U.S. patent application number 10/859737 was filed with the patent office on 2004-10-28 for vegf-related protein.
This patent application is currently assigned to Genentech, Inc.. Invention is credited to Lee, James, Wood, William.
Application Number | 20040213790 10/859737 |
Document ID | / |
Family ID | 21706123 |
Filed Date | 2004-10-28 |
United States Patent
Application |
20040213790 |
Kind Code |
A1 |
Lee, James ; et al. |
October 28, 2004 |
VEGF-related protein
Abstract
A human VEGF-related protein (VRP) has been identified and
isolated that binds to, and stimulates the phosphorylation of, the
receptor tyrosine kinase Flt4. The VRP is postulated to be a third
member of the VEGF protein family. Also provided are antibodies
that bind to VRP and neutralize a biological activity of VRP,
compositions containing the VRP or antibody, methods of use,
chimeric polypeptides, and a signal polypeptide for VRP.
Inventors: |
Lee, James; (San Bruno,
CA) ; Wood, William; (Cupertino, CA) |
Correspondence
Address: |
GENENTECH, INC.
1 DNA WAY
SOUTH SAN FRANCISCO
CA
94080
US
|
Assignee: |
Genentech, Inc.
South San Francisco
CA
|
Family ID: |
21706123 |
Appl. No.: |
10/859737 |
Filed: |
June 2, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10859737 |
Jun 2, 2004 |
|
|
|
10346802 |
Jan 17, 2003 |
|
|
|
10346802 |
Jan 17, 2003 |
|
|
|
09313299 |
May 17, 1999 |
|
|
|
6576608 |
|
|
|
|
09313299 |
May 17, 1999 |
|
|
|
08706054 |
Aug 30, 1996 |
|
|
|
6451764 |
|
|
|
|
60003491 |
Sep 8, 1995 |
|
|
|
Current U.S.
Class: |
424/146.1 ;
514/19.3; 514/7.5; 514/8.1; 530/350; 530/388.26 |
Current CPC
Class: |
A61P 7/00 20180101; A61P
27/06 20180101; C07K 16/22 20130101; A61P 11/00 20180101; C07K
14/52 20130101; A61P 3/10 20180101; A61P 9/10 20180101; A61P 17/00
20180101; A61P 13/12 20180101; A61P 9/14 20180101; A61P 9/00
20180101; A61P 27/02 20180101; C07K 2319/30 20130101; A61P 7/10
20180101; A61P 29/00 20180101; C07K 2319/00 20130101; A61P 17/06
20180101; A61P 35/00 20180101; A61P 5/14 20180101; A61P 35/04
20180101; A61K 38/00 20130101; C07K 14/71 20130101; A61P 19/02
20180101; A61P 43/00 20180101; A61P 17/02 20180101 |
Class at
Publication: |
424/146.1 ;
530/388.26; 514/012; 530/350 |
International
Class: |
A61K 039/395; C07K
016/40 |
Claims
1-22. Canceled
23. A method of blocking or preventing neovascularization in a
mammal, said method comprising: administering to the mammal an
effective amount of a Flt4 ligand antagonist in combination with
second agent, wherein the combined administration blocks or
prevents neovascularization.
24. The method of claim 23, wherein the neovascularization is
associated with a neoplastic disorder.
25. The method of claim 24, wherein the neoplastic disorder is
tumor growth.
26. The method of claim 25, wherein the mammal comprises a
tumor-bearing patient undergoing therapy for tumors, wherein the
patient is receiving no further beneficial effect from the
therapy.
27. The method of claim 23, wherein the mammal is a human.
28. The method of claim 23, further comprising administering a
third therapeutic agent.
29. The method of claim 28, wherein the third therapeutic agent is
antibody to an angiogenic molecule, wherein the antibody inhibits
or neutralizes the angiogenic activity of the molecule.
30. The method of claim 23, wherein the Flt4 ligand antagonist
comprises a VEGF-related protein (VRP) antagonist.
31. The method of claim 30, wherein the VRP antagonist is an
anti-VRP antibody.
32. The method of claim 23, wherein the second agent comprises a
VEGF antagonist.
33. The method of claim 32, wherein the VEGF antagonist is an
anti-VEGF antibody.
34. The method of claim 33, wherein the antibody is A4.6.1.
35. The method of claim 31 or 33, wherein the antibody is a
humanized antibody.
36. The method of claim 23, wherein the Flt4 ligand antagonist
blocks excess activation of a Flt4 receptor.
37. The method of claim 23, wherein the second agent is a PDGF
antagonist.
38. The method of claim 23, wherein the administration is performed
serially.
39. A method of prevent neovascularization associated with tumor
growth, the method comprising: administering to a mammal an
effective amount of at least two agents, which block excessive
activation of a receptor for VRP.
40. The method of claim 39, wherein at least one of the two agents
is an anti-VRP antibody which inhibits activation of a FLT4
receptor.
41. A method of blocking or preventing neovascularization in a
mammal, the method comprising: administering to the mammal an
effective amount of a VRP antagonist, wherein the mammal comprises
a tumor-bearing patient undergoing therapy for tumors, and the
patient is receiving no further beneficial effect from the therapy,
and wherein the administration blocks or prevents
neovascularization.
42. The method of claim 41, wherein the patient is being treated
with a VEGF antagonist.
43. The method of claim 42, wherein the VEGF antagonist comprises
an anti-VEGF antibody.
44. The method of claim 43, wherein the antibody is A4.6.1.
45. The method of claim 43, wherein the antibody is a humanized
antibody.
46. The method of claim 41, further comprising administering
another auxiliary agent.
Description
PRIORITY OF INVENTION
[0001] This application is a divisional of pending U.S. patent
application Ser. No. 09/313,299, filed on May 17, 1999, which is a
divisional application of U.S. patent application Ser. No.
08/706,054, filed on Aug. 30, 1996, now U.S. Pat. No. 6,451,764,
which claims the benefit of U.S. Provisional Application Serial No.
60/003,491, filed on Sep. 8, 1995. All of these applications are
hereby expressly incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention pertains generally to a receptor
protein tyrosine kinase (rPTK) ligand. More particularly, the
invention relates to a novel ligand, designated VEGF-related
protein (VRP) or VH1, which binds to, and stimulates the
phosphorylation of, the Flt4 tyrosine kinase receptor (also known
as the Sal-S 1 receptor) and the isolation and recombinant
production of the same.
[0004] 2. Description of Related Art
[0005] The formation of new blood vessels either from
differentiating endothelial cells during embryonic development
(vasculogenesis) or from pre-existing vessels during adult life
(angiogenesis) is an essential feature of organ development,
reproduction, and wound healing in higher organisms. Folkman and
Shing, J. Biol. Chem., 267: 10931-10934 (1992); Reynolds et al.,
FASEB J., 6: 886-892 (1992); Risau et al., Development, 102:
471-478 (1988). Angiogenesis is also necessary for certain
pathological processes including tumorigenesis (Folkman, Nature
Medicine, 1: 27-31 [1995]) and retinopathy. Miller et al., Am. J.
Pathol., 145: 574-584 (1994). While several growth factors can
stimulate angiogenesis (Klagsbrun and D'Amore, Ann. Rev. Physiol.,
53: 217-239 [1991]; Folkman and Klagsbrun, Science, 235: 442-447
[1987]), vascular endothelial growth factor (VEGF) (Ferrara et al.,
Endo. Rev., 13: 18-32 [1992]) is a potent angiogenic factor that
acts via the endothelial cell-specific receptor tyrosine kinases
fms-like tyrosine kinase (Flt1) (Shibuya et al., Oncogene, 5:
519-524 [1990]; deVries et al., Science, 255: 989-991 [1992]) and
fetal liver kinase (Flk1) (also designated KDR). Quinn et al.,
Proc. Natl. Acad. Sci. USA, 90: 7533-7537 (1993); Millauer et al.,
Cell, 72: 835-846 (1993); Matthews et al., Proc. Natl. Acad. Sci.
USA, 88: 9026-9030 (1991); Terman et al., Biochem. Biophys. Res.
Commun., 187: 1579-1586 (1992); Terman et al., Oncogene, 6:
1677-1683 (1991); Oelrichs et al., Oncogene, 8: 11-18 (1993). These
two VEGF receptors and a third orphan receptor, Flt4 (Pajusola et
al., Cancer Res., 52: 5738-5743 [1992]; Galland et al., Oncogene,
8: 1233-1240 [1993]; Finnerty et al., Oncogene, 8: 2293-2298
[1993]) constitute a subfamily of class III receptor tyrosine
kinases that contain seven extracellular immunoglobulin-like
domains and a split intracellular tyrosine kinase domain. Mustonen
and Alitalo, J. Cell. Biol., 129: 895-898 (1995). See also WO
94/10202 published 11 May 1994 and PCT/US93/00586 filed 22 Jan.
1993 (Avraham et al.). These three receptors have 31-36% amino acid
identity in their extracellular ligand-binding domains.
[0006] Mice deficient in Flt1 (Fong et al., Nature, 376: 66-70
[1995]) or Flk1 (Shalaby et al., Nature, 376: 62-66 [1995])
(generated by gene targeting in embryonic stem cells) have severe
defects in vasculogenesis and die in utero at embryonic day 8-9.
The phenotype of the receptor-deficient mice differs considerably,
however. Mice lacking Flt1 have a disorganized vascular endothelium
that extends to the major vessels as well as to the
microvasculature, while endothelial cell differentiation appears to
be normal. Fong et al., supra. Mice lacking Flk1 have a major
defect in the development of mature endothelial cells as well as a
severe reduction in hematopoietic cell progenitors. Shalaby et al,
supra. Thus, VEGF may act on endothelial cells at more than one
stage of vasculogenesis.
[0007] Flt4 is also specifically expressed in endothelial cells; it
is first observed in day 8.5 mouse embryos in endothelial cell
precursors. Kaipainen et al., Proc. Natl. Acad. Sci. USA, 92:
3566-3570 (1995); Kaipainen et al., J. Exp. Med., 178: 2077-2088
(1993). See also Hatva et al., Am J. Pathol., 146: 368-378 (1995).
As development proceeds, Flt4 expression becomes confined to the
venous and lymphatic endothelium and is finally restricted to the
lymphatic vessels. Consistent with this finding, adult human
tissues show Flt4 expression in lymphatic endothelia while there is
a lack of expression in arteries, veins, and capillaries. Kaipainen
et al., Proc. Natl. Acad. Sci. USA, supra. Clones encoding human
and mouse Flt4 have been isolated either by PCR with primers from
conserved tyrosine kinase regions (Finnerty et al., supra;
PCT/US93/00586, supra; Aprelikova et al., Cancer Res., 52: 746-748
[1992]) or by low-stringency hybridization with a Flk2 probe.
Galland et al., Genomics, 13: 475-478 (1992). Alternative splicing
of the Flt4 mRNA produces two variants of the protein differing by
65 amino acids at the C-terminus. Pajusola et al., Oncogene, 8:
2931-2937 (1993). These variants migrate as bands of 170-190 kDa
that are partially cleaved proteolytically in the extracellular
domain to produce a form of about 125 kDa. Pajusola et al.,
Oncogene, 8, supra; Pajusola et al., Oncogene, 9: 3545-3555 (1994).
Expression of the longer spliced form of Flt4 as a chimera with the
extracellular domain of the CSF-1 receptor shows that the Flt4
intracellular domain can signal a ligand-dependent growth response
in rodent fibroblasts. Pajusola et al., Oncogene, 9, supra; Borg et
al., Oncogene, 10: 973-984 (1995). Flt4 has been localized to human
chromosome 5q34-q35 (Aprelikova et al, supra; Galland et al.,
Genomics, supra); Flt1 and Flk1 are located at 13q12 (Imbert et
al., Cytogenet. Cell Genet., 67: 175-177 [1994]) and 4q12. Sait et
al., Cytogenet. Cell Genet., 70: 145-146 (1995); Spritz et al.,
Genomics, 22: 431436 (1994).
[0008] VEGF is a homodimeric, cysteine-rich protein that can occur
in at least four forms due to alternative splicing of its mRNA.
Ferrara et al, supra. While VEGF is a high-affinity ligand for Flt1
and Flk1, it does not bind or activate Flt4. Pajusola et al.,
Oncogene, 9, supra. The only other closely related member of the
VEGF family is placental growth factor (PlGF), which has 47% amino
acid identity with VEGF. Maglione et al., Proc. Natl. Acad. Sci.
USA, 88: 9267-9271 (1991). P1GF also occurs in two alternatively
spliced forms which differ in the presence or absence of a basic
heparin binding domain of 21 amino acids. Maglione et al.,
Oncogene, 8: 925-931 (1993); Hauser and Weich, Growth Factors, 9:
259-268 (1993). PlGF binds to Flt1 but not to Flk1 (Park et al., J.
Biol. Chem., 269: 25646-25654 [1994]); it is believed that its
binding to Flt4 has not been determined. PlGF fails to duplicate
the capillary endothelial cell mitogenesis or vascular permeability
activities of VEGF, suggesting that these activities are mediated
by the Flk1 receptor. Park et al., supra.
[0009] Molecules that modulate the Flk1 receptor or neutralize
activation of a VEGF receptor are disclosed in the patent
literature. For example, WO 95/21613 published 17 Aug. 1995
discloses compounds that modulate KDR/Flk1 receptor signal
transduction so as to regulate and/or modulate vasculogenesis and
angiogenesis and disclose using Flk1 to evaluate and screen for
drugs and analogs of VEGF involved in Flk1 modulation by either
agonist or antagonist activities; WO 95/21865 published 17 Aug.
1995 discloses molecules immunointeractive with animal
neuroepithelial kinase (NYK)/Flk1, which molecules can be used to
provide agents for treatment, prophylaxis, and diagnosis of an
angiogenic-dependent phenotype; and WO 95/21868 published 17 Aug.
1995 discloses monoclonal antibodies that specifically bind to an
extracellular domain of a VEGF receptor and neutralize activation
of the receptor.
SUMMARY OF THE INVENTION
[0010] cDNA clones have now been identified that encode a novel
protein, designated VRP, which binds to and stimulates the
phosphorylation of the receptor tyrosine kinase Flt4. VRP is
related in amino acid sequence to VEGF, but does not interact
appreciably with the VEGF receptors, Flt1 and Ftk1.
[0011] In one aspect, the invention provides isolated biologically
active human VRP containing at least 265 amino acids. In another
aspect, the invention supplies isolated biologically active human
VEGF-related protein (VRP) comprising an amino acid sequence
comprising at least residues +1 through 29, inclusive, of FIG. 1.
In further aspect, the invention supplies isolated biologically
active human VRP comprising an amino acid sequence shown as
residues -20 through 399, inclusive, or residues 1 through 399,
inclusive, of FIG. 1.
[0012] The invention also pertains to chimeras comprising the VRP
fused to another polypeptide. For example, the invention provides a
chimeric polypeptide comprising the VRP fused to a tag polypeptide
sequence. An example of such a chimera is epitope-tagged VRP.
[0013] In another aspect, the invention provides a composition
comprising biologically active VRP and a pharmaceutically
acceptable carrier. In a more specific embodiment, the invention
provides a pharmaceutical composition useful for promotion of
vascular or lymph endothelial cell growth comprising a
therapeutically effective amount of the VRP in a pharmaceutically
acceptable carrier. In another aspect, this composition further
comprises another cell growth factor such as VEGF and/or PDGF.
[0014] In a further aspect, the invention provides a method of
treating vascular tissue and promoting angiogenesis in a mammal
comprising administering to the mammal an effective amount of the
composition comprising VRP. In another embodiment, the invention
provides a method for treating trauma affecting the vascular
endothelium comprising administering to a mammal suffering from
said trauma an effective amount of the composition containing the
VRP. The trauma is, for example, diabetic ulcers or a wound of the
blood vessels or heart. In another embodiment, the invention
provides a method for treating a dysfunctional state characterized
by lack of activation or lack of inhibition of a receptor for VRP
in a mammal comprising administering to the mammal an effective
amount of the composition containing the VRP.
[0015] The invention also provides a method which involves
contacting the Flt4 receptor with the VRP to cause phosphorylation
of the kinase domain thereof. For example, the invention provides a
method for stimulating the phosphorylation of a tyrosine kinase
domain of a Flt4 receptor comprising contacting an extracellular
domain of the Flt4 receptor with the VRP.
[0016] The invention also provides a monoclonal antibody which
binds to the VRP and preferably also neutralizes a biological
activity of the protein, one biological activity being
characterized as promoting neovascularization or vascular
permeability or vascular endothelial cell growth in a mammal.
Alternatively or conjunctively, the invention provides a monoclonal
antibody which binds to the N-terminal portion from residues -20
through 137, inclusive, or from residues +1 through 137, inclusive,
of the amino acid sequence shown in FIG. 1. The antibody can be
used, for example, to detect the presence of the VRP in a
biological sample suspected of having the protein, or to treat
patients. The invention contemplates a pharmaceutical composition
comprising such antibody and a pharmaceutically acceptable carrier,
as well as a method of treating diseases or disorders characterized
by undesirable excessive neovascularization or vascular
permeability in a mammal comprising administering to said mammal an
effective amount of one of the antibodies described above. Further
included by the invention is a method for treating a dysfunctional
state characterized by excessive activation or inhibition of a
receptor for VRP in a mammal comprising administering to the mammal
an effective amount of one of the antibodies described above.
[0017] In addition, the invention contemplates a peptide consisting
of an amino acid sequence shown as residues -20 through -1,
inclusive, of FIG. 1.
[0018] In a further embodiment, the invention provides an isolated
nucleic acid molecule encoding VRP or a VRP chimera. In one aspect,
the nucleic acid molecule is RNA or DNA that encodes a biologically
active VRP or is complementary to nucleic acid sequence encoding
such VRP, and remains stably bound to it under stringent
conditions. The nucleic acid molecule optionally includes the
regions of the nucleic acid sequences of FIG. 1 which encode signal
sequences. In one embodiment, the nucleic acid sequence is selected
from:
[0019] (a) the coding region of the nucleic acid sequence of FIG. 1
that codes for the preprotein from residue -20 to residue 399 or
that codes for the mature protein from residue 1 to residue 399
(i.e., nucleotides 372 through 1628, inclusive, or nucleotides 432
through 1628, inclusive, of the nucleic acid sequence shown in FIG.
1 as SEQ ID NO: 1); or
[0020] (b) a sequence corresponding to the sequence of (a) within
the scope of degeneracy of the genetic code. In another aspect, the
nucleic acid molecule can be provided in a replicable vector
comprising the nucleic acid molecule operably linked to control
sequences recognized by a host cell transfected or transformed with
the vector. The invention further provides a host cell comprising
the vector or the nucleic acid molecule. A method of producing VRP
is also provided which comprises culturing a host cell comprising
the nucleic acid molecule and recovering the protein from the host
cell culture.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIGS. 1A-1D depict the nucleotide coding sequence (SEQ ID
NO: 1), nucleotide complementary sequence (SEQ ID NO: 2), and
deduced amino acid sequence (SEQ ID NO: 3) of the human VRP
described herein.
[0022] FIG. 2 depicts binding of Flt4/IgG and of Rse/IgG (an
unrelated receptor fusion protein) to the human glioma cell line
G61, which binding was evaluated by FACS analysis.
[0023] FIGS. 3A and 3B respectively depict a map of cDNA clones
encoding human VRP and an alignment of the protein sequence VRP
(SEQ ID NO: 3) with that of VEGF.sub.121 (SEQ ID NO: 4) and
PlGF.sub.131 (SEQ ID NO: 5). FIG. 3A shows the extent of four VRP
cDNA clones; dashed lines indicate the missing portions of VH1.1
and VH1.3. Arrows indicate restriction enzyme sites; the shaded box
indicates the putative secretion signal sequence; the open box
indicates the mature protein; Y-type designations within the open
box indicate the potential N-linked glycosylation sites; and
vertical lines indicate the cysteine residues. A diagram of
VEGF.sub.121 is shown for comparison. The hydropathy plot (Kyle and
Doolittle, J. Mol. Biol., 157: 105-132 [1982]) is for VRP. In FIG.
3B, overlining indicates the region encoded by an expressed
sequence tag (EST) (sequence of a portion of a cDNA clone) from
GenBank designated HSC1WF111.
[0024] FIG. 4 depicts a map of the cDNA clone for full-length human
VRP herein versus eleven known EST's. The eleven EST partial amino
acid sequence fragments are H07991 and H07899 (5' and 3' ends of
the same cloned fragment, respectively), H05134 and H05177 (3' and
5' ends of the same cloned fragment, respectively), HSC1WF112 and
HSC1WF111 (3' and 5' ends of the same cloned fragment,
respectively), T81481 and T81690 (3' and 5' ends of the same cloned
fragment, respectively), R77495 (a 3' end of a cloned fragment),
and T84377 and T89295 (5' and 3' ends of the same cloned fragment,
respectively).
[0025] FIG. 5 depicts binding of .sup.125I-Flt4/IgG to purified
VRP. The binding was performed in the absence (-) or presence (+)
of 100 nM receptor IgG fusion protein (FIG. 5A) or with increasing
concentrations of Flt4/IgG (FIG. 5B).
[0026] FIG. 6 shows a graph of the cell count of human lung
microvascular endothelial cells as a function of the concentration
of VEGF or VRP in the cell culture medium to assess and compare
mitogenic activity.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] I. Definitions
[0028] In describing the present invention, the following terms
will be employed, and are intended to be defined as indicated
below.
[0029] "Human VRP" is defined herein to be a polypeptide sequence
containing at least residues -20 to 399, inclusive, or residues +1
to 399, inclusive, of the amino acid sequence shown in FIG. 1,
including residues -5 to 399, inclusive, and residues -4 to 399,
inclusive, of the amino acid sequence shown in FIG. 1, as well as
biologically active deletional, insertional, or substitutional
variants of the above sequences having at least 265 amino acids
and/or having at least residues +1 through 29, inclusive, of FIG.
1. In a preferred embodiment, the protein sequence has at least
residues +1 through 137, inclusive, of FIG. 1, more preferably at
least residues -20 through 29, inclusive, of FIG. 1, and most
preferably at least residues -20 through 137, inclusive, of FIG. 1.
In another preferred embodiment, the biologically active variants
have a length of 265 to about 450 amino acid residues, more
preferably about 300-450, even more preferably about 350-450, and
most preferably about 399-419 amino acid residues. Another
preferred set of variants are variants that are insertional or
substitutional variants, or deletional variants where the deletion
is in the signal sequence and/or is not in the N-terminal region of
the molecule (i.e., residues 1-29, preferably residues 1-137). The
definition of VRP excludes all known EST sequences, such as, e.g.,
H07991, H05134, H05177, HSC1WF112, HSC1WF111, T81481, R77495,
H07899, T84377, T81690, and T89295, as well as all forms of VEGF
and PlGF.
[0030] "Biologically active" for the purposes herein means having
the ability to bind to, and stimulate the phosphorylation of, the
Flt4 receptor. Generally, the protein will bind to the
extracellular domain of the Flt4 receptor and thereby activate or
inhibit the intracellular tyrosine kinase domain thereof.
Consequently, binding of the protein to the receptor may result in
enhancement or inhibition of proliferation and/or differentiation
and/or activation of cells having the Flt4 receptor for the VRP in
vivo or in vitro. Binding of the protein to the Flt4 receptor can
be determined using conventional techniques, including competitive
binding methods, such as RIAs, ELISAs, and other competitive
binding assays. Ligand/receptor complexes can be identified using
such separation methods as filtration, centrifugation, flow
cytometry (see, e.g., Lyman et al., Cell, 75:1157-1167 [1993];
Urdal et al., J. Biol. Chem., 263:2870-2877 [1988]; and Gearing et
al., EMBO J., 8:3667-3676 [1989]), and the like. Results from
binding studies can be analyzed using any conventional graphical
representation of the binding data, such as Scatchard analysis
(Scatchard, Ann. NY Acad. Sci.,51:660-672 [1949]; Goodwin et al.,
Cell, 73:447-456 [1993]), and the like. Since the VRP induces
phosphorylation of the Flt4 receptor, conventional tyrosine
phosphorylation assays, such as the assay described in Example 5
herein, can also be used as an indication of the formation of a
Flt4 receptor/VRP complex.
[0031] The term "epitope tagged" when used herein refers to a
chimeric polypeptide comprising the entire VRP, or a portion
thereof, fused to a "tag polypeptide". The tag polypeptide has
enough residues to provide an epitope against which an antibody
thereagainst can be made, yet is short enough such that it does not
interfere with activity of the VRP. The tag polypeptide preferably
also is fairly unique so that the antibody thereagainst does not
substantially cross-react with other epitopes. Suitable tag
polypeptides generally have at least six amino acid residues and
usually between about 8-50 amino acid residues (preferably between
about 9-30 residues).
[0032] "Isolated," when used to describe the various proteins
disclosed herein, means protein that has been identified and
separated and/or recovered from a component of its natural
environment. Contaminant components of its natural environment are
materials that would interfere with diagnostic or therapeutic uses
for the protein, and may include enzymes, hormones, and other
proteinaceous or non-proteinaceous solutes. In preferred
embodiments, the protein will be purified (1) to a degree
sufficient to obtain at least 15 residues of N-terminal or internal
amino acid sequence by use of a spinning cup sequenator, or (2) to
homogeneity by SDS-PAGE under non-reducing or reducing conditions
using Coomassie blue or, preferably, silver stain. Isolated protein
includes protein in situ within recombinant cells, since at least
one component of the VRP natural environment will not be present.
Ordinarily, however, isolated protein will be prepared by at least
one purification step.
[0033] "Essentially pure" protein means a composition comprising at
least about 90% by weight of the protein, based on total weight of
the composition, preferably at least about 95% by weight.
"Essentially homogeneous" protein means a composition comprising at
least about 99% by weight of protein, based on total weight of the
composition.
[0034] An "isolated" VRP nucleic acid molecule is a nucleic acid
molecule that is identified and separated from at least one
contaminant nucleic acid molecule with which it is ordinarily
associated in the natural source of the VRP nucleic acid. An
isolated VRP nucleic acid molecule is other than in the form or
setting in which it is found in nature. Isolated VRP nucleic acid
molecules therefore are distinguished from the VRP nucleic acid
molecule as it exists in natural cells. However, an isolated VRP
nucleic acid molecule includes VRP nucleic acid molecules contained
in cells that ordinarily express VRP where, for example, the
nucleic acid molecule is in a chromosomal location different from
that of natural cells.
[0035] The isolated VRP polypeptide, VRP nucleic acid, or VRP
antibody may be labeled for diagnostic and probe purposes, using a
label as described and defined further below in the discussion on
uses of VRP antibodies.
[0036] The expression "control sequences" refers to DNA sequences
necessary for the expression of an operably linked coding sequence
in a particular host organism. The control sequences that are
suitable for prokaryotes, for example, include a promoter,
optionally an operator sequence, a ribosome binding site, and
possibly, other as yet poorly understood sequences. Eukaryotic
cells are known to utilize promoters, polyadenylation signals, and
enhancers.
[0037] Nucleic acid is "operably linked" when it is placed into a
functional relationship with another nucleic acid sequence. For
example, DNA for a presequence or secretory leader is operably
linked to DNA for a polypeptide if it is expressed as a preprotein
that participates in the secretion of the polypeptide; a promoter
or enhancer is operably linked to a coding sequence if it affects
the transcription of the sequence; or a ribosome binding site is
operably linked to a coding sequence if it is positioned so as to
facilitate translation. Generally, "operably linked" means that the
DNA sequences being linked are contiguous, and, in the case of a
secretory leader, contiguous and in reading phase. However,
enhancers do not have to be contiguous. Linking is accomplished by
ligation at convenient restriction sites. If such sites do not
exist, the synthetic oligonucleotide adaptors or linkers are used
in accordance with conventional practice.
[0038] The term "antibody" is used in the broadest sense and
specifically covers single anti-VRP monoclonal antibodies
(including agonist and antagonist antibodies) and anti-VRP antibody
compositions with polyepitopic specificity.
[0039] The term "monoclonal antibody" as used herein refers to an
antibody obtained from a population of substantially homogeneous
antibodies, i.e., the individual antibodies comprising the
population are identical except for possible naturally-occurring
mutations that may be present in minor amounts. Monoclonal
antibodies are highly specific, being directed against a single
antigenic site. Furthermore, in contrast to conventional
(polyclonal) antibody preparations which typically include
different antibodies directed against different determinants
(epitopes), each monoclonal antibody is directed against a single
determinant on the antigen.
[0040] The monoclonal antibodies herein include hybrid and
recombinant antibodies produced by splicing a variable (including
hypervariable) domain of an anti-VRP antibody with a constant
domain (e.g. "humanized" antibodies), or a light chain with a heavy
chain, or a chain from one species with a chain from another
species, or fusions with heterologous proteins, regardless of
species of origin or immunoglobulin class or subclass designation,
as well as antibody fragments (e.g., Fab, F(ab').sub.2, and Fv), so
long as they exhibit the desired biological activity. See, e.g.
U.S. Pat. No. 4,816,567 and Mage and Lamoyi, in Monoclonal Antibody
Production Techniques and Applications, pp.79-97 (Marcel Dekker,
Inc.: New York, 1987).
[0041] Thus, the modifier "monoclonal" indicates the character of
the antibody as being obtained from a substantially homogeneous
population of antibodies, and is not to be construed as requiring
production of the antibody by any particular method. For example,
the monoclonal antibodies to be used in accordance with the present
invention may be made by the hybridoma method first described by
Kohler and Milstein, Nature, 256:495 (1975), or may be made by
recombinant DNA methods. U.S. Pat. No. 4,816,567. The "monoclonal
antibodies" may also be isolated from phage libraries generated
using the techniques described in McCafferty et al., Nature,
348:552-554 (1990), for example.
[0042] "Humanized" forms of non-human (e.g. murine) antibodies are
specific chimeric immunoglobulins, immunoglobulin chains, or
fragments thereof (such as Fv, Fab, Fab', F(ab').sub.2 or other
antigen-binding subsequences of antibodies) which contain minimal
sequence derived from non-human immunoglobulin. For the most part,
humanized antibodies are human immunoglobulins (recipient antibody)
in which residues from a complementary determining region (CDR) of
the recipient are replaced by residues from a CDR of a non-human
species (donor antibody) such as mouse, rat, or rabbit having the
desired specificity, affinity, and capacity. In some instances, Fv
framework region (FR) residues of the human immunoglobulin are
replaced by corresponding non-human residues. Furthermore, the
humanized antibody may comprise residues which are found neither in
the recipient antibody nor in the imported CDR or framework
sequences. These modifications are made to further refine and
optimize antibody performance. In general, the humanized antibody
will comprise substantially all of at least one, and typically two,
variable domains, in which all or substantially all of the CDR
regions correspond to those of a non-human immunoglobulin and all
or substantially all of the FR regions are those of a human
immunoglobulin consensus sequence. The humanized antibody optimally
also will comprise at least a portion of an immunoglobulin constant
region (Fc), typically that of a human immunoglobulin.
[0043] As used herein, "vascular endothelial cell growth factor,"
or "VEGF," refers to a mammalian growth factor derived originally
from bovine pituitary follicular cells having the amino acid
sequence of FIG. 2 of WO 90/13649, and has the human amino acid
sequence of FIG. 10 of WO 90/13649. See also U.S. Pat. No.
5,194,596, which discloses bovine VEGF of 120 amino acids and human
VEGF of 121 amino acids. The biological activity of native VEGF is
capable of promoting selective growth of vascular endothelial cells
but not of bovine corneal endothelial cells, lens epithelial cells,
adrenal cortex cells, BHK-21 fibroblasts, or keratinocytes.
[0044] The expression "trauma affecting the vascular endothelium"
refers to trauma, such as injuries, to the blood vessels or heart,
including the vascular network of organs, to which an animal or
human, preferably a mammal, and most preferably a human, is
subjected. Examples of such trauma include wounds, incisions, and
ulcers, most preferably diabetic ulcers and wounds or lacerations
of the blood vessels or heart. Trauma includes conditions caused by
internal events as well as those that are imposed by an extrinsic
agent such as a pathogen, which can be improved by promotion of
vascular endothelial cell growth. It also refers to the treatment
of wounds in which neovascularization or re-endothelialization is
required for healing.
[0045] "Promotion of vascular or lymph endothelial cell growth"
refers to inducing or increasing the growth of vascular or lymph
endothelial cells, including human lung microvascular endothelial
cells.
[0046] "Disorders related to vasculogenesis and angiogenesis"
include cancer, diabetes, hemangioma, and Kaposi's sarcoma.
[0047] "Diseases or disorders characterized by undesirable
excessive neovascularization or vascular permeability" refer to
diseases or disorders that include, by way of example, excessive
neovascularization, tumors, and especially solid malignant tumors,
rheumatoid arthritis, psoriasis, atherosclerosis, diabetic and
other retinopathies, retrolental fibroplasia, age-related macular
degeneration, neovascular glaucoma, hemangiomas, thyroid
hyperplasias (including Grave's disease), corneal and other tissue
transplantation, and chronic inflammation. Examples of diseases or
disorders characterized by undesirable excessive vascular
permeability include edema associated with brain tumors, ascites
associated with malignancies, Meigs' syndrome, lung inflammation,
nephrotic syndrome, pericardial effusion (such as that associated
with pericarditis), and pleural effusion.
[0048] "Dysfunctional states characterized by excessive activation
or inhibition of a receptor for VRP" (such receptor including Flt4)
refer to disorders or diseases that would be beneficially treated
by providing to a mammal having such a pathological condition an
antagonist to VRP, such as a chimera of Flt4 or its extracellular
domain (e.g., an IgG fusion with Flt4) or an antibody to VRP.
[0049] "Dysfunctional states characterized by lack of activation or
lack of inhibition of a receptor for VRP" (such receptor including
Flt4) refer to disorders or diseases that would be beneficially
treated by providing VRP or a VRP receptor agonist to a mammal with
such a pathological condition.
[0050] "Treatment" refers to both therapeutic treatment and
prophylactic or preventative measures. Those in need of treatment
include those already with the disorder as well as those prone to
have the disorder or those in which the disorder is to be
prevented.
[0051] "Mammal" for purposes of treatment refers to any animal
classified as a mammal, including humans, domestic and farm
animals, and zoo, sports, or pet animals, such as dogs, horses,
cats, cows, etc. Preferably, the mammal herein is human.
[0052] "Effective amount" or "therapeutically effective amount" of
the VRP, VRP composition, antibody, or antibody composition is an
amount that is effective either to prevent, lessen the worsening
of, alleviate, or cure the treated condition. For example, an
effective amount of VRP includes that amount which is sufficient to
enhance the growth of vascular endothelium in vivo or to treat
trauma, and an "effective amount" of VRP antibody includes that
amount which is sufficient to reduce excess neovascularization and
angiogenesis.
[0053] II. Modes for Carrying Out the Invention
[0054] The present invention is based on the discovery of a novel
VRP which binds to, and stimulates the phosphorylation of, the Flt4
receptor.
[0055] Three approaches were undertaken to identify protein that
would bind and stimulate the phosphorylation of the Flt4 receptor.
First, the full-length receptor was stably expressed in 293 cells
to establish a receptor tyrosine kinase phosphorylation assay of
Flt4 activation. This assay was used to screen about 400 cell
supernatants and tissue extracts, without positive results.
[0056] Second, the extracellular domain of the receptor was
expressed as a fusion protein with an immunoglobulin Fc domain. By
using this fusion protein (Flt4/IgG) to screen cell lines for
membrane-bound ligands by FACS analysis, one positive cell line was
identified. The human glioma line, G61, gave about a 10-fold shift
in peak fluorescence intensity that was specific for Flt4/IgG (FIG.
2). Attempts to expression clone this putative membrane-bound
ligand by the transfection of pools of cDNA clones into COS cells
followed by screening with labeled Flt4/IgG gave no positives from
640 pools of 1000-5000 clones each. Flt4/IgG was also used to
generate polyclonal antisera and monoclonal antibodies that had
agonistic activity and that were used to develop the Flt4 tyrosine
phosphorylation assay as described in Example 5 below.
[0057] Third, candidate ligand proteins were tested for their
ability to bind to Flt4/IgG or to activate the Flt4 phosphorylation
assay. Labeled VEGF failed to bind to Flt4/IgG, although the
expected binding of VEGF to Flt1/IgG or Flk1/IgG was routinely
detected. The failure of VEGF to bind or stimulate the
phosphorylation of Flt4 has been reported by Pajusola et al.,
Oncogene, 9, supra. An additional candidate ligand protein was
found by use of cloning techniques, details of which are provided
in Example 3 below. The human VRP cDNA sequence is depicted in
FIGS. 1A-1D. The predicted molecular weight of the protein is 44.8
kDa.
[0058] A description follows as to how the biologically active
human VRP may be prepared.
[0059] 1. Preparation of VRP
[0060] Most of the discussion below pertains to production of VRP
by culturing cells transformed with a vector containing VRP nucleic
acid and recovering the polypeptide from the cell culture. It is
further envisioned that the VRP of this invention may be produced
by homologous recombination, as provided for in WO 91/06667,
published 16 May 1991.
[0061] Briefly, this method involves transforming primary human
cells containing a human VRP-encoding gene with a construct (i.e.,
vector) comprising an amplifiable gene [such as dihydrofolate
reductase (DHFR) or others discussed below] and at least one
flanking region of a length of at least about 150 bp that is
homologous with a DNA sequence at the locus of the coding region of
the VRP gene to provide amplification of the VRP gene. The
amplifiable gene must be at a site that does not interfere with
expression of the VRP gene. The transformation is conducted such
that the construct becomes homologously integrated into the genome
of the primary cells to define an amplifiable region.
[0062] Primary cells comprising the construct are then selected for
by means of the amplifiable gene or other marker present in the
construct. The presence of the marker gene establishes the presence
and integration of the construct into the host genome. No further
selection of the primary cells need be made, since selection will
be made in the second host. If desired, the occurrence of the
homologous recombination event can be determined by employing PCR
and either sequencing the resulting amplified DNA sequences or
determining the appropriate length of the PCR fragment when DNA
from correct homologous integrants is present and expanding only
those cells containing such fragments. Also if desired, the
selected cells may be amplified at this point by stressing the
cells with the appropriate amplifying agent (such as methotrexate
if the amplifiable gene is DHFR), so that multiple copies of the
target gene are obtained. Preferably, however, the amplification
step is not conducted until after the second transformation
described below.
[0063] After the selection step, DNA portions of the genome,
sufficiently large to include the entire amplifiable region, are
isolated from the selected primary cells. Secondary mammalian
expression host cells are then transformed with these genomic DNA
portions and cloned, and clones are selected that contain the
amplifiable region. The amplifiable region is then amplified by
means of an amplifying agent if not already amplified in the
primary cells. Finally, the secondary expression host cells now
comprising multiple copies of the amplifiable region containing VRP
are grown so as to express the gene and produce the protein.
[0064] A. Isolation of DNA Encoding VRP
[0065] The DNA encoding VRP may be obtained from any cDNA library
prepared from tissue believed to possess the VRP mRNA and to
express it at a detectable level. Accordingly, human VRP DNA can be
conveniently obtained from a cDNA library prepared from human brain
tissue, e.g., a glial cell line. The VRP-encoding gene may also be
obtained from a genomic library or by oligonucleotide
synthesis.
[0066] Libraries are screened with probes (such as antibodies to
the VRP or oligonucleotides of about 20-80 bases) designed to
identify the gene of interest or the protein encoded by it.
Screening the cDNA or genomic library with the selected probe may
be conducted using standard procedures as described in chapters
10-12 of Sambrook et al., Molecular Cloning: A Laboratory Manual
(New York: Cold Spring Harbor Laboratory Press, 1989). An
alternative means to isolate the gene encoding VRP is to use PCR
methodology as described in section 14 of Sambrook et al.,
supra.
[0067] A preferred method of practicing this invention is to use
carefully selected oligonucleotide sequences to screen cDNA
libraries from various human tissues, preferably brain cell lines.
The oligonucleotide sequences selected as probes should be of
sufficient length and sufficiently unambiguous that false positives
are minimized.
[0068] The oligonucleotide must be labeled such that it can be
detected upon hybridization to DNA in the library being screened.
The preferred method of labeling is to use .sup.32P-labeled ATP
with polynucleotide kinase, as is well known in the art, to
radiolabel the oligonucleotide. However, other methods may be used
to label the oligonucleotide, including, but not limited to,
biotinylation or enzyme labeling.
[0069] In some preferred embodiments, the nucleic acid sequence
includes the native VRP signal sequence. Nucleic acid having all
the protein coding sequence is obtained by screening selected cDNA
or genomic libraries using the deduced amino acid sequence
disclosed herein for the first time, and, if necessary, using
conventional primer extension procedures as described in section
7.79 of Sambrook et al., supra, to detect precursors and processing
intermediates of mRNA that may not have been reverse-transcribed
into cDNA.
[0070] Amino acid sequence variants of VRP are prepared by
introducing appropriate nucleotide changes into the VRP DNA, or by
synthesis of the desired VRP polypeptide. Such variants represent
insertions, substitutions, and/or deletions of, residues within or
at one or both of the ends of the amino acid sequence shown for the
VRP in FIG. 1. Preferably, these variants represent insertions
and/or substitutions within or at one or both ends of the mature
sequence, and/or insertions, substitutions and/or deletions within
or at one or both of the ends of the signal sequence for VRP shown
in FIG. 1. Any combination of insertion, substitution, and/or
deletion is made to arrive at the final construct, provided that
the final construct possesses the desired biological activity as
defined herein. The 7amino acid changes also may alter
post-translational processes of the VRP, such as changing the
number or position of glycosylation sites, altering the membrane
anchoring characteristics, and/or altering the intracellular
location of the VRP by inserting, deleting, or otherwise affecting
the leader sequence of the VRP.
[0071] Variations in the native sequence as described above can be
made using any of the techniques and guidelines for conservative
and non-conservative mutations set forth in U.S. Pat. No.
5,364,934. These include oligonucleotide-mediated (site-directed)
mutagenesis, alanine scanning, and PCR mutagenesis. See also, for
example, Table I therein and the discussion surrounding this table
for guidance on selecting amino acids to change, add, or
delete.
[0072] B. Insertion of Nucleic Acid into Replicable Vector
[0073] The nucleic acid (e.g., cDNA or genomic DNA) encoding native
or variant VRP is inserted into a replicable vector for further
cloning (amplification of the DNA) or for expression. Many vectors
are available. The vector components generally include, but are not
limited to, one or more of the following: a signal sequence, an
origin of replication, one or more marker genes, an enhancer
element, a promoter, and a transcription termination sequence.
[0074] (i) Signal Sequence Component
[0075] The VRPs of this invention may be produced recombinantly not
only directly, but also as a fusion polypeptide with a heterologous
polypeptide, which is preferably a signal sequence or other
polypeptide having a specific cleavage site at the N-terminus of
the mature protein or polypeptide. In general, the signal sequence
may be a component of the vector, or it may be a part of the VRP
DNA that is inserted into the vector. The heterologous signal
sequence selected preferably is one that is recognized and
processed (i.e., cleaved by a signal peptidase) by the host cell.
For prokaryotic host cells that do not recognize and process the
native VRP signal sequence, the signal sequence is substituted by a
prokaryotic signal sequence selected, for example, from the group
of the alkaline phosphatase, penicillinase, 1pp, or heat-stable
enterotoxin II leaders. For yeast secretion the native signal
sequence may be substituted by, e.g., the yeast invertase leader,
alpha factor leader (including Saccharomyces and Kluyveromyces
.alpha.-factor leaders, the latter described in U.S. Pat. No.
5,010,182 issued 23 Apr. 1991), or acid phosphatase leader, the C.
albicans glucoamylase leader (EP 362,179 published 4 Apr. 1990), or
the signal described in WO 90/13646 published 15 Nov. 1990. In
mammalian cell expression the native signal sequence (e.g., the VRP
presequence that normally directs secretion of VRP from human cells
in vivo) is satisfactory, although other mammalian signal sequences
may be suitable, such as signal sequences from other animal VRPs,
and signal sequences from secreted polypeptides of the same or
related species, as well as viral secretory leaders, for example,
the herpes simplex gD signal.
[0076] The DNA for such precursor region is ligated in reading
frame to DNA encoding the mature VRP.
[0077] (ii) Origin of Replication Component
[0078] Both expression and cloning vectors contain a nucleic acid
sequence that enables the vector to replicate in one or more
selected host cells. Generally, in cloning vectors this sequence is
one that enables the vector to replicate independently of the host
chromosomal DNA, and includes origins of replication or
autonomously replicating sequences. Such sequences are well known
for a variety of bacteria, yeast, and viruses. The origin of
replication from the plasmid pBR322 is suitable for most
Gram-negative bacteria, the 2.mu. plasmid origin is suitable for
yeast, and various viral origins (SV40, polyoma, adenovirus, VSV or
BPV) are useful for cloning vectors in mammalian cells. Generally,
the origin of replication component is not needed for mammalian
expression vectors (the SV40 origin may typically be used only
because it contains the early promoter).
[0079] Most expression vectors are "shuttle" vectors, i.e., they
are capable of replication in at least one class of organisms but
can be transfected into another organism for expression. For
example, a vector is cloned in E. coli and then the same vector is
transfected into yeast or mammalian cells for expression even
though it is not capable of replicating independently of the host
cell chromosome.
[0080] DNA may also be amplified by insertion into the host genome.
This is readily accomplished using Bacillus species as hosts, for
example, by including in the vector a DNA sequence that is
complementary to a sequence found in Bacillus genomic DNA.
Transfection of Bacillus with this vector results in homologous
recombination with the genome and insertion of VRP DNA. However,
the recovery of genomic DNA encoding VRP is more complex than that
of an exogenously replicated vector because restriction enzyme
digestion is required to excise the VRP DNA.
[0081] (iii) Selection Gene Component
[0082] Expression and cloning vectors should contain a selection
gene, also termed a selectable marker. This gene encodes a protein
necessary for the survival or growth of transformed host cells
grown in a selective culture medium. Host cells not transformed
with the vector containing the selection gene will not survive in
the culture medium. Typical selection genes encode proteins that
(a) confer resistance to antibiotics or other toxins, e.g.,
ampicillin, neomycin, methotrexate, or tetracycline, (b) complement
auxotrophic deficiencies, or (c) supply critical nutrients not
available from complex media, e.g., the gene encoding D-alanine
racemase for Bacilli.
[0083] One example of a selection scheme utilizes a drug to arrest
growth of a host cell. Those cells that are successfully
transformed with a heterologous gene produce a protein conferring
drug resistance and thus survive the selection regimen. Examples of
such dominant selection use the drugs neomycin (Southern et al., J.
Molec. Appl. Genet., 1:327 [1982]), mycophenolic acid (Mulligan et
al., Science, 209:1422 [1980]) or hygromycin. Sugden et al., Mol.
Cell. Biol., 5:410-413 (1985). The three examples given above
employ bacterial genes under eukaryotic control to convey
resistance to the appropriate drug G418 or neomycin (geneticin),
xgpt (mycophenolic acid), or hygromycin, respectively.
[0084] Another example of suitable selectable markers for mammalian
cells are those that enable the identification of cells competent
to take up the VRP nucleic acid, such as DHFR or thymidine kinase.
The mammalian cell transformants are placed under selection
pressure that only the transformants are uniquely adapted to
survive by virtue of having taken up the marker. Selection pressure
is imposed by culturing the transformants under conditions in which
the concentration of selection agent in the medium is successively
changed, thereby leading to amplification of both the selection
gene and the DNA that encodes VRP. Amplification is the process by
which genes in greater demand for the production of a protein
critical for growth are reiterated in tandem within the chromosomes
of successive generations of recombinant cells. Increased
quantities of VRP are synthesized from the amplified DNA. Other
examples of amplifiable genes include metallothionein-I and -II,
preferably primate metallothionein genes, adenosine deaminase,
omithine decarboxylase, etc.
[0085] For example, cells transformed with the DHFR selection gene
are first identified by culturing all of the transformants in a
culture medium that contains methotrexate (Mtx), a competitive
antagonist of DHFR. An appropriate host cell when wild-type DHFR is
employed is the Chinese hamster ovary (CHO) cell line deficient in
DHFR activity, prepared and propagated as described by Urlaub and
Chasin, Proc. Natl. Acad. Sci. USA, 77:4216 (1980). The transformed
cells are then exposed to increased levels of methotrexate. This
leads to the synthesis of multiple copies of the DHFR gene, and,
concomitantly, multiple copies of other DNA comprising the
expression vectors, such as the DNA encoding VRP. This
amplification technique can be used with any otherwise suitable
host, e.g., ATCC No. CCL61 CHO-KL, notwithstanding the presence of
endogenous DHFR if, for example, a mutant DHFR gene that is highly
resistant to Mtx is employed (EP 117,060).
[0086] Alternatively, host cells [particularly wild-type hosts that
contain endogenous DHFR] transformed or co-transformed with DNA
sequences encoding VRP, wild-type DHFR protein, and another
selectable marker such as aminoglycoside 3'-phosphotransferase
(APH) can be selected by cell growth in medium containing a
selection agent for the selectable marker such as an
aminoglycosidic antibiotic, e.g., kanamycin, neomycin, or G418. See
U.S. Pat. No. 4,965,199.
[0087] A suitable selection gene for use in yeast is the trp1 gene
present in the yeast plasmid YRp7. Stinchcomb et al., Nature,
282:39 (1979); Kingsman et al., Gene, 7:141 (1979); Tschemper et
al., Gene, 10:157 (1980). The trp1 gene provides a selection marker
for a mutant strain of yeast lacking the ability to grow in
tryptophan, for example, ATCC No. 44076 or PEP4-1. Jones, Genetics,
85:12 (1977). The presence of the trp1 lesion in the yeast host
cell genome then provides an effective environment for detecting
transformation by growth in the absence of tryptophan. Similarly,
Leu2-deficient yeast strains (ATCC 20,622 or 38,626) are
complemented by known plasmids bearing the Leu2 gene.
[0088] In addition, vectors derived from the 1.6 .mu.m circular
plasmid pKD1 can be used for transformation of Kluyveromyces
yeasts. Bianchi et al., Curr. Genet., 12:185 (1987). More recently,
an expression system for large-scale production of recombinant calf
chymosin was reported for K. lactis. Van den Berg, Bio/Technology,
8:135 (1990). Stable multi-copy expression vectors for secretion of
mature recombinant human serum albumin by industrial strains of
Kluyveromyces have also been disclosed. Fleer et al.,
Bio/Technology, 9:968-975 (1991).
[0089] (iv) Promoter Component
[0090] Expression and cloning vectors usually contain a promoter
that is recognized by the host organism and is operably linked to
the VRP nucleic acid. Promoters are untranslated sequences located
upstream (5') to the start codon of a structural gene (generally
within about 100 to 1000 bp) that control the transcription and
translation of particular nucleic acid sequence, such as the VRP
nucleic acid sequence, to which they are operably linked. Such
promoters typically fall into two classes, inducible and
constitutive. Inducible promoters are promoters that initiate
increased levels of transcription from DNA under their control in
response to some change in culture conditions, e.g., the presence
or absence of a nutrient or a change in temperature. At this time a
large number of promoters recognized by a variety of potential host
cells are well known. These promoters are operably linked to
VRP-encoding DNA by removing the promoter from the source DNA by
restriction enzyme digestion and inserting the isolated promoter
sequence into the vector. Both the native VRP promoter sequence and
many heterologous promoters may be used to direct amplification
and/or expression of the VRP DNA. However, heterologous promoters
are preferred, as they generally permit greater transcription and
higher yields of VRP as compared to the native VRP promoter.
[0091] Promoters suitable for use with prokaryotic hosts include
the .beta.-lactamase and lactose promoter systems (Chang et al.,
Nature, 275:615 [1978]; Goeddel et al., Nature, 281:544 [1979]),
alkaline phosphatase, a tryptophan (trp) promoter system (Goeddel,
Nucleic Acids Res., 8:4057 [1980]; EP 36,776), and hybrid promoters
such as the tac promoter. deBoer et al., Proc. Natl. Acad. Sci.
USA, 80:21-25 (1983). However, other known bacterial promoters are
suitable. Their nucleotide sequences have been published, thereby
enabling a skilled worker operably to ligate them to DNA encoding
VRP (Siebenlist et al., Cell, 20:269 [1980]) using linkers or
adaptors to supply any required restriction sites. Promoters for
use in bacterial systems also will contain a Shine-Dalgarno (S.D.)
sequence operably linked to the DNA encoding VRP.
[0092] Promoter sequences are known for eukaryotes. Virtually all
eukaryotic genes have an AT-rich region located approximately 25 to
30 bases upstream from the site where transcription is initiated.
Another sequence found 70 to 80 bases upstream from the start of
transcription of many genes is a CXCAAT region where X may be any
nucleotide. At the 3' end of most eukaryotic genes is an AATAAA
sequence that may be the signal for addition of the poly A tail to
the 3' end of the coding sequence. All of these sequences are
suitably inserted into eukaryotic expression vectors.
[0093] Examples of suitable promoting sequences for use with yeast
hosts include the promoters for 3-phosphoglycerate kinase (Hitzeman
et al., J. Biol. Chem., 255:2073 [1980]) or other glycolytic
enzymes (Hess et al., J. Adv. Enzyme Reg., 7:149 [1968]; Holland,
Biochemistry, 17:4900 [1978]), such as enolase,
glyceraldehyde-3-phosphate dehydrogenase, hexokinase, pyruvate
decarboxylase, phosphofructokinase, glucose-6-phosphate isomerase,
3-phosphoglycerate mutase, pyruvate kinase, triosephosphate
isomerase, phosphoglucose isomerase, and glucokinase.
[0094] Other yeast promoters, which are inducible promoters having
the additional advantage of transcription controlled by growth
conditions, are the promoter regions for alcohol dehydrogenase 2,
isocytochrome C, acid phosphatase, degradative enzymes associated
with nitrogen metabolism, metallothionein,
glyceraldehyde-3-phosphate dehydrogenase, and enzymes responsible
for maltose and galactose utilization. Suitable vectors and
promoters for use in yeast expression are further described in EP
73,657. Yeast enhancers also are advantageously used with yeast
promoters.
[0095] VRP transcription from vectors in mammalian host cells is
controlled, for example, by promoters obtained from the genomes of
viruses such as polyoma virus, fowlpox virus (UK 2,211,504
published 5 Jul. 1989), adenovirus (such as Adenovirus 2), bovine
papilloma virus, avian sarcoma virus, cytomegalovirus, a
retrovirus, hepatitis-B virus and most preferably Simian Virus 40
(SV40), from heterologous mammalian promoters, e.g., the actin
promoter or an immunoglobulin promoter, from heat-shock promoters,
and from the promoter normally associated with the VRP sequence,
provided such promoters are compatible with the host cell
systems.
[0096] The early and late promoters of the SV40 virus are
conveniently obtained as an SV40 restriction fragment that also
contains the SV40 viral origin of replication. Fiers et al.,
Nature, 273:113 (1978); Mulligan and Berg, Science, 209:1422-1427
(1980); Pavlakis et al., Proc. Natl. Acad. Sci. USA, 78:7398-7402
(1981). The immediate early promoter of the human cytomegalovirus
is conveniently obtained as a HindIII E restriction fragment.
Greenaway et al., Gene, 18:355-360 (1982). A system for expressing
DNA in mammalian hosts using the bovine papilloma virus as a vector
is disclosed in U.S. Pat. No. 4,419,446. A modification of this
system is described in U.S. Pat. No. 4,601,978. See also Gray et
al., Nature, 295:503-508 (1982) on expressing cDNA encoding immune
interferon in monkey cells; Reyes et al., Nature, 297:598-601
(1982) on expression of human .beta.-interferon cDNA in mouse cells
under the control of a thymidine kinase promoter from herpes
simplex virus; Canaani and Berg, Proc. Natl. Acad. Sci. USA
79:5166-5170 (1982) on expression of the human interferon .beta.1
gene in cultured mouse and rabbit cells; and Gorman et al., Proc.
Natl. Acad. Sci. USA, 79:6777-6781 (1982) on expression of
bacterial CAT sequences in CV-1 monkey kidney cells, chicken embryo
fibroblasts, Chinese hamster ovary cells, HeLa cells, and mouse
NIH-3T3 cells using the Rous sarcoma virus long terminal repeat as
a promoter.
[0097] (v) Enhancer Element Component
[0098] Transcription of a DNA encoding the VRP of this invention by
higher eukaryotes is often increased by inserting an enhancer
sequence into the vector. Enhancers are cis-acting elements of DNA,
usually about from 10 to 300 bp, that act on a promoter to increase
its transcription. Enhancers are relatively orientation and
position independent, having been found 5' (Laimins et al., Proc.
Natl. Acad. Sci. USA, 78:993 [1981]) and 3' (Lusky et al., Mol.
Cell Bio., 3:1108 [1983]) to the transcription unit, within an
intron (Banerji et al., Cell, 33:729 [1983]), as well as within the
coding sequence itself. Osborne et al., Mol. Cell Bio., 4:1293
(1984). Many enhancer sequences are now known from mammalian genes
(globin, elastase, albumin, .alpha.-fetoprotein, and insulin).
Typically, however, one will use an enhancer from a eukaryotic cell
virus. Examples include the SV40 enhancer on the late side of the
replication origin (bp 100-270), the cytomegalovirus early promoter
enhancer, the polyoma enhancer on the late side of the replication
origin, and adenovirus enhancers. See also Yaniv, Nature, 297:17-18
(1982) on enhancing elements for activation of eukaryotic
promoters. The enhancer may be spliced into the vector at a
position 5' or 3' to the VRP-encoding sequence, but is preferably
located at a site 5' from the promoter.
[0099] (vi) Transcription Termination Component
[0100] Expression vectors used in eukaryotic host cells (yeast,
fungi, insect, plant, animal, human, or nucleated cells from other
multicellular organisms) will also contain sequences necessary for
the termination of transcription and for stabilizing the mRNA. Such
sequences are commonly available from the 5' and, occasionally 3',
untranslated regions of eukaryotic or viral DNAs or cDNAs. These
regions contain nucleotide segments transcribed as polyadenylated
fragments in the untranslated portion of the mRNA encoding VRP.
[0101] (vii) Construction and Analysis of Vectors
[0102] Construction of suitable vectors containing one or more of
the above-listed components employs standard ligation techniques.
Isolated plasmids or DNA fragments are cleaved, tailored, and
re-ligated in the form desired to generate the plasmids
required.
[0103] For analysis to confirm correct sequences in plasmids
constructed, the ligation mixtures are used to transform E. coli
K12 strain 294 (ATCC 31,446) and successful transformants selected
by ampicillin or tetracycline resistance where appropriate.
Plasmids from the transformants are prepared, analyzed by
restriction endonuclease digestion, and/or sequenced by the method
of Messing et al., Nucleic Acids Res., 9:309 (1981) or by the
method of Maxam et al., Methods in Enzymology, 65:499 (1980).
[0104] (viii) Transient Expression Vectors
[0105] Particularly useful in the practice of this invention are
expression vectors that provide for the transient expression in
mammalian cells of DNA encoding VRP. In general, transient
expression involves the use of an expression vector that is able to
replicate efficiently in a host cell, such that the host cell
accumulates many copies of the expression vector and, in turn,
synthesizes high levels of a desired polypeptide encoded by the
expression vector. Sambrook et al., supra, pp. 16.17-16.22.
Transient expression systems, comprising a suitable expression
vector and a host cell, allow for the convenient positive
identification of polypeptides encoded by cloned DNAs, as well as
for the rapid screening of such polypeptides for desired biological
or physiological properties. Thus, transient expression systems are
particularly useful in the invention for purposes of identifying
analogs and variants of VRP that are biologically active VRP.
[0106] (ix) Suitable Exemplary Vertebrate Cell Vectors
[0107] Other methods, vectors, and host cells suitable for
adaptation to the synthesis of VRP in recombinant vertebrate cell
culture are described in Gething et al., Nature, 293:620-625
(1981); Mantei et al., Nature, 281:40-46 (1979); EP 117,060; and EP
117,058. A particularly useful plasmid for mammalian cell culture
expression of VRP is pRK5 (EP 307,247) or pSVI6B. WO 91/08291
published 13 Jun. 1991.
[0108] C. Selection and Transformation of Host Cells
[0109] Suitable host cells for cloning or expressing the DNA in the
vectors herein are the prokaryote, yeast, or higher eukaryote cells
described above. Suitable prokaryotes for this purpose include
eubacteria, such as Gram-negative or Gram-positive organisms, for
example, Enterobacteriaceae such as Escherichia, e.g., E. coli,
Enterobacter, Erwinia, Klebsiella, Proteus, Salmonella, e.g.,
Salmonella typhimurium, Serratia, e.g., Serratia marcescans, and
Shigella, as well as Bacilli such as B. subtilis and B.
licheniformis (e.g., B. licheniformis 41P disclosed in DD 266,710
published 12 Apr. 1989), Pseudomonas such as P. aeruginosa, and
Streptomyces. One preferred E. coli cloning host is E. coli 294
(ATCC 31,446), although other strains such as E. coli B, E. coli
X1776 (ATCC 31,537), and E. coli W3110 (ATCC 27,325) are suitable.
These examples are illustrative rather than limiting. Strain W3110
is a particularly preferred host or parent host because it is a
common host strain for recombinant DNA product fermentations.
Preferably, the host cell should secrete minimal amounts of
proteolytic enzymes. For example, strain W3110 may be modified to
effect a genetic mutation in the genes encoding proteins, with
examples of such hosts including E. coli W3110 strain 27C7. The
complete genotype of 27C7 is tonA.DELTA. ptr3 phoA.DELTA.E15
A(argF-lac)169 omp T.DELTA. degP4kan.sup.r. Strain 27C7 was
deposited on 30 Oct. 1991 in the American Type Culture Collection
as ATCC No. 55,244. Alternatively, the strain of E. coli having
mutant periplasmic protease disclosed in U.S. Pat. No. 4,946,783
issued 7 Aug. 1990 may be employed. Alternatively still, methods of
cloning, e.g., PCR or other nucleic acid polymerase reactions, are
suitable.
[0110] In addition to prokaryotes, eukaryotic microbes such as
filamentous fungi or yeast are suitable cloning or expression hosts
for VRP-encoding vectors. Saccharomyces cerevisiae, or common
baker's yeast, is the most commonly used among lower eukaryotic
host microorganisms. However, a number of other genera, species,
and strains are commonly available and useful herein, such as
Schizosaccharomyces pombe (Beach and Nurse, Nature, 290:140 [1981];
EP 139,383 published 2 May 1985); Kluyveromyces hosts (U.S. Pat.
No. 4,943,529; Fleer et al., supra) such as, e.g., K. lactis
[MW98-8C, CBS683, CBS4574; Louvencourt et al., J. Bacteriol., 737
(1983)], K. fragilis (ATCC 12,424), K. bulgaricus (ATCC 16,045), K.
wickeramii (ATCC 24,178), K. waltii (ATCC 56,500), K. drosophilarum
(ATCC 36,906; Van den Berg et al., supra), K. thermotolerans, and
K. marxianus; yarrowia [EP 402,226]; Pichia pastoris (EP 183,070;
Sreekrishna et al., J. Basic Microbiol., 28:265-278 [1988]);
Candida; Trichoderma reesia (EP 244,234); Neurospora crassa (Case
et al., Proc. Natl. Acad. Sci. USA, 76:5259-5263 [1979]);
Schwanniomyces such as Schwanniomyces occidentalis EP 394,538
published 31 Oct. 1990); and filamentous fungi such as, e.g.,
Neurospora, Penicillium, Tolypocladium (WO 91/00357 published 10
Jan. 1991), and Aspergillus hosts such as A. nidulans (Ballance et
al., Biochem. Biophys. Res. Commun., 112:284-289 [1983]; Tilburn et
al., Gene, 26:205-221 [1983]; Yelton et al., Proc. Natl. Acad. Sci.
USA, 81:1470-1474 [1984]) and A. niger. Kelly and Hynes, EMBO J.,
4:475-479 (1985).
[0111] Suitable host cells for the expression of glycosylated VRP
are derived from multicellular organisms. Such host cells are
capable of complex processing and glycosylation activities. In
principle, any higher eukaryotic cell culture is workable, whether
from vertebrate or invertebrate culture. Examples of invertebrate
cells include plant and insect cells. Numerous baculoviral strains
and variants and corresponding permissive insect host cells from
hosts such as Spodoptera frugiperda (caterpillar), Aedes aegypti
(mosquito), Aedes albopictus (mosquito), Drosophila melanogaster
(fruitfly), and Bombyx mori have been identified. See, e.g., Luckow
et al., Bio/Technology, 6:47-55 (1988); Miller et al., in Genetic
Engineering, Setlow et al., eds., Vol. 8 (Plenum Publishing, 1986),
pp. 277-279; and Maeda et al., Nature, 315:592-594 (1985). A
variety of viral strains for transfection are publicly available,
e.g., the L-1 variant of Autographa californica NPV and the Bm-5
strain of Bombyx mori NPV, and such viruses may be used as the
virus herein according to the present invention, particularly for
transfection of Spodoptera frugiperda cells.
[0112] Plant cell cultures of cotton, corn, potato, soybean,
petunia, tomato, and tobacco can be utilized as hosts. Typically,
plant cells are transfected by incubation with certain strains of
the bacterium Agrobacterium tumefaciens, which has been previously
manipulated to contain the VRP-encoding DNA. During incubation of
the plant cell culture with A. tumefaciens, the DNA encoding the
VRP is transferred to the plant cell host such that it is
transfected, and will, under appropriate conditions, express the
VRP-encoding DNA. In addition, regulatory and signal sequences
compatible with plant cells are available, such as the nopaline
synthase promoter and polyadenylation signal sequences. Depicker et
al., J. Mol. Appl. Gen., 1:561 (1982). In addition, DNA segments
isolated from the upstream region of the T-DNA 780 gene are capable
of activating or increasing transcription levels of
plant-expressible genes in recombinant DNA-containing plant tissue.
EP 321,196 published 21 Jun. 1989.
[0113] However, interest has been greatest in vertebrate cells, and
propagation of vertebrate cells in culture (tissue culture) has
become a routine procedure. See, e.g., Tissue Culture, Academic
Press, Kruse and Patterson, editors (1973). Examples of useful
mammalian host cell lines are monkey kidney CV1 line transformed by
SV40 (COS-7, ATCC CRL 1651); human embryonic kidney line (293 or
293 cells subcloned for growth in suspension culture, Graham et
al., J. Gen Virol., 36:59 [1977]); baby hamster kidney cells (BHK,
ATCC CCL 10); Chinese hamster ovary cells/-DHFR (CHO, Urlaub and
Chasin, Proc. Natl. Acad. Sci. USA, 77:4216 [1980]); mouse sertoli
cells (TM4, Mather, Biol. Reprod., 23:243-251 [1980]); monkey
kidney cells (CV1 ATCC CCL 70); African green monkey kidney cells
(VERO-76, ATCC CRL-1587); human cervical carcinoma cells (HELA,
ATCC CCL 2); canine kidney cells (MDCK, ATCC CCL 34); buffalo rat
liver cells (BRL 3A, ATCC CRL 1442); human lung cells (W138, ATCC
CCL 75); human liver cells (Hep G2, HB 8065); mouse mammary tumor
(MMT 060562, ATCC CCL51); TRI cells (Mather et al., Annals N.Y.
Acad. Sci., 383:44-68 [1982]); MRC 5 cells; FS4 cells; and a human
hepatoma line (Hep G2).
[0114] Host cells are transfected and preferably transformed with
the above-described expression or cloning vectors for VRP
production and cultured in conventional nutrient media modified as
appropriate for inducing promoters, selecting transformants, or
amplifying the genes encoding the desired sequences.
[0115] Transfection refers to the taking up of an expression vector
by a host cell whether or not any coding sequences are in fact
expressed. Numerous methods of transfection are known to the
ordinarily skilled artisan, for example, CaPO.sub.4 and
electroporation. Successful transfection is generally recognized
when any indication of the operation of this vector occurs within
the host cell.
[0116] Transformation means introducing DNA into an organism so
that the DNA is replicable, either as an extrachromosomal element
or by chromosomal integrant. Depending on the host cell used,
transformation is done using standard techniques appropriate to
such cells. The calcium treatment employing calcium chloride, as
described in section 1.82 of Sambrook et al., supra, or
electroporation is generally used for prokaryotes or other cells
that contain substantial cell-wall barriers. Infection with
Agrobacterium tumefaciens is used for transformation of certain
plant cells, as described by Shaw et al., Gene, 23:315 (1983) and
WO 89/05859 published 29 Jun. 1989. In addition, plants may be
transfected using ultrasound treatment as described in WO 91/00358
published 10 Jan. 1991.
[0117] For mammalian cells without such cell walls, the calcium
phosphate precipitation method of Graham and van der Eb, Virology,
52:456-457 (1978) is preferred. General aspects of mammalian cell
host system transformations have been described in U.S. Pat. No.
4,399,216 issued 16 Aug. 1983. Transformations into yeast are
typically carried out according to the method of Van Solingen et
al., J. Bact., 130:946 (1977) and Hsiao et al., Proc. Natl. Acad.
Sci. (USA), 76:3829 (1979). However, other methods for introducing
DNA into cells, such as by nuclear microinjection, electroporation,
bacterial protoplast fusion with intact cells, or polycations,
e.g., polybrene, polyornithine, etc., may also be used. For various
techniques for transforming mammalian cells, see Keown et al.,
Methods in Enzymology, 185:527-537 (1990) and Mansour et al.,
Nature, 336:348-352 (1988).
[0118] D. Culturing the Host Cells
[0119] Prokaryotic cells used to produce the VRP polypeptide of
this invention are cultured in suitable media as described
generally in Sambrook et al., supra.
[0120] The mammalian host cells used to produce the VRP of this
invention may be cultured in a variety of media. Commercially
available media such as Ham's F10 (Sigma), Minimal Essential Medium
([MEM], Sigma), RPMI-1640 (Sigma), and Dulbecco's Modified Eagle's
Medium ([DMEM], Sigma) are suitable for culturing the host cells.
In addition, any of the media described in Ham and Wallace, Meth.
Enz., 58:44 (1979), Barnes and Sato, Anal. Biochem.,102:255 (1980),
U.S. Pat. Nos. 4,767,704; 4,657,866; 4,927,762; 4,560,655; or
5,122,469; WO 90/03430; WO 87/00195; or U.S. Pat. No. Re. 30,985
may be used as culture media for the host cells. Any of these media
may be supplemented as necessary with hormones and/or other growth
factors (such as insulin, transferrin, or epidermal growth factor),
salts (such as sodium chloride, calcium, magnesium, and phosphate),
buffers (such as HEPES), nucleosides (such as adenosine and
thymidine), antibiotics (such as Gentamycin.TM. drug), trace
elements (defined as inorganic compounds usually present at final
concentrations in the micromolar range), and glucose or an
equivalent energy source. Any other necessary supplements may also
be included at appropriate concentrations that would be known to
those skilled in the art. The culture conditions, such as
temperature, pH, and the like, are those previously used with the
host cell selected for expression, and will be apparent to the
ordinarily skilled artisan.
[0121] In general, principles, protocols, and practical techniques
for maximizing the productivity of mammalian cell cultures can be
found in Mammalian Cell Biotechnology: a Practical Approach, M.
Butler, ed. (IRL Press, 1991).
[0122] The host cells referred to in this disclosure encompass
cells in culture as well as cells that are within a host
animal.
[0123] E. Detecting Gene Amplification/Expression
[0124] Gene amplification and/or expression may be measured in a
sample directly, for example, by conventional Southern blotting,
Northern blotting to quantitate the transcription of mRNA (Thomas,
Proc. Natl. Acad. Sci. USA, 77:5201-5205 [1980]), dot blotting (DNA
analysis), or in situ hybridization, using an appropriately labeled
probe, based on the sequences provided herein. Various labels may
be employed, most commonly radioisotopes, particularly .sup.32P.
However, other techniques may also be employed, such as using
biotin-modified nucleotides for introduction into a polynucleotide.
The biotin then serves as the site for binding to avidin or
antibodies, which may be labeled with a wide variety of labels,
such as radionuclides, fluorescers, enzymes, or the like.
Alternatively, antibodies may be employed that can recognize
specific duplexes, including DNA duplexes, RNA duplexes, and
DNA-RNA hybrid duplexes or DNA-protein duplexes. The antibodies in
turn may be labeled and the assay may be carried out where the
duplex is bound to a surface, so that upon the formation of duplex
on the surface, the presence of antibody bound to the duplex can be
detected.
[0125] Gene expression, alternatively, may be measured by
immunological methods, such as immunohistochemical staining of
tissue sections and assay of cell culture or body fluids, to
quantitate directly the expression of gene product. With
immunohistochemical staining techniques, a cell sample is prepared,
typically by dehydration and fixation, followed by reaction with
labeled antibodies specific for the gene product coupled, where the
labels are usually visually detectable, such as enzymatic labels,
fluorescent labels, luminescent labels, and the like. A
particularly sensitive staining technique suitable for use in the
present invention is described by Hsu et al., Am. J. Clin. Path.,
75:734-738 (1980).
[0126] Antibodies useful for immunohistochemical staining and/or
assay of sample fluids may be either monoclonal or polyclonal, and
may be prepared in any mammal. Conveniently, the antibodies may be
prepared against a native VRP polypeptide or against a synthetic
peptide based on the DNA sequences provided herein as described
further in Section 4 below.
[0127] F. Purification of VRP Polypeptide
[0128] VRP preferably is recovered from the culture medium as a
secreted polypeptide, although it also may be recovered from host
cell lysates when directly produced without a secretory signal. If
the VRP is membrane-bound, it can be released from the membrane
using a suitable detergent solution (e.g. Triton-X 100)
[0129] When VRP is produced in a recombinant cell other than one of
human origin, the VRP is completely free of proteins or
polypeptides of human origin. However, it is necessary to purify
VRP from recombinant cell proteins or polypeptides to obtain
preparations that are substantially homogeneous as to VRP. As a
first step, the culture medium or lysate is centrifuged to remove
particulate cell debris. VRP thereafter is purified from
contaminant soluble proteins and polypeptides, with the following
procedures being exemplary of suitable purification procedures: by
fractionation on an ion-exchange column; ethanol precipitation;
reverse phase HPLC; chromatography on silica or on a
cation-exchange resin such as DEAE; chromatofocusing; SDS-PAGE;
ammonium sulfate precipitation; gel filtration using, for example,
Sephadex G-75; and protein A Sepharose columns to remove
contaminants such as IgG.
[0130] In the preferred embodiment, the Flt4 receptor-IgG fusion is
immobilized on an affinity chromatography column and the VRP can be
isolated by affinity purification using this column. Alternatively,
the VRP is joined at its N-terminus to a glycoprotein D sequence
and is passed through an affinity chromatography column on which is
immobilized an anti-gD monoclonal antibody such as 5B6, which is
specific for a glycoprotein D sequence.
[0131] VRP variants in which residues have been deleted, inserted,
or substituted are recovered in the same fashion as native VRP,
taking account of any substantial changes in properties occasioned
by the variation. For example, preparation of a VRP fusion with
another protein or polypeptide, e.g., a bacterial or viral antigen,
facilitates purification; an immunoaffinity column containing
antibody to the antigen can be used to adsorb the fusion
polypeptide. Immunoaffinity columns such as a rabbit polyclonal
anti-VRP column can be employed to absorb the VRP variant by
binding it to at least one remaining immune epitope.
[0132] A protease inhibitor such as phenyl methyl sulfonyl fluoride
(PMSF) also may be useful to inhibit proteolytic degradation during
purification, and antibiotics may be included to prevent the growth
of adventitious contaminants. One skilled in the art will
appreciate that purification methods suitable for native VRP may
require modification to account for changes in the character of VRP
or its variants upon expression in recombinant cell culture.
[0133] G. Covalent Modifications of VRP Polypeptides
[0134] Covalent modifications of VRP polypeptides are included
within the scope of this invention. Both native VRP and amino acid
sequence variants of the VRP may be covalently modified. One type
of covalent modification of the VRP is introduced into the molecule
by reacting targeted amino acid residues of the VRP with an organic
derivatizing agent that is capable of reacting with selected side
chains or the N- or C-terminal residues of the VRP.
[0135] Cysteinyl residues most commonly are reacted with
.alpha.-haloacetates (and corresponding amines), such as
chloroacetic acid or chloroacetamide, to give carboxymethyl or
carboxyamidomethyl derivatives. Cysteinyl residues also are
derivatized by reaction with bromotrifluoroacetone,
.alpha.-bromo-.beta.-(5-imidozoyl)propionic acid, chloroacetyl
phosphate, N-alkylmaleimides, 3-nitro-2-pyridyl disulfide, methyl
2-pyridyl disulfide, p-chloromercuribenzoate,
2-chloromercuri4-nitrophenol, or
chloro-7-nitrobenzo-2-oxa-1,3-diazole.
[0136] Histidyl residues are derivatized by reaction with
diethylpyrocarbonate at pH 5.5-7.0 because this agent is relatively
specific for the histidyl side chain. Para-bromophenacyl bromide
also is useful; the reaction is preferably performed in 0.1M sodium
cacodylate at pH 6.0.
[0137] Lysinyl and amino terminal residues are reacted with
succinic or other carboxylic acid anhydrides. Derivatization with
these agents has the effect of reversing the charge of the lysinyl
residues. Other suitable reagents for derivatizing
.alpha.-amino-containing residues include imidoesters such as
methyl picolinimidate, pyridoxal phosphate, pyridoxal,
chloroborohydride, trinitrobenzenesulfonic acid, O-methylisourea,
2,4-pentanedione, and transaminase-catalyzed reaction with
glyoxylate.
[0138] Arginyl residues are modified by reaction with one or
several conventional reagents, among them phenylglyoxal,
2,3-butanedione, 1,2-cyclohexanedione, and ninhydrin.
Derivatization of arginine residues requires that the reaction be
performed under alkaline conditions because of the high pK.sub.a of
the guanidine functional group. Furthermore, these reagents may
react with the groups of lysine as well as with the arginine
epsilon-amino group.
[0139] The specific modification of tyrosyl residues may be made,
with particular interest in introducing spectral labels into
tyrosyl residues by reaction with aromatic diazonium compounds or
tetranitromethane. Most commonly, N-acetylimidizole and
tetranitromethane are used to form O-acetyl tyrosyl species and
3-nitro derivatives, respectively. Tyrosyl residues are iodinated
using .sup.125I or .sup.131I to prepare labeled proteins for use in
radioimmunoassay, the chloramine T method being suitable.
[0140] Carboxyl side groups (aspartyl or glutamyl) are selectively
modified by reaction with carbodiimides (R--N.dbd.C.dbd.N--R'),
where R and R' are different alkyl groups, such as
1-cyclohexyl-3-(2-morpholinyl-- 4-ethyl)carbodiimide or
1-ethyl-3-(4-azonia4,4-dimethylpentyl)carbodiimide- . Furthermore,
aspartyl and glutamyl residues are converted to asparaginyl and
glutaminyl residues by reaction with ammonium ions.
[0141] Derivatization with bifunctional agents is useful for
crosslinking VRP to a water-insoluble support matrix or surface for
use in the method for purifying anti-VRP antibodies, and
vice-versa. Commonly used crosslinking agents include, e.g.,
1,1-bis(diazoacetyl)-2-phenylethane, glutaraldehyde,
N-hydroxysuccinimide esters, for example, esters with
4-azidosalicylic acid, homobifunctional imidoesters, including
disuccinimidyl esters such as
3,3'-dithiobis(succinimidylpropionate), and bifunctional maleimides
such as bis-N-maleimido-1,8-octane. Derivatizing agents such as
methyl-3-[(p-azidophenyl)dithio]propioimidate yield
photoactivatable intermediates that are capable of forming
crosslinks in the presence of light. Alternatively, reactive
water-insoluble matrices such as cyanogen bromide-activated
carbohydrates and the reactive substrates described in U.S. Pat.
Nos. 3,969,287; 3,691,016; 4,195,128; 4,247,642; 4,229,537; and
4,330,440 are employed for protein immobilization.
[0142] Glutaminyl and asparaginyl residues are frequently
deamidated to the corresponding glutamyl and aspartyl residues,
respectively. These residues are deamidated under neutral or basic
conditions. The deamidated form of these residues falls within the
scope of this invention.
[0143] Other modifications include hydroxylation of proline and
lysine, phosphorylation of hydroxyl groups of seryl or threonyl
residues, methylation of the .alpha.-amino groups of lysine,
arginine, and histidine side chains (T. E. Creighton, Proteins:
Structure and Molecular Properties, W.H. Freeman & Co., San
Francisco, pp. 79-86 [1983]), acetylation of the N-terminal amine,
and amidation of any C-terminal carboxyl group.
[0144] Another type of covalent modification of the VRP polypeptide
included within the scope of this invention comprises altering the
native glycosylation pattern of the polypeptide. By altering is
meant deleting one or more carbohydrate moieties found in native
VRP, and/or adding one or more glycosylation sites that are not
present in the native VRP.
[0145] Glycosylation of polypeptides is typically either N-linked
or O-linked. N-linked refers to the attachment of the carbohydrate
moiety to the side chain of an asparagine residue. The tripeptide
sequences asparagine-X-serine and asparagine-X-threonine, where X
is any amino acid except proline, are the recognition sequences for
enzymatic attachment of the carbohydrate moiety to the asparagine
side chain. Thus, the presence of either of these tripeptide
sequences in a polypeptide creates a potential glycosylation site.
O-linked glycosylation refers to the attachment of one of the
sugars N-aceylgalactosamine, galactose, or xylose to a
hydroxylamino acid, most commonly serine or threonine, although
5-hydroxyproline or 5-hydroxylysine may also be used.
[0146] Addition of glycosylation sites to the VRP polypeptide is
conveniently accomplished by altering the amino acid sequence such
that it contains one or more of the above-described tripeptide
sequences (for N-linked glycosylation sites). The alteration may
also be made by the addition of, or substitution by, one or more
serine or threonine residues to the native VRP sequence (for
O-linked glycosylation sites). For ease, the VRP amino acid
sequence is preferably altered through changes at the DNA level,
particularly by mutating the DNA encoding the VRP polypeptide at
preselected bases such that codons are generated that will
translate into the desired amino acids. The DNA mutation(s) may be
made using methods described above and in U.S. Pat. No. 5,364,934,
supra.
[0147] Another means of increasing the number of carbohydrate
moieties on the VRP polypeptide is by chemical or enzymatic
coupling of glycosides to the polypeptide. These procedures are
advantageous in that they do not require production of the
polypeptide in a host cell that has glycosylation capabilities for
N- or O-linked glycosylation. Depending on the coupling mode used,
the sugar(s) may be attached to (a) arginine and histidine, (b)
free carboxyl groups, (c) free sulfhydryl groups such as those of
cysteine, (d) free hydroxyl groups such as those of serine,
threonine, or hydroxyproline, (e) aromatic residues such as those
of phenylalanine, tyrosine, or tryptophan, or (f) the amide group
of glutamine. These methods are described in WO 87/05330 published
11 Sep. 1987, and in Aplin and Wriston, CRC Crit. Rev. Biochem.,
pp. 259-306 (1981).
[0148] Removal of carbohydrate moieties present on the VRP
polypeptide may be accomplished chemically or enzymatically.
Chemical deglycosylation requires exposure of the polypeptide to
the compound trifluoromethanesulfonic acid, or an equivalent
compound. This treatment results in the cleavage of most or all
sugars except the linking sugar (N-acetylglucosamine or
N-acetylgalactosamine), while leaving the polypeptide intact.
Chemical deglycosylation is described by Hakimuddin, et al., Arch.
Biochem. Biophys., 259:52 (1987) and by Edge et al., Anal.
Biochem., 118:131 (1981). Enzymatic cleavage of carbohydrate
moieties on polypeptides can be achieved by the use of a variety of
endo- and exo-glycosidases as described by Thotakura et al., Meth.
Enzymol., 138:350 (1987).
[0149] Glycosylation at potential glycosylation sites may be
prevented by the use of the compound tunicamycin as described by
Duskin et al., J. Biol. Chem., 257:3105 (1982). Tunicamycin blocks
the formation of protein-N-glycoside linkages.
[0150] Another type of covalent modification of VRP comprises
linking the VRP polypeptide to one of a variety of nonproteinaceous
polymers, e.g., polyethylene glycol, polypropylene glycol, or
polyoxyalkylenes, in the manner set forth in U.S. Pat. Nos.
4,640,835; 4,496,689; 4,301,144; 4,670,417; 4,791,192 or
4,179,337.
[0151] Since it is often difficult to predict in advance the
characteristics of a variant VRP, it will be appreciated that some
screening of the recovered variant will be needed to select the
optimal variant. A change in the immunological character of the VRP
molecule, such as affinity for a given antibody, is also able to be
measured by a competitive-type immunoassay. The variant is assayed
for changes in the suppression or enhancement of its mitogenic
activity by comparison to the activity observed for native VRP in
the same assay. For example, one can screen for the ability of the
variant VRP to stimulate protein kinase activity of the Flt4
receptor as described in Example 5 herein. Other potential
modifications of protein or polypeptide properties such as redox or
thermal stability, hydrophobicity, susceptibility to proteolytic
degradation, or the tendency to aggregate with carriers or into
multimers are assayed by methods well known in the art.
[0152] H. Epitope-Tagged VRP
[0153] This invention encompasses chimeric polypeptides comprising
VRP fused to another polypeptide. In one preferred embodiment, the
chimeric polypeptide comprises a fusion of the VRP with a tag
polypeptide which provides an epitope to which an anti-tag antibody
can selectively bind. The epitope tag is generally placed at the
amino- or carboxyl-terminus of the VRP. Such epitope-tagged forms
of the VRP are desirable, as the presence thereof can be detected
using a labeled antibody against the tag polypeptide. Also,
provision of the epitope tag enables the VRP to be readily purified
by affinity purification using the anti-tag antibody. Affinity
purification techniques and diagnostic assays involving antibodies
are described later herein.
[0154] Tag polypeptides and their respective antibodies are well
known in the art. Examples include the flu HA tag polypeptide and
its antibody 12CA5 (Field et al., Mol. Cell. Biol., 8:2159-2165
[1988]); the c-myc tag and the 8F9, 3C7, 6E10, G4, B7 and E10
antibodies thereto (Evan et al., Molecular and Cellular Biology,
5:3610-3616 [1985]); and the Herpes Simplex virus glycoprotein D
(gD) tag and its antibody. Paborsky et al., Protein Engineering,
3(6):547-553 (1990). Other tag polypeptides have been disclosed.
Examples include the Flag-peptide (Hopp et al., BioTechnology,
6:1204-1210 [1988]); the KT3 epitope peptide (Martin et al.,
Science, 255:192-194 [1992]); an .alpha.-tubulin epitope peptide
(Skinner et al., J. Biol. Chem., 266:15163-15166 [1991]); and the
T7 gene 10 protein peptide tag. Lutz-Freyermuth et al., Proc. Natl.
Acad. Sci. USA, 87:6393-6397 (1990). Once the tag polypeptide has
been selected, an antibody thereto can be generated using the
techniques disclosed herein.
[0155] The general methods suitable for the construction and
production of epitope-tagged VRP are the same as those disclosed
hereinabove with regard to (native or variant) VRP. VRP-tag
polypeptide fusions are most conveniently constructed by fusing the
cDNA sequence encoding the VRP portion in-frame to the tag
polypeptide DNA sequence and expressing the resultant DNA fusion
construct in appropriate host cells. Ordinarily, when preparing the
VRP-tag polypeptide chimeras of the present invention, nucleic acid
encoding the VRP will be fused at its 3' end to nucleic acid
encoding the N-terminus of the tag polypeptide, however 5' fusions
are also possible.
[0156] Epitope-tagged VRP can be conveniently purified by affinity
chromatography using the anti-tag antibody. The matrix to which the
affinity antibody is attached is most often agarose, but other
matrices are available (e.g. controlled pore glass or
poly(styrenedivinyl)benzene)- . The epitope-tagged VRP can be
eluted from the affinity column by varying the buffer pH or ionic
strength or adding chaotropic agents, for example.
[0157] 2. Therapeutic Uses, Compositions, and Administration of
VRP
[0158] VRP is believed to find therapeutic use for treating mammals
via stimulation or inhibition of growth and/or differentiation
and/or activation of cells having the Flt4 receptor or one or more
other VRP receptors. Exogenous VRP may be administered to a patient
in these circumstances. The human VRP is clearly useful insofar as
it can be administered to a human having depressed levels of
endogenous VRP, preferably in the situation where such depressed
levels lead to a pathological disorder, or where there is lack of
activation or inhibition of the Flt4 receptor or one or more other
VRP receptors.
[0159] Various potential therapeutic uses of VRP include those in
which VEGF is useful. Examples of these include uses associated
with the vascular endothelium, such as the treatment of traumata to
the vascular network, in view of the demonstrated rapid promotion
by VEGF of the proliferation of vascular endothelial cells that
would surround the traumata and in view of the relationship between
VEGF and the VRP established herein. Examples of such traumata that
could be so treated include, but are not limited to, surgical
incisions, particularly those involving the heart, wounds,
including lacerations, incisions, and penetrations of blood
vessels, and surface ulcers involving the vascular endothelium such
as diabetic, haemophiliac, and varicose ulcers. Other physiological
conditions that could be improved based on the selective mitogenic
character of the VRP are also included herein.
[0160] For the traumatic indications referred to above, the VRP
molecule will be formulated and dosed in a fashion consistent with
good medical practice taking into account the specific disorder to
be treated, the condition of the individual patient, the site of
delivery of the VRP, the method of administration, and other
factors known to practitioners.
[0161] Additional indications for the VRP are in the treatment of
full-thickness wounds such as dermal ulcers, including the
categories of pressure sores, venous ulcers, and diabetic ulcers,
as well as of full-thickness burns and injuries where angiogenesis
is required to prepare the burn or injured site for a skin graft or
flap. In this case the VRP is either applied directly to the site
or it is used to soak the skin or flap that is being transplanted
prior to grafting. In a similar fashion, the VRP can be used in
plastic surgery when reconstruction is required following a burn or
other trauma, or for cosmetic purposes.
[0162] Angiogenesis is also important in keeping wounds clean and
non-infected. The VRP can therefore be used in association with
general surgery and following the repair of cuts and lacerations.
It is particularly useful in the treatment of abdominal wounds with
a high risk of infection. Neovascularization is also key to
fracture repair, since blood vessels develop at the site of bone
injury. Administration of the VRP to the site of a fracture is
therefore another utility.
[0163] In cases where the VRP is being used for topical wound
healing, as described above, it may be administered by any of the
routes described below for the re-endothelialization of vascular
tissue, or more preferably by topical means. In these cases, it
will be administered as either a solution, spray, gel, cream,
ointment, or dry powder directly to the site of injury.
Slow-release devices directing the VRP to the injured site will
also be used. In topical applications, the VRP will be applied at a
concentration ranging from about 50 to 1,000 .mu.g/mL, either in a
single application, or in dosing regimens that are daily or every
few days for a period of one week to several weeks. Generally, the
amount of topical formulation administered is that which is
sufficient to apply from about 0.1 to 100 .mu.g/cm.sup.2 of the
VRP, based on the surface area of the wound.
[0164] The VRP can be used as a post-operative wound healing agent
in balloon angioplasty, a procedure in which vascular endothelial
cells are removed or damaged, together with compression of
atherosclerotic plaques. The VRP can be applied to inner vascular
surfaces by systemic or local intravenous application either as
intravenous bolus injection or infusions. If desired, the VRP can
be administered over time using a micrometering pump. Suitable
compositions for intravenous administration comprise the VRP in an
amount effective to promote endothelial cell growth and a
parenteral carrier material. The VRP can be present in the
composition over a wide range of concentrations, for example, from
about 50 .mu.g/mL to about 1,000 .mu.g/mL using injections of 3 to
10 mL per patient, administered once or in dosing regimens that
allow for multiple applications. Any of the known parenteral
carrier vehicles can be used, such as normal saline or 5-10%
dextrose.
[0165] The VRP can also be used to promote endothelialization in
vascular graft surgery. In the case of vascular grafts using either
transplanted vessels or synthetic material, for example, the VRP
can be applied to the surfaces of the graft and/or at the junctions
of the graft and the existing vasculature to promote the growth of
vascular endothelial cells. For such applications, the VRP can be
applied intravenously as described above for balloon angioplasty or
it can be applied directly to the surfaces of the graft and/or the
existing vasculature either before or during surgery. In such cases
it may be desired to apply the VRP in a thickened carrier material
so that it will adhere to the affected surface. Suitable carrier
materials include, for example, 1-5% carbopol. The VRP can be
present in the carrier over a wide range of concentrations, for
example, from about 50 .mu.g/mg to about 1,000 .mu.g/mg.
Alternatively, the VRP can be delivered to the site by a
micrometering pump as a parenteral solution.
[0166] The VRP can also be employed to repair vascular damage
following myocardial infarction and to circumvent the need for
coronary bypass surgery by stimulating the growth of a collateral
circulation. The VRP is administered intravenously for this
purpose, either in individual injections or by micrometering pump
over a period of time as described above or by direct infusion or
injection to the site of damaged cardial muscle. Therapeutic
formulations of VRP are prepared for storage by mixing VRP having
the desired degree of purity with optional physiologically
acceptable carriers, excipients, or stabilizers (Remington's
Pharmaceutical Sciences, 16th edition, Osol, A., Ed., [1980]), in
the form of lyophilized cake or aqueous solutions. Acceptable
carriers, excipients, or stabilizers are nontoxic to recipients at
the dosages and concentrations employed, and include buffers such
as phosphate, citrate, and other organic acids; antioxidants
including ascorbic acid; low molecular weight (less than about 10
residues) polypeptides; proteins, such as serum albumin, gelatin,
or immunoglobulins; hydrophilic polymers such as
polyvinylpyrrolidone; amino acids such as glycine, glutamine,
asparagine, arginine, or lysine; monosaccharides, disaccharides,
and other carbohydrates including glucose, mannose, or dextrins;
chelating agents such as EDTA; sugar alcohols such as mannitol or
sorbitol; salt-forming counter-ions such as sodium; and/or
non-ionic surfactants such as Tween, Pluronics or polyethylene
glycol (PEG).
[0167] The VRP also may be entrapped in microcapsules prepared, for
example, by coacervation techniques or by interfacial
polymerization (for example, hydroxymethylcellulose or
gelatin-microcapsules and poly-[methylmethacylate] microcapsules,
respectively), in colloidal drug delivery systems (for example,
liposomes, albumin microspheres, microemulsions, nano-particles,
and nanocapsules), or in macroemulsions. Such techniques are
disclosed in Remington's Pharmaceutical Sciences, supra.
[0168] VRP to be used for in vivo administration must be sterile.
This is readily accomplished by filtration through sterile
filtration membranes, prior to or following lyophilization and
reconstitution. VRP ordinarily will be stored in lyophilized form
or in solution.
[0169] Therapeutic VRP compositions generally are placed into a
container having a sterile access port, for example, an intravenous
solution bag or vial having a stopper pierceable by a hypodermic
injection needle.
[0170] The route of VRP administration is in accord with known
methods, e.g., those routes set forth above for specific
indications, as well as the general routes of injection or infusion
by intravenous, intraperitoneal, intracerebral, intramuscular,
intraocular, intraarterial, or intralesional means, or sustained
release systems as noted below. VRP is administered continuously by
infusion or by bolus injection. Generally, where the disorder
permits, one should formulate and dose the VRP for site-specific
delivery. This is convenient in the case of wounds and ulcers.
[0171] Suitable examples of sustained-release preparations include
semipermeable matrices of solid hydrophobic polymers containing the
protein, which matrices are in the form of shaped articles, e.g.,
films, or microcapsules. Examples of sustained-release matrices
include polyesters, hydrogels [e.g.,
poly(2-hydroxyethyl-methacrylate) as described by Langer et al., J.
Biomed. Mater. Res., 15:167-277 (1981) and Langer, Chem. Tech.,
12:98-105 (1982) or poly(vinylalcohol)], polylactides (U.S. Pat.
No. 3,773,919, EP 58,481), copolymers of L-glutamic acid and gamma
ethyl-L-glutamate (Sidman et al., Biopolymers, 22:547-556 [1983]),
non-degradable ethylene-vinyl acetate (Langer et al., supra),
degradable lactic acid-glycolic acid copolymers such as the Lupron
Depot.TM. (injectable microspheres composed of lactic acid-glycolic
acid copolymer and leuprolide acetate), and
poly-D-(-)-3-hydroxybutyric acid (EP 133,988).
[0172] While polymers such as ethylene-vinyl acetate and lactic
acid-glycolic acid enable release of molecules for over 100 days,
certain hydrogels release proteins for shorter time periods. When
encapsulated proteins remain in the body for a long time, they may
denature or aggregate as a result of exposure to moisture at
37.degree. C., resulting in a loss of biological activity and
possible changes in immunogenicity. Rational strategies can be
devised for protein stabilization depending on the mechanism
involved. For example, if the aggregation mechanism is discovered
to be intermolecular S--S bond formation through thio-disulfide
interchange, stabilization may be achieved by modifying sulfhydryl
residues, lyophilizing from acidic solutions, controlling moisture
content, using appropriate additives, and developing specific
polymer matrix compositions.
[0173] Sustained-release VRP compositions also include liposomally
entrapped VRP. Liposomes containing VRP are prepared by methods
known per se: DE 3,218,121; Epstein et al., Proc. Natl. Acad. Sci.
USA, 82:3688-3692 (1985); Hwang et al., Proc. Natl. Acad. Sci. USA,
77:4030-4034 (1980); EP 52,322; EP 36,676; EP 88,046; EP 143,949;
EP 142,641; Japanese patent application 83-118008; U.S. Pat. Nos.
4,485,045 and 4,544,545; and EP 102,324. Ordinarily the liposomes
are of the small (about 200-800 Angstroms) unilamellar type in
which the lipid content is greater than about 30 mol. %
cholesterol, the selected proportion being adjusted for the optimal
VRP therapy.
[0174] When applied topically, the VRP is suitably combined with
other ingredients, such as carriers and/or adjuvants. There are no
limitations on the nature of such other ingredients, except that
they must be pharmaceutically acceptable and efficacious for their
intended administration, and cannot degrade the activity of the
active ingredients of the composition. Examples of suitable
vehicles include ointments, creams, gels, or suspensions, with or
without purified collagen. The compositions also may be impregnated
into transdermal patches, plasters, and bandages, preferably in
liquid or semi-liquid form.
[0175] For obtaining a gel formulation, the VRP formulated in a
liquid composition may be mixed with an effective amount of a
water-soluble polysaccharide or synthetic polymer such as PEG to
form a gel of the proper viscosity to be applied topically. The
polysaccharide that may be used includes, for example, cellulose
derivatives such as etherified cellulose derivatives, including
alkyl celluloses, hydroxyalkyl celluloses, and alkylhydroxyalkyl
celluloses, for example, methylcellulose, hydroxyethyl cellulose,
carboxymethyl cellulose, hydroxypropyl methylcellulose, and
hydroxypropyl cellulose; starch and fractionated starch; agar;
alginic acid and alginates; gum arabic; pullullan; agarose;
carrageenan; dextrans; dextrins; fructans; inulin; mannans; xylans;
arabinans; chitosans; glycogens; glucans; and synthetic
biopolymers; as well as gums such as xanthan gum; guar gum; locust
bean gum; gum arabic; tragacanth gum; and karaya gum; and
derivatives and mixtures thereof. The preferred gelling agent
herein is one that is inert to biological systems, nontoxic, simple
to prepare, and not too runny or viscous, and will not destabilize
the VRP held within it.
[0176] Preferably the polysaccharide is an etherified cellulose
derivative, more preferably one that is well defined, purified, and
listed in USP, e.g., methylcellulose and the hydroxyalkyl cellulose
derivatives, such as hydroxypropyl cellulose, hydroxyethyl
cellulose, and hydroxypropyl methylcellulose. Most preferred herein
is methylcellulose.
[0177] The polyethylene glycol useful for gelling is typically a
mixture of low and high molecular weight PEGs to obtain the proper
viscosity. For example, a mixture of a PEG of molecular weight
400-600 with one of molecular weight 1500 would be effective for
this purpose when mixed in the proper ratio to obtain a paste.
[0178] The term "water soluble" as applied to the polysaccharides
and PEGs is meant to include colloidal solutions and dispersions.
In general, the solubility of the cellulose derivatives is
determined by the degree of substitution of ether groups, and the
stabilizing derivatives useful herein should have a sufficient
quantity of such ether groups per anhydroglucose unit in the
cellulose chain to render the derivatives water soluble. A degree
of ether substitution of at least 0.35 ether groups per
anhydroglucose unit is generally sufficient. Additionally, the
cellulose derivatives may be in the form of alkali metal salts, for
example, the Li, Na, K, or Cs salts.
[0179] If methylcellulose is employed in the gel, preferably it
comprises about 2-5%, more preferably about 3%, of the gel and the
VRP is present in an amount of about 300-1000 mg per ml of gel.
[0180] An effective amount of VRP to be employed therapeutically
will depend, for example, upon the therapeutic objectives, the
route of administration, and the condition of the patient.
Accordingly, it will be necessary for the therapist to titer the
dosage and modify the route of administration as required to obtain
the optimal therapeutic effect. Typically, the clinician will
administer the VRP until a dosage is reached that achieves the
desired effect. A typical daily dosage for systemic treatment might
range from about 1 .mu.g/kg to up to 10 mg/kg or more, depending on
the factors mentioned above. As an alternative general proposition,
the VRP is formulated and delivered to the target site or tissue at
a dosage capable of establishing in the tissue a VRP level greater
than about 0.1 ng/cc up to a maximum dose that is efficacious but
not unduly toxic. This intra-tissue concentration should be
maintained if possible by continuous infusion, sustained release,
topical application, or injection at empirically determined
frequencies. The progress of this therapy is easily monitored by
conventional assays.
[0181] It is within the scope hereof to combine the VRP therapy
with other novel or conventional therapies (e.g., growth factors
such as VEGF, acidic or basic fibroblast growth factor (aFGF or
bFGF, respectively), platelet-derived growth factor (PDGF),
insulin-like growth factor (IGF-I or IGF-II), nerve growth factor
(NGF), anabolic steroids, EGF or TGF-.alpha.) for enhancing the
activity of any of the growth factors, including the VRP, in
promoting cell proliferation and repair. It is not necessary that
such co-treatment drugs be included per se in the compositions of
this invention, although this will be convenient where such drugs
are proteinaceous. Such admixtures are suitably administered in the
same manner and for the same purposes as the VRP used alone. The
useful molar ratio of VRP to such secondary growth factors is
typically 1:0.1-10, with about equimolar amounts being
preferred.
[0182] 3. Non-Therapeutic, Diagnostic Uses for VRP
[0183] The nucleic acid encoding the VRP may be used as a
diagnostic for tissue-specific typing. For example, such procedures
as in situ hybridization, Northern and Southern blotting, and PCR
analysis may be used to determine whether DNA and/or RNA encoding
VRP is present in the cell type(s) being evaluated. VRP nucleic
acid or polypeptide may also be used as diagnostic markers. For
example, the VRP may be labeled, using the techniques described
herein, and expression of nucleic acid molecules encoding a Flt4
receptor or another VRP receptor can be quantified, using the
labelled VRP.
[0184] If the human VRP-encoding nucleic acid is localized to a
human chromosome, the nucleic acid for human VRP can be used as a
marker for this human chromosome.
[0185] VRP nucleic acid is also useful for the preparation of VRP
polypeptide by recombinant techniques exemplified herein.
[0186] Isolated VRP polypeptide may be used in quantitative
diagnostic assays as a standard or control against which samples
containing unknown quantities of VRP may be prepared.
[0187] VRP preparations are also useful in generating antibodies,
as standards in assays for VRP (e.g., by labeling VRP for use as a
standard in a radioimmunoassay, radioreceptor assay, or
enzyme-linked immunoassay), for detecting the presence of the Flt4
receptor or one or more other VRP receptors in a biological sample
(e.g., using a labeled VRP), in affinity purification techniques,
and in competitive-type receptor binding assays when labeled with
radioiodine, enzymes, fluorophores, spin labels, or the like.
[0188] The VRP is also useful as a diagnostic tool. For example,
the VRP can be produced in prokaryotic cells using the techniques
elaborated herein and the unglycosylated protein so produced can be
used as a molecular weight marker. The deduced molecular weight
(mw) of the VRP is about 44.8 kDa. To use the VRP as a molecular
weight marker, gel filtration chromatography or SDS-PAGE, for
example, will be used to separate protein(s) for which it is
desired to determine their molecular weight(s) in substantially the
normal way. The VRP and other molecular weight markers will be used
as standards to provide a range of molecular weights. For example,
phosphorylase b (mw=97,400), bovine serum albumin (mw=68,000),
ovalbumin (mw=46,000), VRP (mw=44,800), trypsin inhibitor
(mw=20,100), and lysozyme (mw=14,400) can be used a mw markers. The
other molecular weight markers mentioned here can be purchased
commercially from Amersham Corporation, Arlington Heights, Ill.,
for example. Often, the molecular weight markers will be labeled to
enable easy detection following separation. Techniques for labeling
antibodies and proteins are discussed herein and are well known in
the art. For example, the molecular weight markers may be
biotinylated and, following separation on SDS-PAGE, for example,
the blot can be incubated with streptavidin-horseradish peroxidase.
The bands can then be detected by light detection.
[0189] It may also be useful to grow certain cells having the Flt4
receptor or one or more other VRP receptors ex vivo using the VRP
as an angiogenic factor or growth factor. Thus, for example, the
VRP can be used as a growth factor in the in vitro culturing of
endothelial cells. For such uses, the VRP can be added to the cell
culture medium at a concentration from about 10 pg/mL to about 10
ng/mL.
[0190] These cells which are to be grown ex vivo may simultaneously
be exposed to other known growth factors or cytokines. Exemplary
cytokines include the interleukins (e.g., IL-3),
granulocyte-macrophage colony-stimulating factor (GM-CSF), VEGF,
macrophage colony-stimulating factor (M-CSF), granulocyte
colony-stimulating factor (G-CSF), granulocyte-macrophage
colony-stimulating factor (GM-CSF), erythropoietin (Epo),
lymphotoxin, steel factor (SLF), tumor necrosis factor (TNF), and
gamma-interferon. This results in proliferation and/or
differentiation of the cells having the Flt4 receptor or one or
more other VRP receptors.
[0191] In yet another aspect of the invention, the VRP may be used
for affinity purification of the Flt4 receptor or one or more other
VRP receptors. Briefly, this technique involves covalently
attaching the VRP to an inert and porous matrix (e.g., agarose
reacted with cyanogen bromide). A solution containing the Flt4
receptor or other VRP receptor(s) can then be passed through the
chromatographic material and can be subsequently released by
changing the elution conditions (e.g. by changing pH or ionic
strength).
[0192] The purified VRP, and the nucleic acid encoding it, may also
be sold as reagents for mechanism studies of VRP and its cognate
receptors, to study the role of the VRP and the Flt4 receptor or
other VRP receptors in normal growth and development, as well as
abnormal growth and development, e.g. in malignancies.
[0193] The VRP may be used for competitive screening of potential
agonists or antagonists for binding to the Flt4 receptor or other
VRP receptors. VRP variants are useful as standards or controls in
assays for the VRP, provided that they are recognized by the
analytical system employed, e.g. an anti-VRP antibody.
[0194] 4. VRP Antibody Preparation
[0195] A description follows as to the production of exemplary
antibodies as defined herein. These exemplary antibodies include
polyclonal, monoclonal, humanized, bispecific, or heteroconjugate
antibodies.
[0196] A. Polyclonal Antibodies
[0197] Polyclonal antibodies to the VRP generally are raised in
animals by multiple subcutaneous (sc) or intraperitoneal (ip)
injections of the VRP and an adjuvant. It may be useful to
conjugate the VRP to a protein that is immunogenic in the species
to be immunized, e.g., keyhole limpet hemocyanin, serum albumin,
bovine thyroglobulin, or soybean trypsin inhibitor using a
bifunctional or derivatizing agent, for example maleimidobenzoyl
sulfosuccinimide ester (conjugation through cysteine residues),
N-hydroxysuccinimide (through lysine residues), glytaraldehyde,
succinic anhydride, SOCl.sub.2, or R.sup.1N.dbd.C.dbd.NR, where R
and R.sup.1 are different alkyl groups.
[0198] Animals are immunized against the immunogenic conjugates or
derivatives by combining 1 mg of 1 .mu.g of conjugate (for rabbits
or mice, respectively) with 3 volumes of Freud's complete adjuvant
and injecting the solution intradermally at multiple sites. One
month later the animals are boosted with 1/5 to {fraction (1/10)}
the original amount of conjugate in Freud's complete adjuvant by
subcutaneous injection at multiple sites. Seven to 14 days later
the animals are bled and the serum is assayed for anti-VRP antibody
titer. Animals are boosted until the titer plateaus. Preferably,
the animal is boosted with a conjugate of the same VRP with a
different protein and/or the conjugation is through a different
cross-linking reagent. Conjugates also can be made in recombinant
cell culture as protein fusions. Also, aggregating agents such as
alum are used to enhance the immune response.
[0199] B. Monoclonal Antibodies
[0200] Monoclonal antibodies are obtained from a population of
substantially homogeneous antibodies, i.e., the individual
antibodies comprising the population are identical except for
possible naturally-occurring mutations that may be present in minor
amounts. Thus, the modifier "monoclonal" indicates the character of
the antibody as not being a mixture of discrete antibodies.
[0201] For example, the anti-VRP monoclonal antibodies of the
invention may be made using the hybridoma method first described by
Kohler and Milstein, Nature, 256:495 (1975), or may be made by
recombinant DNA methods. U.S. Pat. No. 4,816,567.
[0202] In the hybridoma method, a mouse or other appropriate host
animal, such as hamster, is immunized as hereinabove described to
elicit lymphocytes that produce, or are capable of producing,
antibodies that will specifically bind to the protein used for
immunization. Alternatively, lymphocytes may be immunized in vitro.
Lymphocytes then are fused with myeloma cells using a suitable
fusing agent, such as PEG, to form a hybridoma cell. Goding,
Monoclonal Antibodies: Principles and Practice, pp.59-103 (Academic
Press, 1986).
[0203] The hybridoma cells thus prepared are seeded and grown in a
suitable culture medium that preferably contains one or more
substances that inhibit the growth or survival of the unfused,
parental myeloma cells. For example, if the parental myeloma cells
lack the enzyme hypoxanthine guanine phosphoribosyl transferase
(HGPRT or HPRT), the culture medium for the hybridomas typically
will include hypoxanthine, aminopterin, and thymidine (HAT medium),
which substances prevent the growth of HGPRT-deficient cells.
[0204] Preferred myeloma cells are those that fuse efficiently,
support stable high-level expression of antibody by the selected
antibody-producing cells, and are sensitive to a medium such as HAT
medium. Among these, preferred myeloma cell lines are murine
myeloma lines, such as those derived from MOPC-21 and MPC-11 mouse
tumors available from the Salk Institute Cell Distribution Center,
San Diego, Calif. USA, and SP-2 cells available from the American
Type Culture Collection, Rockville, Md. USA. Human myeloma and
mouse-human heteromyeloma cell lines also have been described for
the production of human monoclonal antibodies. Kozbor, J. Immunol.,
133:3001 (1984); Brodeur et al., Monoclonal Antibody Production
Techniques and Applications, pp.51-63 (Marcel Dekker, Inc., New
York, 1987). See, also, Boerner et al., J. Immunol., 147:86-95
(1991) and WO 91/17769, published 28 Nov. 1991, for techniques for
the production of human monoclonal antibodies.
[0205] Culture medium in which hybridoma cells are growing is
assayed for production of monoclonal antibodies directed against
VRP. Preferably, the binding specificity of monoclonal antibodies
produced by hybridoma cells is determined by immunoprecipitation or
by an in vitro binding assay, such as radioimmunoassay (RIA) or
enzyme-linked immunoabsorbent assay (ELISA).
[0206] The binding affinity of the monoclonal antibody can, for
example, be determined by the Scatchard analysis of Munson and
Pollard, Anal. Biochem., 107:220 (1980).
[0207] After hybridoma cells are identified that produce antibodies
of the desired specificity, affinity, and/or activity, the clones
may be subcloned by limiting dilution procedures and grown by
standard methods. Goding, Monoclonal Antibodies: Principles and
Practice, pp.59-104 (Academic Press, 1986). Suitable culture media
for this purpose include, for example, Dulbecco's Modified Eagle's
Medium or RPMI-1640 medium. In addition, the hybridoma cells may be
grown in vivo as ascites tumors in an animal.
[0208] The monoclonal antibodies secreted by the subclones are
suitably separated from the culture medium, ascites fluid, or serum
by conventional immunoglobulin purification procedures such as, for
example, protein A-Sepharose, hydroxylapatite chromatography, gel
electrophoresis, dialysis, or affinity chromatography.
Alternatively, it is now possible to produce transgenic animals
(e.g. mice) that are capable, upon immunization, of producing a
full repertoire of human antibodies in the absence of endogenous
immunoglobulin production. For example, it has been described that
the homozygous deletion of the antibody heavy chain joining region
(J.sub.H) gene in chimeric and germ-line mutant mice results in
complete inhibition of endogenous antibody production. Transfer of
the human germ-line immunoglobulin gene array in such germ-line
mutant mice will result in the production of human antibodies upon
antigen challenge. See, e.g. Jakobovits et al., Proc. Natl. Acad.
Sci. USA, 90:2551-255 (1993); Jakobovits et al., Nature,
362:255-258 (1993).
[0209] In a further embodiment, antibodies or antibody fragments
can be isolated from antibody phage libraries generated using the
techniques described in McCafferty et al., Nature, 348:552-554
(1990), using the VRP to select for a suitable antibody or antibody
fragment. Clackson et al., Nature, 352:624-628 (1991) and Marks et
al., J. Mol. Biol., 222:581-597 (1991) describe the isolation of
murine and human antibodies, respectively, using phage libraries.
Subsequent publications describe the production of high-affinity
(nM range) human antibodies by chain shuffling (Mark et al.,
Bio/Technol., 10:779-783 [1992]), as well as combinatorial
infection and in vivo recombination as a strategy for constructing
very large phage libraries. Waterhouse et al., Nuc. Acids Res.,
21:2265-2266 (1993). Thus, these techniques are viable alternatives
to traditional monoclonal antibody hybridoma techniques for
isolation of "monoclonal" antibodies (especially human antibodies)
that are encompassed by the present invention.
[0210] DNA encoding the monoclonal antibodies of the invention is
readily isolated and sequenced using conventional procedures (e.g.,
by using oligonucleotide probes that are capable of binding
specifically to genes encoding the heavy and light chains of murine
antibodies). The hybridoma cells of the invention serve as a
preferred source of such DNA. Once isolated, the DNA may be placed
into expression vectors, which are then transfected into host cells
such as simian COS cells, Chinese hamster ovary (CHO) cells, or
myeloma cells that do not otherwise produce immunoglobulin protein,
to obtain the synthesis of monoclonal antibodies in the recombinant
host cells. The DNA also may be modified, for example, by
substituting the coding sequence for human heavy- and light-chain
constant domains in place of the homologous murine sequences
(Morrison et al., Proc. Nat. Acad. Sci. USA, 81, 6851 [1984]), or
by covalently joining to the immunoglobulin coding sequence all or
part of the coding sequence for a non-immunoglobulin polypeptide.
In that manner, "chimeric" or "hybrid" antibodies are prepared that
have the binding specificity of an anti-VRP monoclonal antibody
herein.
[0211] Typically, such non-immunoglobulin polypeptides are
substituted for the constant domains of an antibody of the
invention, or they are substituted for the variable domains of one
antigen-combining site of an antibody of the invention to create a
chimeric bivalent antibody comprising one antigen-combining site
having specificity for an VRP and another antigen-combining site
having specificity for a different antigen.
[0212] Chimeric or hybrid antibodies also may be prepared in vitro
using known methods in synthetic protein chemistry, including those
involving crosslinking agents. For example, immunotoxins may be
constructed using a disulfide exchange reaction or by forming a
thioether bond. Examples of suitable reagents for this purpose
include iminothiolate and methyl-4-mercaptobutyrimidate.
[0213] For diagnostic applications, the antibodies of the invention
typically will be labeled with a detectable moiety. The detectable
moiety can be any one which is capable of producing, either
directly or indirectly, a detectable signal. For example, the
detectable moiety may be a radioisotope, such as .sup.3H, .sup.14C,
.sup.32P, .sup.35S, or .sup.125I; a fluorescent or chemiluminescent
compound, such as fluorescein isothiocyanate, rhodamine, or
luciferin; or an enzyme, such as alkaline phosphatase,
beta-galactosidase, or horseradish peroxidase.
[0214] Any method known in the art for separately conjugating the
antibody to the detectable moiety may be employed, including those
methods described by Hunter et al., Nature, 144:945 (1962); David
et al., Biochemistry, 13:1014 (1974); Pain et al., J. Immunol.
Meth., 40:219 (1981); and Nygren, J. Histochem. and Cytochem.,
30:407 (1982).
[0215] The antibodies of the present invention may be employed in
any known assay method, such as competitive binding assays, direct
and indirect sandwich assays, and immunoprecipitation assays. Zola,
Monoclonal Antibodies: A Manual of Techniques, pp.147-158 (CRC
Press, Inc., 1987).
[0216] Competitive binding assays rely on the ability of a labeled
standard (which may be a VRP, or an immunologically reactive
portion thereof) to compete with the test sample analyte (VRP) for
binding with a limited amount of antibody. The amount of VRP in the
test sample is inversely proportional to the amount of standard
that becomes bound to the antibodies. To facilitate determining the
amount of standard that becomes bound, the antibodies generally are
insolubilized before or after the competition, so that the standard
and analyte that are bound to the antibodies may conveniently be
separated from the standard and analyte which remain unbound.
[0217] Sandwich assays involve the use of two antibodies, each
capable of binding to a different immunogenic portion, or epitope,
of the protein to be detected (VRP). In a sandwich assay, the test
sample analyte is bound by a first antibody which is immobilized on
a solid support, and thereafter a second antibody binds to the
analyte, thus forming an insoluble three-part complex. See, e.g.,
U.S. Pat No. 4,376,110. The second antibody may itself be labeled
with a detectable moiety (direct sandwich assays) or may be
measured using an anti-immunoglobulin antibody that is labeled with
a detectable moiety (indirect sandwich assay). For example, one
type of sandwich assay is an ELISA assay, in which case the
detectable moiety is an enzyme.
[0218] C. Humanized Antibodies
[0219] Methods for humanizing non-human antibodies are well known
in the art. Generally, a humanized antibody has one or more amino
acid residues introduced into it from a source which is non-human.
These non-human amino acid residues are often referred to as
"import" residues, which are typically taken from an "import"
variable domain. Humanization can be essentially performed
following the method of Winter and co-workers (Jones et al.,
Nature, 321:522-525 [1986]; Riechmann et al., Nature, 332:323-327
[1988]; Verhoeyen et al., Science, 239:1534-1536 [1988]), by
substituting rodent CDRs or CDR sequences for the corresponding
sequences of a human antibody. Accordingly, such "humanized"
antibodies are chimeric antibodies (U.S. Pat. No. 4,816,567,
supra), wherein substantially less than an intact human variable
domain has been substituted by the corresponding sequence from a
non-human species. In practice, humanized antibodies are typically
human antibodies in which some CDR residues, and possibly some FR
residues, are substituted by residues from analogous sites in
rodent antibodies.
[0220] It is important that antibodies be humanized with retention
of high affinity for the antigen and other favorable biological
properties. To achieve this goal, according to a preferred method,
humanized antibodies are prepared by a process of analysis of the
parental sequences and various conceptual humanized products using
three-dimensional models of the parental and humanized sequences.
Three-dimensional immunoglobulin models are familiar to those
skilled in the art. Computer programs are available which
illustrate and display probable three-dimensional conformational
structures of selected candidate immunoglobulin sequences.
Inspection of these displays permits analysis of the likely role of
the residues in the functioning of the candidate immunoglobulin
sequence, i.e., the analysis of residues that influence the ability
of the candidate immunoglobulin to bind its antigen. In this way,
FR residues can be selected and combined from the consensus and
import sequence so that the desired antibody characteristic, such
as increased affinity for the target antigen(s), is achieved. In
general, the CDR residues are directly and most substantially
involved in influencing antigen binding. For further details see WO
92/22653, published 23 Dec. 1992.
[0221] D. Bispecific Antibodies
[0222] Bispecific antibodies are monoclonal, preferably human or
humanized, antibodies that have binding specificities for at least
two different antigens. In the present case, one of the binding
specificities is for the VRP, the other one is for any other
antigen, and preferably for a receptor or receptor subunit. For
example, bispecific antibodies specifically binding the Flt4
receptor and the VRP are within the scope of the present
invention.
[0223] Methods for making bispecific antibodies are known in the
art. Traditionally, the recombinant production of bispecific
antibodies is based on the co-expression of two immunoglobulin
heavy-chain/light-chain pairs, where the two heavy chains have
different specificities. Millstein and Cuello, Nature 305:537-539
(1983). Because of the random assortment of immunoglobulin heavy
and light chains, these hybridomas (quadromas) produce a potential
mixture of ten different antibody molecules, of which only one has
the correct bispecific structure. The purification of the correct
molecule, which is usually done by affinity chromatography steps,
is rather cumbersome, and the product yields are low. Similar
procedures are disclosed in WO 93/08829, published 13 May 1993, and
in Traunecker et al., EMBO J., 10:3655-3659 (1991).
[0224] According to a different and more preferred approach,
antibody variable domains with the desired binding specificities
(antibody-antigen combining sites) are fused to immunoglobulin
constant domain sequences. The fusion preferably is with an
immunoglobulin heavy-chain constant domain, comprising at least
part of the hinge, CH2, and CH3 regions. It is preferred to have
the first heavy-chain constant region (CH1) containing the site
necessary for light-chain binding present in at least one of the
fusions. DNAs encoding the immunoglobulin heavy-chain fusions and,
if desired, the immunoglobulin light chain, are inserted into
separate expression vectors, and are co-transfected into a suitable
host organism. This provides for great flexibility in adjusting the
mutual proportions of the three polypeptide fragments in
embodiments when unequal ratios of the three polypeptide chains
used in the construction provide the optimum yields. It is,
however, possible to insert the coding sequences for two or all
three polypeptide chains in one expression vector when the
expression of at least two polypeptide chains in equal ratios
results in high yields or when the ratios are of no particular
significance. In a preferred embodiment of this approach, the
bispecific antibodies are composed of a hybrid immunoglobulin heavy
chain with a first binding specificity in one arm, and a hybrid
immunoglobulin heavy-chain/light-chain pair (providing a second
binding specificity) in the other arm. It was found that this
asymmetric structure facilitates the separation of the desired
bispecific compound from unwanted immunoglobulin chain
combinations, as the presence of an immunoglobulin light chain in
only one half of the bispecific molecule provides for a facile way
of separation. This approach is disclosed in WO 94/04690 published
3 Mar. 1994. For further details of generating bispecific
antibodies see, for example, Suresh et al., Methods in Enzymology,
121:210 (1986).
[0225] E. Heteroconjugate Antibodies
[0226] Heteroconjugate antibodies are also within the scope of the
present invention. Heteroconjugate antibodies are composed of two
covalently joined antibodies. Such antibodies have, for example,
been proposed to target immune system cells to unwanted cells (U.S.
Pat. No. 4,676,980), and for treatment of HIV infection. WO
91/00360; WO 92/200373; EP 03089. Heteroconjugate antibodies may be
made using any convenient cross-linking methods. Suitable
cross-linking agents are well known in the art, and are disclosed,
for example, in U.S. Pat. No. 4,676,980, along with a number of
cross-linking techniques.
[0227] 5. Uses of VRP Antibodies
[0228] i. Therapeutic Uses
[0229] VRP antibodies may be useful in certain therapeutic
indications to block activity of the VRP (for example, to block
excess activation or inhibition of the Flt4 receptor or another
receptor that binds to VRP, and to block neovascularization,
re-endothelialization, and angiogenesis). Specifically, the VRP
antibodies are useful in the treatment of various neoplastic and
non-neoplastic diseases and disorders. Neoplasms and related
conditions that are amenable to treatment include breast
carcinomas, lung carcinomas, gastric carcinomas, esophageal
carcinomas, colorectal carcinomas, liver carcinomas, ovarian
carcinomas, thecomas, arrhenoblastomas, cervical carcinomas,
endometrial carcinoma, endometrial hyperplasia, endometriosis,
fibrosarcomas, choriocarcinoma, head and neck cancer,
nasopharyngeal carcinoma, laryngeal carcinomas, hepatoblastoma,
Kaposi's sarcoma, melanoma, skin carcinomas, hemangioma, cavernous
hemangioma, hemangioblastoma, pancreas carcinomas, retinoblastoma,
astrocytoma, glioblastoma, Schwannoma, oligodendroglioma,
medulloblastoma, neuroblastomas, rhabdomyosarcoma, osteogenic
sarcoma, leiomyosarcomas, urinary tract carcinomas, thyroid
carcinomas, Wilm's tumor, renal cell carcinoma, prostate carcinoma,
abnormal vascular proliferation associated with phakomatoses, edema
(such as that associated with brain tumors), and Meigs'
syndrome.
[0230] Non-neoplastic conditions that are amenable to treatment
include rheumatoid arthritis, psoriasis, atherosclerosis, diabetic
and other retinopathies, retrolental fibroplasia, neovascular
glaucoma, age-related macular degeneration, thyroid hyperplasias
(including Grave's disease), corneal and other tissue
transplantation, chronic inflammation, lung inflammation, nephrotic
syndrome, preeclampsia, ascites, pericardial effusion (such as that
associated with pericarditis), and pleural effusion.
[0231] Age-related macular degeneration (AMD) is a leading cause of
severe visual loss in the elderly population. The exudative form of
AMD is characterized by choroidal neovascularization and retinal
pigment epithelial cell detachment. Because choroidal
neovascularization is associated with a dramatic worsening in
prognosis, the VRP antibodies of the present invention are expected
to be especially useful in reducing the severity of AMD.
[0232] For therapeutic applications, the VRP antibodies of the
invention are administered to a mammal, preferably a human, in a
pharmaceutically acceptable dosage form, including those that may
be administered to a human intravenously as a bolus or by
continuous infusion over a period of time, by intramuscular,
intraperitoneal, intra-cerobrospinal, subcutaneous,
intra-articular, intrasynovial, intrathecal, oral, topical, or
inhalation routes. The VRP antibodies also are suitably
administered by intratumoral, peritumoral, intralesional, or
perilesional routes or to the lymph, to exert local as well as
systemic therapeutic effects. The intraperitoneal route is expected
to be particularly useful, for example, in the treatment of ovarian
tumors.
[0233] Such dosage forms encompass pharmaceutically acceptable
carriers that are inherently non-toxic and non-therapeutic.
Examples of such carriers include ion exchangers, alumina, aluminum
stearate, lecithin, serum proteins, such as human serum albumin,
buffer substances such as phosphates, glycine, sorbic acid,
potassium sorbate, partial glyceride mixtures of saturated
vegetable fatty acids, water, salts, or electrolytes such as
protamine sulfate, disodium hydrogen phosphate, potassium hydrogen
phosphate, sodium chloride, zinc salts, colloidal silica, magnesium
trisilicate, polyvinyl pyrrolidone, cellulose-based substances, and
PEG. Carriers for topical or gel-based forms of VRP antibodies
include polysaccharides such as sodium carboxymethylcellulose or
methylcellulose, polyvinylpyrrolidone, polyacrylates,
polyoxyethylene-polyoxypropylene-block polymers, PEG, and wood wax
alcohols. For all administrations, conventional depot forms are
suitably used. Such forms include, for example, microcapsules,
nano-capsules, liposomes, plasters, inhalation forms, nose sprays,
sublingual tablets, and sustained-release preparations. The VRP
antibody will typically be formulated in such vehicles at a
concentration of about 0.1 mg/ml to 100 mg/ml.
[0234] Suitable examples of sustained-release preparations include
semipermeable matrices of solid hydrophobic polymers containing the
VRP antibody, which matrices are in the form of shaped articles,
e.g. films, or microcapsules. Examples of sustained-release
matrices include polyesters, hydrogels (for example,
poly(2-hydroxyethyl-methacrylate) as described by Langer et al.,
supra and Langer, supra, or poly(vinylalcohol), polylactides (U.S.
Pat. No. 3,773,919), copolymers of L-glutamic acid and gamma
ethyl-L-glutamate (Sidman et al., supra), non-degradable
ethylene-vinyl acetate (Langer et al., supra), degradable lactic
acid-glycolic acid copolymers such as the Lupron Depot.TM.
(injectable micropheres composed of lactic acid-glycolic acid
copolymer and leuprolide acetate), and poly-D-(-)-3-hydroxybutyric
acid. While polymers such as ethylene-vinyl acetate and lactic
acid-glycolic acid enable release of molecules for over 100 days,
certain hydrogels release proteins for shorter time periods. When
encapsulated VRP antibodies remain in the body for a long time,
they may denature or aggregate as a result of exposure to moisture
at 37.degree. C., resulting in a loss of biological activity and
possible changes in immunogenicity. Rational strategies can be
devised for stabilization depending on the mechanism involved. For
example, if the aggregation mechanism is discovered to be
intermolecular S--S bond formation through thio-disulfide
interchange, stabilization may be achieved by modifying sulfhydryl
residues, lyophilizing from acidic solutions, controlling moisture
content, using appropriate additives, and developing specific
polymer matrix compositions.
[0235] Sustained-release VRP antibody compositions also include
liposomally entrapped antibodies. Liposomes containing the VRP
antibodies are prepared by methods known in the art, such as
described in Epstein et al., Proc. Natl. Acad. Sci. USA, 82:3688
(1985); Hwang et al., Proc. Natl. Acad. Sci. USA, 77:4030 (1980);
and U.S. Pat. Nos. 4,485,045 and 4,544,545. Ordinarily, the
liposomes are the small (about 200-800 Angstroms) unilamelar type
in which the lipid content is greater than about 30 mol. %
cholesterol, the selected proportion being adjusted for the optimal
VRP antibody therapy. Liposomes with enhanced circulation time are
disclosed in U.S. Pat. No. 5,013,556.
[0236] Another use of the present invention comprises incorporating
VRP antibodies into formed articles. Such articles can be used in
modulating endothelial cell growth and angiogenesis. In addition,
tumor invasion and metastasis may be modulated with these
articles.
[0237] For the prevention or treatment of disease, the appropriate
dosage of VRP antibody will depend on the type of disease to be
treated, as defined above, the severity and course of the disease,
whether the antibodies are administered for preventive or
therapeutic purposes, previous therapy, the patient's clinical
history and response to the VRP antibody, and the discretion of the
attending physician. The VRP antibody is suitably administered to
the patient at one time or over a series of treatments.
[0238] Depending on the type and severity of the disease, about 1
.mu.g/kg to 15 mg/kg of VRP antibody is an initial candidate dosage
for administration to the patient, whether, for example, by one or
more separate administrations, or by continuous infusion. A typical
daily dosage might range from about 1 .mu.g/kg to 100 mg/kg or
more, depending on the factors mentioned above. For repeated
administrations over several days or longer, depending on the
condition, the treatment is sustained until a desired suppression
of disease symptoms occurs. However, other dosage regimens may be
useful. The progress of this therapy is easily monitored by
conventional techniques and assays, including, for example,
radiographic tumor imaging.
[0239] According to another embodiment of the invention, the
effectiveness of the VRP antibody in preventing or treating disease
may be improved by administering the VRP antibody serially or in
combination with another proteinaceous agent that is effective for
those purposes, such as those enumerated below, or one or more
conventional therapeutic agents such as, for example, alkylating
agents, folic acid antagonists, anti-metabolites of nucleic acid
metabolism, antibiotics, pyrimidine analogs, 5-fluorouracil,
cisplatin, purine nucleosides, amines, amino acids, triazol
nucleosides, or corticosteroids. Such other agents may be present
in the composition being administered or may be administered
separately. Also, the VRP antibody is suitably administered
serially or in combination with radiological treatments, whether
involving irradiation or administration of radioactive
substances.
[0240] In one embodiment, vascularization of tumors is attacked in
combination therapy. One or more VRP antibodies are administered to
tumor-bearing patients at therapeutically effective doses as
determined, for example, by observing necrosis of the tumor or its
metastatic foci, if any. This therapy is continued until such time
as no further beneficial effect is observed or clinical examination
shows no trace of the tumor or any metastatic foci. Then the
proteinaceous auxiliary agent is administered, alone or in
combination with another auxiliary agent. Such agents include,
e.g., TNF, an antibody capable of inhibiting or neutralizing the
angiogenic activity of aFGF or bFGF or hepatocyte growth factor
(HGF), an rhVEGF antagonist as described in WO 94/10202, supra,
alpha-, beta-, or gamma-interferon, anti-HER2 antibody, heregulin,
anti-heregulin antibody, D-factor, interleukin-1 (IL-1),
interleukin-2 (IL-2), GM-CSF, or agents that promote microvascular
coagulation in tumors, such as anti-protein C antibody,
anti-protein S antibody, or C4b binding protein (WO 91/01753
published 21 Feb. 1991), or heat or radiation.
[0241] Since the auxiliary agents will vary in their effectiveness
it is desirable to compare their impact on the tumor by matrix
screening in conventional fashion. The administration of VRP
antibody and TNF and/or other auxiliary agent is repeated until the
desired clinical effect is achieved. Alternatively, the VRP
antibody or antibodies are administered together with TNF and,
optionally, other auxiliary agent(s). In instances where solid
tumors are found in the limbs or in other locations susceptible to
isolation from the general circulation, the therapeutic agents
described herein are administered to the isolated tumor or organ.
In other embodiments, a FGF or platelet-derived growth factor
(PDGF) antagonist, such as an anti-FGF or an anti-PDGF neutralizing
antibody, is administered to the patient in conjunction with the
VRP antibody. Treatment with VRP antibodies optimally may be
suspended during periods of wound healing or desirable
neovascularization.
[0242] ii. Other Uses
[0243] The VRP antibodies of the invention also are useful as
affinity purification agents. In this process, the antibodies
against VRP are immobilized on a suitable support, such a Sephadex
resin or filter paper, using methods well known in the art. The
immobilized antibody then is contacted with a sample containing the
VRP to be purified, and thereafter the support is washed with a
suitable solvent that will remove substantially all the material in
the sample except the VRP, which is bound to the immobilized
antibody. Finally, the support is washed with another suitable
solvent, such as glycine buffer, pH 5.0, that will release the VRP
from the antibody.
[0244] VRP antibodies may also be useful in diagnostic assays for
VRP, e.g., detecting its expression in specific cells, tissues, or
serum. The antibodies are labeled in the same fashion as VRP
described above and/or are immobilized on an insoluble matrix. VRP
antibodies also are useful for the affinity purification of VRP
from recombinant cell culture or natural sources. VRP antibodies
that do not detectably cross-react with other proteins can be used
to purify VRP free from these other known proteins. Suitable
diagnostic assays for VRP and its antibodies are described
above.
[0245] III. Experimental
[0246] Below are examples of specific embodiments for carrying out
the present invention. The examples are offered for illustrative
purposes only, and are not intended to limit the scope of the
present invention in any way.
[0247] All publications, patents and patent applications cited
herein, whether supra or infra, are hereby incorporated by
reference in their entirety.
EXAMPLE 1
Isolation of cDNA Clones Encoding Human Flt4 Receptor
[0248] cDNA synthesized from mRNA purified from the human
megakaryocyte leukemia cell line CMK11-5 was amplified with
redundant PCR primers based on the conserved regions of tyrosine
kinase receptors. Wilks, Proc. Natl. Acad. Sci. USA, 86: 1603-1607
(1989). One amplified fragment of about 180 bp with a unique DNA
sequence (designated SAL-S1 or tk1; PCT/US93/00586, supra) was used
to screen (Janssen et al., supra) cDNA libraries from CMK11-5 and
DAMI cells to obtain overlapping clones that encoded the
full-length short form of Flt4 receptor (1298 amino acids). The
sequence of the assembled Flt4-encoding clones matched that
reported from an anerythroleukemia cell line (Pajusola et al.,
Cancer Res., supra); it encodes 8 amino acid differences from
another reported Flt4 sequence. Galland et al., Oncogene, supra.
Clones encoding the long form of Flt4 (1363 amino acids) were
constructed by synthesizing the differing 3' DNA sequence of about
200 bp based on the published sequence. Pajusola et al., Oncogene,
8, supra.
EXAMPLE 2
Receptor IgG Fusion Proteins, Flt4/IgG Antiserum, and G61 FACS
Analysis
[0249] Flt1/IgG (Park et al., supra), Flk1/IgG (Park et al.,
supra), Rse/IgG (Godowski et al., Cell, 82: 355-358 [1995]), and
Htk/IgG (Bennett et al., J. Biol. Chem., 269: 14211-14218 [1994])
were produced as described in these references. For Flt4/IgG, DNA
encoding the extracellular domain of the Flt4 receptor (amino acids
1-775) was spliced to the Fc region of a human IgG heavy chain at
the unique BstEII site in the plasmid pBSSK-Fc (pBSSK-CH2CH3).
Bennett et al., J. Biol. Chem., 266: 23060-23067 (1991). The open
reading frame encoding Flt4/IgG was cloned in the mammalian
expression vector pRK5 (Suva et al., Science, 237: 893-896 [1987])
to yield the plasmid pRK5.tk1ig1.1. This plasmid was transfected by
electroporation (Janssen et al., supra) into 293 cells (ATCC CRL
1651), and after 3-4 days, Flt4/IgG was purified from the
serum-free conditioned medium with protein A agarose (Calbiochem).
Flt4 antiserum was generated by injection of purified Flt4/IgG into
rabbits.
[0250] By using this fusion protein to screen cell lines for
membrane-bound VRP by FACS analysis, one positive cell line was
identified, G61, described below.
[0251] The human glioma cell line, G61 (Hamel et al., J. Neurosci.
Res., 34: 147-157 [1993]), was cultured in F12:DMEM (50:50) (high
glucose) containing 10% fetal bovine serum, 2 mM L-glutamine, and
antibiotics. For FACS analysis of Flt4/IgG binding to G61 cells, 1
million cells were incubated with 70 nM receptor-IgG fusion protein
in phosphate-buffered saline (PBS), 5% goat serum, 2% rabbit serum
for 60 min. at 4.degree. C. and then stained with 10 .mu.g/mL
biotin-SP-conjugated goat anti-human Fc antibody and 10 .mu.g/mL
R-phycoerythrin-conjugated streptavidin (Jackson Immuno Research).
G61 caused about a 10-fold shift in peak fluorescence intensity
that was specific for Flt4/IgG as compared to Rse/IgG, an unrelated
tyrosine kinase receptor complex (FIG. 2). Attempts to expression
clone this putative membrane-bound VRP by the transfection of pools
of cDNA clones into COS cells followed by screening with labeled
Flt4/IgG yielded no positives from 640 pools of 1000-5000 clones
each.
EXAMPLE 3
Isolation of cDNA Clones Encoding Human VRP
[0252] A cDNA library was prepared from polyA+RNA isolated as
described in Cathala et al., DNA: 2: 329-335 (1983) and Aviv and
Leder, Proc. Natl. Acad. Sci. USA, 69: 1408-1412 (1972) from the
human glioma cell line, G61. Hamel et al., supra. cDNA was prepared
from this RNA with reagents from GIBCO/BRL (SuperScript) and cloned
in the plasmid pRK5B (Holmes et al., Science, 253: 1278-1280
[1991]) digested with XhoI and NotI. Clones encoding VRP were
isolated by screening the cDNA library with synthetic
oligonucleotide probes based on an EST sequence (GenBank locus
HSC1WF111), which showed a reasonable match to VEGF. The EST
sequence of HSC1WF111 is 299 bp and is 36% identical to VEGF over
50 residues, including an 11 of 13 residue match beginning at VEGF
amino acid 56. The sequence is as follows:
1 5'- (SEQ ID NO: 6) CCGTCTACAGATGTGGGGGTTGCTGCAA-
TAGTGAGGGGCTGCAGTGCATG AACACCAGCACGAGCTACCTCAGNAAGACGTTATT-
TGAAATTACAGTGCC TCTCTCTCAAGGCCCCAAACCAGTAACAATCAGTTTTGCCAA-
TCACACTT CCTGCCGATGCATGTCTAAACTGGATGTTTACAGACAAGTTCATTCCAT- T
ATTAGACGTTCCCTGCCAGCAACACTACCACAGTGTCAGGCAGCGAACAA
GACCTGCCCCACCAATTACATGTGGAATAATCACATCTGCAGATGCCTG.
[0253] The sequences of the oligonucleotide probes ovh1.4 and
ovh1.5 employed are indicated below.
2 ovh1.4: 5'- CTGGTGTTCATGCACTGCAGCCCCTCACTATTGCA (SEQ ID NO: 7)
GCAACCCCCACATCT ovh1.5: 5'- GCATCTGCAGATGTGATTATTCCACATGTAATTGG
(SEQ ID NO: 8) TGGGGCAGGTCTTGT
[0254] These two probes were .sup.32P labeled and hybridized in 20%
formamide at 42.degree. C. with a final wash in 30 mM NaCl/3 mM
trisodium citrate at 55.degree. C. Janssen, Current Protocols in
Molecular Biology, John Wiley & Sons (1995). Seven positives
were identified and characterized from 650,000 clones screened. The
positives fell into three groups by restriction mapping and DNA
sequencing.
[0255] Clones VH1.4 (pRK.vh1.4.1) and VH1.6 included the full
coding region (FIG. 3A) and were sequenced completely. They differ
only in length and the lack of two T's preceeding the 3' poly A
sequence in VH1.6. Clone VH1.2 is collinear with VH1.4. Clones
VH1.3, VH1.5, and VH1.7 are identical and have a 557 bp deletion
when compared with VH1.4 (a deletion of bp 519-1075), and clone
VH1.1 has a 152 bp deletion when compared with VH1.4 (a deletion of
bp 924-1075). The nucleotide and deduced amino acid sequences of
VH1.4 are shown in FIG. 1.
[0256] The sequence contained an open reading frame of 419 amino
acids beginning with an ATG codon preceded by a purine residue at
position -3 as expected for a translation initiation site. Kozak,
Nucl. Acids Res., 12: 857-872 (1984). About 250 bp 5' of this ATG
are two in-frame ATG codons followed shortly (4 or 10 amino acids)
by a stop codon. Both of these ATG's have a pyrimidine at position
-3 and would not be expected to function as a strong translation
initiation site. Kozak, supra. The encoded amino acid sequence
imediately following the start of the 419 amino acid reading frame
is hydrophobic, indicative of an amino-terminal secretion signal
sequence. Perlman and Halvorson, J. Mol. Biol., 167: 391-409
(1983). See FIG. 3A. The most likely cleavage site for this
sequence would be after amino acid 20, although cleavage following
residues 15 or 16 cannot be excluded. von Heijne, Nucl. Acids Res.,
14: 4683-4690 (1986). The open reading frame is preceded by a
GC-rich 5' untranslated region of about 380 bp and followed by a 3'
untranslated region of about 400 bp.
[0257] The predicted mature amino acid sequence of human VRP
contains 399 amino acid residues (translated M.sub.r=44.8 kDa), of
which 37 (9.3%) are cysteine residues; there are three potential
N-linked glycosylation sites (FIG. 3A). An alignment of the amino
acid sequence of VRP with the six forms of VEGF and PlGF shows that
it is most similar to VEGF.sub.121 (32% identical) and PIGF.sub.131
(27% identical) (FIG. 3B); the locations of 8 of the 9 cysteine
residues are conserved. While VRP does not contain the regions of
basic amino acids found in some forms of VEGF and PlGF, it is
considerably larger than VEGF and contains a cysteine-rich
C-terminal half of the molecule that is not found in VEGF. This
cysteine-rich domain has four copies of the pattern Cys followed by
ten non-Cys residues followed by Cys-X followed by Cys-X and then
by Cys (FIG. 3B), a repeat found more than 50 times in a diptran
Balbiani ring 3 protein. Paulsson et al., J. Mol. Biol., 211:
331-349 (1990). Without being limited to any one theory, VRP may
interact with other membrane-bound proteins on these cells via the
cysteine residues; such an intermolecular interaction has been
proposed for the Balbiani protein. Paulsson et al., supra.
[0258] Two of the cDNA clones (VH1.1 and VH1.3) contained a 152 or
557 bp deletion when compared with VH1.4 (FIG. 3A). Both these
deletions end at the same nucleotide and are presumed to be the
result of alternative splicing. Both deletions would be expected to
encode the same frame-shifted protein 3' of the deletion which
terminates at a stop codon within 15 amino acids. The protein
encoded by VH1.3 would include none of the core cysteine region
similar with VEGF. VH1.1 contains much of the region that is
similar to VEGF; its deletion, however, is not analogous to the
various known forms of VEGF or PlGF. Ferrara et al., supra;
Maglione et al., supra; Hauser and Weich, supra.
[0259] FIG. 4 discloses an alignment of VH1.4 (top) with 11 EST
cDNA sequences from GenBank. It is noted that the 3' EST's are at
the polyA end and that the EST's cover only a little more than half
of the full-length sequence of VH1.4.
EXAMPLE 4
Receptor IgG Precipitation of .sup.35S-Labeled VRP
[0260] To determine whether VRP is a ligand for Flt4, expression
plasmids containing the VH1.4 cDNA clone, as well as control
plasmids (the expression vector alone or with VEGF or PlGF DNA),
were transfected into COS7 cells and the proteins labeled with
.sup.35S amino acids. Conditioned media from these cells was
precipatated with Flt4/IgG and Flk1/IgG. Specifically, the VRP
expression plasmid, pRK.vh1.4.2, was constructed by deleting about
360 bp of 5' untranslated sequence (5' of the AgeI site (FIG. 3A)
from VH1.4). This DNA and control plasmids encoding VEGF.sub.165
(Houck et al., Mol. Endocrinol., 5: 1806-1814 [1991]), PlGF.sub.152
(Park et al., supra), or the vector alone (pRK5; Suva et al.,
supra) were transfected into COS7 cells with DEAE-dextran. Janssen
et al., supra. Two days after transfection, the cells were
pulse-labeled in 10-cm dishes for 5 hours with 5 mL of methionine-
and cysteine-free DMEM supplemented with 100 .mu.Ci/mL of 35S amino
acids (Pro-Mix.TM. brand; Amersham #SJQ0079) at 37.degree. C., and
then chased with DMEM for 7 hours. The labeled conditioned medium
was concentrated 10-fold by spin concentration (Centricon-10.TM.
brand; Amicon #4203). Fifty .mu.L of the concentrated medium was
incubated with 3 .mu.g of receptor IgG and 80 .mu.L of a 50% slurry
of protein A agarose (Calbiochem) overnight at 4.degree. C. The
precipitates were washed with PBS/0.1% Triton X-100, boiled in SDS
sample buffer, and electrophoresed on 12% SDS polyacrylamide gels
(Novex #EC60052). The gels were treated with autoradiography
enhancer (duPont #NEF974) and exposed overnight at -70.degree.
C.
[0261] Two specific bands of 53 kDa and 33 kDa were precipitated
from the VRP transfection by the Flt4/IgG; these bands were absent
in the vector transfection. Little or no specific precipitation of
these two bands was found with Flt1/IgG or Flk1/IgG. At times, some
VRP precipitation was detected with Flk1/IgG, suggesting that VRP
may have a low-affinity interaction with Flk1. Transfection with a
VEGF-expressing plasmid showed the expected precipitation of a
strong band of about 22 kDa with Flt1/IgG and Flk1/IgG (DeVries et
al., supra; Quinn et al., supra; Millauer et al., supra; Terman et
al., Biochem. Biophys. Res. Commun., supra), but no precipitation
with Flt4/IgG. Similar experiments with labeled PlGF showed no
precipitation by Flt4/IgG, but did give the expected precipitation
by Flt1/IgG, but not by Flk1/IgG. Park et al., supra. These data
indicate that the VRP binds to the extracellular domain of the Flt4
receptor, but does not interact (or does so much more weakly) with
the VEGF receptors Flt1 or Flk1. They also confirm the lack of an
interaction of VEGF with Flt4 (Pajusola et al., Oncogene, 9, supra)
and indicate that PlGF is also not a ligand for this receptor.
EXAMPLE 5
Tyrosine Phosphorylation of Flt4 Receptor
[0262] To assay Flt4 tyrosine phosphorylation (also described in
PCT/US93/00586, supra), Flt4 was expressed in 293 cells and Flt4
phosphorylation monitored by phosphotyrosine immunoblot.
Specifically, DNA encoding the long form of human Flt4 was cloned
into the mammalian expression vector pRK5 (Suva et al., supra) to
give the plasmid pRK.tk1-3.1. This plasmid was co-transfected with
a plasmid containing a miroglycoside phosphotransferase (neo)
transcription unit into 293 cells by calcium phosphate
precipitation (Janssen et al., supra), and stably transfected lines
were selected by growth on G418 (Gibco). One clonal cell line
expressing Flt4 (clone 31), as determined by FACS analysis with
Flt4/IgG antiserum, and untransfected 293 cells were used in the
Flt4 tyrosine phosphorylation assays. One million cells in 100
.mu.L of PBS/0.1% bovine serum albumin (BSA) were mixed with 100
.mu.L of sample and incubated at 37.degree. C. for 15 minutes. The
cells were then collected by centrifugation and lysed in 250 .mu.L
of 0.15 M NaCl, 10% glycerol, 1% Triton X-100, 50 mM HEPES pH 7.3,
4 .mu.g/mL PMSF, 0.02 u/mL aprotinin (Sigma A6279), and 20 mM
sodium orthovanadate. Flt4 was immunoprecipitated by the addition
of 8 .mu.L of rabbit Flt4/IgG antiserum and 30 .mu.L of protein A
agarose. Washed precipitates were boiled in SDS sample buffer,
electrophoresed on polyacrylamide gels (Novex), transferred to
nitrocellulose (Janssen et al., supra), and probed with an
anti-phosphotyrosine monoclonal antibody (Upstate Biotechnology)
and an alkaline phosphatase detection system (Promega).
[0263] Samples containing VRP or VEGF were prepared by the
electroporation of expression plasmids encoding VH1.4 (pRK.vh1.4.2)
or VEGF (Houck et al., supra) into 293 cells and 20-fold
concentration (Centricon-10, Amicon) of the 3-day serum-free
conditioned medium. In the receptor IgG competition experiments,
the concentrated conditioned media were pre-incubated 1 hour at
4.degree. C. with receptor IgG.
[0264] Without stimulation, 293 cells expressing or not expressing
Flt4 showed little or no Flt4 tyrosine phosphorylation. Stimulation
of the Flt4-expressing cells by Flt4/IgG antiserum showed the
tyrosine phosphorylation of two bands of 180 and 120 kDa. No
increase above basal phosphorylation was observed with preimmune
serum, and no bands were found with Flt4/IgG antiserum stimulation
of non-expressing cells. Two Flt4 bands of about this size have
been reported as being expressed by DAMI and HEL cells. Pajusola et
al., Oncogene, 8, supra. In addition, SDS gel analysis of purified
Flt4/IgG shows that it is composed of peptides of 150, 80, and 70
kDa. N-terminal amino acid sequence of the Flt4/IG peptides shows
that the 150 and 70 kDa bands have the amino acid sequence YSMTPPTL
(SEQ ID NO: 9) (matching the Flt4 sequence starting at residue 25)
and that the 80 kDa band has the sequence SLRRRQQQD (SEQ ID NO: 10)
(matching the Flt4 sequence beginning at residue 473). Thus, both
the Flt4/IgG and full-length Flt4 appear to be partially cleaved in
the extracellular domain, and the tyrosine phosphorylated bands of
180 and 120 kDa observed in the Flt4 phosphorylation assays would
correspond to the 150 and 80 kDa peptides of Flt4/IgG. Addition of
a polyclonal antiserum to the Flt4 expressing cells showed the
tyrosine phosphorylation of two Flt4 bands of 180 and 120 kDa; no
bands were observed in non-expressing cells. These data show that
polyclonal antibodies generated to the extracellular domain of the
Flt4 receptor are capable of activating Flt4 tyrosine
phosphorylation.
[0265] To determine whether VRP could activate the tyrosine
phosphorylation of Flt4, conditioned media from mammalian cells
transfected with the VRP expression plasmid was assayed. This
conditioned medium stimulated the tyrosine phosphorylation of the
same 180 and 120 kDa bands found with the agonist polyclonal
antibodies, demonstrating that VRP is able to stimulate the
phosphorylation of, as well as bind to, Flt4. Conditioned medium
from VEGF-expressing cells failed to activate Flt4 tyrosine
phosphorylation.
[0266] To confirm the specificity of VRP binding to the receptors
of the VEGF family, Flt4/IgG, Flt1/IgG, Flk1/IgG, and Htk/IgG were
tested for their ability to compete for VRP-stimulated Flt4
phosphorylation. As expected if VRP is a ligand for Flt4, Flt4/IgG
prevented the VRP-stimulated phosphorylation, while Flt1/IgG,
Flk1/IgG, and Htk/IgG, a fusion protein from an unrelated tyrosine
kinase receptor, had little or no effect. These data show that VRP
is able to induce the tyrosine phosphorylation of Flt4.
EXAMPLE 6
Purification of VRP and Binding to Labeled Flt4/IgG
[0267] The reading frame encoding the N-terminal secretion signal
sequence and about 30 amino acids of the herpes glycoprotein D
(Lasky and Dowbenko, DNA, 3: 23-29 [1984]); Pennica et al., Proc.
Natl. Acad. Sci. USA, 92: 1142-1146 [1995]) were fused with a short
linker sequence to the putative mature sequence of VRP. Following
secretion from mammalian cells, this construct is expected to give
the N-terminal glycoprotein D sequence:
[0268] KYALADASLKMADPNRFRGKDLPVLDQLLEGGAAHYALLP (SEQ ID NO: 11)
followed by the mature VRP sequence GPREAPAAAAAFE (SEQ ID NO: 12).
DNA encoding this fusion protein was cloned into the vector pRK5 to
give the plasmid pRK.vh1.4.5. This plasmid was transfected into 293
cells by electroporation (Janssen et al., supra), and VRP purified
from the 3-4 day serum-free conditioned medium by monoclonal
antibody (5B6) affinity chromatography and quantitated by
colorimetric assay (Bio-Rad). This antibody is specific for the
glycoprotein D sequence fused to the N-terminus of VRP.
[0269] Flt4/IgG was iodinated to a specific activity of 1000-1500
Ci/mmol with Iodobeads.TM. brand iodinated beads (Pierce). Binding
was performed with .about.20,000 cpm .sup.125I-Flt4/IgG and 12 ng
VH1.4 gD fusion protein in PBS, 0.5% BSA, 0.02% Tween-20.TM.
surfactant, 1 .mu.g/nL heparin (binding buffer) containing 20 .mu.L
of a 50% slurry of glass beads conjugated to .about.30 .mu.g
anti-gD monoclonal antibody (5B6) in a final volume of 100 .mu.L
for 4-6 hours at 22.degree. C. Beads were collected by filtration
(Millipore Multiscreen-HV), washed five times with 200 .mu.L
binding buffer, and counted. For binding at increasing
concentrations of Flt4/IgG (FIG. 5B) the binding buffer was DMEM
(low glucose):F12 (50:50), 20 mM sodium HEPES, pH 7.2, 10% fetal
bovine serum, 0.2% gelatin, and 1 .mu.g/mL heparin.
[0270] The purified VRP specifically bound to .sup.125I-Flt4/IgG,
and the binding was not competed by unlabeled Flt1/IgG or Flk1/IgG
(FIG. 5A). Binding competition with increasing concentrations of
unlabeled Flt4/IgG (FIG. 5B) gave an EC.sub.50 for this interaction
of .about.0.7 nM, suggesting that the binding of VRP to Flt4 is of
high affinity as would be expected if VRP is a biologically
relevant ligand for Flt4.
[0271] RNA Blots
[0272] Blots containing poly(A)+ human RNA were from Clontech. For
the G61 glioma cell line, 5 .mu.g of poly(A)+ and poly(A)- RNA were
electrophoresed on a 1% agarose/2.2 M formaldehyde gel and
transferred to nitrocellulose (Janssen et al., supra). Blots were
hybridized with .sup.32P-labeled probes ovh1.4 and ovh1.5 and
washed in 30 mM NaCl/3 mM trisodium citrate at 55.degree. C.
[0273] The G61 glioma cell line used in the cloning of VRP
expresses a major VRP RNA band of about 2.4 kb. A minor band of
about 2.2 kb may also be present. A 2.4 kb band was expressed in
adult human tissues from heart, placenta, ovary, and small
intestine; a weaker band was found in lung, skeletal muscle,
spleen, prostrate, testis, and colon. Expression of a 2.4 kb mRNA
was also found in fetal lung and kidney.
EXAMPLE 7
Mitogenic Activity of VRP
[0274] To test whether VRP has mitogenic activity like that found
for VEGF, the growth of human lung endothelial cells was determined
at increasing concentrations of VRP or VEGF (FIG. 6). Specifically,
human lung microvascular endothelial cells (HMVEC-L, Clonetics, San
Diego, Calif.) were maintained in the recommended growth medium
(EGM-MV with 5% fetal calf serum). For the assay of mitogenesis,
low passage (<6) cells were seeded at 6500 cells/well in 48-well
plates (Costar) and maintained overnightin the recommended growth
medium. The medium was removed, and the cells were maintained in
the growth medium (2% fetal calf serum) without bovine brain
extract and supplemented with VEGF or VRP. After four days, the
cells were removed with trypsin and counted with a Coulter counter
(Hialeah, Fla.).
[0275] VRP promoted the growth of these endothelial cells (see FIG.
6), and thus shares this mitogenic activity with VEGF. This is in
contrast to PlGF, which has been reported to lack such mitogenic
activity (at .ltoreq.35 nM). Park et al., supra. While an effective
mitogenic agent, VRP was about 100 fold less potent than VEGF in
this assay.
[0276] In conclusion, a novel secreted protein, VRP, has now been
identified that is a Flt4 ligand and that stimulates the tyrosine
phosphorylation of the receptor tyrosine kinase Flt4. VRP is a
third member of the VEGF protein family and has about 30% amino
acid identity with VEGF and PlGF. In addition to the VEGF-like
domain, VRP contains a .about.180 amino acid C-terminal,
cysteine-rich domain not found in other members of the VEGF family.
VRP fails to interact appreciably with the VEGF receptors Flt1 and
Flk1.
[0277] Deposit of Material
[0278] The following plasmid has been deposited with the American
Type Culture Collection, 12301 Parklawn Drive, Rockville, Md., USA
(ATCC):
3 Plasmid ATCC Dep. No. Deposit Date pRK.vh1.4.1 97249 Sep. 6,
1995
[0279] This deposit was made under the provisions of the Budapest
Treaty on the International Recognition of the Deposit of
Microorganisms for the Purpose of Patent Procedure and the
Regulations thereunder (Budapest Treaty). This assures maintenance
of a viable culture of the deposit for 30 years from the date of
deposit. The deposit will be made available by ATCC under the terms
of the Budapest Treaty, and subject to an agreement between
Genentech, Inc. and ATCC, which assures permanent and unrestricted
availability of the progeny of the culture of the deposit to the
public upon issuance of the pertinent U.S. patent or upon laying
open to the public of any U.S. or foreign patent application,
whichever comes first, and assures availability of the progeny to
one determined by the U.S. Commissioner of Patents and Trademarks
to be entitled thereto according to 35 USC .sctn.122 and the
Commissioner's rules pursuant thereto (including 37 CFR .sctn.1.14
with particular reference to 886 OG 638).
[0280] The assignee of the present application has agreed that if a
culture of the plasmid on deposit should die or be lost or
destroyed when cultivated under suitable conditions, the plasmid
will be promptly replaced on notification with another of the same
plasmid. Availability of the deposited plasmid is not to be
construed as a license to practice the invention in contravention
of the rights granted under the authority of any government in
accordance with its patent laws.
[0281] The foregoing written specification is considered to be
sufficient to enable one skilled in the art to practice the
invention. The present invention is not to be limited in scope by
the construct deposited, since the deposited embodiment is intended
as a single illustration of certain aspects of the invention and
any constructs that are functionally equivalent are within the
scope of this invention. The deposit of material herein does not
constitute an admission that the written description herein
contained is inadequate to enable the practice of any aspect of the
invention, including the best mode thereof, nor is it to be
construed as limiting the scope of the claims to the specific
illustrations that it represents. Indeed, various modifications of
the invention in addition to those shown and described herein will
become apparent to those skilled in the art from the foregoing
description and fall within the scope of the appended claims.
Sequence CWU 1
1
* * * * *