U.S. patent application number 12/269369 was filed with the patent office on 2010-09-09 for human kunitz-type inhibitor with enhanced antifibrinolytic activity.
This patent application is currently assigned to STC.UNM. Invention is credited to Hitendra S. Chand, Walter Kisiel.
Application Number | 20100227808 12/269369 |
Document ID | / |
Family ID | 35996989 |
Filed Date | 2010-09-09 |
United States Patent
Application |
20100227808 |
Kind Code |
A1 |
Kisiel; Walter ; et
al. |
September 9, 2010 |
HUMAN KUNITZ-TYPE INHIBITOR WITH ENHANCED ANTIFIBRINOLYTIC
ACTIVITY
Abstract
A human Kunitz-type inhibitor polypeptide with enhanced
antifibrinolytic activity, methods of making, and methods of use.
The novel polypeptide is structurally similar to the KD1 domain of
human tissue factor pathway inhibitor-2 (TFPI-2).
Inventors: |
Kisiel; Walter;
(Albuquerque, NM) ; Chand; Hitendra S.;
(Albuquerque, NM) |
Correspondence
Address: |
MUETING, RAASCH & GEBHARDT, P.A.
P.O. BOX 581336
MINNEAPOLIS
MN
55458-1336
US
|
Assignee: |
STC.UNM
Albuquerque
NM
|
Family ID: |
35996989 |
Appl. No.: |
12/269369 |
Filed: |
November 12, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11107643 |
Apr 15, 2005 |
7432238 |
|
|
12269369 |
|
|
|
|
60563039 |
Apr 16, 2004 |
|
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Current U.S.
Class: |
514/20.1 ;
530/324 |
Current CPC
Class: |
A61P 11/06 20180101;
A61P 31/16 20180101; C07K 14/8114 20130101; A61K 38/00 20130101;
A61P 35/00 20180101 |
Class at
Publication: |
514/12 ;
530/324 |
International
Class: |
A61K 38/16 20060101
A61K038/16; C07K 14/435 20060101 C07K014/435; A61P 11/06 20060101
A61P011/06; A61P 35/00 20060101 A61P035/00; A61P 31/16 20060101
A61P031/16 |
Goverment Interests
STATEMENT OF GOVERNMENT RIGHTS
[0002] This invention was made with government support under a
grant from the National Institutes of Health, Grant No. 1 RO1
HL64119. The U.S. Government has certain rights in this invention.
Claims
1-51. (canceled)
52. A polypeptide comprising: a KD1 domain consisting of a primary
structure that is at least 86% identical to the primary structure
of the wild-type KD1 domain of human tissue factor pathway
inhibitor-2 (TFPI-2) (SEQ ID NO:2), or a biologically active
subunit thereof; wherein the polypeptide does not include a KD2 or
KD3 domain of human TFPI-2.
53. The polypeptide of claim 52 wherein the polypeptide includes a
lysine instead of arginine at position 24 as defined for the
wild-type KD1 amino acid sequence.
54. The polypeptide of claim 53 comprising SEQ ID NO:3.
55. The polypeptide of claim 52 wherein the biologically active
subunit of KD1 is characterized by a deletion of 1, 2, 3, 4, 5, 6,
7, 8, 9, or 10 amino acid residues at either or both of the
amino-terminal or carboxy-terminal end relative to the wild-type
KD1 sequence.
56. The polypeptide of claim 52 wherein the KD1 domain consists of
a primary structure that is at least 90% identical to the primary
structure of the wild-type KD1 domain of TFPI-2 (SEQ ID NO:2), or a
biologically active subunit thereof.
57. The polypeptide of claim 56 wherein the polypeptide includes a
lysine instead of arginine at position 24 as defined for the
wild-type KD1 amino acid sequence.
58. The polypeptide of claim 52 wherein the KD1 domain consists of
a primary structure that is at least 95% identical to the primary
structure of the wild-type KD1 domain of TFPI-2 (SEQ ID NO:2), or a
biologically active subunit thereof.
59. The polypeptide of claim 58 wherein the polypeptide includes a
lysine instead of arginine at position 24 as defined for the
wild-type KD1 amino acid sequence.
60. A polypeptide comprising: a KD1 domain consisting of a primary
structure that is at least 86% identical to the primary structure
of the wild-type KD1 domain of human tissue factor pathway
inhibitor-2 (TFPI-2) (SEQ ID NO:2), or a biologically active
subunit thereof, wherein the polypeptide does not include a KD2 or
KD3 domain of human TFPI-2; and a multiply positively charged amino
acid sequence disposed at either or both of the N-terminal or
C-terminal end of the polypeptide.
61. The polypeptide of claim 60 wherein the polypeptide includes a
lysine instead of arginine at position 24 as defined for the
wild-type KD1 amino acid sequence.
62. The polypeptide of claim 60 wherein the KD1 domain consists of
a primary structure that is at least 90% identical to the primary
structure of the wild-type KD1 domain of TFPI-2 (SEQ ID NO:2), or a
biologically active subunit thereof.
63. The polypeptide of claim 62 wherein the polypeptide includes a
lysine instead of arginine at position 24 as defined for the
wild-type KD1 amino acid sequence.
64. The polypeptide of claim 60 wherein the KD1 domain consists of
a primary structure that is at least 95% identical to the primary
structure of the wild-type KD1 domain of TFPI-2 (SEQ ID NO:2), or a
biologically active subunit thereof.
65. The polypeptide of claim 64 wherein the polypeptide includes a
lysine instead of arginine at position 24 as defined for the
wild-type KD1 amino acid sequence.
66. The polypeptide of claim 60 wherein the multiply positively
charged amino acid sequence comprises an amino acid sequence from
the C-terminus of wild-type TFPI-2.
67. The polypeptide of claim 66 wherein the multiply positively
charged amino acid sequence comprises amino acids 192 through 211
of SEQ ID NO:1.
68. A polypeptide comprising: a KD1 domain consisting of a primary
structure that is at least 86% identical to the primary structure
of the wild-type KD1 domain of human tissue factor pathway
inhibitor-2 (TFPI-2) (SEQ ID NO:2), or a biologically active
subunit thereof; and a multiply positively charged amino acid
sequence disposed at either or both of the N-terminal or C-terminal
end of the polypeptide.
69. The polypeptide of claim 68 wherein the KD1 domain comprises a
lysine at position 24 as defined for the wild-type KD1 amino acid
sequence.
70. The polypeptide of claim 68 wherein the KD1 domain consists of
a primary structure that is at least 90% identical to the primary
structure of a wild-type KD1 domain of human TFPI-2 (SEQ ID NO:2),
or a biologically active subunit thereof.
71. The polypeptide of claim 70 wherein the KD1 domain comprises a
lysine at position 24 as defined for the wild-type KD1 amino acid
sequence.
72. The polypeptide of claim 68 wherein the KD1 domain consists of
a primary structure that is at least 95% identical to the primary
structure of the wild-type KD1 domain of TFPI-2 (SEQ ID NO:2), or a
biologically active subunit thereof.
73. The polypeptide of claim 72 wherein the polypeptide includes a
lysine instead of arginine at position 24 as defined for the
wild-type KD1 amino acid sequence.
74. The polypeptide of claim 68 wherein the multiply positively
charged amino acid sequence comprises an amino acid sequence from
the C-terminus of wild-type TFPI-2.
75. The polypeptide of claim 74 wherein the multiply positively
charged amino acid sequence comprises amino acids 192 through 211
of SEQ ID NO:1.
76. A polypeptide comprising: a KD1 domain consisting of a primary
structure that is at least 86% identical to the primary structure
of the wild-type KD1 domain of human tissue factor pathway
inhibitor-2 (TFPI-2) (SEQ ID NO:2); wherein the polypeptide
includes a lysine instead of arginine at position 24 as defined for
the wild-type KD1 amino acid sequence.
77. A pharmaceutical composition comprising: the polypeptide of
claim 52; and a pharmaceutically acceptable carrier.
78. A pharmaceutical composition comprising: the polypeptide of
claim 60; and a pharmaceutically acceptable carrier.
79. A pharmaceutical composition comprising: the polypeptide of
claim 68; and a pharmaceutically acceptable carrier.
80. A pharmaceutical composition comprising: the polypeptide of
claim 76; and a pharmaceutically acceptable carrier.
Description
[0001] This application is a divisional patent application of U.S.
patent application Ser. No. 11/107,643, filed Apr. 15, 2005, now
U.S. Pat. No. 7,432,238, which claims the benefit of U.S.
Provisional Patent Application Ser. No. 60/563,039, filed Apr. 16,
2004, each of which is incorporated herein by reference in its
entirety. The present application is entitled to the benefit of
U.S. patent application Ser. No. 11/107,643 and U.S. Provisional
Patent Application Ser. No. 60/563,039 through co-pending U.S.
patent application Ser. No. 12/286,933, filed Oct. 3, 2008, which
is a continuation-in-part of U.S. patent application Ser. No.
11/107,643.
BACKGROUND OF THE INVENTION
[0003] Proteinase inhibitors play a critical role in the regulation
of several physiological processes such as blood coagulation,
complement fixation, fibrinolysis, and fertilization (Bode and
Huber, Biochim. Biophys. Acta 1477:241-252, 2000). Most of these
inhibitors are proteins having characteristic polypeptide
scaffolds, and are grouped into a number of families including the
Kunitz (Laskowski and Kato, Ann. Rev. Biochem. 49: 593-626, 1980),
Kazal (Laskowski and Kato, Ann. Rev. Biochem. 49: 593-626, 1980),
Serpin (Potempa et al., J. Biol. Chem. 269: 15957-15960, 1994) and
mucus (Wiedow et al., J. Biol. Chem. 265: 14791-14795, 1990)
families.
[0004] The Kunitz-type family comprises serine proteinase
inhibitors that include one or more Kunitz-type inhibitory domains.
Bovine pancreatic trypsin inhibitor (BPTI) is the prototypical
Kunitz-type inhibitor. The Kunitz-type family also includes tissue
factor pathway inhibitor (TFPI) and type-2 tissue factor pathway
inhibitor (TFPI-2). These two inhibitors have been investigated
extensively in the past decade, and have been shown to play an
important role in inhibiting serine proteinases involved in
coagulation and fibrinolysis (Girard et al., Nature 338:518-520,
1989; Broze et al., Biochemistry 29: 7539-7546, 1990; Sprecher et
al., Proc. Natl. Acad. Sci. USA 91: 3353-3357, 1994; Bajaj et al.,
Thromb. Haemost. 86:959-972, 2001).
[0005] Human TFPI-2, originally isolated from placenta and
designated as placental protein 5 (PP5), is a matrix-associated
inhibitor consisting of three tandemly arranged Kunitz-type
proteinase inhibitor domains flanked by a short acidic amino
terminus and a highly basic carboxy-terminal tail (Sprecher et al.,
Proc. Natl. Acad. Sci. USA 91:3353-3357, 1994; Miyagi et al., J.
Biochem. 116:939-942, 1994) (see FIG. 1). A wide variety of cells
including keratinocytes (Rao et al., J. Invest. Dermatol. 104:
379-383, 1995), dermal fibroblasts (Rao et al. J. Invest. Dermatol.
104: 379-383, 1995), smooth muscle cells (Herman et al. J. Clin.
Invest. 107: 1117-1126, 2001), syncytiotrophoblasts (Udagawa et al.
Placenta 19:217-223, 1998), synoviocytes (Sugiyama et al. FEBS
Lett. 517: 121-128, 2002), and endothelial cells (Iino et al.
Arterioscler. Thromb. Vasc. Biol. 18: 40-46, 1998) synthesize and
secrete TFPI-2, primarily into their extracellular matrix. Three
variants/isoforms of molecular mass 32 kDa, 30 kDa and 27 kDa are
synthesized by these cells and are thought to represent
differentially glycosylated fauns (Rao et al., Arch. Biochem.
Biophys. 335:82-92, 1996).
[0006] TFPI-2 exhibits inhibitory activity towards a broad spectrum
of proteinases including trypsin, plasmin, chymotrypsin, cathepsin
G, plasma kallikrein and the factor VIIa-tissue factor complex.
However, TFPI-2 exhibits little, if any, inhibitory activity
towards urokinase-type plasminogen activator (uPA), tissue-type
plasminogen activator (tPA) and .alpha.-thrombin (Petersen et al.,
Biochemistry 35: 266-272, 1996). TFPI-2 presumably inhibits
proteinases through a P.sub.1 arginine residue (R24) in its
Kunitz-type domain, since an R24Q TFPI-2 mutant exhibited only
5-10% inhibitory activity toward trypsin, plasmin and the factor
VIIa-tissue factor complex (Kamei et al. Thromb. Res. 94: 147-152,
1999). Recently, TFPI-2 expression by a stably-transfected human
high-grade glioma cell line SNB19 resulted in a diminished capacity
to form tumors relative to their parental control or
mock-transfected SNB19 cells following intracerebral injection of
these cells into mice (Konduri et. al., Oncogene 20:6938-6945,
2001). This latter study provides strong experimental evidence that
down-regulation of TFPI-2 by tumor cells, presumably through
hypermethylation of the TFPI-2 promoter, plays a significant role
in the invasive properties of human gliomas.
[0007] Plasmin is known to degrade fibrinogen after surgery. Bovine
pancreatic trypsin inhibitor (BPTI), also known commercially as
aprotinin or Trasylol.RTM. (commercially available from Bayer
Corporation, West Haven, Conn.), is widely used in the clinic
post-operatively by anesthesiologists for general surgery patients
and patients undergoing cardiopulmonary bypass surgery to inhibit
the degradation of fibrinogen (fibrinolysis) by plasmin arising
through activation of the fibrinolytic pathway. Aprotinin inhibits
the activity of plasmin. However, aprotinin, being of bovine
origin, precipitates episodes of severe anaphylaxis on some
occasions (0.5-1%). Accordingly, there is still a need in the art
for improved formulations having antifibrinolytic activity that
does not produce the undesirable side effects associated with
traditional antifibrinolytic compositions.
SUMMARY OF THE INVENTION
[0008] The present invention provides a "KD1 polypeptide" that is
structurally equivalent to or structurally similar to the primary
structure of the KD1 domain of Kunitz inhibitor human type 2 tissue
factor pathway inhibitor (TFPI-2) (SEQ ID NO:2), as well as methods
for making and using a KD1 polypeptide.
[0009] In one embodiment, the KD1 polypeptide consists essentially
of a primary structure that is equivalent to the primary structure
of the wild-type KD1 domain of human tissue factor pathway
inhibitor-2 (TFPI-2) (SEQ ID NO:2). In another embodiment, the KD1
polypeptide consists essentially of a primary structure that is
similar to the primary structure of the wild-type KD1 domain of
human tissue factor pathway inhibitor-2 (TFPI-2) (SEQ ID NO:2),
preferably with the proviso that said polypeptide includes a lysine
instead of arginine at position 24 as defined for the wild-type KD1
amino acid sequence. In a preferred embodiment, the KD1 polypeptide
consists essentially of the primary structure of the wild-type KD1
domain of TFPI-2 (SEQ ID NO:2), or a biologically active subunit
thereof, with the proviso that said polypeptide includes a lysine
instead of arginine at position 24 as defined for the wild-type KD1
amino acid sequence; more preferably, the KD1 polypeptide comprises
SEQ ID NO:3. A biologically active subunit of KD1 is characterized
by deletions of 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid
residues at either or both of the amino-terminal or
carboxy-terminal end relative to the wild-type KD1 sequence.
[0010] In another embodiment, the KD1 polypeptide consists
essentially of a primary structure that is equivalent to or similar
to the primary structure of the wild-type KD1 domain of TFPI-2 (SEQ
ID NO:2), or a biologically active subunit thereof, with the
proviso that said polypeptide includes at least one conservative
amino acid substitution relative to the primary structure of the
wild-type KD1 domain of TFPI-2, and preferably with the further
proviso that said polypeptide includes a lysine instead of arginine
at position 24 as defined for the wild-type KD1 amino acid
sequence.
[0011] In another embodiment, the KD1 polypeptide consists
essentially of a KD1 domain having a primary structure that is
equivalent to or similar to the primary structure of the wild-type
KD1 domain of human tissue factor pathway inhibitor-2 (TFPI-2) (SEQ
ID NO:2); and optionally a multiply positively charged amino acid
sequence disposed at either or both of the N-terminal or C-terminal
end of the polypeptide. Preferably, the multiply positively charged
amino acid sequence includes an amino acid sequence from the
C-terminus of wild-type TFPI-2, more preferably the multiply
positively charged amino acid sequence comprises amino acids 192
through 211 of SEQ ID NO:1.
[0012] The KD1 polypeptide of the invention preferably exhibits
inhibitory activity against a serine protease that degrades
fibrinogen.
[0013] In another aspect, the invention includes pharmaceutical
compositions that include a KD1 polypeptide of the invention, or a
polynucleotide encoding said KD1 polypeptide, and a
pharmaceutically acceptable carrier are also encompassed by the
invention, as are polynucleotides encoding a KD1 polypeptide of the
invention.
[0014] In yet another aspect, the invention includes methods of
making a KD1 polypeptide and using a KD1 polypeptide. Methods of
using a KD1 polypeptide preferably utilize wild-type KD1
polypeptide (SEQ ID NO:2) and R24K KD1 polypeptide (SEQ ID NO:3),
including subunits thereof, as well as the targeted forms of any of
them as described herein. Targeted form include a KD1 polypeptide
consisting essentially of a KD1 domain having a primary structure
that is equivalent to or similar to the primary structure of the
wild-type KD1 domain of human tissue factor pathway inhibitor-2
(TFPI-2); and a multiply positively charged amino acid sequence
disposed at either or both of the N-terminal or C-terminal end of
the polypeptide.
[0015] The KD1 polypeptide of the invention, in any form described
herein, can advantageously be used to treat a subject for a
condition treatable by aprotinin. The condition treatable by
aprotinin may be associated with surgery or cardiovascular disease.
The KD1 polypeptide can also be used to treat other ailments
including, but not limited to, allergies, asthma, cancer or a
precancerous condition, influenza infection, or persons in need of
surgery, in which case it can be administered to the subject
before, during and/or after surgery. The surgery is preferably
performed on a component of the vascular system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The file of this patent contains at least one photograph
executed in color. Copies of this patent with color photographs
will be provided by the Office upon request and payment of the
necessary fee.
[0017] FIG. 1 is a schematic drawing of human tissue factor pathway
inhibitor-2 (TFPI-2) including its amino acid sequence (SEQ ID
NO:1).
[0018] FIG. 2 is a schematic drawing of wild-type TFPI-2 KD1 domain
including its amino acid sequence (SEQ ID NO:2). The amino acid
sequence shows the arginine residue at the P1 position (Arg24).
[0019] FIG. 3 is a schematic drawing of an R24K TFPI-2 KD1 domain
including its amino acid sequence (SEQ ID NO:3). The amino acid
sequence shows a lysine residue at the P1 position (Lys24).
[0020] FIG. 4 shows the amino acid sequences (SEQ ID NOs:4-21)
surrounding the P.sub.1 reactive site residue in selected
Kunitz-type inhibitors. BPTI sequence is from Creighton &
Charles (1987, J. Mol. Biol. 194, 11-22), APPI is from Ponte et al.
(1988, Nature 331, 525-52), APPH is from Sprecher et al. (1993,
Biochemistry 32, 4481-4486), TFPI is from Wun et al. (1988, J.
Biol. Chem. 263, 6001-6004), TFPI-2 is from Sprecher et al. (1994,
Proc. Natl. Acad. Sci. USA 91, 3353-3357), HAI-1 is from Shimomura
et al. (1997, J. Biol. Chem. 272, 6370-6376), HAI-2 is from
Kawaguchi et al. (1997, J. Biol. Chem. 272, 27558-27564),
I.alpha.TI is from Kaumeyer et al. (1986, Nucleic Acids Res. 14,
7839-7850), PLI is from Drobnic-Kosorok et al. (1990, Biol. Chem.
Hoppe Seyler 371, 57-61), UPTI is from Stallings-Mann et al. (1994,
J. Biol. Chem. 269, 24090-24094), SPI1 is from Nirmala et al.
(2001, Eur. J. Biochem. 268, 2064-2073), and AsKC1 is from Schweitz
et al. (1995, J. Biol. Chem. 270, 25121-25126).
[0021] FIG. 5 shows details of the specificity of TFPI-2 KD1 for
plasmin. The proteinase domain number of plasmin is based on
chymotrypsin numbering. A: Specific interactions between plasmin
and TFPI-2 KD1. Red represents oxygen, blue represents nitrogen and
green represents carbon atoms. Plasmin is shown with cyan ribbons
and TFPI-2 KD1 is shown with yellow ribbons. TFPI-2 KD1 has an
acidic patch (Asp 19 and Glu48) that interacts with a basic patch
on plasmin (Arg644{c98}, Arg719{c173} and Arg767{c221}, where the
"c" numbers refer to the analogous positions in chymotrypsin). The
NH.sub.2 groups of Arg719{c173} in plasmin could make H-bonds with
both of the side chain carboxylate groups of Glu48 in TFPI-2 KD1.
Gln738{c192} N.sub.E2 in plasmin appears to make a H-bond with the
carbonyl oxygen of Gly21 in TFPI-2 KD1. In addition to these
interactions, TFPI-2 KD1 contains a hydrophobic core consisting of
Leu18, Tyr20, Tyr31 and Phe42. This hydrophobic core is connected
to an interactive hydrophobic patch consisting of Leu26, Leu27,
Leu28 and Leu43. This hydrophobic patch in KD1 makes hydrophobic
interactions with the C.sub.B of Lys607{c61}, Phe583{c37},
Met585{c39} and Phe587{c41} in plasmin. B: Electrostatic potential
between TFPI-2 KD1 and plasmin proteinase domain. The electrostatic
potential between TFPI-2 KD1 and plasmin was determined using the
program GRASP (Nicholls et al., 1991, Proteins 11, 281-296), and
the orientation of the molecules is the same as in A. Blue
represents positive, red represents negative, and white represents
neutral residues. Region 1 refers to the interactions of the acidic
patch on TFPI-2 KD1 (Asp 19 and Glu48) and a basic patch on plasmin
(Arg644{c98}, Arg719{c173} and Arg767{c221}) described above, and
region 2 refers to the hydrophobic interactions between TFPI-2 KD1
and plasmin described above.
[0022] FIG. 6 shows models of the interaction of TFPI-2 KD1 with
trypsin and factor VIIa. The orientation of the molecules is the
same as FIG. 4. Blue represents positive, red represents negative,
and white represents neutral residues. A. Electrostatic potential
between TFPI-2 KD1 and trypsin using the program GRASP (Nicholls et
al., 1991, Proteins 11, 281-296). Region 1 shows the absence of the
interaction between the acidic region (Asp19 and Glu48) of TFPI-2
KD1 and a basic region present in plasmin but absent in trypsin.
Instead, this region is acidic in trypsin. Region 2 corresponds to
the hydrophobic interactions between TFPI-2 KD1 and trypsin, which
is similar to those in the interaction of TFPI-2 KD1 with plasmin.
B. Electrostatic potential between TFPI-2 KD1 and factor VIIa
determined using the program GRASP (Nicholls et al., 1991, Proteins
11, 281-296). Region 1 shows the absence of the interaction between
the acidic region (Asp 19 and Glu48) of TFPI-2 KD1 and a basic
region, which is present in plasmin but not factor VIIa. Instead,
this region is hydrophobic. Region 2 corresponds to the absence of
hydrophobic patch interactions between TFPI-2 KD1 and factor VIIa,
which are present in both plasmin and trypsin.
[0023] FIG. 7 shows a model structure of the first Kunitz-type
domain (KD1) of human TFPI-2 (SEQ ID NO:2). Residues mutated in
Example I are shaded.
[0024] FIG. 8 shows SDS-PAGE of recombinant TFPI-2 KD1 and various
KD1 mutants. A: Lane 1, wild-type KD1; lane 2, R24K KD1; lane 3,
R24Q KD1; lane 4, R29A KD1; lane 5, R29D KD1; lane 6, R29K KD1;
STD, mixture of reduced standard proteins. B: Lane 1, wild-type
KD1; lane 2, D19A KD1; lane 3, Y20A KD1; lane 4, G21D KD1; lane 5,
L26Q KD1; lane 6, F42A KD1; STD, mixture of reduced standard
proteins. Mutant KD1 preparations are designated according to the
notation by Shapiro and Vallee (Shapiro, et al., 1989, Biochemistry
28, 7401-7408), in which the single letter code for the original
amino acid is followed by its position in the sequence and the
single letter code for the new amino acid.
[0025] FIG. 9 shows expression of either wild-type or R24Q human
TFPI-2 by stably-transfected HT-1080 cells in the presence and
absence of G418. Stably-transfected HT-1080 cell lines, with an
initial expression level of .about.55 ng TFPI-2/ml/day/10.sup.6
cells, was continuously cultured, with passaging, in the presence
(.quadrature., .DELTA.) and absence (.box-solid., .tangle-solidup.)
of 0.6 g/ml G418. The supernatants were assayed weekly for either
TFPI-2 (.quadrature., .box-solid.) or R24Q TFPI-2 (.DELTA.,
.tangle-solidup.) expression by a sandwich ELISA as described in
Example II.
[0026] FIG. 10 shows growth rates of MT-1080, WT-1080 and QT-1080
cells in culture. MT-1080 cells (gray bars), WT-1080 cells (white
bars), and QT-1080 cells (black bars) were initially plated at a
density of 1.times.10.sup.5 cells/well in a six well plate. Every
seven days, the cells were trypsinized, counted and replated at the
same seeding density.
[0027] FIG. 11 shows histological and immunohistochemical analyses
of paraffin-embedded subcutaneous (A-H) and lung (I,J) tumors.
Tumor sections (50 were either stained with hematoxylin and eosin
(H&E) or treated with antibody as described in Materials and
Methods. (Panel A), H & E stained subcutaneous tumor; (Panels
B-D), immunohistochemical detection of TFPI-2 (arrows) in
subcutaneous tumors; (Panels E,F), immunohistochemical detection of
BrdU-positive cells (arrowheads) in subcutaneous tumors; (Panels
G,H), TUNEL staining for apoptotic cells (arrowheads) in
subcutaneous tumors; (Panels I,J), anti-TFPI-2 IgG
immunohistochemistry of metastatic lung tumors. Boxed area in I is
magnified an additional 2.5-fold in panel J. PC, peripheral cells
(Panels D, F & H). CC, core cells (Panels C, E & G).
Magnifications: A and B, 250.times.; I, 1000.times.; C-H, J,
2500.times..
[0028] FIG. 12 shows qualitative PCR analyses of cellular DNA
obtained from various tissues by microdissection. Cellular DNA used
as a template in these PCR reactions was obtained from
microdissected cells as described in Materials and Methods, and PCR
products resolved electrophoretically in 1.2% agarose gels.
Cellular DNA from mouse gastric and lung cells were processed in an
identical manner to exclude the possibility that the human-specific
primer pair cross-reacted with mouse DNA.
[0029] FIG. 13 shows real time quantitative RT-PCR analysis of
murine VEGF gene expression in tumors. A: melting curve analysis of
the VEGF and GAPDH amplicons. Distinct melting curves of VEGF
(dashed line) and GAPDH (solid line) are shown together with
controls. B: relative efficiency plot of VEGF and GAPDH. The
.DELTA.C.sub.T (difference in C.sub.T values of VEGF and GAPDH)
were calculated for each cDNA dilution. C: murine VEGF gene
expression levels in MT-1080, QT-1080 and WT-1080 tumor samples.
Mouse liver RNA (line-filled bar) was used as a positive control.
Each column represents the average of three amplification reactions
(error bars represent standard deviation) performed on a single
cDNA sample reverse-transcribed from RNA derived from each tumor
sample. Samples MT-2T, MT-3T and MT-6T are representative MT-1080
tumors (dot-filled bars). Samples WT-3T, WT-5T and WT-11T are
representative WT-1080 tumors (reverse-hatched bars), while samples
QT-1T, QT-5T, and QT-7T are representative QT-1080 tumors (small
square bars). D: agarose gel analyses of PCR products obtained
following specific amplification of murine VEGF (upper panel) and
murine GAPDH (lower panel) amplicons. Asterisks indicate negative
controls lacking reverse transcriptase in first strand cDNA
synthesis.
[0030] FIG. 14 shows the effect of TFPI-2 on endothelial cell
capillary tube formation. A, 6 hour HUVEC tube formation in the
absence of TFPI-2; B, 15 hour HUVEC tube formation in the presence
of 5 .mu.M TFPI-2; C, number of branch points fanned in 8 hours in
control endothelial cells (-TFPI-2) and endothelial cells treated
with exogenous TFPI-2 or VEGF at the indicated concentrations.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
Abbreviations
[0031] KD1, the first Kunitz-type domain of human TFPI-2; TFPI-2,
tissue factor pathway inhibitor-2; TFPI, tissue factor pathway
inhibitor; VIIa, Factor VIIa; BPTI, bovine pancreatic trypsin
inhibitor; APPI, amyloid precursor protein inhibitor; APPH, amyloid
precursor protein homolog; HAI, hepatocyte growth factor activator
inhibitor; I.alpha.TI, Inter-.alpha.-trypsin inhibitor; PLI,
porcine leukocyte inhibitor; UPTI, uterine plasmin/trypsin
inhibitor; SPI1, silk proteinase inhibitor-1; AsKC1, A. sulcata
kalicludine1; TF, tissue factor; K.sub.i, equilibrium inhibition
constant; S-2251, H-D-Val-Leu-Lys-p-nitroanilide; S-2288,
H-D-Ile-Pro-Arg-p-nitroanilide; IPTG,
isopropylthiogalactopyranoside; SDS-PAGE, sodium dodecyl
sulfate-polyacrylamide gel electrophoresis; BSA, bovine serum
albumin; TBS, 50 mM Tris-HCl (pH 7.5) containing 100 mM NaCl.
[0032] The Kunitz inhibitor human type 2 tissue factor pathway
inhibitor (TFPI-2) is a 213 amino acid polypeptide comprising three
tandem Kunitz-type domains designated as KD1, KD2 and KD3 (FIG. 1).
The wild-type KD1 domain includes approximately the first 72 amino
acids of the TFPI-2 amino acid sequence (FIG. 2).
[0033] In one aspect, the present invention is directed to a KD1
polypeptide that is structurally similar to the first domain, KD1,
of wild-type TFPI-2, but has been modified so as to contain a
lysine residue at position 24 in place of the wild-type arginine
(e.g., FIG. 3). By "structurally similar" to KD1, it is meant that
a polypeptide includes all or most of the amino acid sequence of
the wild-type KD1 domain, as well as conservative amino acid
substitutions. In other words, the primary structure (amino acid
sequence) of the KD1 polypeptide of the invention is essentially
the same as the primary structure (amino acid sequence) of
wild-type KD1 (optionally including conservative amino acid
substitutions), with the proviso that in this aspect of the
invention a lysine is present at position 24. The change at
position 24 is represented by the notation "R24K" (Arg to Lys at
position 24, using the wild-type numbering system). The polypeptide
of the invention is thus referred to herein as an "R24K KD1
polypeptide" or simply as "R24K KD1."
[0034] The term "structurally similar" to a wild-type KD1
polypeptide indicates that the polypeptide of the invention can
include conservative substitutions, especially substitutions of
hydrophobic amino acids, relative to the amino acids in wild-type
KD1, as long as the substitutions do eliminate the biological
activity of the R24K KD1 polypeptide as described below and, in
this aspect of the invention, as long as the lysine at position 24
is maintained, since that change represents the essence of the
novel polypeptide of this aspect of the invention. The biological
activity of a KD1 polypeptide as a protease inhibitor can be
readily evaluated using the assays described herein, and it is
routine in the art to perform such assays.
[0035] Conservative substitutions for an amino acid are selected
from other members of the class to which the amino acid belongs.
For example, nonpolar (hydrophobic) amino acids include alanine,
leucine, isoleucine, valine, proline, phenylalanine, tryptophan,
tyrosine and glycine. Polar neutral amino acids include glycine,
serine, threonine, cysteine, tyrosine, asparagine and glutamine.
The positively charged (basic) amino acids include arginine, lysine
and histidine. The negatively charged (acidic) amino acids include
aspartic acid and glutamic acid. Examples of preferred conservative
substitutions include Lys for Arg and vice versa to maintain a
positive charge; Glu for Asp and vice versa to maintain a negative
charge; Ser for Thr so that a free --OH is maintained; and Gln for
Asn to maintain a free NH.sub.2. The R24K KD1 polypeptide of the
invention includes derivatives, analogs and variants of the
polypeptides described herein.
[0036] Additionally, the term "structurally similar" to wild-type
KD1 indicates that an embodiment of an R24K KD1 polypeptide that
includes "most" of the amino acids in the wild-type KD1 domain can
include a truncated form of KD1 (also referred to as a "subunit" of
KD1) characterized by deletions of 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10
amino acid residues at either or both of the amino-terminal or
carboxy-terminal end relative to the wild-type KD1 sequence.
[0037] The R24K KD1 polypeptide of the invention preferably
includes at least a biologically active portion of the first
Kunitz-type domain, KD1, of human tissue factor pathway inhibitor-2
(TFPI-2), modified so as to include a lysine residue rather than
arginine at position 24. A biologically active portion of a KD1
domain is a portion that exhibits inhibitory activity against a
serine protease, such as plasmin or trypsin, that may be
responsible for the degradation of fibrinogen or the activation of
a wide variety of proteins involved in tumor metastasis, asthma and
influenza virus hemagglutinin activation. In a preferred
embodiment, the R24K KD1 polypeptide exhibits a higher degree of
antifibrinolytic activity, e.g., enhanced activity toward plasmin
and/or trypsin, than that exhibited by wild-type KD1.
[0038] Notably, the C-terminus of wild-type TFPI-2 is highly
positively charged and has been postulated to bind to matrix
proteoglycans. Accordingly, in another aspect, the invention
provides a KD1 polypeptide that includes, appended to its
C-terminus, an amino acid sequence having multiple (two or more)
positive charges. Positively charged amino acids include arginine,
lysine and histidine. This embodiment of the KD1 polypeptide,
having the positively charged C-terminal "tail," is referred to
herein as a "targeted" form of a KD1 polypeptide or simply a
"targeted KD1 polypeptide" as it is "targeted," in a nonspecific
way, to the matrix proteoglycans or other negatively charged
molecules.
[0039] In a preferred embodiment, the targeted polypeptide thus
consists essentially of two components: a KD1 domain, and a
positively charged amino acid sequence attached to one or both
termini. The targeted polypeptide does not include a KD2 or KD3
domain as does the wild-type TFPI-2. The KD1 domain of the targeted
polypeptide can be equivalent to the wild-type KD1 domain, or it
can be a KD1 domain that is structurally similar to the wild-type
KD1 domain, as described above, as well as subunits, derivatives,
analogs and variants thereof. A particularly preferred embodiment
of the targeted polypeptide is one that includes a wild-type KD1
domain or an R24K KD1 domain, and a positively charged amino acid
sequence at the C- or N-terminus, as further described herein. As
used herein, the term "domain" describes a polypeptide; thus for
example a KD1 "domain" refers to the polypeptide that makes up the
KD1 domain.
[0040] Although any positively charged sequence can be used, the
C-terminus of wild-type TFPI-2 represents a convenient and natural
choice for use as the positively charged amino acid sequence to
form the targeted KD1 polypeptide. For example, a targeted KD1
polypeptide can include, appended to its C-terminus, a positively
charged amino acid sequence that lies within the region bounded by
amino acid 190 in the N-terminal direction and amino acid 213 in
the C-terminal direction of wild-type TFPI-2. Preferably, the
positively charge sequence begins at amino acid 190, 191, 192, 193,
194, 195, 196, 197, 198, 199 or 200 of wild-type TFPI-2 (SEQ ID
NO:1) and ends at amino acid 211, 212 or 213 of wild-type TFPI-2
(SEQ ID NO:1). An example of a preferred positively charged amino
acid sequence is one that begins at amino acid 192 and ends at
amino acid 211.
[0041] Although the targeted KD1 polypeptide of the invention is
described primarily with reference to a positively charged amino
acid sequence at the C-terminus, the invention also includes a
variation wherein the positively charged amino acid sequence is
present instead (or in addition) at the N-terminus, prior to the
KD1 amino acid sequence. An example of a targeted, N-terminus
modified KD1 polypeptide is a KD1 polypeptide that includes a
"histidine tag" (multiple histidines) at the N-terminus.
[0042] The positively charged terminal amino acid sequence present
on the targeted form of the KD1 polypeptide may bind to one or more
negatively-charged proteoglycans in the extracellular matrix and
assist the polypeptide in increasing its local concentration in the
extracellular matrix, thereby facilitating its ability to readily
inhibit serine proteases in this environment. This embodiment of
the KD1 polypeptide thus can function in vivo pericellularly by
virtue of binding to proteoglycans. Targeting the proteoglycan
layer may be especially advantageous in connection with use of the
protease inhibitor in cancer, asthma and influenza therapies, as
described below.
[0043] The KD1 polypeptide can also function in the blood and other
extracellular locations, for example to inhibit plasmin,
particularly if it is present in the form of an embodiment lacking
a positively charged terminal sequence as described in the
preceding paragraphs. However, forms of KD1 having one or more
positively charged targeting sequences at the C- and or N-terminus
(including targeted wild-type KD1 and targeted R24K KD1) are
expected to function in the blood and at other extracellular
locations as well.
[0044] A polypeptide of the invention, such as the wild-type KD1
polypeptide, R24K KD1 polypeptide or the targeted form of either of
those polypeptides having the multiply positively charged
N-terminus or C-terminus, can be produced by recombinant
engineering, for example using a bacterial, insect or mammalian
host cell, or by using enzymatic or chemical synthesis in vitro.
Preferably, the polypeptide is produced by recombinant engineering
in a bacterial cell, such as E. coli. Conveniently, while the
second and third domains (KD2 and KD3) of TFPI-2 have glycosylation
sites, the first domain (KD1) has no known glycosylation sites,
making it amenable to expression in bacterial systems, as well as
eukaryotic systems.
[0045] It should be understood that the term polypeptide as used
herein does not connote a specific length of a polymer of amino
acids, nor is it intended to imply or distinguish whether the
polypeptide is produced using recombinant techniques, chemical or
enzymatic synthesis, or is naturally occurring.
[0046] A polypeptide of the invention, such as the wild-type KD1
polypeptide, R24K KD1 polypeptide or the targeted form of either of
those polypeptides having the multiply positively charged
N-terminus or C-terminus, can be readily formulated as a
pharmaceutical composition for veterinary or human use. The
pharmaceutical composition optionally includes excipients or
diluents that are pharmaceutically acceptable as carriers and
compatible with the biological material. The term "pharmaceutically
acceptable carrier" refers to a carrier(s) that is "acceptable" in
the sense of being compatible with the other ingredients of a
composition and not deleterious to the recipient thereof. Suitable
excipients are, for example, water, saline, dextrose, glycerol,
ethanol, or the like and combinations thereof. In addition, if
desired, the pharmaceutical composition may contain minor amounts
of auxiliary substances such as wetting or emulsifying agents, pH
buffering agents and/or salts. Also, the pharmaceutical composition
can include additional therapeutic agents. Methods of making and
using such pharmaceutical compositions are also included in the
invention.
[0047] Also included in the invention is a polynucleotide
comprising a nucleotide sequence that encodes a polypeptide of the
invention, for example a wild-type KD1 polypeptide, an R24K KD1
polypeptide or a targeted form of either of those polypeptides
having the multiply positively charged N-terminus or C-terminus.
The term "polynucleotide" refers broadly to a polymer of two or
more nucleotides covalently linked in a 5' to 3' orientation. The
terms nucleic acid, nucleic acid sequence, and oligonucleotide are
included within the definition of polynucleotide and these terms
may be used interchangeably. It should be understood that these
terms do not connote a specific length of a polymer of nucleotides,
nor are they intended to imply or distinguish whether the
polynucleotide is produced using recombinant techniques, chemical
or enzymatic synthesis, or is naturally occurring. The
polynucleotides of the invention can be DNA, RNA, or a combination
thereof, and can include any combination of naturally occurring,
chemically modified or enzymatically modified nucleotides.
[0048] Polynucleotides can be single-stranded or double-stranded,
and the sequence of the second, complementary strand is dictated by
the sequence of the first strand. The teen "polynucleotide" is
therefore to be broadly interpreted as encompassing a single
stranded nucleic acid polymer, its complement, and the duplex
formed thereby. "Complementarity" of polynucleotides refers to the
ability of two single-stranded polynucleotides to base pair with
each other, in which an adenine on one polynucleotide will base
pair with a thymidine (or uracil, in the case of RNA) on the other,
and a cytidine on one polynucleotide will base pair with a guanine
on the other. Two polynucleotides are complementary to each other
when a nucleotide sequence in one polynucleotide can base pair with
a nucleotide sequence in a second polynucleotide. For instance,
5'-ATGC and 5'-GCAT are fully complementary, as are 5'-GCTA and
5'-TAGC.
[0049] Preferred polynucleotides of the invention include
polynucleotides having a nucleotide sequence that is "substantially
complementary" to (a) a nucleotide sequence that encodes a
polypeptide according to the invention, or (b) the complement of
such nucleotide sequence. "Substantially complementary"
polynucleotides can include at least one base pair mismatch, such
that at least one nucleotide present on a second polynucleotide,
however the two polynucleotides will still have the capacity to
hybridize. For instance, the middle nucleotide of each of the two
DNA molecules 5'-AGCAAATAT and 5'-ATATATGCT will not base pair, but
these two polynucleotides are nonetheless substantially
complementary as defined herein. Two polynucleotides are
substantially complementary if they hybridize under hybridization
conditions exemplified by 2.times.SSC (SSC: 150 mM NaCl, 15 mM
trisodium citrate, pH 7.6) at 55.degree. C. Substantially
complementary polynucleotides for purposes of the present invention
preferably share at least one region of at least 20 nucleotides in
length which shared region has at least 60% nucleotide identity,
preferably at least 80% nucleotide identity, more preferably at
least 90% nucleotide identity and most preferably at least 95%
nucleotide identity. Particularly preferred substantially
complementary polynucleotides share a plurality of such
regions.
[0050] Nucleotide sequences are preferably compared using the
Blastn program, version 2.2.10, of the BLAST 2 search algorithm,
also as described by Tatusova et al. (FEMS Microbiol. Lett, 174,
247-250 (1999)), and available on the World Wide Web at the
National Center for Biotechnology Information website, under BLAST
in the Molecular Database section. Preferably, the default values
for all BLAST 2 search parameters are used, including reward for
match=1, penalty for mismatch=-2, open gap penalty=5, extension gap
penalty=2, gap x_dropoff=50, expect=10, wordsize=11, and
optionally, filter on. Locations and levels of nucleotide sequence
identity between two nucleotide sequences can also be readily
determined using CLUSTALW multiple sequence alignment software (J.
Thompson et al., Nucl. Acids Res., 22:4673-4680 (1994)), available
at from the World Wide Web at the European Bioinformatics Institute
website in the "Toolbox" section as the ClustalW program.
[0051] It should be understood that a polynucleotide that encodes a
polypeptide of the invention is not limited to a polynucleotide
that contains all or a portion of naturally occurring genomic or
cDNA nucleotide sequence, but also includes the class of
polynucleotides that encode such polypeptides as a result of the
degeneracy of the genetic code. The class of nucleotide sequences
that encode a selected polypeptide sequence is large but finite,
and the nucleotide sequence of each member of the class can be
readily determined by one skilled in the art by reference to the
standard genetic code, wherein different nucleotide triplets
(codons) are known to encode the same amino acid. It should further
be noted that production, purification and use of human Kunitz type
inhibitors, specifically TFPI-2, are described in detail in U.S.
Pat. No. 5,914,315 (Sprecher et al.). As it is structurally
equivalent to or similar to the first domain of TFPI-2, the KD1
polypeptide of the invention (e.g., wild-type KD1 polypeptide or
R24K polypeptide) can be produced, purified and used substantially
in accordance with the methods described therein.
[0052] In the embodiment described in Example I, R24K KD1 is a
recombinant polypeptide that includes residues 1-73 of intact human
TFPI-2 with substitution of arginine by lysine at residue number
24. In that embodiment, the N-terminus of R24K KD1 includes four
additional amino acid residues derived from the expression vector
after the thrombin cleavage site which include, in order, glycine
(gly, G), serine (ser, S), histidine (his, H), and methionine (met,
M).
[0053] The KD1 polypeptide of the invention may be prepared by
recombinant DNA technology or synthesized directly, either
chemically or enzymatically. An illustrative example of a method
for producing a recombinant R24K KD1 is shown in Example I. In that
example, R24K KD1 was overexpressed as an N-terminal
histidine-tagged fusion protein in Escherichia coli strain
BL21(DE3)pLys using the T7 promoter system (Studier et al., Meth.
Enzymol. 185: 60-89, 1990). The recombinant plasmid derived from
pET28a (Novagen, Madison, Wis.) bearing a hexahistidine-tag leader
sequence followed by a thrombin cleavage site and cDNA encoding the
first Kunitz-type domain of wild-type TFPI-2 was prepared according
to standard procedures (Sambrook and Russel, Molecular Cloning: A
Laboratory Manual, 3.sup.rd Edition, CSHL Press, 2001).
[0054] Using this recombinant vector as a template, the mutation of
arginine-24 to lysine-24 was generated using a QuickChange.RTM.
site-directed mutagenesis kit (Stratagene, La Jolla, Calif.)
according to the manufacturer's instruction. The recombinant
pET28a-R24K KD1 vector was transformed into BL21(DE3)pLysS by the
calcium chloride method (Cohen et al., Proc. Natl. Acad. Sci. USA
69:2110-2114, 1972). His-tagged R24K KD1 preparations were
expressed in E. coli grown in rich media containing 100 mg/L
ampicillin, and induced at 37.degree. C. with 1 mM isopropyl
thiogalactopyranoside (IPTG) at mid log-phase
(A.sub.600=0.6-0.8).
[0055] The overexpressed 6-His-tag R24K KD1 was recovered from the
cell lysate in the form of inclusion bodies. The solubulized
inclusion bodies were recovered by high-speed centrifugation and
filtered through a 0.22 .mu.l Nalgene.RTM. filter before
application to a His-Trap.RTM. column (Amersham Biosciences Corp.,
Piscataway, N.J.). The His-Trap affinity column was used in a
Pharmacia Fast Protein Liquid Chromatography system (FPLC) and
purification carried out following the manufacturer's protocol.
[0056] Fractions eluting from the His-Trap column containing
denatured, unfolded His.sub.6-R24K KD1 were identified by sodium
dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE;
Laemmli, Nature 227, 680-685, 1970), pooled, and oxidatively
refolded according to the procedure described by Stone and
coworkers (Stone et al., Biochem. J. 310:605-614, 1995) for the
refolding of E. coli-derived soluble tissue factor. The refolded
protein was then purified to homogeneity by anion exchange
chromatography using a MONO Q (MONO Q HR 5/5) FPLC column (Amersham
Biosciences Corp., Piscataway, N.J.). R24K KD1 was eluted from this
column in a linear NaCl gradient consisting of 50 mM Tris-HCl (pH
9.0) and 50 mM Tris-HCl (pH 9.0) containing 1 M NaCl.
[0057] Alternatively, the KD1 polypeptide can be purified by
Q-Sepharose FF column chromatography under the same conditions used
for the MONO Q FPLC purification. Fractions were subjected to
SDS-PAGE analysis and fractions containing pure His.sub.6-R24K KD1,
as evidenced by a single band, were pooled for further analysis.
The purified His.sub.6-R24K KD1 was then dialyzed against 50 mM
Tris-HCl (pH 8) and subsequently treated with human thrombin
(1:1000 enzyme:protein molar ratio) for 6 hours at 37.degree. C. to
cleave and separate the His-tag leader sequence from the R24K KD1.
The liberated His-tag was removed from the digest by FPLC using a
His-Trap.RTM. column, and the R24K KD1/thrombin mixture eluted in
the unadsorbed fraction. Thrombin was removed from the sample by
SP-Sephadex C-50 chromatography as described for the purification
of thrombin (Kisiel et al., Blood 66: 1302-1308, 1985). The
concentration of the R24K KD1 was determined by measuring its
absorbance at 280 nm using a calculated value for E.sup.1% derived
from its tyrosine, tryptophan and cysteine content (Gill and von
Hippel, Anal. Biochem. 182: 319-326, 1989).
[0058] The invention provides a novel method for purifying the KD1
polypeptide of the invention, such as a wild-type KD1 polypeptide
or the R24K KD1 polypeptide, as exemplified in Example II.
Refolding of the solubilized, denatured polypeptide in urea is
facilitated by raising the pH to about 9, such that the protein can
be refolded at higher concentrations. Refolding and purification at
pH 9 markedly decreases precipitation of the denatured polypeptide
commonly observed in refolding strategies. Without intending to
limit the invention to any particular mechanism of action, improved
solubility and recovery of the R24K KD1 at pH 9 is probably related
to the high calculated pI value of R24K KD1 (pI=7.44).
[0059] The inhibitory activity of purified recombinant KD1
polypeptide of the invention, such as wild-type KD1 polypeptide,
R24K KD1 polypeptide, or the targeted form of either of them having
a multiply positively charged N-terminus or C-terminus, toward
plasmin is readily assessed, for example, as described in Petersen
et al. (Biochemistry 35:266-272, 1996). Example I provides an
illustrative example of assessment of the inhibitory activity.
Briefly, human plasmin (30 nM; Haematologic Technologies Inc.,
Essex Junction, Vt.) was incubated with various concentrations of
R24K KD1 for 15 min at 37.degree. C. in a 96-well microtitration
plate. The chromogenic substrate S-2251
(D-Val-Leu-Lys-p-nitroanilide; DiaPharma Group Inc., West Chester,
Ohio) was then added and residual plasmin amidolytic activity was
measured at 405 nm in a Molecular Devices UV.sub.max kinetic
microplate reader. The inhibition constant, K.sub.i, for R24K KD1
inhibition of plasmin was determined using the non-linear
regression data analysis program Ultrafitfv3.0 as described (see
Example I).
[0060] As demonstrated in Example I, the isolated first Kunitz-type
domain (KD1) of human TFPI-2 (see FIG. 2) exhibited stronger
inhibitory activity towards several serine proteinases in
comparison to intact TFPI-2. The R24K KD1 mutant polypeptide
exhibited enhanced inhibitory activity toward plasmin and trypsin
in comparison to wild-type KD1. R24K KD1 was prepared by
substituting the reactive site P.sub.1 arginine residue at position
24 with a lysine residue by site-specific mutagenesis. R24K KD1 was
shown to inhibit the fibrinolytic proteinase plasmin with an
inhibition constant (K.sub.i) of 0.85 nM, which is similar (0.75
nM) to that observed for the inhibition of plasmin by the
prototypical Kunitz-type inhibitor known as bovine pancreatic
trypsin inhibitor (BPTI), also known commercially as aprotinin or
Trasylol.RTM.. Unexpectedly, a lysine substitution at the P.sub.1
position (R24K) in KD1 significantly increased its inhibitory
activity toward plasmin, making it essentially as effective as BPTI
toward this proteinase.
[0061] The present invention further includes antibodies, both
monoclonal and polyclonal, that bind specifically to the R24K KD1
polypeptide, thereby distinguishing it from wild-type KD1. The R24K
KD1 polypeptide of the invention can be used as an antigen to
produce antibodies, including vertebrate antibodies, hybrid
antibodies, chimeric antibodies, humanized antibodies, altered
antibodies, univalent antibodies, monoclonal and polyclonal
antibodies, Fab proteins and single domain antibodies. Optionally,
the polypeptide is covalently linked to an immunogenic carrier such
as keyhole limpet hemocyanin (KLH), bovine serum albumin,
ovalbumin, mouse serum albumin, rabbit serum albumin, and the
like.
[0062] If polyclonal antibodies are desired, a selected animal
(e.g., mouse, rabbit, goat, horse or bird, such as chicken) is
immunized with the R24K KD1 polypeptide. Serum from the immunized
animal is collected and treated according to known procedures. If
the serum contains polyclonal antibodies that bind to the R24K
polypeptide, the polyclonal antibodies can be purified by
immunoaffinity chromatography. Techniques for producing and
processing polyclonal antisera are known in the art (see for
example, Mayer and Walker eds. Immunochemical Methods in Cell and
Molecular Biology (Academic Press, London) (1987), Coligan, et al.,
Unit 9, Current Protocols in Immunology, Wiley Interscience (1991),
Green et al., Production of Polyclonal Antisera, in Immunochemical
Protocols (Manson, ed.), pages 1-5 (Humana Press 1992); Coligan et
al., Production of Polyclonal Antisera in Rabbits, Rats, Mice and
Hamsters, in Current Protocols in Immunology, section 2.4.1
(1992)).
[0063] Monoclonal antibodies directed against R24K KD1 polypeptide
are also included in the invention, and can be readily produced by
one skilled in the art. The general methodology for making
monoclonal antibodies by hybridomas is well known. Immortal
antibody-producing cell lines can be created by cell fusion, and
also by other techniques such as direct transformation of B
lymphocyte cells with oncogenic DNA, or transfection with
Epstein-Barr virus (See Monoclonal Antibody Production. Committee
on Methods of Producing Monoclonal Antibodies, Institute for
Laboratory Animal Research, National Research Council; The National
Academies Press; (1999), Kohler & Milstein, Nature, 256:495
(1975); Coligan et al., sections 2.5.1-2.6.7; and Harlow et al.,
Antibodies: A Laboratory Manual, page 726 (Cold Spring Harbor Pub.
1988)). Panels of monoclonal antibodies produced against the
polypeptide of the invention can be screened for various
properties, for example epitope affinity.
[0064] Antibodies can also be prepared through use of phage display
techniques. Phage display methods to isolate antigens and
antibodies are known in the art and have been described (Gram et
al., Proc. Natl. Acad. Sci., 89:3576 (1992); Kay et al., Phage
display of peptides and proteins: A laboratory manual. San Diego:
Academic Press (1996); Kermani et al., Hybrid, 14:323 (1995);
Schmitz et al., Placenta, 21 Suppl. A:S106 (2000); Sanna et al.,
Proc. Natl. Acad. Sci., 92:6439 (1995)).
[0065] Antibody specificity can be evaluated, for example, by
performing Western blot analysis and comparing the results for
wild-type KD1 polypeptide and R24K KD1 polypeptide. Antibodies that
bind to R24K KD1 polypeptide but not wild-type KD1 polypeptide are
considered to be specific for the R24K KD1 polypeptide of the
invention. The R24K KD1 polypeptide of the invention has many
therapeutic applications. This polypeptide has structural and
functional properties that are virtually identical to aprotinin,
and therefore is expected to be advantageous for use in any
therapeutic application for which aprotinin is useful. Unlike
aprotinin, however, the R24K polypeptide of the invention is based
on a polypeptide of human origin. Accordingly, the incidences of
reactivity to it are expected to be very low in comparison to
aprotinin, which elicits adverse reactions, such as anaphylaxis, in
0.5% to 1% of patients (and a higher rate in patients receiving
aprotinin a second time).
[0066] Like aprotinin, the polypeptide of the invention can be used
as an inhibitor of fibrinolysis and coagulation in patients
undergoing surgery for treatment before, during and after
cardiovascular surgery such as cardiopulmonary bypass procedures,
as well as other therapeutic applications, such as deep vein
thrombosis, disseminated intravascular coagulation, pulmonary
embolism and for the prevention of thrombosis following surgery.
For example, the wild-type KD1 polypeptide or the R24K KD1
polypeptide, or a targeted form of either of them as described
herein, can be used prophylactically to reduce perioperative blood
loss and the need for blood transfusion in patients undergoing
cardiopulmonary bypass (CPB) in the course of coronary artery
bypass graft (CABG) surgery. Aprotinin has also been used to block
thrombin-mediated PAR 1 activation on platelets of patients
undergoing coronary artery bypass grafting (Day et al, Circulation
110: 2597-2600, 2004), and it is expected that the polypeptide of
the invention will have analogous activity.
[0067] The mode of administration and dosing regimen for the KD1
polypeptide are similar to those used for aprotinin for similar
applications. As aprotinin is well known and in current therapeutic
use, one of skill in the art will appreciate that the dosing
amounts and regimens, and methods of administration, that are
applicable to aprotinin can be readily employed for use with the
KD1 polypeptide of the invention, such as wild-type KD1 polypeptide
or R24K polypeptide. Dosing regimens for aprotinin (Trasylol.RTM.,
Bayer Corporation, West Haven, Conn.) are applicable to the R24K
polypeptide of the invention and can be found in the 2004
Physician's Desk Reference on page 864. A recent article describing
aprotinin dosing (Niimi, J. Extra Corpor Technol 36: 384-390, 2004)
also sets forth exemplary protocols including amounts, timing,
modes of administration, and the like. See also Levy et al.,
"Efficacy and Safety of Aprotinin in Cardiac Surgery," Orthopedics
(June 2004 Supplement) and Levy et al., Aprotinin: A Pharmacologic
Overview," (June 2004 Supplement), available online at the
HYPERLINK "www.orthosupersite.com." Administration by any
convenient route is contemplated, including parenteral
administration, such as intravenous injection, intramuscular
injection, inhalation or topical application; however, the
preferred method of administration is intravenous injection and
perfusion.
[0068] In addition, since plasmin is a key proteinase in many
pathological conditions associated with malignancy and the
migration of cells to inflammatory sites in vivo, it is
contemplated that the KD1 polypeptide of the invention, such as
wild-type KD1 polypeptide, R24K KD1 polypeptide, or the targeted
forms of either of them as described herein, finds further
therapeutic applications in the treatment of cancer and asthma (see
Examples I and III; Chand et al., J. Biol. Chem. 2004;
279(17):17500-7; Epub 2004 Feb. 16. Erratum in: J. Biol. Chem.
2004; 279(23):24906; Chand et al., Blood 103: 1069-1077, 2004; Epub
2003 Oct. 2). In particular, a KD1 polypeptide such as wild-type
KD1 as well as the R24K KD1 polypeptide can be used to treat
asthma. In an art-recognized animal model, hexahistidine-tagged KD1
was shown to block leukocytes from migrating into the lung (Example
IV), thereby indicating that it represents an effective asthma
therapy. The KD1 polypeptide can be administered to an asthmatic
subject in any convenient manner, such as intravenously,
intramuscularly or by inhalation. Intravenous injection can be
accomplished using an implanted pump. Preferably, however, the
polypeptide is administered via inhalation, for example as an
aerosol. The KD1 polypeptide can be administered in acute episodes
of asthma, for example as treatment for an asthmatic attack or
anaphylaxis or as a continuing, periodic treatment for chronic
asthmatic conditions.
[0069] A KD1 polypeptide of the invention such as wild-type KD1 as
well as the R24K KD1 polypeptide, including the targeted forms
thereof, can be used to treat cancer and precancerous conditions.
It is known that some tumors downregulate TFPI-2. Tumor cells can
secrete one or more proteases, but this may not be accompanied by
secretion of one or more protease inhibitors. The uninhibited
protease causes proteolytic digestion of basement membranes, for
example, and allows the tumor cells to mobilize, facilitating
metastases. This process can be counteracted by, for example,
administering a wild-type KD1 polypeptide or an R24K KD1
polypeptide to the subject, for example using via indwelling pumps,
to reduce tumor growth and tumor metastasis.
[0070] Additionally, we have shown that hexahistidine-tagged human
KD1 exhibits dose-dependent inhibition of angiogenesis in a
commercially available in vitro human endothelial cell angiogenesis
assay. The angiogenesis assay is commercially available from
Chemicon International, Inc. (Temecula, Calif.), and involves
growing human umbilical vein endothelial cells (HUVECs) on a
proprietary matrix, followed by assessing angiogenesis on this
matrix by counting new branch points in sprouting endothelial
cells.
[0071] The KD1 polypeptide of the invention, including a wild-type
KD1 and an R24K KD1 polypeptide, as well as their targeted forms as
described herein, may be also be used therapeutically to treat
influenza infections. Aprotinin has been shown to inhibit the
cleavage of influenza A virus hemagglutinin in vitro, and
diminished the infectivity of the virus (Zhirnov et al., J. Virol.
76: 8682-8689, 2002). The KD1 polypeptide of the invention is
expected to have similar activity.
[0072] In therapeutic applications, it may be particularly
advantageous to append to the KD1 polypeptide (such as a wild-type
KD1 polypeptide or a R24K KD1 polypeptide) the multiply positively
charged C-terminus or N-terminus region as described above, so as
to target the extracellular matrix and prevent its breakdown by
tumor cell-secreted proteases.
EXAMPLES
[0073] The present invention is illustrated by the following
examples. It is to be understood that the particular examples,
materials, amounts, and procedures are to be interpreted broadly in
accordance with the scope and spirit of the invention as set forth
herein.
Example I
Structure-Function Analysis of the Reactive Site in the First
Kunitz-Type Domain of Human Tissue Factor Pathway Inhibitor-2
Summary
[0074] Human tissue factor pathway inhibitor-2 (TFPI-2) is a
Kunitz-type proteinase inhibitor that regulates a variety of serine
proteinases involved in coagulation and fibrinolysis through their
non-productive interaction with a P.sub.1 residue (Arg24) in its
first Kunitz-type domain (KD1). Previous kinetic studies revealed
that TFPI-2 was a more effective inhibitor of plasmin than several
other serine proteinases, but the molecular basis for this
specificity was unclear. In this study, we employed molecular
modeling and mutagenesis strategies to produce several variants of
human TFPI-2 KD1 in an effort to identify interactive site residues
other than the P.sub.1 Arg that contribute significantly to its
inhibitory activity and specificity. Molecular modeling of KD1
based on the crystal structure of bovine pancreatic trypsin
inhibitor revealed that KD1 formed a more energetically favorable
complex with plasmin versus trypsin and/or the factor VIIa-tissue
factor complex primarily due to strong ionic interactions between
Asp19 (P.sub.6) and Arg residues in plasmin (Arg644, Arg719 and
Arg767), Arg24 (P.sub.1) with Asp735 in plasmin, and Arg29
(P.sub.5') with Glu606 in plasmin. In addition, Leu26-28
(P.sub.2'-P.sub.4') in KD1 formed strong van der Waals contact with
a hydrophobic cluster in plasmin (Phe583, Met585 and Phe587).
Mutagenesis of Asp19, Tyr20, Arg24, Arg29, and Leu26 in KD1
resulted in substantial reductions in plasmin inhibitory activity
relative to wild-type KD1, but the Asp19 and Tyr20 mutations
revealed the importance of these residues in the specific
inhibition of plasmin. In addition to the reactive site residues in
the P.sub.6-P.sub.5' region of KD1, mutation of a highly conserved
Phe at the P.sub.18' position revealed the importance of this
residue in the inhibition of serine proteinases by KD1. Thus,
together with the P.sub.1 residue, the nature of other residues
flanking the P.sub.1 residue, particularly at P.sub.6 and P.sub.5',
strongly influences the inhibitory activity and specificity of
human TFPI-2.
Introduction
[0075] Proteinase inhibitors play a critical role in the regulation
of several physiological processes such as blood coagulation,
complement fixation, fibrinolysis, and fertilization (Bode et al.,
2000, Biochim. Biophys. Acta 1477, 241-252). Most of these
inhibitors are proteins having characteristic polypeptide
scaffolds, and are grouped into a number of families including the
Kunitz (Laskowski et al., 1980, Ann. Rev. Biochem. 49, 593-626),
Kazal (Laskowski et al., 1980, Ann. Rev. Biochem. 49, 593-626),
Serpin (Potempa et al., 1994, J. Biol. Chem. 269, 15957-15960) and
mucus (Wiedow et al., 1990, J. Biol. Chem. 265, 14791-14795)
families. The Kunitz-type family, serine proteinase inhibitors that
include one or more Kunitz-type inhibitory domains, includes tissue
factor pathway inhibitor (TFPI).sup.1 and type-2 tissue factor
pathway inhibitor (TFPI-2). These two inhibitors have been
investigated extensively in the past decade, and have been shown to
play an important role in inhibiting serine proteinases involved in
coagulation and fibrinolysis (Girard et al., 1989, Nature 338,
518-520; Broze et al., 1990, Biochemistry 29, 7539-46; Sprecher et
al., 1994, Proc. Natl. Acad. Sci. USA 91, 3353-3357; Bajaj et al.,
2001, Thromb. Haemost. 86, 959-972).
[0076] Human TFPI-2, originally isolated from placenta and
designated as placental protein 5 (PP5), is a matrix-associated
inhibitor consisting of three tandemly arranged Kunitz-type
proteinase inhibitor domains flanked by a short acidic
amino-terminus and a highly basic carboxy-terminal tail (Sprecher
et al., 1994, Proc. Natl. Acad. Sci. USA 91, 3353-3357; Miyagi et
al., 1994, J. Biochem. 116, 939-942). A wide variety of cells
including keratinocytes (Rao et al., 1995, J. Invest. Dermatol.
104, 379-383), dermal fibroblasts (Rao et al., 1995, J. Invest.
Dermatol. 104, 379-383), smooth muscle cells (Herman et al., 2001,
J. Clin. Invest. 107, 1117-1126), syncytiotrophoblasts (Udagawa et
al., 1998, Placenta 19, 217-223), synoviocytes (Sugiyama et al.,
2002, FEBS Lett. 517, 121-128) and endothelial cells (Iino et al.,
1998, Arterioscler. Thromb. Vasc. Biol. 18, 40-46) synthesize and
secrete TFPI-2 primarily into their extracellular matrix. Three
variants/isoforms of molecular mass 32 kDa, 30 kDa and 27 kDa are
synthesized by these cells and are thought to represent
differentially glycosylated forms (Rao et al., 1996, Arch. Biochem.
Biophys. 335, 45-52).
[0077] TFPI-2 exhibits inhibitory activity towards a broad spectrum
of proteinases including trypsin, plasmin, chymotrypsin, cathepsin
G, plasma kallikrein and the factor VIIa-tissue factor complex.
However, TFPI-2 exhibits little, if any, inhibitory activity
towards urokinase-type plasminogen activator (uPA), tissue-type
plasminogen activator (tPA) and .alpha.-thrombin (Petersen et al.,
1996, Biochemistry 35, 266-272). TFPI-2 presumably inhibits
proteinases through a P.sub.1 arginine residue (R24) in its first
Kunitz-type domain, as an R24Q TFPI-2 mutant exhibited only 5-10%
inhibitory activity towards trypsin, plasmin and the factor
VIIa-tissue factor complex (Kamei et al., 1999, Thromb. Res. 94,
147-152).
[0078] Recently, TFPI-2 expression by select tumors has been shown
to play a significant role in inhibiting tumor growth and
metastasis by a mechanism that involves its inhibitory activity
(Konduri et al., 2001, Oncogene 20, 6938-6945; Chand et al., 2004,
Blood 103, 1069-1077; Epub 2003 Oct. 2; Example III).
[0079] Several approaches have been employed to elucidate the
structure-function relationship and broad specificity of
Kunitz-type inhibitors using the well-characterized bovine
pancreatic trypsin inhibitor (BPTI) as a model. Detailed
biophysical and biochemical studies have provided a greater insight
into the structural basis for the association of BPTI, or its
homologues, to proteinases. Moreover, using semisynthetic (Wenzel
et al., 1982, FEBS Lett. 140, 53-57; Tschesche et al., 1987,
Biochim. Biophys. Acta 913, 97-101) or recombinant approaches
(Stassen et al., 1995, Thromb. Haemost. 74, 655-659; Kraunsoe et
al., 1996, FEBS Lett. 396, 108-112), it has been possible to change
or enhance the inhibitory activity and spectrum of BPTI, as well as
its homologues. Kunitz-type inhibitors possess a compact
pear-shaped structure stabilized by three disulfide bonds
containing a reactive site region featuring the principal
determinant P.sub.1 residue in a rigid conformation. These
inhibitors competitively prevent access of the serine proteinase
for its physiologically relevant macromolecular substrate through
insertion of the P.sub.1 residue into the active site cleft
(Wlodawer et al., 1987, J. Mol. Biol. 193, 145-156). In addition to
the P.sub.1 residue, other residues within the reactive site region
of BPTI (P.sub.4-P.sub.4') have been shown to interact with
different serine proteinases, and it is generally recognized that
the N-terminal side of the reactive site (P) is energetically more
important than the P' C-terminal side (Perona et al., 1997, J.
Biol. Chem. 272, 29987-29990). In all, about 10-12 amino acid
residues in the inhibitor and 20-25 residues in the proteinase are
in direct contact in the formation of a stable proteinase-inhibitor
complex, and provide a buried area of 600-900 .ANG. (Janie et al.,
1990, J. Biol. Chem. 265, 16027-16030). While many proteins
structurally similar to BPTI, such as TFPI KD2 (Burgering et al.,
1997, J. Mol. Biol. 269, 395-407), APPI (Scheidig et al., 1997,
Protein Sci. 6, 1806-1824) and bikunin (Xu et al., 1998, J. Mol.
Biol. 276, 955-966), have been isolated and their three dimensional
structures determined, there are few studies that have assigned the
relative contribution of residues flanking the reactive site
residue in the formation of the proteinase-inhibitor complex and
their affect on inhibitory activity and specificity (Van Norstrand
et al., 1995, J. Biol. Chem. 270, 22827-22830; Castro et al., 1996,
Biochemistry 35, 11435-11446; Grzesiak et al., 2000b, J. Biol.
Chem. 275, 33346-33352).
[0080] In the case of TFPI-2, it is generally believed that its
first Kunitz-type domain, in a BPTI-like manner, harbors most of
its inhibitory activity, although no studies have definitively
shown that this domain is sufficient to mediate this activity. In
the present study, the complete first Kunitz domain of human TFPI-2
was expressed and purified, and its inhibitory activity towards
selected proteinases was compared with that of full-length TFPI-2
and BPTI. In addition, molecular modeling was employed to obtain
three-dimensional structural information on complexes of TFPI-2
KD1-plasmin, TFPI-2 KD1-trypsin and TFPI-2 KD1-factor VIIa in order
to identify residues in KD1 involved in its molecular recognition
of each proteinase. From this analysis, residues primarily
responsible for the interaction and proteinase specificity were
then selected for mutagenesis. Select amino acid residues on both
the N-terminal and C-terminal side of the reactive site residue
(P.sub.1) were substituted individually, and the effects of these
point-mutations on the proteinase specificity and inhibitory
activity were investigated.
Experimental Procedures
Materials
[0081] The chromogenic substrates H-D-Val-Leu-Lys-p-nitroanilide
(S-2251) and H-D-Ile-Pro-Arg-p-nitroanilide (S-2288) were purchased
from DiaPharma Group Inc (West Chester, Ohio, USA). Human plasmin
was purchased from Haematologic Technologies, Inc. (Essex Junction,
Vt., USA). Human recombinant factor VIIa, porcine trypsin and
bovine aprotinin (BPTI) were generously provided by Novo Nordisk
(Copenhagen, Denmark). Escherichia coli strain BL21(DE3)pLys and
pET19b expression vector were products of Novagen Inc. (Madison,
Wis.). The QuickChange.RTM. site-directed mutagenesis kit was
obtained from Stratagene (La Jolla, Calif.). YM3 ultrafiltration
membranes were purchased from Millipore (Bedford, Mass.).
His-Trap.RTM. columns were obtained from Amersham Biosciences Corp.
(Piscataway, N.J.). Novex 4-20% Tris-glycine polyacrylamide gels
were purchased from Invitrogen (Carlsbad, Calif.). Recombinant
human TFPI-2 (Sprecher et al., 1994, Proc. Natl. Acad. Sci. USA 91,
3353-3357), recombinant soluble tissue factor (Petersen et al.,
1996, Biochemistry 35, 266-272), and protein-A Sepharose-purified
anti-human TFPI-2 IgG (Iino et al., 1998, Arterioscler. Thromb.
Vasc. Biol. 18, 40-46) were prepared according to published
methods. All other reagents were the highest purity commercially
available.
Molecular Modeling
[0082] Three-dimensional structural information on complexes formed
between KD1 and plasmin, KD1 and trypsin, and KD1 and factor VIIa
was obtained using molecular modeling strategies. The
crystallographically-determined structures of factor VIIa-TF
inhibited with a BPTI mutant (Zhang et al., 1999, J. Mol. Biol.
285, 2089-2104; pdb code 1fak), factor VIIa-TF (Banner et al.,
1996, Nature 380, 41-46; pdb code 1dan), trypsin inhibited with
TFPI KD2 (Burgering et al., 1997, J. Mol. Biol. 269, 395-407; pdb
code 1tfx), the NMR determined structure of TFPI KD2 (Burgering et
al., 1997, J. Mol. Biol. 269, 395-407; pdb code 1adz), trypsin
inhibited with BPTI (Huber et al., 1974, J. Mol. Biol. 89: 73-101;
pdb code 2ptc), and plasmin (Wang et al., 1998, Science 281,
1662-1665; pdb code 1bml) served as templates in building these
models. Bulk solvent was excluded from the proteinase-inhibitor
complex and, accordingly, it was anticipated that hydrogen bonds
and ionic interactions that may play an important role in
specificity could be accurately evaluated. The protocols for
modeling these complexes have been described in detail elsewhere
(Bajaj et al., 2001, Thromb. Haemost. 86, 959-972). Briefly, the
relative positions of the inhibitor and proteinase domains were
maintained and adjustments were only made to the side chains.
Hydrophobic/van der Waals, hydrogen bonds, and ionic interactions
were observed between each proteinase-inhibitor complex. All of
these interactions were taken into consideration in evaluating each
proteinase-inhibitor complex, and it was assumed that all potential
hydrogen bond donors and acceptors would participate in these
interactions.
Expression and Purification of Wild-Type and Mutant Proteins
[0083] The first Kunitz-type proteinase inhibitor domain of human
TFPI-2 (KD1) and its mutants were overexpressed as N-terminal
His-tagged fusion proteins in Escherichia coli strain BL21(DE3)pLys
using the T7 promoter system (Studier et al., 1990, Methods
Enzymol. 185, 60-89). The recombinant plasmid derived from pET19b
bearing a decahistidine-tag leader sequence followed by an
enterokinase cleavage site and cDNA encoding the first
Kunitz-domain of TFPI-2 was prepared according to standard
procedures (Sambrook et al., 2001, Molecular Cloning: A laboratory
Manual, Third Edition, CSHL press). Using this recombinant vector
as a template, several other constructs containing the desired
point mutations were generated using a QuickChange.RTM.
site-directed mutagenesis kit according to the manufacturer's
instructions. Each recombinant construct was examined for in-frame
orientation, integrity and desired mutation by nucleic acid
sequencing. Wild-type and mutant His-tag KD1 preparations were
expressed in E. coli grown in rich media containing 100 mg/L
ampicillin, and induced at 37.degree. C. with 1 mM isopropyl
thiogalactopyranoside (IPTG) at mid log-phase (A.sub.600=0.6-0.8).
The overexpressed proteins were recovered from the cell lysates in
the faun of inclusion bodies following sonication in 50 mM Tris-HCl
(pH 8.0) containing 0.5 M NaCl, 5 mM 2-mercaptoethanol, and 10 mM
imidazole (buffer A). Inclusion bodies were recovered by high-speed
centrifugation (20,000.times.g for 60 minutes) and thoroughly
washed overnight at room temperature before solubilizing in buffer
A containing 6M guanidine hydrochloride. The solubilized inclusion
bodies were recovered by high speed centrifugation and were
filtered through 0.22.mu. Nalgene.RTM. filters before application
to His-Trap.RTM. column individually dedicated to each expressed
protein. His-Trap affinity columns were used in a Pharmacia FPLC
system and purification was carried out following the
manufacturer's protocol. Peak fractions were identified by
SDS-PAGE, pooled, and oxidatively refolded by initial dialysis
against 50 mM Tris-HCl (pH 8.0) containing 3 mM 2-mercaptoethanol,
followed by extensive dialysis against 50 mM Tris-HCl (pH 8.0).
[0084] The refolded proteins were purified to homogeneity by Mono Q
FPLC at room temperature. KD1 proteins were eluted from this column
in a linear NaCl gradient consisting of 50 mM Tris-HCl (pH 8) and
50 mM Tris-HCl (pH 8) containing 1 M NaCl. Peak fractions were
subjected to SDS-PAGE analysis, and pure fractions were pooled and
concentrated on YM-3 ultrafiltration membranes.
General Methods
[0085] The concentration of each purified KD1 protein was
determined by measuring its absorbance at 280 nm using calculated
values for E.sup.1% derived from its Tyr, Trp and Cys content (Gill
et al., 1989, Anal. Biochem. 182, 319-326). The concentration of
plasmin was provided by the supplier, whereas the concentrations of
all other proteins used in this study were determined according to
Bradford (1976, Anal. Biochem. 72, 248-254) using BSA as the
reference protein. SDS-PAGE was performed according to Laemmli
(1970, Nature 227, 680-685) using 4-20% polyacrylamide gradient
gels.
Trypsin and Plasmin Inhibition Assays
[0086] Trypsin and plasmin inhibition assays were performed as
described elsewhere (Petersen et al., 1996, Biochemistry 35,
266-272). Briefly, trypsin and plasmin were incubated with various
concentrations of inhibitor preparations for 15 minutes at
37.degree. C. in a 96-well microtitration plate. The chromogenic
substrate S-2251 was then added and residual amidolytic activity
was measured in a Molecular Devices UV.sub.max kinetic microplate
reader.
Inhibition Assay for Factor VIIa-Tissue Factor Amidolytic
Activity
[0087] Recombinant soluble human tissue factor (100 nM) and factor
VIIa (50 nM) were incubated in a TBS-BSA buffer/5 mM CaCl.sub.2 for
15 minutes at 37.degree. C. Following this incubation, aliquots
(100 .mu.l) were dispensed into a 96-well microtitration plate and
treated with serial dilutions of inhibitors dissolved in TBS
buffer. After 15 minutes of incubation, 30 .mu.l of S-2288 (final
concentration, 1 mM) was added to each well and the absorbance at
405 nm was determined as described earlier.
Inhibition Kinetics
[0088] The apparent inhibition constant, K.sub.i' was determined
using the non-linear regression data analysis program Ultrafitfv3.0
(Biosoft). Trypsin and plasmin inhibitory data were analyzed
according to the following equation for a tight-binding
inhibitor:
v.sub.i=v.sub.0[
(K.sub.i'+[I].sub.0+[E].sub.0).sup.2-4[I].sub.0[E].sub.0-(K.sub.i'+[I].su-
b.0-[E].sub.0)]/2[E].sub.0
where v.sub.i and v.sub.0 are the inhibited and uninhibited rates,
respectively, and [I].sub.0 and [E].sub.0 are the total
concentrations of inhibitor and enzyme, respectively. Factor
VIIa-tissue factor inhibition data, where K.sub.i>>[E].sub.0,
were analyzed according to the following equation:
v.sub.i=v.sub.0/(1+[I].sub.0/K.sub.i')
K.sub.i values were obtained by correcting for the effect of
substrate according to Bieth et al. (Bieth, 1984, Biochem. Med. 32,
387-397), where K.sub.i=K.sub.i'/(1+[S]/K.sub.m)
Results
Molecular Modeling and Selection of Mutations
[0089] Previous studies demonstrated that human TFPI-2 is a strong
inhibitor of plasmin and trypsin, and a relatively weak inhibitor
of the factor VIIa-tissue factor complex (Petersen et al., 1996,
Biochemistry 35, 266-272). The molecular basis of TFPI-2's
specificity for plasmin and trypsin relative to the serine
proteinase factor VIIa is unclear, but presumably involves residues
other than the P.sub.1 Arg in the first Kunitz-type domain of
TFPI-2, as well as residues in the active site region of the
proteinase. In order to address whether other residues in the
reactive site region of TFPI-2 may play a role in its inhibitory
potency and specificity, we employed a molecular modeling approach
to guide subsequent mutagenesis studies designed to provide
information on the functional importance of these residues. As our
preliminary data indicated that a recombinant preparation of the
first Kunitz-type domain of TFPI-2 (KD1) exhibited better
inhibitory activity in comparison to the intact parent molecule
(see below), we decided to model complexes of KD1 with plasmin,
trypsin and factor VIIa based on the crystal structure of BPTI and
each proteinase, respectively. A preliminary inspection of the
amino acid sequences surrounding the P.sub.1 residue in a number of
Kunitz-type inhibitors revealed highly conserved residues at the
P.sub.6, P.sub.1, P.sub.5' and P.sub.18' positions (FIG. 4), and
our molecular modeling studies thus initially focused on the
contributions of these residues in the formation of an
energetically stable complex between KD1 and the above proteinases.
In the model structures of these complexes, no unfavorable contacts
between atoms and no unnatural chiral centers were observed. In the
Ramachandran plot of the main-chain .phi.-.phi. angles, all of the
non-glycine residues are in the most favored or permissive regions.
Moreover, there are no gross steric clashes that preclude the
interaction of proteinases with KD1. For simplicity and
consistency, the residue numbering system employed for KD1 and each
proteinase is that of its linear sequence position. In addition, in
order to relate each proteinase residue number to its corresponding
position in the prototypical proteinase chymotrypsin, each
proteinase residue number is followed by its position in
chymotrypsin in braces, and is preceded by the letter "c". Finally,
the relationship between residues mutated in KD1 and their position
in BPTI is indicated in Table I. Note that the residues in KD1
differ by nine from BPTI; thus, residue 24 (P.sub.1 residue) in KD1
is equivalent to 15 in BPTI. For simplicity, KD1 numbering system
is used in this document.
TABLE-US-00001 TABLE I K.sub.i Values For The Inhibition Of
Selected Proteinases By Human TFPI-2, KD1, KD1 Point-Mutants and
BPTI. K.sub.i [nM] Plasmin Trypsin FVIIa-TF Inhibitor [30 nM] [50
nM] [50/100 nM] TFPI-2 9 21 1910 KD1 3 13 1640 D19A (D10A).sup.a
118 15 1960 Y20A (Y11A) 16 8 1350 G21D (G12D) 59 42 26000 R24Q
(R15Q) 48 296 55740 R24K (R15K) 0.85 8 8550 L26Q (L17Q) 29 162
53970 R29A (R20A) 12 52 3931 R29D (R20D) 261 4600 44600 R29K (R20K)
5 20 1115 F42A (F33A) 79 155 61186 BPTI 0.75 5 NI.sup.b
.sup.aNumber in parenthesis indicate BPTI numbering system
.sup.bNI, No Inhibition
[0090] In the KD1-proteinase complex, there is an interactive
hydrophobic patch and an internal hydrophobic patch in KD1 (FIGS.
5A and 5B). The plasmin-interactive hydrophobic interface is formed
by a number of residues in KD1 including Leu26, Leu27, Leu28, Leu43
and Tyr55. The residues Leu18, Tyr20, Tyr31, Phe42 and Tyr44 in KD1
are buried within and contribute to the formation of an internal
hydrophobic pocket. Within the interactive patch, Leu27 in KD1
interacts with Phe583{c37}, Met585{c39}, Phe587{c41} and C.sub.B of
Lys607{c61} in plasmin (FIGS. 5A and 5B). In addition, Leu28
interacts with Met585 {c39} in plasmin. Furthermore, the side chain
C.sub.D and C.sub.E of Lys607{c61} could make hydrophobic
interactions with C.sub.D1 and C.sub.E1 of Tyr55 in KD1 (FIG. 5A).
These flanking region interactions at the interface of plasmin and
KD1 exhibit a marked variability in structural complementarity when
compared to analogous interactions in KD1-trypsin (FIG. 6A) and
KD1-factor VIIa (FIG. 6B) complexes. In this regard, the
hydrophobic patch observed between KD1 and plasmin does not exist
with factor VIIa (FIG. 6B), whereas trypsin appears to have this
hydrophobic patch interaction (FIG. 6A). Tyr159{c151} in trypsin is
probably involved in hydrophobic interactions with Leu26 and Leu43
of KD1 as is evident from the KD1-trypsin complex. In addition,
Phe49{c41} in trypsin is positioned to interact with Leu27 of KD1.
We further propose that Lys68{c60} of trypsin may interact with
Tyr55 of KD1 and that the side-chain of Lys68{c60} in trypsin may
interact with Leu27 via hydrophobic interactions. Finally, there
are also main chain interactions between the carbonyl O of Pro22 in
KD1 and the amide N of Gly{c216} in serine proteinases, as well as
the amide N of Arg24 in KD1 and the carbonyl O of Ser{c214} in
serine proteinases. These interactions are common to a serine
proteinase interacting with Kunitz-type inhibitors (Janin et al.,
1990, J. Biol. Chem. 265, 16027-16030).
[0091] In addition to hydrophobic interactions, electrostatic
attraction/repulsion also plays an important role in forming and
stabilizing the KD1-proteinase complex (FIG. 5B). One of the
reactive site residues at the P.sub.6 position, Asp19, together
with Glu48 of the secondary loop, forms an acidic patch in KD1.
This acidic patch interacts with a basic patch in plasmin that
consists of Arg644{c98}, Arg719{c173}, and Arg767{c221}. Inasmuch
as this basic patch is not present in either trypsin or factor VIIa
(FIGS. 6A and 6B), we believe that Asp19 in KD1 enhances the
specificity of KD1 for plasmin through this electrostatic
interaction. Tyr20, the P.sub.5 residue, lines the hydrophobic
cavity of the internal hydrophobic patch of KD1 and contributes to
its structural stability. The following P.sub.4 residue, Gly21 is
in close proximity spatially to Asp19 and, as observed in the
structure N.sub.E2 of Gln738{c192} in plasmin, makes a hydrogen
bond with the backbone C--O of Gly21 in KD1. At the P.sub.3
position in KD1, Pro22 is involved in a turn and also fits into a
hydrophobic patch in plasmin, trypsin and factor VIIa. Pro22 also
sits in the S.sub.3/S.sub.4 site of the proteinase. Arg24, the
P.sub.1 residue, ion pairs with Asp735{c189} at the bottom of the
substrate binding pocket in plasmin and is further stabilized
through hydrogen bonding to Ser736{c190} O.gamma. and
Gly765{c219}O. Arg29, the highly conserved Arg/Lys at the P.sub.5'
of Kunitz-type inhibitors, makes hydrogen bonds with Glu606{c60} in
plasmin, and interacts with Tyr67{c59} in trypsin and Asp196{c60}
in factor VIIa. Finally, the conserved P.sub.18' residue, Phe42 is
located in a hydrophobic pocket with Tyr20, Leu18, Tyr31 and Tyr44
in KD1 and probably contributes to the stabilization of the KD1
inhibitory structure. Based on the above molecular modeling
studies, KD1 residues Asp19, Tyr20, Gly21, Arg24, Leu26, Arg29 and
Phe42 were selected for mutagenesis. A schematic model
representation of the human TFPI-2 KD1 is illustrated in FIG. 7,
and highlights residues mutated in this study at the P.sub.6,
P.sub.5, P.sub.4, P.sub.1, P.sub.2', P.sub.5' and P.sub.18'.
Preparation and Purification of Human TFPI-2 KD1 and Various KD1
Mutants
[0092] Wild-type and site-specific mutant preparations of human
TFPI-2 KD1 were overexpressed as His-tagged fusion proteins in E.
coli. The in-frame orientation, integrity and desired mutations in
the recombinant constructs were confirmed by nucleic acid
sequencing. Each of the recombinant KD1 preparations was expressed
and purified from 4 liters of LB broth following induction at
37.degree. C. with 1 mM IPTG. The KD1 preparations obtained from
inclusion bodies were solubilized in 6 M guanidine hydrochloride
and initially purified on a nickel-charged metal chelating column
(His-Trap.RTM.), and refolded by sequential dialysis in the
presence and absence of reducing agent. The partially purified and
refolded KD1 preparations consisted mainly of monomeric KD1
(.about.70%) with the remainder consisting of KD1 oligomers.
Monomeric KD1 was subsequently separated from oligomeric KD1 by
Mono Q FPLC. Each of the KD1 preparations migrated as a single band
with an average apparent molecular weight of 16 kDa in a denaturing
SDS-PAGE gel (FIG. 8). An average yield of 3 mg of purified KD1 was
obtained per liter of broth. For each KD1 preparation, the precise
molecular weight values were obtained from its amino acid
composition, and their mass concentrations were determined
spectrophotometrically at 280 nm using a calculated E.sup.1% value
based on its Trp, Tyr and Cys content (Gill et al., 1989, Anal.
Biochem. 182, 319-326).
Inhibitory Properties of Human TFPI-2 KD1 and Various KD1
Mutants
[0093] Recombinant KD1 exhibited stronger inhibitory activity
towards each of the three serine proteinases in comparison to the
eukaryotically-expressed recombinant full-length TFPI-2 molecule
(Table 1), providing strong evidence that the other two Kunitz-type
domains of TFPI-2 do not provide any significant effect on TFPI-2's
inhibitory properties and that post-translational modifications are
not essential for full expression of its inhibitory activity.
Wild-type KD1 inhibited plasmin amidolytic activity with roughly a
3-fold higher K.sub.i value than BPTI (Table 1), but was three-fold
more potent than full-length TFPI-2. On the other hand, KD1
exhibited approximately two-fold higher trypsin inhibitory activity
than full-length TFPI-2, but was two-fold less potent than BPTI
(Table 1). Wild-type KD1 inhibited factor VIIa-tissue factor
amidolytic activity with a comparable K.sub.i value to that of
full-length TFPI-2, while BPTI failed to show any inhibitory
activity towards this complex (Table 1). Extra amino acids
N-terminal to the mature protein, such as the His-tag region, had
little, if any, negative effect on its inhibitory activity. The
higher inhibitory activity of the first Kunitz-type domain of
TFPI-2 compared to full-length TFPI-2 in all likelihood is
attributed to its smaller size and/or flexibility.
[0094] The effect of mutations at the P.sub.6, P.sub.5, P.sub.4,
P.sub.1, P.sub.2', P.sub.5' and P.sub.18' are also listed in Table
1. An alanine substitution at the P.sub.6 position, Asp19, showed a
dramatic (.about.40-fold) loss of inhibitory activity towards
plasmin, but failed to show any significant loss of activity
towards trypsin and factor VIIa. From the molecular graphics model,
the most rational explanation for this effect is that Asp19
interacts with a basic patch in plasmin consisting of Arg644{c98},
Arg719{c173} and Arg767{c221}. As there are no corresponding basic
patches in trypsin or factor VIIa at these positions, the
interaction of Asp19 with the basic patch in plasmin appears to
confer KD1 with enhanced reactivity, and inhibitory potency,
towards plasmin. Mutagenesis of the neighboring P.sub.5 residue,
Tyr20, to Ala also had a significant negative effect on KD1
inhibition of plasmin, suggesting that this residue either
contributes towards the formation of the KD1-plasmin complex, or is
critical in maintaining the conformation of the KD1 reactive site
towards plasmin. Mutagenesis of Tyr20 to Ala, however, slightly
enhanced its ability to inhibit trypsin and factor VIIa (Table
1).
[0095] The residue at the P.sub.4 position, Gly21, also seems to
play a supportive role in the interaction of KD1 with proteinases
as shown earlier using BPTI mutants (Grzesiak et al., 2000b, J.
Biol. Chem. 275, 33346-33352). In this study, we mutated Gly21 to
aspartic acid in order to increase the acidic patch on KD1 and
enhance its interaction with the basic patch in plasmin, since
Gly21 is in close spatial proximity to Asp19. However, mutation of
Gly with Asp did not have the desired effect and this mutant lost
inhibitory activity towards all proteinases tested most probably
due to perturbation in the main-chain conformation of the KD1
reactive site. In this regard, the phi angle (.phi.) of Gly is
+111.degree. and the psi angle (.phi.) is -174.degree., which
places Gly21 in a region of the Ramachandran plot accessible only
to Gly residues (Creighton et al., 1987, J. Mol. Biol. 194, 11-22).
Accordingly, any other residue would conceivably alter the backbone
structure by changing the phi and psi angles resulting in an
altered main-chain conformation in the vicinity of Gly21.
[0096] The side chain of the P.sub.1 residue primarily dictates the
specificity of a proteinase inhibitor for its cognate proteinase.
Systematic substitution at this position in a number of inhibitors
revealed a large dynamic range of effects on its association with
different proteinases (Castro et al., 1996, Biochemistry 35,
11435-11446; Grzesiak et al., 2000b, J. Biol. Chem. 275,
33346-33352; Ponte et al., 1988, Nature 331, 525-52; Sprecher et
al., 1993, Biochemistry 32, 4481-4486; Wun et al., 1988, J. Biol.
Chem. 263, 6001-6004; Shimomura et al., 1997, J. Biol. Chem. 272,
6370-6376; Kawaguchi et al., 1997, J. Biol. Chem. 272, 27558-27564;
Kaumeyer et al., 1986, Nucleic Acids Res. 14, 7839-7850). The
glutamine substitution at the P.sub.1 site resulted in a decreased
inhibitory activity in KD1 (Table 1), as was observed with the
full-length R24Q TFPI-2 mutant (Kamei et al., 1999, Thromb. Res.
94, 147-152). As observed in the model structure of KD1 with
plasmin, trypsin and factor VIIa, the Arg24 in KD1 forms a salt
bridge, in addition to two hydrogen bonds, with the carbonyl
backbone of Asp{c189} and Gly{c219} in order to stabilize the
complex. Mutation of Arg to Gln eliminates interaction with the
S.sub.1 site residue Asp{c189} due to the shorter side chain and
its lack of charge. Lysine substitution at this position restores
the inhibitory activity of KD1, and the lower K.sub.i values
obtained with R24K KD1 against plasmin and trypsin could be the
result of an ionic interaction of the protonated amino group with
the carboxylate group of Asp{c189}, as well as water-mediated
hydrogen bonding between the carbonyl group of Gly{c219} and the
hydroxyl group of Ser{c190} with the P.sub.1 Lys amino group. In
view of this potential bonding pattern, it is curious as to why the
inhibitory activity of R24K KD1 for factor VIIa was reduced
approximately five-fold, inasmuch as factor VIIa also has a
Ser326{c190}. The reason for its reduced inhibitory activity
against factor VIIa is not known at this point, but may be due
other residues in the substrate binding pocket of factor VIIa as
opposed to that of plasmin and trypsin.
[0097] As mentioned above, KD1 contains a cluster of hydrophobic
Leu residues at the P.sub.2'-P.sub.4' region that interacts with a
hydrophobic patch in plasmin, trypsin and factor VIIa. In order to
disrupt this cluster, Leu26 was substituted with the highly
hydrophilic residue, glutamine. This L26Q mutation resulted in at
least a 10-fold reduction in inhibitory potency of KD1 towards each
of the proteinases tested (Table 1) and underscores the importance
of this hydrophobic interaction in the inhibitory mechanism of KD1.
Leu26 is part of a hydrophobic patch and interacts with Leu43 and
Leu28 of KD1. Leu26 also has the potential to have hydrophobic
interactions with Gln738{c192} in plasmin, with C.sub.D and C.sub.G
of Gln200{c192} in trypsin, and with C.sub.D and C.sub.G of
Lys328{c192} in factor VIIa. Thus, changing this residue to a
non-hydrophobic residue such as Gln will disrupt these interactions
and be disruptive for each proteinase.
[0098] Virtually all Kunitz-type domains studied have a highly
conserved Lys/Arg at the P.sub.5' position (FIG. 4), and three
point mutants were made at this position. In plasmin, Glu606{c60}
makes hydrogen bonds with Arg29 in KD1, whereas Tyr67{c59} and
Asp196{c60} in trypsin and factor VIIa, respectively, interact with
this residue. Substitution of Arg29 with alanine resulted in a
marginal loss of inhibitory activity towards all three proteinases
(Table 1), whereas substitution with aspartic acid presumably
caused charge repulsion, as well as disruption of hydrogen bonds,
with a major effect on K.sub.i (Table 1). Mutation of Arg29 with
lysine could possibly preserve the hydrogen bonding observed with
Arg and resulted in minor changes in K.sub.i (Table 1). While the
P.sub.5' Arg/Lys residue is important in the inhibitory mechanism
of KD1, it does not appear to be a major determinant in KD1
specificity.
[0099] Finally, as expected, mutagenesis of the highly conserved
Phe42 at the P.sub.18' position with alanine resulted in similar
losses of inhibitory activity towards all three proteinases (Table
1), presumably by disruption of the internal hydrophobic core in
KD1 formed by Phe42, Tyr20, Leu18, Tyr31, Tyr44 and the side chain
of Arg29.
Discussion
[0100] In the present study, we have expressed and purified the
human TFPI-2 Konitz-type domain 1 (KD1), and compared its
inhibitory activity towards plasmin, trypsin and the factor
VIIa-tissue factor (VIIa-TF) complex to that of full-length TFPI-2,
BPTI, and nine human TFPI-2 KD1 constructs with mutations in the
reactive site region (P.sub.6-P.sub.5'). The isolated TFPI-2 KD1
exhibited stronger inhibitory activity towards these proteinases in
comparison to intact TFPI-2. Alanine substitution at the P.sub.6
(D19A) and the P.sub.5 (Y20A) positions had a marginal effect on
its inhibitory activity towards trypsin and VIIa-TF, but exhibited
a marked decrease in activity towards plasmin. Substitution of
aspartic acid for alanine was particularly deleterious to plasmin
inhibition by KD1 and molecular modeling studies revealed that this
was in all likelihood due to the modulation of an ionic interaction
between an acidic patch in KD1, formed by Asp19 and Glu39, and a
basic patch unique to plasmin composed of Arg644{c98}, Arg719{c173}
and Arg767{c221}. Thus, Asp19 and Tyr20 in KD1 appear to play a
major role in the specificity of TFPI-2 for plasmin. In contrast,
point mutations at the P.sub.4(G21D), P.sub.1(R24Q), P.sub.2'
(L26Q) and P.sub.5' (R29A) positions all exhibited substantial
decreased inhibitory activity towards all of these proteinases. The
importance for a highly conserved basic residue (Arg/Lys) at the
P.sub.5' position was evident from a substantial loss of inhibitory
activity in the R29D KD1, presumably through the loss of either a
stabilizing ionic interaction between Arg29 and Glu606/Asp196{c60}
in plasmin/VIIa, or by hydrogen bonding of Arg29 to Tyr67{c59} in
trypsin. Finally, mutation of a highly conserved phenylalanine at
the P.sub.18' position (F42A) revealed the importance of this
residue in the stabilization of the reactive site structure through
internal hydrophobic interactions.
[0101] A lysine substitution at the P.sub.1 position (R24K) in KD1
significantly increased its inhibitory activity towards both
plasmin and trypsin, making it essentially as effective as BPTI
towards these proteinases. In sharp contrast, R24K KD1
paradoxically exhibited approximately a five-fold reduction in
inhibitory activity towards VIIa-TF, a somewhat surprising result
in consideration of the fact that VIIa contains a Ser326{c190} that
forms an additional water-mediated hydrogen bond with the
protonated 6-amino group in lysine (Bode et al., 2000, Biochim.
Biophys. Acta 1477, 241-252) and that VIIa forms a stable
interaction with the first Kunitz-type domain of TFPI through its
interaction with a P.sub.1 lysine residue. On the other hand, BPTI
also contains a lysine in its P.sub.1 position and failed to
inhibit VIIa-TF (Table 1), suggesting that VIIa prefers Arg P.sub.1
residues and that other residues in the reactive site region of
TFPI-2 KD1 somehow synergistically enhance VIIa inhibition, as has
been shown for a BPTI mutant (Zhang et al., 1999, J. Mol. Biol.
285, 2089-2104).
[0102] Of potential clinical relevance, R24K KD1 exhibited
essentially the same inhibitory activity as BPTI, which is widely
used as a plasmin inhibitor during surgery but, being of bovine
origin, precipitates episodes of severe anaphylaxis on some
occasions (0.5-1%). In this context, these studies may provide a
template for the design of improved Kunitz-type serine proteinase
inhibitors with considerable therapeutic potential. In this regard,
our laboratory, and other laboratories, have demonstrated the
importance of serine proteinase inhibition in the growth,
migration, angiogenesis and metastasis of a variety of human tumors
(Chand et al., 2004, Blood 103, 1069-1077; Epub 2003 Oct. 2,
Example III; Soff et al., 1995, J. Clin. Invest. 96, 2593-2600;
Konduri et al., 2001, Oncogene 20, 6938-6945; Kobayashi et al.,
2004, Cancer 100, 869-877).
[0103] These tumor properties are presumably mediated in large part
by proteinases such as plasmin and/or trypsin IV (Cottrell et al.,
J. Biol. Chem. 279: 13532-13539, 2004), and the secretion of
inhibitory TFPI-2 by these tumors markedly inhibits their growth
and metastasis in animal models (Chand et al., 2004, Blood 103,
1069-1077; Epub 2003 Oct. 2; Example III; Konduri et al., 2001,
Oncogene 20, 6938-6945). Moreover, in preliminary studies, we have
shown that hexahistidine tagged-human KD1 exhibits dose-dependent
inhibition of angiogenesis in a commercially available in-vitro
human endothelial cell angiogenesis assay (see Example VI). In
addition, intravenous administration of human KD1 to
ovalbumin-sensitized asthmatic mice resulted in a significant
decrease in the number of airway macrophages and lymphocytes
relative to vehicle-treated asthmatic mice, suggesting that KD1
inhibits the proteinase-mediated transepithelial migration of
mononuclear cells from the bloodstream to the airways (see Example
IV). Accordingly, administration of KD1, or a more potent KD1
mutant, may conceivably regulate these and other pathological
processes dependent upon the activity of serine proteinases. In
addition, the availability of human KD1 generated in these studies
will facilitate X-ray crystallographic studies of either this
inhibitor alone or in complex with serine proteinases, and these
studies are currently ongoing in our laboratories.
[0104] In summary, these studies provide the initial, definitive
evidence that the first Kunitz-type domain of human TFPI-2 contains
all the structural elements for the inhibition of a variety of
serine proteinases, and underscores the importance of critical
residues in its P.sub.6-P.sub.5' position in its inhibitory
activity towards these proteinases. In addition, these studies
reveal the importance of the Asp and Tyr residues at the P.sub.6
and P.sub.5 positions in the reactive site region of KD1 that
appears to confer specificity for plasmin inhibition by TFPI-2.
Example II
Purification of R24K-KD1
Materials
[0105] Escherichia coli strain BL21(DE3) and pET28a expression
vector were products of Novagen Inc. (Madison, Wis.). The
QuickChange.RTM. site-directed mutagenesis kit was obtained from
Stratagene (La Jolla, Calif.). YM3 ultrafiltration membranes were
purchased from Millipore (Bedford, Mass.). His-Trap.RTM. columns
were obtained from Amersham Biosciences Corp. (Piscataway, N.J.).
Novex 4-20% Tris-glycine polyacrylamide gels were purchased from
Invitrogen (Carlsbad, Calif.). All other reagents were the highest
purity commercially available.
Expression and Purification of R24K-KD1
[0106] The R24K mutant of the first Kunitz-type domain of human
TFPI-2 (KD1) was overexpressed as N-terminal histidine (His)-tagged
fusion protein in Escherichia coli strain BL21(DE3) using the T7
promoter system. The recombinant plasmid derived from pET28a
bearing a hexa-histidine leader sequence followed a thrombin
cleavage site and cDNA encoding the first Kunitz-domain of TFPI-2
was prepared according to standard procedures (Sambrook et al.,
2001, Molecular Cloning: A laboratory Manual, Third Edition, Cold
Spring Harbor Laboratory Press, Cold Spring Harbor, Me.). Using
this recombinant vector as a template, a R24K-KD1 mutant construct
was generated using a QuickChange.RTM. site-directed mutagenesis
kit according to the manufacturer's instructions. The recombinant
construct was examined for in-frame orientation, integrity and
desired mutation by nucleic acid sequencing. The 6-His-tag R24K-KD1
fusion protein was expressed in E. coli grown in rich media
containing 100 mg/L ampicillin (Sigma Chemical Company, St. Louis,
Mo.), and induced at 37.degree. C. with 1 mM isopropyl
thiogalactopyranoside (IPTG, Gold Biotechnologies Inc., St. Louis,
Mo.) at mid log-phase (A.sub.600=0.4-0.7).
[0107] The induced cells were harvested and lysed using a
lysozyme-nucleotidase mix, 0.2% Lysozyme (Sigma Chemical Company,
St. Louis, Mo.), 20 .mu.g/ml DNase I (Sigma) & 20 .mu.g/ml
RNase A (Sigma Chemical Company, St. Louis, Mo.) in 10 mM Tris-HCl
(pH 7.5) containing 150 mM NaCl, 1 mM MgCl.sub.2, 1 mM PMSF. Cell
lysis was carried out at room temperature for 2 hour and the lysate
was subjected to centrifugation (20000.times.g for 15 minutes). The
cell pellet was then resuspended in a detergent solution, 3%
Igepal.RTM. CA-630 (MP Biochemicals LLC, Aurora, Ohio) in 10 mM
Tris-HCl (pH 7.5) and 1 mM EDTA, sonicated at 50% power
(Sonicator.RTM., Heat Systems Ultrasonic Inc., W-380 model) and
inclusion bodies were collected by centrifugation (20000.times.g
for 15 minutes). The inclusion bodies were then washed twice with
water following brief sonication and centrifugation (20000.times.g
for 15 minutes). The highly enriched inclusion bodies were then
solubilized overnight in 50 mM Tris-HCl (pH 8.0) containing 7 M
urea, 0.5 M NaCl and 10 mM 2-mercaptoethanol. The suspension was
centrifuged at 20000.times.g for 3 hour, the supernatant was
filtered (0.2.mu. filters) and subsequently loaded onto a
nickel-charged His-Trap column (Amersham Bioscience, Piscataway,
N.J.). The column was washed with the equilibration buffer (50 mM
Tris-HCl (pH 8.0) containing 7 M urea, 0.5 M NaCl and 10 mM
2-mercaptoethanol), followed by equilibration buffer containing 25
mM imidazole. The 6-His-Tag R24K-KD1 fusion protein was eluted from
the column in equilibration buffer containing 500 mM imidazole.
[0108] The His-Trap purified protein was reduced by the addition of
50 mM dithiothreitol (Sigma Chemical Company, St. Louis, Mo.). This
solution was incubated overnight with rocker-shaking at room
temperature and then diluted to a concentration of .about.0.5 mg/ml
in 50 mM Tris-HCl (pH 9.5) containing 6 M urea and 0.02% azide, and
dialyzed against 20 volumes of the same buffer at room temperature.
The refolding was then carried out by dialyzing against 50 mM
Tris-HCl (pH 9.0) containing 0.3 M NaCl, 2 M urea, 2.5 mM GSH, 0.5
mM GSSG and 0.02% azide (buffer A). The dialysis was performed for
48 hour at 4.degree. C. The sample was then dialyzed against fresh
buffer A for another 48 hour at 4.degree. C. The solution was then
dialyzed at 4.degree. C. against 50 mM Tris-HCl (pH 9.0) containing
1 M urea followed by extensive dialysis against 50 mM Tris-HCl (pH
9.0) at 4.degree. C.
[0109] The refolded protein solution was then filtered (0.2.mu.
filters) and applied to a Q-Sepharose (Pharmacia Biotech) column
equilibrated at 4.degree. C. with 50 mM Tris-HCl (pH 9.0). The
protein was eluted from the column using a linear 0-1 M NaCl
gradient and the fractions were analyzed on SDS-PAGE. The
R24K-KD1-containing fractions were pooled and digested with human
thrombin (Kisiel et al., Blood. 1985; 66(6):1302-8)) at a 1:1000
enzyme: substrate molar ratio for 6 hour at room temperature. The
digestion was confirmed by SDS-PAGE analysis of temporal aliquots.
His-Tag-free R24K-KD1 preparations were then applied on His-Trap
columns to remove the hexa-histidine peptides followed by
SP-Sepharose (Pharmacia Biotech) chromatography equilibrated with
50 mM IVIES (pH 6.0) buffer, to remove traces of thrombin. The
pure, His-Tag-free R24K-KD1 preparations were then dialyzed
extensively against 20 mM Tris-HCl (pH 7.5), concentrated to >10
mg/ml (Amicon Ultra-15, 5000 MWCO, Millipore), and stored at
-80.degree. C. Each batch preparation was characterized with
respect to protein concentration (A.sub.280), purity (SDS-PAGE
analysis) and inhibition kinetics as described in Example I (see
also Chand et al., J. Biol. Chem. 2004; 279(17):17500-7; Epub 2004
Feb. 16. Erratum in: J Biol. Chem. 2004; 279(23):24906).
Example III
The Effect of Human Tissue Factor Pathway Inhibitor-2 on the Growth
and Metastasis of Fibrosarcoma Tumors in Athymic Mice
Summary
[0110] Human tissue factor pathway inhibitor-2 (TFPI-2) is a
matrix-associated Kunitz inhibitor that inhibits the plasmin and
trypsin-mediated activation of zymogen matrix metalloproteinases
involved in tumor progression, invasion and metastasis. To directly
assess its role in tumor growth and metastasis in-vivo, we
stably-transfected HT-1080 fibrosarcoma cells expressing either
fully active wild-type human TFPI-2 (WT) or inactive R24Q TFPI-2
(QT), and examined their ability to form tumors and metastasize in
athymic mice in comparison to mock-transfected cells (MT). MT and
QT fibrosarcoma tumors grew 2-3 times larger than WT tumors. Tumor
metastasis was confined to the lung and was observed in 75% of mice
treated with either MT- or QT-cells whereas only 42% of mice
treated with WT-cells developed lung metastases. Real time
quantitative RT-PCR analyses of each tumor group revealed 3-6-fold
lower levels of murine vascular endothelial growth factor gene
expression in WT tumors in relation to either MT or QT tumors.
Comparative tumor gene-expression analysis revealed that several
human genes implicated in oncogenesis, invasion and metastasis,
apoptosis and angiogenesis had significantly altered levels of
expression in WT-tumors. Our collective data demonstrate that
secretion of inhibitory TFPI-2 by a highly metastatic tumor cell
markedly inhibits its growth and metastasis in-vivo by regulating
pericellular ECM remodeling and angiogenesis.
Introduction
[0111] Proteolytic degradation of the extracellular matrix (ECM) is
considered to be an essential step for malignant cells to invade
and metastasize to distant tissues (Dano et al., Adv. Cancer Res.
1985; 44:139-239; Mignatti et al., Physiol. Rev. 1995; 73:161-195).
Proteinase inhibitors capable of protecting the ECM from
degradation by tumor-derived proteinases could potentially find
utility as therapeutic agents for blocking tumor metastasis. Human
tissue factor pathway inhibitor-2 (TFPI-2) is a Kunitz-type serine
proteinase inhibitor synthesized and secreted into the ECM by
endothelial cells, smooth muscle cells, fibroblasts, keratinocytes
and urothelium (lino et al., Arter. Thromb. Vasc. Biol. 1998;
18:40-46; Herman et al., J. Clin. Invest. 2001; 107:1117-1126; Rao
et al., Arch. Biochem. Biophys. 1995; 104: 311-314; Rao et al., J.
Invest. Dermatol. 1995; 104:379-383; Deng et al., Proc. Natl. Acad.
Sci. USA 2001; 98:154-159). TFPI-2 readily inhibits trypsin,
plasmin, chymotrypsin, cathepsin G, plasma kallikrein and the
factor VIIa-tissue factor complex, but not urokinase-type
plasminogen activator (uPA), tissue-type plasminogen activator or
thrombin (Sprecher et al., Proc. Natl. Acad. Sci. USA 1994;
91:3353-3357; Petersen et al., Biochemistry 1996; 35:266-272;
Miyagi et al., J. Biochem. 1994; 116:939-942; Rao et al., Arch.
Biochem. Biophys. 1996; 335:45-52). TFPI-2 presumably inhibits
these proteinases through an arginine residue (R24) in its first
Kunitz-type domain, as an R24Q TFPI-2 mutant lost >90% of its
inhibitory activity towards trypsin, plasmin and the factor
VIIa-tissue factor complex (Kamei et al., Thromb. Res. 1999;
94:147-152). TFPI-2 also strongly inhibited the trypsin or
plasmin-mediated activation of promatrix metalloproteinases
proMMP-1 and proMMP-3, and suppressed production of active MMP-2 in
HT-1080 cells stably-transfected with the TFPI-2 expression vector
(Rao et al., Biochem. Biophys. Res. Commun. 1999; 255:94-99; Izumi
et al., FEBS Lett. 2000; 481:31-36). In addition, TFPI-2 expression
is upregulated in human atherosclerotic coronary arteries in
comparison to normal, healthy arteries (Crawley et al.,
Arterioscler. Thromb. Vasc. Biol. 2002; 22:218-224). Thus,
ECM-associated TFPI-2 may play a pivotal role in the regulation of
ECM remodeling, a process essential for tumor invasion and
metastasis.
[0112] Given the inhibitory spectrum of TFPI-2, as well as our
previous finding that TFPI-2 inhibited the degradation of
fibroblast-derived ECM and Matrigel invasion by the highly invasive
HT-1080 fibrosarcoma cell in a dose-dependent fashion (Rao et al.,
Int. J. Cancer 1998; 75:749-756), we hypothesized that expression
of TFPI-2 by HT-1080 cells would markedly reduce its invasive and
metastatic properties in an animal model. Since HT-1080 cells do
not constitutively synthesize TFPI-2 (Rao et al., Int. J. Cancer
1998; 75:749-756), we prepared stably-transfected HT-1080 cells
expressing high concentrations of wild-type human TFPI-2. We
demonstrate that, in athymic mice, HT-1080 cells expressing
wild-type TFPI-2 produce considerably smaller subcutaneous tumors
and exhibited a lower metastatic rate in comparison to
mock-transfected HT-1080 cells. Furthermore, HT-1080 cells stably
transfected with an expression vector coding for an inactive mutant
of TFPI-2, R24Q TFPI-2, produced tumors in size and metastatic rate
similar to mock-transfected HT-1080 cells, providing strong
evidence that the ability of TFPI-2 to reduce tumor size and
metastasis correlated with its serine proteinase inhibitory
activity.
Materials and Methods
Materials
[0113] The murine myeloma cell line P3X63Ag8U.1 (P3U1) and the
human fibrosarcoma cell line HT-1080 were obtained from American
Type Tissue Culture Collection (Rockville, Md.). Minimum essential
medium Eagle (EMEM), non-essential amino acid solution,
trypsin/EDTA solution, RPMI-1640, TMBZ
(3,3',5,5'-tetramethyl-benzidine), and avidin-peroxidase were from
Sigma Chemical Company (St. Louis, Mo.). Lipofectamine plus
reagent, sodium pyruvate, penicillin-streptomycin, and PBS were
obtained from Gibco BRL Life Technologies, (Rockville, Md.). pcDNA3
vector and proteinase K were obtained from Invitrogen (Carlsbad,
Calif.). 5'-bromo-2'-deoxyuridine (BrdU) and monoclonal antibody to
BrdU were obtained from Amersham Pharmacia Biotech (Piscataway,
N.J.). Histomouse.TM.-SP bulk kit was purchased from Zymed
Laboratories (South San Francisco, Calif.). ApopTag.RTM.-Peroxidase
In-Situ Apoptosis Detection Kit was obtained from Serological
Corporation (Norcross, Ga.). The TaqMan.RTM. RT reagent kit and the
SYBR.RTM. Green Master Mix were obtained from Applied Biosystems
(Foster City, Calif.). Recombinant human TFPI-2 was purified as
described (Sprecher et al., Proc. Natl. Acad. Sci. USA 1994;
91:3353-3357). All other reagents used were the highest quality
commercially available.
Antibodies
[0114] Rabbit anti-human TFPI-2 IgG was prepared as described (Iino
et al., Arter. Thromb. Vasc. Biol. 1998; 18:40-46). Murine
monoclonal antibodies against human TFPI-2 were prepared as
follows. Six-week-old female Balb/c mice were injected
intraperitoneally (IP) on day 0 with 50 .mu.g recombinant TFPI-2
suspended in 50 .mu.l of a PBS/Freund's Complete Adjuvant emulsion.
Subsequent injections containing 50 .mu.g of TFPI-2 and Freund's
Incomplete Adjuvant were administered IP on days 14 and 35. Mice
were given an intravenous boost on days 49, 53 and 56, and
sacrificed on day 59. One mouse expressing the highest serum titer
(>10.sup.5) of anti-TFPI-2 antibodies was sacrificed and its
splenocytes fused with P3X63Ag8U.1 myeloma cells. Fusion and
hybridoma selection were optimized using standard methodology (Lane
et al., Cancer Epid. Biomark. Prey. 2002; 11:809-814). Hybridomas
were cultured for seven days and their supernatants screened for
antibodies to TFPI-2 by ELISA. Wells considered positive
(A.sub.405>1) were weaned from HAT supplement over 7-10 days,
subcloned by limiting dilution, and grown in pristane-primed mice
to generate ascites fluid. Monoclonal antibodies to human TFPI-2
(SK8, SK9) were isolated from ascites fluid using Hi Trap.RTM.
rProtein A affinity columns.
Cell Culture and Transfection
[0115] HT-1080 cells were cultured in 6% CO.sub.2-94% air and 96%
humidity at 37.degree. C. EMEM supplemented with 10% bovine calf
serum (Hyclone, Logan, Utah), sodium pyruvate, nonessential amino
acids, L-glutamine, and penicillin-streptomycin. The human TFPI-2
(Sprecher et al., Proc. Natl. Acad. Sci. USA 1994; 91:3353-3357)
and R24Q TFPI-2 (Kamei et al., Thromb. Res., 1999, 94:147-152) cDNA
were directionally subcloned into the EcoRI site of the pcDNA3
expression vector and the recombinant constructs transfected into
HT-1080 cells using the Lipofectamine Plus reagent according to the
manufacturer's instructions. Selection of transfected cells with
0.6 mg/ml G418 sulfate (Clontech, Palo Alto, Calif.) was initiated
48 hrs post-transfection and resistant colonies were cloned thrice
by limiting dilution, screened for TFPI-2 expression by ELISA, and
expanded. The expression levels of wild-type and R24Q TFPI-2 in
stably-transfected cells were assessed over a six week period in
the presence and absence of G418.
Cell Proliferation
[0116] Transfected HT-1080 cells were plated in duplicate at a
density of 1.times.10.sup.5 cells/well in a six-well plate. Every
seven days, for a total of 42 days, the cells were trypsinized,
counted, and replated at the same seeding density.
Human TFPI-2 ELISA
[0117] The concentration of wild-type and R24Q human TFPI-2 antigen
in stably-transfected HT-1080 cell supernatants was determined by
ELISA using monoclonal antibody SK9 and biotinylated monoclonal
antibody SK8. In this procedure, 96-well microtitration plates were
coated overnight at 4.degree. C. with 100 .mu.l/well of 50 mM
carbonate buffer (pH 9.6) containing 10 .mu.g/ml SK9. After washing
the plate three times with TBS/0.05% Tween 20, each well was
blocked with 200 .mu.l of TBS/1% gelatin/0.02% NaN.sub.3 at
37.degree. C. for 2 hours. Following five washes with TBS/Tween,
1000 samples were added to each well and allowed to incubate at
37.degree. C. for 2 hours. The plate was then washed five times
with TBS/Tween and 100 .mu.l of biotinylated SK-8 (100 ng/ml in
TBS/0.1% BSA) was added to each well. After 2 hours incubation at
37.degree. C., the plate was washed five times with TBS/Tween and
subsequently treated with 10 .mu.l of diluted peroxidase-conjugated
avidin for 1 hour. After washing with TBS/Tween, each well was
treated with 100 .mu.l of tetramethyl benzidine solution. Following
a suitable color development, the reaction was stopped by the
addition of 1 NH.sub.2SO.sub.4 (100 .mu.l) and the absorbance
measured at 450 nm. The concentration of TFPI-2 in test samples was
interpolated from a linear standard curve (linear range 6-200 ng
TFPI-2) relating A.sub.450 and known concentrations of recombinant
human TFPI-2.
Tumor Growth and Metastasis
[0118] All animal procedures were approved by the University of New
Mexico Health Sciences Center Laboratory Animal Care and Use
Committee. Thirty-six, six week old Balb/c SCID male mice, obtained
from Charles River Laboratory (Frederick, Md.) through the NCI
Contract Animal Program, were fed and watered ad libitum. The mice
were divided into three groups of twelve, and each mouse was
injected 5.times.10.sup.6 HT-1080 cells subcutaneously (SQ). Group
I was administered mock-transfected HT-1080 cells (MT), group II
with wild-type TFPI-2 transfected HT-1080 cells (WT), and group III
with R24Q TFPI-2 transfected HT-1080 cells (QT). The subcutaneous
growth of tumors was readily visible, and the volume
(0.5.times.length.times.width.sup.2) of each tumor was measured
externally by a tumor caliper. Five weeks post-injection, each
mouse received an intraperitoneal injection of BrdU (100 .mu.g/g
body mass) and was sacrificed 3 hrs later by CO.sub.2 narcosis. At
sacrifice, the mice were weighed, and visible tumors and several
organs were aseptically removed for further analyses.
Tissue Processing
[0119] Harvested tumors and organs were formalin-fixed and
paraffin-embedded using standard procedures. The organ tissues were
visually inspected for the presence of metastatic tumors throughout
the procedure. The embedded organ and tumor tissues were sectioned
(5.mu.) for subsequent hematoxylin and eosin (H&E) staining and
further analyses.
Immunohistochemical Detection of TFPI-2
[0120] Sections were deparafinnized with xylene, rehydrated in a
graded series of ethanol, and washed in PBS for immunohistochemical
staining. Expression of wild-type or R24Q TFPI-2 was determined
using rabbit anti-human TFPI-2 IgG and detected using the
Histomouse.TM.-SP Bulk kit according to the manufacturer's
instructions. Briefly, rehydrated slides were incubated with 3%
H.sub.2O.sub.2 to quench endogenous peroxidase activity, blocked,
incubated overnight (4.degree. C.) with antibody (1:1000 dilution
in PBS), followed by incubation with a biotinylated secondary
antibody, developed and counterstained with hematoxylin.
Detection of BrdU-Labeled and Apoptotic Cells
[0121] Tumor sections were processed as described above with an
additional step of trypsin (1 .mu.g/.mu.l) treatment after
quenching. The cells were probed by incubation with primary
anti-BrdU antibody (1:10 dilution) in nuclease solution. The
apoptotic cells in sections were detected by TUNEL staining using
the in-situ apoptosis detection kit (Apoptag.RTM. Peroxidase Kit)
according to the manufacturer's instructions. Briefly, after
deparaffinization, the sections were treated with proteinase K (20
.mu.g/ml) for 15 min at room temperature and blocked. The sections
were then treated with TdT enzyme for 60 min at 37.degree. C.
Anti-digoxigenin peroxidase-conjugate was applied for 30 min at RT,
and was detected with the aforementioned substrate-chromogen
solution. BrdU-labeled and TUNEL-positive cells were determined by
counting five randomly-chosen areas (100.times.) in each section
and averaged from three sections.
Microdissection and DNA Amplification
[0122] The cells from sections were microdissected and cellular DNA
purified as described (Bernstein et al., Cancer Epid. Biomark.
Prev. 2002; 11:809-814). For each group, three 5.mu. sections were
deparaffinized and air dried. Under a dissecting microscope, the
regions of interest were microdissected and collected. Fixed
control mouse stomach and lung cells were also processed similarly.
The microdissected tissue was lysed overnight at 50.degree. C. in
50 .mu.l of buffer containing 50 mM Tris-HCl (pH 8.5)/1 mM
EDTA/0.5% Tween 20/200 .mu.g/ml proteinase K, followed by
proteinase K inactivation at 95.degree. C. (10 minutes). The
cellular DNA obtained was ethanol precipitated, washed, air-dried
and redissolved in 10 .mu.l of ADW. An aliquot (3 .mu.l) of each
was analyzed for human mitochondrial DNA (mt DNA) and the
recombinant vector construct (rvcDNA) by PCR. The amplification of
human mt DNA (1071 by fragment) utilized a forward primer (GCT ATT
ACC TTC TTA TTA TTT ACC; SEQ ID NO:23) and reverse primer (GTG CGA
TGA GTA GGG GAA GG; SEQ ID NO:24). For the amplification of rvcDNA
(700 by fragment), a forward T7 primer (TAA TAC GAC TCA CTA TAG GG;
SEQ ID NO:25) and a TFPI-2-specific reverse primer (GCC TCG AGT TAA
AAT TGC TTC TTC CGA TA; SEQ ID NO:26) were employed. The
thermocycling profile was set as 5 minutes of initial denaturation
at 94.degree. C., followed by 39 cycles of denaturation (94.degree.
C. for 30 seconds), annealing for 1 minute (54.degree. C. for
rvcDNA; 57.degree. C. for human mtDNA), and elongation (72.degree.
C. for 2 minutes). The reaction products were electrophoresed in a
1.2% agarose gel along with appropriate DNA markers.
RNA Isolation
[0123] Total RNA was isolated from snap-frozen tumor samples
(100-150 mg) using an RNeasy RNA extraction kit (Qiagen,
Chatsworth, Calif.), according to the manufacturer's
recommendation. Purified RNA samples were stored at -80.degree. C.
in 100 .mu.l of DEPC-treated water. An aliquot of each RNA
preparation was analyzed and quantitated using the RNA 6000 Nano
assay kit in an Agilent Technologies 2100 Bioanalyzer.
VEGF Expression: Real Time Quantitative RT-PCR
[0124] A two-step real time quantitative RT-PCR analysis was
performed using a SYBR.RTM. Green-dye based assay in an ABI
Prism.RTM. 7000 Sequence Detection System according to the
manufacturer's instructions. Total RNA (300 ng) from each sample
was reverse-transcribed using random hexamer primers (TaqMan.RTM.
RT reagents kit). Primers targeting the angiogenesis marker murine
VEGF and murine GAPDH, an internal control, were designed using
Primer Express software. The primers selected for sense and
antisense strand respectively are; mouse VEGF cDNA (GenBank
accession number S38083): TTACTGCTGTACCTCCACC (SEQ ID NO:27) and
ACAGGACGGCTTGAAGATG (SEQ ID NO:28); mouse GAPDH cDNA (GenBank
accession number M32599): AACGACCCCTTCATTGAC (SEQ ID NO:29) and
TCCACGACATACTCAGCAC (SEQ ID NO:30). To assure the amplicon
specificity of each primer set, the PCR products were subjected to
a melting curve analysis and subsequent agarose gel
electrophoresis. The PCR reaction was performed in triplicates
using the SYBR.RTM. Green Master Mix in a total volume of 50 .mu.l.
The reaction mixture was incubated at 95.degree. C. for 10 minutes
followed by a cycling profile of 45 cycles consisting of
denaturation at 95.degree. C. for 9 seconds, annealing at
57.degree. C. for 9 seconds, and extension at 72.degree. C. for 30
seconds. The efficiency for amplification of the target gene (VEGF)
and the internal control gene (GAPDH) was examined using serial
dilutions of cDNA with gene-specific primers. The mean difference
between threshold cycle number values (.DELTA.C.sub.T) was
calculated for each cDNA dilution. The VEGF gene expression level
in each sample was calculated following normalization to the GAPDH
gene level and expressed as relative units.
Tumor cDNA Microarray Analysis
[0125] The relative mRNA abundance in the snap-frozen tumor
xenograft samples was assessed by oligonucleotide-based microarray
analysis using an Affymetrix GeneChip.RTM.Human Genome U133 set.
This GeneChip.RTM. consists of two array units of over one million
unique oligonucleotide features covering over 39,000 transcript
variants that represent 33,000 of the best characterized human
genes. Additional information regarding these chips is available
on-line at HYPERLINK
"http://www.affymetrix.com/products/arrays/specifc/hgen133.affx."
Biotinylated cRNA probe preparation, processing, hybridization and
normalization were performed as described in the Affymetrix
GeneChip.RTM. Expression Analysis Manual. Florescence images were
captured using a gene array scanner (Affymetrix) and expression
analysis was performed using GeneSpring v5.1 software. The
wild-type TFPI-2 transfected (WT) tumor ratio of medians was
normalized with that obtained from mock-transfected (MT) tumors.
The spots that exhibited a 2-fold or greater difference in
expression levels were used to generate the gene clusters.
Results
Characterization of Stably-Transfected HT-1080 Cells
[0126] HT-1080 cells were stably transfected with the eukaryotic
expression vector pcDNA3 alone (MT-1080), or containing cDNA
constructs for either wild-type TFPI-2 (WT-1080) or R24Q TFPI-2
(QT-1080). TFPI-2-expressing stably transfected tumor cells were
cloned by limiting dilution resulting in several cell lines
secreting different levels of TFPI-2 that ranged from 10-55
ng/ml/day/10.sup.6 cells determined by ELISA and consisted of three
differential glycosylated forms of TFPI-2 (Mr 32 kDa, 29 kDa, and
26 kDa), similar to that observed for human endothelial and smooth
muscle cells (Iino et al., Arter. Thromb. Vasc. Biol. 1998;
18:40-46; Herman et al., J. Clin. Invest. 2001; 107:1117-1126; Rao
et al., Arch. Biochem. Biophys. 1995; 104: 311-314; Rao et al., J.
Invest. Dermatol. 1995; 104:379-383). The TFPI-2-secreting HT-1080
cell lines selected for these studies secreted .about.55
ng/ml/day/10.sup.6 cells, but this number most likely
underestimates the amount of TFPI-2 secreted by these cells into
their ECM in-vivo. In this regard, our preliminary findings
indicated that the stably-transfected HT-1080 cells, similar to
endothelial cells and smooth muscle cells (Iino et al., Arter.
Thromb. Vasc. Biol. 1998; 18:40-46; Herman et al., J. Clin. Invest.
2001; 107:1117-1126), secrete 4-6 fold higher levels of TFPI-2 into
their ECM in cultures in comparison to their luminal secretion.
[0127] Initial in-vitro studies revealed that the TFPI-2-expressing
HT-1080 cells in continuous culture for six weeks secreted a
relatively constant amount of TFPI-2 while under G-418 selection
(FIG. 9). In the absence of G-418, these same cells continued to
secrete TFPI-2, but the level declined by about 25% over six weeks
of continuous culturing (FIG. 9). Despite the slow and progressive
loss of the expression vector in the absence of G-418, i.e., under
conditions that would partially mimic the in-vivo growth of this
cell line, the TFPI-2 expression level was still about 80% over a
five-week period. Accordingly, this period was selected as the time
frame to evaluate the effect of TFPI-2 secretion on the in-vivo
growth and metastasis of this tumor cell in SCID mice.
[0128] We next evaluated whether the growth rate of
TFPI-2-expressing HT-1080 cells in culture were similar to the
mock-transfected HT-1080 cells (MT-1080) over a 6-week period as
described elsewhere. Although a slight decline in proliferation
rate was noted over time, the proliferative rates of all
transfected HT-1080 cells were essentially equivalent, suggesting
that TFPI-2 secretion by these cells had no influence on their
growth rate in-vitro (FIG. 10).
[0129] In separate experiments, transfected HT-1080 cells cultured
in the absence of G-418 also exhibited growth rates virtually
identical to transfected cells grown in the presence of G-418,
providing evidence that G418 was also not affecting the
proliferative rate of these cells. Moreover, transfection of these
cells had no effect on their proliferative rates, as transfected
tumor cells, cultured in the absence of G418, grew at a rate
indistinguishable from the parental HT-1080 cell line.
Growth of Transfected HT-1080 Tumors in Athymic Mice
[0130] Athymic male Balb/c mice, grouped randomly, were inoculated
subcutaneously with 5.times.10.sup.6 cells transfected HT-1080
cells. SQ tumor growth of MT-1080 cells was linear with time and
achieved an average volume of 837.+-.104 mm.sup.3 five weeks
post-inoculation (Table 2). SQ tumor growth of WT-1080 cells was
also linear, but in sharp contrast to MT-1080 SQ tumors, these
tumors were, on an average, 28-60% smaller than the MT-1080 tumors
at comparable times post-inoculation (Table 2). QT-1080 SQ tumors
exhibited essentially the same tumor growth rate as the MT-1080
tumors (Table 2), suggesting that secretion of wild-type TFPI-2 by
WT-1080 cells was associated with reduced tumor size.
TABLE-US-00002 TABLE 2 Effect of TFPI-2 Expression on the Growth of
HT-1080 Tumors Tumor Volume (mm.sup.3).sup..sctn. Tumor Type Week 1
Week 2 Week 3 Week 4 Week5 MT-1080 24.1 .+-. 4.7 165.9 .+-. 17.5
336.3 .+-. 38.2 570 .+-. 59.1 837 .+-. 103.8 WT-1080 5.5 .+-. 0.8
66.9 .+-. 14.4 161.0 .+-. 30.6 327 .+-. 57.2 462 .+-. 70.5 QT-1080
20.5 .+-. 4.0 155.6 .+-. 18.9 302.4 .+-. 36.2 515 .+-. 57.4 731
.+-. 78.1 .sup..sctn.Values are expressed as the Mean .+-. SEM.
Differences between all mean values at a given time point were
tested pairwise by one way analysis of variance (ANOVA) and
statistical significance was accepted at P .ltoreq. 0.05.
[0131] Mice were sacrificed five weeks post-inoculation. At
sacrifice, the average weight of the resected MT-1080 and QT-1080
tumors was 2.65.+-.0.56 g, whereas the average weight of the
resected WT-1080 tumors was 1.47.+-.0.34 g. Metastasis of MT-1080,
WT-1080 and QT-1080 tumor cells in the SCID mice from the primary
tumor location was confined exclusively to the lungs. Of the twelve
SCID mice inoculated with MT-1080 cells, nine mice (75%) developed
metastatic lesions/nodules in the lungs, as compared to a
metastatic incidence of 42% (5/12) in mice inoculated with WT-1080
cells (P<0.001). The metastatic incidence of SCID mice
inoculated with QT-1080 cells was identical to that observed for
mice inoculated with MT-1080 cells. In order to assess the degree
of metastasis in each experimental group, four randomly selected
paraffin-embedded lungs from each group were sectioned in their
entirety, and all sections (except every fourth section) were
H&E stained. Examination of these sections revealed as many as
5-8 metastatic sites per tumor-positive lung in mice injected with
MT-1080 cells, while only 1-2 metastatic sites were observed in
tumor-positive lungs of mice inoculated with WT-1080 or QT-1080.
The metastatic tumor size, evaluated from the number of sections
they spanned, varied from 30-300.mu.. As with the growth of SQ
tumors in athymic mice, these findings provide evidence that
metastasis of HT-1080 tumors was markedly inhibited through their
ability to secrete inhibitory TFPI-2.
Histological and Immunohistochemical Analyses of Primary and
Metastatic Tumors
[0132] The histology of all primary SQ tumors, shown in FIG. 11
(Panel A), exhibited a peculiar morphology with loosely distributed
cells in a core region (referred to as core cells, or CC)
encompassed by rather tightly packed peripheral cells (PC). Initial
immunohistochemical analyses of MT-1080, WT-1080 and QT-1080 cell
cytospins revealed that MT-1080 cells were negative for TFPI-2
antigen, consistent with the absence of detectable TFPI-2 in
parental HT-1080 cell conditioned media by ELISA. On the other
hand, WT-1080 and QT-1080 cells, stained strongly positive for
TFPI-2 antigen in cell cytospins. In agreement with the cell
cytospin analyses, primary MT-1080 tumors exhibited negative
immunoreactivity for TFPI-2 antigen both in the PC and CC regions.
In contrast, WT-1080 and QT-1080 primary tumors stained positive
for TFPI-2 antigen in the PC region (FIG. 11, Panel D), but failed
to stain in the CC region (FIG. 11, Panel C). Interestingly,
metastatic tumors from all groups of mice, when subjected to
immunohistochemical analyses, failed to show any detectable TFPI-2
antigen (FIG. 11, Panels I & J).
Differential Cellular Proliferation and Apoptosis
[0133] The relative distribution of proliferating (BrdU positive)
cells was also assessed in sections of primary tumors from each
experimental group. More than 90% of the PC in all three
tumor-types was proliferating (FIG. 11, Panel F), whereas only
8-10% of CC were proliferating in MT-1080 or QT-1080 primary
tumors. By comparison, more than 20% of CC region cells in WT-1080
tumors were positive for proliferation (FIG. 11, Panel E). When
examined for apoptosis by TUNEL assay, very few cells in the PC or
CC regions in MT-1080 and QT-1080 primary tumors stained positive.
In the case of the WT-1080 primary tumors, negligible numbers of
cells were undergoing apoptosis in the PC region, whereas >40%
of cells in the CC region stained positive (FIG. 11, Panel G &
H).
Tumor Cell DNA Analyses
[0134] To address the possibility that the core cells were of
murine origin recruited into the growing tumor mass, a PCR-based
qualitative analysis was performed on each cell type (PC and CC)
found in the three primary tumors, as well as cells of metastatic
tumors. Cellular DNA was prepared from microdissected cells as
described earlier. By qualitative PCR amplification using human
mitochondrial (mtDNA)-specific primers, both PC and CC cell types
were positive for human mitochondrial DNA (FIG. 12, top panel),
providing evidence that these regions contain human cells. PCR
amplification of the recombinant vector/construct (rvcDNA)-specific
region revealed that only cellular DNA from the PC regions of
WT-1080 and QT-1080 tumors was positive (FIG. 12, bottom panel). No
rvcDNA amplification was observed in MT-1080 tumor cells (FIG. 12,
bottom panel). The metastatic lung tumors also demonstrated the
presence of human mitochondrial DNA attesting to their human origin
(FIG. 12, top panel). Somewhat surprisingly, cellular DNA derived
from WT-1080 and QT-1080 lung tumors tested positive for the intact
rvcDNA region following PCR amplification (FIG. 12, bottom panel),
in spite of undetectable TFPI-2 antigen in these cells. The reason
for this discrepancy is not known, but most probably relates to the
relative sensitivities between immunohistochemistry and PCR
amplification techniques. Alternatively, TFPI-2 synthesis and
expression may be down-regulated by lung-specific signaling
molecules from the metastatic tumor microenvironment.
[0135] VEGF Expression in Tumors
[0136] As VEGF expression is critical for tumor microvasculature
formation (Shih et al., Am. J. Pathol. 2002; 161:35-41), we
performed a real time quantitative RT-PCR analysis to assess murine
VEGF gene expression levels in three tumor samples randomly
selected from each tumor group. Melting curve analyses of the
amplified PCR products revealed predominately a single product with
distinct T.sub.m values (T.sub.m=82.6.degree. C. for GAPDH and
T.sub.m=84.4.degree. C. for VEGF; FIG. 13A). The efficiencies for
the VEGF and GAPDH amplification were similar as the slope obtained
from a plot of log cDNA dilution versus .DELTA.C.sub.T was <0.1
(FIG. 13B), thus validating the primer sets. The relative VEGF
levels (mean.+-.SEM) for mouse liver and three representative
samples of each tumor type were then plotted as shown in FIG. 13C.
Tumors arising from MT-1080 cells showed a 3-6-fold higher
expression of VEGF mRNA than tumors derived from WT-1080 cells,
whereas VEGF mRNA expression in QT-1080 cells was essentially
identical to VEGF mRNA levels found in MT-1080 cells. The final PCR
reaction products revealed amplification of a single, specific band
for VEGF (FIG. 13D, upper panel) and GAPDH (FIG. 13D, lower panel)
on agarose gel electrophoresis.
Genes Regulated by TFPI-2 Expression
[0137] Using four-independent tumor samples in the Affymetrix
GeneChip.RTM. microarray system, a relative gene expression profile
was obtained. Comparative differential gene-expression analysis
revealed that 80 genes had significantly altered levels of
expression, directly or indirectly regulated by TFPI-2 expression
in these tumors. Among these, 43 genes were upregulated and 37
genes were downregulated. Further analysis revealed that 15 mRNA
species were induced by more than 4-fold and 10 mRNA species were
repressed by 4-fold or more. In Table 3, the proteins encoded by
these genes are grouped according to their functions. The analysis
of the genes according to a gene ontology system showed that TFPI-2
expression regulated genes in almost every category including those
implicated in transcription, signal transduction, cell growth and
proliferation, extracellular matrix, oncogenesis, invasion and
metastasis, apoptosis and angiogenesis.
TABLE-US-00003 TABLE 3 Genes regulated by TFPI-2 expression in
fibrosarcoma xenografts obtained from SCID mice. GeneBank Fold
Accession no. Change* Description Transcription factors NM_001186
-2.11 Helicase, Basic leucine zipper transcription factor-1
NM_006963, +29.27 Zinc finger protein 22 (KOX 15) AA744771
NM_006291 +5.05 Zinc finger protein 185 (LIM domain) NM_014368
+2.91 LIM homeobox protein 6 NM_001290 -5.20 LIM domain binding 2
NM_002586 -2.75 PBX-2, Pre-B cell leukemia transcription factor-2
X16155 -2.79 COUP-transcription factor Signal transduction
NM_004445 -2.38 Erythropoietin-producing hepatocyte kinase, EphB6
NM_002547 +2.95 Oligophrenin 1 NM_002821 +2.33 protein tyrosine
kinase 7 U71075 -2.48 Protein tyrosine phosphatase, receptor type,
U D30751 +2.79 Bone morphogenetic protein 4 NM_022159 -2.92
EGF-TM7-latrophilin-related protein Cell growth, proliferation and
maintenance NM_013975 +2.04 Ligase III, DNA NM_006567 +2.11
Phenylalanine-tRNA synthetase AU118882, -2.90 Endothelin receptor
type A NM_001957 NM_002349 +14.32 Lymphocyte antigen 75, gp200-MR6
NM_005330 -7.63 Hemoglobin, epsilon 1, oxygen transport NM_000385
+2.30 Aquaporin 1 AF052169 +2.48 voltage-gated potassium channel
activity BE742268 -4.21 sortilin 1 (SORT1) AW206786 -2.32 enigma
(LIM domain protein) Invasion and Metastasis M34064 -2.13
N-Cadherin NM_014751 +2.06 Metastasis suppressor gene NM_002961
+2.79 S100 calcium-binding protein A4 NM_021111 +2.64
Reversion-inducing-cysteine-rich protein with kazal motif (RECK)
AF348491, -4.21, Chemokine (C-X-C motif), receptor AJ224869 -27.40
4 (fusin) NM_022842 -18.70 CUB domain-containing protein 1 (CDCP1)
Oncogenes/Tumor suppressor genes NM_021991 -2.21 Junction
plakoglobin NM_003287 +2.10 Tumor protein D52-like 1 NM_001958
+6.85 EEF1A2, Eukaryotic translation elongation factor 1 alpha 2
Apoptosis NM_005892 -2.14 Formin like (FRL) NM_020371 -2.11 Cell
death regulator Aven Angiogenesis NM_002019 -2.24 FLT, VEGFR1,
Fms-related tyrosine kinase receptor NM_000584 -6.99 Interleukin-8
(IL-8, C-X-CL8) AI812030 -3.39 thrombospondin 1 precursor L01639
-8.03 Neuropeptide Y receptor U58111 -2.41 Vascular endothelial
growth factor C NM_006291 +2.98 Tumor necrosis factor,
alpha-induced protein 2 Extracellular matrix NM_002607 +2.53
platelet derived growth factor alpha polypeptide NM_021599 -4.62
ADAM-TS2 BC002416 -2.29 Biglycan NM_000088 +3.51 Collagen, type I,
alpha 1 AI264196 -2.48 fibrillin 1 precursor D32039 -2.13
Chondroitin sulfate proteoglycan 2 (versican) AI146848 +2.87
dermatopontin precursor AJ276395 -3.80 Fibronectin 1 AA669336 +7.26
Alpha 1 chain of Type XII Collagen Others NM_002759 +2.51 EIF2Ak1,
protein kinase, PKR NM_004988 -2.95 MAGE-A1, Melanoma antigen
family A1 NM_016931 -2.46 Nox 4, NADPH oxidase 4 NM_021822 +2.80
Phorbolin-like protein MDS019 NM_001785 +35.30 Cytidine deaminase
*The number indicates the -fold change in mRNA abundance in TFPI-2
expressing tumors over mock-transfected tumors determined by
microarray data analysis. + and - indicate increased and decreased
mRNA levels.
Discussion
[0138] In the present study, we have prepared stably-transfected
human HT-1080 fibrosarcoma cell lines expressing either wild-type
human TFPI-2 or an inactive mutant TFPI-2 (R24Q TFPI-2), and
assessed their ability to grow and metastasize in athymic Balb/c
mice in relation to a mock-transfected HT-1080 cell line. We
observed that stably-transfected WT-1080 cell tumor grew at a
substantially lower (about 28-60%) rate than MT-1080 solid tumors.
QT-1080 produced subcutaneous tumor masses essentially identical in
volume to that observed for the MT-1080, providing suggestive
evidence that the expression of inhibitory TFPI-2 was associated
with restricted tumor growth. In addition to the substantially
decreased growth rate of WT-1080 tumors, the metastatic rate of
WT-1080 cells (42%) was also markedly lower than that observed for
QT-1080 or MT-1080 cells (75%). The decreased metastatic rate of
WT-1080 cells in all likelihood relates to a smaller primary tumor
mass burden rather than TFPI-2 expression, as immunohistochemical
analyses revealed that the WT-1080 metastatic tumors paradoxically
failed to stain for immunoreactive TFPI-2 but retained the
vector/construct as shown by PCR. The reason(s) for this
discrepancy is not known but may be related to different
sensitivities between these two techniques and/or downregulation of
TFPI-2 expression in the metastatic tumor microenvironment.
[0139] Our in vivo findings are clearly consistent with and extend
previous in-vitro results demonstrating a dose-dependent inhibition
of HT-1080 invasiveness in Matrigel and ECM degradation by
exogenous TFPI-2 (Rao et al., Int. J. Cancer 1998; 75:749-756). Our
results are also consistent with a recent report by Konduri and
colleagues (Konduri et al., Oncogene 2001; 20:6938-6945)
demonstrating that high-grade SNB19 glioma cells stably-transfected
with the human TFPI-2 expression vector fowled smaller
intracerebral tumors in contrast to its mock-transfected
counterpart. Finally, our data agree, in part, with that very
recently published by Jin and coworkers (Jin et al., Gync. Oncol.
2001; 83:325-333) who demonstrated that TFPI-2-expressing human
choriocarcinoma cells (JAR) exhibited decreased invasive properties
in Matrigel relative to mock-transfected JAR tumor cells, as well
as decreased invasiveness in-vivo in nude mice following SQ
transplantation. However, in contrast to our findings using HT-1080
fibrosarcoma cells, mock-transfected and TFPI-2-expressing human
choriocarcinoma tumors were essentially identical in mass and
failed to metastasize (Jin et al., Gync. Oncol. 2001;
83:325-333).
[0140] Histological analyses on primary and metastatic tumors were
performed to evaluate the effects of TFPI-2 on tumor growth and
metastasis. HT-1080 tumors consisted of two distinct regions; a
homogeneous core of cells with condensed nuclei, and peripheral
cells that appeared morphologically similar to cultured HT-1080
cells. Although both regions demonstrated the presence of human
mtDNA, only cells occupying the peripheral regions were positive
for TFPI-2 antigen and demonstrated presence of the vector
construct. BrdU and TUNEL staining confirmed that cells present in
the peripheral region were still proliferating, while most of the
cells occupying the core region were undergoing apoptosis. Since
tumor volumes were significantly smaller in WT-1080-treated mice,
TFPI-2 most likely affects those processes involved in tumor mass
formation in-vivo, such as neovascularization, rather than
inhibiting the proliferative rate of individual tumor cells.
[0141] The precise mechanism(s) whereby genetically engineered
expression of functional TFPI-2 by a TFPI-2 null cell reduces tumor
size and its aggressive phenotype in-vivo is unclear. During tumor
growth, malignant cells invade normal adjacent tissues, and
regulation of plasmin activity on the surface of tumor cells has
been shown to influence the invasive and metastatic behavior of
tumor cells (Crowley et al., Proc. Natl. Acad. Sci. USA 1993;
90:5021-5025; Stahl et al., Cancer Res. 1994; 54:3066-3071; Min et
al., Cancer Res. 1996; 56:2428-2433). However, plasmin associated
with the ECM or the membranes of cultured cells is resistant to
inhibition by known physiologically-relevant proteinase inhibitors
(Bizik et al., Cell Regul. 1990; 1:895-905; Quax et al., J. Cell
Biol. 1991; 115:191-199; Reinartz et al., Exp. Cell Res. 1993;
208:197-208), and it has been suggested that metastatic tumor cells
generate "unregulated" plasmin activity which potentiates
metastatic behavior (Kwaan et al., Cancer Metastasis Rev. 1992;
11:291-311; Kramer et al., Invasion Metastasis, 1994; 14:210-222).
Many tumor cells, including the HT-1080 fibrosarcoma cell line
utilized in this study, employ the uPA-uPAR system to activate
plasminogen, resulting in plasmin-mediated ECM degradation and
invasion, as well as proMMP-1 and proMMP-3 activation that further
enhances tumor invasion and metastasis (Rao et al., Biochem.
Biophys. Res. Commun. 1999; 255:94-99). In addition, tumor growth
is highly dependent on an adequate blood supply, and plasmin
presumably plays an important role in tumor angiogenesis (Tarui et
al., J. Biol. Chem., 2002, 277:33564-33570). In this regard, Soff
and coworkers (Soff et al., J. Clin. Invest. 1995; 96:2593-2600)
have reported that expression of PAI-1 by a stably-transfected
human prostate carcinoma cell line (PC-3) markedly reduced the
growth rate of these primary tumors in an athymic mouse model in
relation to the parental PC-3 cell line, providing clear evidence
that regulation of plasmin formation reduced the aggressive
phenotype of these cells. In view of its ability to strongly
inhibit plasmin in vitro, it is not unreasonable to speculate that
ECM-associated TFPI-2 generated by WT-1080 tumors inhibits ECM
turnover mediated by plasmin and plasmin-activated matrix
metalloproteinases, thereby inhibiting tumor invasiveness and
metastases in-vivo. In this connection, preliminary studies have
shown that wild-type human TFPI-2 exhibited a potent and
dose-dependent anti-angiogenic effect in both the VEGF-induced
chorioallantoic membrane assay and the FGF-2-induced cornea pocket
assay. Accordingly, the ability of secreted TFPI-2 to reduce tumor
size may be dependent, in part, on its anti-angiogenic
properties.
[0142] To establish the role of TFPI-2, if any, in
neovascularization essential for tumor growth and metastasis, host
VEGF gene expression was quantitated in these tumors by real time
quantitative RT-PCR. MT- and QT-1080 tumors expressed essentially
the same levels of VEGF mRNA, whereas WT-1080 tumor VEGF mRNA
levels were reduced 3-6-fold in relation to MT- and QT-1080 tumors.
Accordingly, a clear quantitative correlation was observed between
murine VEGF expression levels and tumor size, suggesting that
active TFPI-2 plays a suppressive role on host-derived VEGF gene
expression and, by extension, on VEGF-mediated angiogenesis. The
cellular origin of murine VEGF mRNA isolated from these tumors is
not known, although host stromal cells may be one cell responsible
for VEGF synthesis. Clearly, the higher apoptotic rate of WT-1080
tumor core cells strongly suggests decreased tumor angiogenesis in
this portion of the tumor architecture that may be related to
either lower host VEGF mRNA expression in these tumors, or elevated
levels of angiostatin, or both. Although wild-type HT-1080 cells
constitutively secrete human VEGF (Sawaji et al., Br. J. Cancer
2002; 86:1597-1603) that presumably contributes greatly to
neovascularization in these tumors, recent studies have shown that
complete inhibition of rhabdomyosarcoma xenograft growth and
neovascularization in nude mice required inhibition of both tumor
and host-derived VEGF (Gerber et al., Cancer Res. 2000;
60:6253-6258).
[0143] The relative assessment of genes in the snap-frozen tumor
xenograft by oligonucleotide-based microarray analysis revealed no
significant change in the human (tumor) VEGF gene levels, although
a 2-fold or greater decrease in FLT-1 (VEGFR1) and VEGF-C mRNA
levels was observed. VEGF-C and VEGFR1, a VEGF receptor, have been
implicated in tumor-related angiogenesis (Andre et al., Int. J.
Cancer 2000; 86:174-181; Olofsson et al., Proc. Natl. Acad. Sci.
USA 1998; 95:11709-11714; Mandriota et al., EMBO J. 2001;
20:672-682). Thus, induced TFPI-2 expression does not regulate
tumor VEGF mRNA levels but rather appears to suppress its
angiogenic effect by downregulating receptor (VEGFR1) levels. Among
other angiogenic regulators, IL-8, THBS-1 and neuropeptide-Y
receptor gene levels were also down-regulated, whereas the tumor
necrosis factor alpha-induced protein 2 (TNF-AIP2) levels were
upregulated. Interleukin-8 is not expressed constitutively, but on
TNF-.alpha. induction inhibits apoptosis via NF-kappaB and Akt
signaling pathways (Osawa et al., Infect. Immun. 2002;
70:6294-6301). IL-8 also exhibits potent angiogenic activity and
thus may play a role in tumor progression. Thrombospondin (THBS-1)
suppresses tumor growth, inhibits activation of MMP-9 and inhibits
VEGF binding to receptor suppressing capillary morphogenesis
(Rodriquez-Mazaneque et al., Proc. Natl. Acad. Sci. USA 2001;
98:12485-12490). Surprisingly, its expression is downregulated by
TFPI-2, partially reducing its anti-tumor growth function. However,
another anti-angiogenic gene, neuropeptide Y receptor-2 regulates
angiogenesis-dependent tumor repair (Ekstrand et al., Proc. Natl.
Acad. Sci. USA 2003; 100:6033-6038), and is down-regulated. Thus,
at the transcriptional level, TFPI-2 expression regulates both pro-
and anti-angiogenic regulators, which, in concert, could affect
tumor angiogenesis.
[0144] The pro-invasive and pro-metastatic genes such as
N-cadherin, CDCP1 and chemokine receptor 4 are suppressed by TFPI-2
induction in these tumor cells. N-cadherin, a cell adhesion
molecule, makes heterotypic contacts with catenin (.alpha., .beta.,
.gamma.)-p120.sup.ctn promoting matrix invasion and
transendothelial migration by convergence of TGF-13 signaling
(Mareel et al., Physiol. Rev. 2003; 83:337-76). The junction
plakoglobin (.gamma.-catenin) (Winn et al., Oncogene 2002;
21:7497-7506) is also suppressed by TFPI-2. Protein tyrosine
phosphatase receptor .mu. (PTPRmu) (Zondag et al., J. Biol. Chem.
2000; 275:11264-11269), another component of this cadherin-catenin
complex that dephosphorylates p120.sup.ctn, is also downregulated.
Thus, most of the components of the cadherin-catenin complex are
suppressed, possibly leading to an imbalance between levels of
activated N-cadherin and E-cadherin necessary for cell motility and
tumor invasion (Mareel et al., Physiol. Rev. 2003; 83:337-76).
Furthermore, the ectodomain of E-cadherin (sE-CAD) is shed by
plasmin, stromelysin-1 and matrilysin (MMP7) cleavage thereby
stimulating tumor invasion, in part, by upregulation of MMP-2,
MMP-9 and MT1-MMP (Mareel et al., Physiol. Rev. 2003; 83:337-76;
Ryniers et al., Biol. Chem. 2002; 383:159-165; Nawrocki-Raby et
al., Int. J. Cancer 2003; 105:790-795). Since it is thought that
metastatic tumor cells generate "unregulated" plasmin activity
(Kwaan et al., Cancer Metastasis Rev. 1992; 11:291-311; Kramer et
al., Cancer Metastasis Rev. 1994; 14:210-222), the tumor growth
suppression could also be affected by the plasmin-inhibitory
activity of TFPI-2 suppressing sE-CAD production.
[0145] Tumor invasion metastasis suppressor genes, MIM (Lee et al.,
Neoplasia 2002; 4:291-294) and RECK are induced more than 2-fold in
TFPI-2 over-expressing tumors. Overexpression of RECK has been
shown to faun HT-1080 tumors defective in vasculature due to
inhibition of angiogenic sprouting through excessive degradation of
the ECM (Oh et al., Cell 2001; 107:789-800). Moreover, RECK
negatively regulates matrix-metalloproteinases MMP-2, MMP-9 and
MT1-MMP, thereby inhibiting tumor invasion, metastasis and
angiogenesis (Voda et al., Cancer Metastasis Rev. 2003; 22:167-175;
Takahashi et al., Proc. Natl. Acad. Sci. USA 1998; 95:13221-13226).
However, the prometastatic gene, S100A4/MTS1/metastasin,
upregulated in medulloblastoma, brain cancer cells, and murine
melanoma (Mazzucchelli, Am. J. Pathol. 2002; 1601:7-13), was also
upregulated in these tumors.
[0146] Two of the pro-apoptotic genes, FRL (Yayoshi-Yamamoto et
al., Mol. Cell. Biol. 2000; 20:6872-6881), and chemokine receptor 4
(CXC-R4) (Bodner et al., J. Neuroimmunol. 2003; 140:1-12) are
downregulated, suggesting the induction of genes that support tumor
cell growth and survival. In contrast, the anti-apoptotic gene,
Aven (Chau et al., Mol. Cell. 2000; 6:31-40), is downregulated.
Genes encoding for extracellular matrix constituents like ADAM-TS2,
biglycan, fibronectin 1, versican, and fibrillin 1 precursors are
suppressed, whereas dermatopontin and collagen 1 alpha 1 genes are
upregulated, suggesting regulation of ECM remodeling at the
transcriptional level. In addition, a large number of genes found
to be regulated by TFPI-2 in this model are implicated in general
cellular functions including signal transduction, cell growth and
proliferation and the synthesis of some transcription factors,
which in turn regulate other genes that affect other cellular
processes.
[0147] While the genomic response to TFPI-2 overexpression appears
complex, most of the genes regulated by TFPI-2 would result in an
overall decrease in tumor growth and metastatic potential. The
molecular mechanism whereby TFPI-2 expression and function affects
tumor cell gene expression is not known, but presumably involves
its ability to regulate proteinases such as trypsin, plasmin or the
factor VIIa-tissue factor complex either on the tumor cell or in
the tumor microenvironment that, in turn, affect a variety of tumor
cell signaling processes involved in growth and angiogenesis.
Future studies focused on the regulation and functional
significance of the target genes reported here are likely to
increase our understanding of the role of TFPI-2 in the regulation
of pericellular ECM remodeling in normal and tumor cells.
Example IV
Plasmin Inhibitor TFPI-2/KD1 Blocks Mononuclear Cell Migration into
Airways in a Murine Model of Allergic Asthma
[0148] Recent published work, using plasminogen knockout mice, has
demonstrated that plasminogen and its activated form, the serine
proteinase plasmin, regulate cellular recruitment and pathogenesis
in a murine model of asthma. In addition to playing a major role in
fibrinolysis and matrix metalloproteinase activation, plasmin
cleaves cell surface G-coupled proteins (protease activated
receptors) leading to signal transduction events, increased mRNA
expression and increased cellular migration.
[0149] We have recently demonstrated that constitutive expression
of tissue factor pathway inhibitor-2 (TFPI-2), a Kunitz-type
plasmin inhibitor, by a fibrosarcoma tumor cell markedly decreased
its subcutaneous growth and metastasis in athymic mice in a process
that partly involves decreased tumor angiogenesis (Example III). We
were interested in testing whether a recombinant preparation of the
first Kunitz-type domain of TFPI-2 (KD1) that inhibits plasmin
activity in vitro (Ki=3 nM) affects the putative plasmin-mediated
development of allergic lung inflammation and the recruitment of
leukocytes to the airways.
[0150] B.sub.6D.sub.2F1 mice were immunized with ovalbumin (OVA)
adsorbed to alum (days 0 and 5) and received two OVA aerosols on
day 12. A subgroup of mice were treated with hexahistidine-tagged
KD1, delivered via the lateral tail vein, on days 11-14. Mice were
sacrificed on day 15 for the enumeration and differentiation of
cells in the airway and lung tissue compartments.
[0151] Treatment with hexahistidine-tagged KD1 resulted in a
statistically significant decrease in total numbers of cells,
macrophages and lymphocytes recoverable from the airways after OVA
aerosol in comparison to vehicle treated mice. Total numbers of
cells recovered by collagenase digestion of lung tissue was
equivalent in mice treated with hexahistidine-tagged KD1 as
compared to vehicle. These data suggest that plasmin mediates
transepithelial, but not transendothelial, migration of mononuclear
cells in a murine model of asthma. See Wilder et al., Am. J. Resp.
Crit. Care Med. 2004; 169(7):A803.
Example V
Crystal Structure of Kunitz Domain 1 (KD1) of Tissue Factor Pathway
Inhibitor-2 with Trypsin and Molecular Model of KD1 with Plasmin
and Factor VIIa/Tissue Factor: Implications for KD1 Specificity of
Inhibition
[0152] Tissue factor pathway inhibtor-2 (TFPI-2), also known as
matrix serine protease inhibitor or placental protein 5, contains
three Kunitz-type inhibitory domains in tandem. A variety of cells
including keratinocytes, dermal fibroblasts, smooth muscle cells,
syncytiotrophoblasts, synoviocytes, and endothelial cells
synthesize and secrete TFPI-2 into the extracellular matrix (ECM).
Kunitz domain 1 (KD1) of TFPI-2 inhibits plasmin (Ki=3 nM), trypsin
(Ki=13 nM), and FVIIa/TF (Ki=1640 nM).
[0153] We employed crystallography and molecular modeling
approaches to elucidate the basis of the specificity of KD1 for
plasmin versus trypsin or FVIIa/TF. Crystals of the complex of KD1
with bovine trypsin were obtained that diffracted to 1.8 .ANG. and
belonged to the space group P2.sub.12.sub.12.sub.1 with unit cell
parameters, a=74.11, b=77.01, and c=125.42. Each asymmetric unit
contained two KD1-trypsin complexes. The structure of KD1 thus
obtained was then used in conjunction with the known structures of
plasmin and FVIIa/TF to model the KD1-plasmin and KD1-FVIIa
complexes. KD1 contained a hydrophobic core consisting of residues
Leu-9 (BPTI numbering), Tyr-11, Tyr-22, and Phe-33.
[0154] In all structures, Arg-15 (P1 residue) of KD1 interacted
with Asp-189 (chymotrypsin numbering) at the bottom of the
specificity pocket. A hydrophobic patch involving residues Leu-17,
Leu-18, Leu-19, and Leu-34 of KD1 was identified to interact with a
hydrophobic patch in plasmin and trypsin but not in FVIIa/TF. This
complementary hydrophobic patch in plasmin consists of Phe-37,
Met-39, Phe-41, and the carbon side chains of Gln-192 and Glu-141.
In trypsin, it consists of Tyr-39, Phe-41, Tyr-151 and the carbon
side chain of Gln-192. Furthermore, a basic patch involving Arg-98,
Arg-173 and Arg-221 in plasmin was identified to interact with an
acidic patch in KD1 consisting of residues Asp-10 and Glu-39. This
electrostatic interaction is absent in trypsin and in FVIIa/TF.
Moreover, Tyr-46 in KD1 can make H-bonds with Lys-61 and Arg-64 in
plasmin as well as with Lys-60A in FVIIa/TF; however, these
interactions are absent in trypsin. Further, Arg-20 of KD1 is
important for making a H-bond with Glu-60 in plasmin, with Lys-60
through a water molecule in trypsin and with Asp-60 in
FVIIa/TF.
[0155] Cumulatively, the crystal structure and refined modeling
data confirm our previous predictions and illustrate the molecular
basis for preference of KD1 to inhibit plasmin versus trypsin or
FVIIa/TF. KD1 interacts with plasmin through hydrophobic and
electrostatic interactions whereas the electrostatic contacts are
limited in trypsin. Notably, both the electrostatic and hydrophobic
interactions are sparse in FVIIa/TF. Thus, both the crystal and
modeled structures validate the differential effects of mutations
in KD1 involving residues surrounding the P1 site, including D10A,
L17Q, R20D, and F33A, reported earlier (Chand et al., J. Biol.
Chem. 279, 17500-17507, 2004). Knowledge gained from such studies
may help in the development of a potent and specific TFPI-2 KD1
molecule that specifically inhibits plasmin without targeting other
proteases. Such a molecule could have a large pharmacologic impact
specifically in preventing tumor metastasis, retinal degeneration,
and degradation of collagen in the ECM.
Example VI
Inhibition of Angiogenesis by TFPI-2
Materials and Methods
[0156] A semi-quantitative assay for in vitro angiogenesis was
utilized. Human umbilical vein endothelial cells (HUVEC, Clonetics)
were maintained in 25 cm.sup.2 flasks in EGM-2 media (Clonetics)
supplemented with 2% fetal bovine serum, gentamicin,
amphotericin-B, hEGF, hydrocortisone, VEGF, hFGF-B, R3-IGF-1,
ascorbic acid and heparin. For assay, a 48-well tissue culture
plate was coated with 100 .mu.l of ECMatrix.TM. (Chemicon) followed
by incubation at 37.degree. C. for 1 hour. Approximately
5.times.10.sup.4 cells were then seeded onto the surface of the
polymerized matrix. Varying concentrations of full-length human
TFPI-2, diluted in EGM-2 media and filtered, were added to the
wells and plate was placed in 37.degree. C.-humidified CO.sub.2
incubator. Each treatment was performed in duplicate wells.
Separately, VEGF was used as a positive control. The 3-dimensional
organization of cells was examined every hour under an inverted
photomicroscope. The capillary tube branch point formation was
counted in each well following 8 hours of incubation. For each
concentration, eight randomly chosen areas under 250.times.
magnified field were observed. The results are expressed as number
of branching points (mean+SEM) and the differences between each
mean value was tested by one way analysis of variance (ANOVA).
Statistically p-value<0.05 was accepted.
[0157] To examine the effect of full-length human TFPI-2 on
morphogenesis (capillary-like tube formation) of endothelial cells,
HUVECs were seeded on the matrigel and treated with full-length
human TFPI-2 (0.2 .mu.M-5 .mu.M).
Results
[0158] Capillary-like tube formation, an indication of in-vitro
angiogenesis, was well developed in control HUVECs after 6 hours
(FIG. 14A) whereas with TFPI-2 (5 .mu.M) treatment there was no
complete tube formation even after overnight incubation (FIG. 14B).
Additionally, TFPI-2 treatment significantly inhibited the
capillary-like tube formation of HUVECs in a dose-dependent manner
compared to controls (FIG. 14C). Addition of the pro-angiogenic
agent, VEGF, yielded a significant increase in number of tube
formation (FIG. 14C) with the first visible tube forming within 3
hours of incubation compared to approximately 4 hours in the
control. Further, angiogenesis-related genes are modulated by
full-length TFPI-2. As described in Example III, VEGF-C was down
regulated 2.41 fold, VEGF-R1 (FLT1) was down regulated 2.24 fold
and IL-8 another pro-angiogenic gene was down regulated 6.99 fold
in human fibrosarcomas secreting wild-type human TFPI-2.
[0159] We have shown that hexahistidine-tagged KD1 and wild-type
TFPI-2 inhibit angiogenesis. However, preliminary experiments have
indicated that wild-type KD1 does not inhibit angiogenesis. Thus,
we postulate that a positively charged amino acid sequence at
either the N-terminus or the C-terminus facilitates this
anti-angiogenic activity, perhaps by a charge-mediated targeting
mechanism.
[0160] The complete disclosure of all patents, patent applications,
and publications, and electronically available material (including,
for example, nucleotide sequence submissions in, e.g., GenBank and
RefSeq, and amino acid sequence submissions in, e.g., SwissProt,
PIR, PRF, PDB, and translations from annotated coding regions in
GenBank and RefSeq) cited herein are incorporated by reference. The
foregoing detailed description and examples have been given for
clarity of understanding only. No unnecessary limitations are to be
understood therefrom. The invention is not limited to the exact
details shown and described, for variations obvious to one skilled
in the art will be included within the invention defined by the
claims.
Sequence CWU 1
1
301213PRTHomo sapiens 1Asp Ala Ala Gln Glu Pro Thr Gly Asn Asn Ala
Glu Ile Cys Leu Leu1 5 10 15Pro Leu Asp Tyr Gly Pro Cys Arg Ala Leu
Leu Leu Arg Tyr Tyr Tyr 20 25 30Asp Arg Tyr Thr Gln Ser Cys Arg Gln
Phe Leu Tyr Gly Gly Cys Glu 35 40 45Gly Asn Ala Asn Asn Phe Tyr Thr
Trp Glu Ala Cys Asp Asp Ala Cys 50 55 60Trp Arg Ile Glu Lys Val Pro
Lys Val Cys Arg Leu Gln Val Ser Val65 70 75 80Asp Asp Gln Cys Glu
Gly Ser Thr Glu Lys Tyr Phe Phe Asn Leu Ser 85 90 95Ser Met Thr Cys
Glu Lys Phe Phe Ser Gly Gly Cys His Arg Asn Arg 100 105 110Ile Glu
Asn Arg Phe Pro Asp Glu Ala Thr Cys Met Gly Phe Cys Ala 115 120
125Pro Lys Lys Ile Pro Ser Phe Cys Tyr Ser Pro Lys Asp Glu Gly Leu
130 135 140Cys Ser Ala Asn Val Thr Arg Tyr Tyr Phe Asn Pro Arg Tyr
Arg Thr145 150 155 160Cys Asp Ala Phe Thr Tyr Thr Gly Cys Gly Gly
Asn Asp Asn Asn Phe 165 170 175Val Ser Arg Glu Asp Cys Lys Arg Ala
Cys Ala Lys Ala Leu Lys Lys 180 185 190Lys Lys Lys Met Pro Lys Leu
Arg Phe Ala Ser Arg Ile Arg Lys Ile 195 200 205Arg Lys Lys Gln Phe
210273PRTHomo sapiens 2Asp Ala Ala Gln Glu Pro Thr Gly Asn Asn Ala
Glu Ile Cys Leu Leu1 5 10 15Pro Leu Asp Tyr Gly Pro Cys Arg Ala Leu
Leu Leu Arg Tyr Tyr Tyr 20 25 30Asp Arg Tyr Thr Gln Ser Cys Arg Gln
Phe Leu Tyr Gly Gly Cys Glu 35 40 45Gly Asn Ala Asn Asn Phe Tyr Thr
Trp Glu Ala Cys Asp Asp Ala Cys 50 55 60Trp Arg Ile Glu Lys Val Pro
Lys Val65 70373PRTartificialmutated first Kunitz-type domain of
human TFP1-2 containing a R24K substitution 3Asp Ala Ala Gln Glu
Pro Thr Gly Asn Asn Ala Glu Ile Cys Leu Leu1 5 10 15Pro Leu Asp Tyr
Gly Pro Cys Lys Ala Leu Leu Leu Arg Tyr Tyr Tyr 20 25 30Asp Arg Tyr
Thr Gln Ser Cys Arg Gln Phe Leu Tyr Gly Gly Cys Glu 35 40 45Gly Asn
Ala Asn Asn Phe Tyr Thr Trp Glu Ala Cys Asp Asp Ala Cys 50 55 60Trp
Arg Ile Glu Lys Val Pro Lys Val65 70411PRTartificialReactive Site
Region 4Tyr Thr Gly Pro Cys Lys Ala Arg Ile Ile Arg1 5
10511PRTartificialReactive Site Region 5Glu Thr Gly Pro Cys Arg Ala
Met Ile Ile Arg1 5 10611PRTartificialReactive Site Region 6Met Thr
Gly Pro Cys Arg Ala Val Met Pro Arg1 5 10711PRTartificialReactive
Site Region 7Asp Asp Gly Pro Cys Lys Ala Ile Met Lys Arg1 5
10811PRTartificialReactive Site Region 8Asp Pro Gly Ile Cys Arg Gly
Tyr Ile Thr Arg1 5 10911PRTartificialReactive Site Region 9Asp Leu
Gly Leu Cys Arg Ala Asn Glu Asn Arg1 5 101011PRTartificialReactive
Site Region 10Asp Tyr Gly Pro Cys Arg Ala Leu Leu Leu Arg1 5
101111PRTartificialReactive Site Region 11Val Asp Asp Gln Cys Glu
Gly Ser Thr Glu Lys1 5 101211PRTartificialReactive Site Region
12Asp Glu Gly Leu Cys Ser Ala Asn Val Thr Arg1 5
101311PRTartificialReactive Site Region 13Lys Val Gly Arg Cys Arg
Gly Ser Phe Pro Arg1 5 101411PRTartificialReactive Site Region
14Asp Thr Gly Leu Cys Lys Glu Ser Ile Pro Arg1 5
101511PRTartificialReactive Site Region 15Val Val Gly Arg Cys Arg
Ala Ser Met Pro Arg1 5 101611PRTartificialReactive Site Region
16Val Thr Gly Pro Cys Arg Ala Ser Phe Pro Arg1 5
101711PRTartificialReactive Site Region 17Ser Ala Gly Pro Cys Met
Gly Met Thr Ser Arg1 5 101811PRTartificialReactive Site Region
18Tyr Thr Gly Pro Cys Lys Ala Arg Met Ile Lys1 5
101911PRTartificialReactive Site Region 19Tyr Thr Gly Pro Cys Arg
Ala His Phe Ile Arg1 5 102011PRTartificialReactive Site Region
20Lys Thr Gly Pro Cys Lys Ala Ala Phe Gln Arg1 5
102111PRTartificialReactive Site Region 21Asp Val Gly Arg Cys Arg
Ala Ser His Pro Arg1 5 102273PRTartificialmutated first Kunitz-type
domain of human TFP1-2 containing any of the following
substitutions D19A, Y20A, G21D, R24Q, R24K, L26Q, R29A, R29D, R29K,
or F42A 22Asp Ala Ala Gln Glu Pro Thr Gly Asn Asn Ala Glu Ile Cys
Leu Leu1 5 10 15Pro Leu Asp Tyr Gly Pro Cys Arg Ala Leu Leu Leu Arg
Tyr Tyr Tyr 20 25 30Asp Arg Tyr Thr Gln Ser Cys Arg Gln Phe Leu Tyr
Gly Gly Cys Glu 35 40 45Gly Asn Ala Asn Asn Phe Tyr Thr Trp Glu Ala
Cys Asp Asp Ala Cys 50 55 60Trp Arg Ile Glu Lys Val Pro Lys Val65
702324DNAartificialprimer sequence 23gctattacct tcttattatt tacc
242420DNAartificialprimer sequence 24gtgcgatgag taggggaagg
202520DNAartificialprimer sequence 25taatacgact cactataggg
202629DNAartificialprimer sequence 26gcctcgagtt aaaattgctt
cttccgata 292719DNAartificialprimer sequence 27ttactgctgt acctccacc
192819DNAartificialprimer sequence 28acaggacggc ttgaagatg
192918DNAartificialprimer sequence 29aacgacccct tcattgac
183019DNAartificialprimer sequence 30tccacgacat actcagcac 19
* * * * *
References