U.S. patent application number 11/280954 was filed with the patent office on 2006-06-15 for at4 receptor ligands as angiogenic, anti-angiogenic, and anti-tumor agents.
This patent application is currently assigned to Pacific Northwest Biotechnology Inc.. Invention is credited to Joseph W. Harding, John W. Wright.
Application Number | 20060128630 11/280954 |
Document ID | / |
Family ID | 35055141 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060128630 |
Kind Code |
A1 |
Harding; Joseph W. ; et
al. |
June 15, 2006 |
AT4 receptor ligands as angiogenic, anti-angiogenic, and anti-tumor
agents
Abstract
AT.sub.4 receptor agonists are potent activators of angiogenesis
and can be used to treat diseases that are characterized by
vascular insufficiency. AT.sub.4 receptor antagonists, which are
potent inhibitors of angiogenesis, and can be used as
anti-angiogenic agents for the treatment of cancer, diabetic
retinopathy, rheumatoid arthritis, psoriasis, atherosclerotic
plaque formation, and any disease process that is characterized by
excessive, undesired or inappropriate angiogenesis or proliferation
of endothelial cells.
Inventors: |
Harding; Joseph W.;
(Pullman, WA) ; Wright; John W.; (Pullman,
WA) |
Correspondence
Address: |
SEED INTELLECTUAL PROPERTY LAW GROUP PLLC
701 FIFTH AVE
SUITE 6300
SEATTLE
WA
98104-7092
US
|
Assignee: |
Pacific Northwest Biotechnology
Inc.
Pullman
WA
Washington State University Research Foundation
Pullman
WA
|
Family ID: |
35055141 |
Appl. No.: |
11/280954 |
Filed: |
November 16, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10675470 |
Sep 30, 2003 |
|
|
|
11280954 |
Nov 16, 2005 |
|
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|
Current U.S.
Class: |
435/6.1 ;
514/13.3; 514/19.3; 514/19.8 |
Current CPC
Class: |
A61K 38/05 20130101;
A61K 38/08 20130101; A61K 38/07 20130101; A61K 38/06 20130101; A61P
35/00 20180101 |
Class at
Publication: |
514/016 |
International
Class: |
A61K 38/08 20060101
A61K038/08 |
Claims
1. An AT.sub.4 receptor ligand comprising a compound of the
formula: R.sub.1ZR.sub.2R.sub.3X, wherein R.sub.1 is selected from
the group consisting of: Leu and norleucine; Z is a peptide bond or
a reduced peptide bond; R.sub.2 is Tyr; R.sub.3 is selected from
the group consisting of: Leu and Ile; X is selected from the group
consisting of: nothing, ZR.sub.4, ZR.sub.4--R.sub.5, and
ZR.sub.4--R.sub.5--R.sub.6, wherein Z is a peptide bond or a
reduced peptide bond; R.sub.4 is selected from the group consisting
of: hexamide, His, and Sar; R.sub.5 is selected from the group
consisting of: Pro, Sar, and Phe; R.sub.6 is selected from the
group consisting of: dPhe and amide group.
2. The composition according to claim 1, wherein the compound has
the formula: Nle-Y-I-(CH.sub.2).sub.6-amide.
3. The composition according to claim 1, wherein the compound has
the formula: Nle-Y-I-H.
4. The composition according to claim 1, wherein the compound has
the formula:
Nle.sub.1-Leu.sup.3-(CH.sub.2NH.sub.2).sup.3-4-AngIV.
5. The composition according to claim 1, wherein the compound has
the formula: L-.PSI.-Y-L-.PSI.-H-P-F.
6. The composition according to claim 1, wherein the compound has
the formula: Nle-Y-I-(CH.sub.2).sub.6-F-amide.
7. The composition according to claim 1, wherein the compound has
the formula: Nle-Y-I-Sar-Sar-dPhe.
8. A method selected from the group consisting of: (a) a method for
inhibiting the growth and metastasis of a non-solid tumor; (b) a
method for inhibiting the growth and metastasis of melanoma; and
(c) a method for altering MMP expression in pathologies associated
with over expression or under expression of matrix
metalloproteinase enzymes, comprising administering at least one
AT.sub.4 receptor ligand, wherein the ligand comprises a compound
of the formula: R.sub.1ZR.sub.2R.sub.3X, wherein R.sub.1 is
selected from the group consisting of: Leu and norleucine; Z is a
peptide bond or a reduced peptide bond; R.sub.2 is Tyr; R.sub.3 is
selected from the group consisting of: Leu and Ile; X is selected
from the group consisting of: nothing, ZR.sub.4, ZR.sub.4--R.sub.5,
and ZR.sub.4--R.sub.5--R.sub.6, wherein Z is a peptide bond or a
reduced peptide bond; R.sub.4 is selected from the group consisting
of: hexamide, His, and Sar; R.sub.5 is selected from the group
consisting of: Pro, Sar, and Phe; R.sub.6 is selected from the
group consisting of: dPhe and amide group.
9. A method for inhibiting extracellular matrix deposition by a
cell comprising administering at least one AT.sub.4 ligand, wherein
the ligand comprises a compound of the formula:
R.sub.1ZR.sub.2R.sub.3X, wherein R.sub.1 is selected from the group
consisting of: Leu and norleucine; Z is a peptide bond or a reduced
peptide bond; R.sub.2 is Tyr; R.sub.3 is selected from the group
consisting of: Leu and Ile; X is selected from the group consisting
of: nothing, ZR.sub.4, ZR.sub.4--R.sub.5, and
ZR.sub.4--R.sub.5--R.sub.6, wherein Z is a peptide bond or a
reduced peptide bond; R.sub.4 is selected from the group consisting
of: hexamide, His, and Sar; R.sub.5 is selected from the group
consisting of: Pro, Sar, and Phe; R.sub.6 is selected from the
group consisting of: dPhe and amide group.
10. The method according to claim 9, wherein inhibition of
extracellular matrix deposition comprises inhibition of at least
one of endothelial cell growth and vessel formation.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/675,470, filed Sep. 30, 2003, now pending,
which application is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to the general utility of
AT.sub.4 receptor ligands to alter blood vessel growth
(angiogenesis) in diseases associated with insufficient blood
supply or those associated with excessive, undesired or
inappropriate angiogenesis or proliferation of endothelial cells.
In particular, AT.sub.4 receptor ligands that inhibit angiogenesis
are extremely potent anti-cancer agents that block both the growth
of primary tumors and the development of metastatic tumors.
[0004] 2. Description of Related Art
[0005] The dominant therapeutic approaches that are currently
employed to treat cancer include surgical removal of primary
tumors, tumor irradiation, and parenteral application of
anti-mitotic cytotoxic agents. The continued dominance of these
long established therapies is mirrored by the lack of improvement
in survival rates for most cancers. Improvements that have been
observed can be traced not to therapeutic advancements but
diagnostic ones. In addition to limited clinical success,
devastating side effects accompany classic therapies. Both
radiation- and cytotoxic-based therapies result in the destruction
of rapidly dividing hematopoietic and intestinal epithelial cells
leading to compromised immune function, anemia, and impaired
nutrient absorption. Surgical intervention often results in a
release of tumor cells into the circulation or lymph systems from
which metastatic tumors can subsequently be established.
Furthermore, primary tumors often produce or generate endogenous
anti-angiogenic substances that suppress the growth of already
established but undetected micrometastases (O'Reilly et al., 1994).
Their removal, without accompanying treatment that is directed at
the micrometastases often leads to rapid expansion of the
metastatic tumors with fatal consequences.
[0006] Because of the shortcomings of classic treatment regimens
several new approaches to cancer therapy have been initiated over
the past decade. Most prominent among these are the development of
vaccines directed at cancer cells (Morris et al., 2003), the
related use of immunotoxins (antibodies linked to cytotoxic agents)
(Pastan and Kreitman, 2002), hormone-based therapies (Kenemans and
Bosman, 2003), and anti-angiogenics that are designed to limit
tumor growth and metastasis by inhibiting tumor vascularization
(Kerbel and Folkman, 2002). Although, the vaccine and immunotoxin
therapeutic approach has been under development for some time no
immuno-based therapy is now in use as a standard cancer treatment.
The utility of this approach is limited by two properties that are
inherent to cancer cells. First, cancers are derived from many cell
types all with different antigenic profiles. Therefore, each cancer
type would necessarily require its own specific set of therapeutic
reagents that would entail prohibitively expensive individual
development. Second, the antigenic targets of the reagents would
never be totally unique to the transformed cancer cells but would
also be represented on normal healthy cells resulting in unwanted
cytotoxic damage. Hormone-based therapies, while useful for the
treatment of a select group of cancers, will never be a treatment
option that is generally applicable to the vast majority of cancers
that are hormone insensitive. The successful development of a new
and generally useful cancer therapy must meet two critical
criteria. First, the treatment must target a molecular target or
process that is associated with most (if not all) cancers. Next,
the treatment must have little or no impact on normal cells. Unlike
immune- or hormone-based cancer therapies, anti-angiogenic-based
therapies meet both of these criteria.
[0007] Neovasularization of tumors is requisite for both the growth
and metastasis of tumors. The vascularization of tumor provides it
with a dedicated source of nutrients and oxygen that are essential
for continued growth. Without a dedicated blood supply the
availability of nutrients and oxygen, which must be furnished by
vessels external to the neoplasm, is diffusion limited restricting
tumor size to about 1 millimeter in diameter. In addition to
providing nutrients and oxygen, the tumor vasculature, which is
often abnormally permeable, acts as a conduit enabling cancer cells
to escape into the general circulation from whence they can
establish metastatic tumors at distant sites. The inverse
relationship between tumor vascularization and patient prognosis is
well recognized and reflects the fact that 90% of cancer patients
die of metastatic disease and not primary tumors. The realization
that most, if not all, tumors require a dedicated blood supply in
order to progress to a clinically relevant state spawned the notion
that inhibiting tumor neovasularization could control cancer
progression. This could be accomplished by blocking the process of
angiogenesis in which vascular endothelial cells divide and migrate
to produce branching of established vessels. A particularly
attractive aspect of targeting angiogenesis is that the frequency
of cancer is increased in older adults who possess quiescent
endothelial cells with a normal turnover rate of 1000 days and
occurs only during wound healing and menses. Thus, anti-angiogenic
drugs meet the primary criteria for a general anti-cancer agent-
i.e., broad applicability and minimal effects on normal tissues.
Another advantage offered by anti-angiogenic drugs is that they
target a cell population (endothelial cells) that is genetically
stable and far less likely to support the development of drug
resistance that is regularly seen with drugs directed at cancer
cells. A final advantage offered by anti-angiogenics is their ready
access to endothelial target cells following parenteral
application.
BRIEF SUMMARY OF THE INVENTION
[0008] A method of increasing angiogenesis in pathological
conditions associated with insufficiencies in vascular perfusion,
by producing an AT.sub.4 receptor agonist; and administering the
AT.sub.4 receptor agonist. A method of inhibiting angiogenesis in
pathological conditions, where increased angiogenesis and
coincidental vascular perfusion are clinically detrimental, by
producing an AT.sub.4 receptor antagonist; and administering the
AT.sub.4 receptor antagonist. A method of inhibiting the growth and
metastasis of solid tumors, by producing an AT.sub.4 receptor
antagonist; and administering the AT.sub.4 receptor antagonist. A
method of inhibiting the growth and metastasis of breast cancer, by
producing an AT.sub.4 receptor antagonist; and administering the
AT.sub.4 receptor antagonist.
[0009] In any of the above methods the AT.sub.4 receptor ligand can
be administered locally, intravascularly, intramuscularly,
intraperitoneally, subcutaneously, or orally.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0010] FIGS. 1A and 1B shows the effect of the AT.sub.4 receptor
agonist, Nle.sup.1-AngIV (NORLEU), and the AT.sub.4, receptor
antagonist, Nle.sup.1,
Leu.sup.3-.PSI.(CH.sub.2--NH.sub.2).sup.3-4-Ang IV (NORLEUAL), on
the growth of human umbilical vein endothelial cells.
[0011] FIG. 2 shows the effect of the AT.sub.4 receptor antagonist
on the net deposition of extracellular matrix protein by human
dermal fibroblasts and C6 glioma cells.
[0012] FIG. 3 shows the effect of various AT.sub.4 receptor ligands
on the expression and secretion of matrix metalloproteinases by
rabbit cardiac fibroblasts.
[0013] FIG. 4 shows the effect of the AT.sub.4 receptor antagonist,
NORLEUAL, on the net deposition of extracellular matrix protein by
human umbilical vein endothelial cells and +SA-WAZ-2T murine breast
cancer cells.
[0014] FIGS. 5A and 5B show the effect of the AT.sub.4 receptor
antagonist, NORLEUAL, on the ex vivo development of new blood
vessels in the rat aortic ring angiogenesis assay.
[0015] FIGS. 6A and 6B show the effect of various AT.sub.4 receptor
ligands on in vivo angiogenesis in the rat disc angiogenesis
assay.
[0016] FIG. 7 shows the inhibitory effect of the AT.sub.4 receptor
antagonist, NORLEUAL, on the growth of +SA-WAZ-2T murine primary
tumors in mice.
[0017] FIGS. 8A and 8B shows the inhibition of tumor angiogenesis
in mice following application of the AT.sub.4 receptor antagonist,
NORLEUAL.
[0018] FIG. 9 shows inhibition in the development of lung
metastasis in mice following injection of +SA-WAZ-2T cells into the
tail vein and subsequent application of the AT.sub.4 receptor
antagonist, NORLEUAL.
[0019] FIG. 10 shows the inhibition of MDA-MB-231 human breast
cancer growth by the AT.sub.4 receptor antagonist, NORLEUAL.
[0020] FIG. 11 shows the inhibition of human prostate cancer growth
by an AT.sub.4 receptor antagonist.
[0021] FIG. 12 shows the effect of an AT.sub.4 receptor antagonist
on the deposition of extracellular matrix protein by human dermal
fibroblasts and C6 glioma cells.
[0022] FIG. 13 shows the effect of an AT.sub.4 receptor antagonist
on the deposition of extracellular matrix protein by human
umbilical vein endothelial cells and +SW-WAZ-2T murine breast
cancer cells.
[0023] FIG. 14 shows the inhibitory effect of an AT.sub.4 receptor
antagonist on the growth of +SW-WAZ-2T murine primary tumors on
mice.
[0024] FIG. 15 shows the inhibition of tumor angiogenesis in mice
following application of an AT.sub.4 receptor antagonist.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The potential ability of AT.sub.4 receptor ligands to alter
the angiogenic process was first suggested by the observation that
the agonist, Nle.sup.1-AngIV can augment the rate of
.sup.3H-thymidine incorporation in cultured bovine coronary venular
endothelial cells (CVEC) (Hall et al., 1995). These initial
observations were extended to human endothelial cells (FIG. 1A)
where application of the high affinity agonist, Nle.sup.1-Ang IV
(Sardinia et al., 1994; Wright et al., 1999), produces a
dose-dependent increase in growth. Human umbilical vein endothelial
cells (HUVEC) were grown in EGM (Clonetics) and 10% calf serum for
four days in the absence (control) or presence of 10.sup.-8 M,
10.sup.-10 M, or 10.sup.-12 M Nle.sup.1-Ang IV. Cell proliferation
was estimated by monitoring mitochondrial activity with the
redox-sensitive substrate
3-[4,5-Dimethylthiazol-yl]-2,5-diphenyltetrazolium bromide (MTT)
(Carmicheal et al., 1987). These data demonstrated that
Nle.sup.1-Ang IV stimulated endothelial cell proliferation at all
doses examined in a dose-dependent manner (Mean.+-.SEM, n=6;
p<0.001) The maximum observed increase was 330% of control
levels. These results support the notion that AT.sub.4 receptor
agonists, like Nle.sup.1-Ang IV, can be used to stimulate
endothelial cell proliferation and processes like angiogenesis that
rely on increased endothelial cell growth.
[0026] Most relevant for anti-angiogenic cancer treatment is the
ability of AT.sub.4 antagonists to inhibit endothelial cell growth
in culture. Attenuated growth has been observed with both CVECs and
with HUVECs (FIG. 1B). After four days of treatment with 10.sup.-10
M Nle.sup.1, Leu.sup.3-.PSI.(CH.sub.2--NH.sub.2).sup.3-4-Ang IV
(NORLEUAL), a potent AT.sub.4 receptor antagonist (Kramar et al.,
2001), growth of CVECs was reduced to 25% of control (Mean.+-.SEM;
n=8; p<0.001). Treatment of HUVECs with NORLEUAL resulted in a
dose-dependent inhibition of growth with the largest decease (to
39% control) at 10.sup.-6M (FIG. 1B). Cell proliferation was again
estimated using the MTT assay. Together these data spawned the idea
that angiogenesis could potentially be augmented by agonists and
inhibited by antagonists of the AT.sub.4 receptor.
[0027] A second set of observations regarding the function of
AT.sub.4 receptors indicated that AT.sub.4 receptor modulation had
a dramatic impact on extracellular matrix (ECM) structure and
remodeling. While examining the effect of AT.sub.4 receptor ligands
on fibroblasts and C6 glioma cells (transformed astrocytes), a near
total loss of deposited ECM was observed following antagonist
treatment (FIG. 2; FIG. 12[color version]). Human dermal
fibroblasts and C6 glioma cells (astrocyte tumor) were treated with
10.sup.-12 M NORLEUAL for 3 days. Cells were stripped with 0.25%
Triton X-100 for 10 minutes and stained with either Coomassie blue
(gliomas) or anti-fibronectin (fibroblasts). Stained dots remaining
after treatment are nuclei. Although the mechanism responsible for
the lose of ECM proteins has yet to be fully elucidated, a
contributing factor could be AT.sub.4 receptor-dependent
alterations in the expression of matrix metalloproteinases.
Application of AT.sub.4 receptor ligands to rabbit cardiac
fibroblasts initiated marked changes in the expression of various
matrix metalloproteinases (MMPs) (FIG. 3). The data presented in
FIG. 3 is zymographic data. Conditioned media from cardiac
fibroblasts treated with various AT.sub.4 receptor ligands for 12
hours was loaded and run on a 10% SDS-polyacrylamide gel containing
the 1% gelatin, an MMP substrate. After renaturation and activation
of MMPs, the gel was incubated at 37.degree. C. for 24 hours to
allow for the degradation of gelatin at sites within the gel where
MMPs reside. These sites are seen as unstained lytic bands on a
background of stained and undegraded gelatin. Lane one is control
media from cells with no exposure to AT.sub.4 receptor ligands.
Lanes 2-4 contained media from cells treated with Nle.sup.1-Ang IV,
a putative AT.sub.4 receptor agonist, at concentrations of 1 nM, 10
nM, and 100 nM respectively. Lanes 5-10 contained media from cells
treated with 10.sup.-6 M concentrations of various putative
agonists or antagonists (see FIG. 3 and accompanying table for
details). These data indicate that AT.sub.4 receptor ligands can
dramatically alter the expression of several MMPs and suggest that
AT.sub.4 receptor ligands may be useful for altering MMP expression
in pathologies associated with either under or over expression of
MMPs.
[0028] The consistent ability of AT.sub.4 receptor antagonists to
dramatically inhibit the net deposition of ECM protein in various
cells (FIG. 2) and the essential involvement of the ECM in
mediating endothelial cell growth, motility, and vessel formation
made it imperative to assess the impact of AT.sub.4 antagonists on
endothelial ECM. As seen in FIG. 4 (FIG. 13[color version]),
application of the AT.sub.4 antagonist NORLEUAL initiates a
dramatic reduction in the density of the endothelial-associated
ECM. HUVECs and the mouse breast cancer cell line, +SA-WAZ-2T was
exposed to the AT.sub.4 receptor antagonist NORLEUAL at 10.sup.-12M
for 3 days. Cells were then stripped with 0.25% Triton X-100 and
stained with Coomassie blue to visualize total ECM protein. Without
an ECM platform endothelial cells fail to migrate and are unable to
stabilize new blood vessels.
[0029] The ability of AT.sub.4 receptor antagonists to inhibit
endothelial cell growth and ECM deposition implies that they should
exhibit anti-angiogenic activity as well. This prediction has been
borne out in studies examining the anti-angiogenic activity of the
AT.sub.4 receptor antagonist, NORLEUAL, using an ex vivo aortic
ring model (FIG. 5) and an in vivo disc angiogenesis assay system
in rats (FIG. 6). The data shown in FIG. 5 illustrate the dramatic
ability of an AT.sub.4 receptor antagonist to inhibit neovascular
growth. Rat aortic rings were incubated for 24 hours in a growth
factor rich medium (EGM-2) followed by 3 days of incubation in a
basal medium (control) or basal media with varying concentrations
of NORLEUAL. The data shown in FIG. 5A compare an untreated control
ring and a ring treated with 10-6 M NORLEUAL. FIG. 5B illustrates
the dose response effect of NORLEUAL on the inhibition of vessel
growth (Mean.+-.SEM, n=8; p<0.02 for 10.sup.-6 M). These results
have been extended to an in vivo model in which growth of new
vessels into a subcutaneously implanted disc (sandwich of surgical
sponge between impermeable membranes with test compound in the
middle) can be quantitated. An example of the type of data that has
been generated using the disc angiogenesis assay is shown in FIG.
6A. FIG. 6B shows the results with several AT.sub.4 receptor
antagonists and the agonist Nle.sup.1-AngIV. Disks (1 cm diameter)
composed of surgical sponge sandwiched between impermeable
membranes were implanted subcutaneously in the backs of rats. In
the center of the disks was a pellet containing the test material.
The disks were removed 10 days after implantation, paraffin
sectioned, stained with Coomassie blue, and analyzed by
quantitative image analysis methods to determine the vascularized
area. FIG. 6A shows example control and treated disks that have
been stained and sectioned. FIG. 6B shows summary data for several
AT.sub.4 receptor ligands. Data from discs containing no drug
(control), an AT.sub.4 receptor agonist (Cpnd 1), or an AT.sub.4
receptor antagonist (Cpnds 2-4). Cmpd 2 is NORLEUAL. Each disc
contained 10 micrograms of drug. Data is presented as the percent
of the total disc area that is vascularized (Mean.+-.SEM; n=8).
These data demonstrate the ability of three antagonists (compounds
2-4) to inhibit angiogenesis while the agonist (compound 1)
exhibited a trend toward enhancing angiogenesis.
[0030] The anti-angiogenic activity of AT.sub.4 receptor
antagonists predicts that these compounds should also possess
anti-tumor activity in vivo. To test this prediction mice were
implanted with 5.times.10.sup.-5+SA-WAZ-2T mouse breast cancer
cells (a highly aggressive and metastatic cell line) (Danielson et
al., 1980) directly into the mammary gland in the presence or
absence of a slow-release pellet containing the AT.sub.4
antagonist, NORLEUAL at various concentrations (FIG. 7; FIG.
14[color version)). Mouse mammary glands were injected with
5.times.10.sup.5 cells. An Elvax pellet containing an inactive
angiokine (control) or NORLEUAL was simultaneously inserted into
the gland. Tumors were removed and weighed at various time points.
Data shown represents one of three experiments that yielded
identical results. The insert shows typical tumors from control and
treated mice. Arrows indicate large blood vessels in the control
tumor. NORLEUAL dramatically inhibited primary tumor growth as
measured by tumor volume. The highest dose examined inhibited
growth more than 97%. Equally dramatic as the reduced size of the
tumors was their lack of vascularization. This can be seen in FIG.
7 (see insert) and FIG. 8 which shows Factor VIII stained sections
of highly vascularized control tumors and treated tumors that were
nearly avascular--thus reconfirming that AT.sub.4 receptor
antagonists inhibit angiogenesis. Tumors were harvested after 5
weeks of drug application and stained for Factor VIII. FIG. 8A
(FIG. 15[color version]) shows representative high power fields of
sections of control and treated murine mammary tumors. The
quantitative data shown in FIG. 8B indicates the number of visible
blood vessels in an average high power field. Data are mean.+-.SEM,
n=6.
[0031] In addition to inhibiting primary tumor growth, AT.sub.4
receptor antagonists are also effective at preventing the growth of
lung metastases (as assessed by total lung weight and the presence
of metastatic tumor nodules) in mice that have had breast cancer
cells injected via the tail vein (FIG. 9). In these experiments the
drug was applied using Elvax slow-release pellets that were
implanted into the gluteus maximus muscle coincident with the
injection of tumor cells into the tail vein. Mice were injected
with 5.times.10.sup.5 murine breast cancer cells and bilaterally
implanted with Elvax pellets containing 0.3 mg of NORLEUAL. Lungs
were harvested 7 weeks after tumor cell injection and weighed. The
results from two combined experiments demonstrated that lungs from
treated mice exhibited no gross or microscopic indication of
metastases (Mean.+-.SEM. N=8). Visible nodules that were seen in
the lungs of control mice were absent from treated mice. Total
pulmonary metastatic burden was assessed by comparing lung weights
of control and treated mice to naive mice that did not receive any
tumor cells. In order to compare just the added lung weight due to
tumor infiltration, tumor burden was calculated by subtracting the
mean lung weight of wild type untreated controls from the weight of
lungs from experimental groups. The mean lung weight of the
untreated tumor controls was normalized to 100. Typically, the lung
weights of cancer injected, non-treated mice were 50% greater than
non-injected controls and treated mice. Spleen weight, another
indication of tumor burden, was also normal in treated mice.
[0032] Because of the marked effectiveness of AT.sub.4 receptor
antagonists to inhibit the growth and metastasis of breast cancer
in vivo, and the generally disappointing activity of
anti-angiogenic molecules seen in clinical trials (Kerbel and
Folkman, 2002), we decided to ascertain whether these drugs might
have a direct effect on tumor cells as well as inhibiting
angiogenesis. The growth of MDA-MB-231 cells, an aggressive
estrogen-independent human cell line was inhibited by all
concentrations that were examined (FIG. 10). Growth was assessed
using the mitochondrial activity dye MTT after four days in
culture. Growth was reduced to less than 25% of control by a
concentration of NORLEUAL of 10.sup.-12 M (Mean.+-.SEM; n=6).
Similar results were observed when NORLEUAL was applied at
10.sup.-6 M to DU-145 cells (Mean.+-.SEM; n=6), a human prostate
cancer cell line (FIG. 11). The unusual reversed dose-response
curve seen with the MDA-MB-231 cells may represent differential
effects on multiple receptor subtypes with varied ligand
affinities. These studies demonstrated that in addition to
inhibiting angiogenesis, which indirectly impacts tumor growth and
metastatic potential, AT.sub.4 receptor antagonists did, in fact,
interact directly with tumor cells resulting in a dramatic
inhibition of tumor growth in culture (FIG. 10, FIG. 11), a near
total loss of secreted ECM proteins (FIG. 4), and alterations in
the expression of matrix metalloproteinases (data not shown). The
ability of AT.sub.4 receptor antagonists to inhibit both the
angiogenic process as well as the proliferation of human cancer
cells makes them unique among anticancer agents and provides a
plausible explanation for their dramatic ability to inhibit tumor
growth and metastasis.
[0033] Definition: An AT.sub.4 receptor ligand is defined as any
molecule that can compete for the binding of .sup.125I-angiotensin
IV (VYIHPF) to plasma membranes from bovine adrenal glands, which
are enriched in AT.sub.4 receptors, with a K.sub.I< or
=10.sup.-7 M.
[0034] It is to be understood that the above-described arrangements
are only illustrative of the application of the principles of the
present invention. Alternative arrangements may be devised by those
skilled in the art without departing from the spirit and the scope
of the present invention. The appended claims are intended to cover
such modifications and arrangements. Thus, while the present
invention has been shown in the drawings and fully described above
with particularity and detail in connection with what is presently
deemed to be the most practical and preferred embodiments of the
invention, it will be apparent to those of ordinary skill in the
art that numerous modifications, including but not limited to the
application of the present invention to treat: lung cancer,
prostrate cancer, ovarian cancer, gastrointestinal cancers,
melanoma or to treat nonsolid tumors such as leukemia, Hodgkin's
disease, multiple myeloma, other hematopoietic-based cancers.
AT.sub.4 receptor agonists are potent activators of angiogenesis
and can be used to treat diseases that are characterized by
vascular insufficiency. In the alternative, AT.sub.4 receptor
antagonists, which are potent inhibitors of angiogenesis, and can
be used as anti-angiogenic agents for the treatment of cancer,
diabetic retinopathy, rheumatoid arthritis, psoriasis,
atherosclerotic plaque formation, and any disease process that is
characterized by excessive, undesired or inappropriate angiogenesis
or proliferation of endothelial cells, may be performed without
departing from the principles and concepts set forth herein.
* * * * *