| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Regular Articles |
Craniofacial Developmental Biology and Regeneration Branch, National Institute of Dental and Craniofacial Research, NIH, Bethesda, Maryland 20892 [M. L. P., S. H., A. M. L., H. K. K.], and Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, Japan [M. M., M. N.]
| ABSTRACT |
|---|
|
|
|---|
1 and
1 chains, respectively. We reported recently that a scrambled C16 sequence, C16S (DFKLFAVTIKYR), acts as an antagonist to both peptides. Here, we have identified a stronger antiangiogenic peptide, C16Y (C16S with a T to Y substitution), with potent activity in several biological assays including tumor growth. C16Y is more potent in promoting endothelial cell attachment and inhibiting attachment to laminin-1 than either C16 or C16Y. Disruption of tube formation by C16Y is also observed at concentrations at least five times lower than C16S. The minimal active sequence was found to be DFKLFAVY. C16Y is more potent in blocking C16-induced chick chorioallantoic membrane angiogenesis than C16S. Tumor growth studies on the chick chorioallantoic membrane showed that C16Y reduces breast cancer cell growth without affecting cell proliferation. This result suggests that angiogenesis is being inhibited by the peptide. In vivo animal studies demonstrated that C16Y treatment significantly reduced tumor growth and decreased tumor vessel number, as compared with controls, additionally suggesting that angiogenesis was affected. These results indicate that we have identified a more potent antiangiogenesis inhibitor peptide that may be used as a therapeutic to treat cancer. | INTRODUCTION |
|---|
|
|
|---|
In our laboratory, we have also identified >20 peptides from laminin-1, a large ECM protein composed of three chains,
1, ß1, and
1, that can promote angiogenesis in vivo (9
, 10) . Two of the most potent sites, A13 and C16, are redundant angiogenic sites present in homologous regions of the
1 and
1 chain, respectively (11, 12, 13)
. These sequences bind to the endothelial cell integrins
vß3 and
5ß1 (14)
. These peptides have also been shown to promote adhesion, tube formation, and angiogenesis in the chick CAM assay. Although these sequences bind to integrins, they do not seem to signal through mitogen-activated protein kinase or several serine or threonine kinases, and their mechanism of action has not yet been identified. The
1 chain is present in 11 of the laminins; therefore, C16 is present in at least 11 of the 13 laminins (15)
. The A13 sequence is also highly conserved in the
chains; therefore, this sequence is present twice in some of the laminins including laminin-1 and -3 (16)
. Because of the putative significance of this site in angiogenesis and its related diseases, it has been important to identify an antagonist that could block its activity. We have reported previously a scrambled peptide sequence, C16S, that can inhibit C16 and bFGF-induced angiogenesis in the CAM assay (14)
. Here, we have identified a modified, and at least five times more potent sequence, C16Y, that can inhibit in vivo angiogenesis and tumor growth in mice. Furthermore, we have identified its minimum active sequence and have determined that it has homology to fibronectin.
| MATERIALS AND METHODS |
|---|
|
|
|---|
|
Cell Adhesion and Competition Experiments.
Cell adhesion assays were performed on 96-well plates coated overnight with either 0.5 µg of laminin-1 or synthetic laminin peptides (05 µg) as described previously (9)
. Wells were rinsed with PBS, blocked with 2 mg/ml of BSA, and rinsed again with PBS. Cell adhesion was performed in 0.1 ml of RPMI 1640 containing 35,000 HUVECs. Competition experiments were done in laminin-1-coated plates in the presence of 0100 µg/ml of competing peptide as specified. Controls were wells coated only with BSA. After a 1.5-h incubation at 37°C, unbound cells were decanted, and attached cells were fixed and stained with 20% methanol/0.2% crystal violet. Dishes were extensively rinsed, and bound dye was solubilized in 2% SDS and quantitated at 600 nm. Assays were done in triplicate at least three times.
Endothelial Cell Tube Formation.
Tube-forming assays were performed as described previously (14)
. Matrigel (200 µl/well) was used to coat 48-well dishes. HUVECs (24,000 cells/well) were plated in RPMI 1640 containing 10% bovine calf serum, defined and supplemented (HyClone Laboratories, Inc., Logan, UT), and 100 mg/liter of endothelial cell growth factor (Collaborative Biomedical). Tube assays were performed using 075 µg/ml of peptide as specified. Controls contained only medium. Cells were fixed and stained after 16 h with Diff-Quick fixative (methanol) and solution II [6.25% (w/v) each of azure A and methylene blue; Dade AG, Dudingen, Switzerland], and the tubes were scored by a blinded observer. Peptides were tested at least in triplicate, and the assays were repeated a minimum of three times.
Chick CAM Assay.
The CAM assay was performed using 10-day-old embryonated eggs (CBT, Charlestown, MD) as described previously (18)
. On embryonal day 3,
4 ml of ovalbumin was removed from each egg. After opening windows on embryonal day 10, the angiogenic stimulus, C16, and test competitor peptides in 5 µl of distilled water were applied to the CAM after drying on 13-mm diameter quartered plastic coverslips (Thermanox; Nalge, NUNC International, Naperville, IL). Three days later, the eggs were scored for a positive response and photographed. The positive control was bFGF, and the negative control was the vehicle water. Experiments were repeated twice using a minimum of 11 eggs for each data point.
Tumor Growth.
MDA-231 breast cancer cells (5 x 105 cells; a gift of Dan Welch, Pennsylvania State University, University Park, PA) mixed (1:4) with Matrigel were injected s.c. into nude mice. Daily peptide i.p. injections were started when the tumors reached a volume of 200300 mm3 (days 79 after initial tumor injection). Peptides injected included C16 (1 mg/day) and C16Y at 0.2, 0.5, and 1.0 mg/day. Controls were mice injected daily with vehicle (water). Tumor growth was monitored with a caliper, and volume was determined using the formula width2 x length x 0.52. Tumors were excised, weighed, and fixed with formalin at the end of the experiment. Vessel number was determined by staining sections with a CD-31 antibody (16)
and counting 6 fields per section per mouse (n = 2 sections/mouse; total 3 mice).
We also investigated the growth of MDA-MB-231 tumor cells using the chick CAM (19) . Tumor cells (1 x 106 cells/0.1 ml) in RPMI 1640 were mixed with the indicated amount of peptide, and then mixed 1:1 with a neutralized collagen I solution (4.6 mg/ml collagen type I) and added directly onto the CAM of a 7-day-old embryo. After a 7-day incubation, tumors were excised and weighed. This experiment was repeated twice with each data point tested in at least six replicates.
Cell Proliferation.
Proliferation of MDA-MB 231 cells was quantified using a Cell Titer 96 Aqueous Cell Proliferation assay kit (Promega, Madison, WI). Cells were plated on four 96-well dishes at 5 x 103 cells/well and cultured in AIM-V serum-free medium (Life Technologies, Inc., Gaithersburg, MD). After 1 h, peptides C16 and C16Y were added at a final concentration of 100 µg/ml. A separate dish was used to quantitate proliferation at 2, 24, 48, and 72 h by reading absorbance at 490 nm on an Emax plate reader. Each experiment was repeated in triplicate two times.
| RESULTS |
|---|
|
|
|---|
1 chain-derived peptide, C16, was angiogenic in vivo and that a scrambled version of this peptide, C16S, had strong antiangiogenic activity (10
, 11) . Here, several scrambled C16 peptide sequences were synthesized to determine whether we could identify another sequence that would posses a more potent antiangiogenic activity than that observed with C16S (Table 1)
|
C16Y Most Actively Disrupts Tube Formation.
Endothelial cells form capillary-like structures when placed on Matrigel, a basement membrane matrix (19
, 20)
. Disruption of endothelial cell tube formation is highly suggestive of the ability of a compound to either promote or inhibit angiogenesis (10
, 11)
. We had determined previously that peptide C16, which is angiogenic, and C16S, its antagonist, were active in this assay at doses >50 µg/ml (14)
. To identify other peptides that might posses a stronger tube-disrupting activity, a tube-forming assay was used in which soluble peptide was added at doses that ranged between 10 and 75 µg/ml. As expected, C16 and C16S disrupted tube formation at 50 and 75 µg/ml, with little or no activity observed at lower doses (Fig. 2)
. In contrast, C16Y strongly disrupted tube formation at all of the doses tested, even as low as 10 µg/ml, a dose five times lower than that at which C16 or C16S are active. The other peptides, C16J, C16-3 (not shown), and C16L, showed no activity at the lower doses and only slight tube disruption at higher concentrations.
|
|
|
40% of its control C16 (P < 0.05). More vessels were observed in the untreated tumors and in those tumors treated with C16 than in the tumors treated with C16Y (7.5 ± 0.45 versus 9.6 ± 0.23 versus 5.1 ± 0.16; P
0.027). Whether the difference in tumor growth was because of inhibition of angiogenesis or because of an effect on cell proliferation was still uncertain.
|
C16Y Inhibits the Growth of Primary Tumors.
To additionally confirm the antiangiogenic effect of C16Y, we used a second in vivo system in which nude mice bearing a pre-established 200300 mm3 breast carcinoma tumor were treated for 710 days with peptide. Tumor growth was either significantly (P < 0.028) inhibited (Fig. 5A)
or its size was reduced to
33% after a week of treatment with 1 mg of C16Y (Fig. 5B)
. In contrast, during the same period, control tumors and those of animals treated with C16 grew 1.72.5 times their initial size. Although we had expected C16 animal tumors to grow more rapidly than the control, it was interesting to note that C16 treatment did not significantly affect tumor growth (Fig. 5, A and B)
. This could be explained by the production of high levels of growth factors that are endogenously secreted by the tumor itself. Lower C16Y doses (0.2 and 0.5 mg) also led to a dose-dependent reduction of initial tumor burden (Fig. 5B)
. However, when daily administration of the antiangiogenic peptide was stopped on day 7, the tumors began to grow rapidly (Fig. 5B)
. The tumors of those animals treated with the lowest C16Y dose (0.2 mg) grew the fastest, approaching control tumor volume within 3 days. Tumors of animals that received 0.5 mg of C16Y daily grew more slowly, and those that received the highest doses reached initial tumor size
6 days after peptide treatment was stopped. These results strongly suggest that C16Y can reduce tumor growth via its antiangiogenic activity.
|
| DISCUSSION |
|---|
|
|
|---|
1 chain (10, 11, 12)
. This site recognizes integrins
5ß1 and
vß3. A scrambled version of this peptide, C16S, was created as a negative control but had unexpected antagonist activity (14)
. The scrambled peptide bound to the receptor and promoted cell adhesion, but blocked adhesion to the parent peptide C16 and to laminin-1. This peptide also blocked peptide- and fibroblast growth factor-mediated angiogenesis in the chick CAM assay. Here, we have searched for a more potent antagonist using the sequence present in C16S and making different amino acid substitutions. One peptide, C16Y, which contains a single amino acid substitution of a T to a Y, is 510-fold more potent in its antagonistic activity than C16S. This peptide is also active in vivo and can inhibit tumor growth in a dose-dependent manner when given daily as an i.p. injection. C16Y likely acts on tumor growth by blocking angiogenesis, because it had no effect on tumor cell proliferation in vitro.
Peptide C16Y is not toxic and may interfere with the normal functions of laminin-1, as well as other molecules that use the integrin
5ß1 and
vß3 receptors. Angiogenesis has been shown to require the activity of integrin
vß3 (23
, 24)
. Laminin-1 has many biological activities that would promote tumor growth and angiogenesis (25)
. Laminin-1 promotes cell adhesion, migration, invasion, and protease activity, and laminin-1-adherent cells are more malignant than nonadherent cells or fibronectin-adherent cells. Because several laminin-1 peptides can modulate tumor growth and angiogenesis in vivo, endogenous laminin-1 is likely physiologically active in vivo during tumor growth and angiogenesis, although this has not yet been demonstrated directly in vivo. We believe that the C16 site on laminin-1 is functionally important in vivo in both tumor growth and angiogenesis, and that this active site on laminin-1 is blocked by the C16Y peptide. In our previous screens for finding active sites for malignancy on laminin-1, C16 and its homologue on the
chain, A13, were identified as being the most potent on their respective chains (9
, 10
, 13
, 16
, 26)
. Furthermore, either or both of these redundant active sites are present in all of the laminin-1 isoforms.
When initially preparing control peptides for C16, many different randomly scrambled peptides were prepared. Most were inactive, but some had low activity, and C16S had the highest activity (12)
. A comparison study of the C16Y sequence (DFKLFAVYIKYR) was made for amino acid homology to other short sequences using National Center for Biotechnology Information Protein BLAST search, and the results indicate that there was 66% (8 of 12) identity to the fibronectin sequence (residues 10231033) in c-elegans (DYKYFAVYYR; Ref. 27
). We have prepared this peptide and find that it has no activity for blocking endothelial cell tube formation.3
It had already been established that VAYI was the minimal active sequence for A13 and that this sequence is highly conserved among the
chains (16)
. With C16, the minimal active sequence was found previously to be YVRL (26)
. Although different in sequence, these peptides are located in homologous sites on laminin-1 and recognize the same cellular receptors. The minimal active sequence for C16Y is DFKLFAVY. All of these peptides regulate angiogenesis and recognize the promiscuous integrin
vß3 (28
, 29)
.
Many sites for angiogenesis have been identified on laminin-1, but only one site has been found to be an inhibitor of angiogenesis, YIGSR, which is located on the ß1 chain (residues 929933; Refs. 30
, 31
). This peptide also blocks tumor growth and lung colonization but is much less active (
10-fold) than the C16Y peptide described here (32
, 33). C16Y is the most potent peptide described to date and may function as an antagonist to integrins during angiogenesis.
| FOOTNOTES |
|---|
1 To whom requests for reprints should be addressed, National Institute of Dental and Craniofacial Research, NIH Building 30, Room 433, 30 Convent Drive, MSC 4370, Bethesda, MD 20892. Phone: (301) 496-4069; Fax: (301) 402-0892; E-mail address: hkleinman{at}dir.nidcr.nih.gov ![]()
2 The abbreviations used are: ECM, extracellular matrix; bFGF, basic fibroblast growth factor; CAM, chorioallantoic membrane; HUVEC, human umbilical vascular endothelial cell. ![]()
Received 11/20/02. Revised 5/26/03. Accepted 6/12/03.
| REFERENCES |
|---|
|
|
|---|
vß3 integrin and inhibits angiogenesis. J. Biol. Chem., 276: 31959-31968, 2001.
-1 and ß-1 chain peptides active for endothelial cell adhesion, tube formation, and aortic sprouting. FASEB J., 13: 53-62, 1999.
-1 chain. Circ. Res., 84: 688-694, 1999.
1 and
1 chains are angiogenic in vivo via integrins
5ß1 and
Vß3. Exp. Cell Res., 285: 189-195, 2003.[Medline]
1 chain peptide, C-16 (KAFDITYVRLKF), promotes migration, MMP-9 secretion, and pulmonary metastasis of B16F10 mouse melanoma cells. Br. J. Cancer, 86: 1169-1173, 2002.[Medline]
-1 chain. Exp. Cell Res., 249: 386-395, 1999.[Medline]
-1 site and its antagonist bind through the
vß3 and
5ß1 integrins. FASEB J., 15: 1389-1397, 2001.
chains. Biochemistry, 40: 15310-15317, 2001.[Medline]
v integrins. Science (Wash. DC), 270: 1500-1502, 1995.
v ß 3 for angiogenesis. Science (Wash. DC), 264: 569-571, 1994.
-1 chain by systematic peptide screening. J. Biol. Chem., 272: 32198-32205, 1997.
v ß 3. Important Adv. Oncol., : 69-87, 1996.
This article has been cited by other articles:
![]() |
Y. Fu, M. L. Ponce, M. Thill, P. Yuan, N. S. Wang, and K. G. Csaky Angiogenesis Inhibition and Choroidal Neovascularization Suppression by Sustained Delivery of an Integrin Antagonist, EMD478761 Invest. Ophthalmol. Vis. Sci., November 1, 2007; 48(11): 5184 - 5190. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. Akalu, J. M. Roth, M. Caunt, D. Policarpio, L. Liebes, and P. C. Brooks Inhibition of Angiogenesis and Tumor Metastasis by Targeting a Matrix Immobilized Cryptic Extracellular Matrix Epitope in Laminin Cancer Res., May 1, 2007; 67(9): 4353 - 4363. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. C. Sroka, M. E. Pennington, and A. E. Cress Synthetic D-amino acid peptide inhibits tumor cell motility on laminin-5 Carcinogenesis, September 1, 2006; 27(9): 1748 - 1757. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Hibino, M. Shibuya, M. P. Hoffman, J. A. Engbring, R. Hossain, M. Mochizuki, S. Kudoh, M. Nomizu, and H. K. Kleinman Laminin {alpha}5 Chain Metastasis- and Angiogenesis-Inhibiting Peptide Blocks Fibroblast Growth Factor 2 Activity by Binding to the Heparan Sulfate Chains of CD44 Cancer Res., November 15, 2005; 65(22): 10494 - 10501. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. Hallmann, N. Horn, M. Selg, O. Wendler, F. Pausch, and L. M. Sorokin Expression and Function of Laminins in the Embryonic and Mature Vasculature Physiol Rev, July 1, 2005; 85(3): 979 - 1000. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. Ambesi, R. M. Klein, K. M. Pumiglia, and P. J. McKeown-Longo Anastellin, a Fragment of the First Type III Repeat of Fibronectin, Inhibits Extracellular Signal-Regulated Kinase and Causes G1 Arrest in Human Microvessel Endothelial Cells Cancer Res., January 1, 2005; 65(1): 148 - 156. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Hibino, M. Shibuya, J. A. Engbring, M. Mochizuki, M. Nomizu, and H. K. Kleinman Identification of an Active Site on the Laminin {alpha}5 Chain Globular Domain That Binds to CD44 and Inhibits Malignancy Cancer Res., July 15, 2004; 64(14): 4810 - 4816. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Dixelius, L. Jakobsson, E. Genersch, S. Bohman, P. Ekblom, and L. Claesson-Welsh Laminin-1 Promotes Angiogenesis in Synergy with Fibroblast Growth Factor by Distinct Regulation of the Gene and Protein Expression Profile in Endothelial Cells J. Biol. Chem., May 28, 2004; 279(22): 23766 - 23772. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Cancer Research | Clinical Cancer Research |
| Cancer Epidemiology Biomarkers & Prevention | Molecular Cancer Therapeutics |
| Molecular Cancer Research | Cancer Prevention Research |
| Cancer Prevention Journals Portal | Cancer Reviews Online |
| Annual Meeting Education Book | Meeting Abstracts Online |