ROLE OF THE SIKVAV SITE OF LAMININ IN PROMOTION OF ANGIOGENESIS AND TUMOR-GROWTH - AN INVIVO MATRIGEL MODEL

Background: Angiogenesis (vascularization) has a critical role in tumor growth and metastasis, and peptides containing the SIKVAV amino acid sequence (Ser-Ile-Lys-Val-Ala-Val) have been shown to stimulate many angiogenic activities in vitro. The use of model systems to identify agents that stimulate or inhibit angiogenesis may lead to the development of new antitumor strategies. Purpose: Our purpose was to use an in vivo murine model system to study the angiogenic activity of a synthetic peptide derived from the laminin A protein chain and containing the SIKVAV amino acid sequence. We also examined the ability of the peptide to enhance tumor growth in vivo. Methods: The SIKVAV-containing peptide was mixed with Matrigel, a reconstituted basement membrane extract used to assay stimulation of angiogenesis. The mixture was subcutaneously injected into C57BL/6 mice. At various times after injection, the Matrigel plug was excised, and angiogenic activity was assessed by histologic examination and immunohistochemical staining with an antibody to the von Willebrand factor (vWF), an endothelium-specific antigen. In other experiments, the mixture of peptide and Matrigel was co-injected with B16F10 murine melanoma cells into C57BL/6 mice, and the resultant tumors were assessed for size and vascularization. Results: When co-injected with Matrigel at doses as low as 10 mug, the SIKVAV-containing peptide stimulated angiogenesis fourfold greater than that seen in controls, and maximum angiogenic activity was observed 2 weeks after injection. This peptide was angiogenic in a dose-dependent manner up to a 100-mug dose. When co-injected with Matrigel and B16F10 melanoma cells, the peptide enhanced tumor growth by approximately 2.5-fold, and tumor vascularization was significantly increased (P = .027) over that observed after injection with melanoma cells and Matrigel alone. Conclusions: These data demonstrate that the laminin-derived SIKVAV-containing peptide is angiogenic in a new in vivo model system and can enhance tumor vascularization and growth.