Distinct antitumor properties of a type IV collagen domain derived from basement membrane

Vascular basement membrane is an important structural component of blood vessels. During angiogenesis this membrane undergoes many alterations and these changes are speculated to influence the formation of new capillaries. Type IV collagen is a major component of vascular basement membrane, and recently we identified a fragment of type IV collagen alpha 2 chain with specific anti-angiogenic properties (Kamphaus, G. D., Colorado, P. C., Panka, D. J., Hopfer, H., Ramchandran, R., Tome, A., Maeshima, Y., Mier, J. W., Sukhatme, V. P., and Karlluri, R. (2000) J. Biol. Chem. 275, 1209-1215), In the present study we characterize two different antitumor activities associated with the noncollagenous 1 (NC1) domain of the alpha 3 chain of type IV collagen. This domain was previously discovered to possess a C-terminal peptide sequence (amino acids 185-203) that inhibits melanoma cell proliferation (Han, J., Ohno, N., Pasco, S., Monboisse, J. C., Borel, J. P., and Kefalides, N. A. (1997) J. Biol. Chem. 272, 20395-20401). In the present study, we identify the anti-angiogenic capacity of this domain using several in vitro and in vivo assays. The alpha 3(IV)NC1 inhibited in vivo neovascularization in matrigel plug assays and suppressed tumor growth of human renal cell carcinoma (786-O) and prostate carcinoma (PC-3) in mouse xenograft models associated with in vivo endothelial cell-specific apoptosis. The anti-angiogenic activity was localized to amino acids 54-132 using deletion mutagenesis. This anti-angiogenic region is separate from the 185-203 amino acid region responsible for the antitumor cell activity. Additionally, our experiments indicate that the antitumor cell activity is not realized until the peptide region is exposed by truncation of the alpha 3(IV)NC1 domain, a requirement not essential for the anti-angiogenic activity of this domain. Collectively, these results effectively highlight the distinct and unique antitumor properties of the alpha 3(IV)NC1 domain and the potential use of this molecule for inhibition of tumor growth.