A novel α_vβ₃-blocking disintegrin containing the RGD motive, DisBa-01, inhibits bFGF-induced angiogenesis and melanoma metastasis

The integrin α_vβ₃ is involved in multiple aspects of malignant cancer, including tumor angiogenesis and metastasis, which makes the receptor a key target for the development of anti-cancer therapies. We report here on the production, the characterization and the in vivo anti-angiogenic and anti-metastatic properties of a novel α _vβ₃-binding disintegrin, DisBa-01, isolated from a cDNA library made with RNAs from the venom gland of Bothrops alternatus. The 11,637 Da-recombinant monomeric form of DisBa-01 displayed an RGD motif and interacted with purified α_vβ₃ integrin in surface plasmon resonance studies, in a dose-dependent and cation sensitive manner. A three-dimensional molecular model of DisBa-01 in complex with α_vβ₃ predicted a large surface of contacts with the β₃ subunit. DisBa-01 inhibited the adhesion of α_vβ₃-expressing human microvascular endothelial cell line-1 (HMEC-1) and murine melanoma cell line B16F10 to vitronectin (IC₅₀ = 555 nM and 225 nM, respectively), and transiently inhibited their proliferation without direct cell toxicity, but did not affect the binding nor the proliferation of a human breast cancer-derived cell line (MDA-MB-231) not expressing α_vβ₃. In vivo, DisBa-01 dose-dependently decreased bFGF-induced angiogenesis in a matrigel plug assay in athymic nude mice (IC₅₀ = 83 nM). When injected intravenously to C57BL/6 mice together with B16F10 melanoma cells, DisBa-01 time- and dose-dependently inhibited lung metastasis monitored by bioluminescent imaging. We conclude that DisBa-01 is a potent new inhibitor of α_vβ ₃-dependent adherence mechanisms involved in neo-vascularization and tumor metastasis processes.