FAS1 domain protein inhibits VEGF₁₆₅-induced angiogenesis by targeting the interaction between VEGFR-2 and αvβ3 integrin

It is known that VEGF receptors (VEGFR) and integrins interact with each other to regulate angiogenesis. We reported previously that the fasciclin 1 (FAS1) domain-containing protein, TGFBIp/βig-h3 (TGF-β-induced protein) is an angiogenesis regulator that inhibits both endothelial cell migration and growth via αvβ3 integrin. In an attempt to target the interaction between VEGFR-2 and αvβ3 integrin, we determined whether the FAS1 domain region of TGFBIp/βig-h3 (FAS1 domain protein) can block the interaction between the two receptors, leading to the suppression of angiogenesis. In this study, we showed that FAS1 domain protein inhibits VEGF₁₆₅-induced endothelial cell proliferation and migration via αvβ3 integrin, resulting in the inhibition of VEGF ₁₆₅-induced angiogenesis. We also defined a molecular mechanism by which FAS1 domain protein blocks the association between αvβ3 integrin and VEGFR-2, showing that it binds to αvβ3 integrin but not to VEGFR-2. Blocking the association of these major angiogenic receptors with FAS1 domain protein inhibits signaling pathways downstream of VEGFR-2. Collectively, our results indicate that FAS1 domain protein, in addition to its inhibitory effect on αvβ3 integrin-mediated angiogenesis, also inhibits VEGF₁₆₅-induced angiogenesis. Thus, FAS1 domain protein can be further developed into a potent anticancer drug that targets two principal angiogenic pathways.