The integrin family contains at least 18 alpha and 8 beta subunits that form 24 known integrins with distinct tissue distribution and overlaping ligand specificities. Integrins not only transmit signals to cells in response to the extracellular environment (outside-in signaling), but also sense intracellular cues to alter their interaction with extracellular environment (inside-out signaling).Several alphaV subfamily members, including alphaVbeta3, alphaVbeta5, alphaVbeta1, are highly expressed in active endothelial cells and cancer cells where they play a critical role in angiogenesis and tumor metastasis.