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 (alpha)V subfamily members, including (alpha)V(beta)3, (alpha)V(beta)5, (alpha)V(beta)1, are highly expressed in active endothelial cells and cancer cells where they play a critical role in angiogenesis and tumor metastasis.