Integrins are ?/? heterodimeric cell surface receptors that play a pivotal role in cell adhesion and migration, as well as in growth and survival. The integrin family contains at least 18 ? and 8 ? subunits that form 24 known integrins with distinct tissue distribution and overlapping 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 the extracellular environment (inside-out signaling) .
Integrin ?5/?1 is involved in multiple biological processes including embryonic development, angiogenesis and tumor metastasis. By interaction with its fibronectin ligand, ?5/?1 transduces signals that regulate cell adhesion, migration, matrix assembly and cytoskeletal organization.