Integrins are heterodimeric transmembrane glycoproteins consisting of an α and a β subunit.
In total, 24 different subtypes of integrins that are constituted from 18α and 8β subunits have been discovered to date. Almost half of them bind to various ECM proteins such as fibronectin, vitronectin, and collagen via RGD motif, and are vital in the adhesion, growth, signaling, proliferation, migration, survival, migration and invasion of most cells. Synthetic RGD peptides or peptidomimetics may affect these events in tumour cells thereby directly induce apoptosis. They also can be used for tumor targeted drug-delivery.