integrin αvβ3 (alpha-v beta-3), a heterodimeric transmembrane receptor that mediates cell adhesion and signaling. Integrin αvβ3 is expressed at low levels on normal, quiescent endothelial cells and some osteoclasts but becomes highly upregulated on activated endothelial cells within growing tumor vasculature and on certain aggressive tumor cells (e.g., melanoma, glioblastoma). It recognizes ligands in the extracellular matrix containing an Arg-Gly-Asp (RGD) amino acid sequence, such as vitronectin, fibronectin, and osteopontin. Upon ligand binding, αvβ3 activates intracellular signaling cascades (e.g., via FAK and Src kinases) that promote endothelial cell migration, proliferation, and survival during angiogenesis, as well as tumor cell invasion and metastasis.