It has been shown that angiogenesis is highly dependent upon extracellular and inflammatory signals such as cytokines, proteases, and growth factors. Integrins, a type of transmembrane receptor protein, have been shown to be important for angiogenesis. When they are inhibited, specifically integrin α5β1, angiogenesis does not occur.[21] Targeting integrin αvβ5 was shown to have a negative effect on vascular endothelial growth factor (VEGF)-dependent angiogenesis.