VEGF–integrin interplay controls tumor growth and vascularization

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Abstract
Cross-talk between the major angiogenic growth factor, VEGF, and integrin cell adhesion receptors has emerged recently as a critical factor in the regulation of angiogenesis and tumor development. However, the molecular mechanisms and consequences of this intercommunication remain unclear. Here, we define a mechanism whereby integrin αvβ3, through activation, clustering, and signaling by means of p66 Shc (Src homology 2 domain containing), regulates the production of VEGF in tumor cells expressing this integrin. Tumors with “activatable” but not “inactive” β3 integrin secrete high levels of VEGF, which in turn promotes extensive neovascularization and augments tumor growth in vivo. This stimulation of VEGF expression depends upon the ability of αvβ3 integrin to cluster and promote phosphorylation of p66 Shc. These observations identify a link between β3 integrins and VEGF in tumor growth and angiogenesis and, therefore, may influence anti-integrin as well as anti-VEGF therapeutic strategies.