<p>Sunitinib inhibits cellular signaling by targeting multiple receptor tyrosine kinases (RTKs).<br />
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These include all receptors for platelet-derived growth factor (PDGF-Rs) and vascular endothelial growth factor receptors (VEGFRs), which play a role in both tumor angiogenesis and tumor cell proliferation. The simultaneous inhibition of these targets therefore reduces tumor vascularization and triggers cancer cell apoptosis and thus results in tumor shrinkage.<br />
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Sunitinib also inhibits CD117 (c-KIT), the receptor tyrosine kinase that (when improperly activated by mutation) drives the majority of gastrointestinal stromal cell tumors. It has been recommended as a second-line therapy for patients whose tumors develop mutations in c-KIT that make them resistant to imatinib, or who the cannot tolerate the drug.<br />
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In addition, sunitinib binds other receptors. These include: RET, CD114, CD135. The fact that sunitinib targets many different receptors, leads to many of its side effects such as the classic hand-foot syndrome, stomatitis, and other dermatologic toxicities.</p>