KDR and renal cell carcinoma: One of the initial VEGFR-TKIs utilized in advanced RCC, sorafenib inhibits intracellular Raf kinases (CRAF, BRAF, and mutant BRAF) and cell surface kinase receptors (VEGFR-1, VEGFR-2, VEGFR-3, PDGFR-beta, cKIT, FLT-3, RET, and RET/PTC) [21].