Sorafenib is a kinase inhibitor that decreases tumor cell proliferation in vitro. Sorafenib was shown to inhibit multiple intracellular (CRAF, BRAF and mutant BRAF) and cell surface kinases (KIT, FLT-3, RET, VEGFR-1, VEGFR-2, VEGFR-3, and PDGFR-?). Several of these kinases are thought to be involved in tumor cell signaling,?angiogenesis, and?apoptosis. Sorafenib inhibited tumor growth and angiogenesis of human?hepatocellular carcinoma?and?renal cell carcinoma, and several other human tumor xenografts in?immunocompromised?mice.