KDR and renal cell carcinoma: Sorafenib, a multi-kinase inhibitor of rapidly accelerated fibrosarcoma (RAF) kinase, vascular endothelial growth factor receptor -2/-3 (VEGFR-2/-3), platelet-derived growth factor receptor β (PDGFR-β), Flt3 and C-kit receptor, has been recommended in the therapy of solid cancers, such as renal cell carcinoma and HCC [21].