FLT3 and renal cell carcinoma: Sunitinib, a receptor tyrosine kinase (RTK) inhibitor, is the first-line treatment for renal cell carcinoma (RCC) patients, which has potent anti-angiogenic and anti-tumor activities by inhibition of VEGF receptor, PDGF receptor, FMS-like tyrosine kinase 3 (FLT3), and stem cell growth factor receptor.