Background: Renal cell carcinoma (RCC) is the most common malignancy of human adult kidney and accounts for 2 to 3% of all cancers.As RCC respond poorly to anthracyclines, Vinca alkaloids, and other anticancer agents as a result of the intrinsic multidrug resistance (MDR) phenotype, most of the RCC patients have a poor prognosis. Overexpression of P-glycoprotein (P-gp) encoded by the multidrug resistance 1 (mdr1) gene is thought to be the major cause of the contribution to the intrinsic multidr...