In order to explore further the correlation between sunitinib response and protein expression of the validated genes, we carried out immunohistochemical staining of VEGFR1 (FLT1), SAV1 and BLIMP1 (PRDM1) on 170 ccRCC cases uniformly treated with sunitinib. Here, FLT1 is linked to nonpapillary renal cell carcinoma.