TGFBR1 and nonpapillary renal cell carcinoma: Treatment of different RCC cell lines with recombinant TGF-β1 showed a down-regulation of TGFBR2 while TGFBR1 was upregulated (Figure 2A) with exception of the ccRCC cell line MZ2733RC, which showed a down-regulation for both receptor subunits.