Genes involved in TGF-β signaling and the encoded proteins dysregulated in renal tumors from BHD patients. (A) Quantitative RT-PCR of TGFB2, INHBA, SMAD3, THBS1, GREM1 and FLCN expression levels in human BHD tumors (T, n = 12) and normal kidneys (N, n = 8). Gene expressions were normalized against cyclophilin gene expression and relative expressions were calculated against gene expression in UOK257 cells. Median values of expression levels were indicated with short lines. Points, mean expression of each sample. P value, Mann-Whittney U-test. (B) Reduced expression of TGF-β2 in the BHD tumors (left panel) and the UOK257 xenograft tumors (right panel) compared to normal renal tubules as shown by immunohistochemical staining. Five BHD tumors were examined and a representative immunostained image is shown. (C) Positive correlation of pSMAD3 and SMAD3 with FLCN expression in human BHD kidney tumors and normal kidney tissue. pSMAD3, SMAD2, SMAD3 and FLCN protein levels were measured by western blot analysis in normal kidney tissue (n = 5) and BHD tumors (n = 11).