Because most of the TGF-β in the serum is contained in platelet α-granules30 and recombinant TGF-β1 could reduce expression of KLF6 in HCC cells (Supplemental Fig. 5), we hypothesized that platelet-derived TGF-β is involved in tumor growth and affects KLF6 expression. The gene discussed is TGFB1; the disease is hepatocellular carcinoma.