TGFB1 and hepatocellular carcinoma: In conclusion, our findings provide evidence for the significant association of TGFB1 gene C-509T polymorphism with hepatocellular carcinoma in population-based studies and circulating TGF-β1 changes, and importantly enhanced circulating TGF-β1 was suggested to be causally associated with an increased risk of hepatocellular carcinoma by choosing TGFB1 gene C-509T polymorphism as an instrument, the association warranting further validation in large, independent studies.