TGFB1 and hepatocellular carcinoma: These findings, together with the results of this study, therefore suggest that the pre-S2 mutant-enhanced TGF-β1 secretion from HCC tumor cells may be probably one of the possible explanations for the increased infiltration and activity of Tregs as well as decreased activity of CTLs in HCC tissues of the pre-S2 mutant-positive patients.