Since the suppression of in vitro DC generation caused by the CM of RIG-I-deficient human HCC cells was ameliorated with a neutralizing anti-TGF-β1 antibody and since tumors derived from RIG-I-deficient human HCC cells contained a large amount of TGF-β1, our results also suggest that TGF-β1 is involved in suppression of DC generation and in the phenotypic change of TIDCs. This evidence concerns the gene RIGI and hepatocellular carcinoma.