Hepatitis B and C viruses and hepatocellular carcinoma.

Although it is now accepted that both HBV and HCV are carcinogenic in humans, uncertainty still exists as to the exact pathogenetic mechanisms involved. Direct and indirect carcinogenic mechanisms are probable, and there is persuasive evidence that both are involved in HBV-induced HCC. The direct effect of HBV appears to be mediated through insertional mutagenesis, with the transactivating properties of products of the X gene and perhaps a truncated preS/S gene being a likely component. Direct carcinogenicity is less certain in HCV/induced HCC, although indirect evidence does suggest such an effect. The two viruses almost certainly interact in HCC, and each probably interacts with alcohol in inducing chronic hepatic parenchymal disease that in turn is complicated by malignant transformation.