Hepatocellular carcinoma (HCC) is widely known to develop more frequently in cirrhotic patients with a high expression of Hepatitis B virus X protein (HBx), which is controlled by the enhancer 1 (Enh1) ⁄ X-promoter. To examine the effect of the mutations in the Enh1 ⁄ X-promoter region in hepatitis B virus (HBV) genomes on the development of HCC, we investigated the differences in HBV isolated from cirrhotic patients with or without HCC along with the promoter activities of certain specific mutations within the Enh1 ⁄ X-promoter. We examined 160 hepatitis B surface antigen (HBsAg)-positive cirrhotic patients (80 HCC patients, 80 non-HCC patients) by evaluating the biochemical, virological, and molecular characteristics. We evaluated the functional differences in certain specific mutations within the Enh1 ⁄ X-promoter. The isolated sequences included all of the subgenotypes C2. The sites that showed higher mutation rates in the HCC group were G1053A and G1229A, which were found to be independent risk factors through multiple logistic analysis (P < 0.05). Their promoter activities were elevated 2.38-and 4.68-fold, respectively, over that of the wild type in the HepG2 cells. Similarly, both the mRNA and protein levels of HBx in these two mutants were much higher than that in wild type-transfected HepG2 cells. Mutated nucleotides of the Enh1 ⁄ X-promoter, especially G1053A and G1229A mutations in the HBV subgenotype C2 of patients with cirrhosis, can be risk factors for hepatocarcinogenesis, and this might be due to an increase in the HBx levels through the transactivation of the Enh1 ⁄ Xpromoter. (Cancer Sci 2010; 101: 1905-1912 T he hepatitis B virus (HBV) genome is a 3.2-kb circular, partially double-stranded molecule with four overlapping open reading frames (ORF; P, S, C, and X). Hepatitis B virus (HBV) produces several viral proteins that are influenced by promoters and enhancers located upstream.(1) Hepatic injury due to HBV is mediated by immune-related mechanisms; these can induce chronic liver disease (CLD) and eventually lead to hepatocellular carcinoma (HCC).(2-4) However, the exact mechanism underlying hepatocarcinogenesis in chronic HBV infection remains elusive.The development of HCC by HBV is enhanced by several risk factors such as cirrhosis, carcinogen exposure, alcohol abuse, genetic factors, a higher viral load, viral genotype, male gender, and advanced age.(5-8) Among them, cirrhosis is the strongest risk factor.(9-11) Therefore, the ability of HBV to induce inflammation that affects the host immune response might be a primary contributing factor for hepatocarcinogenesis. (5,7,12) Additional explanations of hepatocarcinogenesis include the genomic integration of HBV in the host (13,14) and the multiple regulatory activities caused by viral proteins.(15,16) Among them, Hepatitis B virus X protein (HBx) has been most commonly implicated in hepatocarcinogenesis, as HCC does not occur in avian hosts that lack X-ORF.(17) Hepatocellular carcinoma (HCC) development occurs more frequently in humans with...
