Impact of Hepatitis B Virus (HBV) X Gene Mutations on Hepatocellular Carcinoma Development in Chronic HBV Infection

Abstract

The hepatitis B virus (HBV) PreS mutations C1653T, T1753V, and A1762T/G1764A were reported as a strong risk factor of hepatocellular carcinoma (HCC) in a meta-analysis. HBV core promoter overlaps partially with HBx coding sequence, so the nucleotide 1762 and 1764 mutations induce HBV X protein (HBx) 130 and 131 substitutions. We sought to elucidate the impact of HBx mutations on HCC development. Chronically HBV-infected patients were enrolled in this study: 42 chronic hepatitis B (CHB) patients, 23 liver cirrhosis (LC) patients, and 31 HCC patients. Direct sequencing showed HBx131, HBx130, HBx5, HBx94, and HBx38 amino acid mutations were common in HCC patients. Of various mutations, HBx130؉HBx131 (double) mutations and HBx5؉HBx130؉HBx131 (triple) mutations were significantly high in HCC patients. Double and triple mutations increased the risk for HCC by 3.75-fold (95% confidence interval [CI] ‫؍‬ 1.101 to 12.768, P ‫؍‬ 0.033) and 5.34-fold (95% CI ‫؍‬ 1.65 to 17.309, P ‫؍‬ 0.005), respectively, when HCC patients were compared to CHB patients. Functionally, there were significantly higher levels of NF-B activity in cells with the HBx5 mutant and with the double mutants than that of wild-type cells and the triple-mutant cells. The triple mutation did not increase NF-B activity. Other regulatory pathways seem to exist for NF-B activation. In conclusion, a specific HBx mutation may contribute to HCC development by activating NF-B activity. The HBx5 mutation in genotype C2 HBV appears to be a risk factor for the development of HCC and may be used to predict the clinical outcomes of patients with chronic HBV infection.Hepatitis B virus (HBV) infection is a global health issue, with two billion people infected worldwide and 350 million suffering from chronic HBV infection (18). Chronic HBV infection is known as the most common underlying etiology of hepatocellular carcinoma (HCC) (2) and can further progress to liver cirrhosis (LC) and HCC. However, the pathogenesis of these HBV-related diseases has not been fully clarified. The disease progression may depend on complex and multistep mechanisms.In an HBV management consensus report, the National Institutes of Health (NIH) suggested risk factors associated with the increased risk of HCC and cirrhosis in chronic HBVinfected patients (20). That report described the HCC risk based on demographic factors, environmental factors, and viral factors and classified them using the scoring system of evidence-based studies. The association between HBV mutations and HCC has not been fully investigated. Recently, the HBV PreS mutations C1653T, T1753V, and A1762T/G1764A were reported as strong risk factors for HCC in a meta-analysis (19). Mutations of HBV have been considered as an escape mechanism from the host immune system and may affect the oncogenic potential of chronic HBV diseases.HBV X is the smallest of four kinds of HBV functional genes, but it expresses a 154-amino-acid multifunctional protein (HBx), with an N-terminal negative regulatory/antiapoptotic domain and a C-termin...

A novel mutant 10Ala/Arg together with mutant 144Ser/Arg of hepatitis B virus X protein involved in hepatitis B virus-related hepatocarcinogenesis in HepG2 cell lines

“…We identified high frequency of K130M mutation and A1762T/G1764A double-mutation in 47 para-tumor and central-tumor samples, similar to previous reports [20,32,33]. But no statistically significant differences in these mutation sites were observed between central- and para-tumor tissues, although there were differences in entropy between both sequence datasets.…”

“…HBx modulates transcription, responses to genotoxic stress, protein degradation, and other signaling pathways [15], affecting viral replication and proliferation, cell cycle checkpoints [16], apoptosis [17], and carcinogenesis [18]. HBx mutations, including double-substitution K130M-V131I, found preferentially in HCC patients [19], may be a risk factor for HCC development [20]. Furthermore, HBx gene disruptions were more frequent in tumor than in non-tumor liver [21,22].…”

Clinical utility of complex mutations in the core promoter and proximal precore regions of the hepatitis B virus genome

“…The core promoter overlaps the distal part of the X gene, and the proximal precore includes the epsilon signal [38][39][40] . These two genetically distinct regions are the most complex portion of the HBV genome, which includes various functional gene clusters, such as enhancer Ⅱ, the basal core promoter, the X-termination signal, two pregenomic RNA start points, the poly A signal, epsilon, and other important sequences [38][39][40] .…”

“…These two genetically distinct regions are the most complex portion of the HBV genome, which includes various functional gene clusters, such as enhancer Ⅱ, the basal core promoter, the X-termination signal, two pregenomic RNA start points, the poly A signal, epsilon, and other important sequences [38][39][40] . These regions differentially regulate the synthesis of pregenomic and pre-C mRNAs of HBV and the production of HBeAg and hepatitis B core antigen (HBcAg), and cooperatively regulate viral replication [39][40][41][42] . Any single mutation can induce some form of inherent change that affects viral loads and the levels of HBeAg in serum and HBcAg and X protein in hepatocytes.…”

“…Any single mutation can induce some form of inherent change that affects viral loads and the levels of HBeAg in serum and HBcAg and X protein in hepatocytes. These effects can subsequently modulate the immune response to viral antigens and enhance the carcinogenic effects of altered X proteins [40] . In Far East Asia, HBV genotypes B and C are predominant, and five mutations are prominent in the core promoter and proximal precore regions: G1613A, C1653T, T1753V, A1846T, and G1899A [43][44][45][46][47] .…”