Identification of Transforming Hepatitis B Virus S Gene Nonsense Mutations Derived from Freely Replicative Viruses in Hepatocellular Carcinoma

Abstract

Background & AimsThe correlation between chronic hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC) has been well-established. But the roles of viral factor remain uncertain. Only HBV X gene and nonsense mutations of S gene (C-terminal truncation of HBV surface protein) have been demonstrated to have transforming activity. Whether they play a significant role in hepatocarcinogenesis is still uncertain.MethodsTwenty-five HBV-related HCC patients were positive for hepatitis B core antigen (HBcAg) in the cancerous parts of their HCC liver tissues by immunohistochemistry studies, and had available tissue for whole HBV genome sequence analysis. The results were compared with 25 gender and age-matched HBcAg negative HCCs. Plasmids encoding HBV S gene nonsense mutations identified from HBcAg (+) HCC tissue were constructed to investigate their cell proliferation, transformation activity and the oncogenic potentials by xenograft study and in vivo migration assay.ResultsHBcAg (+) HCC patients were significantly associated with cirrhosis and small tumor size (≦2 cm) when compared with HBcAg (−) HCC patients. Southern blot analyses revealed freely replicative forms of HBV in the cancerous parts of HBcAg(+) HCC. Three nonsense mutations of S gene (sL95*, sW182*, and sL216*) were identified in the HBcAg(+) HCC tumor tissues. sW182* and sL216* were recurrently found in the 25 HBcAg (−) HCC tumor tissue, too. Functional studies of the above 3 non-sense mutations all demonstrated higher cell proliferation activities and transformation abilities than wild type S, especially sW182*. Tumorigenicity analysis by xenograft experiments and in vitro migration assay showed potent oncogenic activity of sW182* mutant.ConclusionsThis study has demonstrated potent oncogenic activity of nonsense mutations of HBV S gene, suggesting they may play an important role in hepatocarcinogenesis.

Naturally Occurring Surface Antigen Variants of Hepatitis B Virus in Tunisian Patients

“…However, these findings may not be conclusive in this study since the number of cirrhosis patients was small. Some S mutation patterns have been found in association with cirrhosis [60,61,62]. In the present data, 3 mutations were detected in association with cirrhosis: one is the Y134N mutation, inside the MHR, the others are L49R and L213I mutations, outside the MHR.…”

Selection of the highly replicative and partially multidrug resistant rtS78T HBV polymerase mutation during TDF-ETV combination therapy

“…In this regard, the emergence of rtS78T/sC69* mutation has been occasionally reported in the literature [21,22,25]. The presence of rtS78T in addition to rtT184S, rtV173L, rtL180M, and rtM204V, was associated with a two-fold reduction in ETV susceptibility; however, in line with our results, the ETV resistance level for this mutation alone did not exceed 1.8-fold of the level of wild type HBV [26–29].…”

Hepatocarcinogenesis in transgenic mice carrying hepatitis B virus pre-S/S gene with the sW172* mutation

“…19, 20 Recent studies using HBcAg/HBsAg-postive HCC tissues uncovered another frequent S gene truncation mutation, sW182*. 34 It has been reported to be highly prevalent in Korean HCC patients and it has been found in HBV and HIV coinfected patients. 35, 36 Tumorigenicity assessment in nude mice showed an even higher oncongenicity.…”