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.

Dysregulation of the enzymes involved in the pentose phosphate pathway (PPP) is known to promote tumorigenesis. Our recent study demonstrated that ribose-5-phosphate isomerase (RPIA), a key regulator of the PPP, regulates hepatoma cell proliferation and colony formation. Our studies in zebrafish reveal that RPIA-mediated hepatocarcinogenesis requires extracellular signal-regulated kinase (ERK) and β-catenin signaling. To further investigate RPIA-mediated hepatocarcinogenesis, two independent lines of transgenic zebrafish expressing human RPIA in the liver were generated. These studies reveal that RPIA overexpression triggers lipogenic factor/enzyme expression, steatosis, fibrosis and proliferation of the liver. In addition, the severity of fibrosis and the extent of proliferation are positively correlated with RPIA expression levels. Furthermore, RPIA-mediated induction of hepatocellular carcinoma (HCC) requires the ERK and β-catenin signaling pathway but is not dependent upon transaldolase levels. Our study presents a mechanism for RPIA-mediated hepatocarcinogenesis and suggests that RPIA represents a valuable therapeutic target for the treatment of HCC.

α‐1,2 mannosidases, key enzymes in N‐glycosylation, are required for the formation of mature glycoproteins in eukaryotes. Aberrant regulation of α‐1,2 mannosidases can result in cancer, although the underlying mechanisms are unclear. Here, we report the distinct roles of α‐1,2 mannosidase subtypes (MAN1A, MAN1B, ERMAN1, MAN1C) in the formation of hepatocellular carcinoma (HCC). Clinicopathological analyses revealed that the clinical stage, tumor size, α‐fetoprotein level, and invasion status were positively correlated with the expression levels of MAN1A1, MAN1B1, and MAN1A2. In contrast, the expression of MAN1C1 was decreased as early as stage I of HCC. Survival analyses showed that high MAN1A1, MAN1A2, and MAN1B1 expression levels combined with low MAN1C1 expression levels were significantly correlated with shorter overall survival rates. Functionally, the overexpression of MAN1A1 promoted proliferation, migration, and transformation as well as in vivo migration in zebrafish. Conversely, overexpression of MAN1C1 reduced the migration ability both in vitro and in vivo, decreased the colony formation ability, and shortened the S phase of the cell cycle. Furthermore, the expression of genes involved in cell cycle/proliferation and migration was increased in MAN1A1‐overexpressing cells but decreased in MAN1C1‐overexpressing cells. MAN1A1 activated the expression of key regulators of the unfolded protein response (UPR), while treatment with endoplasmic reticulum stress inhibitors blocked the expression of MAN1A1‐activated genes. Using the MAN1A1 liver‐specific overexpression zebrafish model, we observed steatosis and inflammation at earlier stages and HCC formation at a later stage accompanied by the increased expression of the UPR modulator binding immunoglobulin protein (BiP). These data suggest that the up‐regulation of MAN1A1 activates the UPR and might initiate metastasis. Conclusion: MAN1A1 represents a novel oncogene while MAN1C1 plays a role in tumor suppression in hepatocarcinogenesis. (Hepatology Communications 2017;1:230‐247)