Effect of hepatitis B virus X in inhibiting the apoptosis of trophoblastic cells and its potential mechanism / 西安交通大学学报(医学版)

【Objective】 To investigate the relationship between hepatitis B virus X （HBx） protein and EGFR promoter， and the role of HBx protein in activating EGFR/PI3K/p-Akt signaling pathway and inhibiting apoptosis. 【Methods】 EGFR promoter plasmids were constructed and the relationship between HBx and EGFR promoters was characterized using a luciferase reporter assay. EGFR-overexpressing trophoblast cells were constructed， and EGFR expression in the overexpressing cells was knocked down using EGFR shRNA. The expression and localization of EGFR/PI3K/p-Akt were detected by Western blotting and confocal laser microscopy. Cell apoptosis was analyzed using flow cytometry. HBV plasmids carrying either full-length HBx or HBx with a deletion mutation （ΔHBx） and HBx plasmids were transfected into two types of trophoblast cells； HBx and PI3K/p-Akt protein expressions were detected by Western blotting. Cell apoptosis was analyzed using flow cytometry. 【Results】 Co-transfection of HBx and EGFR promoter plasmids in JEG-3 and HTR-8/Svneo cells significantly elevated the expression of EGFR promoter driven luciferase compared with the control group （P<0.01）. In EGFR-overexpressing cells， the expression of PI3K/p-Akt was significantly increased （P<0.01）， whereas the apoptosis rate was significantly decreased for JEG-3 cells and HTR-8/Svneo cells （both P<0.01）. These results were reversed in the EGFR-knock down group. When the intracellular HBx protein was expressed in JEG-3 and HTR-8 cells， PI3K/p-Akt protein expression was significantly increased （both P<0.05）， and the proportion of apoptosis was significantly decreased （both P<0.05）. 【Conclusion】 In placental trophoblast cells， HBx protein activates the expression of EGFR by acting on the EGFR promoter， and inhibits the apoptosis of trophoblast cells via the downstream EGFR/PI3K/p-Akt signaling pathway.

Nuclear Expression of Hepatitis B Virus X Protein Is Associated with Recurrence of Early-Stage Hepatocellular Carcinomas: Role of Viral Protein in Tumor Recurrence

BACKGROUND: Hepatitis B virus (HBV) plays well-known roles in tumorigenesis of hepatocellular carcinoma (HCC) in infected patients. However, HBV-associated protein status in tumor tissues and the relevance to tumor behavior has not been reported. Our study aimed to examine the expression of HBV-associated proteins in HCC and adjacent nontumorous tissue and their clinicopathologic implication in HCC patients. METHODS: HBV surface antigen (HBsAg), HBV core antigen (HBcAg), and HBV X protein (HBx) were assessed in 328 HBV-associated HCCs and in 155 matched nontumorous tissues by immunohistochemistry staining. RESULTS: The positive rates of HBsAg and cytoplasmic HBx staining in tumor tissue were lower than those in nontumorous tissue (7.3% vs. 57.4%, p < .001; 43.4% vs. 81.3%, p < .001). Conversely, nuclear HBx was detected more frequently in tumors than in nontumorous tissue (52.1% vs. 30.3%, p < .001). HCCs expressing HBsAg, HBcAg, or cytoplasmic HBx had smaller size; lower Edmondson-Steiner (ES) nuclear grade, pT stage, and serum alpha-fetoprotein, and less angioinvasion than HCCs not expressing HBV-associated proteins. Exceptionally, nuclear HBx-positive HCCs showed higher ES nuclear grade and more frequent large-vessel invasion than did nuclear HBx-negative HCCs. In survival analysis, only nuclear HBx-positive HCCs had shorter disease-free survival than nuclear HBx-negative HCCs in pT1 and ES nuclear grade 1-2 HCC subgroup (median, 126 months vs. 35 months; p = .015). CONCLUSIONS: Our data confirmed that expression of normal HBV-associated proteins generally decreases in tumor cells in comparison to nontumorous hepatocytes, with the exception of nuclear HBx, which suggests that nuclear HBx plays a role in recurrence of well-differentiated and early-stage HCCs.

Molecular Pathogenesis of Hepatitis-B-virus-associated Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most frequent and malignant diseases worldwide. Epidemiological studies have clearly demonstrated that chronic hepatitis B virus (HBV) infection is a major etiological factor in the development of HCC. The pathogenesis of HBV-associated HCC has been studied extensively, and the molecular changes associated with malignant transformation have been identified. The predominant carcinogenic mechanisms of HBV-associated HCC are chronic inflammation and the effects of cytokines in the development of fibrosis and liver cell proliferation. An important role is also played by the integration of HBV DNA into host cellular DNA, which disrupts or promotes the expression of cellular genes that are important in cell growth and differentiation. Especially, HBx protein is a transactivating protein that promotes cell growth, survival, and the development of HCC. Continued investigation of the mechanisms underlying hepatocarcinogenesis will refine our current understanding of the molecular and cellular basis for neoplastic transformation in the liver. Prevention of HBV infections and effective treatments for chronic hepatitis B are still needed for the global control of HBV-associated HCC. This review summarizes the current knowledge on the mechanisms involved in HBV-associated hepatocarcinogenesis.

Molecular Mechanisms of Hepatitis B Virus-associated Hepatocellular Carcinoma / 대한간학회지

Hepatocellular carcinoma (HCC) is one of the most common malignant diseases in the world. The hepatitis B virus (HBV) replicates non-cytopathically in hepatocytes, and most of the liver injury associated with this infection reflects the immune response. Epidemiological studies have clearly demonstrated that a chronic HBV infection is a major etiological factor in the development of HCC. The pathogenesis of HBV-associated HCC has been studied extensively, and the molecular changes during the malignant transformation have been identified. The main carcinogenic mechanism of HBV-associated HCC is related to the long term-inflammatory changes caused by a chronic hepatitis B infection, which might involve the integration of the HBV. Integration of the HBV DNA into the host genome occurs at the early steps of clonal tumorous expansion. The hepatitis B x protein (HBx) is a multifunctional regulatory protein that communicates directly or indirectly with a variety of host targets, and mediates many opposing cellular functions, including its function in cell cycle regulation, transcriptional regulation, signaling, encoding of the cytoskeleton and cell adhesion molecules, as well as oncogenes and tumor suppressor genes. Continued study of the mechanisms of hepatocarcinogenesis will refine our current understanding of the molecular and cellular basis for neoplastic transformations in the liver. This review summarizes the current knowledge of the mechanisms involved in HBV-associated hepatocarcinogenesis.