Hepatitis B virus X protein induces hepatic stem cell-like features in hepatocellular carcinoma by activating KDM5B

AIM To determine the role of hepatitis B virus X protein(HBx), HBx in regulating hepatic progenitor cell(HPC)-like features in hepatocellular carcinoma(HCC) and the underlying molecular mechanisms.METHODS We used a retrovirus vector to introduce wild type HBx or empty vector into Hep G2 cells. We then used these cells to analyze cell proliferation, senescence, transformation, and stem-like features. Gene expression profiling was carried out on Affymetrix GeneC hip Human U133A2.0 ver.2 arrays according to the manufacturer's protocol. Unsupervised hierarchical clustering analysis and Class Comparison analysis were performed by BRB-Array Tools software Version 4.2.2. A total of 238 hepatitis B virus(HBV)-related HCC patients' array data were used for analyzing clinical features.RESULTS The histone demethylase KDM5 B was significantlyhighly expressed in HBV-related HCC cases(P 0.01). In HBV proteins, only HBx up-regulated KDM5 B by activating c-myc. Hepatic stem cell(Hp SC) markers(EpC AM, AFP, PROM1, and NANOG) were significantly highly expressed in KDM5B-high HCC cases(P 0.01). KDM5 B played an important role in maintaining HpS Clike features and was associated with a poor prognosis. Moreover, inhibition of KDM5 B suppressed spheroid formation and cell invasion in vitro.CONCLUSION HBx activates the histone demethylase KDM5 B and induces HPC-like features in HCC. Histone demethylases KDM5 B may be an important therapeutic target against HBV-related HCC cases.     

Hepatitis B virus X gene differentially modulates cell cycle progression and apoptotic protein expression in hepatocyte versus hepatoma cell lines

Summary. The hepatitis B virus (HBV) X gene, which encodes the hepatitis B virus x protein (HBx), is essential for viral infection and genome replication, virus‐associated liver disease, and development of hepatocellular carcinoma. However, the exact role(s) of HBx remain controversial. In this study, we focus on studying the role of HBx in the regulation of cell cycle and apoptosis in normal liver and hepatoma cell lines. We established the Huh7‐X and Chang‐X cell lines that constitutively express HBx. There were differences between the two cell lines in terms of cell cycle regulation and expression of p27 and transforming growth factor‐β. Expression of HBx proteins dramatically increases expression of Bcl‐2 and reduces levels of cleaved PARP protein in Chang‐X cells, and it inhibits apoptosis under unfavourable conditions, such as serum starvation, in both cell lines. Our findings provide clues about the intracellular roles of HBx and demonstrate that expression of this protein is important for multiple cellular processes, that is, cell cycle progression and apoptosis, in hepatoma cells and normal liver cell lines.     

Hepatocellular carcinoma in a hepatitis B 'x' transgenic mouse model: A sequential pathological evaluation

BACKGROUND: The introduction of transgenic technology has made it possible to study the steps of carcinogenesis and directly establish the link between viral subgenomic fragments and specific types of cancer. Research directed at hepatitis B virus (HBV)-related carcinogenesis has benefited from this technology. We present a detailed pathological evaluation of the sequential steps of hepatocarcinogenesis in a hepatitis B 'x' (HBx) transgenic mouse model. In this model, the transgene incorporates the region encoding amino acids 58-154 of the HBV X protein and the murine c-myc gene. This model demonstrated changes in the liver from birth with foci of multicentric dysplasia evolving into nodules and overt hepatocellular carcinoma between 20 and 28 weeks. METHODS AND RESULTS: The hepatocytes were mitotically active and showed increased proliferative capacity soon after birth, with exponential increase thereafter. This was accompanied by a high rate of apoptosis, which later declined as the tumors developed. Other functional and immunophenotypic characteristics included a high c-myc expression in the neoplastic lesions, no alteration in p53 expression, and no alteration in the expression of hepatic enzymes except for diffuse expression of succinic dehydrogenase. CONCLUSION: The entire process illustrates the disturbances of cell growth and death because of the collaborative influence of HBx and c-myc genes that result in the development of hepatocellular carcinoma after a prolonged latent period.     

Molecular mechanism of hepatitis B virus X protein function in hepatocarcinogenesis

Many factors are considered to contribute to hepatitis B virus(HBV)-associated hepatocellular carcinoma(HCC),including products of HBV,HBV integration and mutation,and host susceptibility. HBV X protein(HBx) can interfere with several signaling pathways associated with cell proliferation and invasion,and HBx C-terminal truncation has been suggested to impact the development of HCC. This review focuses on the pathological functions of HBx in HBV-induced hepatocarcinogenesis. As a transactivator,HBx can affect regulatory non-coding RNAs(nc RNAs),including micro RNAs and long nc RNAs. HBx is also involved in epigenetic modification and DNA repair. HBx interacts with various signal-transduction pathways,such as the p53,Wnt,and nuclear factor-κB pathways. We conclude that HBx hastens the development of hepatoma.     

Hepatitis B Virus HBx Protein Interactions with the Ubiquitin Proteasome System

The hepatitis B virus (HBV) causes acute and chronic hepatitis, and the latter is a major risk factor for the development of hepatocellular carcinoma (HCC). HBV encodes a 17-kDa regulatory protein, HBx, which is required for virus replication. Although the precise contribution(s) of HBx to virus replication is unknown, many viruses target cellular pathways to create an environment favorable for virus replication. The ubiquitin proteasome system (UPS) is a major conserved cellular pathway that controls several critical processes in the cell by regulating the levels of proteins involved in cell cycle, DNA repair, innate immunity, and other processes. We summarize here the interactions of HBx with components of the UPS, including the CUL4 adaptor DDB1, the cullin regulatory complex CSN, and the 26S proteasome. Understanding how these protein interactions benefit virus replication remains a challenge due to limited models in which to study HBV replication. However, studies from other viral systems that similarly target the UPS provide insight into possible strategies used by HBV.     

HBx triggers either cellular senescence or cell proliferation depending on cellular phenotype

Replicative senescence is a hallmark of chronic liver diseases including chronic hepatitis B virus (HBV) infection, whereas HBV‐encoded oncoproteins HBx and preS2 have been found to overcome senescence. HBx possesses a C‐terminal truncation mainly in hepatocellular carcinomas but also in noncancerous liver tissues. Here, by cell counting, BrdU incorporation, MTT proliferation assay, cell cycle analysis, SA‐βgal staining and Western blotting in primary and malignant cells, we investigated the effect of HBx C‐terminal mutants on cellular senescence. HBx C‐terminal mutants were found to trigger cellular senescence in primary MRC5 cells, and malignant liver cells Huh7, and SK‐Hep1. In contrast, these mutants promoted the proliferation of HepG2 malignant liver cells. The pro‐senescent effect of HBx relied on an increased p16^INK4a and p21^Waf1/Cip1 expression, and a decreased phosphorylation of Rb. Together, these results suggest that the two main variants of HBx present in HBV‐infected liver possess opposite effects on cellular senescence that depend on the phenotype of infected cells.     

HBx及其截短体在乙型肝炎病毒复制中的作用

HBV感染作为引起慢性乙型肝炎、乙肝后肝硬化、原发性肝癌(hepatocellular carcinoma,HCC)的起始因素,已成为世界性的健康问题.据统计,目前世界上已有超过5亿人感染HBV,每年有1百万人死于乙肝相关疾病.HBx蛋白作为HBV的一个多功能调节蛋白,已被证实在HCC的发生过程中起了重要作用.近年来,关于乙肝病毒X蛋白(HBV X protein,HBx)影响HBV的复制研究也有了一定的进展.同时,越来越多的HBx截短体在肝病发展过程中的作用也被重视.本文将对HBx及其截短体在HBV复制中的作用作一综述.     

HBx致肝细胞癌分子机制的研究进展

乙型肝炎病毒(HBV)慢性感染是我国肝细胞肝癌(HCC)发生的主要原因之一.一些体内外研究发现,乙型肝炎病毒x(HBx)可诱导肝细胞的恶性转化及癌变,成为目前研究乙肝相关性肝细胞癌发生机制的热点.近来在HBx与抑癌基因,如p53的新成员p73以及p16,p21等之间的相互作用及其对肝细胞恶性转化与癌变的影响等方面的研究也取得初步成果,但其关系错综复杂,这方面不断的深入研究将有助于进一步揭示HBx致肝细胞癌发生的分子机制,对探寻乙肝相关性肝癌新的防治策略具有重要意义.     

HBx和癌胚抗原相关细胞黏附分子1在乙型肝炎相关性肝癌中的作用及病理特征

目的 探讨HBx和癌胚抗原相关细胞黏附分子1(CEACAM1)在乙型肝炎相关性肝癌中的表达及意义.方法 采用免疫组织化学方法(SP法)检测81份乙肝相关性肝癌组织中HBx及CEACAM1的表达情况,分析HBx和CEACAM1与乙肝相关性肝癌的临床病理特征.Western印迹检测人正常肝细胞系QZG、肝癌细胞HepG2及稳定转染HBx的肝癌细胞HepG2(HepG2-X)中CEACAM1的表达.结果 81份乙肝相关性肝癌组织中HBx表达阳性率为74.07％ (60/81),CEACAM1表达阳性率为71.60％ (58/81),二者与门静脉侵袭、淋巴结转移和TNM分期存在显著相关,HBx与CEACAM1的表达呈负相关(rs=-0.310,P＜0.01);在HepG2-X中,CEACAM1蛋白表达水平与肝癌细胞HepG2及人正常肝细胞系QZG相比显著降低.结论 HBx的高表达和CEACAM1的低表达与乙肝相关性肝癌的侵袭、转移密切相关,HBx有可能通过抑制CEACAM1的表达而诱导乙肝相关性肝癌的侵袭与转移.     

乙型肝炎病毒X蛋白在原发性肝癌中的作用

乙型肝炎病毒X蛋白(HBx)是一种由HBV X基因编码的多功能蛋白,参与调节基因转录、细胞信号转导、细胞增殖转化、细胞周期和细胞凋亡。目前HBx蛋白被认为在HBV诱发原发性肝癌的过程中发挥重要作用。介绍了HBx蛋白与癌基因、抑癌基因、细胞增殖、细胞凋亡、肝癌侵袭转移和肝癌干细胞的关系,探讨了HBx蛋白在肝癌发生发展中的作用。     

Pin1 interacts with a specific serine-proline motif of hepatitis B virus X-protein to enhance hepatocarcinogenesis

BACKGROUND AND AIMS: The peptidyl prolyl isomerase Pin1 frequently is overexpressed in hepatocellular carcinoma (HCC). Hepatitis B virus (HBV) is the most common etiologic agent in HCC, and its encoded X-protein (HBx) is oncogenic and possesses a serine-proline motif that may bind Pin1. The role of Pin1 in hepatocarcinogenesis, particularly in HBV-related HCC, was investigated. METHODS: Immunohistochemical staining was performed to evaluate the prevalence of Pin1 overexpression in HCCs of different etiologies. Glutathione S-transferase pull-down and co-immunoprecipitation experiments were used to validate the physical interaction between Pin1 and HBx. Reporter assay, cell proliferation assay, and xenotransplantation experiments were used to show the functional consequence and importance of Pin1-HBx interaction in hepatocarcinogenesis. RESULTS: We showed preferential Pin1 overexpression in HBV-related tumors and confirmed the interaction between Pin1 and HBx at the specific serine-proline motif. Pin1 overexpression increased the protein stability of HBx. Furthermore, HBx-mediated transactivation was enhanced by co-expression of Pin1. HepG2 expressing Pin1 and HBx showed a synergistic increase in cellular proliferation, as compared with cells expressing Pin1 or HBx alone. Furthermore, concomitant expression of Pin1 and HBx in the nontumorigenic human hepatocyte cell line MIHA led to a synergistic increase in tumor growth. Finally, in Hep3B cells with suppressed Pin1 expression, HBx-enhanced tumor growth in nude mice was abrogated. CONCLUSIONS: Pin1 binds HBx to enhance hepatocarcinogenesis in HBV-infected hepatocytes. The discovery of an interaction between Pin1 and HBx will further our understanding of the molecular pathogenic mechanism of HBV-related HCC in human beings.     

Interaction between the Hepatitis B Virus and Cellular FLIP Variants in Viral Replication and the Innate Immune System

During viral evolution and adaptation, many viruses have utilized host cellular factors and machinery as their partners. HBx, as a multifunctional viral protein encoded by the hepatitis B virus (HBV), promotes HBV replication and greatly contributes to the development of HBV-associated hepatocellular carcinoma (HCC). HBx interacts with several host factors in order to regulate HBV replication and evolve carcinogenesis. The cellular FADD-like IL-1β-converting enzyme (FLICE)-like inhibitory protein (c-FLIP) is a major factor that functions in a variety of cellular pathways and specifically in apoptosis. It has been shown that the interaction between HBx and c-FLIP determines HBV fate. In this review, we provide a comprehensive and detailed overview of the interplay between c-FLIP and HBV in various environmental circumstances. We describe strategies adapted by HBV to establish its chronic infection. We also summarize the conventional roles of c-FLIP and highlight the functional outcome of the interaction between c-FLIP and HBV or other viruses in viral replication and the innate immune system.     

Effects of Ginkgo biloba extract on cell proliferation and cytotoxicity in human hepatocellular carcinoma cells

AIM: To study the effect of Ginkgo biloba extract (EGb 761) containing 22-27% flavonoids (ginkgo-flavone glycosides) and 5-7% terpenoids (ginkgolides and bilobalides) on cell proliferation and cytotoxicity in human hepatocellular carcinoma (HCC) cells. METHODS: Human HCC cell lines (HepG2 and Hep3B) were incubated with various concentrations (0-1 000 mg/L) of EGb 761 solution. After 24 h incubation, cell proliferation and cytotoxicity were determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay and lactate dehydrogenase (LDH) release, respectively. After 48 h incubation, the expression of proliferating cell nuclear antigen (PCNA) and p53 protein was measured by Western blotting. RESULTS: The results showed that EGb 761 (50-1 000 mg/L) significantly suppressed cell proliferation and increased LDH release (P<0.05) in HepG2 and Hep3B cells compared with the control group. The cell proliferation of HepG2 and Hep3B cells treated with EGb 761 (1 000 mg/L) was 45% and 39% of the control group (P<0.05), respectively. LDH release of HepG2 cells without and with EGb 761 (1 000 mg/L) treatment was 6.7% and 37.7%, respectively, and that of Hep3B cells without and with EGb 761 (1 000 mg/L) treatment was 7.2% and 40.3%, respectively. The expression of PCNA and p53 protein in HepG2 cells treated with EGb 761 (1 000 mg/L) was 85% and 174% of the control group, respectively. CONCLUSION: Ginkgo biloba extract significantly can suppress proliferation and increase cytotoxicity in HepG2 and Hep3B cells. Additionally, Ginkgo biloba extract can decrease PCNA and increase p53 expression in HepG2 cells.