乙型肝炎病毒X基因及HBx蛋白的研究进展

我国是乙型肝炎高发区,乙型肝炎病毒(HBV)X基因及其编码的多功能蛋白HBx是乙型肝炎病毒基因转录所必需的作用因子,在乙肝的致病过程中起到重要作用。HBx可直接或间接改变肝脏结构细胞的结构和功能,引发肝脏细胞的凋亡;具有广泛的非特异性反式激活作用,反式激活细胞内的某些癌基因或病毒基因,与乙型肝炎和肝细胞癌的发生关系十分密切。本文从多方面综述了X基因及HBx蛋白目前的研究进展,展现了X基因功能的多样性。     

Polymorphism analyses of hepatitis B virus X gene in hepatocellular carcinoma patients from southern China

Chronic hepatitis B virus(HBV)infection is one of the major causes of hepatocellularcarcinoma(HCC),and the HBV X(HBx)gene plays a critical role in the molecular pathogenesis ofHBV-related HCC.We have investigated whether there are particular HBx gene mutations associated withHCC in patients from southern China.The HBx gene was examined in 51 paraffin-embedded tumor tissuesamples from patients with HCC and 25 serum samples from the HBV carrier by nested polymerase chainreaction(PCR),single-stranded conformational polymorphism and heteroduplex analysis.The HBx geneswith potentially important mutations from tumor tissue samples were cloned,sequenced and aligned withthe published HBx gene sequence.HBV genotypes in tumor tissue samples were analyzed by nested PCR.Analyses of HBx gene polymorphism showed that 31.3% of HBx gene fragments in tumor tissue sampleshad a special pattern.A common deletion at nt 382-400 of the HBx gene accompanied by 29 point mutationswas detected in four randomly selected tumor tissue samples with this pattern which caused a frame-shiftin the HBx open reading frame with a new stop codon at nt 1818,resulting in an HBx polypeptide chaintruncated at the C end in these cases.Among the four randomly selected samples,three were HBV genotypeB,and one was not detected by our present assay.In another tumor tissue sample,amplification of thefull-length HBx gene yielded a shorter fragment.Sequencing of this fragment revealed a 264 bp deletionbetween nt 1577 and 1840 of the HBV gene.These results suggest that HBx gene mutation occurs frequentlyin HCC samples,and the deletion at nt 382-400 of the HBx gene might play a role in carcinogenesis of HCCin southern China.     

HBx expression activates RhoA GTPase: impact on cell migration

HBV (hepatitis B virus) remains a global health concern, especially in developing countries. It has been associated with the development of HCC (hepatocellular carcinoma). One of the four viral proteins, HBx, interacts with cellular proteins, which are involved in a series of cellular processes including cell migration. The Rho GTPases (guanine nucleotide triphosphatases) family of proteins is involved in the regulation of the reorganization of actin and cell migration. We have reported that HBV replication activates Rac1 through SH3 binding. Here, we reported that RhoA was activated by HBx in vitro. The cell motility was enhanced in HepG2 cells co-transfected with HBx and RhoA, compared with those transfected with RhoA alone. Our results were consistent with the recently reported role of RhoA in promoting cell motility and may provide new insights on the mechanism of HBV-associated HCC.     

乙型肝炎病毒变异与肝细胞癌发生关系

乙型肝炎病毒（hepatitisBvirus,HBV）基因组复制时,以病毒前基因组RNA作为模板合成子代病毒DNA,催化该过程的逆转录酶缺乏校对功能,所以HBV易出现变异。近年来,各国学者通过比较肝细胞癌（hepatocellular carcinoma,HCC）患者和非HCC患者的HBV基因序列,发现HBV基本核心启动子区的A1762T／G1764A变异或T1753V变异、增强子Ⅰ区的G1053A或G1229A变异、前S蛋白的F141L变异、前s2区基因缺失变异和x基因的截短变异,分别是HCC的易患因素,而前c区常见的G1896A变异,与HCC的发生无关。增强子Ⅱ区的C1653T变异在c基因HBV感染中可能与发生HCC有关,而在A基因型可能无关。     

肝细胞在HBx刺激和低氧压力时表达IL-2

肝细胞肝癌有极端坏的预后,主要归因于它的高转移性复发．我们曾经报道过对于乙型肝炎相关性肝癌患者,癌周组织的白介素2 (IL-2)水平越高就倾向于有更低的肝内转移复发率,而且IL-2的免疫组化显示主要着色于癌周的肝细胞．然而,是否肝细胞能在体外表达IL-2以及其内在机制仍未被揭示．本研究里,比较了有和没有肝炎病史的肝癌患者的癌周组织IL-2表达水平,然后在永生化的成人肝细胞THLE-2里过表达了乙型肝炎病毒x蛋白(HBx),并用过氧化氢处理模拟氧压力微环境．实验证实肝细胞在HBx刺激和低氧压力同时存在下能通过MAP3K7/NF-κB通路表达IL-2．研究结果提示靶向调节微环境氧化压力为预防和治疗乙肝相关性肝癌的转移复发提供了新的方向．     

CpG-ODN2216致敏的单核细胞培养上清对HBV相关性肝癌病人的树突状细胞表型和功能的影响

目的:研究CpG-ODN2216致敏的外周血单核细胞(PBMC)培养上清液对HBV相关性肝癌病人的树突状细胞(DC)成熟与功能的影响,寻求一种增强DC疫苗效果的方法。方法:从9例HBV相关性肝癌患者PBMC中诱导出未成熟的单核细胞来源的DC(MoDC),经HBV核心抗原(HBcAg)负载后,用CpG-ODN2216刺激的PBMC上清液、“细胞因子鸡尾酒(IL-1β、IL-6、TNF-α和PGE2)”以及两者的联合作用促进MoDC的进一步成熟,检测MoDC表型和功能;选择其中5例HLA-A2 病人,用成熟MoDC诱导自身T细胞产生HBV特异性CD8 的细胞毒性T淋巴细胞(CTL)。结果:用细胞因子鸡尾酒和CpG-ODN2216刺激的PBMC上清液联合作用可明显增强MoDC表面的CD80、CD83和CD1a表达,其对HBcAg负载的MoDC促成熟作用大于单独用细胞因子鸡尾酒或单独用CpG-ODN2216刺激PBMC的上清液。联合作用促进MoDC分泌IL-12和IL-10的能力明显强于单独应用PBMC上清液或细胞因子鸡尾酒,其刺激自体T细胞分泌IFN-γ、TNF-α、IL-6的能力也明显增高。联合作用促成熟的MoDC诱导HLA-A2 病人的自体T细胞产生HBVcore18-27特异性CD8 CTL的频率明显高于细胞因子鸡尾酒单独促成熟的MoDC。结论:CpG-ODN2216刺激PBMC的上清液和细胞因子鸡尾酒联合作用可以明显促进HBcAg负载的HBV相关性肝癌病人的MoDC成熟,增强MoDC分泌细胞因子、刺激自体特异性T淋巴细胞应答、诱导HBV特异性细胞毒性T细胞的能力。为提高HBV特异性树突状细胞疫苗的效果提供了一种可行方案。     

HBx参与肝细胞癌发生发展调控的分子机制

肝细胞癌 (hepatocellular carcinoma, HCC)是我国最常见的恶性肿瘤之一,而HBV慢性感染是肝癌发生的主要原因.乙型肝炎病毒(HBV)中X基因编码的一种多功能蛋白(HBx),参与众多重要生物学过程的调控,并促进肝细胞癌的发生. 早期研究表明,HBx在HCC发生过程中发挥重要的调控功能,但其确切分子机制尚未完全明确. 近几年,HBx参与生物学过程的分子机制研究有了较快的进展. 有趣的是,研究发现,HBx在不同的细胞系以及HBV感染的不同阶段发挥促抑凋亡的双重作用,HBx还参与细胞自噬的调控. 此外,在HBx参与细胞增殖及肿瘤侵袭和转移等方面,也产生了一些新的认识. 本文将从HBx对肝细胞凋亡、自噬和增殖的调控及其对肝癌细胞转移和侵袭的调控等方面,对HBx参与肝细胞癌发生发展调控机制做一综述.     

Hepatitis B virus X protein inhibits autophagic degradation by impairing lysosomal maturation

Deficiency in autophagy, a lysosome-dependent cell degradation pathway, has been associated with a variety of diseases especially cancer. Recently, the activation of autophagy by hepatitis B virus X (HBx) protein, which is implicated in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC), has been identified in hepatic cells. However, the underlying mechanism and the relevance of HBx-activated autophagy to the carcinogenesis caused by HBV remain elusive. Here, by transfection of HBV genomic DNA and HBx in hepatic and hepatoma cells, we showed that HBV- or HBx-induced autophagosome formation was accompanied by unchanged MTOR (mechanistic target of rapamycin) activity and decreased degradation of LC3 and SQSTM1/p62, the typical autophagic cargo proteins. Further functional and morphological analysis indicated that HBx dramatically impaired lysosomal acidification leading to a drop in lysosomal degradative capacity and the accumulation of immature lysosomes possibly through interaction with V-ATPase affecting its lysosome targeting. Moreover, clinical specimen test showed increased SQSTM1 and immature lysosomal hydrolase CTSD (cathepsin D) in human liver tissues with chronic HBV infection and HBV-associated liver cancer. These data suggest that a repressive effect of HBx on lysosomal function is responsible for the inhibition of autophagic degradation, and this may be critical to the development of HBV-associated HCC.     

乙型肝炎病毒X基因转基因小鼠模型的建立及其应用研究进展

主要介绍了乙型肝炎病毒X基因转基因小鼠模型的建立,及其在HBx的反式激活作用和肝细胞癌等方面的研究进展。     

Comparison of genome-scale DNA methylation profiles in hepatocellular carcinoma by viral status

Hepatocellular carcinoma (HCC) incidence has steadily increased in the US over the past 30 years. Our understanding of epigenetic regulation in HCC is still limited, especially the impact of hepatitis B virus (HBV) or hepatitis C virus (HCV) infection on aberrant DNA methylation. We performed genome-wide DNA methylation profiling in 33 fresh frozen tumor samples, including 10 HBV-HCC, 13 HCV-HCC, and 10 non-infected (NIV-HCC) using the Illumina HumanMethylation450 BeadChip. Gene expression profiling was also performed using the Illumina whole-genome DASL HT Assay. Biological influences and gene networks of the differentially-methylated (DM) CpG loci were predicted using the Ingenuity Pathway Analysis. Genome-wide methylation analysis identified 7, 26, and 98 DM loci between HBV-HCC vs. HCV-HCC, HBV-HCC vs. NIV-HCC, and HCV-HCC vs. NIV-HCC, respectively, at P < 5 × 10^?5 for each. Overall, the DM loci were highly enriched for enhancers (48%), promoters (37%), or CpG islands and surrounding regions (37%). Most DM loci were hypermethylated in HCV-HCC compared to HBV-HCC or NIV-HCC. The DM loci were associated with a variety of biological functions including Cell Morphology (HBV-HCC vs. NIV-HCC), Cell Death/ Survival (HBV-HCC vs. NIV-HCC), or Cellular Growth and Proliferation (HCV-HCC vs. NIV-HCC). A subset of the DM loci were correlated (either positively or negatively) with their gene expression or associated with alcohol consumption, BMI, cirrhosis, diabetes, and cigarette smoking. Our findings of differential methylation by viral infection lend insights into the potential effects of viral infection on the epigenetic regulation and further the development and progression of HCC.     

乙肝病毒X 蛋白通过CREB 上调HBx结合蛋白促进肝癌细胞迁移

乙型肝炎病毒X蛋白（hepatitis B virus X protein,HBx）对肝癌的发生发展具有十分重要的作用. HBx 具有促进肝癌迁移的作用,但其作用的分子机制不清. 本研究对 HBx 促进肝癌细胞迁移的分子机制进行了探讨. 伤口愈合和 Boyden’s chamber结果表明,HBx 可明显促进肝癌 HepG2 细胞迁移. 在稳定转染 HBx 的 HepG2（HepG2-X）细胞中转染 HBx 结合蛋白（hepatitis B X-interacting protein,HBXIP）的 RNA 干扰片段,可明显抑制 HBx 的促迁移作用. 免疫组化和实时定量 PCR 结果表明,HBXIP 在肝癌组织中显著高表达,并且与 HBx 表达成正相关. 荧光素酶报告基因和免疫印迹结果表明,HBx 显著增强 HBXIP 的启动子活性和蛋白质表达水平. 应用 HBx 的 RNA 干扰处理 HepG2-X 细胞,HBXIP 的启动子活性和蛋白质表达水平明显下降.将 HBXIP 启动子区的cAMP效应元件结合因子（CREB）结合位点突变后,HBx 上调 HBXIP 的作用消失. 应用 CREB 的 RNA 干扰处理肝癌细胞,在启动子水平和蛋白质水平上, HBx 对 HBXIP 的上调作用被显著抑制. 染色质免疫共沉淀结果表明,HBx 能够通过 CREB 结合到 HBXIP 的启动子上,进而发挥激活 HBXIP 的功能. 本研究结果表明,HBx 促进肝癌细胞迁移的作用是通过 CREB 上调 HBXIP 实现的. 这一发现对进一步揭示 HBx 促进肝癌细胞迁移的分子机制具有重要意义.     

Histochemical and immunohistochemical similarities between hepatic tumors in two chimpanzees and man

A well-differentiated trabecular hepatocellular carcinoma (HCC) and a well-differentiated tumor resembling HCC from each of two chimpanzees were found to have histochemical and immunohistochemical staining characteristics similar to those in human HCCs. Transforming growth factor α was overexpressed in both tumors. Oval cells, thought to be liver stem cell progeny with a possible role in hepatocarcinogenesis, were observed among nontumorous hepatocytes, particularly near the tumors. Hepatic tumors are rare in chimpanzees but their similarities to human HCC provides a useful research model.     

Analysis of hepatocellular carcinoma associated with hepatitis B virus

The hepatitis B virus (HBV) is considered one of the main driving forces in the development of hepatocellular carcinoma (HCC). Human HBV is a partially double-stranded DNA (dsDNA) virus consisting of approximately 3.2 kbp. HBV predominantly infects hepatocytes via the receptor sodium taurocholate cotransporting polypeptide (NTCP) and coreceptor hepatic proteoglycan. The replication of HBV in hepatocytes leads to apoptosis while simultaneously leading to cirrhosis and cancer. Although the integration of dsDNA into the hepatocyte genome seems to be the main cause of mutation, since the discovery of their function, viral proteins have been shown to regulate the P53 pathway or P13K/AKT pathway to prevent host cell apoptosis, causing uncontrolled proliferation of liver cells leading to the formation of solid tumours. The most common treatments involve nucleo(s)tide analogue (NA) and polyethylene glycol (PEG)ylated interferon-alpha (PegIFN-α). NA treatment has been found to be effective for the majority of patients and induces few side effects. Nevertheless, the rate of seroconversion is relatively low. PegIFN treatment is contraindicated during pregnancy and leads to a higher morbidity rate, but the seroconversion rate is high. Since medicines and vaccines have been developed, the incidence and mortality of HBV related to HCC have profoundly decreased compared to those in 2000. This review investigates what can be the potential mechanism that HBV can cause HBV and the treatment used in chronic and acute infection.     

乙肝病毒X基因真核表达质粒及细胞模型的建立

采用聚合酶链反应（PCR）方法扩增HBVX基因,定向亚克隆入真核表达载体pRc／CMV2．构建重组质粒pCMV／X;采用脂质体法转染QSG7701细胞,筛选阳性细胞克隆;RT—PCR法检测HBV XmRNA的表达情况．Western blotting法鉴定HBx蛋白的表达,结果表明,构建的真核重组表达质粒pCMV／X中包含有完整的HBVX基因片断,pCMV／工转染的QSG7701细胞中有HBVXmRNA及HBx蛋白的稳定表达．成功建立了HBVX稳定转染的细胞系,为进一步探讨HBx在HCC的发生发展过程中所起的作用,提供了一个有价值的细胞模型．     

Hepatitis B virus X protein upregulates alpha-fetoprotein to promote hepatocellular carcinoma by targeting miR-1236 and miR-329

Hepatitis B virus (HBV) infection is the most common cause of hepatocellular carcinoma (HCC) worldwide, wherein the expression of alpha-fetoprotein (AFP) is reactivated to promote tumorgenesis. Hepatitis B virus X protein (HBx) protein encoded by the HBV virus X gene has been considered to be oncogenic and implicated in hepatocarcinogenesis. However, the relationship between HBx and abnormal AFP expression in HCC is yet to be fully understood. To explore the potential regulation of HBx on AFP re-expression in HCC, 97 HCC samples of different etiologies were analyzed, and extremely higher serum AFP levels were found in patients with HBsAg⁺. Analyses of HBV-related HCC specimens showed that the expression of AFP was negatively correlated with the levels of miR-1236 and miR-329. Further analyses indicated that HBx promotes the expression of AFP by orchestrating the levels of miR-1236 and miR-329 both in vitro and in vivo. Specifically, miR-1236 and miR-329 bind to the potential target sequences in AFP mRNA 3′-untranslated region to suppress its expression. HBx transfection resulted in the significant decrement of these microRNAs and increment of AFP expression. Moreover, AFP promotes the proliferation of hepatoma cells and attenuates the proapoptotic effect of chemotherapy agents. These findings revealed a novel regulatory mechanism of HBx on the abnormal AFP expression in HCC, which may provide a therapeutic approach for combating HBV-related HCC by targeting the regulation of AFP expression.     

p16在HBsAg和HBx转基因小鼠肝脏肿瘤中的表达

目的:探讨p16基因在由乙型肝炎病毒基因整合引起的小鼠肝细胞癌发生发展中的表达变化规律。方法:以乙肝病毒表面抗原基因(HBsAg)及X基因(HBx)定位整合转基因小鼠及对照小鼠的肝脏组织为标本,利用North-ern印迹、Western印迹及免疫组织化学检测p16在乙肝病毒基因定位整合转基因小鼠肝脏正常组织与肿瘤组织中的差异表达。结果:p16主要在小鼠胚胎期的肝脏中表达,在新生小鼠和成年小鼠的肝脏组织中几乎检测不到其表达;在HBsAg转基因小鼠和HBx转基因小鼠的肝脏肿瘤中,p16的表达明显升高。结论:p16基因在HBsAg或HBx诱导的肝细胞癌发生过程中被重新激活,也许发挥重要的作用。     

COX-2在乙肝病毒X蛋白（HBx）促进肝癌细胞和肝细胞增殖中的作用

乙型肝炎病毒（hepatitis B virus, HBV）X蛋白（HBx）对肝癌的发生发展具有十分重要的作用．大量研究结果表明,与花生四烯酸代谢相关的磷脂酶COX-2与肿瘤细胞的增殖密切相关．为了阐明COX-2在HBx促进肝细胞增殖中的作用,在前期应用基因芯片方法检测发现稳定转染HBx 基因的肝癌细胞H7402-X中COX-2基因表达明显上调的基础上,本研究应用免疫印迹技术在蛋白表达水平上获得了相同的结果．进而,应用COX-2的特异性抑制剂Indo分别作用H7402-X细胞和L-O2-X细胞（稳定转染HBx 基因的人永生化L-O2肝细胞）,观察HBx蛋白是否通过COX-2促进肝癌细胞或肝细胞增殖．BrdU掺入实验和流式细胞仪检测结果显示,50 μmol/L的Indo可明显抑制H7402-X细胞和L-O2-X细胞的增殖．本研究结果提示,HBx可通过COX-2所介导的花生四烯酸代谢促进肝癌细胞和肝细胞增殖．