Molecular mechanisms of viral hepatitis induced hepatocellular carcinoma

Chronic infection with viral hepatitis affects half a billion individuals worldwide and can lead to cirrhosis, cancer, and liver failure. Liver cancer is the third leading cause of cancer-associated mortality, of which hepatocellular carcinoma (HCC)represents 90%of all primary liver cancers. Solid tumors like HCC are complex and have heterogeneous tumor genomic profiles contributing to complexity in diagnosis and management. Chronic infection with hepatitis B virus (HBV),hepatitis delta virus (HDV), and hepatitis C virus (HCV) are the greatest etiological risk factors for HCC. Due to the significant role of chronic viral infection in HCC development, it is important to investigate direct (viral associated) and indirect (immune-associated) mechanisms involved in the pathogenesis of HCC. Common mechanisms used by HBV, HCV, and HDV that drive hepatocarcinogenesis include persistent liver inflammation with an impaired antiviral immune response, immune and viral protein-mediated oxidative stress, and deregulation of cellular signaling pathways by viral proteins.DNA integration to promote genome instability is a feature of HBV infection, and metabolic reprogramming leading to steatosis is driven by HCV infection. The current review aims to provide a brief overview of HBV, HCV and HDV molecular biology, and highlight specific viral-associated oncogenic mechanisms and common molecular pathways deregulated in HCC, and current as well as emerging treatments for HCC.     

Prevention of hepatocellular carcinoma in chronic viral hepatitis B and C infection

Hepatocellular carcinoma(HCC)is a leading cause of cancer-related mortality worldwide,with the majority of cases associated with persistent infection from hepatitis B virus(HBV)or hepatitis C virus(HCV).Natural history studies have identified risk factors associated with HCC development among chronic HBV and HCV infection.High-risk infected individuals can now be identified by the usage of risk predictive scores.Vaccination plays a central role in the prevention of HBV-related HCC.Treatment of chronic HBV infection,especially by nucleoside analogue therapy,could also reduce the risk of HBV-related HCC.Concerning HCV infection,besides the advocation of universal precautions to reduce the rate of infection,pegylated interferon and ribavirin could also reduce the risk of HCV-related HCC among those achieving a sustained virologic response.Recently there has been mounting evidence on the role of chemopreventive agents in reducing HBV-and HCV-related HCC.The continued advances in the understanding of the molecular pathogenesis of HCC would hold promise in preventing this highly lethal cancer.     

Autophagy and microRNA in hepatitis B virus-related hepatocellular carcinoma

Approximately 350 million people worldwide are chronically infected by hepatitis B virus (HBV). HBV causes severe liver diseases including cirrhosis and hepatocellular carcinoma (HCC). In about 25% of affected patients, HBV infection proceeds to HCC. Therefore, the mechanisms by which HBV affects the host cell to promote viral replication and its pathogenesis have been the subject of intensive research efforts. Emerging evidence indicates that both autophagy and microRNAs (miRNAs) are involved in HBV replication and HBV-related hepatocarcinogenesis. In this review, we summarize how HBV induces autophagy, the role of autophagy in HBV infection, and HBV-related tumorigenesis. We further discuss the emerging roles of miRNAs in HBV infection and how HBV affects miRNAs biogenesis. The accumulating knowledge pertaining to autophagy and miRNAs in HBV replication and its pathogenesis may lead to the development of novel strategies against HBV infection and HBV-related HCC tumorigenesis.     

Occult hepatitis B virus and hepatocellular carcinoma

Occult hepatitis B virus (HBV) infection (OBI) is a challenging pathobiological and clinical issue that has been widely debated for several decades. By definition, OBI is characterized by the persistence of HBV DNA in the liver tissue (and in some cases also in the serum) in the absence of circulating HBV surface antigen (HBsAg). Many epidemiological and molecular studies have indicated that OBI is an important risk factor for hepatocellular carcinoma (HCC) development. OBI may exert direct pro-oncogenic effects through the activation of the same oncogenic mechanisms that are activated in the course of an HBsAg-positive infection. Indeed, in OBI as in HBV-positive infection, HBV DNA can persist in the hepatocytes both integrated into the host genome as well as free episome, and may maintain the capacity to produce proteins-mainly X protein and truncated preS-S protein - provided with potential transforming properties. Furthermore, OBI may indirectly favor HCC development. It has been shown that the persistence of very low viral replicative activity during OBI may induce mild liver necro-inflammation continuing for life, and substantial clinical evidence indicates that OBI can accelerate the progression of liver disease towards cirrhosis that is considered the most important risk factor for HCC development.     

乙型肝炎病毒X基因突变与肝细胞癌

原发性肝细胞癌是世界上最常见的恶性肿瘤之一,慢性HBV感染是导致肝细胞癌的主要病因。HBV诱发肝细胞癌的确切机制仍不十分清楚。目前在HBV相关肝细胞癌病人血清和肝癌组织中发现了许多HBV X基因突变体,一些与肝细胞癌发生发展密切相关。本文主要就HBV X基因突变与肝细胞癌研究进展进行综述。     

肝癌组织中多基因甲基化与乙型肝炎病毒感染的关系

目的 评估HBV感染与非HBV感染的肝癌组织中多基因（p14、p15、p16和RB）甲基化状态,探讨HBV感染诱导基因甲基化在肝癌发病机制中的作用.方法 运用甲基化特异性聚合酶链反应（PCR）方法检测32例HBV感染和12例非HBV感染患者的肝癌组织中p14、p15、p16和RB的甲基化状态,应用实时荧光定量PCR技术检测44例血标本中HBV DNA.结果 44例肝癌组织中p14、p15、p16和RB基因的甲基化检出率分别为34.1％、56.8％、70.5％和27.3％；HBV感染与非HBV感染患者的肝癌组织中p14、p15、p16和RB4种基因的甲基化检出率分别为43.8％和8.3％、68.9％和25.0％、90.6％和16.7％、28.1％和25.0％；HBV感染与p14、p15、p16基因的甲基化明显相关（P=0.048、0.035、0.020）,HBV DNA扩增与p14、p15、p16基因的甲基化明显相关（P均＜0.05）.结论 （1）p14、p15、p16、RB基因甲基化是肝癌发生的频发事件；（2）HBV病毒感染与p14、p15、p16基因的甲基化相关；（3）HBV感染诱导相关基因高甲基化可能是HBV相关性肝癌的发病机制之一.     

Prevention of hepatocellular carcinoma in patients with chronic hepatitis B

Patients with chronic hepatitis B are at significant risk for hepatocellular carcinoma(HCC). Globally,over half a million people each year are diagnosed with HCC,with marked geographical variations. Despite overwhelming evidence for a causal role of hepatitis B virus(HBV) infection in the development of HCC and a well-established relationship between high baseline hepatitis B viral load and cumulative risk of HCC,the molecular basis for this association has not been fully elucidated. In addition,a beneficial role for antiviral therapy in preventing the development of HCC has been difficult to establish. This review examines the biological and molecular mechanisms of HBV-related hepatocarcinogenesis,recent results on the effect of modern nucleos(t)ides on the rate of HCC development in high risk HBV cohorts and the potential mechanisms by which long-term antiviral therapy with potent inhibitors of HBV replication might reduce the risk of HCC in patients with chronic hepatitis B. Although evidence from randomized controlled trials shows the favourable effects of antiviral agentsin achieving profound and durable suppression of HBV DNA levels while improving liver function and histology,robust evidence of other long-term clinical outcomes,such as prevention of HCC,are limited.     

Molecular mechanism of hepatitis B virus-induced hepatocarcinogenesis

Hepatitis B virus (HBV) infection is a global public health problem with approximately 2 billion people that have been exposed to the virus. HBV is a member of a family of small, enveloped DNA viruses called hepadnaviruses, and has a preferential tropism for hepatocytes of mammals and birds. Epidemiological studies have proved a strong correlation between chronic hepatitis B virus infection and the development of hepatocellular carcinoma (HCC). HCC is the fifth most common malignancy with about 700000 new cases each year, and more than 50% of them arise in HBV carriers. A large number of studies describe the way in which HBV can contribute to HCC development. Multiple mechanisms have been proposed, including the accumulation of genetic damage due to immune-mediated hepatic inflammation and the induction of oxidative stress. There is evidence of the direct effects of the viral proteins HBx and HBs on the cell biology. Integration of HBV-DNA into the human genome is considered an early event in the carcinogenic process and can induce, through insertional mutagenesis, the alteration of gene expression and chromosomal instability. HBV has also epigenetic effects through the modification of the genomic methylation status. Furthermore, the virus plays an important role in the regulation of microRNA expression. This review will summarize the many mechanisms involved in HBV-related liver carcinogenesis.     

乙型肝炎病毒致肝细胞癌发生机制研究进展

肝细胞癌（HCC）的发生与乙型肝炎病毒（HBV）感染密切相关。HBV感染所致的炎症反应、HBV X基因及其产物X蛋白、核心启动子突变、前S2区突变、剪接特异性蛋白等均可能参与HCC的发生发展。     

Clinical analysis of the risk factors for recurrence of HCC and its relationship with HBV

AIM: To comprehend the risk factors of recurrence of hepatocellular carcinoma (HCC) and its relationship with the infection patterns of hepatitis B virus (HBV).METHODS: All materials of 270 cases of postoperative HCC were statistically analyzed by SPSS software.Recurrence and metastasis were classified into early( ≤2 years) and late phase (>2 years). Risk factors for recurrence and metastasis after surgery in each group were analyzed.RESULTS: Out of 270 cases of HCC, 162 cases were followed up in which recurrence and metastasis occurred in 136 cases. There were a lot of risk factors related to recurrence and metastasis of HCC; risk factors contributing to early phase recurrence were serum AFP level, vascular invasion, incisal margin and operative transfusion, gross tumor classification and number of intrahepatic node to late phase recurrence. The HBV infective rate of recurrent HCC was 94.1%, in which ““HBsAg, HBeAb, HBcAb““ positive pattern reached 45.6%. The proportion of HBV infection in solitary large hepatocellular carcinoma (SLHCC)evidently decreased compared to nodular hepatocellular carcinoma (NHCC) (P<0.05).CONCLUSION: The early and late recurrence and metastasis after hepatectomy of HCC were associated with different risk factors. The early recurrence may be mediated by vascular invasion and remnant lesion, the late recurrence by tumor‘s clinical pathology propert, as multicentric carcinogenesis or intrahepatic carcinoma de novo. HBV replication takes a great role in this process.From this study, we found that SLHCC has more satisfactory neoplasm biological behavior than NHCC.     

The influence of hepatitis B virus genotype and subgenotype on the natural history of chronic hepatitis B

Background  Chronic infection with hepatitis B virus (HBV) is associated with a high lifetime risk of developing hepatocellular carcinoma (HCC) and cirrhosis of the liver. Purpose  To review the studies published to date regarding the association of HBV genotypes and subgenotypes in the development of adverse sequelae from HBV. Methods  Review of the literature for articles describing studies of HBV genotype/subgenotypes and development of HCC, cirrhosis, and liver-related death. Results  Eight genotypes of HBV (A through H), which differ from each other in viral genome sequence by more than 8%, and multiple subgenotypes, which differ from each other by 4–8% have been identified. Recently, studies investigating the association between the risks of developing HCC and cirrhosis by specific HBV genotypes and subgenotypes have reported marked differences in outcome. Certain HBV genotypes and subgenotypes, including genotype C, B2-5, and F1, appear to be associated with a higher risk of developing HCC, and others, including genotypes B1, B6, and A2, appear to be associated with a lower risk of complications of HBV. Our understanding of the role of HBV genotypes and subgenotypes on the outcome of HBV infection is limited, as few population-based prospective studies have been performed and most studies compare only the outcome in areas where two genotypes predominate whereas others have not examined subgenotypes. Conclusions  Studies to date suggest that HBV genotypes/subgenotypes have important influences on the outcome of chronic HBV infection, but more population-based prospective studies examining multiple genotypes are needed.     

Hepatitis B virus-induced oncogenesis

Hepatocellular carcinoma (HCC) is one of the most common cancers in the world with an annual incidence of more than 500000 in the year 2000. Its incidence is rising in many countries. Recently, it has been estimated that about 53% of HCC cases in the world are related to hepatitis B virus (HBV). The epidemiological association of HBV with HCC is well established. In recent studies,it was revealed that HBsAg carriers have a 25-37times increased risk of developing HCC as compared to non-infected people. At present, HBV-associated carcinogenesis can be seen as a multi-factorial process that includes both direct and indirect mechanisms that might act synergistically. The integration of HBV DNA into the host genome occurs at early steps of clonal tumor expansion. The integration has been shown in a number of cases to affect a variety of cancerrelated genes and to exert insertional mutagenesis. The permanent liver inflammation, induced by the immune response, resulting in a degeneration and regeneration process confers to the accumulation of critical mutations in the host genome. In addition to this, the regulatory proteins HBx and the PreS2 activators that can be encoded by the integrate exert a tumor promoter-like function resulting in positive selection of cells producing a functional regulatory protein. Gene expression profiling and proteomic techniques may help to characterize the molecular mechanisms driving HBV-associated carcinogenesis, and thus potentially identify new strategies in diagnosis and therapy.     

Hepatitis B virus persistent infection-related single nucleotide polymorphisms in HLA regions are associated with viral load in hepatoma families

BACKGROUNDGenome-wide association studies from Asia indicate that HLA-DP and HLA-DQ loci are important in persistent hepatitis B virus (HBV) infections. One of the key elements for HBV-related carcinogenesis is persistent viral replication and inflammation.AIMTo examine genetic and nongenetic factors with persistent HBV infection and viral load in families with hepatocellular carcinoma (HCC).METHODSThe HCC families included 301 hepatitis B surface antigen (HBsAg) carriers and 424 noncarriers born before the nationwide vaccination program was initiated in 1984. Five HBV-related single nucleotide polymorphisms (SNPs) — rs477515, rs9272105, rs9276370, rs7756516, and rs9277535 — were genotyped. Factors associated with persistent HBV infection and viral load were analyzed by a generalized estimating equation.RESULTSIn the first-stage persistent HBV study, all SNPs except rs9272105 were associated with persistent infection. A significantly higher area under the reciprocal operating characteristic curve for nongenetic factors vs genetic factors (P < 0.001) suggests that the former play a major role in persistent HBV infection. In the second-stage viral load study, we added 8 HBsAg carriers born after 1984. The 309 HBsAg carriers were divided into low (n = 162) and high viral load (n = 147) groups with an HBV DNA cutoff of 10⁵ cps/mL. Sex, relationship to the index case, rs477515, rs9272105, and rs7756516 were associated with viral load. Based on the receiver operating characteristic curve analysis, genetic and nongenetic factors affected viral load equally in the HCC family cohort (P = 0.3117).CONCLUSIONIn these east Asian adults, the mechanism of persistent HBV infection-related SNPs was a prolonged viral replication phase.     

MicroRNAs as therapeutic strategy for hepatitis B virus-associated hepatocellular carcinoma: Current status and future prospects

Hepatocellular carcinoma (HCC) remains to be one of the top causing cancer-related deaths today. The majority of HCC cases are reported to be the result of chronic hepatitis B virus (HBV) infection. Current treatments for HBV-related HCC revolve around the use of drugs to inhibit viral replication, as a high level of viral load and antigen in circulation often presents a poor patient prognosis. However, existing therapies are inefficient in the complete eradication of HBV, often resulting in tumour recurrence. The involvement of microRNAs (miRNAs) in important processes in HBV-related HCC makes it an important player in the progression of HCC in chronic hepatitis B infected patients. In this review, we discuss the key aspects of HBV infection and the important viral products that may regulate cancer-related processes via their interaction with miRNAs or their closely related protein machinery. Conversely, we also look at how miRNAs may go about regulating the virus, especially in vital processes like viral replication. Apart from miRNAs acting as either oncogenes or tumour-suppressors, we also look at how miRNAs may function as biomarkers that may possibly serve as better candidates than those currently employed in the diagnosis of HBV infection or HBV-related HCC. A summary of the roles of miRNAs in HBV-related HCC will hopefully lead to a gain in understanding of the pathogenesis process and pave the way for new insights in medical therapy.     

乙型与丙型肝炎病毒感染对小肝癌患者预后的影响

目的 探讨HBV、HCV感染对小肝癌的外科治疗策略及其预后的影响.方法 回顾性分析1997年1月-2003年12月天津医科大学附属肿瘤医院413例手术根治切除治疗的小肝痛(≤3 cm)患者的临床资料,将其分为4组:HCV感染组75例、HBV感染组251例、HCV、HBV混合感染组33例和尢HCV、HBV感染组54例,对可能影响预后的因素采用Kaplan-Meier生存分析、log-rank时序检验.结果 413例患者术后1、3、5年尢瘤生存率分别为83%、66%和58%,术后共有168(40.8%)例患者出现肝内复发,5年复发率HCV感染组最高(64.2%),其次为HBV/HCV感染组(48.4%),HBV感染组(37.8%)及无感染组(32.3%).肝内复发肿瘤为多发者在HCV感染组发生率最高(占肝内复发肿瘤的66.0%),其次为HBV/HCV感染组(28.6%),HBV感染组(23.3%)及无感染组(17.6%).413例小肝癌患者术后1、3、5年总生存率分别为89%、70%和61%,HCV感染组预后最差.和其他组相比,HCV感染组肝硬化程度严重,肿瘤细胞分化低,更易发生血管侵犯.在随访过程中,HCV感染组肝内复发率高,且复发类型常为多结节型.结论 HCV感染相关肝癌的临床肝硬化症状更重,而且术后复发率较高,预后更差.     

Lower serum viral loads in young patients with hepatitis-B-virus-related hepatocellular carcinoma

Advanced age and high hepatitis B virus (HBV) DNA level are risk factors associated with the development of HBV-related hepatocellular carcinoma (HCC). However, little is known about the role of viral load in the carcinogenesis of HCC in young people. A total of 183 HBV-related HCC patients and 202 HBV carriers were therefore enrolled to compare serum viral loads in young (40 years of age) age groups. Other factors associated with the development of HCC were also analysed. The results showed that serum alanine aminotransferase (38.7 +/- 24.1 vs 58.4 +/- 65.4 IU/L, P = 0.006) and HBV DNA levels (log(10) titre: 4.20 +/- 1.33 vs 4.80 +/- 1.39, P = 0.053) were lower in young HCC patients than in old HCC patients. There was a positive correlation between age and serum HBV DNA level in HCC patients but a negative correlation in HBV carriers. Young HCC patients with HBV genotype B infection had higher viral loads than those with genotype C infection (log(10) titre: 4.79 +/- 1.34 vs 3.27 +/- 0.60, P = 0.001). By multivariate logistic regression analyses, high serum HBV DNA level was associated with the development of HCC in old patients [odds ratio (OR) 1.584, 95% confidence interval (CI) 1.075-2.333] rather than in young patients (OR 0.848, 95% CI 0.645-1.116). In conclusion, viral factors in association with the development of HBV-related HCC in young patients may be different from their old counterparts. The complicated interplay between host and virus could be responsible for the emergence and aggressive outcome of early-onset HCC.     

Viral hepatitis and hepatocellular carcinoma: From molecular pathways to the role of clinical surveillance and antiviral treatment

Hepatocellular carcinoma (HCC) is a global health challenge. Due to the high prevalence in low-income countries, hepatitis B virus (HBV) and hepatitis C virus infections remain the main risk factors for HCC occurrence, despite the increasing frequencies of non-viral etiologies. In addition, hepatitis D virus coinfection increases the oncogenic risk in patients with HBV infection. The molecular processes underlying HCC development are complex and various, either independent from liver disease etiology or etiology-related. The reciprocal interlinkage among non-viral and viral risk factors, the damaged cellular microenvironment, the dysregulation of the immune system and the alteration of gut-liver-axis are known to participate in liver cancer induction and progression. Oncogenic mechanisms and pathways change throughout the natural history of viral hepatitis with the worsening of liver fibrosis. The high risk of cancer incidence in chronic viral hepatitis infected patients compared to other liver disease etiologies makes it necessary to implement a proper surveillance, both through clinical-biochemical scores and periodic ultrasound assessment. This review aims to outline viral and microenvironmental factors contributing to HCC occurrence in patients with chronic viral hepatitis and to point out the importance of surveillance programs recommended by international guidelines to promote early diagnosis of HCC.     

Hepatocellular carcinoma: The virus or the liver?

Hepatocellular carcinoma (HCC) represents a major public health problem being one of the most common causes of cancer-related deaths worldwide. Hepatitis B (HBV) and C viruses have been classified as oncoviruses and are responsible for the majority of HCC cases, while the role of hepatitis D virus (HDV) in liver carcinogenesis has not been elucidated. HDV/HBV coinfection is related to more severe liver damage than HBV mono-infection and recent studies suggest that HDV/HBV patients are at increased risk of developing HCC compared to HBV mono-infected patients. HBV is known to promote hepatocarcinogenesis via DNA integration into host DNA, disruption of molecular pathways by regulatory HBV x (HBx) protein and excessive oxidative stress. Recently, several molecular mechanisms have been proposed to clarify the pathogenesis of HDV-related HCC including activation of signalling pathways by specific HDV antigens, epigenetic dysregulation and altered gene expression. Alongside, ongoing chronic inflammation and impaired immune responses have also been suggested to facilitate carcinogenesis. Finally, cellular senescence seems to play an important role in chronic viral infection and inflammation leading to hepatocarcinogenesis. In this review, we summarize the current literature on the impact of HDV in HCC development and discuss the potential interplay between HBV, HDV and neighbouring liver tissue in liver carcinogenesis.     

Hepatitis B Virus Vaccine for Patients with Hepatitis C Virus Infection

Summary Hepatitis C is a disease with varying rates of progression. The role of hepatitis B virus (HBV) as a cofactor in the development of hepatitis C virus (HCV)-related cirrhosis and hepatocellular carcinoma (HCC) has been suggested and the use of HBV vaccine in all HCV-infected patients has been advocated. This review presents the implications of HBV and HCV coinfection and addresses the issues of HBV vaccine immunogenicity and safety in patients with chronic HCV infection. Received: December, 1999 · Revision accepted: July 1, 2000