Interactions between hepatitis B virus infection and exposure to aflatoxins in the development of hepatocellular carcinoma: a molecular epidemiological approach.

Aflatoxins and hepatitis B virus (HBV) are major risk factors for hepatocellular carcinoma (HCC) in high incidence areas for this cancer, namely southeast Asia and parts of Africa. There is evidence from both epidemiological studies and animal models that the two factors can act synergistically to increase the risk of HCC. The cellular and molecular mechanism of the interaction between these two factors is as yet undefined. However, one possible mechanism attested to by studies in HBV transgenic mice is that chronic liver injury alters the expression of specific carcinogen metabolising enzymes thus modulating the binding of aflatoxin to DNA in hepatocytes. The high levels of aflatoxin exposure which occur in many areas of the world where chronic HBV infection is endemic indicate that measures to reduce aflatoxin exposure would contribute to reducing HCC incidence. In preliminary studies, Guinea-Conakry have established baseline data for the implementation of a community-based intervention study to evaluate the effectiveness of improved post-harvest processing and storage of the groundnut crop, a major source of aflatoxins. Aflatoxin-albumin adducts were measured in 423 sera from individuals living in the four natural geographic zones of Guinea. More than 95% of the serum samples were positive for this biomarker and highest exposures were found in Lower Guinea where groundnuts are consumed as a dietary staple. Variations in mean levels between villages within a geographic region did not vary greatly. HBV infection was endemic in all regions with an overall prevalence of 16.7% chronic carriers. Thus in this population both HBV vaccination and reduction in aflatoxin exposure would be beneficial in decreasing morbidity and mortality from liver disease.     

Changing pattern of hepatocellular carcinoma (HCC) and its risk factors in Egypt: possibilities for prevention

The burden of hepatocellular carcinoma (HCC) has been increasing in Egypt with a doubling in the incidence rate in the past 10 years. This has been attributed to several biological (e.g. hepatitis B and C virus infection) and environmental factors (e.g. aflatoxin, AF). Other factors such as cigarette smoking, occupational exposure to chemicals such as pesticides, and endemic infections in the community, such as schistosomiasis, may have additional roles in the etiology or progression of the disease. Estimates of the burden of cancer caused by these factors provide an opportunity for prevention. Previously, there was strong evidence that hepatitis B virus (HBV) was the major cause of HCC in Egypt, but more recently HCV has become the predominant factor associated with the more recent epidemic of HCC. It has been well documented that Egypt has one of the highest prevalence rates of HCV infection in the world. The natural history of HCV infection and disease progression, however, are influenced by additional factors such as duration of infection, age at infection, sex, co-infection with HBV, the level of HCV viraemia and its genotype. The role of exposure to aflatoxins and development of HCC in Egypt was historically less clear. Nevertheless, recent food sampling surveys and population-based studies indicated that exposure to aflatoxins in Egypt may have been underestimated in the past. Recent results indicated that both local and imported samples were positive for aflatoxin B1 (AFB1, 17.5% and 20%, respectively), with concentrations ranging from 3 to 25 microg/kg. The level of AFB1 was dependent on the area of collection as well as the season of the year. In a population-based study, the level and frequency of aflatoxin M1 (AFM1, a major metabolite of aflatoxin B1 excreted in breast milk) was assessed as a biomarker of maternal exposure. The samples were collected from a selected group of 388 Egyptian lactating mothers during May-September 2003. Non-working status, obesity, high corn oil consumption, and the number of offspring contributed to the variability in occurrence of AFM1 in breast milk. Prevention and intervention approaches directed to risk factors of HCC can play a critical role in its prevention. In the case of HCV infection a prevention programme can be achieved by changing personal behaviors and/or cultural habits which are risk factors for HCV transmission, such as injection with contaminated syringes, blood transfusion, surgical operations, venous catheterization, use of common syringes, dental treatment and circumcision at home. Prevention of exposure to aflatoxins can be achieved either at community (via good agriculture practices) or individual levels (treatment or dietary interventions). In conclusion, due to the alarming increase in the incidence of HCC in Egypt, there is a need to further investigate the contribution of these emerging risk factors to the development of HCC in Egypt. This may enable us to determine the susceptibility to HCC among high-risk groups and to provide these individuals with effective measures for early prevention or intervention.     

Viral hepatitis and hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the world. The incidence of HCC varies considerably with the geographic area because of differences in the major causative factors. Chronic hepatitis B and C, mostly in the cirrhotic stage, are responsible for the great majority of cases of HCC worldwide. The geographic areas at the highest risk are South-East Asia and sub-Saharan Africa, here hepatitis B is highly endemic and is the main cause of HCC. In areas with an intermediate rate of HCC such as Southern Europe and Japan, hepatitis C is the predominant cause, whereas in low rate areas such as Northern Europe and the USA, HCC is often related to other factors as alcoholic liver disease. There is a rising incidence in HCC in developed countries during the last two decades, due to the increasing rate of hepatitis C infection and improvement of the clinical management of cirrhosis.

Methods

This article reviews the literature on hepatitis and hepatocellular carcinoma. The Medline search was carried out using these key words and articles were selected on epidemiology, risk factors, screening, and prevention of hepatocellular carcinoma.

Results

Screening of patients with advanced chronic hepatitis B and C with hepatic ultrasound and determination of serum alfa-fetoprotein may improve the detection of HCC, but further studies are needed whether screening improves clinical outcome. Hepatitis B and C viruses (HBV/HCV) can be implicated in the development of HCC in an indirect way, through induction of chronic inflammation, or directly by means of viral proteins or, in the case of HBV, by creation of mutations by integration into the genome of the hepatocyte.

Conclusion

The most effective tool to prevent HCC is avoidance of the risk factors such as viral infection. For HBV, a very effective vaccine is available. Preliminary data from Taiwan indicate a protective effect of universal vaccination on the development of HCC. Vaccination against HBV should therefore be a health priority. In patients with chronic hepatitis B or C, interferon-alfa treatment in a noncirrhotic stage is protective for HCC development in responders, probably by prevention of cirrhosis development. When cirrhosis is already present, the protective effect is less clear. For cirrhosis due to hepatitis B, a protective effect was demonstrated in Oriental, but not in European patients. For cirrhosis due to hepatitis C, interferon-alfa treatment showed to be protective in some studies, especially in Japan with a high incidence of HCC in untreated patients. Virological, but also merely biochemical response, seems to be associated with a lower risk of development of HCC. As most studies are not randomized controlled trials, no definitive conclusions on the long-term effects of interferon-alfa in HBV or HCV cirrhosis can be established. Especially in hepatitis C, prospective studies should be performed using the more potent reference treatments for cirrhotics, namely the combination of peginterferon and ribavirin.     

Cancer-associated carbohydrate antigens as potential biomarkers for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common human malignancies. Therefore, developing the early, high-sensitivity diagnostic biomarkers to prevent HCC is urgently needed. Serum a-fetoprotein (AFP), the clinical biomarker in current use, is elevated in only ~60% of patients with HCC; therefore, identification of additional biomarkers is expected to have a significant impact on public health. In this study, we used glycan microarray analysis to explore the potential diagnostic value of several cancer-associated carbohydrate antigens (CACAs) as biomarkers for HCC. We used glycan microarray analysis with 58 different glycan analogs for quantitative comparison of 593 human serum samples (293 HCC samples; 133 chronic hepatitis B virus (HBV) infection samples, 134 chronic hepatitis C virus (HCV) infection samples, and 33 healthy donor samples) to explore the diagnostic possibility of serum antibody changes as biomarkers for HCC. Serum concentrations of anti-disialosyl galactosyl globoside (DSGG), anti-fucosyl GM1 and anti-Gb2 were significantly higher in patients with HCC than in chronic HBV infection individuals not in chronic HCV infection patients. Overall, in our study population, the biomarker candidates DSGG, fucosyl GM1 and Gb2 of CACAs achieved better predictive sensitivity than AFP. We identified potential biomarkers suitable for early detection of HCC. Glycan microarray analysis provides a powerful tool for high-sensitivity and high-throughput detection of serum antibodies against CACAs, which may be valuable serum biomarkers for the early detection of persons at high risk for HCC.     

Epigenetic mechanisms in hepatocellular carcinoma: how environmental factors influence the epigenome

Epigenetic mechanisms maintain heritable changes in gene expression and chromatin organization over many cell generations. Importantly, deregulated epigenetic mechanisms play a key role in a wide range of human malignancies, including liver cancer. Hepatocellular carcinoma (HCC), which originates from the hepatocytes, is by far the most common liver cancer, with rates and aetiology that show considerable geographic variation. Various environmental agents and lifestyles known to be risk factors for HCC (such as infection by hepatitis B virus (HBV) and hepatitis C virus (HCV), chronic alcohol intake, and aflatoxins) are suspected to promote its development by eliciting epigenetic changes, however the precise gene targets and underlying mechanisms have not been elucidated. Many recent studies have exploited conceptual and technological advances in epigenetics and epigenomics to investigate the role of epigenetic events induced by environmental factors in HCC tumors and non-tumor precancerous (cirrhotic) lesions. These studies have identified a large number of genes and pathways that are targeted by epigenetic deregulation (changes in DNA methylation, histone modifications and RNA-mediated gene silencing) during the development and progression of HCC. Frequent identification of aberrant epigenetic changes in specific genes in cirrhotic tissue is consistent with the notion that epigenetic deregulation of selected genes in pre-malignant lesions precedes and promotes the development of HCC. In addition, several lines of evidence argue that some environmental factors (such as HBV virus) may abrogate cellular defense systems, induce silencing of host genes and promote HCC development via an "epigenetic strategy". Finally, profiling studies reveal that HCC tumors and pre-cancerous lesions may exhibit epigenetic signatures associated with specific risk factors and tumor progression stage. Together, recent evidence underscores the importance of aberrant epigenetic events induced by environmental factors in liver cancer and highlights potential targets for biomarker discovery and future preventive and therapeutic strategies.     

丙型肝炎病毒（HCV）实验性疫苗的研究进展

丙型肝炎病毒是引起输血相关肝炎及慢性肝炎、肝硬化、肝癌的主要病原,目前尚无有效的治疗与预防手段。本文将综述HCV感染所引起的机体免疫应答及近年来实验性疫苗（主要是DNA疫苗、病毒载体疫苗及联合疫苗）的研究进展。     

Human oncogenic viruses: Hepatitis B and hepatitis C viruses and their role in hepatocarcinogenesis

Chronic infections caused by hepatitis B virus (HBV) and/or hepatitis C virus (HCV) are the main risk factors for the development of hepatocellular carcinoma (HCC) in humans. Both viruses cause a wide spectrum of clinical manifestations ranging from healthy carrier state to acute and chronic hepatitis, liver cirrhosis, and HCC. HBV and HCV belong to different viral families (Hepadnoviridae and Flaviviridae, respectively); they are characterized by different genetic structures. Clinical manifestations of these viral infections result from the interaction between these viruses and host hepatocytes (i.e. between viral and cell genomes). Proteins encoded by both viruses play an important role in processes responsible for immortalization and transformation of these cells. Chronic inflammation determined by host immune response to the viral infection, hepatocyte death and their compensatory proliferation, as well as modulation of expression of some regulatory proteins of the cell (growth factors, cytokines, etc.) are the processes that play the major role in liver cancer induced by HBV and HCV.     

MicroRNA in HCV infection and liver cancer

In the more than two-decades since hepatitis C virus (HCV) was identified, there has been considerable improvement in our understanding of virus life cycle due largely to the development of in vitro culture systems for virus replication. Still challenges remain: HCV infection is a major risk factor for chronic hepatitis, liver cirrhosis and hepatocellular carcinoma worldwide; yet mechanistic details of HCV infection-associated hepatocarcinogenesis remain incompletely understood. A protective vaccine is not yet available, and current therapeutic options result in sustained virus clearance only in a subset of patients. Recent interest has focused on small non-protein coding RNAs, microRNAs (miRNAs), the dependence of virus replication on miRNAs, and miRNA-regulated genes in liver cancer. Functional analysis of the miRNA-targeted genes in liver cancer has advanced our understanding of the "oncomiRs" and their role in hepatocarcinogenesis. This review focuses on the dependence of HCV replication on miRNA and role of miRNA-targeted tumor suppressor genes as molecular markers of and possible targets for developing oncomiR-targeted therapy of chronic hepatitis and HCC. This article is part of a Special Issue entitled: MicroRNAs in viral gene regulation.     

The natural course of chronic hepatitis C

Abstract: In 1988, investigators from the Chiron Company (USA) detected the non-A, non-B agent and named it hepatitis C virus (HCV). An anti-HCV antibody assay (ELISA) and subsequently confirmation tests (immunoblot and polymerase chain reaction) were developed. HCV exposure results in a chronic infection in a majority of cases. This chronic infection is associated with slowly progressive chronic liver disease. Chronic HCV infection is, like HBV, also associated with the development of hepatocellular carcinoma. Most HCV carriers are infected by parenteral routes. Intravenous drug users have the highest risk of becoming infected. Intrafamiliar spread is seen in certain parts of the world but sexual and perinatal transmission does not play an important role in spreading the infection. Antiviral therapy (alpha-interferon) in patients with chronic hepatitis C will normalize liver function tests in about 25% of the cases.     

Small rodent models of hepatitis B and C virus replication and pathogenesis

The narrow host range of infection supporting the long-term propagation of hepatitis B and C viruses is a major limitation that has prevented a more thorough understanding of persistent infection and t...     

Viral interference: A potential therapeutic method for chronic viral hepatitis?

Viral interference exists between different viral hepatitis. Acute Hepatitis C virus (HCV) super-infection on Hepatitis B virus (HBV) chronic carriers showed an inhibition of the HBV genome. And acute HBV super-infection on HCV chronic carriers indicated a similar interaction. In these cases, if the acute liver viral super-infection presents a self-limited course, the patients may be free from both viral infections or at least with undetectable underlying chronic viremia. The mechanism of viral interference is still undefined. Anyway this still leads to the hypothesis of using one hepatitis virus (live attenuated vaccine) to treat another hepatitis virus.     

Serum cytokine levels as putative prognostic markers in the progression of chronic HCV hepatitis to cirrhosis

Hepatitis C virus (HCV) infection can present as an acute manifestation, and can lead to severe complications such as chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). It represents a global health problem because there is no vaccine currently available. Cytokines play an important role in viral clearance, infection control, inflammation, regeneration and fibrosis, and also are implicated in the pathological processes occurring in the liver during viral infection. Immunological markers of chronic HCV hepatitis progression as compared to cirrhosis and HCC would be extremely useful, particularly for distinguishing between the molecules produced during HCV-induced chronic inflammation and those secreted during cirrhosis and HCC. In this work, we evaluated the serum levels of several cytokines, chemokines and growth factors in 30 patients affected by chronic HCV (HC), 30 patients affected by HCV-related cirrhosis (LC) and 20 healthy, control subjects. We used a multiplex biometric ELISA-based immunoassay in order to identify molecules that might be useful for monitoring the progression of HCV to liver cirrhosis and, possibly, to cancer. Our results show that some pro-inflammatory molecules are significantly up-regulated, and play a role as immunological markers in the intermediate steps towards liver cancer, and that hepatocyte growth factor (HGF) is a specific marker of liver cirrhosis. Finally, these data will be used to define a cytokinome profile, which might prove useful for studies involving the transition of chronic inflammation to neoplastic processes.     

Molecular aspects of hepatitis B viral infection and the viral carcinogenesis

Of many viral causes of human cancer, few are of greater global importance than the hepatitis B virus (HBV). Over 250 million people worldwide are persistently infected with HBV. A significant minority of these develop severe pathologic consequences, including chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). Earlier epidemiological evidence suggested a link between chronic HBV infection and HCC. Further, the existence of related animal viruses that induce acute and chronic infections of the liver, and eventually HCC, confirms the concept that HBV belongs to one of the few human oncogenic viruses. Although it is clear that chronic HBV infections are major risk factors, relatively little is understood about how the viral factors contribute to hepatocarcinogenesis. This review will introduce molecular aspects of the viral infection, and highlight recent findings on the viral contribution to hepatocarcinogenesis.     

HBV基因型、基本核心启动子区双突变和肝细胞癌发生及临床病理特征的关系

目的探讨乙型肝炎病毒(HBV)基因型、基本核心启动子(BCP)区双突变(简称BCP双突变)和肝硬化(LC)、肝细胞癌(HCC)发生的关联,分析BCP双突变和HCC临床病理特征的关系。方法随机收集233例慢性HBV感染者的血清,其中80例为慢性乙型肝炎(CHB)患者、75例为LC患者、78例为HCC患者,并系统整理患者的常规检查和病理等资料。采用实时荧光定量聚合酶链反应(FQ-PCR)检测BCP双突,用特异性引物多重PCR扩增确定HBV基因型。用SPSS 11.0分析结果。结果 HBV基因型结果均为B和C型,分别在CHB和LC组,CHB和HCC组间分布差异有统计学意义(P<0.05),在LC和HCC组间分布差异无统计学意义(P>0.05),感染C基因型与LC和HCC发生相关(分别OR=2.73,95%CI=1.29～5.82;OR=2.00,95%CI=0.98～4.09)。BCP双突变也分别在CHB和LC组,CHB和HCC组间分布差异有统计学意义(P<0.05),在LC和HCC组间分布差异无统计学意义(P>0.05),双突变与LC和HCC发生相关(分别OR=1.91,95%CI=0.96～3.82;OR=2.05,95%CI=1.04～4.06)。BCP双突变和伴肝硬化的HCC相关(P<0.05)。结论感染HBV C基因型、BCP双突变可能均是LC和HCC发生的危险因素,BCP双突变可作为LC和HCC早期预警生物标记物。     

Natural history and treatment of hepatitis B virus and hepatitis C virus coinfection

Hepatitis B virus (HBV) and hepatitis C virus (HCV) coinfection is not uncommon as a result of similar routes of infection. Patients who are coinfected represent a unique group with diverse serologic profiles. Combined chronic hepatitis B and C leads to more severe liver disease and an increased risk of hepatocellular carcinoma. Furthermore, coinfected patients represent a treatment challenge. No standard recommendations exist for treatment of viral hepatitis due to dual HBV/HCV infection, and therefore treatment must be individualized based on patient variables such as serologic and virologic profiles, patient's prior exposure to antiviral treatment, and the presence of other parenterally transmitted viruses such as hepatitis D virus and human immunodeficiency virus. The natural history and treatment of patients with HBV and HCV coinfection is reviewed.     

A distinct repertoire of autoantibodies in hepatocellular carcinoma identified by proteomic analysis

Chronic infections with hepatitis B (HBV) and hepatitis C (HCV) viruses are major risk factors for hepatocellular carcinoma (HCC). We have utilized a proteomic approach to determine whether a distinct repertoire of autoantibodies can be identified in HCC. Sera from 37 patients with HCC and 31 subjects chronically infected with HBV or HCV without HCC were investigated. Sera from 116 patients with other cancers, three patients with systemic lupus erythematosus, and 24 healthy subjects were utilized as controls. We report the identification of eight proteins, for each of which autoantibodies were detected in sera from more than 10% of patients with HCC but not in sera from healthy individuals (p < 0.05). Autoantibodies to four of these proteins were detected at a comparable frequency in sera from patients with chronic hepatitis. The other four proteins, which consisted of calreticulin isoforms, cytokeratin 8, nucleoside diphosphate kinase A, and F(1)-ATP synthase beta-subunit, induced autoantibodies among patients with HCC, independently of their HBV/HCV status. Calreticulin, and a novel truncated form of calreticulin (Crt32) we have identified, most commonly elicited autoantibodies among patients with HCC (27%). We conclude that a distinct repertoire of autoantibodies is associated with HCC that may have utility in early diagnosis of HCC among high risk subjects with chronic hepatitis.     

Hepatitis vaccines: recent advances

Despite the availability of hepatitis A vaccines that might provide protection for decades, hepatitis B vaccines that provides protection for at least 15 years and the recent introduction of a combined hepatitis A and B vaccine, these infections continue to spread in both the developed and developing world. Hepatitis A vaccine coverage has been limited to high-risk groups: such a selective immunisation policy is unlikely to have a major impact. If adequate immunogenicity in infants is confirmed, dosing schedules can be improved and the costs of vaccination reduced, universal paediatric immunisation with combined hepatitis A and B products is likely to result in the eventual eradication of these infections. In the interim, novel hepatitis A vaccines are being investigated and additional studies on hepatitis A vaccine immunogenicity in infants are in progress. Worldwide use of hepatitis B vaccines for the newborn, young children and high-risk groups should control this infection and obviate the need for a vaccine against hepatitis D. Newer hepatitis B vaccines that may reduce the likelihood of non-responsiveness and have immunotherapeutic value are under study. A recombinant hepatitis E vaccine for use in endemic regions is currently in clinical trials. The development of an effective hepatitis C vaccine has been agonisingly slow and many impediments have been recognised. These include the lack of a susceptible small animal, a high degree of hepatitis C virus (HCV) genomic diversity and failure to produce high quantities of HCV in tissue culture. The development of a novel HCV replicon system may be a major breakthrough. Nonetheless, it may still be exceedingly difficult to produce a vaccine that uniformly provides sterilising immunity; the possibility of developing a hepatitis C vaccine that can prevent chronic infection is an exciting concept that requires further investigation. Advances in recombinant technology, the use of novel genetic (DNA-based) vaccines, expression of hepatitis antigens in plants and improved adjuvants also hold considerable promise.     

Hepatitis B viral factors and clinical outcomes of chronic hepatitis B

Hepatitis B virus (HBV) infection is an important health problem and the major cause of chronic hepatitis, cirrhosis as well as hepatocellular carcinoma (HCC) worldwide. The natural history of chronic HBV infection can be divided into 4 dynamic phases in HBV carriers who acquire the virus early in life. In general, the frequency and severity of hepatitis flares in the immune clearance or reactivation phase predict disease progression in HBV carriers, and early HBeAg seroconversion typically confers a favorable outcome. In contrast, late or absent HBeAg seroconversion after multiple hepatitis flares accelerates the progression of chronic hepatitis to cirrhosis. Recently, several hepatitis B viral factors predictive of clinical outcomes have been identified. For example, serum HBV DNA level at enrollment is the best predictor of adverse outcomes (cirrhosis, HCC and death from liver disease) in adults with chronic HBV infection. In addition, HBV genotype C, basal core promoter (BCP) mutant and pre-S deletion mutant are associated with increased risk of HCC development. In conclusion, hepatitis B viral factors such as serum HBV DNA level, genotype and mutants have already been clarified to influence disease progression of chronic hepatitis B. Further studies are needed to investigate the pathogenic mechanism of each viral factor.     

Hepatitis viruses and hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is among the most frequent malignancies worldwide. Hepatitis viruses, such as the hepatitis B virus (HBV) and hepatitis C virus (HCV) are undoubtedly listed in the etiology of HCC. Studies show that, in the near future, viral hepatitis will carry increasing weight in the etiology of HCC. This review briefly discusses the known carcinogenic effects of HBV and HCV in the light of experimental and human studies. The data show that viral proteins may directly interfere with gene products responsible for cell proliferation and cell growth. Many other signal transduction cascades may be affected as well. Direct integration of HBV viral sequences into the host genome increases the genomic instability. The genomic imbalance allows the development and survival of malignant clones bearing defected genomic information. HBV and HCV infection induces indirect and direct mechanisms through cellular damage, increased regeneration and cell proliferation, therefore enhancing the development of HCC.