Hepatocellular carcinoma: an update.

Hepatocellular carcinoma (HCC) is the most common malignant tumor of males in the world, with an incidence of 1,000,000 new cases a year. It is endemic in Southeast Asia and Sub-Saharan Africa. Risk factors include chronic infection with hepatitis B virus (HBV) and hepatitis C virus (HCV), Aflatoxin B1 uptake, hemochromatosis, and alpha1 -antitripsin deficiency. Epidemiological studies provide evidence for the association of HCC with HBV infection. The incidence of HCC is high in regions hyperendemic for HBV. Chronic carrier state and maternal-infant transmission are important factors in the development of HCC. Evidence of direct oncogenic effect of H BV is well established, HCCs contain viral DNA sequences integrated into hepatocyte DNA that act as random insertional mutagens, and these sites are near genes involved in the control of proliferation and differentiation. The mechanism of hepatitis C virus in hepatocarcinogenesis is still imprecise but a high percentage of cases are related to this virus. Chronic alcohol consumption and cirrhosis are cofactors that increase the development of HCC in patients with chronic viral infection. In experimental carcinogenesis a multipotential element called oval cell proliferates in the early stages. The cellular events are accompanied by increased expression of several growth factors that enhance the survival of carcinogen-activated cells by suppressing apoptosis and increasing elements entering the cell cycle. Hepatic carcinogenesis is a complex process associated with accumulation of genetic and epigenetic changes that run through steps of initiation, promotion and progression. Activation of oncogenes of the "ras" family and others has been detected during chemically-induced HCC in rodents, but there is little evidence of such activation in human tumors. The role of tumor supressor genes such as retinoblastoma (RB) and P53 genes has been documented. Aflatoxin B1 that contaminates foods in endemic areas has a clear role in hepatocarcinogenesis. Metabolites of this toxin promote apurinic sites and G to T mutations in chromosomal DNA, the third base of codon 249 of the P53 gene is preferentially targeted to form aducts with aflatoxin B1, and this mutation has been specifically identified in HBV infection. Histological and cytological criteria for the diagnosis of HCC are well established and are based in architectural and cytological changes. An important issue is the diagnosis of liver "nodules" detected by image, from which small biopsies or aspiration material is obtained. Special studies such as reticulin, CD34, cytokeratin profile, and MOC-31 can be very useful for the differential diagnosis of primary and metastatic tumors. Telomerase activity has been found in HCC and negative in pericancerous tissue. It is more pronounced in poorly differentiated tumors and correlates with factors of clinical importance, such as prognosis and recurrences. Cells of well-differentiated HCC have an ultrastructural appearance similar to normal hepatocytes. During the process of dedifferentiation, there is progressive loss of organization of intracellular organelles. The cell cohesion is lost, intercellular gaps with microvilli appear, the sinusoids become capillarized, and reparative changes are seen in the spaces of Disse. A variety of inclusions, such as Mallory bodies, granular material, secondary lysosomes, and Dubin-Johnson pigment, have been described. Fibrolamellar carcinoma has a characteristic histological picture and ultrastructurally oncocytic features. Neuroendocrine granules and combination of HCC with bile duct carcinoma are seen by electron microscopy.     

Hepatitis B and C virus-related carcinogenesis

Chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) infection are the most important causes of hepatocellular carcinoma (HCC), accounting for the majority of the cases worldwide. The geographical distribution of HCC therefore coincides with the distribution of HBV and HCV infections in those areas. Similar to nonviral liver diseases, HBV and HCV infection can cause chronic injury to the liver, with subsequent progression to severe fibrosis and cirrhosis. The presence of cirrhosis is a major risk factor for the development of HCC. However, HCC can occur in the absence of cirrhosis, suggesting that both HBV and HCV may be directly involved in hepatocarcinogenesis. Several HBV factors have been implicated in hepatocarcinogenesis, including the HBx gene, the pre-S2/S gene and the HBV spliced protein. Furthermore, HBV can be integrated into the host genome, leading to changes in genomic function or chromosomal instability. By contrast to HBV, HCV cannot integrate into the host genome. Various HCV proteins, including the core, envelope and nonstructural proteins, have been shown to have oncogenic properties. For HBV infection, antiviral therapy and vaccination have been shown to decrease the risk of HCC. Antiviral therapy for HCV can also reduce the risk of HCC.     

Frequent detection of hepatitis B virus DNA in hepatocellular carcinoma of patients with sustained virologic response for hepatitis C virus

Hepatocellular carcinoma (HCC) develops several years after the eradication of hepatitis C virus (HCV) by interferon therapy. Risk factors for the development of HCC are only partly understood. To elucidate the role of occult hepatitis B virus (HBV) infection in hepatocarcinogenesis in patients with sustained virologic response, the prevalences of HBV‐related makers were examined. Study group comprised 16 patients with sustained virologic response (group A) and 50 with HCV (group B). Anti‐HBc and anti‐HBs in serum were examined by enzyme‐linked immunoassay. HBV DNA in liver was examined by nested polymerase chain reaction, using primers specific for genes encoding for HBx, HBsAg, HBcAg, and HBV cccDNA. Sequence of the amplified HBV DNA for ‘a’ determinant of HBsAg was determined in HCC. Anti‐HBc was positive in 10 of 16 in group A and 25 of 50 in group B. HBV DNA in liver was detected in 12 of 16 in group A and 21 of 50 in group B (P = 0.044). In group A, HBV DNA in liver was detected frequently in patients without cirrhosis and in those with a longer period from the time of HCV eradication to the development of HCC. Mutation in ‘a’ determinant of HBsAg was found in three HCC of group A. Occult HBV infection may be one of the most important risk factors in hepatocarcinogenesis of Japanese patients with sustained virologic response. J. Med. Virol. 81:1009–1014, 2009. © 2009 Wiley‐Liss, Inc.     

Hepatitis B virus infection and primary hepatocellular carcinoma.

For many years, epidemiological studies have demonstrated a strong link between chronic hepatitis B virus (HBV) infection and the development of primary hepatocellular carcinoma (PHC). Other hepatocarcinogens such as hepatitis C virus and aflatoxin also contribute to hepatocarcinogenesis either in conjunction with HBV infection or alone. Cellular and molecular biological studies are providing explanations for the HBV-PHC relationship, and models are now being formulated to further test the relative importance of various factors such as viral DNA integration, activation of oncogenes, genetic instability, loss of tumor suppressor genes, and trans-activating properties of HBV to the pathogenesis of PHC. Further research will probably define more than a single mechanism whereby chronic HBV infection results in PHC.     

Primary liver cancer and its relationship to chronic infection with the hepatitis B virus

Conclusions Chronic infection with the hepatitis B virus is etiologically related to the development of hepatocellular carcinoma, one of the most frequent cancers in several heavily populated areas of the world. Chronic infection with the HBV is extremely frequent among HCC patients and it may be true that more than three quarters of the world cases of HCC are positive for HBsAg. The clinical and laboratory features of HCC associated with chronic HBV infection appear to vary geographically. An attempt was made, however, to outline its main clinical aspects including possibilities in early diagnosis. Although cirrhosis is present in more than two thirds of HBsAg positive HCCs, it is usually compensated and even clinically latent, particularly in the high-incidence areas of HCC. HBsAg positive HCC can also arise as a result of chronic hepatitis, in only slightly fibrotic or even normal livers. The causal role of HBV in HCC has been discussed on the basis of existing evidence. Chronic HBV infection in conjunction with other factors may lead to the development of HCC by creating a continuous stimulus for regeneration and growth, by modifying the biotransformation system of hepatocytes, by initiating and promoting resistant dysplastic hepatocytes, and by transforming directly liver-cells to malignant ones after integration of the viral DNA into the host genome. Regardless of these speculations it is hoped that prevention of chronic HBV infection may significantly reduce, in the future, mortality from HCC.     

Persistence of intrahepatic hepatitis B virus DNA integration in patients developing hepatocellular carcinoma after hepatitis B surface antigen seroclearance

Background/AimsThe role of hepatitis B virus (HBV) integration into the host genome in hepatocarcinogenesis following hepatitis B surface antigen (HBsAg) seroclearance remains unknown. Our study aimed to investigate and characterize HBV integration events in chronic hepatitis B (CHB) patients who developed hepatocellular carcinoma (HCC) after HBsAg seroclearance.MethodsUsing probe-based HBV capturing followed by next-generation sequencing technology, HBV integration was examined in 10 samples (seven tumors and three non-tumor tissues) from seven chronic carriers who developed HCC after HBsAg loss. Genomic locations and patterns of HBV integration were investigated.ResultsHBV integration was observed in six patients (85.7%) and eight (80.0%) of 10 tested samples. HBV integration breakpoints were detected in all of the non-tumor (3/3, 100%) and five of the seven (71.4%) tumor samples, with an average number of breakpoints of 4.00 and 2.43, respectively. Despite the lower total number of tumoral integration breakpoints, HBV integration sites in the tumors were more enriched within the genic area. In contrast, non-tumor tissues more often showed intergenic integration. Regarding functions of the affected genes, tumoral genes with HBV integration were mostly associated with carcinogenesis. At enrollment, patients who did not remain under regular HCC surveillance after HBsAg seroclearance had a large HCC, while those on regular surveillance had a small HCC.ConclusionsThe biological functions of HBV integration are almost comparable between HBsAg-positive and HBsAg-serocleared HCCs, with continuing pro-oncogenic effects of HBV integration. Thus, ongoing HCC surveillance and clinical management should continue even after HBsAg seroclearance in patients with CHB.     

Hepatocellular carcinoma and schistosomiasis japonica. A clinicopathologic study of 59 autopsy cases of hepatocellular carcinoma associated with chronic schistosomiasis japonica

The association between hepatocellular carcinoma (HCC) and chronic hepatic schistosomiasis (CS) was studied by reviewing, 4,886 autopsies in adults during the past 20 years. In 229 cases of CS, 59 (25.7%) also had HCC. Among cases without CS, 399 (8.5%) had HCC. The incidence of HCC in patients with CS was significantly higher than that of other autopsy cases (p less than 0.01). Serum HBsAg was positive in 25.7% of 35 HCC cases with CS examined for hepatitis B virus (HBV) markers and anti HBs was positive in 10 of the 12 HBsAg-negative cases associated with CS, and in 62.1% of the other HBsAg-negative cases examined. Thus, most of HCC cases, including those associated with CS, probably had HBV infection at one time. Morphological examination revealed varying degrees of non-schistosomal hepatic changes, including macronodular or mixed macro-and micronodular cirrhosis, superimposed on schistosomal fibrosis in about two-thirds of the cases of HCC associated with CS. Although conclusive evidence whether or not schistosomal infection had a direct role in hepatocarcinogenesis could not be obtained, it was predicted that the additional non-schistosomal factors, particularly HBV infection, might play a synergistic role.     

NK cell receptor imbalance and NK cell dysfunction in HBV infection and hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is currently the third leading cause of cancer mortality and a common poor-prognosis malignancy due to postoperative recurrence and metastasis. There is a significant correlation between chronic hepatitis B virus (HBV) infection and hepatocarcinogenesis. As the first line of host defense against viral infections and tumors, natural killer (NK) cells express a large number of immune recognition receptors (NK receptors (NKRs)) to recognize ligands on hepatocytes, liver sinusoidal endothelial cells, stellate cells and Kupffer cells, which maintain the balance between immune response and immune tolerance of NK cells. Unfortunately, the percentage and absolute number of liver NK cells decrease significantly during the development and progression of HCC. The abnormal expression of NK cell receptors and dysfunction of liver NK cells contribute to the progression of chronic HBV infection and HCC and are significantly associated with poor prognosis for liver cancer. In this review, we focus on the role of NK cell receptors in anti-tumor immune responses in HCC, particularly HBV-related HCC. We discuss specifically how tumor cells evade attack from NK cells and how emerging understanding of NKRs may aid the development of novel treatments for HCC. Novel mono- and combination therapeutic strategies that target the NK cell receptor–ligand system may potentially lead to successful and effective immunotherapy in HCC.     

Hepadnaviruses in cirrhotic liver and hepatocellular carcinoma

Hepadnaviruses share properties of virion structure, genome structure and replication, epidemiologic behavior, and pathogenic effects, including an association with hepatocellular carcinoma (HCC). Epidemiologic evidence implicating hepadnavirus infection in HCC includes the observation that the geographic distributions of HBV infection and HCC are similar, that the incidence of HCC is much higher in hepadnavirus infected than uninfected hosts, and that viral DNA sequences are integrated in the cellular DNA of most (e.g., 80-90%) but not all hepadnavirus-associated HCC. Cirrhosis further increases the risk of HCC in HBV infected humans. The precise role of hepadnaviruses in development of most HCC is unclear, although the finding of viral integrations within or near protooncogenes in a few cases suggests the possibility that these integrations may play a direct role in these HCC. However, in the great majority of HCC associated with HBV infections, viral integrations are in different cellular DNA sites in different HCC, integrations are not within domains of known protooncogenes, and integrations are not found in some 10-15% hepadnavirus-associated HCC, suggesting that persisting viral sequences are not directly involved in the development of these HCC as viral sequences are for tumors caused by viruses with oncogenes or viruses that act by a "promoter-insertion" mechanism. It is possible, however, that oncogenic mutations could arise via other mutagenic mechanism that may operate in chronic hepatitis B and/or cirrhosis and which do not involve persisting viral integrations. For example, liver regeneration, which is a feature of the cirrhosis associated with chronic HBV infection (and sometimes with chronic hepatitis B) involves proliferation of many cells with HBV integrations, and such integrations have been shown to be unstable and may lead to mutations through post-integration rearrangements of cellular sequences at sites of viral integrations. Viral sequences appear to be lost or deleted at some such sites of rearranged cell DNA. Chronic HBV infection shares pathologic features of liver cell injury and reactive inflammation, liver regeneration, and in man sometimes cirrhosis with other important risk factors for HCC including chronic alcoholic liver disease, chronic non-A, non-B hepatitis, hemochromatosis, and crypogenic cirrhosis, suggesting that this common pathologic process may be carcinogenic by a mechanism that does not depend specifically on the factor which initiates liver cell injury. The pathogenetic role of chronic hepadnavirus infection in such a process would be in causing liver cell injury with reactive inflammation and hepatocyte proliferation (regeneration).(ABSTRACT TRUNCATED AT 400 WORDS)     

Hepatitis B virus antigens in liver resections from patients with hepatocellular carcinoma

A high rate of hepatitis B virus (HBV) antigen carriers among patients with hepatocellular carcinoma (HCC) has been recorded from areas of endemic HBV infections in Africa and Asia, but there are only rare and contradictory data for Europe. 12 specimens of resected liver tissue were immunohistologically investigated for hepatitis B surface antigen (HBsAg) as well as for hepatitis B core antigen (HBcAg). HBsAg was contained in non-tumorous liver tissue in 66 per cent of these cases. In two cases detection of HBcAg in the liver provided evidence to replication of the virus. HBcAg plus HBsAg were present in tumour tissue in one case. All of the HBV antigen carriers did not have chronic hepatitis. On the other hand, all patients with chronic hepatitis had HBV antigens in their liver tissue. HBV antigens were detectable in 7 non-cirrhotic livers, but were contained in only one of two cirrhotic livers. These results are likely to suggest a possible relevance of HBV infection to the aetiology of HCC even in central Europe without customary liver cirrhosis.     

Frequent integration of hepatitis B virus DNA in noncancerous liver tissue from hepatocellular carcinoma patients

To investigate the relationship between hepatocarcinogenesis and integration of hepatitis B virus (HBV) DNA in the cellular DNA of the liver, we studied the integration of HBV DNA in various noncancerous regions of the liver from 31 patients using Southern blot analysis. Of 13 patients without hepatocellular carcinoma (HCC), 4 had heterogeneously integrated HBV DNA. Of the latter four patients, two had chronic liver disease, and two had nonspecific histological changes. In contrast, integration of HBV DNA was found in noncancerous tissue from 11 of 18 patients with HCC. In eight patients, homogeneous integration was found in noncancerous tissue, and restriction fragments of integrated HBV DNA were different from those found in cancerous tissue. Moreover, integration of HBV DNA was found in all portions examined from the same liver, and homogeneously integrated HBV DNA showed different restriction patterns in different areas. These results suggest that integration of HBV DNA may occur in heterogeneous sites of cellular DNA before hepatocarcinogenesis. Subsequently, multi-focal clonal populations develop from these hepatocytes, especially frequently in the case of HCC. Integrated HBV DNA may play an important role in the clonal growth of hepatocytes, although the development of HCC requires additional factors.     

Hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC): Molecular mechanisms and novel paradigms

Chronic hepatitis B (HBV) infection is a major risk factor for hepatocellular carcinoma (HCC). Most HCCs complicate the evolution of an active or inactive cirrhosis. However, some tumors occur on livers with minimal histological changes; the prevalence of such cases varies from one geographical region to the other, being much higher in the Southern half of Africa (around 40% of HCCs) than in Asia, America and Europe, where at least 90% of HCCs are associated in the cirrhosis. This heterogeneity is probably a reflection of different environmental and genetic factors. This review will summarise the current knowledge on the mechanisms involved in HBV-related liver carcinogenesis. It will show in particular how viruses can be viewed as tools to discover and dissect new cellular pathways involved in cancer development and emphasize the potential synergistic effects between HBV and hepatitis C virus (HCV), as well as between viral infections and other environmental factors, such as alcohol.     

Epidemiology of chronic hepatitis B virus infection,hepatocellular carcinoma,and hepatitis B virus-induced hepatocellular carcinoma

Approximately 360 million people worldwide are chronically infected with hepatitis B virus (HBV) and are at high risk of developing hepatocellular carcinoma (HCC). Chronic HBV infection is the most prevalent cause of this tumour, accounting for 55% of global cases, and 89% of those in endemic regions for HBV infection. Relative risks for developing HCC in the presence of chronic HBV infection may be as high as 49 in case-control studies, and 98 in cohort studies. HCC is the sixth most common cancer in the world today, with approximately 630,000 new cases occurring each year. It ranks third in annual cancer mortality rates. Approximately 80% of HCCs occur in developing countries where HBV infection is endemic, with the highest incidences being in the Asia-Pacific region, and sub-Saharan Africa. In the chronic carriers of the virus who are at greatest risk of developing HCC, the infection is acquired at birth or in the early months or years of life, either perinatally or horizontally, and frequently becomes chronic. The risks are greater in males, and older individuals, and are increased by co-exposure to aflatoxin B₁, the presence of cirrhosis, obesity, or diabetes mellitus, and possibly co-infection with hepatitis C virus. Viral factors that influence the risk of HCC are high viral load, the presence of certain mutations, and genotypes. Although the incidence of chronic HBV infection is beginning to decrease as a result of the universal infant immunization programme, HBV-induced HCC incidence is projected to increase for at least another two decades.     

Hepatitis B virus (HBV) and hepatitis C virus (HCV) dual infection

Hepatitis B virus (HBV) and hepatitis C virus (HCV) infections account for a substantial proportion of liver diseases worldwide. Because the two hepatotropic viruses share same modes of transmission, coinfection with the two viruses is not uncommon, especially in areas with a high prevalence of HBV infection and among people at high risk for parenteral infection. Patients with dual HBV and HCV infection have more severe liver disease, and are at an increased risk for progression to hepatocellular carcinoma (HCC). Treatment of viral hepatitis due to dual HBV/HCV infection represents a challenge.     

Stimulation of Cellular Proliferation by Hepatitis B Virus X Protein

Chronic infection with the hepatitis B virus (HBV) is a known risk factor in the development of human hepatocellular carcinoma (HCC). The HBV-encoded X protein, HBx, has been investigated for properties that may explain its cancer cofactor role in transgenic mouse lines. We discuss here recent data showing that HBx is able to induce hepatocellular proliferation in vitro and in vivo. This property of HBx is predicted to sensitize hepatocytes to other HCC cofactors, including exposure to carcinogens and to other hepatitis viruses. Cellular proliferation is intimately linked to the mechanism(s) by which most tumor-associated viruses transform virus-infected cells. The HBx alteration of the cell cycle provides an additional mechanism by which chronic HBV infection may contribute to HCC.     

Impact of hepatitis B virus X protein on the DNA damage response during hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is one of the most prevalent and lethal cancers worldwide. The main HCC-associated diseases are chronic infections with hepatitis B virus (HBV) and hepatitis C virus (HCV), and HBV-associated HCC is still prevalent in Asia. Many studies have suggested that HBV X protein (HBX), which is the most common ORF integrated into the host genome, plays a crucial role in hepatocarcinogenesis. However, the accumulated evidence regarding HBX-mediated signaling pathways is not concordant, and it is difficult to understand the mechanistic nature of HBX-associated hepatocarcinogenesis. For example, HBX was reported to inactivate the early responses to DNA damage via p53-dependent and -independent pathways by interacting with several DNA damage-binding proteins and was also reported to sensitize cells to p53-mediated apoptosis via ataxia-telangiectasia and Rad3-related (ATR)-dependent signaling. HBX also interferes with the centrosome replication process, resulting in rearrangement of chromosomes with micronuclei. Moreover, HBX was found to sensitize protein kinases such as Ras/Raf/mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), stress-activated protein kinase/NH2-terminal-Jun kinase (SAPK/JNK), protein kinase B (PKB/Akt), and Janus kinase/STAT (JAK/STAT), indicating that a variety of signaling pathways may be activated by HBX. In this review, we focus on the roles of HBX in DNA damage repair during HCC development, with a view to achieving a better understanding of the significance of HBX in the early steps of hepatocarcinogenesis.     

Molecular and serological aspects of HBsAg-negative hepatitis B virus infections in North America

A few hepatitis B virus (HBV) infections are characterized by the presence of HBV DNA in serum or liver tissue, or both, in the absence of detectable hepatitis B surface antigen (HBsAg) in serum. However, such infections have rarely been described previously in North American patients. In the present study, 31 hepatocellular carcinoma (HCC) patients from the United States and Canada who had no detectable HBsAg in their serum were studied. In these 31 HBsAg-negative HCC patients, HBV DNA was detected in HCC and/or in adjacent nontumorous liver tissue using nested polymerase chain reaction (PCR) in 5/9 (56%) patients from the United States and in 12/22 (55%) from Canada. The 17 HBV DNA-positive/HBsAg-negative patients from the United States and Canada included 9 without any serological markers for HBV and 8 with detectable antibodies to hepatitis B core antigen. In these patients, HBV genotype C was the most prevalent genotype (11/17; 64%). HBV genotypes have not been previously reported in HCC patients from North America. Replicative intermediate forms of HBV (covalently closed circular HBV DNA) were detected in 2/17 (12%) HBV DNA-positive/HBsAg-negative patients, indicating that at least two of these patients had actively replicating HBV infections. The use of tests to detect HBV DNA permitted the identification of HBV infections in HBsAg-negative HCC patients from North America. Among these patients, those with antibody to hepatitis C virus (HCV) would otherwise have been designated "HCV-associated HCCs" based on serological tests alone. These findings provide a new perspective on determining the possible viral etiologies of HCCs in North America.