Pathogenic mechanisms in HBV- and HCV-associated hepatocellular carcinoma

Identification of genomic alterations in oesophageal squamous cell cancer

Oesophageal cancer is one of the most aggressive cancers and is the sixth leading cause of cancer death worldwide. Approximately 70% of global oesophageal cancer cases occur in China, with oesophageal squamous cell carcinoma (ESCC) being the histopathological form in the vast majority of cases (>90%). Currently, there are limited clinical approaches for the early diagnosis and treatment of ESCC, resulting in a 10% five-year survival rate for patients. However, the full repertoire of genomic events leading to the pathogenesis of ESCC remains unclear. Here we describe a comprehensive genomic analysis of 158 ESCC cases, as part of the International Cancer Genome Consortium research project. We conducted whole-genome sequencing in 17 ESCC cases and whole-exome sequencing in 71 cases, of which 53 cases, plus an additional 70 ESCC cases not used in the whole-genome and whole-exome sequencing, were subjected to array comparative genomic hybridization analysis. We identified eight significantly mutated genes, of which six are well known tumour-associated genes (TP53, RB1, CDKN2A, PIK3CA, NOTCH1, NFE2L2), and two have not previously been described in ESCC (ADAM29 and FAM135B). Notably, FAM135B is identified as a novel cancer-implicated gene as assayed for its ability to promote malignancy of ESCC cells. Additionally, MIR548K, a microRNA encoded in the amplified 11q13.3-13.4 region, is characterized as a novel oncogene, and functional assays demonstrate that MIR548K enhances malignant phenotypes of ESCC cells. Moreover, we have found that several important histone regulator genes (MLL2 (also called KMT2D), ASH1L, MLL3 (KMT2C), SETD1B, CREBBP and EP300) are frequently altered in ESCC. Pathway assessment reveals that somatic aberrations are mainly involved in the Wnt, cell cycle and Notch pathways. Genomic analyses suggest that ESCC and head and neck squamous cell carcinoma share some common pathogenic mechanisms, and ESCC development is associated with alcohol drinking. This study has explored novel biological markers and tumorigenic pathways that would greatly improve therapeutic strategies for ESCC.

Managing hepatitis B to prevent liver cancer: recent advances

Chronic hepatitis B (CHB) infection is a major cause of human mortality worldwide. The majority of people with CHB are infected early in life, and 20-40% of men and 15% of women with chronic infection will develop hepatocellular carcinoma (HCC). Antiviral therapy is recommended for patients with CHB who have cirrhosis or active disease with the aims of reducing disease progression to cirrhosis, liver failure and liver cancer, thereby preventing death. Evidence that treatment with interferon or with early nucleos(t)ide analogue therapy reduces HCC has been somewhat conflicting, however evidence is emerging to support a significant role in HCC prevention of the more effective antivirals, entecavir and tenofovir. Older patients, those with cirrhosis, and those undergoing curative treatments for HCC derive the greatest medium-term benefit in terms of HCC reduction, but HCC can still occur and long-term surveillance is recommended.

Reversible phospho-Smad3 signalling between tumour suppression and fibrocarcinogenesis in chronic hepatitis B infection

Transforming growth factor (TGF)-β, type I receptor (TβRI) and c-Jun N-terminal kinases (JNK) phosphorylate Smad3 differentially to create 2 isoforms phosphorylated (p) at the COOH-terminus (C) or at the linker region (L) and regulate hepatocytic fibrocarcinogenesis. This study aimed to compare the differences between how hepatitis B virus (HBV) infection affected hepatocytic Smad3 phosphorylated isoforms before and after anti-viral therapy. To clarify the relationship between Smad3 phosphorylation and liver disease progression, we studied 10 random patients in each stage of HBV-related fibrotic liver disease (F1-4) and also 10 patients with HBV-associated HCC. To examine changes in phosphorylated Smad3 signalling before and after anti-HBV therapies, we chose 27 patients with chronic hepatitis B who underwent baseline and follow-up biopsies at 52 weeks from the start of nucleoside analogue treatments (Lamivudine 100 mg daily or Telbivudine 600 mg daily). Fibrosis stage, inflammatory activity and phosphorylated Smad3 positivity in the paired biopsy samples were compared. Hepatocytic pSmad3C signalling shifted to fibrocarcinogenic pSmad3L signalling as the livers progressed from chronic hepatitis B infection to HCC. After nucleoside analogue treatment, serum alanine aminotransferase (ALT) and HBV-DNA levels in 27 patients with HBV-related chronic liver diseases were decreased dramatically. Decrease in HBV-DNA restored pSmad3C signalling in hepatocytes, while eliminating prior fibrocarcinogenic pSmad3L signalling. Oral nucleoside analogue therapies can suppress fibrosis and reduce HCC incidence by successfully reversing phosphorylated Smad3 signalling; even liver disease progressed to cirrhosis in chronic hepatitis B patients.

High expression of beta2-glycoprotein I is associated significantly with the earliest stages of hepatitis B virus infection

Human beta2-glycoprotein I (beta2-GPI) binds to recombinant hepatitis B surface antigen (rHBsAg) and can bind specifically to annexin II, which is located on the cell membrane of human hepatoma SMMC-7721 cells. Viral envelope proteins are essential for mediating cellular entry. The aim of this study was to investigate the role of beta2-GPI in the early stages of hepatitis B virus (HBV) infection. Western blot and qRT-PCR analyses revealed that beta2-GPI expression was upregulated in HepG2.2.15 cells at both the mRNA and protein level and was almost non-existent in 293T and CHO cells. Furthermore, annexin II was expressed at lower levels in HepG2.2.15 cells compared to L02, HepG2, and SMMC-7721 cells. Additionally, ELISA analyses demonstrated that beta2-GPI enhanced the ability of HBsAg to bind to cell surfaces, and there was differential adhesion to L02, HepG2, HepG2.2.15, and 293T cells. Western blot and ELISA were then performed to assess the effects of HBV and the HBsAg domain on beta2-GPI expression in co-transfected 293T cells. This study revealed that HBV and the large HBV envelope protein increased beta2-GPI expression. Further investigation indicated that beta2-GPI colocalized with HBsAg in the cytosol of HepG2.2.15 cells, with sodium taurocholate co-transporting polypeptide (NTCP) on the cell membrane in NTCP-complemented HepG2 cells, and with annexin II in the cytosol of HepG2 and HepG2.2.15 cells. These data suggest that high expression of beta2-GPI enhances HBsAg binding to cell surfaces, thus contributing to virus particle transfer to the NTCP receptor and interaction with annexin II for viral membrane fusion.

Methylation-associated silencing of microRNA-34b in hepatocellular carcinoma cancer

MicroRNAs (miRNAs) can act as oncogenes or tumor-suppressor genes in human cancers including HCC. Previous studies have identified miR-34 family as an important component of the tumor suppressor network during carcinogenesis. In this study, we investigated the methylation status of miR-34 family in HCC tumor and adjacent non-tumor tissues using methylation-specific PCR (MSP). The methylation frequencies of miR-34a and miR-34b/c were 72.1% (31/43) and 79.1% (34/43) in HCC tissues, which were significantly higher than that in the adjacent non-tumor tissues (P < 0.05), respectively. The results were validated by bisulfite sequencing PCR (BSP). Quantitative reverse transcription polymerase chain reaction (RT-PCR) analysis showed that the expression of miR-34a and miR-34b was significantly down-regulated in HCC tissues compared with adjacent non-tumor tissues (P < 0.05). Moreover, the expression of miR-34b was inversely correlated to CpG island methylation in tumor tissues, but not for miR-34a. In summary, our results suggest that DNA methylation may be involved in the inactivation of miR-34b in HCC.

Hypoxia-inducible factor 1 and its role in viral carcinogenesis

The advent of modern molecular biology has allowed for the discovery of several mechanisms by which oncoviruses promote carcinogenesis. Remarkably, nearly all human oncogenic viruses increase levels of the transcription factor hypoxia-inducible factor 1 (HIF-1). In this review, we highlight HIF-1׳s significance in viral oncogenesis, while providing an in-depth analysis of its activation mechanisms by the following oncoviruses: human papillomaviruses (HPVs), hepatitis B/C viruses (HBV/HCVs), Epstein-Barr virus (EBV), Kaposi׳s sarcoma-associated herpes virus (KSHV), and human T-cell lymphotropic virus (HTLV-1). We discuss virus-induced HIF-1׳s role in transcriptional upregulation of metabolic, angiogenic, and microenvironmental factors that are integral for oncogenesis. Admittedly, conclusive evidence is lacking as to whether activation of HIF-1 target genes is necessary for malignant transformation or merely a result thereof. In addition, a complete understanding of host-virus interactions, the effect of viral genomic variation, and the clinical (and potential therapeutic) relevance of HIF-1 in viral oncogenesis warrant further investigation.

Understanding the interaction of hepatitis C virus with host DEAD-box RNA helicases

The current therapeutic regimen to combat chronic hepatitis C is not optimal due to substantial side effects and the failure of a significant proportion of patients to achieve a sustained virological response. Recently developed direct-acting antivirals targeting hepatitis C virus (HCV) enzymes reportedly increase the virologic response to therapy but may lead to a selection of drug-resistant variants. Besides direct-acting antivirals, another promising class of HCV drugs in development include host targeting agents that are responsible for interfering with the host factors crucial for the viral life cycle. A family of host proteins known as DEAD-box RNA helicases, characterized by nine conserved motifs, is known to play an important role in RNA metabolism. Several members of this family such as DDX3, DDX5 and DDX6 have been shown to play a role in HCV replication and this review will summarize our current knowledge on their interaction with HCV. As chronic hepatitis C is one of the leading causes of hepatocellular carcinoma, the involvement of DEAD-box RNA helicases in the development of HCC will also be highlighted. Continuing research on the interaction of host DEAD-box proteins with HCV and the contribution to viral replication and pathogenesis could be the panacea for the development of novel therapeutics against HCV.

Hepatitis B virus infection and immunopathogenesis in a humanized mouse model: induction of human-specific liver fibrosis and M2-like macrophages

The mechanisms of chronic HBV infection and immunopathogenesis are poorly understood due to a lack of a robust small animal model. Here we report the development of a humanized mouse model with both human immune system and human liver cells by reconstituting the immunodeficient A2/NSG (NOD.Cg-Prkdc(scid) Il2rg(tm1Wjl)/SzJ mice with human HLA-A2 transgene) with human hematopoietic stem cells and liver progenitor cells (A2/NSG-hu HSC/Hep mice). The A2/NSG-hu HSC/Hep mouse supported HBV infection and approximately 75% of HBV infected mice established persistent infection for at least 4 months. We detected human immune responses, albeit impaired in the liver, chronic liver inflammation and liver fibrosis in infected animals. An HBV neutralizing antibody efficiently inhibited HBV infection and associated liver diseases in humanized mice. In addition, we found that the HBV mediated liver disease was associated with high level of infiltrated human macrophages with M2-like activation phenotype. Importantly, similar M2-like macrophage accumulation was confirmed in chronic hepatitis B patients with liver diseases. Furthermore, gene expression analysis showed that induction of M2-like macrophage in the liver is associated with accelerated liver fibrosis and necrosis in patients with acute HBV-induced liver failure. Lastly, we demonstrate that HBV promotes M2-like activation in both M1 and M2 macrophages in cell culture studies. Our study demonstrates that the A2/NSG-hu HSC/Hep mouse model is valuable in studying HBV infection, human immune responses and associated liver diseases. Furthermore, results from this study suggest a critical role for macrophage polarization in hepatitis B virus-induced immune impairment and liver pathology.

The role of chemokines in hepatitis C virus-mediated liver disease

The hepatitis C virus (HCV) is a global health problem affecting more than 170 million people. A chronic HCV infection is associated with liver fibrosis, liver cirrhosis and hepatocellular carcinoma. To enable viral persistence, HCV has developed mechanisms to modulate both innate and adaptive immunity. The recruitment of antiviral immune cells in the liver is mainly dependent on the release of specific chemokines. Thus, the modulation of their expression could represent an efficient viral escape mechanism to hamper specific immune cell migration to the liver during the acute phase of the infection. HCV-mediated changes in hepatic immune cell chemotaxis during the chronic phase of the infection are significantly affecting antiviral immunity and tissue damage and thus influence survival of both the host and the virus. This review summarizes our current understanding of the HCV-mediated modulation of chemokine expression and of its impact on the development of liver disease. A profound knowledge of the strategies used by HCV to interfere with the host's immune response and the pro-fibrotic and pro-carcinogenic activities of HCV is essential to be able to design effective immunotherapies against HCV and HCV-mediated liver diseases.

Role of RASSF1A promoter methylation in the pathogenesis of hepatocellular carcinoma: a meta-analysis of 21 cohort studies

We carried out the current meta-analysis aiming to comprehensively assess the potential role of RASSF1A aberrant promoter methylation in the pathogenesis of hepatocellular carcinoma (HCC). A range of electronic databases were searched: Web of Science (1945-2013), the Cochrane Library Database (Issue 12, 2013), PubMed (1966-2013), EMBASE (1980-2013), CINAHL (1982-2013) and the Chinese Biomedical Database (CBM) (1982-2013) without language restrictions. Meta-analysis was conducted using the STATA 12.0 software. Crude risk difference (RD) with their 95% confidence interval (95% CI) was calculated. In the present meta-analysis, 21 clinical cohort studies with a total of 1,205 HCC patients were included. The results of our meta-analysis illustrated that the frequency of RASSF1A promoter methylation in cancer tissues were significantly higher than those of normal, adjacent and benign tissues (cancer tissues vs. normal tissues: RD = 0.63, 95% CI 0.53-0.73, P < 0.001; cancer tissues vs. adjacent tissues: RD = 0.43, 95% CI 0.33-0.53, P < 0.001; cancer tissues vs. benign tissues: RD = 0.48, 95% CI 038-0.58, P < 0.001; respectively). Further subgroup by ethnicity demonstrated that RASSF1A aberrant promoter methylation was correlated with the pathogenesis of HCC among both Asians and Caucasians (all P < 0.05). The current meta-analysis suggests that RASSF1A aberrant promoter methylation may be implicated in the pathogenesis of HCC. Thus, detection of RASSF1A promoter methylation may be a helpful and valuable biomarker for diagnosis and prognosis of HCC.

Abnormal expression of insulin-like growth factor-I receptor in hepatoma tissue and its inhibition to promote apoptosis of tumor cells

Abnormal signaling of insulin-like growth factor I receptor (IGF-IR) is associated with hepatocellular carcinoma, but the underlying molecular mechanisms remain largely unknown. The objective of this study was to investigate IGF-IR's role as a signaling molecule, its pathological alteration in hepatoma tissues, and its effect on hepatoma cell proliferation when inhibited. As measured by immunohistochemical analysis, the incidence of hepatic IGF-IR expression in cancerous tissue was 80.0 % (24 of 30), which was significantly higher (P < 0.05) than 43.3 % (13 of 30) occurrence in the surrounding tissue and the nondetectable (0 of 30) frequency in the distal cancerous tissue. Hepatoma IGF-IR expression was correlated to the differentiation degree and not to the number or size of tumors, HBV infection, and AFP level. The in vitro IGF-IR expression in hepatoma cells was down-regulated significantly by picropodophyllin, a specific kinase inhibitor, in a time- and dose-dependent manner. Cell proliferation was inhibited through typical mechanisms of promoting apoptosis and cell cycle arrest (G2/M phase). Up-regulation of IGF-IR in hepatocarcinogenesis suggests that the down-regulation of IGF-IR expression could be a specific molecular target for hepatoma cell proliferation.

CD81-receptor associations--impact for hepatitis C virus entry and antiviral therapies

Tetraspanins are integral transmembrane proteins organized in microdomains displaying specific and direct interactions with other tetraspanins and molecular partners. Among them, CD81 has been implicated in a variety of physiological and pathological processes. CD81 also plays a crucial role in pathogen entry into host cells, including hepatitis C virus (HCV) entry into hepatocytes. HCV is a major cause of liver cirrhosis and hepatocellular carcinoma. HCV entry into hepatocytes is a complex process that requires the coordinated interaction of viral and host factors for the initiation of infection, including CD81, scavenger receptor BI, claudin-1, occludin, membrane-bound host cell kinases, Niemann-Pick C1 Like 1, Harvey rat sarcoma viral oncogene homolog (HRas), CD63 and transferrin receptor 1. Furthermore, recent data in HCV model systems have demonstrated that targeting critical components of tetraspanins and associated cell membrane proteins open new avenues to prevent and treat viral infection.

Hepatitis C virus genotype 1b increases cumulative lifetime risk of hepatocellular carcinoma

The association between subtypes of hepatitis C virus (HCV) and risk of hepatocellular carcinoma (HCC) remained inconclusive and evaluated in both case-control and cohort studies. In the case-control study, 397 HCC cases from medical centers were compared with 410 community-based non-HCC controls. All of them were anti-HCV-seropositive, HBsAg-seronegative with serum HCV RNA levels ≥1,000 IU/mL. Logistic regression models were used to estimate the odds ratio (OR) with 95% confidence interval (95% CI) of HCV subtype after controlling for other HCC risk factors. In the cohort study, 866 anti-HCV-seropositive individuals were followed from 1991 to 2008 to assess the long-term HCC predictability of HCV subtypes. Newly developed HCC cases were ascertained by follow-up health examinations and computerized linkage with national databases. The percentage of HCV 1b subtype was higher among HCC cases than controls (64 vs. 55%, p < 0.001). Participant infected with HCV 1b had a higher mean serum HCV RNA level (2.0 × 10(6) IU/mL) than those infected with HCV non-1b (1.2 × 10(6) IU/mL, p < 0.001). The multivariate-adjusted OR (95% CI) of developing HCC for HCV 1b comparing to non-1b was 1.43 (1.02-2.02). After the long-term follow-up, the cumulative lifetime (30-80 years old) HCC risk was 19.2 and 29.7% for patients infected with HCV non-1b and 1b, respectively (p < 0.001). The multivariate-adjusted hazard ratio (95% CI) was 1.85 (1.06-3.22) for HCV 1b compared to non-1b. HCV subtype 1b, the most prevalent subtype in Taiwan, was associated with an increased HCC risk and a proactive clinical management is suggested for patients with HCV 1b.

Using multiple cytokines to predict hepatocellular carcinoma recurrence in two patient cohorts

BACKGROUND

Cytokines are tightly linked to the carcinogenesis, development and prognosis of hepatocellular carcinoma (HCC). We determined the prognostic value of 39 circulating cytokines in HCC patients after radical resection and then developed a novel cytokine-based prognostic classifier (CBPC) for the prediction of patient prognosis.

METHODS

A total of 179 patients were divided into two cohorts based on the date of radical resection. Thirty-nine cytokines were simultaneously analysed in patient serum samples using multiplex bead-based Luminex technology. Support vector machine-based methods and Cox proportional hazard models were used to develop a CBPC from the training cohort, which was then validated in the validation cohort.

RESULTS

Among seven cytokines significantly correlating with the disease-free survival (DFS) in the training cohort, six of them were validated to be significant prognostic factors to predict DFS and overall survival (OS) in the validation cohort, namely fibroblast growth factor 2 (FGF-2), growth-regulated oncogene (GRO), interleukin 8 (IL-8), interferon gamma-induced protein 10 (IP-10), vascular endothelial growth factor (VEGF), and interferon alpha-2 (IFN-α2). By integrating six cytokines and three clinical characteristics, we developed a CBPC to predict the recurrence and 3-year OS of HCC patients (sensitivity, 0.648; specificity, 0.918). In the validation cohort, the CBPC were confirmed to have significant predictive power for predicting tumour recurrence and OS (sensitivity, 0.585; specificity, 0.857). Interestingly, IFN-α2 was the only cytokine being independent prognostic factor in both patient cohorts.

CONCLUSION

Our study verifies the presence of specific cytokine-phenotype associations with patient prognosis in HCC. The CBPC developed include multiple circulating cytokines and may serve as a novel screening approach for identifying HCC patients with a high risk of post-resection recurrence and shorter OS. These individuals may also be suitable for cytokine-targeted therapies.

IFI16 mis-localization can be a contributing factor to hepatocellular carcinoma progression

Hepatocellular carcinoma (HCC) is a highly deadly cancer, with usually drug resistance. However the mechanisms responsible for this phenomenon are poorly understood. Interferon-γ inducible protein 16 (IFI16), a multifunctional protein, has roles in anti-proliferation, autophagy, cell senescence, anti-inflammation, and DNA sensor to trigger innate immunity. IFI16 physiologically absents in adult healthy hepatocyte, but exists in liver cancer cells. Interestingly, increasing evidences suggest that dysregulation or/and loss of IFI16 function have a critical role in drug resistance and tumor progression. Furthermore, interaction with DNA or other protein depends on IFI16 localization. In our study, to our knowledge, we first showed that IFI16 is a chromatin-binding protein in four HCC cell lines with different TP53 genotype, but not in fetal liver cell line, L02 cells. However, the function of IFI16 subcellular localization has not been determined in HCC. Therefore, we present our study and theoretical basis and presume that chromatin-bounding localization of IFI16 is associated with HCC progression. If we are able to acetylate or/and delete NLS of IFI16 with activated-p53 restoration, we may offer an alternative for HCC therapy.

Comparison of characteristics and transarterial chemoembolization outcomes in patients with unresectable hepatocellular carcinoma and different viral etiologies

PURPOSE

To determine any differences in patient characteristics and outcomes after transarterial chemoembolization between different viral etiologies of hepatocellular carcinoma (HCC).

METHODS

This retrospective study consisted of 201 patients undergoing first-time transarterial chemoembolization for unresectable HCC from January to December 2009. The patients were divided into four groups: hepatitis B virus (HBV) only (n = 104), hepatitis C virus (HCV) only (n = 63), HBV and HCV (n = 10), and no viral hepatitis (n = 24). The clinical and laboratory data were obtained from electronic medical records, and imaging findings obtained before transarterial chemoembolization were analyzed. Kaplan-Meier analyses were used to assess the impact of HBV or HCV status, clinical characteristics, and imaging results on overall survival.

RESULTS

After a median follow-up of 28.3 months ± 16.2, the 1-, 2-, and 3-year overall survival rates were 74.1%, 59.7%, and 53.2%. Patients with HBV had a significant association with younger age (P = .001), higher male-to-female ratio (P = .003), lower alanine aminotransferase levels (P = .018), higher albumin levels (P = .009), and multifocal tumors at diagnosis (P = .04) compared with patients with HCV. Patients with both HBV and HCV had significantly higher serum bilirubin levels compared with the other groups (P = .002). No significant difference was found in overall survival among the different hepatitis groups (P = .943). Multivariate analysis showed that statistically significant determinants for overall survival were Child-Pugh class (P = .002), Barcelona Clinic Liver Cancer stage (P < .001), tumor size (P < .001), and distribution (P < .001).

CONCLUSIONS

Viral etiology has no correlation with the outcome of patients with HCC undergoing transarterial chemoembolization.

Virus associated malignancies: the role of viral hepatitis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading fatal cancer worldwide and its incidence continues to increase. Chronic viral hepatitis involving either hepatitis B virus (HBV) or hepatitis C virus (HCV) infection is the leading etiology for HCC, making HCC prevention a major goal of antiviral therapy. While recent clinical observations and translational research have enhanced our understanding of the molecular mechanisms driving the initiation and progression of HCC, much remains unknown. Current data indicates that HCC tumors are highly complex and heterogeneous resulting from the aberrant function of multiple molecular pathways. This complex biology is responsible, at least in part, for the absence of highly efficient target-directed therapies for this deadly cancer. Additionally, the direct or indirect effect of HBV and HCV infection on the development of HCC is still a contentious issue. Thus, the question remains whether viral hepatitis-associated HCC stems from virus-specific factors, and/or from a general mechanism involving inflammation and tissue regeneration. In this review we summarize general mechanisms implicated in HCC, emphasizing data generated by new technologies available today. We also highlight specific pathways by which HBV and HCV could be involved in HCC pathogenesis. However, improvements to current in vitro and in vivo systems for both viruses will be needed to rigorously define the temporal sequence and specific pathway dysregulations that drive the strong clinical link between chronic hepatitis virus infection and HCC.

Molecular mechanisms of hepatic apoptosis

Apoptosis is a prominent feature of liver diseases. Causative factors such as alcohol, viruses, toxic bile acids, fatty acids, drugs, and immune response, can induce apoptotic cell death via membrane receptors and intracellular stress. Apoptotic signaling network, including membrane death receptor-mediated cascade, reactive oxygen species (ROS) generation, endoplasmic reticulum (ER) stress, lysosomal permeabilization, and mitochondrial dysfunction, is intermixed each other, but one mechanism may dominate at a particular stage. Mechanisms of hepatic apoptosis are complicated by multiple signaling pathways. The progression of liver disease is affected by the balance between apoptotic and antiapoptotic capabilities. Therapeutic options of liver injury are impacted by the clear understanding toward mechanisms of hepatic apoptosis.

Molecular mechanisms of hepatic apoptosis

Apoptosis is a prominent feature of liver diseases. Causative factors such as alcohol, viruses, toxic bile acids, fatty acids, drugs, and immune response, can induce apoptotic cell death via membrane receptors and intracellular stress. Apoptotic signaling network, including membrane death receptor-mediated cascade, reactive oxygen species (ROS) generation, endoplasmic reticulum (ER) stress, lysosomal permeabilization, and mitochondrial dysfunction, is intermixed each other, but one mechanism may dominate at a particular stage. Mechanisms of hepatic apoptosis are complicated by multiple signaling pathways. The progression of liver disease is affected by the balance between apoptotic and antiapoptotic capabilities. Therapeutic options of liver injury are impacted by the clear understanding toward mechanisms of hepatic apoptosis.

The Complex Relationship between Liver Cancer and the Cell Cycle: A Story of Multiple Regulations

The liver acts as a hub for metabolic reactions to keep a homeostatic balance during development and growth. The process of liver cancer development, although poorly understood, is related to different etiologic factors like toxins, alcohol, or viral infection. At the molecular level, liver cancer is characterized by a disruption of cell cycle regulation through many molecular mechanisms. In this review, we focus on the mechanisms underlying the lack of regulation of the cell cycle during liver cancer, focusing mainly on hepatocellular carcinoma (HCC). We also provide a brief summary of novel therapies connected to cell cycle regulation.

Overexpression of the transcription factor MEF2D in hepatocellular carcinoma sustains malignant character by suppressing G2-M transition genes

The underlying molecular pathogenesis in hepatocellular carcinoma remains poorly understood. The transcription factor MEF2D promotes survival in various cell types and it seems to function as an oncogene in leukemia. However, its potential contributions to solid cancers have not been explored. In this study, we investigated MEF2D expression and function in hepatocellular carcinoma, finding that MEF2D elevation in hepatocellular carcinoma clinical specimens was associated with poor prognosis. MEF2D-positive primary hepatocellular carcinoma cells displayed a faster proliferation rate compared with MEF2D-negative cells, and silencing or promoting MEF2D expression in these settings limited or accelerated cell proliferation, respectively. Notably, MEF2D-silencing abolished hepatocellular carcinoma tumorigenicity in mouse xenograft models. Mechanistic investigations revealed that MEF2D-silencing triggered G2-M arrest in a manner associated with direct downregulation of the cell-cycle regulatory genes RPRM, GADD45A, GADD45B, and CDKN1A. Furthermore, we identified MEF2D as an authentic target of miR-122, the reduced expression of which in hepatocellular carcinoma may be responsible for MEF2D upregulation. Together, our results identify MEF2D as a candidate oncogene in hepatocellular carcinoma and a potential target for hepatocellular carcinoma therapy.

Hepatic fibrosis and the microenvironment: fertile soil for hepatocellular carcinoma development

Hepatocellular carcinoma is an emerging worldwide health threat that has few curative treatment options and poor overall survival. Progressive hepatic fibrosis is a common pathway for all forms of chronic liver disease and is closely linked epidemiologically to hepatocellular carcinoma risk. However, the molecular events that predispose a fibrotic liver to cancer development remain elusive. Nonetheless, a permissive hepatic microenvironment provides fertile soil for transition of damaged hepatocytes into hepatocellular carcinoma. Key predisposing features include alterations in the extracellular matrix, bidirectional signaling pathways between parenchymal and nonparenchymal cells, and immune dysfunction. Emerging research into the contributions of autophagy, tumor-associated fibroblasts, and hepatocellular carcinoma progenitor cells to this dangerous milieu also provides new mechanistic underpinnings to explain the contribution of fibrosis to cancer. As effective antifibrotic therapies are developed, these approaches could attenuate the rising surge of hepatocellular carcinoma associated with chronic liver disease.

Chemopreventive strategies in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third most common cause of death from cancer. The incidence and mortality of HCC are increasing in most Western countries as a result of an ageing cohort infected with chronic hepatitis C, and are expected to continue to rise as a consequence of the obesity epidemic. Chemopreventive strategies aimed at decreasing the risk or delaying the onset of HCC are needed. Universal immunization against HBV and antiviral therapy against HBV and HCV in patients with established disease has consistently been associated with reduced HCC risk, especially in patients who achieve sustained virologic response. However, the cost-effectiveness of antiviral therapy for primary HCC prevention is not known. Several commonly prescribed medications seem promising as chemopreventive agents against HCC, including statins, antidiabetic medications and aspirin. Dietary agents such as coffee, vitamin E and fish oil as well as phytochemicals might also be associated with reduced risk of HCC. Though randomized controlled trials are ideally needed to firmly establish efficacy, such chemoprevention trials are logistically and ethically challenging. Well-designed, prospective, population-based cohort studies might provide the best evidence for chemopreventive efficacy of these agents.

Exploitation of host clock gene machinery by hepatitis viruses B and C

Many aspects of cellular physiology display circadian (approximately 24-h) rhythms. Dysfunction of the circadian clock molecular circuitry is associated with human health derangements, including neurodegeneration, increased risk of cancer, cardiovascular diseases and the metabolic syndrome. Viruses triggering hepatitis depend tightly on the host cell synthesis machinery for their own replication, survival and spreading. Recent evidences support a link between the circadian clock circuitry and viruses’ biological cycle within host cells. Currently, in vitro models for chronobiological studies of cells infected with viruses need to be implemented. The establishment of such in vitro models would be helpful to better understand the link between the clock gene machinery and viral replication/viral persistence in order to develop specifically targeted therapeutic regimens. Here we review the recent literature dealing with the interplay between hepatitis B and C viruses and clock genes.

Hepatocellular carcinoma in chronic hepatitis B patients under antiviral therapy

Patients with chronic hepatitis B are at increased risk of hepatocellular carcinoma (HCC), while the inhibition of viral replication can represent a reasonable target for HCC prevention. Interferon-α therapy results in decreased HCC risk, which is more evident in patients with high baseline HCC risk. The majority of chronic hepatitis B patients are treated with a nucleos(t)ide analogue (NA) for several reasons including the non-sustained response after interferon-α. The effect of the first licensed and low genetic barrier NA, lamivudine, on HCC incidence, has been repeatedly evaluated. Lamivudine, compared to no treatment, reduces the HCC incidence, which may increase again in cases with lamivudine resistance. Emerging data with the currently first-line NAs, entecavir and tenofovir, suggest that they also reduce the HCC incidence. The treatment benefit in reduction of the HCC incidence is always greater in patients with high baseline HCC risk, particularly cirrhotics, and without virological remission under entecavir/tenofovir. However, the HCC risk is not eliminated even in the vast majority of patients who remain in virological remission under entecavir/tenofovir. Therefore, patients at increased baseline HCC risk should continue to undergo HCC surveillance even if they have achieved complete long-term inhibition of viral replication and improvements in liver histology.

Ablation therapy for hepatocellular carcinoma: past, present and future perspectives

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death worldwide, and is most commonly found in the setting of liver cirrhosis. Treatment of HCC must consider both the tumors present, as well as the remaining dysfunctional liver that both hinders treatment and can produce additional HCC over time. Ablation is an evolving part of the multimodality treatment approach to HCC that can effectively destroy tumors while preserving surrounding liver parenchyma. New technologies have made ablation an indispensable tool in the treatment of all stages of HCC. This review presents the history, present technologies and future potential of ablation in the treatment of HCC.

Immunity, inflammation and cancer: a leading role for adenosine

Cancer is a complex disease that is dictated by both cancer cell-intrinsic and cell-extrinsic processes. Adenosine is an ancient extracellular signalling molecule that can regulate almost all aspects of tissue function. As such, several studies have recently highlighted a crucial role for adenosine signalling in regulating the various aspects of cell-intrinsic and cell-extrinsic processes of cancer development. This Review critically discusses the role of adenosine and its receptors in regulating the complex interplay among immune, inflammatory, endothelial and cancer cells during the course of neoplastic disease.

Using proteomics to identify the HBx interactome in hepatitis B virus: how can this inform the clinic?

Hepatitis B virus (HBV) is a small and enveloped DNA virus, of which chronic infection is the main risk factor of liver cirrhosis and hepatocellular carcinoma. Hepatitis B virus X protein (HBx) is a multifunctional protein encoded by HBV genome, which have significant effects on HBV replication and pathogenesis. Through directly interacting with cellular proteins, HBx is capable to promote HBV replication, regulate transcription of host genes, disrupt protein degradation, modulate signaling pathway, manipulate cell death and deregulate cell cycle. In this review, we briefly discuss the diversified effects of HBx-interactome and their potential clinical significances.

Is the oxidative DNA damage level of human lymphocyte correlated with the antioxidant capacity of serum or the base excision repair activity of lymphocyte?

A random screening of human blood samples from 24 individuals of nonsmoker was conducted to examine the correlation between the oxidative DNA damage level of lymphocytes and the antioxidant capacity of serum or the base excision repair (BER) activity of lymphocytes. The oxidative DNA damage level was measured with comet assay containing Fpg/Endo III cleavage, and the BER activity was estimated with a modified comet assay including nuclear extract of lymphocytes for enzymatic cleavage. Antioxidant capacity was determined with trolox equivalent antioxidant capacity assay. We found that though the endogenous DNA oxidation levels varied among the individuals, each individual level appeared to be steady for at least 1 month. Our results indicate that the oxidative DNA damage level is insignificantly or weakly correlated with antioxidant capacity or BER activity, respectively. However, lymphocytes from carriers of Helicobacter pylori (HP) or Hepatitis B virus (HBV) tend to give higher levels of oxidative DNA damage (P < 0.05). Though sera of this group of individuals show no particular tendency with reduced antioxidant capacity, the respective BER activities of lymphocytes are lower in average (P < 0.05). Thus, reduction of repair activity may be associated with the genotoxic effect of HP or HBV infection.

Synergistic function of Kras mutation and HBx in initiation and progression of hepatocellular carcinoma in mice

Although the activation of Ras pathway is frequently observed in human hepatocellular carcinoma (HCC), the in vivo role of Ras activation in HCC initiation and progression is underdetermined. To test the consequence of Kras activation in hepatocyte, we generated a hepatocyte-specific Kras(G12D) transgenic mouse strain and observed spontaneous development of HCC in these mice. Remarkably, HBV X protein (HBx) expression significantly promotes the formation and malignant progression of Kras(G12D)-driven HCC as shown with the accelerated tumor onset, the increased tumor burden and the more poorly differentiated lesions. At the cellular level, concomitant expression of Kras(G12D) and HBx results in a robust increase in hepatocellular proliferation. We reveal that the Akt, MAPK, p53 and TGF-β pathways are deregulated in the Kras(G12D)-driven HCCs. Also, the dysregulation is more pronounced in the HCCs developed in Kras(G12D) and HBx double transgenic mice. In addition, the altered expressions of β-catenin, CD44 and E-cadherin are only observed in the Kras(G12D) and HBx double transgenic mice. These results demonstrate a crucial role of Ras activation in hepatocellular carcinogenesis and the functional synergy between Kras(G12D) and HBx in HCC initiation and progression. The novel genetic mouse models that closely recapitulate the histopathologic progression and molecular alterations of human HCC may potentially facilitate the future therapeutic studies.

Emerging role of high-mobility group box 1 (HMGB1) in liver diseases

Damage-associated molecular pattern (DAMP) molecules are essential for the initiation of innate inflammatory responses to infection and injury. The prototypic DAMP molecule, high-mobility group box 1 (HMGB1), is an abundant architectural chromosomal protein that has location-specific biological functions: within the nucleus as a DNA chaperone, within the cytosol to sustain autophagy and outside the cell as a DAMP molecule. Recent research indicates that aberrant activation of HMGB1 signaling can promote the onset of inflammatory and autoimmune diseases, raising interest in the development of therapeutic strategies to control their function. The importance of HMGB1 activation in various forms of liver disease in relation to liver damage, steatosis, inflammation, fibrosis, tumorigenesis and regeneration is discussed in this review.

Genetic variability of hepatitis B and C viruses in Brazilian patients with and without hepatocellular carcinoma

Most cases of hepatocellular carcinoma (HCC) are due to chronic hepatitis B virus (HBV) or hepatitis C virus (HCV) infection worldwide. The aim of this study was to determine the viral genotypes and frequency of 17 mutations (15 for HBV and 2 for HCV), described previously as able to influence the course of chronic liver disease, in patients with and without HCC. This transversal study included 157 Brazilian patients with chronic hepatitis B (n = 51) and C (n = 106). Of these, 12 and 40 patients had HBV- and HCV-related HCC, respectively. Nucleotide sequencing of core promoter, pre-core, and pre-S/S regions of HBV and core region of HCV strains was performed to determine their genotypes and the frequency of the respective mutations. Among the HBV isolates, subgenotype A1 was the most prevalent in both patients with (90%) and without (61%) HCC. Fourteen out of the 15 mutations under study, as well as five different pre-S deletions, were identified. Core promoter T1753V, A1762T, and G1764A mutations were more frequent in patients with HCC than in those without, although with no statistical difference. However, a significant correlation was observed between T1753V mutation and elevation of transaminases levels (P < 0.05). As for HCV, mutation at residue 70 in the core protein of genotype 1b strains was significantly more frequent in patients with cirrhosis (56.3%) than in those without (9.1%) (P = 0.018). The detection of some key mutations in the genomes of HBV and HCV might be helpful to predict the clinical outcome of patients with chronic liver disease.

Replication of genome wide association studies on hepatocellular carcinoma susceptibility loci in a Chinese population

Background

Genome-wide association studies (GWAS) have identified three loci (rs17401966 in KIF1B, rs7574865 in STAT4, rs9275319 in HLA-DQ) as being associated with hepatitis B virus-related hepatocellular carcinoma (HBV-related HCC) in a Chinese population, two loci (rs2596542 in MICA, rs9275572 located between HLA-DQA and HLA-DQB) with hepatitis C virus-related HCC (HCV-related HCC) in a Japanese population. In the present study, we sought to determine whether these SNPs are predictive for HBV-related HCC development in other Chinese population as well.

Method and Findings

We genotyped 4 SNPs, rs2596542, rs9275572, rs17401966, rs7574865, in 506 HBV-related HCC patients and 772 chronic hepatitis B (CHB) patients in Han Chinese by TaqMan methods. Odds ratio(OR)and 95% confidence interval (CI) were calculated by logistic regression. In our case-control study, significant association between rs9275572 and HCC were observed (P = 0.02, OR = 0.73, 95% CI = 0.56–0.95). In the further haplotype analysis between rs2596542 at 6p21.33 and rs9275572 at 6p21.3, G-A showed a protective effect on HBV-related HCC occurrence (P<0.001, OR = 0.66, 95% CI = 0.52–0.84).

Conclusion

These findings provided convincing evidence that rs9275572 significantly associated with HBV-related HCC.

Substrate cleavage profiling suggests a distinct function of Bacteroides fragilis metalloproteinases (fragilysin and metalloproteinase II) at the microbiome-inflammation-cancer interface

Enterotoxigenic anaerobic Bacteroides fragilis is a significant source of inflammatory diarrheal disease and a risk factor for colorectal cancer. Two distinct metalloproteinase types (the homologous 1, 2, and 3 isoforms of fragilysin (FRA1, FRA2, and FRA3, respectively) and metalloproteinase II (MPII)) are encoded by the B. fragilis pathogenicity island. FRA was demonstrated to be important to pathogenesis, whereas MPII, also a potential virulence protein, remained completely uncharacterized. Here, we, for the first time, extensively characterized MPII in comparison with FRA3, a representative of the FRA isoforms. We employed a series of multiplexed peptide cleavage assays to determine substrate specificity and proteolytic characteristics of MPII and FRA. These results enabled implementation of an efficient assay of MPII activity using a fluorescence-quenched peptide and contributed to structural evidence for the distinct substrate cleavage preferences of MPII and FRA. Our data imply that MPII specificity mimics the dibasic Arg↓Arg cleavage motif of furin-like proprotein convertases, whereas the cleavage motif of FRA (Pro-X-X-Leu-(Arg/Ala/Leu)↓) resembles that of human matrix metalloproteinases. To the best of our knowledge, MPII is the first zinc metalloproteinase with the dibasic cleavage preferences, suggesting a high level of versatility of metalloproteinase proteolysis. Based on these data, we now suggest that the combined (rather than individual) activity of MPII and FRA is required for the overall B. fragilis virulence in vivo.

Circulating miRNA profile in HCV infected serum: novel insight into pathogenesis

Changes in circulating miRNA profiles have been associated with different diseases. Here we demonstrate the circulating miRNA profile in serum of HCV infected individuals using a microRNA array that profiles the expression of 940 miRNAs. Serum samples from two HCV genotype - 1 and two HCV genotype - 3 infected individuals were compared with healthy controls. Expression levels of miR-134, miR-198, miR-320c and miR-483-5p that were commonly upregulated in case of both genotypes were validated in 36 individual patient serum samples. Serum miR-134, miR-320c and miR-483-5p were significantly upregulated during HCV infection. miR-320c and miR-483-5p were also upregulated in HCV- JFH1 infected cells and cell culture supernatant. Pathway analysis of putative target genes of these miRNAs indicated involvement of PI3K-Akt, NFKB and MAPK signaling pathways. Results revealed novel insights on the role of circulating miRNAs in mediating pathogenesis in HCV-infected cells.

Association of 5-methylcytosine and 5-hydroxymethylcytosine with mitochondrial DNA content and clinical and biochemical parameters in hepatocellular carcinoma

Increasing epidemiological evidence has indicated that inherited variations of mitochondrial DNA (mtDNA) copy number affect the genetic susceptibility of many malignancies in a tumour-specific manner and that DNA methylation also plays an important role in controlling gene expression during the differentiation and development of hepatocellular carcinoma (HCC). Our previous study demonstrated that HCC tissues showed a lower 5-hydroxymethylcytosine (5-hmC) content when compared to tumour-adjacent tissues, but the relationship among 5-hmC, 5-methylcytosine (5-mC) and mtDNA content in HCC patients is still unknown. This study aimed to clarify the correlation among mtDNA content, 5-mC and 5-hmC by quantitative real-time PCR and liquid chromatography tandem mass spectrometry analysis. We demonstrated that 5-hmC correlated with tumour size [odds ratio (OR) 0.847, 95% confidence interval (CI) 0.746–0.962, P = 0.011], and HCC patients with a tumour size ≥5.0 cm showed a lower 5-hmC content and higher levels of fasting plasma aspartate aminotransferase, the ratio of alanine amiotransferase to aspartate aminotransferase, γ-glutamyltransferase, alpha-fetoprotein than those with a tumour size <5 cm (all P<0.05). We further revealed that the mtDNA content of HCC tumour tissues was 225.97(105.42, 430.54) [median (25th Percentile, 75th Percentile)] and was negatively correlated with 5-mC content (P = 0.035), but not 5-hmC content, in genomic DNA from HCC tumour tissues.

Associations of miR-499 and miR-34b/c Polymorphisms with Susceptibility to Hepatocellular Carcinoma: An Evidence-Based Evaluation

Background. Hepatocellular carcinoma (HCC) represents the sixth common cancer in the world. Single nucleotide polymorphisms (SNPs) in microRNA genes may be associated with susceptibility to HCC. Recently, several studies have reported possible associations of SNPs miR-499 T>C rs3746444 and miR-34b/c T>C rs4938723 with the risk of HCC. However the results are inconsistent and inconclusive. In this present study, we conducted a meta-analysis to comprehensively evaluate potential associations between the two SNPs and HCC susceptibility. Methods. Through a systematic literature search, 8-case-control studies involving 5464 subjects were identified and included in this meta-analysis. The association between the two common SNPs and HCC risk was estimated by pooled odds ratios (ORs) and 95% confidence intervals (95% CIs). Our results showed no significant association between rs3746444 and susceptibility to HCC, whereas variant genotypes of rs4938723 were associated with increased HCC risk in allele frequency model and heterozygous model (C versus T, OR = 1.11, 95% CI: 1.01-1.23, P = 0.04; TC versus TT, OR = 1.19, 95% CI: 1.03-1.37, P = 0.02). Conclusions. The current evidence did not support association between rs3746444 and HCC risk. SNP rs4938723 may be associated with susceptibility to HCC. Further well-designed studies are required to clarify the relationships between the two SNPs and HCC risk.

COX-2-765G>C polymorphism increases the risk of cancer: a meta-analysis

Background

Chronic inflammation has been regarded as an important mechanism in carcinogenesis. Inflammation-associated genetic variants have been highly associated with cancer risk. Polymorphisms in the gene cyclooxygenase-2 (COX-2), a pro-inflammation factor, have been suggested to alter the risk of multiple tumors, but the findings of various studies are not consistent.

Methods

A literature search through February 2013 was performed using PubMed, EMBASE, and CNKI databases. We used odds ratios (ORs) with confidence intervals (CIs) of 95% to assess the strength of the association between the COX-2-765G>C polymorphism and cancer risk in a random-effect model. We also assessed heterogeneity and publication bias.

Results

In total, 65 articles with 29,487 cancer cases and 39,212 non-cancer controls were included in this meta-analysis. The pooled OR (95% CIs) in the co-dominant model (GC vs. GG) was 1.11 (1.02–1.22), and in the dominant model ((CC+GC) vs. GG), the pooled OR was 1.12 (1.02–1.23). In the subgroup analysis, stratified by cancer type and race, significant associations were found between the-765 C allele and higher risk for gastric cancer, leukemia, pancreatic cancer, and cancer in the Asian population.

Conclusion

In summary, the COX-2-765 C allele was related to increased cancer susceptibility, especially gastric cancer and cancer in the Asian population.

Role of hepatitis B virus X protein in hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world and the third most common cause of cancer-related death. Chronic hepatitis B virus (HBV) infection has been identified as a major risk factor for HCC. Evidence suggests that the HBV X protein (HBx) plays a crucial role in the carcinogenesis of HCC. HBx is a multifunctional regulator that plays a key role in the occurrence, development, invasion and metastasis of cancers. Due to its important roles in the development of HCC, the research on the HBx protein has become a hot topic in recent years. This review describes the latest advances in understanding the role of the HBx protein in hepatocarcinogenesis.

Antiviral activities of Indonesian medicinal plants in the East Java region against hepatitis C virus

Background

Hepatitis C virus (HCV) is a major cause of liver disease and a potential cause of substantial morbidity and mortality worldwide. The overall prevalence of HCV infection is 2%, representing 120 million people worldwide. Current standard treatment using pegylated interferon and ribavirin is effective in only 50% of the patients infected with HCV genotype 1, and is associated with significant side effects. Therefore, it is still of importance to develop new drugs for treatment of HCV. Antiviral substances obtained from natural products, including medicinal plants, are potentially good targets to study. In this study, we evaluated Indonesian medicinal plants for their anti-HCV activities.

Methods

Ethanol extracts of 21 samples derived from 17 species of medicinal plants explored in the East Java region were tested. Anti-HCV activities were determined by a cell culture method using Huh7.5 cells and HCV strains of 9 different genotypes (1a to 7a, 1b and 2b).

Results

Four of the 21 samples tested showed antiviral activities against HCV: Toona sureni leaves (TSL) with 50% inhibitory concentrations (IC₅₀) of 13.9 and 2.0 μg/ml against the HCV J6/JFH1-P47 and -P1 strains, respectively, Melicope latifolia leaves (MLL) with IC₅₀ of 3.5 and 2.1 μg/ml, respectively, Melanolepis multiglandulosa stem (MMS) with IC₅₀ of 17.1 and 6.2 μg/ml, respectively, and Ficus fistulosa leaves (FFL) with IC₅₀ of 15.0 and 5.7 μg/ml, respectively. Time-of-addition experiments revealed that TSL and MLL inhibited both at the entry and post-entry steps while MMS and FFL principally at the entry step. TSL and MLL inhibited all of 11 HCV strains of all the genotypes tested to the same extent. On the other hand, FFL showed significantly weaker inhibitory activities against the HCV genotype 1a strain, and MMS against the HCV strains of genotypes 2b and 7a to a lesser extent, compared to the other HCV genotypes.

Conclusions

Ethanol extracts of TSL, MLL, MMS and FFL showed antiviral activities against all the HCV genotypes tested with the exception that some genotype(s) showed significant resistance to FFL and to MMS to a lesser extent. These plant extracts may be good candidates for the development of anti-HCV drugs.

Virus induced inflammation and cancer development

Chronic inflammation as a result of viral infection significantly increases the likelihood of cancer development. A handful of diverse viruses have confirmed roles in cancer development and progression, but the list of suspected oncogenic viruses is continually growing. Viruses induce cancer directly and indirectly, by activating inflammatory signalling pathways and cytokines, stimulating growth of infected cells and inhibiting apoptosis. Although oncogenic viruses induce inflammation by various mechanisms, it is generally mediated by the MAPK, NFκB and STAT3 signalling pathways. This review will explore the unique mechanisms by which different oncogenic viruses induce inflammation to promote cancer initiation and progression.

Significant association between XRCC3 C241T polymorphism and increased risk of hepatocellular carcinoma: a meta-analysis

Many studies were published to examine the association between XRCC3 C241T polymorphism and hepatocellular carcinoma risk, but their results were inconsistent. To assess the association between XRCC3 C241T polymorphism and hepatocellular carcinoma risk more precisely, a meta-analysis was performed. PubMed, Embase and Wanfang databases were searched for relevant case-control studies. Data were extracted, and the pooled odds ratios (OR) with 95 % confidence intervals (95% CI) were calculated. Finally, seven studies comprising 2,288 cases with hepatocellular carcinoma and 3,249 controls were included into the meta-analysis. Overall, there was an obvious association between XRCC3 C241T polymorphism and increased risk of hepatocellular carcinoma (TT versus CC: OR = 3.31, 95% CI 1.52-7.19, P = 0.003; TT versus

CC/CT

OR = 3.31, 95% CI 1.81-6.06, P < 0.001). After adjusting for heterogeneity, there was still an obvious association between XRCC3 C241T polymorphism and increased risk of hepatocellular carcinoma (TT versus CC: OR = 1.92, 95 % CI 1.13-3.26, P = 0.016; TT versus

CC/CT

OR = 2.10, 95% CI 1.25-3.55, P = 0.005). Overall, there is a significant association between XRCC3 C241T polymorphism and increased risk of hepatocellular carcinoma. Further studies are needed to further assess the association in Caucasians.

Tying the knot between cytokine and toll-like receptor signaling in gastrointestinal tract cancers

Inflammation-associated malignancies of the gastrointestinal tract (GI), including those of the stomach and colon, collectively rank as the highest cause of cancer-related deaths worldwide. It has been well documented that the deregulated activation of the archetypal pro-inflammatory and oncogenic transcription factors nuclear factor-kappa B (NF-κB) and signal transducer and activator of transcription (STAT)3 is a common feature of GI cancers that invariably correlates with poor prognosis. Signal transducer and activator of transcription 3 and NF-κB are key downstream signal transducers of the interleukin (IL)-6 cytokine and toll-like receptor (TLR) families, respectively, and until recently, the potential involvement of these two families in the pathogenesis of cancer has been investigated in isolation. However, there is now emerging evidence of the complex interplay between the IL-6 cytokine and TLR families in GI tract cancers, with a surprising twist in the identification of a non-immune role for specific TLR family members. In this review, we discuss the molecular mechanisms associated with cross-talk between the IL-6 cytokine family/STAT3 signaling network and the TLR family/NF-κB signaling network, and we address the potential benefit of their therapeutic targeting in gastric and colorectal cancers.

Towards incorporating epigenetic mechanisms into carcinogen identification and evaluation

Remarkable progress in the field of epigenetics has turned academic, medical and public attention to the potential applications of these new advances in medicine and various fields of biomedical research. The result is a broader appreciation of epigenetic phenomena in the a etiology of common human diseases, most notably cancer. These advances also represent an exciting opportunity to incorporate epigenetics and epigenomics into carcinogen identification and safety assessment. Current epigenetic studies, including major international sequencing projects, are expected to generate information for establishing the 'normal' epigenome of tissues and cell types as well as the physiological variability of the epigenome against which carcinogen exposure can be assessed. Recently, epigenetic events have emerged as key mechanisms in cancer development, and while our search of the Monograph Volume 100 revealed that epigenetics have played a modest role in evaluating human carcinogens by the International Agency for Research on Cancer (IARC) Monographs so far, epigenetic data might play a pivotal role in the future. Here, we review (i) the current status of incorporation of epigenetics in carcinogen evaluation in the IARC Monographs Programme, (ii) potential modes of action for epigenetic carcinogens, (iii) current in vivo and in vitro technologies to detect epigenetic carcinogens, (iv) genomic regions and epigenetic modifications and their biological consequences and (v) critical technological and biological issues in assessment of epigenetic carcinogens. We also discuss the issues related to opportunities and challenges in the application of epigenetic testing in carcinogen identification and evaluation. Although the application of epigenetic assays in carcinogen evaluation is still in its infancy, important data are being generated and valuable scientific resources are being established that should catalyse future applications of epigenetic testing.