Hepatitis C virus core protein triggers hepatic angiogenesis by a mechanism including multiple pathways

Viruses exploit growth factor mechanisms to achieve augmented pathogenicity and promote tumorigenesis

Cellular homeostasis is regulated by growth factors (GFs) which orchestrate various cellular processes including proliferation, survival, differentiation, motility, inflammation and angiogenesis. Dysregulation of GFs in microbial infections and malignancies have been reported previously. Viral pathogens exemplify the exploitation of host cell GFs and their signalling pathways contributing to viral entry, virulence, and evasion of anti-viral immune responses. Viruses can also perturb cellular metabolism and the cell cycle by manipulation of GF signaling. In some cases, this disturbance may promote oncogenesis. Viral pathogens can encode viral GF homologues and induce the endogenous biosynthesis of GFs and their corresponding receptors or manipulate their activity to infect the host cells. Close investigation of how viral strategies exploit and regulate GFs, a will shed light on how to improve anti-viral therapy and cancer treatment. In this review, we discuss and provide insights on how various viral pathogens exploit different GFs to promote viral survival and oncogenic transformation, and how this knowledge can be leveraged toward the design of more efficient therapeutics or novel drug delivery systems in the treatment of both viral infections and malignancies.

HCV and HCC Tango-Deciphering the Intricate Dance of Disease: A Review Article

Hepatitis C virus (HCV) is a major cause of hepatocellular carcinoma (HCC) accounting for around one-third of all HCC cases. Prolonged inflammation in chronic hepatitis C (CHC), maintained through a variety of pro- and anti-inflammatory mediators, is one of the aspects of carcinogenesis, followed by mitochondrial dysfunction and oxidative stress. Immune response dysfunction including the innate and adaptive immunity also plays a role in the development, as well as in the recurrence of HCC after treatment. Some of the tumor suppressor genes inhibited by the HCV proteins are p53, p73, and retinoblastoma 1. Mutations in the telomerase reverse transcriptase promoter and the oncogene catenin beta 1 are two more important carcinogenic signaling pathways in HCC associated with HCV. Furthermore, in HCV-related HCC, numerous tumor suppressor and seven oncogenic genes are dysregulated by epigenetic changes. Epigenetic regulation of gene expression is considered as a lasting "epigenetic memory", suggesting that HCV-induced changes persist and are associated with liver carcinogenesis even after cure. Epigenetic changes and immune response dysfunction are recognized targets for potential therapy of HCC.

Pathogenesis of Hepatocellular Carcinoma: The Interplay of Apoptosis and Autophagy

The pathogenesis of hepatocellular carcinoma (HCC) is a multifactorial process that has not yet been fully investigated. Autophagy and apoptosis are two important cellular pathways that are critical for cell survival or death. The balance between apoptosis and autophagy regulates liver cell turnover and maintains intracellular homeostasis. However, the balance is often dysregulated in many cancers, including HCC. Autophagy and apoptosis pathways may be either independent or parallel or one may influence the other. Autophagy may either inhibit or promote apoptosis, thus regulating the fate of the liver cancer cells. In this review, a concise overview of the pathogenesis of HCC is presented, with emphasis on new developments, including the role of endoplasmic reticulum stress, the implication of microRNAs and the role of gut microbiota. The characteristics of HCC associated with a specific liver disease are also described and a brief description of autophagy and apoptosis is provided. The role of autophagy and apoptosis in the initiation, progress and metastatic potential is reviewed and the experimental evidence indicating an interplay between the two is extensively analyzed. The role of ferroptosis, a recently described specific pathway of regulated cell death, is presented. Finally, the potential therapeutic implications of autophagy and apoptosis in drug resistance are examined.

Mechanism of ASK1 involvement in liver diseases and related potential therapeutic targets: A critical pathway molecule worth investigating

Since the discovery of apoptosis signal-regulated kinase 1 (ASK1), the signal transduction mechanism and pathophysiological process involved in its regulation have been continuously revealed. Many previous studies have identified that ASK1 is involved and plays a critical role in the development of diseases affecting the nervous, cardiac, renal, and other systems. As a mitogen-activated protein kinase (MAPK) kinase kinase, ASK1 mediates apoptosis, necrosis, inflammation, and other pathological processes by activating its downstream c-Jun N-terminal kinase (JNK)/p38 MAPK. Owing to the important role of ASK1, an increasing number of studies in recent years have focused on its status in liver-related diseases. In this paper, we review the mechanisms and targets of ASK1 in liver-related diseases to emphasize its important role in the development of liver disease.

Nilotinib alleviated acetaminophen-induced acute hepatic injury in mice through inhibiting HIF-1alpha/VEGF-signaling pathway

The current study inspects the impact of nilotinib (Nil) on liver damage caused by acetaminophen (APAP). Adult male mice were pre-treated with nilotinib (Nil,5 and 10 mg/kg) orally once daily for 7 days followed by a single intraperitoneal administration of acetaminophen (APAP, 200 mg/kg) on the 7th day. The results indicated that nilotinib significantly decreased APAP-induced elevation of biochemical markers (ALT, AST, ALP, LDH, ɤ GT, and total bilirubin). Additionally, nilotinib significantly increased hepatic GSH and SOD content, while decreased MDA content. Nil significantly suppressed the expression of HIF-1α and VEGF. Histopathological examination of hepatic tissue from Nil-treated mice revealed that Nil reduced acetaminophen-induced necrosis.

Hepatitis C Virus Core Protein Promotes the Metastasis of Human Hepatocytes by Activating the MAPK/ERK/PEA3-SRF/c-Fos/MMPs Axis

BACKGROUND AND AIM

Previous studies have shown that the hepatitis C virus (HCV) core protein plays an important role in the metastasis of hepatocellular carcinoma (HCC) cells. This study aimed to identify the potential mechanism of HCV core protein in HCC.

METHODS

A transcription factor microarray analysis was performed to identify the factors regulated by the HCV core protein. A comprehensive bioinformatics analysis approach was utilized to predict the functions, regulatory signaling pathways and downstream target genes of the differentially regulated transcription factors. Dual-luciferase assays, qPCR, Western blotting, ERK pathway inhibition experiments and siRNA knockdown experiments were performed to verify the effects of the HCV core protein on PEA3, SRF and c-Fos, as well asthe underlying mechanism. The migration/invasion assay and scratch assay served to confirm the metastasis-promoting mechanism of the HCV core protein.

RESULTS

The results demonstrated that altered expression of PEA3, SRF and c-Fos mediated by the HCV core protein were associated with the MAPK/ERK pathway. c-Fos was a downstream target protein of PEA3 and SRF. Knockdown of PEA3-SRF/c-Fos expression and ERK pathway components suppressed the migration and invasion activity of hepatocytes by affecting MMP2 and MMP9 expression.

CONCLUSION

We provided preliminary evidence that the role of the HCV core protein in promoting metastasis is at least partially dependent on the activation of the MAPK/ERK/PEA3-SRF/c-Fos/MMP2/MMP9 axis. These findings reveal a novel mechanism by which the HCV core protein promotes HCC metastasis and may provide new therapeutic targets for patients with metastatic HCC.

Biomarkers for the Detection and Management of Hepatocellular Carcinoma in Patients Treated with Direct-Acting Antivirals

Simple Summary

Chronic Hepatitis C virus (HCV) represents the main etiological factor for hepatocellular carcinoma (HCC) in developed countries. The introduction of direct-acting antivirals (DAAs) improved the eradication of the hepatitis C virus (HCV) but not the reduction in the incidence of HCV-associated HCC. Some patients still develop HCC, even after reaching a sustained virological response (SVR). This review is a summary of pre-clinical studies that investigated predictive biomarkers for HCC occurrence and recurrence in HCV-infected patients treated with DAAs. The presented biomarkers are found dysregulated in serum or tissue at specific time points (before, during, after DAA treatment or post SVR) and correlated with HCC-predisposing conditions. Thus, this review aims to improve the management of patients developing HCV-induced HCC.

Abstract

Hepatocellular carcinoma (HCC) is the sixth-most common type of cancer worldwide and chronic Hepatitis C virus (HCV) represents the main etiological factor in developed countries. HCV promotes hepatocarcinogenesis through persistent liver inflammation and dysregulation of cell signaling pathways. The introduction of direct-acting antivirals (DAAs) resulted in a significant improvement in the eradication of the virus, with an expected reduction of HCC incidence. However, the risk of HCC development can persist after DAA treatment. Recent studies have investigated the potential use of molecular biomarkers that predict HCC occurrence or recurrence helping the stratification of patients under surveillance. This review aimed to summarize all pre-clinical exploration of predictive biomarkers to identify DAA-treated patients at risk for HCC development. Dysregulated microRNAs, lncRNAs, histone modifications, cytokines, proteins, and sphingolipids represent various classes of HCC risk predictors identified in two different biological sources (tissue and serum). The non-invasive serum markers can provide a more accessible means to perform clinical monitoring and predict the risk of HCC. In addition, conditions like cirrhosis, predisposing to HCC, strongly correlate with most of the molecular predictors identified, supporting the value of these molecules as possible biomarkers of HCC in DAA-treated patients.

Vitamin D and Hypoxia: Points of Interplay in Cancer

Vitamin D is a hormone that, through its action, elicits a broad spectrum of physiological responses ranging from classic to nonclassical actions such as bone morphogenesis and immune function. In parallel, many studies describe the antiproliferative, proapoptotic, antiangiogenic effects of calcitriol (the active hormonal form) that contribute to its anticancer activity. Additionally, epidemiological data signify the inverse correlation between vitamin D levels and cancer risk. On the contrary, tumors possess several adaptive mechanisms that enable them to evade the anticancer effects of calcitriol. Such maladaptive processes are often a characteristic of the cancer microenvironment, which in solid tumors is frequently hypoxic and elicits the overexpression of Hypoxia-Inducible Factors (HIFs). HIF-mediated signaling not only contributes to cancer cell survival and proliferation but also confers resistance to anticancer agents. Taking into consideration that calcitriol intertwines with signaling events elicited by the hypoxic status cells, this review examines their interplay in cellular signaling to give the opportunity to better understand their relationship in cancer development and their prospect for the treatment of cancer.

Anti-inflammatory and anti-fibrotic effects of modafinil in nonalcoholic liver disease

Small- and intermediate-conductance Ca²⁺-activated K⁺ channels, K_Ca2.3 and K_Ca3.1, are involved in cellular signaling processes associated with inflammation and fibrosis. K_Ca2.3 and K_Ca3.1 are upregulated by proinflammatory cytokines and profibrotic growth factors. Cyclic AMP, which downregulates K_Ca2.3 and K_Ca3.1, is elevated by modafinil in cells; accordingly, we investigated whether modafinil exerts anti-inflammatory and anti-fibrotic responses via K_Ca2.3- and K_Ca3.1-mediated pathways in high-fat diet (HFD)- or thioacetamide-induced liver disease models in mice. Modafinil was administered orally in the form of a racemate, (R)-isomer, or (S)-isomer. We also determined whether the treatment targeted the profibrotic activity of hepatic stellate cells using immortalized human hepatic stellate cells (LX-2 cells). Modafinil improved HFD- or thioacetamide-induced changes compared to the control, leading to a reduced inflammatory response, collagen deposition, and α-smooth muscle actin expression both in vivo and in vitro. However, modafinil did not relieve HFD-induced steatosis. There were no significant differences in the effects of the (R)- and (S)-isomers of modafinil. K_Ca2.3 and K_Ca3.1 were upregulated and catalase was downregulated in liver tissues from thioacetamide- or HFD-induced liver disease models or in TGF-β-treated LX-2 cells. TGF-β-induced upregulation of K_Ca2.3, K_Ca3.1, collagen, and α-smooth muscle actin and downregulation of catalase were reversed by modafinil, polyethylene glycol catalase, N-acetylcysteine, siRNA against K_Ca2.3 or K_Ca3.1, and Epac inhibitors. Our investigation revealed that modafinil attenuated inflammatory and fibrotic progression via K_Ca2.3- and K_Ca3.1-mediated pathways in nonalcoholic hepatitis, suggesting that inhibiting K_Ca2.3- and K_Ca3.1-mediated signaling may serve as a novel therapeutic approach for inflammatory and fibrotic liver diseases.

Liver fibrosis regression correlates with downregulation in liver angiogenesis in chronic hepatitis C through viral eradication

OBJECTIVES

The impact of viral eradication on hepatic angiogenesis is unknown. This study aimed to analyze the correlations of liver angiogenesis with liver fibrosis progression or regression in chronic hepatitis C (CHC) after viral eradication.

METHODS

From 2003 to 2020, a cohort of 130 eligible participants underwent paired percutaneous liver biopsies (median = 48 months apart; range = 46-62) at the treatment baseline and after sustained virological response to CHC treatment at the tertiary referral center. The collagen proportionate area (CPA) of liver tissue sections was determined using picrosirius red staining through digital image analysis. CD34 and α-smooth muscle actin (α-SMA) phenotypically quantitated liver angiogenesis and myofibroblasts, respectively, through immunohistochemistry staining, to correlate the total, portal, and extraportal liver angiogenesis with fibrogenesis.

RESULTS

Paired histology manifested significant regressions in fibrosis stages, and necroinflammatory grades (both P  < 0.001). The median of changes in CPAs (follow-up minus baseline) was -6.12% (interquartile range = -12.35 to -2.05%). The median of CPA changes per year was -1.38%/year (interquartile range = -2.98 to -0.51%/year). The significance of declines in total CD34 [coefficient (95% confidence interval), 5.577 (3.286-7.868); P  < 0.001] outweighed α-SMA declines, when explaining (R2 = 0.522; adjusted R2 = 0.502) the CPA declines through multiple regression analysis adjusting for other histological variables.

CONCLUSION

Through viral eradication in CHC, the downregulated liver angiogenesis significantly explains the CPA regression.

Correlation Between Vascular Endothelial Growth Factor and Long-Term Occurrence of HCV-Related Hepatocellular Carcinoma After Treatment with Direct-Acting Antivirals

We aimed to evaluate the correlation between vascular endothelial growth factor (VEGF) and long-term occurrence of hepatocellular carcinoma after HCV treatment with direct-acting antivirals (DAAs) and the HCC stage. Two groups with HCV-related liver cirrhosis and HCC were included: group 1, HCC following DAAs; group 2, HCC did not receive DAAs. The serum level of VEGF and HCC staging was evaluated. The duration between DAAs and HCC was 21.81 ± 11.66 months. Portal vein thrombosis (PVT) was observed more in group 1 (31%). VEGF was relatively elevated in group 1 compared to group 2. HCC patients after DAAs, showed elevated VEGF with frequent PVT.

TGF-β isoforms inhibit hepatitis C virus propagation in transforming growth factor beta/SMAD protein signalling pathway dependent and independent manners

Transforming growth factor beta (TGF‐β) plays an important role in the viral liver disease progression via controlling viral propagation and mediating inflammation‐associated responses. However, the antiviral activities and mechanisms of TGF‐β isoforms, including TGF‐β1, TGF‐β2 and TGF‐β3, remain unclear. Here, we demonstrated that all of the three TGF‐β isoforms were increased in Huh7.5 cells infected by hepatitis C virus (HCV), but in turn, the elevated TGF‐β isoforms could inhibit HCV propagation with different potency in infectious HCV cell culture system. TGF‐β isoforms suppressed HCV propagation through interrupting several different stages in the whole HCV life cycle, including virus entry and intracellular replication, in TGF‐β/SMAD signalling pathway–dependent and TGF‐β/SMAD signalling pathway–independent manners. TGF‐β isoforms showed additional anti‐HCV activities when combined with each other. However, the elevated TGF‐β1 and TGF‐β2, not TGF‐β3, could also induce liver fibrosis with a high expression of type I collagen alpha‐1 and α‐smooth muscle actin in LX‐2 cells. Our results showed a new insight into TGF‐β isoforms in the HCV‐related liver disease progression.

Vascular endothelial growth factor in relation to the development of hepatocellular carcinoma in hepatitis C virus patients treated by direct-acting antivirals

Background

Hepatocellular carcinoma (HCC) comprises 5.6% of all cancers worldwide representing the sixth most common cancer. It is also the fourth most common cause of cancer-related mortality. Angiogenesis is a main factor in the development of HCC. Vascular endothelial growth factor (VEGF) is considered as the force for physiological and pathological angiogenesis, and overexpression of VEGF is prominent in HCC. We aimed to study the effect of direct-acting antivirals (DAAs) on VEGF considered as the key regulator of angiogenesis in HCC. This cross-sectional study involved fifty patients who were divided into two groups: group I—twenty-five chronic hepatitis C virus (HCV) patients as (cases) subjected to treatment with direct-acting antiviral drugs for 3 months; group II—twenty-five chronic HCV patients developed HCC as (controls). Serum VEGF level was measured in of group I at baseline, at end of treatment, and 3 months after the end of treatment by sofosbuvir 400 mg plus daclatasvir 60 mg for 3 months in the HCV patient group, also VEGF was assessed in group II with HCC.

Results

Serum VEGF was high in both groups, but it was higher in the HCC group with a statistically significant difference (p < 0.001), also serum VEGF in the HCV group decreased after 3 months at the end of DAA treatment from 209.5 ± 137.6 to 44.1 (31.8–55.3) mg/ml, and all patients who received DAAs achieved sustained virologic response (SVR).

Conclusion

We found that change in serum VEGF in HCV patients treated with DAAs in this study cannot explain the risk of HCC after treatment by DAAs.

Strategies Targeting the Innate Immune Response for the Treatment of Hepatitis C Virus-Associated Liver Fibrosis

Direct-acting antivirals eliminate hepatitis C virus (HCV) in more than 95% of treated individuals and may abolish liver injury, arrest fibrogenesis, and reverse fibrosis and cirrhosis. However, liver regeneration is usually a slow process that is less effective in the late stages of fibrosis. What is more, fibrogenesis may prevail in patients with advanced cirrhosis, where it can progress to liver failure and hepatocellular carcinoma. Therefore, the development of antifibrotic drugs that halt and reverse fibrosis progression is urgently needed. Fibrosis occurs due to the repair process of damaged hepatic tissue, which eventually leads to scarring. The innate immune response against HCV is essential in the initiation and progression of liver fibrosis. HCV-infected hepatocytes and liver macrophages secrete proinflammatory cytokines and chemokines that promote the activation and differentiation of hepatic stellate cells (HSCs) to myofibroblasts that produce extracellular matrix (ECM) components. Prolonged ECM production by myofibroblasts due to chronic inflammation is essential to the development of fibrosis. While no antifibrotic therapy is approved to date, several drugs are being tested in phase 2 and phase 3 trials with promising results. This review discusses current state-of-the-art knowledge on treatments targeting the innate immune system to revert chronic hepatitis C-associated liver fibrosis. Agents that cause liver damage may vary (alcohol, virus infection, etc.), but fibrosis progression shows common patterns among them, including chronic inflammation and immune dysregulation, hepatocyte injury, HSC activation, and excessive ECM deposition. Therefore, mechanisms underlying these processes are promising targets for general antifibrotic therapies.

Hepatitis C virus core protein: Not just a nucleocapsid building block, but an immunity and inflammation modulator

Coevolution occurs between viruses and their hosts. The hosts need to evolve means to eliminate pathogenic virus infections, and the viruses, for their own survival and multiplication, have to develop mechanisms to escape clearance by hosts. Hepatitis C virus (HCV) of Flaviviridae is a pathogen which infects human liver and causes hepatitis, a condition of liver inflammation. Unlike most of the other flaviviruses, HCV has an excellent ability to evade host immunity to establish chronic infection. The persistent liver infection leads to chronic hepatitis, liver cirrhosis, hepatocellular carcinoma (HCC), as well as extrahepatic HCV-related diseases. HCV genomic RNA only expresses 10 proteins, many of which bear functions, in addition to those involved in HCV life cycle, for assisting the virus to develop its persistency. HCV core protein is a structural protein which encapsulates HCV genomic RNA and assembles into nucleocapsids. The core protein is also found to exert functions to affect host inflammation and immune responses by altering a variety of host pathways. This paper reviews the studies regarding the HCV core protein-induced alterations of host immunity and inflammatory responses, as well as the involvements of the HCV core protein in pro- and anti-inflammatory cytokine stimulations, host cellular transcription, lipid metabolism, cell apoptosis, cell proliferations, immune cell differentiations, oxidative stress, and hepatocyte steatosis, which leads to liver fibrosis, cirrhosis, and HCC. Implications of roles played by the HCV core protein in therapeutic resistance are also discussed.

Oxygen Sensing and Viral Replication: Implications for Tropism and Pathogenesis

The ability to detect and respond to varying oxygen tension is an essential prerequisite to life. Several mechanisms regulate the cellular response to oxygen including the prolyl hydroxylase domain (PHD)/factor inhibiting HIF (FIH)-hypoxia inducible factor (HIF) pathway, cysteamine (2-aminoethanethiol) dioxygenase (ADO) system, and the lysine-specific demethylases (KDM) 5A and KDM6A. Using a systems-based approach we discuss the literature on oxygen sensing pathways in the context of virus replication in different tissues that experience variable oxygen tension. Current information supports a model where the PHD-HIF pathway enhances the replication of viruses infecting tissues under low oxygen, however, the reverse is true for viruses with a selective tropism for higher oxygen environments. Differences in oxygen tension and associated HIF signaling may play an important role in viral tropism and pathogenesis. Thus, pharmaceutical agents that modulate HIF activity could provide novel treatment options for viral infections and associated pathological conditions.

Cortactin Interacts with Hepatitis C Virus Core and NS5A Proteins: Implications for Virion Assembly

Hepatitis C virus (HCV) exploits cellular proteins to facilitate viral propagation. To identify the cellular factors involved in the HCV life cycle, we previously performed protein microarray assays using either HCV nonstructural 5A (NS5A) protein or core protein as a probe. Interestingly, cellular cortactin strongly interacted with both NS5A and core. Cortactin is an actin-binding protein critically involved in tumor progression by regulating the migration and invasion of cancerous cells. Protein interaction between cortactin and NS5A or core was confirmed by coimmunoprecipitation and immunofluorescence assays. We showed that cortactin interacted with NS5A and core via the N-terminal acidic domain of cortactin. Cortactin expression levels were not altered by HCV infection. Small interfering RNA (siRNA)-mediated knockdown of cortactin dramatically decreased HCV protein expression and infectivity levels, whereas overexpression of cortactin increased viral propagation. Ectopic expression of the siRNA-resistant cortactin recovered the viral infectivity, suggesting that cortactin was specifically required for HCV propagation. We further showed that cortactin was involved in the assembly step without affecting viral entry, HCV internal ribosome entry site (IRES)-mediated translation, and the replication steps of the HCV life cycle. Of note, silencing of cortactin markedly reduced both NS5A and core protein levels on the lipid droplets (LDs), and this effect was reversed by the overexpression of cortactin. Importantly, NS5A and core promoted cell migration by activating the phosphorylation of cortactin at tyrosine residues 421 and 466. Taken together, these data suggest that cortactin is not only involved in HCV assembly but also plays an important role in the cell migration.IMPORTANCE Cortactin is a cytoskeletal protein that regulates cell migration in response to a number of extracellular stimuli. The functional involvement of cortactin in the virus life cycle is not yet fully understood. The most significant finding is that cortactin strongly interacted with both hepatitis C virus (HCV) core and NS5A. Cortactin is involved in HCV assembly by tethering core and NS5A on the lipid droplets (LDs) with no effect on LD biogenesis. It was noteworthy that HCV NS5A and core activated cortactin by phosphorylation at tyrosines 421 and 466 to regulate cell migration. Collectively, our study shows that cortactin is a novel host factor involved in viral production and HCV-associated pathogenesis.

Hepatitis C Virus and Hepatocellular Carcinoma: When the Host Loses Its Grip

Chronic infection with hepatitis C virus (HCV) is a major cause of hepatocellular carcinoma (HCC). Novel treatments with direct-acting antivirals achieve high rates of sustained virologic response; however, the HCC risk remains elevated in cured patients, especially those with advanced liver disease. Long-term HCV infection causes a persistent and accumulating damage of the liver due to a combination of direct and indirect pro-oncogenic mechanisms. This review describes the processes involved in virus-induced disease progression by viral proteins, derailed signaling, immunity, and persistent epigenetic deregulation, which may be instrumental to develop urgently needed prognostic biomarkers and as targets for novel chemopreventive therapies.

Hepatocellular Carcinoma Mechanisms Associated with Chronic HCV Infection and the Impact of Direct-Acting Antiviral Treatment

Hepatitis C virus (HCV) infection is the major risk factor for liver cirrhosis and hepatocellular carcinoma (HCC). The mechanisms of HCC initiation, growth, and metastasis appear to be highly complex due to the decade-long interactions between the virus, immune system, and overlapping bystander effects of host metabolic liver disease. The lack of a readily accessible animal model system for HCV is a significant obstacle to understand the mechanisms of viral carcinogenesis. Traditionally, the primary prevention strategy of HCC has been to eliminate infection by antiviral therapy. The success of virus elimination by antiviral treatment is determined by the SVR when the HCV is no longer detectable in serum. Interferon-alpha (IFN-α) and its analogs, pegylated IFN-α (PEG-IFN-α) alone with ribavirin (RBV), have been the primary antiviral treatment of HCV for many years with a low cure rate. The cloning and sequencing of HCV have allowed the development of cell culture models, which accelerated antiviral drug discovery. It resulted in the selection of highly effective direct-acting antiviral (DAA)-based combination therapy that now offers incredible success in curing HCV infection in more than 95% of all patients, including those with cirrhosis. However, several emerging recent publications claim that patients who have liver cirrhosis at the time of DAAs treatment face the risk of HCC occurrence and recurrence after viral cure. This remains a substantial challenge while addressing the long-term benefit of antiviral medicine. The host-related mechanisms that drive the risk of HCC in the absence of the virus are unknown. This review describes the multifaceted mechanisms that create a tumorigenic environment during chronic HCV infection. In addition to the potential oncogenic programming that drives HCC after viral clearance by DAAs, the current status of a biomarker development for early prediction of cirrhosis regression and HCC detection post viral treatment is discussed. Since DAAs treatment does not provide full protection against reinfection or viral transmission to other individuals, the recent studies for a vaccine development are also reviewed.

Rewiring Host Signaling: Hepatitis C Virus in Liver Pathogenesis

Hepatitis C virus (HCV) is a major cause of liver disease including metabolic disease, fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). HCV induces and promotes liver disease progression by perturbing a range of survival, proliferative, and metabolic pathways within the proinflammatory cellular microenvironment. The recent breakthrough in antiviral therapy using direct-acting antivirals (DAAs) can cure >90% of HCV patients. However, viral cure cannot fully eliminate the HCC risk, especially in patients with advanced liver disease or comorbidities. HCV induces an epigenetic viral footprint that promotes a pro-oncogenic hepatic signature, which persists after DAA cure. In this review, we summarize the main signaling pathways deregulated by HCV infection, with potential impact on liver pathogenesis. HCV-induced persistent signaling patterns may serve as biomarkers for the stratification of HCV-cured patients at high risk of developing HCC. Moreover, these signaling pathways are potential targets for novel chemopreventive strategies.

Differential network analysis depicts regulatory mechanisms for hepatocellular carcinoma from diverse backgrounds

Aim: To elucidate the integrative combinational gene regulatory network landscape of hepatocellular carcinoma (HCC) molecular carcinogenesis from diverse background. Materials & methods: Modified gene regulatory network analysis was used to prioritize differentially regulated genes and links. Integrative comparisons using bioinformatics methods were applied to identify potential critical molecules and pathways in HCC with different backgrounds. Results: E2F1 with its surrounding regulatory links were identified to play different key roles in the HCC risk factor dysregulation mechanisms. Hsa-mir-19a was identified as showed different effects in the three HCC differential regulation networks, and showed vital regulatory role in HBV-related HCC. Conclusion: We describe in detail the regulatory networks involved in HCC with different backgrounds. E2F1 may serve as a universal target for HCC treatment.

The hepatitis C viral nonstructural protein 5A stabilizes growth-regulatory human transcripts

Numerous mammalian proto-oncogene and other growth-regulatory transcripts are upregulated in malignancy due to abnormal mRNA stabilization. In hepatoma cells expressing a hepatitis C virus (HCV) subgenomic replicon, we found that the viral nonstructural protein 5A (NS5A), a protein known to bind to viral RNA, also bound specifically to human cellular transcripts that encode regulators of cell growth and apoptosis, and this binding correlated with transcript stabilization. An important subset of human NS5A-target transcripts contained GU-rich elements, sequences known to destabilize mRNA. We found that NS5A bound to GU-rich elements in vitro and in cells. Mutation of the NS5A zinc finger abrogated its GU-rich element-binding and mRNA stabilizing activities. Overall, we identified a molecular mechanism whereby HCV manipulates host gene expression by stabilizing host transcripts in a manner that would promote growth and prevent death of virus-infected cells, allowing the virus to establish chronic infection and lead to the development of hepatocellular carcinoma.

Hepatitis C virus core protein modulates several signaling pathways involved in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer, and hepatitis C virus (HCV) infection plays a major role in HCC development. The molecular mechanisms by which HCV infection leads to HCC are varied. HCV core protein is an important risk factor in HCV-associated liver pathogenesis and can modulate several signaling pathways involved in cell cycle regulation, cell growth promotion, cell proliferation, apoptosis, oxidative stress and lipid metabolism. The dysregulation of signaling pathways such as transforming growth factor β (TGF-β), vascular endothelial growth factor (VEGF), Wnt/β-catenin (WNT), cyclooxygenase-2 (COX-2) and peroxisome proliferator-activated receptor α (PPARα) by HCV core protein is implicated in the development of HCC. Therefore, it has been suggested that this protein be considered a favorable target for further studies in the development of HCC. In addition, considering the axial role of these signaling pathways in HCC, they are considered druggable targets for cancer therapy. Therefore, using strategies to limit the dysregulation effects of core protein on these signaling pathways seems necessary to prevent HCV-related HCC.

Molecular Mechanisms Involved in HCC Recurrence after Direct-Acting Antiviral Therapy

Chronic hepatitis C is associated with a high risk of developing hepatocellular carcinoma (HCC) because of a direct effect of the Hepatitis C Virus (HCV) proteins and an indirect oncogenic effect of chronic inflammation and impaired immune response. The treatment of chronic hepatitis C markedly reduces all-cause mortality; in fact, interferon-based treatment has shown a reduction of HCC incidence of more than 70%. The recent introduction of the highly effective direct-acting antivirals (DAAs) has completely changed the scenario of chronic hepatitis C (CHC) with rates of HCV cure over 90%. However, an unexpectedly high incidence of HCC recurrence was observed in patients after DAA treatment (27% versus 0.4–2% in patients who received interferon treatment). The mechanism that underlies the high rate of tumor relapse is currently unknown and is one of the main issues in hepatology. We reviewed the possible mechanisms involved in HCC recurrence after DAA treatment.

Autotaxin and vascular endothelial growth factor receptor-2 and -3 are related to vascular development during the progression of chronic viral hepatitis C

Vascular endothelial growth factor (VEGF) and autotaxin (ATX) play important roles in embryonic vasculogenesis and cancer progression. This study examines whether these two angiogenic factors cooperate in the mechanism that regulates vascular development during the progression of chronic viral hepatitis C (CVH-C) (Inuyama classification, F1-F4). First, surgical wedge biopsy specimens and needle biopsy specimens were obtained. Immunohistochemical staining for ATX and vascular endothelial growth factor receptor was assessed in serial sections. Immunoelectron microscopy was conducted with a perfusion-fixation method. In normal control liver tissue specimens, ATX was expressed at low levels within the branches of the hepatic artery and hepatic sinusoids. In F1 CVH-C liver tissue specimens, ATX was expressed within the branches of the hepatic artery. Additionally, VEGFR-2 was expressed within the branches of the hepatic artery and capillaries. In F3-F4 CVH-C liver tissue specimens, positive staining for ATX and VEGFR-2 or VEGFR-3 was detected in the branches of the hepatic artery or microlymphatic vessels. ATX-1 reaction products were specifically expressed on the plasma membrane of some microvascular endothelial cells (ECs) in the proliferative capillary artery. VEGFR-2 was expressed on caveolae in ECs and vascular smooth muscle cells. VEGFR-3 immunogold particles were also observed in lymphatic ECs. These results suggest functional interactions among ATX, VEGFR-2, and VEGFR-3 in the modulation of hemovascular and lymphovascular cell activation during vascular development.

Oncogenic Signaling Induced by HCV Infection

The liver is frequently exposed to toxins, metabolites, and oxidative stress, which can challenge organ function and genomic stability. Liver regeneration is therefore a highly regulated process involving several sequential signaling events. It is thus not surprising that individual oncogenic mutations in hepatocytes do not necessarily lead to cancer and that the genetic profiles of hepatocellular carcinomas (HCCs) are highly heterogeneous. Long-term infection with hepatitis C virus (HCV) creates an oncogenic environment by a combination of viral protein expression, persistent liver inflammation, oxidative stress, and chronically deregulated signaling events that cumulate as a tipping point for genetic stability. Although novel direct-acting antivirals (DAA)-based treatments efficiently eradicate HCV, the associated HCC risk cannot be fully eliminated by viral cure in patients with advanced liver disease. This suggests that HCV may persistently deregulate signaling pathways beyond viral cure and thereby continue to perturb cancer-relevant gene function. In this review, we summarize the current knowledge about oncogenic signaling pathways derailed by chronic HCV infection. This will not only help to understand the mechanisms of hepatocarcinogenesis but will also highlight potential chemopreventive strategies to help patients with a high-risk profile of developing HCC.

Transcriptional Regulatory Networks in Hepatitis C Virus-induced Hepatocellular Carcinoma

Understanding the transcriptional regulatory elements that influence the progression of liver disease in the presence of hepatitis C virus (HCV) infection is critical for the development of diagnostic and therapeutic approaches. Systems biology provides a roadmap by which these elements may be integrated. In this study, a previously published dataset of 124 microarray samples was analyzed in order to determine differentially expressed genes across four tissue types/conditions (normal, cirrhosis, cirrhosis HCC, and HCC). Differentially expressed genes were assessed for their functional clustering and those genes were annotated with their potential transcription factors and miRNAs. Transcriptional regulatory networks were constructed for each pairwise comparison between the 4 tissue types/conditions. Based on our analysis, it is predicted that the disruption in the regulation of transcription factors such as AP-1, PPARγ, and NF-κB could contribute to the liver progression from cirrhosis to steatosis and eventually to HCC. Whereas the condition of the liver digresses, the downregulation of miRNAs' (such as miR-27, Let-7, and miR-106a) expression makes the transition of the liver through each pathological stage more apparent. This preliminary data can be used to guide future experimental work. An understanding of the transcriptional regulatory attributes acts as a road map to help design interference strategies in order to target the key regulators of progression of HCV induced HCC.

Clinico-Pathological Importance of TGF-β/Phospho-Smad Signaling during Human Hepatic Fibrocarcinogenesis

Chronic viral hepatitis is a global public health problem, with approximately 570 million persons chronically infected. Hepatitis B and C viruses increase the risk of morbidity and mortality from liver cirrhosis, hepatocellular carcinoma (HCC), and extrahepatic complications that develop. Hepatitis virus infection induces transforming growth factor (TGF)-β, which influences microenvironments within the infected liver. TGF-β promotes liver fibrosis by up-regulating extracellular matrix production by hepatic stellate cells. TGF-β is also up-regulated in patients with HCC, in whom it contributes importantly to bringing about a favorable microenvironment for tumor growth. Thus, TGF-β is thought to be a major factor regulating liver fibrosis and carcinogenesis. Since TGF-β carries out regulatory signaling by influencing the phosphorylation of Smads, we have generated several kinds of phospho-specific antibodies to Smad2/3. Using these, we have identified three types of phospohorylated forms: COOH-terminally phosphorylated Smad2/3 (pSmad2C and pSmad3C), linker phosphorylated Smad2/3 (pSmad2L and pSmad3L), and dually phosphorylated Smad3 (pSmad2L/C and pSmad3L/C). TGF-β-mediated pSmad2/3C signaling terminates cell proliferation; on the other hand, cytokine-induced pSmad3L signaling accelerates cell proliferation and promotes fibrogenesis. This review addresses TGF-β/Smad signal transduction in chronic liver injuries and carcinogenic processes. We also discuss the reversibility of Smad signaling after antiviral therapy.

Association of HCV mutated proteins and host SNPs in the development of hepatocellular carcinoma

Hepatitis C virus plays a significant role in the development of hepatocellular carcinoma (HCC) globally. The pathogenic mechanisms of hepatocellular carcinoma with HCV infection are generally linked with inflammation, cytokines, fibrosis, cellular signaling pathways, and liver cell proliferation modulating pathways. HCV encoded proteins (Core, NS3, NS4, NS5A) interact with a broad range of hepatocytes derived factors to modulate an array of activities such as cell signaling, DNA repair, transcription and translational regulation, cell propagation, apoptosis, membrane topology. These four viral proteins are also implicated to show a strong conversion potential in tissue culture. Furthermore, Core and NS5A also trigger the accretion of the β-catenin pathway as a common target to contribute viral induced transformation. There is a strong association between HCV variants within Core, NS4, and NS5A and host single nucleotide polymorphisms (SNPs) with the HCC pathogenesis. Identification of such viral mutants and host SNPs is very critical to determine the risk of HCC and response to antiviral therapy. In this review, we highlight the association of key variants, mutated proteins, and host SNPs in development of HCV induced HCC. How such viral mutants may modulate the interaction with cellular host machinery is also discussed.

Molecular alterations in hepatocellular carcinoma associated with hepatitis B and hepatitis C infections

Chronic infections with hepatitis B (HBV) and hepatitis C viruses (HCV) are the leading cause of cirrhosis and hepatocellular carcinoma (HCC) worldwide. Both viruses encode multifunctional regulatory proteins activating several oncogenic pathways, which induce accumulation of multiple genetic alterations in the infected hepatocytes. Gene mutations in HBV- and HCV-induced HCCs frequently impair the TP53, Wnt/b-catenin, RAS/RAF/MAPK kinase and AKT/mTOR pathways, which represent important anti-cancer targets. In this review, we highlight the molecular mechanisms underlying the pathogenesis of primary liver cancer, with particular emphasis on the host genetic variations identified by high-throughput technologies. In addition, we discuss the importance of genetic alterations, such as mutations in the telomerase reverse transcriptase (TERT) promoter, for the diagnosis, prognosis, and tumor stratification for development of more effective treatment approaches.

Critical role of CREBH-mediated induction of transforming growth factor β2 by hepatitis C virus infection in fibrogenic responses in hepatic stellate cells

Mechanisms of hepatic fibrogenesis induced by hepatitis C virus (HCV), one of the leading causes of liver fibrosis, are not fully understood. We studied transcriptional up-regulation of transforming growth factor β (TGF-β), especially TGF-β2, which is mediated by activation of liver-enriched transcription factor cAMP-responsive element-binding protein, hepatocyte specific (CREBH) triggered by HCV infection and its functional significance for induction of profibrogenic phenotypes by interaction of HCV-infected cells with hepatic stellate cells (HSCs). Compared to TGF-β1, expression of TGF-β2 mRNA was induced faster and to a higher level upon HCV infection. Serum TGF-β2 levels in hepatitis C patients were higher compared to those in healthy individuals and were positively correlated with hepatic fibrosis stages F0-F2. TGF-β2 promoter activity was decreased and increased, respectively, by silencing and overexpression of CREBH. CREBH recognition sites were identified in the TGF-β2 promoter. CREBH binding to the promoter and its increase in cells expressing HCV Core-NS2 were shown by gel mobility shift and chromatin immunoprecipitation, respectively. The active form of CREBH was detectable in HCV-infected chimeric mice with human livers and cells expressing HCV proteins. Involvement of CREBH in HCV-induced fibrogenic response was further demonstrated in the CREBH null-mutant mouse model. Fibrogenic phenotypes were assessed using co-cultures of HCV-infected cells and HSCs. Expressions of fibrogenic factors and TGF-β1 increasing in the co-cultures was prevented by TGF-β2- or CREBH silencing.

CONCLUSION

CREBH was identified as a key positive regulator of TGF-β2 transcription in HCV-infected cells. TGF-β2 released from infected cells potentially contributes to cross-induction of TGF-β in an autocrine manner through its own signaling pathway, leading to an increase in fibrogenic responses in adjacent HSCs. (Hepatology 2017;66:1430-1443).

Hepatitis C virus core protein potentiates proangiogenic activity of hepatocellular carcinoma cells

Increased angiogenic activity has been demonstrated in hepatitis C virus (HCV)-related hepatocellular carcinoma (HCC), but the mechanism was unclear. To study the role of HCV core protein, we used tube formation and Matrigel plug assays to assess the proangiogenic activity of an HCC cell line, HuH7, and 2 of its stable clones—HuH7-core-high and HuH7-core-low, with high and low HCV core protein expression, respectively. In both assays, HuH7-core-high and HuH7-core-low cells dose-dependently induced stronger angiogenesis than control cells. HuH7 cells with HCV core protein expression showed increased mRNA and protein expression of vascular endothelial growth factor (VEGF). VEGF inhibition by bevacizumab reduced the proangiogenic activity of HuH7-core-high cells. The promotor region of VEGF contains the binding site of activator protein-1 (AP-1). Compared with controls, HuH7-core-high cells had an increased AP-1 activity and nuclear localization of phospho-c-jun. AP-1 inhibition using either RNA knockdown or AP-1 inhibitors reduced the VEGF mRNA expression and the proangiogenic activity of HuH7-core-high cells. Among 131 tissue samples from HCC patients, HCV-related HCC revealed stronger VEGF expression than did hepatitis B virus-related HCC. In conclusion, increased VEGF expression through AP-1 activation is a crucial mechanism underlying the proangiogenic activity of the HCV core protein in HCC cells.

Intrahepatic angiopoietin-2 correlates with chronic hepatitis C progression and is induced in hepatitis C virus replicon systems

BACKGROUND & AIMS

Chronic hepatitis C (CHC) is a major cause of cirrhosis and hepatocellular carcinoma and angiogenesis is closely related to the pathogenesis and progression of different chronic liver diseases (CLD). Thus, the intrahepatic expression of angiopoietins 1 and 2 (Ang1 and Ang2), as relevant mediators of pathological angiogenesis in several CLD, was investigated. In addition, the differential influence of structural and non-structural genomic regions of HCV on the expression of angiopoietins and the possible signalling involved were studied.

METHODS

Ang1 and Ang2 expression was evaluated by western blotting and enzyme-linked immunosorbent assay (ELISA) in liver homogenates of CHC patients (n=47) and uninfected subjects (n=8). Their association with disease progression (according to METAVIR classification) was assessed by Spearman's correlation. Statistical differences among the expression of angiopoietins at different CHC stages were calculated by Mann-Whitney U-test. Finally, the in vitro expression of Angiopoietins in HCV replicons (complete or non-structural subgenomic) and the main signalling pathways involved were also examined.

RESULTS

Ang2 levels were significantly higher in the liver of CHC patients compared to controls and significantly correlated with inflammation and fibrosis. Accordingly, an increased expression of Ang2 was found in all HCV replicons tested. Interestingly, the inhibition of MEK and PI3K signalling pathways exerted differential effects on Ang2 expression concerning to the genomic region of HCV.

CONCLUSIONS

Hepatitis C virus induces Ang2 expression in hepatocytes through different signalling routes which may lead to the disregulation of vascular homeostasis in the liver. Thus, pharmacologic intervention on Ang2 signalling might constitute an important therapeutic tool.

T-bet-mediated Tim-3 expression dampens monocyte function during chronic hepatitis C virus infection

Hepatitis C virus (HCV) induces a high rate of chronic infection via dysregulation of host immunity. We have previously shown that T-cell immunoglobulin and mucin domain protein-3 (Tim-3) is up-regulated on monocyte/macrophages (M/Mφ) during chronic HCV infection; little is known, however, about the transcription factor that controls its expression in these cells. In this study, we investigated the role of transcription factor, T-box expressed in T cells (T-bet), in Tim-3 expression in M/Mφ in the setting of HCV infection. We demonstrate that T-bet is constitutively expressed in resting CD14⁺ M/Mφ in the peripheral blood. M/Mφ from chronically HCV-infected individuals exhibit a significant increase in T-bet expression that positively correlates with an increased level of Tim-3 expression. Up-regulation of T-bet is also observed in CD14⁺ M/Mφ incubated with HCV⁺ Huh7.5 cells, as well as in primary M/Mφ or monocytic THP-1 cells exposed to HCV core protein in vitro, which is reversible by blocking HCV core/gC1qR interactions. Moreover, the HCV core-induced up-regulation of T-bet and Tim-3 expression in M/Mφ can be abrogated by incubating the cells with SP600125 - an inhibitor for the c-Jun N-terminal kinase (JNK) signalling pathway. Importantly, silencing T-bet gene expression decreases Tim-3 expression and enhances interleukin-12 secretion as well as signal transducer and activator of transcription 1 phosphorylation. These data suggest that T-bet, induced by the HCV core/gC1qR interaction, enhances Tim-3 expression via the JNK pathway, leading to dampened M/Mφ function during HCV infection. These findings reveal a novel mechanism for Tim-3 regulation via T-bet during HCV infection, providing new targets to combat this global epidemic viral disease.

Fibrosis is not just fibrosis - basement membrane modelling and collagen metabolism differs between hepatitis B- and C-induced injury

BACKGROUND

While morphological patterns differ, the molecular phenotype of liver fibrosis is considered a stereotypical response to chronic liver injury. However, with different cellular triggers and networks regulating fibrosis, the molecular responses of the injured liver may not be identical.

AIM

To investigate whether differences in extracellular matrix (ECM) composition of the liver during fibrogenesis in two seemingly similar types of viral hepatitis could be reflected by differences in ECM turnover.

METHODS

Utilising a cross-sectional design, we measured specific ECM protein fragments in plasma from 197 chronic hepatitis B (CHB) patients and 403 chronic hepatitis C (CHC) patients matched for inflammation grade and fibrosis stage. Markers of matrix metalloprotease degraded type I, III, IV and VI collagen (C1M, C3M, C4M, C6M) and type III and IV collagen formation (Pro-C3, P4NP7S).

RESULTS

P4NP7S, C3M, C4M and C6M were significantly elevated in CHB compared to CHC. In contrast, Pro-C3 was significantly elevated in CHC compared to CHB. Pro-C3, C3M and C4M were increased in parallel with inflammation and fibrosis in both cohorts. C6M and P4NP7S were associated with inflammation and fibrosis only in CHC. Basement membrane collagen fragments P4NP7S and C4M were significantly higher in matched activity and fibrosis cohorts within CHB vs CHC.

CONCLUSION

The main parameters to determine extracellular matrix biomarker levels are inflammation, fibrosis, and type of viral insult. Compared to CHC, CHB appears to induce a higher basement membrane turnover. This suggests that there are aetiology-dependent molecular signatures in liver fibrosis that could have pathogenic and diagnostic implications.

How Hepatitis C Virus Leads to Hepatocellular Carcinoma: A Network-Based Study

BACKGROUND

Hepatitis C virus (HCV) has been known as a major cause of hepatocellular carcinoma (HCC) worldwide. However, the distinct molecular mechanisms underlying the effects of HCV proteins on the HCC progression have remained unclear.

OBJECTIVES

In the present study, we studied the possible role of HCV in the HCC initiation and invasion using topological analysis of protein-protein interaction (PPI) networks.

MATERIALS AND METHODS

After analysis with GEO2R, a PPI network of differentially expressed genes (DEGs) was constructed for both chronic HCV and HCC samples. The STRING and GeneMANIA databases were used to determine the putative interactions between DEGs. In parallel, the functional annotation of DEGs was performed using g: Profiler web tool. The topological analysis and network visualization was carried outperformed using Cytoscape software and the top hub genes were identified. We determined the hub genes-related miRNAs using miRTarBase server and reconstructed a miRNA-Hubgene network.

RESULTS

Based on the topological analysis of miRNA-Hubgene network, we identified the key hub miRNAs. In order to identify the most important common sub-network, we aligned two PPI networks using NETAL tool. The c-Jun gene was identified as the most important hub gene in both HCV and HCC networks. Furthermore, the hsa-miR-34a, hsa-miR-155, hsa-miR-24, hsa-miR-744 and hsa-miR-92a were recognized as the most important hub miRNAs with positive correlation in the chronic HCV and HCC samples. Functional annotation of differentially expressed miRNAs (DEMs) using the tool for annotations of human miRNAs (TAM) revealed that there is a considerable overlap between miRNA gene expression profiles of HCV-infected and HCC cells.

CONCLUSIONS

Our results revealed the possible crucial genes and miRNAs involved in the initiation and progression of HCC cells infected with HCV.

Elevated Expression of Hepatoma Up-Regulated Protein Inhibits γ-Irradiation-Induced Apoptosis of Prostate Cancer Cells

Despite progression in diagnosis and treatment, prostate cancer (PCa) still represents the main cause of cancer-related mortality and morbidity in men. Although radiation therapy offers clinical benefit over other therapeutic modalities, the success of this therapeutic modality is commonly hampered by the resistance of advanced tumors. So far, the mechanisms governing tumor resistance to radiotherapy are not discussed in detail. Here, we demonstrate for the first time that the resistance of PCa to radiation therapy is attributed to elevated expression of Hepatoma Up-Regulated Protein (HURP). In PCa cells, the induction of HURP expression suppresses γ-irradiation-induced apoptosis. γ-irradiation-induced apoptosis of PCa cells is associated with expression of E2F1, p53, p21 proteins together with the phosphorylation of apoptosis signal-regulating kinase1 (ASK1), c-jun-N-terminal kinase (JNK) and Ataxia-telangiectasia mutated (ATM) and histone family member X (H2AX). Whereas, the induction of HURP expression is able to suppress γ-irradiation-induced effects on E2F1, p53, p21, ATM, ASK1, JNK and ATM, and H2AX. Also, inhibition of γ-irradiation-induced- cytochrome c release, cleavage of caspase-9, caspase-3, PARP, and reactive oxygen species (ROS) were noted in PCa cells induced for HURP expression. The observed radio-resistance of PCa is thought to be the consequence of HURP-mediated destabilization of p53 and ATM proteins that are essential for the modulation of γ-irradiation-induced apoptosis. Thus, based on our findings, PCa resistance to radiation therapy results from the deregulation of ASK1/ JNK; ATM/ H2AX; ATM/p53 and checkpoint kinase 2 (Chk2)/ E2F-1 in response to the elevated expression of HURP.

Angiogenesis and liver fibrosis

Recent data indicate that hepatic angiogenesis, regardless of the etiology, takes place in chronic liver diseases (CLDs) that are characterized by inflammation and progressive fibrosis. Because anti-angiogenic therapy has been found to be efficient in the prevention of fibrosis in experimental models of CLDs, it is suggested that blocking angiogenesis could be a promising therapeutic option in patients with advanced fibrosis. Consequently, efforts are being directed to revealing the mechanisms involved in angiogenesis during the progression of liver fibrosis. Literature evidences indicate that hepatic angiogenesis and fibrosis are closely related in both clinical and experimental conditions. Hypoxia is a major inducer of angiogenesis together with inflammation and hepatic stellate cells. These profibrogenic cells stand at the intersection between inflammation, angiogenesis and fibrosis and play also a pivotal role in angiogenesis. This review mainly focuses to give a clear view on the relevant features that communicate angiogenesis with progression of fibrosis in CLDs towards the-end point of cirrhosis that may be translated into future therapies. The pathogenesis of hepatic angiogenesis associated with portal hypertension, viral hepatitis, non-alcoholic fatty liver disease and alcoholic liver disease are also discussed to emphasize the various mechanisms involved in angiogenesis during liver fibrogenesis.

Hypoxia inducible factors in liver disease and hepatocellular carcinoma: current understanding and future directions

Hypoxia inducible transcription factors (HIFs) activate diverse pathways that regulate cellular metabolism, angiogenesis, proliferation, and migration, enabling a cell to respond to a low oxygen or hypoxic environment. HIFs are regulated by oxygen-dependent and independent signals including: mitochondrial dysfunction, reactive oxygen species, endoplasmic reticular stress, and viral infection. HIFs have been reported to play a role in the pathogenesis of liver disease of diverse aetiologies. This review explores the impact of HIFs on hepatocellular biology and inflammatory responses, highlighting the therapeutic potential of targeting HIFs for an array of liver pathologies.

CD133⁺ melanoma subpopulation acquired resistance to caffeic acid phenethyl ester-induced apoptosis is attributed to the elevated expression of ABCB5: significance for melanoma treatment

According to the cancer stem-like cell (CSC) hypothesis, neoplastic clones are maintained by a small fraction of cells with stem cell properties. Also, melanoma resistance to chemo- and radiotherapy is thought to be attributed to melanoma stem-like cells (MSCs). Caffeic acid phenethyl ester (CAPE) is a bioactive molecule, whose antitumor activity is approved in different tumor types. CAPE induced both apoptosis and E2F1 expression in CD133(-), but not in CD133(+) melanoma subpopulations. The resistance of CD133(+) melanoma subpopulation is attributed to the enhanced drug efflux mediated by ATP-binding cassette sub-family B member 5 (ABCB5), since the knockdown of ABCB5 was found to sensitize CD133(+) cells to CAPE. CAPE-induced apoptosis is mediated by E2F1 as evidenced by the abrogation of apoptosis induced in response to the knockdown of E2F1. The functional analysis of E2F1 in CD133(+) melanoma subpopulation demonstrated the ability of E2F1 gene transfer to trigger apoptosis of CD133(+) cells and to enhance the activation of apoptosis signal-regulating kinase (ASK1), c-Jun N-terminal kinase and p38, and the DNA-binding activities of the transcription factors AP-1 and p53. Also, the induction of E2F1 expression was found to enhance the expression of the pro-apoptotic proteins Bax, Noxa and Puma, and to suppress the anti-apoptotic protein Mcl-1. Using specific pharmacological inhibitors we could demonstrate that E2F1 overcomes the chemo-resistance of MSCs/CD133(+) cells by a mechanism mediated by both mitochondrial dysregulation and ER-stress-dependent pathways. In conclusion, our data addresses the mechanisms of CAPE/E2F1-induced apoptosis of chemo-resistant CD133(+) melanoma subpopulation.

Smad3 phospho-isoform signaling in hepatitis C virus-related chronic liver diseases

The risk of hepatocellular carcinoma (HCC) development increases as hepatitis virus C (HCV)-related liver diseases progress, especially in patients with active inflammation. Insight into hepatic carcinogenesis have emerged from recent detailed analyses of transforming growth factor-β and c-Jun-N-terminal kinase signaling processes directed by multiple phosphorylated (phospho)-isoforms of a Smad3 mediator. In the course of HCV-related chronic liver diseases, chronic inflammation and host genetic/epigenetic alterations additively shift the hepatocytic Smad3 phospho-isoform signaling from tumor suppression to carcinogenesis, increasing the risk of HCC. Chronic inflammation represents an early carcinogenic step that provides a nonmutagenic tumor-promoting stimulus. After undergoing successful antiviral therapy, patients with chronic hepatitis C could experience a lower risk of HCC as Smad3 phospho-isoform signaling reverses from potential carcinogenesis to tumor suppression. Even after HCV clearance, however, patients with cirrhosis could still develop HCC because of sustained, intense carcinogenic Smad3 phospho-isoform signaling that is possibly caused by genetic or epigenetic alterations. Smad3 phospho-isoforms should assist with evaluating the effectiveness of interventions aimed at reducing human HCC.

Mechanisms of hepatocarcinogenesis in chronic hepatitis C

Infection with hepatitis C virus (HCV) is a major risk factor for hepatocellular carcinoma. The genetic changes that drive cancer development are heterogeneous and how chronic hepatitis C promotes the initiation of hepatocellular carcinoma is incompletely understood. Cancer typically arises in the setting of advanced fibrosis and/or cirrhosis where chronic immune-mediated inflammation over decades promotes hepatocyte turnover providing selective pressure that favors the malignant phenotype. As well as contributions of unresolved inflammation to carcinogenesis, evidence from transgenic mice with liver-specific expression of viral sequences suggests that some HCV-encoded proteins may directly promote cancer. Numerous in vitro studies suggest roles for HCV proteins in subversion of cellular pathways that normally act to suppress tumorigenesis. Here, we review the mechanisms by which persistent HCV infection might promote cancer in addition to the procarcinogenic effects of inflammatory liver disease.

Ebola virus modulates transforming growth factor β signaling and cellular markers of mesenchyme-like transition in hepatocytes

Ebola virus (EBOV) causes a severe hemorrhagic disease in humans and nonhuman primates, with a median case fatality rate of 78.4%. Although EBOV is considered a public health concern, there is a relative paucity of information regarding the modulation of the functional host response during infection. We employed temporal kinome analysis to investigate the relative early, intermediate, and late host kinome responses to EBOV infection in human hepatocytes. Pathway overrepresentation analysis and functional network analysis of kinome data revealed that transforming growth factor (TGF-β)-mediated signaling responses were temporally modulated in response to EBOV infection. Upregulation of TGF-β signaling in the kinome data sets correlated with the upregulation of TGF-β secretion from EBOV-infected cells. Kinase inhibitors targeting TGF-β signaling, or additional cell receptors and downstream signaling pathway intermediates identified from our kinome analysis, also inhibited EBOV replication. Further, the inhibition of select cell signaling intermediates identified from our kinome analysis provided partial protection in a lethal model of EBOV infection. To gain perspective on the cellular consequence of TGF-β signaling modulation during EBOV infection, we assessed cellular markers associated with upregulation of TGF-β signaling. We observed upregulation of matrix metalloproteinase 9, N-cadherin, and fibronectin expression with concomitant reductions in the expression of E-cadherin and claudin-1, responses that are standard characteristics of an epithelium-to-mesenchyme-like transition. Additionally, we identified phosphorylation events downstream of TGF-β that may contribute to this process. From these observations, we propose a model for a broader role of TGF-β-mediated signaling responses in the pathogenesis of Ebola virus disease.

IMPORTANCE

Ebola virus (EBOV), formerly Zaire ebolavirus, causes a severe hemorrhagic disease in humans and nonhuman primates and is the most lethal Ebola virus species, with case fatality rates of up to 90%. Although EBOV is considered a worldwide concern, many questions remain regarding EBOV molecular pathogenesis. As it is appreciated that many cellular processes are regulated through kinase-mediated phosphorylation events, we employed temporal kinome analysis to investigate the functional responses of human hepatocytes to EBOV infection. Administration of kinase inhibitors targeting signaling pathway intermediates identified in our kinome analysis inhibited viral replication in vitro and reduced EBOV pathogenesis in vivo. Further analysis of our data also demonstrated that EBOV infection modulated TGF-β-mediated signaling responses and promoted "mesenchyme-like" phenotypic changes. Taken together, these results demonstrated that EBOV infection specifically modulates TGF-β-mediated signaling responses in epithelial cells and may have broader implications in EBOV pathogenesis.

Inflammatory response of endothelial cells to hepatitis C virus recombinant envelope glycoprotein 2 protein exposure

The hepatitis C virus (HCV) encodes approximately 10 different structural and non-structural proteins, including the envelope glycoprotein 2 (E2). HCV proteins, especially the envelope proteins, bind to cell receptors and can damage tissues. Endothelial inflammation is the most important determinant of fibrosis progression and, consequently, cirrhosis. The aim of this study was to evaluate and compare the inflammatory response of endothelial cells to two recombinant forms of the HCV E2 protein produced in different expression systems (Escherichia coli and Pichia pastoris). We observed the induction of cell death and the production of nitric oxide, hydrogen peroxide, interleukin-8 and vascular endothelial growth factor A in human umbilical vein endothelial cells (HUVECs) stimulated by the two recombinant E2 proteins. The E2-induced apoptosis of HUVECs was confirmed using the molecular marker PARP. The apoptosis rescue observed when the antioxidant N-acetylcysteine was used suggests that reactive oxygen species are involved in E2-induced apoptosis. We propose that these proteins are involved in the chronic inflammation caused by HCV.

TGF-β/Smad signaling during hepatic fibro-carcinogenesis (review)

After hepatitis virus infection, plasma transforming growth factor (TGF)-β increases in either the acute or chronic inflammatory microenvironment. Although TGF-β is upregulated in patients with hepatocellular carcinoma, it is one of the most potent growth inhibitors for hepatocytes. This cytokine also upregulates extracellular matrix (ECM) production of hepatic stellate cells. Therefore, TGF-β is considered to be the major factor regulating liver carcinogenesis and accelerating liver fibrosis. Smad2 and Smad3 act as the intracellular mediators of TGF-β signal transduction pathway. We have generated numerous antibodies against individual phosphorylation sites in Smad2/3, and identified 3 types of phosphorylated forms (phospho-isoforms): COOH-terminally phosphorylated Smad2/3 (pSmad2C and pSmad3C), linker phosphorylated Smad2/3 (pSmad2L and pSmad3L) and dually phosphorylated Smad2/3 (pSmad2L/C and pSmad3L/C). These Smad phospho-isoforms are categorized into 3 groups: cytostatic pSmad3C signaling, mitogenic pSmad3L signaling and invasive/fibrogenic pSmad2L/C signaling. In this review, we describe differential regulation of TGF-β/Smad signaling after acute or chronic liver injuries. In addition, we consider how chronic inflammation associated with hepatitis virus infection promotes hepatic fibrosis and carcinogenesis (fibro-carcinogenesis), focusing on alteration of Smad phospho-isoform signaling. Finally, we show reversibility of Smad phospho-isoform signaling after therapy against hepatitis virus infection.

Production and pathogenicity of hepatitis C virus core gene products

Hepatitis C virus (HCV) is a major cause of chronic liver diseases, including steatosis, cirrhosis and hepatocellular carcinoma, and its infection is also associated with insulin resistance and type 2 diabetes mellitus. HCV, belonging to the Flaviviridae family, is a small enveloped virus whose positive-stranded RNA genome encoding a polyprotein. The HCV core protein is cleaved first at residue 191 by the host signal peptidase and further cleaved by the host signal peptide peptidase at about residue 177 to generate the mature core protein (a.a. 1-177) and the cleaved peptide (a.a. 178-191). Core protein could induce insulin resistance, steatosis and even hepatocellular carcinoma through various mechanisms. The peptide (a.a. 178-191) may play a role in the immune response. The polymorphism of this peptide is associated with the cellular lipid drop accumulation, contributing to steatosis development. In addition to the conventional open reading frame (ORF), in the +1 frame, an ORF overlaps with the core protein-coding sequence and encodes the alternative reading frame proteins (ARFP or core+1). ARFP/core+1/F protein could enhance hepatocyte growth and may regulate iron metabolism. In this review, we briefly summarized the current knowledge regarding the production of different core gene products and their roles in viral pathogenesis.

Paracrine signals from liver sinusoidal endothelium regulate hepatitis C virus replication

Hepatitis C virus (HCV) is a major cause of global morbidity, causing chronic liver injury that can progress to cirrhosis and hepatocellular carcinoma. The liver is a large and complex organ containing multiple cell types, including hepatocytes, sinusoidal endothelial cells (LSEC), Kupffer cells, and biliary epithelial cells. Hepatocytes are the major reservoir supporting HCV replication; however, the role of nonparenchymal cells in the viral lifecycle remains largely unexplored. LSEC secrete factors that promote HCV infection and transcript analysis identified bone morphogenetic protein 4 (BMP4) as a candidate endothelial-expressed proviral molecule. Recombinant BMP4 increased HCV replication and neutralization of BMP4 abrogated the proviral activity of LSEC-conditioned media. Importantly, BMP4 expression was negatively regulated by vascular endothelial growth factor A (VEGF-A) by way of a VEGF receptor-2 (VEGFR-2) primed activation of p38 MAPK. Consistent with our in vitro observations, we demonstrate that in normal liver VEGFR-2 is activated and BMP4 expression is suppressed. In contrast, in chronic liver disease including HCV infection where there is marked endothelial cell proliferation, we observed reduced endothelial cell VEGFR-2 activation and a concomitant increase in BMP4 expression.

CONCLUSION

These studies identify a role for LSEC and BMP4 in HCV infection and highlight BMP4 as a new therapeutic target for treating individuals with liver disease.

Vinblastine-induced apoptosis of melanoma cells is mediated by Ras homologous A protein (Rho A) via mitochondrial and non-mitochondrial-dependent mechanisms

Despite the availability of melanoma treatment at the primary site, the recurrence of local melanoma can metastasize to any distant organ. Currently, the available therapies for the treatment of metastatic melanoma are of limited benefit. Thus, the functional analysis of conventional therapies may help to improve their efficiency in the treatment of metastatic melanoma. In the present study, the exposure of melanoma cells to vinblastine was found to trigger apoptosis as evidenced by the loss of mitochondrial membrane potential, the release of both cytochrome c and apoptosis inducing factor, activation of caspase-9 and 3, and cleavage of Poly (ADP-ribose)-Polymerase. Also, vinblastine enhances the phosphorylation of Ras homologous protein A, the accumulation of reactive oxygen species, the release of intracellular Ca(2+), as well as the activation of apoptosis signal-regulating kinase 1, c-jun-N-terminal kinase, p38, inhibitor of kappaBα (IκBα) kinase, and inositol requiring enzyme 1α. In addition, vinblastine induces the DNA-binding activities of the transcription factor NF-κB, HSF1, AP-1, and ATF-2, together with the expression of HSP70 and Bax proteins. Moreover, inhibitory experiments addressed a central role for Rho A in the regulation of vinblastine-induced apoptosis of melanoma cells via mitochondrial and non-mitochondrial-dependent mechanisms. In conclusion, the present study addresses for the first time a central role for Rho A in the modulation of vinblastine-induced apoptosis of melanoma cells and thereby provides an insight into the molecular action of vinblastine in melanoma treatment.