Loss of microRNA 122 expression in patients with hepatitis B enhances hepatitis B virus replication through cyclin G(1) -modulated P53 activity

MicroRNA miR-21 attenuates human cytomegalovirus replication in neural cells by targeting Cdc25a

Congenital human cytomegalovirus (HCMV) infection is a leading cause of birth defects, primarily manifesting as neurological disorders. HCMV infection alters expression of cellular microRNAs (miRs) and induces cell cycle arrest, which in turn modifies the cellular environment to favor virus replication. Previous observations found that HCMV infection reduces miR-21 expression in neural progenitor/stem cells (NPCs). Here, we show that infection of NPCs and U-251MG cells represses miR-21 while increasing the levels of Cdc25a, a cell cycle regulator and known target of miR-21. These opposing responses to infection prompted an investigation of the relationship between miR-21, Cdc25a, and viral replication. Overexpression of miR-21 in NPCs and U-251MG cells inhibited viral gene expression, genome replication, and production of infectious progeny, while shRNA-knockdown of miR-21 in U-251MG cells increased viral gene expression. In contrast, overexpression of Cdc25a in U-251MG cells increased viral gene expression and production of infectious progeny and overcame the inhibitory effects of miR-21 overexpression. Three viral gene products-IE1, pp71, and UL26-were shown to inhibit miR-21 expression at the transcriptional level. These results suggest that Cdc25a promotes HCMV replication and elevation of Cdc25a levels after HCMV infection are due in part to HCMV-mediated repression of miR-21. Thus, miR-21 is an intrinsic antiviral factor that is modulated by HCMV infection. This suggests a role for miR-21 downregulation in the neuropathogenesis of HCMV infection of the developing CNS.

IMPORTANCE

Human cytomegalovirus (HCMV) is a ubiquitous pathogen and has very high prevalence among population, especially in China, and congenital HCMV infection is a major cause for birth defects. Elucidating virus-host interactions that govern HCMV replication in neuronal cells is critical to understanding the neuropathogenesis of birth defects resulting from congenital infection. In this study, we confirm that HCMV infection downregulates miR-21 but upregulates Cdc25a. Further determined the negative effects of cellular miRNA miR-21 on HCMV replication in neural progenitor/stem cells and U-251MG glioblastoma/astrocytoma cells. More importantly, our results provide the first evidence that miR-21 negatively regulates HCMV replication by targeting Cdc25a, a vital cell cycle regulator. We further found that viral gene products of IE1, pp71, and UL26 play roles in inhibiting miR-21 expression, which in turn causes increases in Cdc25a and benefits HCMV replication. Thus, miR-21 appears to be an intrinsic antiviral factor that represents a potential target for therapeutic intervention.

Differences in serum microRNA profiles in hepatitis B and C virus infection

OBJECTIVES

Patients infected with chronic hepatitis B virus (HBV) or hepatitis C virus (HCV) are at greater risk of cirrhosis and hepatocellular carcinoma. The objective of this study was to identify virus-specific serum microRNA profiles associated with liver function and disease progression. Microarray analysis of serum microRNAs was performed using the Toray 3D array system in 22 healthy subjects, 42 HBV patients, and 30 HCV patients. Selected microRNAs were then validated by qRT-PCR in 186 HBV patients, 107 HCV patients, and 22 healthy subjects.

RESULTS

Microarray analysis showed up-regulation of a number of microRNAs in serum of both HBV and HCV patients. In qRT-PCR analysis, miR-122, miR-99a, miR-125b, miR-720, miR-22, and miR-1275 were up-regulated both in HBV patients relative to healthy subjects, and all except miR-1275 were up-regulated in HBeAg-positive patients relative to HBeAg-negative patients. Specific microRNAs were independently associated with different aspects of HBV infection. MiR-122 was independently associated with HBV DNA level, whereas miR-125b was independently associated with levels of HBV DNA, HBsAg, and HBeAg. MiR-22 and miR-1275 were independently associated with serum γ-glutamyl transpeptidase levels.

CONCLUSIONS

Serum microRNA levels reflect differences in the etiology and stage of viral hepatitis.

MicroRNA-26b inhibits hepatitis B virus transcription and replication by targeting the host factor CHORDC1 protein

Hepatitis B virus (HBV) causes acute and chronic hepatitis in humans, and HBV infection is a major threat to global health. HBV replication is regulated by a series of host factors, including microRNAs (miRNAs), which are highly conserved small noncoding RNAs that participate in a variety of physiological and pathological processes. Here, we report that a chemically synthesized mimic of miR-26b inhibited HBV antigen expression, transcription, and replication, whereas antisense knockdown of endogenous miR-26b enhanced HBV replication in HepG2 cells. Overexpression and knockdown experiments showed that miR-26b significantly decreased HBV enhancer/promoter activities. We identified the cysteine- and histidine-rich domain containing 1 (CHORDC1) as a novel host factor target of miR-26b. CHORDC1 protein but not mRNA was markedly decreased by miR-26b overexpression via base-pairing with complementary sequences in the 3'UTR of its mRNA. Overexpression and knockdown studies showed that CHORDC1 increased viral antigen expression, transcription, and replication by elevating HBV enhancer/promoter activities. Conversely, HBV infection suppressed miR-26b expression and increased CHORDC1 protein levels in human liver cells. Another mature miRNA of the hsa-miR-26 family, miR-26a, had a similar function as miR-26b in targeting CHORDC1 and affecting HBV production. These results suggest that suppression of miR-26b expression up-regulates its target gene CHORDC1, which increases HBV enhancer/promoter activities and promotes viral transcription, gene expression, and replication. Our study could provide new insights into miRNA expression and the persistence of HBV infection.

Complex interactions between microRNAs and hepatitis B/C viruses

MicroRNAs (miRNAs) are a class of small noncoding RNAs that post-transcriptionally regulate the expression of many target genes via mRNA degradation or translation inhibition. Many studies have shown that miRNAs are involved in the modulation of gene expression and replication of hepatitis B virus (HBV) and hepatitis C virus (HCV) and play a pivotal role in host-virus interactions. Increasing evidence also demonstrates that viral infection leads to alteration of the miRNA expression profile in hepatic tissues or circulation. The deregulated miRNAs participate in hepatocellular carcinoma (HCC) initiation and progression by functioning as oncogenes or tumor suppressor genes by targeting various genes involved in cancer-related signaling pathways. The distinct expression pattern of miRNAs may be a useful marker for the diagnosis and prognosis of virus-related diseases considering the limitation of currently used biomarkers. Moreover, the role of deregulated miRNA in host-virus interactions and HCC development suggested that miRNAs may serve as therapeutic targets or as tools. In this review, we summarize the recent findings about the deregulation and the role of miRNAs during HBV/HCV infection and HCC development, and we discuss the possible mechanism of action of miRNAs in the pathogenesis of virus-related diseases. Furthermore, we discuss the potential of using miRNAs as markers for diagnosis and prognosis as well as therapeutic targets and drugs.

MicroRNAs associated with HBV infection and HBV-related HCC

Hepatitis B virus (HBV) infection is a global problem and a major risk factor for hepatocellular carcinoma (HCC). microRNAs (miRNAs) comprise a group of small noncoding RNAs regulating gene expression at the posttranslational level, thereby participating in fundamental biological processes, including cell proliferation, differentiation, and apoptosis. In this review, we summarize the roles of miRNAs in HBV infection, the recently identified mechanism underlying dysregulation of miRNAs in HBV-associated HCC, and their association with hepatocarcinogenesis. Moreover, we discuss the recent advances in the use of circulating miRNAs in the early diagnosis of HCC as well as therapies based on these aberrantly expressed miRNAs.

Regulation of viral oncogenesis by microRNAs

Viral infection may play a causative role in human cancers, for example hepatitis B virus (HBV) or hepatitis C virus (HCV) in liver cancer, human papilloma virus (HPV) in cervical cancer, and Epstein-Barr virus (EBV) in nasopharyngeal carcinoma. Virally infected cells express viral-encoded genes that are critical for oncogenesis. Some viruses also encode microRNA (miRNA) species. miRNAs are small noncoding RNA molecules that play an important role in cancer development and progression. Recent studies indicate an important interplay among viral oncoproteins, virus-encoded miRNAs, cellular miRNAs, and cellular genes. This review focuses on modulation of HBV-, HCV-, HPV-, and EBV-associated cancers by cellular and/or viral miRNA. An understanding of the mechanisms underlying the regulation of viral carcinogenesis by miRNAs may provide new targets for the development of specific viral therapies.

miR-125b inhibits hepatitis B virus expression in vitro through targeting of the SCNN1A gene

microRNAs (miRNAs) are small noncoding RNAs that modulate gene expression at the posttranscriptional level, playing an important role in many diseases. However, reports concerning the role of miRNA in hepatitis B virus (HBV) infection are limited. miRNA chips were used to investigate miRNA changes during HBV infection in vitro. Bioinformatics analysis was used to explore possible miRNA and target genes during HBV infection. The expression of miR-125b and its potential target gene, sodium channel, non-voltage-gated 1 alpha (SCNN1A), was further analyzed. A total of 136 miRNAs were analyzed in an HBV transient transfection model (HepG2-HBV1.3), and 78 miRNAs were differentially expressed in HepG2.2.15 cells compared with HepG2 cells. miR-125b expression was decreased in both HepG2-HBV1.3 and HepG2.2.15 cells, and ectopic expression of miR-125b inhibited HBV DNA intermediates and secretion of HBsAg and HBeAg. miR-125b also inhibited the mRNA and protein levels of SCNN1A. Using a dual luciferase reporter system, we found that SCNN1A was one of the targets of miR-125b. In this study, we found that miR-125b inhibits HBV expression in vitro by regulating SCNN1A expression.

MiRNA-548ah, a potential molecule associated with transition from immune tolerance to immune activation of chronic hepatitis B

OBJECTIVE

The present study aims to identify the differently expressed microRNA (miRNA) molecules and target genes of miRNA in the immune tolerance (IT) and immune activation (IA) stages of chronic hepatitis B (CHB).

METHODS

miRNA expression profiles of peripheral blood mononuclear cells (PBMCs) at the IT and IA stages of CHB were screened using miRNA microarrays and authenticated using a quantitative real-time polymerase chain reaction (RT-PCR). Gene ontology (GO) and the Kyoto encyclopedia of genes and genomes (KEGG) were used to analyze the significant functions and pathways of possible target genes of miRNAs. Assays of the gain and loss of function of the miRNAs were performed to verify the target genes in THP-1 cell lines. The luciferase reporter test was used on 293T cells as direct targets.

RESULTS

Significantly upregulated miR-548 and miR-4804 were observed in the miRNA microarrays and confirmed by RT-PCR in PBMCs at the IT and IA stages of CHB. GO and KEGG analysis revealed that MiR-548 and miR-4804 could be involved in numerous signaling pathways and protein binding activity. IFNγR1 was predicted as a target gene and validated as the direct gene of MiR-548. Significant negative correlation was found between the miR-548ah and mRNA levels of IFN-γR1 in CHB patients.

CONCLUSIONS

The abnormal expression profiles of miRNA in PBMCs could be closely associated with immune activation of chronic HBV infection. miR-548, by targeting IFN-γR1, may represent a mechanism that can facilitate viral pathogenesis and help determine new therapeutic molecular targets.

MiR-221 accentuates IFN׳s anti-HCV effect by downregulating SOCS1 and SOCS3

MiR-221 was reported to be upregulated and play roles in tumorigenesis of hepatitis C virus (HCV) associated hepatocellular carcinoma (HCC). However, the role of miR-221 in HCV infection remains unknown. In this study, it was found that miR-221 was upregulated in serum of HCV chronic hepatitis patients and Huh7.5.1 cells infected with HCVcc. Further studies indicated that miR-221 mimic could accentuate anti-HCV effect of IFN-α in HCVcc model, miR-221 mimic could further repressed 10% HCV RNA expression and 35-42% HCV core or NS5A protein expression in HCVcc infected Huh7.5.1 cells treated with 100IU/mL IFN-α, and miR-221 inhibitor resulted in the reverse effects. Furthermore, two members of suppressor of cytokine signaling (SOCS) family, SOCS1 and SOCS3, which are well established inhibitory factors on IFN/JAK/STAT pathway, were identified as the targets of miR-221 and were involved in the effect of miR-221. In conclusion, miR-221 could accentuate IFN׳s anti-HCV effect by targeting SOCS1 and SOCS3.

miRNAs affect the development of hepatocellular carcinoma via dysregulation of their biogenesis and expression

The pathogenesis of hepatocellular carcinoma (HCC) is not fully understood, which has affected the early diagnosis and treatment of HCC and the survival time of patients. MicroRNAs (miRNAs) are a class of evolutionarily conserved small, non-coding RNAs, which regulate the expression of various genes post-transcriptionally. Emerging evidence indicates that the key enzymes involved in the miRNA biosynthesis pathway and some tumor-specific miRNAs are widely deregulated or upregulated in HCC and closely associated with the occurrence and development of various cancers, including HCC. Early studies have shown that miRNAs have critical roles in HCC progression by targeting many critical protein-coding genes, thereby contributing to the promotion of cell proliferation; the avoidance of apoptosis, inducing via angiogenesis; and the activation of invasion and metastasis pathways. Experimental data indicate that discovery of increasing numbers of aberrantly expressed miRNAs has opened up a new field for investigating the molecular mechanism of HCC progression. In this review, we describe the current knowledge about the roles and validated targets of miRNAs in the above pathways that are known to be hallmarks of HCC, and we also describe the influence of genetic variations in miRNA biosynthesis and genes.

A genetic variant in microRNA-122 regulatory region confers risk for chronic hepatitis B virus infection and hepatocellular carcinoma in Han Chinese

miR-122 plays a vital role in the development of chronic hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC). Based on data from the Encyclopedia of DNA Elements (ENCODE), two single nucleotide polymorphisms (SNPs), rs4309483 and rs4503880, were identified in the upstream regulatory region of miR-122. A case-control study consisting of 1,300 HBV-positive HCC cases, 1,344 HBV carriers, and 1,344 persons who cleared HBV naturally was carried out to test the association between the two SNPs and the risk for chronic HBV infection and HCC. The CA/AA genotypes of rs4309483 were associated with significantly increased risk for HCC [adjusted odds ratio (OR) = 1.21, 95% confidence intervals (CIs) = 1.02-1.43, P = 0.025] compared with HBV carriers, but decreased risk for chronic HBV infection (adjusted OR = 0.82, 95% CIs = 0.70-0.97, P = 0.017) compared with persons who cleared HBV naturally. The genotype-expression correlation between rs4309483 and the expression of primary or mature miR-122 expression was investigated in 29 pairs of HBV positive HCC and noncancerous liver tissues. In noncancerous liver tissues, subjects carrying the CA genotype exhibited significantly lower expression level of pri-miR-122 than those carrying the CC genotype. In addition, positive or inverse correlation between the expression levels of pri-miR-122 and mature miR-122 were observed in HCC tissues or noncancerous tissues, respectively. These findings indicate that the C to A base change of rs4309483 may alter the expression of miR-122, thus providing protective effect from chronic HBV infection but an increased risk for HCC in HBV carriers.

Functional interplay between hepatitis B virus X protein and human miR-125a in HBV infection

The hepatitis B virus (HBV) is a widespread human pathogen and chronic HBV infection is a major risk factor for hepatocellular carcinoma (HCC). Some cellular microRNAs are emerging as important regulators of virus-host interaction, indirectly or directly modulating HBV replication and pathogenesis. miR-125a binds the viral transcript encoding the surface antigen and interferes with its expression, thus inhibiting viral replication. Intriguingly, liver miR-125a expression has been found increased in patients with high levels of hepatic HBV-DNA. The present study investigates the mechanism by which liver exposure to HBV induces the expression of miR-125a. The analyses were first performed on liver biopsies from HBV patients, showing that the expression of the viral transactivator X protein (HBx) paralleled the increase of miR-125a expression. Then, transfection of HCC cell lines with an HBx-expressing vector showed a substantial increase of miR-125a expression. Overall, the available data depict a self-inhibitory feedback loop in which HBV, through HBx, increases the expression of miR-125a, that in turn interferes with expression of HBV surface antigen, thus repressing viral replication.

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

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

Next generation sequencing reveals microRNA isoforms in liver cirrhosis and hepatocellular carcinoma

Hepatocellular carcinoma (HCC) represents the major histological subtype of liver cancer. Tumorigenic changes in hepatic cells potentially result from aberrant expression of microRNAs (miRNAs). Individual microRNA gene may give rise to miRNAs of different length, named isomiRNAs that proved to be functionally relevant. Since microRNA length heterogeneity in hepatic tissue has not been described before, we employed next-generation sequencing to comprehensively analyze microRNA transcriptome in HCC tumors (n=24) and unaffected tissue adjacent to tumors (n=24), including samples with (n=15) and without cirrhosis (n=9). We detected 374 microRNAs expressed in liver, including miR-122-5p that constituted over 39% of the hepatic miRnome. Among the liver expressed miRs, the levels of 64 significantly differed between tumor and control samples (FDR<0.05, fold change>2). Top deregulated miRNAs included miR-1269a (T/N=22.95), miR-3144-3p (T/N=5.24), miR-183-5p (T/N=4.63), miR-10b-5p (T/N=3.87), miR-490-3p (T/N=0.13), miR-199a-5p (T/N=0.17), miR-199a-3p/miR-199b-3p (T/N=0.19), miR-214-5p (T/N=0.20) and miR-214-3p (T/N=0.21). Almost all miRNA genes produced several mature molecules differing in length (isomiRNAs). The reference sequence was not the most prevalent in 38.6% and completely absent in 10.5% of isomiRNAs. Over 26.1% of miRNAs produced isoforms carrying≥2 alternative seed regions, of which 35.5% constituted novel, previously unknown seeds. This fact sheds new light on the percentage of the human genome regulated by microRNAs and their variants. Among the most deregulated miRNAs, miR-199a-3p/miR-199b-3p (T/N fold change=0.18, FDR=0.005) was expressed in 9 isoforms with 3 different seeds, concertedly leading to upregulation of TGF-beta signaling pathway (OR=1.99; p=0.004). In conclusion, the study reveals the comprehensive miRNome of hepatic tissue and provides new tools for investigation of microRNA-dependent pathways in cirrhotic liver and hepatocellular carcinoma. This article is part of a Directed Issue entitled: Rare Cancers.

Association of miRNA-122-binding site polymorphism at the interleukin-1 α gene and its interaction with hepatitis B virus mutations with hepatocellular carcinoma risk

This study was designed to investigate the contribution of miRNA-122-binding site polymorphism at the IL-1A gene and its multiplicative interactions with hepatitis B virus (HBV) mutations in the risk of hepatocellular carcinoma (HCC). A total of 1021 healthy controls, 302 HBV surface antigen (HBsAg) seroclearance subjects, and 2011 HBsAg-positive subjects (including 1021 HCC patients) were enrolled in this study. Quantitative PCR was used to genotype rs3783553. HBV mutations were determined by direct sequencing. Multivariate logistic regression analyses were performed to test the associations of rs3783553, mutations, and their interactions with the risk of HCC. No significant association was found between rs3783553 and the risk of HCC among healthy controls, HBsAg seroclearance subjects, HBsAg-positive subjects without HCC, and all controls. Additionally, rs3783553 was not significantly associated with chronic HBV infection, liver cirrhosis, HBV e antigen seroconversion, abnormal alanine aminotransferase, and high viral load (> 10(4) copies/ml). However, the TTCA insertion allele of rs3783553 was significantly associated with an increased frequency of HBV C7A mutation compared with homozygous TTCA deletion carriers [(del/ins + ins/ins) vs. del/del, adjusted odds ratio (OR)= 1.48, 95% confidence interval (CI)= 1.09-2.02, P = 0.013]. Multiplicative interaction of rs3783553 with HBV preS deletion significantly reduced the risk of HCC in males, with an adjusted OR of 0.64 (95% CI = 0.42-0.98; P = 0.041) after age and HBV genotype were adjusted. Although rs3783553 did not significantly affect genetic susceptibility to HBV-related HCC, its variant allele may predispose the host to selecting HBV C7A mutation during evolution and significantly reduce the risk of HCC caused by HBV preS deletion. This study provides an insight into the complex host-virus interaction in HBV-induced hepatocarcinogenesis and is helpful in determining HBsAg-positive subjects who are likely to develop HCC.

Regulation of microRNAs and their role in liver development, regeneration and disease

Since their discovery more than a decade ago microRNAs have been demonstrated to have profound effects on almost every aspect of biology. Numerous studies in recent years have shown that microRNAs have important roles in development and in the etiology and progression of disease. This review is focused on microRNAs and the roles they play in liver development, regeneration and liver disease; particularly chronic liver diseases such as alcoholic liver disease, non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, viral hepatitis and primary liver cancer. The key microRNAs identified in liver development and chronic liver disease will be discussed together with, where possible, the target messenger RNAs that these microRNAs regulate to profoundly alter these processes. This article is part of a Directed Issue entitled: The Non-coding RNA Revolution.

Competitive virus and host RNAs: the interplay of a hidden virus and host interaction

During virus infection, viral RNAs and mRNAs function as blueprints for viral protein synthesis and possibly as pathogen-associated molecular patterns (PAMPs) in innate immunity. Here, considering recent research progress in microRNAs (miRNAs) and competitive endogenous RNAs (ceRNAs), we speculate that viral RNAs act as sponges and can sequester endogenous miRNAs within infected cells, thus cross-regulating the stability and translational efficiency of host mRNAs with shared miRNA response elements. This cross-talk and these reciprocal interactions between viral RNAs and host mRNAs are termed “competitive viral and host RNAs” (cvhRNAs). We further provide recent experimental evidence for the existence of cvhRNAs networks in hepatitis B virus (HBV), as well as Herpesvirus saimiri (HVS), lytic murine cytomegalovirus (MCMV) and human cytomegalovirus (HCMV) infections. In addition, the cvhRNA hypothesis also predicts possible cross-regulation between host and other viruses, such as hepatitis C virus (HCV), HIV, influenza virus, human papillomaviruses (HPV). Since the interaction between miRNAs and viral RNAs also inevitably leads to repression of viral RNA function, we speculate that virus may evolve either to employ cvhRNA networks or to avoid miRNA targeting for optimal fitness within the host. CvhRNA networks may therefore play a fundamental role in the regulation of viral replication, infection establishment, and viral pathogenesis.

Modulation of HBV replication by microRNA-15b through targeting hepatocyte nuclear factor 1α

Hepatitis B virus (HBV) infection remains a major health problem worldwide. The role played by microRNAs (miRNAs) in HBV replication and pathogenesis is being increasingly recognized. In this study, we found that miR-15b, an important miRNA during HBV infection and hepatocellular carcinoma development, directly binds hepatocyte nuclear factor 1α (HNF1α) mRNA, a negative regulator of HBV Enhancer I, to attenuate HNF1α expression, resulting in transactivation of HBV Enhancer I, in turn causing the enhancement of HBV replication and expression of HBV antigens, including HBx protein, finally leading to the down-regulated expression of miR-15b in both cell lines and mice in a long cascade of events. Our research showed that miR-15b promotes HBV replication by augmenting HBV Enhancer I activity via direct targeting HNF1α, while HBV replication and antigens expression, particularly the HBx protein, then repress the expression of miR-15b. The reciprocal regulation between miR-15b and HBV controls the level of HBV replication and might play a role in persistent HBV infection. This work adds to the body of knowledge concerning the complex interactions between HBV and host miRNAs.

Antitumor function of microRNA-122 against hepatocellular carcinoma

MicroRNA-122 (miR-122), a highly abundant and liver-specific miRNA, acts as a tumor suppressor against hepatocellular carcinoma (HCC). Decreased expression of miR-122 in HCC is frequently observed and is associated with poor differentiation, larger tumor size, metastasis and invasion, and poor prognosis. Mutant mice with knockout (KO) of the miR-122 locus developed steatohepatitis due to increased triglyceride (TG) synthesis and decreased TG secretion from hepatocytes, and eventually developed HCC. Exogenic miR-122 introduction into miR-122 KO mice inhibited the development of HCC. Target genes of miR-122, including cyclin G1, a disintegrin and metalloprotease (ADAM)10, serum response factor, insulin-like growth factor-1 receptor, ADAM17, transcription factor CUTL1, the embryonic isoform of pyruvate kinase (Pkm2), Wnt1, pituitary tumor-transforming gene 1 binding factor, Cut-like homeobox 1, and c-myc, are involved in hepatocarcinogenesis, epithelial mesenchymal transition, and angiogenesis. MiR-122 expression is regulated by liver-enriched transcription factors such as hepatocyte nuclear factor (HNF)1α, HNF3β, HNF4α, HNF6, and CCAAT/enhancer-binding protein (C/EBP)α. A positive feedback loop exists between C/EBPα and miR-122 and between HNF6 and miR-122, whereas a negative feedback loop exists between c-myc and miR-122. Since cotreatment of 5-Aza-Cd and histone deacetylase inhibitor restored miR-122 expression in HCC cells, epigenetic modulation of miR-122 expression is involved in the suppression of miR-122 in HCC. Several experiments suggest that increasing miR-122 levels in HCC with or without antitumor agents may be a promising strategy for HCC treatment.

Regulation of gene expression by microRNA in HCV infection and HCV-mediated hepatocellular carcinoma

MicroRNA (miRNA) exert a profound effect on Hepatitis C virus (HCV) replication and on the manifestation of HCV-associated hepatocellular carcinoma (HCC). miR-122 in particular, is highly enriched in liver and has been shown to interact with HCV, suggesting this virus has evolved to subvert and manipulate the host gene silencing machinery in order to support its life cycle. It is therefore likely that miR-122 and other miRNAs play an important role in the pathophysiology of HCV infection. The changes in post-transcriptional gene regulation by the miRNAs may play a key role in the manifestation of chronic liver disease and hepatocellular carcinoma. Understanding of HCV-host miRNA interactions will ultimately lead to the design of therapeutic modalities against HCV infection and HCV-mediated HCC and may also provide important biomarkers that direct treatment options. Here, we review the current knowledge on the role of miRNA and gene expression on HCV infection and hepatocellular carcinoma, in addition to the possible role of miRNA as future therapeutic targets.

HBx down-regulated Gld2 plays a critical role in HBV-related dysregulation of miR-122

miR-122 is a liver-rich-specific microRNA that plays an important role in hepatic gene expression via post-transcription regulation, and it is potentially associated with the development of hepatocellular carcinoma. It has been confirmed that miR-122 is down-regulated during HBV infection; however, how HBV affects miR-122 is still debated. One research provided evidence that HBx could reduce the miR-122 transcription level, but the other insisted that HBV had no significant effect on miR-122 transcription level but reduce miR-122 level via binding and sequestering endogenous miR-122. It is determinate that Gld2 could increase the specific miRNA stabilization by monoadenylation which was a post-transcription regulation. In this study, we aimed to investigate the mechanism of HBV-induced reduction of miR-122 and examine whether Gld2 is involved in it. According to the results of a microRNA microarray, we found miR-122 was the most down-regulated microRNA in HepG2.2.15 compared to HepG2. As revealed by qRT-PCR and western blotting analyses, both miR-122 and Gld2 levels were reduced in hepatic cell lines with expression of HBV or HBx but not other proteins of HBV, and over-expression of Gld2 could abolish the effect of HBV and HBx on the miR-122 level. What's more, both HBV and HBx have no significant effect on pre-miR-122 levels. And the dual-luciferase assay implicated that HBx could reduce the Gld2 promoter activity but had no significant effect on miR-122 promoter activity. In conclusion, HBx is a critical protein derived from HBV, which regulates miR-122 via down-regulating Gld2.

MicroRNAs: role and therapeutic targets in viral hepatitis

MicroRNAs regulate gene expression by binding to the 3'-untranslated region (UTR) of target messenger RNAs (mRNAs). The importance of microRNAs has been shown for several liver diseases, for example, viral hepatitis. MicroRNA-122 is highly abundant in the liver and is involved in the regulation of lipid metabolism. MicroRNA-122 is also an important host factor for the HCV and promotes HCV replication. In contrast to HCV, microRNA-122 inhibits replication of the HBV. MicroRNA-122 acts as a tumour suppressor and reduced levels of microRNA-122 are associated with hepatocellular carcinoma. MicroRNAs other than microRNA-122 have been linked to viral hepatitis, fibrosis and inflammation. In this review, we discuss function and clinical implications of microRNA-122 and other microRNAs in liver diseases, especially viral hepatitis.

Recent insights into hepatitis B virus-host interactions

Hepatitis B virus (HBV) poses a threat to global public health mainly because of complications of HBV-related chronic liver disease. HBV exhibits a narrow host range, replicating primarily in hepatocytes by a still poorly understood mechanism. For the generation of progeny virions, HBV depends on interactions with specific host factors through its life cycle. Revealing and characterizing these interactions are keys to identifying novel antiviral targets, and to developing specific treatment strategies for HBV patients. In this review, recent insights into the HBV-host interactions, especially on virus entry, intracellular trafficking, genome transcription and replication, budding and release, and even cellular restriction factors were reviewed.

Epirubicin directly promotes hepatitis B virus (HBV) replication in stable HBV-expressing cell lines: a novel mechanism of HBV reactivation following anticancer chemotherapy

Chronic hepatitis B virus (HBV) infection is a worldwide problem and HBV reactivation following anticancer chemotherapy has become an emerging clinical challenge. However, the mechanisms of HBV reactivation following chemotherapy remain unclear. Epirubicin is an anthracycline drug used in chemotherapy to treat numerous types of malignancy, including breast cancer, acute leukemia, malignant lymphoma, lung cancer, ovarian cancer and stomach cancer. Epirubicin acts by intercalating DNA strands and inhibiting DNA and RNA synthesis. In this study, it was demonstrated that epirubicin directly upregulated the levels of in vitro HBV replication in a concentration-dependent manner. Exposure to epirubicin for 24 h induced >11- and 6-fold increases in the levels of intracellular and secreted HBV DNA, respectively. In concordance with the elevated levels of HBV DNA, the expression levels of HBV pregenomic RNA, intracellular HBV surface and HBV core antigens, and secreted HBV e antigen were significantly increased by treatment with 0.5 µM epirubicin. Notably, epirubicin promoted cellular excretion of HBV nucleocapsids, which are closely associated with the pathological effects of HBV, including acute liver failure. In conclusion, epirubicin exhibited a direct stimulatory effect on HBV replication and this may be a novel mechanism of HBV reactivation following cytotoxic anticancer chemotherapy.

Genome-wide microarray-based analysis of miRNAs expression in patients with acute-on-chronic liver failure

BACKGROUND

Acute-on-chronic liver failure (ACLF) is a severe clinical syndrome that may cause a high mortality. However, the mechanism is still not clear. Characterization of the microRNA (miRNA) profiles in ACLF patients may provide new clues to the pathogenesis and management of this syndrome.

METHODS

Genome-wide microarray was performed to compare the different miRNA expression profiles in peripheral blood mononuclear cells of a pair of monozygotic twins, an ACLF patient and an HBV asymptomatic carrier (AsC). The case-control miRNA profiles were compared and confirmed by quantitative reverse transcription-polymerase chain reaction in 104 ACLF patients and 96 AsCs. A combined computational prediction algorithm was used to predict the potential target genes.

RESULTS

Forty-five miRNAs were increased and eight miRNAs were decreased in the ACLF group. The expressions of hsa-let-7a and hsa-miR-16 were increased by 8.58- and 8.63-fold in ACLF patients compared with that in AsCs, respectively (P<0.001). CARD8, BCL2, IL1RAPL1, LTB, FZD10 and EDA were identified as the target genes of hsa-miR-16; MAP4K3, OPRM1, IGF2BP1 and CERCAM were verified as the target genes of hsa-let-7a.

CONCLUSIONS

Our results showed that there is a close relationship between specific miRNAs of peripheral blood mononuclear cells and ACLF. hsa-miR-16 and hsa-let-7a may contribute to the development of ACLF.

Roadmap of miR-122-related clinical application from bench to bedside

INTRODUCTION

microRNA (miRNA) regulates target gene expression to influence many physiological and pathophysiological processes. The liver-specific miRNA, miR-122, contributes to liver function and plays a very important role in hepatic diseases including the viral hepatitis C (HCV). For this reason, developing an miR-122-related clinical application could be very useful in managing or treating many hepatic disorders.

AREAS COVERED

This review introduces the basic concepts of miRNA and miR-122. It also discusses the possibility of miR-122 as a biomarker and summarizes the results of anti-miR-122 treatment from basic research to a Phase IIa clinical trial. Furthermore, the authors discuss the potential opportunities and challenges found in clinical trials with miravirsen.

EXPERT OPINION

miR-122 may be a useful biomarker as both a diagnostic and prognostic tool. Furthermore, miravirsen is a novel treatment with great potential for hepatic disease treatment, especially in HCV. However, there is certainly the need for future investigations to better determine whether miR-122 is really specific for liver. It is also important to elucidate whether miR-122 is actually specific for HCV genome and further investigate the therapeutic potential of miravirsen. Only once these studies have been completed can anti-miR-122 treatment potentially enter the clinical practice.

MicroRNA profiles in graft preservation solution are predictive of ischemic-type biliary lesions after liver transplantation

BACKGROUND & AIMS

Ischemic-type biliary lesions (ITBL) are the second most common cause of graft loss after liver transplantation. Though the exact pathophysiology of ITBL is unknown, bile duct injury during graft preservation is considered to be a major cause. Here we investigated whether the release of cholangiocyte-derived microRNAs (CDmiRs) during graft preservation is predictive of the development of ITBL after liver transplantation.

METHODS

Graft preservation solutions (perfusates) and paired liver biopsies collected at the end of cold ischemia were analysed by RT-qPCR for CDmiR-30e, CDmiR-222, and CDmiR-296 and hepatocyte-derived miRNAs (HDmiRs) HDmiR-122 and HDmiR-148a. MicroRNAs in perfusates were evaluated on their stability by incubation and fractionation experiments. MicroRNA profiles in perfusates from grafts that developed ITBL (n=20) and grafts without biliary strictures (n=37) were compared.

RESULTS

MicroRNAs in perfusates were proven to be stable and protected against degradation by interacting proteins. Ratios between HDmiRs/CDmiRs were significantly higher in perfusates obtained from grafts that developed ITBL (p<0.01) and were identified as an independent risk factor by multivariate analysis (p<0.01, HR: 6.89). The discriminative power of HDmiRs/CDmiRs in perfusates was validated by analysis of separate brain death- (DBD) and cardiac death donors (DBD; p ≤ 0.016) and was superior to expression in liver biopsies (C=0.77 in perfusates vs. C<0.50 in biopsies).

CONCLUSIONS

This study demonstrates that differential release of CDmiRs during graft preservation is predictive of the development of ITBL after liver transplantation. This provides new evidence for the link between graft-related bile duct injury and the risk for later development of ITBL.

Hepatitis B surface antigen quantity positively correlates with plasma levels of microRNAs differentially expressed in immunological phases of chronic hepatitis B in children

Background and Aim

Children with chronic hepatitis B (CHB) are at high risk of progressive liver disease. It is suggested that a newly-identified panel of 16 microRNAs is important in the pathogenesis of CHB in children. Subviral hepatitis B surface antigen (HBsAg) particles are produced in large excess over infectious virions. Interestingly, circulating HBsAg particles have been shown to carry microRNAs. A thorough characterisation of the identified microRNAs and HBsAg over time in plasma from children with CHB may provide useful information about the natural course of childhood CHB.

Patients and Methods

A cohort of 42 children with CHB was followed over time. Three to five blood samples were obtained from each child at minimum intervals of half a year; in total 180 blood samples. Plasma levels of the 16 microRNAs previously identified were analysed by quantitative real-time polymerase-chain-reaction. Plasma HBsAg was quantified using ARCHITECT® HBsAg assay.

Results

The presence of 14/16 plasma microRNAs in children with CHB was confirmed. All 14 microRNAs were significantly differentially expressed in different immunological phases of the disease. MicroRNA plasma levels were highest in immune-tolerant children, lower in immune-active children, and reached the lowest values in immune-inactive children, p<0.001. Plasma levels of four microRNAs decreased significantly over time in immune-tolerant and immune-active children whereas the microRNA plasma levels were stable in immune-inactive children, p<0.004. HBsAg quantity was positively correlated with plasma levels of 11/14 microRNAs, p<0.004.

Conclusion

This is the first study to characterise plasma microRNAs and HBsAg over time in children with CHB. Our data suggest that plasma levels of selected microRNAs and HBsAg are inversely correlated with immunological control of CHB in children. Further studies are, however, needed to advance the understanding of microRNAs and HBsAg in the pathogenesis of CHB in children.

Roles of microRNAs in the hepatitis B virus infection and related diseases

The hepatitis B virus (HBV) is a small enveloped DNA virus that belongs to the Hepadnaviridae family. HBV can cause acute and persistent infection which can lead to hepatocellular carcinoma (HCC). MicroRNAs (miRNAs) play a crucial role in the main cellular events. The dysregulation of their expression has been linked to the development of the cancer as well as to viral interference. This chapter will describe the involvement of miRNAs in the case of HBV infection and their implication in the development of the HBV-related diseases.

Epigenetic regulation of MicroRNA-122 by peroxisome proliferator activated receptor-gamma and hepatitis b virus X protein in hepatocellular carcinoma cells

MicroRNA-122 (miR-122), a pivotal liver-specific miRNA, has been implicated in several liver diseases including hepatocellular carcinoma (HCC) and hepatitis C and B viral infection. This study aimed to explore epigenetic regulation of miR-122 in human HCC cells and to examine the effect of hepatitis C virus (HCV) and hepatitis B virus (HBV). We performed microRNA microarray analysis and identified miR-122 as the most up-regulated miRNA (6-fold) in human HCC cells treated with 5'aza-2'deoxycytidine (5-Aza-CdR, DNA methylation inhibitor) and 4-phenylbutyric acid (PBA, histone deacetylation inhibitor). Real-time polymerase chain reaction (PCR) analysis verified significant up-regulation of miR-122 by 5'aza and PBA in HCC cells, and to a lesser extent in primary hepatocytes. Peroxisome proliferator activated receptor-gamma (PPARγ) and retinoid X receptor alpha (RXRα) complex was found to be associated with the DR1 and DR2 consensus site in the miR-122 gene promoter which enhanced miR-122 gene transcription. 5-Aza-CdR and PBA treatment increased the association of PPARγ/RXRα, but decreased the association of its corepressors (N-CoR and SMRT), with the miR-122 DR1 and DR2 motifs. The aforementioned DNA-protein complex also contains SUV39H1, an H3K9 histone methyl transferase, which down-regulates miR-122 expression.

CONCLUSIONS

These findings establish a novel role of the PPARγ binding complex for epigenetic regulation of miR-122 in human HCC cells. Moreover, we show that hepatitis B virus X protein binds PPARγ and inhibits the transcription of miR-122, whereas hepatitis C viral particles exhibited no significant effect; these findings provide mechanistic insight into reduction of miR-122 in patients with HBV but not with HCV infection.

microRNA expression in hepatitis B virus infected primary treeshrew hepatocytes and the independence of intracellular miR-122 level for de novo HBV infection in culture

Infection of Hepatitis B virus (HBV) in hepatocytes has been known to be controlled by multiple cellular factors, while the relationship of the infection and liver microRNAs remains obscure. In this study, a miRNA database, containing 168 unique mature miRNA members from primary hepatocytes of a primate-like animal, northern treeshrew (Tupaia belangeri) that is the only species susceptible for HBV infection other than human and chimpanzee, was established. The relative level of a liver predominant microRNA, miR-122, was markedly increased upon HBV infection of the primary tupaia hepatocyte (PTH). However, introducing neither miR-122 nor its antagonist anti-miR-122 into PTHs, or, HepG2-NTCP that is HepG2 cells with the newly identified receptor sodium taurocholate cotransporting polypeptide (NTCP) did not alter the viral infection on these cells. These data suggest that de novo HBV infection of cultured hepatocytes does not depend on the expression level of intracellular miR-122 of the target cells.

Regulation of hepatitis B virus replication by epigenetic mechanisms and microRNAs

The hepatitis B virus (HBV) genome forms a covalently closed circular DNA (cccDNA) minichromosome that persists in the nucleus of virus-infected hepatocytes. HBV cccDNA serves as the template for viral mRNA synthesis and is subject to epigenetic regulation by several mechanisms, including DNA methylation and histone acetylation. Recently, microRNAs (miRNAs), a class of small non-coding RNAs, were also directly connected to the epigenetic machinery through a regulatory loop. Epigenetic modifications have been shown to affect miRNA expression, and a sub-group of miRNAs (defined as epi-miRNAs) can directly target effectors of the epigenetic machinery. In this review, we will summarize recent findings on the epigenetic mechanisms controlling HBV cccDNA function, primarily focusing on the epi-miRNA functions operating in HBV replication. Investigation of the epigenetic regulation of HBV replication may help to discover novel potential therapeutic targets for drug development with the goal to eradicate the HBV cccDNA pool in hepatocytes.

microRNA-122 abundance in hepatocellular carcinoma and non-tumor liver tissue from Japanese patients with persistent HCV versus HBV infection

Mechanisms of hepatic carcinogenesis in chronic hepatitis B and hepatitis C are incompletely defined but often assumed to be similar and related to immune-mediated inflammation. Despite this, several studies hint at differences in expression of miR-122, a liver-specific microRNA with tumor suppressor properties, in hepatocellular carcinoma (HCC) associated with hepatitis B virus (HBV) versus hepatitis C virus (HCV) infection. Differences in the expression of miR-122 in these cancers would be of interest, as miR-122 is an essential host factor for HCV but not HBV replication. To determine whether the abundance of miR-122 in cancer tissue is influenced by the nature of the underlying virus infection, we measured miR-122 by qRT-PCR in paired tumor and non-tumor tissues from cohorts of HBV- and HCV-infected Japanese patients. miR-122 abundance was significantly reduced from normal in HBV-associated HCC, but not in liver cancer associated with HCV infection. This difference was independent of the degree of differentiation of the liver cancer. Surprisingly, we also found significant differences in miR-122 expression in non-tumor tissue, with miR-122 abundance reduced from normal in HCV- but not HBV-infected liver. Similar differences were observed in HCV- vs. HBV-infected chimpanzees. Among HCV-infected Japanese subjects, reductions in miR-122 abundance in non-tumor tissue were associated with a single nucleotide polymorphism near the IL28B gene that predicts poor response to interferon-based therapy (TG vs. TT genotype at rs8099917), and correlated negatively with the abundance of multiple interferon-stimulated gene transcripts. Reduced levels of miR-122 in chronic hepatitis C thus appear to be associated with endogenous interferon responses to the virus, while differences in miR-122 expression in HCV- versus HBV-associated HCC likely reflect virus-specific mechanisms contributing to carcinogenesis. The continued expression of miR-122 in HCV-associated HCC may signify an important role for HCV replication late in the progression to malignancy.

Circulating microRNA-22 correlates with microRNA-122 and represents viral replication and liver injury in patients with chronic hepatitis B

Hepatitis B virus (HBV) infection is associated with increased expression of microRNA-122. Serum microRNA-122 and microRNA-22 levels were analyzed in 198 patients with chronic HBV who underwent liver biopsy and were compared with quantitative measurements of HBsAg, HBeAg, HBV DNA, and other clinical and histological findings. Levels of serum microRNA-122 and microRNA-22 were determined by reverse transcription-TaqMan PCR. Serum levels of microRNA-122 and microRNA-22 were correlated (R(2)  = 0.576; P < 0.001), and both were elevated in chronic HBV patients. Significant linear correlations were found between microRNA-122 or microRNA-22 and HBsAg levels (R(2)  = 0.824, P < 0.001 and R(2)  = 0.394, P < 0.001, respectively) and ALT levels (R(2)  = 0.498, P < 0.001 and R(2)  = 0.528, P < 0.001, respectively). MicroRNA-122 levels were also correlated with HBV DNA titers (R(2)  = 0.694, P < 0.001 and R(2)  = 0.421, P < 0.001). Levels of these microRNAs were significantly higher in HBeAg-positive patients compared to HBeAg-negative patients (P < 0.001 and P < 0.001). MicroRNA-122 levels were also lower in patients with advanced liver fibrosis (P < 0.001) and lower inflammatory activity (P < 0.025). These results suggest that serum micro-RNA levels are significantly associated with multiple aspects of HBV infection. The biological meaning of the correlation between microRNA-122 and HBsAg and should be investigated further.

MicroRNAs in Liver Disease: Bench to Bedside

MicroRNAs (miRs) are small non-coding RNAs that negatively regulate gene expression by pairing with partially complementary target sequences in the 3'UTRs of mRNAs to promote degradation and/or block translation. Aberrant miR expression is associated with development of multiple diseases including hepatic diseases. The role of miRs in the regulation of gene expression and rapid progress in the field of microRNA research are resulting in momentum toward development of diagnostic markers and novel therapeutic strategies for human liver diseases. Recent studies provide clear evidence that miRs are abundant in the liver and modulate a diverse spectrum of biological functions, thereby supporting an association between alterations of miR homeostasis and pathological liver diseases. Here we review the role of miRs in liver as their physiological and pathological importance has been demonstrated in metabolism, immunity, viral hepatitis, oncogenesis, fatty liver diseases (alcoholic and non-alcoholic), drug-induced liver injury, fibrosis as well as acute liver failure.

MicroRNAs may solve the mystery of chronic hepatitis B virus infection

Hepatitis B virus (HBV) infection is a global public health problem that causes persistent liver diseases such as chronic hepatitis, cirrhosis, and hepatocellular carcinoma. A large amount of people die annually from HBV infection. However, the pathogenesises of the HBV-related diseases are ill defined and the therapeutic strategies for the diseases are less than optimum. The recently discovered microRNAs (miRNAs) are tiny noncoding RNAs that regulate gene expression primarily at the post-transcriptional level by binding to mRNAs. miRNAs contribute to a variety of physiological and pathological processes. A number of miRNAs have been found to play a pivotal role in the host-virus interaction including host-HBV interaction. Numerous studies have indicated that HBV infection could change the cellular miRNA expression patterns and different stages of HBV associated disease have displayed distinctive miRNA profiles. Furthermore, the differential expressed miRNAs have been found involved in the progression of HBV-related diseases, for instance some miRNAs are involved in liver tumorigenesis and tumor metastasis. Studies have also shown that the circulating miRNA in serum or plasma might be a very useful biomarker for the diagnosis and prognosis of HBV-related diseases. In addition, miRNA-based therapy strategies have attracted increasing attention, indicating a promising future in the treatment of HBV-related diseases.

Cyclin G1 expands liver tumor-initiating cells by Sox2 induction via Akt/mTOR signaling

Recurrence and chemoresistance of liver cancer has been attributed to the existence of liver tumor-initiating cells (T-ICs). It is important to decipher the molecular mechanism for acquisition of drug resistance and to design combinatorial therapeutic strategies. Cyclin G1 has been shown to play a pivotal role in initiation and metastasis of hepatocellular carcinoma. In this study, we found that enhanced cyclin G1 expression was associated with drug resistance of hepatoma cells and higher recurrence rate in hepatocellular carcinoma patients. Expression of cyclin G1 was elevated in liver T-ICs and closely correlated with the expression of liver T-IC markers. Forced cyclin G1 expression remarkably enhanced self-renewal and tumorigenicity of hepatoma cells. Cyclin G1 overexpression dramatically upregulated the expression of Sox2 both in vitro and in vivo, which was impaired by chemical inhibitors of Akt/mTOR signaling. Furthermore, blockade of Akt/mTOR signaling or interference of Sox2 expression suppressed cyclin G1-enhanced self-renewal, chemoresistance, and tumorigenicity of hepatoma cells, indicating that cyclin G1 expands liver T-ICs through Sox2 induction via Akt/mTOR signaling pathway. These results suggest that cyclin G1-induced liver T-IC expansion contributes to the recurrence and chemoresistance of hepatoma, and cyclin G1 may be a promising biomarker for individualized therapy of hepatocellular carcinoma patients.

Increased expression of Gp96 by HBx-induced NF-κB activation feedback enhances hepatitis B virus production

Elevated expression of heat shock protein gp96 in hepatitis B virus (HBV)-infected patients is positively correlated with the progress of HBV-induced diseases, but little is known regarding the molecular mechanism of virus-induced gp96 expression and its impact on HBV infection. In this study, up-regulation of gp96 by HBV replication was confirmed both in vitro and in vivo. Among HBV components, HBV x protein (HBx) was found to increase gp96 promoter activity and enhance gp96 expression by using a luciferase reporter system, and western blot analysis. Further, we found that HBx-mediated regulation of gp96 expression requires a NF-κB cis-regulatory element on the gp96 promoter, and chromatin immunoprecipitation results demonstrated that HBx promotes the binding of NF-κB to the gp96 promoter. Significantly, both gain- and loss-of-function studies showed that gp96 enhances HBV production in HBV-transfected cells and a mouse model based on hydrodynamic transfection. Moreover, up-regulated gp96 expression was observed in HBV-infected patients, and gp96 levels were correlated with serum viral loads. Thus, our work demonstrates a positive feedback regulatory pathway involving gp96 and HBV, which may contribute to persistent HBV infection. Our data also indicate that modulation of gp96 function may represent a novel strategy for the intervention of HBV infection.

Cationic lipid nanoparticles for therapeutic delivery of siRNA and miRNA to murine liver tumor

miR-122, a liver-specific tumor suppressor microRNA, is frequently down-regulated in hepatocellular carcinoma (HCC). LNP-DP1, a cationic lipid nanoparticle formulation, was developed as a vehicle to restore deregulated gene expression in HCC cells by miR-122 delivery. LNP-DP1 consists of 2-dioleyloxy-N,N-dimethyl-3-aminopropane (DODMA), egg phosphatidylcholine, cholesterol and cholesterol-polyethylene glycol. In vitro, LNP-DP1-mediated transfection of a miR-122 mimic to HCC cells down-regulated miR-122 target genes by >95%. In vivo, siRNAs/miRNAs encapsulated in LNP-DP1 were preferentially taken up by hepatocytes and tumor cells in a mouse HCC model. The miR-122 mimic in LNP-DP1 was functional in HCC cells without causing systemic toxicity. To demonstrate its therapeutic potential, LNP-DP1 encapsulating miR-122 mimic was intratumorally injected and resulted in ~50% growth suppression of HCC xenografts within 30 days, which correlated well with suppression of target genes and impairment of angiogenesis. These data demonstrate the potential of LNP-DP1-mediated microRNA delivery as a novel strategy for HCC therapy.

FROM THE CLINICAL EDITOR

In this study, LNP-DP1 -a cationic lipid nanoparticle formulation -is reported as a vehicle to restore deregulated gene expression in hepatic carcinoma cells by siRNA and miRNA delivery using a mouse model. Further expansions to this study may enable transition to clinical trials of this system.

The L60V variation in hepatitis B virus core protein elicits new epitope-specific cytotoxic T lymphocytes and enhances viral replication

Mutations in the core protein (HBc) of hepatitis B virus (HBV) are associated with aggressive hepatitis and advanced liver diseases in chronic hepatitis B (CHB). In this study, we identified the L60V variation in HBc that generates a new HLA-A2-restricted CD8(+) T cell epitope by screening an overlapping 9-mer peptide pool covering HBc and its variants. The nonameric epitope V60 was determined by structural and immunogenic analysis. The HBc L60V variation is correlated with hepatic necroinflammation and higher viral levels, and it may be associated with a poor prognosis in CHB patients. Immunization with the defined HBV epitope V60 peptide elicited specific cytotoxic T lymphocyte (CTL)-induced liver injury in HLA-A2(+) HBV transgenic mice. In addition, in vitro and in vivo experiments both demonstrated that the HBc L60V variation facilitates viral capsid assembly and increases HBV replication. These data suggest that the HBc L60V variation can impact both HBV replication and HBV-specific T cell responses. Therefore, our work provides further dissection of the impact of the HBc L60V variation, which orchestrates HBV replication, viral persistence, and immunopathogenesis during chronic viral infection.

Hepatitis B viral RNA directly mediates down-regulation of the tumor suppressor microRNA miR-15a/miR-16-1 in hepatocytes

Hepatitis B virus (HBV) is a key risk factor for the development of hepatocellular carcinoma (HCC). Recent work suggests a functional link between HCC and microRNA expression, but the mechanism underlying the functional interaction between microRNA and HBV infection has remained largely elusive. Here we present evidence that the microRNA machinery serves as a defense system against HBV infection, which, in turn, reprograms the expression of specific microRNAs. We demonstrate a critical role of miR-15a/miR-16-1 in this functional interplay between microRNA and HBV infection, but in contrast to various indirect mechanisms mediated by viral proteins, we unexpectedly found that the HBx transcript directly triggers the down-regulation of miR-15a/miR-16-1 via the microRNA targeting sequences in the viral RNA. Because miR-15a and miR-16-1 are well known tumor suppressor microRNAs in multiple human cancers, our findings raise the intriguing possibility that viral RNA-mediated down-regulation of specific tumor suppressor microRNAs may contribute to HCC development in HBV-infected cells.

Differential plasma microRNA profiles in HBeAg positive and HBeAg negative children with chronic hepatitis B

BACKGROUND AND AIM

Children chronically infected with hepatitis B virus (HBV) are at high risk of progressive liver disease. However, no treatment is available that is consistently effective in curing chronic hepatitis B (CHB) in children. Improved understanding of the natural course of disease is warranted. Identification of specific microRNA (miRNA) profiles in children chronically infected with HBV may provide insight into the pathogenesis of CHB and lead to advances in the management of children with CHB.

PATIENTS AND METHODS

MiRNA PCR panels were employed to screen plasma levels of 739 miRNAs in pooled samples from HBeAg positive, HBeAg negative, and healthy children. The three groups' plasma miRNA profiles were compared, and aberrantly expressed miRNAs were identified. The identified miRNAs were then validated. Individual RT-qPCRs were performed on plasma from 34 HBeAg positive, 26 HBeAg negative, and 60 healthy children.

RESULTS

A panel of 16 plasma miRNAs were identified as aberrantly expressed in HBeAg positive and HBeAg negative children (p<0.001). Levels of all of the miRNAs were upregulated in HBeAg positive children compared with in HBeAg negative children. A positive correlation was furthermore found between plasma levels of the identified miRNAs and HBV DNA (p<0.001).

CONCLUSION

We are the first to investigate the plasma miRNA profile of children chronically infected with HBV. Our data indicates the existence of a relationship between abundance of circulating miRNAs and immunological stages in the natural course of disease. Certain miRNAs may contribute to the establishment and maintenance of CHB in children. Further studies are warranted to advance understanding of miRNAs in the pathogenesis of CHB, hopefully leading to the identification of future therapeutic targets.

Role of miR-122 and lipid metabolism in HCV infection

Hepatitis C virus (HCV) exhibits a narrow host range and a specific tissue tropism. Mice expressing major entry receptors for HCV permit viral entry, and therefore the species tropism of HCV infection is considered to be reliant on the expression of the entry receptors. However, HCV receptor candidates are expressed and replication of HCV-RNA can be detected in several nonhepatic cell lines, suggesting that nonhepatic cells are also susceptible to HCV infection. Recently it was shown that the exogenous expression of a liver-specific microRNA, miR-122, facilitated the efficient replication of HCV not only in hepatic cell lines, including Hep3B and HepG2 cells, but also in nonhepatic cell lines, including Hec1B and HEK-293T cells, suggesting that miR-122 is required for the efficient replication of HCV in cultured cells. However, no infectious particle was detected in the nonhepatic cell lines, in spite of the efficient replication of HCV-RNA. In the nonhepatic cells, only small numbers of lipid droplets and low levels of very-low-density lipoprotein-associated proteins were observed compared with findings in the hepatic cell lines, suggesting that functional lipid metabolism participates in the assembly of HCV. Taken together, these findings indicate that miR-122 and functional lipid metabolism are involved in the tissue tropism of HCV infection. In this review, we would like to focus on the role of miR-122 and lipid metabolism in the cell tropism of HCV.

MicroRNAs in Liver Health and Disease

MicroRNAs (miRNAs), a class of short non-coding RNAs, have been studied intensely and extensively in the past decade in every aspect of biological processes, including cell differentiation, proliferation and death. These findings pointed out the pivotal role of miRNA in posttranscriptional control of gene expression in animals and established miRNAs as therapeutic targets for different pathophysiological processes, including liver disease. Here we have discussed the recent advances made in identifying the miRNAs deregulated in different liver diseases such as obesity, hepatitis, alcoholic and nonalcoholic steatohepatitis, cirrhosis and hepatocellular carcinoma, as well as pathophysiological conditions such as developmental abnormality. We have specifically reviewed the role of miRNAs in these diseases and discussed critically potential impacts of these miRNAs as biomarkers and/or therapeutic targets in liver pathobiology in the clinical setting. Finally, we have highlighted the latest techniques or preclinical and/or clinical trials that are being developed to replenish or inhibit the deregulated miRNAs.

Circulating microRNAs: promising candidates serving as novel biomarkers of acute hepatitis

Acute liver failure as life threatening condition comprises a difficult diagnostic situation to evaluate potential outcomes and therapeutic options. Thus, prognostic indicators are urgently needed for evaluation of progression of liver injury, clinical outcome, prognosis, and for therapeutic response. Recently, circulating microRNA, in particular miR-122, was described as a potential biomarker of acute liver injury after intoxication of mice. Circulating microRNA (miRNA) molecules are very stable and RNase-resistant due to protein aggregation and vesicle enclosure. Since miRNA species are known to be associated with chronic liver damage or with liver cancer, circulating miRNA patterns are suggested to serve also as reporters for progression of acute liver failure. miRNA profiling analyses using PCR arrays or next generation sequencing, may achieve identification of miRNA species that are linked to the rapid progression of acute liver injury, to the outcome of liver failure, or to the therapeutic response. Therefore, circulating miRNAs are promising, non-invasive biomarkers of future diagnostic approaches. However, normalisation of circulating miRNA levels is essential and further standardisation of miRNA quantification assays is needed.

Can tobacco use promote HCV-induced miR-122 hijacking and hepatocarcinogenesis?

Chronic hepatitis C virus (HCV) infection is a well-recognized risk factor for hepatocellular carcinoma (HCC). As a co-risk factor, the role of tobacco use in HCV-driven carcinogenesis and relevant underlying mechanisms remain largely unclear. The latest discoveries about HCV replication have shown that HCV RNA hijacks cellular miRNA-122 by forming an Ago2-HCV-miR-122 complex that stabilizes the HCV genome and enhances HCV replication. Our previous work has demonstrated that aqueous tobacco smoke extract (TSE) is a potent activator of HIV replication via TSE-mediated viral protection from oxidative stress and activation of a set of genes that can promote viral replication. Since HCV is, like HIV, an enveloped virus that should be equally susceptible to lipid peroxidation, and since one of the TSE-upregulated genes, the DDX3 helicase, is known to facilitate HCV replication, we hypothesize that (1) tobacco use can similarly enhance HCV viability and replication, and promote HCC progression by up-regulation of DDX3, and (2) by competing for binding with miR-122 as a competing endogenous RNA (ceRNA), HCV replication can liberate miR-122's direct target, oncogenic gene cyclin G1 (CCNG1); furthermore, simultaneous tobacco use can synergistically enhance this competing effect via HCV upregulation. Our hypotheses may lay a foundation for better understanding of carcinogenesis in HCV-driven HCC and the potential role of tobacco as a cofactor. Disrupting the HCV ceRNA effect may provide a new strategy for designing anti HCV/HCC drugs.

Hepatitis B virus mRNA-mediated miR-122 inhibition upregulates PTTG1-binding protein, which promotes hepatocellular carcinoma tumor growth and cell invasion

As the most abundant liver-specific microRNA, miR-122 is involved in diverse aspects of hepatic function and neoplastic transformation. Our previous study showed that miR-122 levels are significantly decreased in hepatitis B virus (HBV)-infected patients, which may facilitate viral replication and persistence (S. Wang, L. Qiu, X. Yan, W. Jin, Y. Wang, L. Chen, E. Wu, X. Ye, G. F. Gao, F. Wang, Y. Chen, Z. Duan, and S. Meng, Hepatology 55:730-741, 2012). Loss of miR-122 expression in patients with hepatitis B enhances hepatitis B virus replication through cyclin G1-modulated P53 activity.). In this study, we provide evidence that all HBV mRNAs harboring an miR-122 complementary site act as sponges to bind and sequester endogenous miR-122, indicating that the highly redundant HBV transcripts are involved in HBV-mediated miR-122 suppression. We next identified pituitary tumor-transforming gene 1 (PTTG1) binding factor (PBF) as a target of miR-122 and demonstrated that HBV replication causes an obvious increase in PBF levels. Furthermore, we observed that the miR-122 levels were decreased and PBF was upregulated in chronic hepatitis B (CHB) and hepatocellular carcinoma (HCC). Overexpression and knockdown studies both revealed that PBF enhances proliferation and invasion of HCC cells, and silencing PBF resulted in a dramatic reduction of HCC tumor growth in vivo. Mechanistic analysis demonstrated that PBF interacts with PTTG1 and facilitates PTTG1 nuclear translocation, subsequently increasing its transcriptional activities. Therefore, we identified a novel HBV mRNA-miR-122-PBF regulatory pathway that facilitates malignant hepatocyte growth and invasion in CHB which may contribute to CHB-induced HCC development and progression. Our work underscores the reciprocal interplay of host miRNA sequestration and depletion by viral mRNAs, which may contribute to chronic-infection-related cancer.

Alcohol facilitates HCV RNA replication via up-regulation of miR-122 expression and inhibition of cyclin G1 in human hepatoma cells

BACKGROUND

Clinical studies demonstrate synergistic liver damage by alcohol and hepatitis C virus (HCV); however, the mechanisms by which alcohol promotes HCV infection remain obscure. The liver-specific microRNA-122 (miR-122) regulates HCV replication and expression of host genes, including Cyclin G1. Here, we hypothesized that alcohol regulates miR-122 expression and thereby modulates HCV RNA replication.

METHODS

The J6/JFH/Huh-7.5 model of HCV infection was used in this study. Real-time quantitative polymerase chain reaction, Western blotting, electrophoretic mobility shift assay, and confocal microscopy were used for experimental analysis.

RESULTS

We found that acute alcohol exposure (25 mM) significantly increased intracellular HCV RNA as well as miR-122 levels in Huh-7.5 and Huh-7.5/CYP2E1 expressing cells in the presence and absence of J6/JFH-HCV infection. Expression of the miR-122 target, Cyclin G1, was inhibited by alcohol both in J6/JFH-infected and uninfected Huh-7.5 cells. The use of a miR-122 inhibitor increased Cyclin G1 expression and prevented the alcohol-induced increase in HCV RNA and protein levels, suggesting a mechanistic role for alcohol-induced miR122 in HCV replication. We discovered that siRNA-mediated silencing of Cyclin G1 significantly increased intracellular HCV RNA levels compared with controls, suggesting a mechanistic role for Cyclin G1 in HCV replication. Alcohol-induced increase in miR-122 was associated with increased nuclear translocation and DNA binding of the nuclear regulatory factor-κB and could be prevented by NF-κB inhibition.

CONCLUSIONS

Our novel data indicate a miR-122-mediated mechanism for alcohol increasing HCV RNA replication. We show for the first time that Cyclin G1, a miR-122 target gene, has regulatory effects on HCV replication and that alcohol increases HCV replication by regulating miR-122 and Cyclin G1.