Down-regulated microRNA-152 induces aberrant DNA methylation in hepatitis B virus-related hepatocellular carcinoma by targeting DNA methyltransferase 1

Epigenetic alterations and microRNA misexpression in cancer and autoimmune diseases: a critical review

Epigenetic markers such as DNA methylation and histone modifications around promoter regions modify chromatin structure and regulate expression of downstream genes. In fact, aberrant epigenetic modifications are common events in human disease including tumorigenesis and autoimmunity. Small non-coding RNAs named microRNAs (miRNAs) are modulators of gene expression and play critical roles in various cellular processes. Several miRNAs have been characterized as tumor suppressors or oncogenes in cancer, and recent reports implicate certain miRNAs in the pathogenesis of autoimmune diseases. Epigenetic investigations have shown that distinct miRNAs are directly regulated by DNA methylation and histone modifications at their promoters. Moreover, miRNAs themselves are key participants in regulating the chromatin modifying machinery. Chromatin-modifying drugs such as DNA methylation inhibitors and histone deacetylase inhibitors have shown efficacy in human malignancies and there is some evidence that these drugs may be useful in autoimmune disease. The benefits of these drugs are at least partially mediated by restoring expression of epigenetically silenced tumor suppressor genes, including miRNAs. The complex layers regulating gene expression have yet to be fully elucidated, but it is clear that epigenetic alterations and miRNA misexpression are essential events in pathologic processes, especially cancer and autoimmune disease, and represent promising therapeutic targets.

Genetic and epigenetic alterations in hepatitis B virus-associated hepatocellular carcinoma

Hepatitis B virus (HBV) is a major cause of hepatocellular carcinoma (HCC). Its chronic infection can lead to chronic liver inflammation and the accumulation of genetic alterations to result in the oncogenic transformation of hepatocytes. HBV can also sensitize hepatocytes to oncogenic transformation by causing genetic and epigenetic changes of the host chromosomes. HBV DNA can insert into host chromosomes and recent large-scale whole-genome sequencing studies revealed recurrent HBV DNA integrations sites that may play important roles in the initiation of hepatocellular carcinogenesis. HBV can also cause epigenetic changes by altering the methylation status of cellular DNA, the post-translational modification of histones, and the expression of microRNAs. These changes can also lead to the eventual hepatocellular transformation. These recent findings on the genetic and epigenetic alterations of the host chromosomes induced by HBV opened a new avenue for the development of novel diagnosis and treatments for HBV-induced HCC.

Ursolic acid inhibited growth of hepatocellular carcinoma HepG2 cells through AMPKα-mediated reduction of DNA methyltransferase 1

Hepatocellular carcinoma (HCC), the major histological subtype of primary liver cancer, remains one of the most common malignancies worldwide. Due to the complicated pathogenesis of this malignancy, the outcome for comprehensive treatment is limited. Chinese herbal medicine (CHM) is emerging as a promising choice for its multi-targets and coordinated intervention effects against HCC. Ursolic acid (UA), a natural pentacyclic triterpenoid carboxylic acid found in CHM, exerts anti-tumor effects and is emerging as an effective compound for cancer prevention and therapy. However, the molecular mechanisms underlying the action of UA remain largely unknown. In this study, we showed that UA inhibited the growth of HCC cells and induced apoptosis in the dose- and time-dependent fashion. Furthermore, we found that UA induced phosphorylation of AMP-activated protein kinase alpha (AMPKα) and suppressed the protein expression of DNA methyltransferase 1 (DNMT1) in the dose-dependent manner. The inhibitor of AMPK, compound C blocked, while an activator of AMPK, metformin augmented the effect of UA on DNMT1 expression. In addition, UA suppressed the expression of transcription factor Sp1. Conversely, overexpression of Sp1 reversed the effect of UA on DNMT1 expression and cell growth. Collectively, our results show for the first time that UA inhibits growth of HCC through AMPKα-mediated inhibition of Sp1; this in turn results in inhibition of DNMT1. This study reveals a potential novel mechanism by which UA controls growth of HCC cells and suggests that DNMT1 could be novel target for HCC chemoprevention and treatment.

The "Macro" World of microRNAs in Hepatocellular Carcinoma

Hepatotropic viruses such as hepatitis B virus (HBV) and hepatitis C virus (HCV) are the major etiological agents associated with development of hepatocellular carcinoma (HCC). Progression of HCC is a multistep process that requires sequential or parallel deregulation of oncogenic and tumor suppressive pathways leading to chromosomal instability and neoplastic phenotype. In the recent years, microRNAs (miRNAs) have carved their own niche alongside oncogenes and tumor suppressors, owing to their innate ability to receive and relay multiple signals. Not surprisingly, miRNAs are fast emerging as central player in myriads of malignancies including HCC. miRNAs are reported to participate in initiation and progression of HCC, and have also been clinically correlated with risk assessment, disease grade, aggressiveness, and prognosis. Despite extensive data available on the role of miRNAs in HCC, there is a pressing need to integrate and evaluate these datasets to find its correlation, if any, with causal agents in order to devise novel interventional modalities. Through this review, we attempt to bridge the gap by consolidating the current knowledge and concepts in the field of HCC-related miRNAs with special emphasis on HBV and HCV. Further, we assess the potential of common as well as unique signatures that may be useful in developing novel biomarkers and therapeutics.

MicroRNA responses to environmental liver carcinogens: Biological and clinical significance

A large number of biological, chemical, and dietary factors have been implicated in the development of liver cancer. These involve complex and protracted interactions between genetic, epigenetic, and environmental factors. The survival rate for patients diagnosed with late-stage liver cancer is currently low due to the aggressive nature of the disease and resistance to therapy. An increasing body of evidence has offered support for the crucial role of non-coding microRNA (miRNA) in directing hepatic responses to environmental risk factors for liver cancer. In this review we focus on miRNA responses to environmental liver cancer risk factors and their potential biological and clinical significance.

Effects of miR-152 on cell growth inhibition, motility suppression and apoptosis induction in hepatocellular carcinoma cells

BACKGROUND

miR-152 is involved in the genesis and development of several malignancies. However, its role in HCC has not been fully clarified. The aim of this study was to investigate the clinicopathological significance of miR-152 and its effect on the malignant phenotype of HCC cells.

METHODS

miR-152 expression was detected using real-time quantitative RT-PCR in 89 pairs of HCC formalin-fixed paraffin-embedded and their adjacent tissues. Functionally, in vitro effects and mechanisms of action of miR-152 on proliferation, viability, caspase activity, apoptosis and motility were explored in HepG2, HepB3 and SNU449 cells, as assessed by spectrophotometry, fluorimetry, fluorescence microscopy, wound-healing and Western blotting, respectively.

RESULTS

miR-152 expression in HCC was downregulated remarkably compared to that in adjacent hepatic tissues. miR-152 levels in groups of advanced clinical stage, larger tumor size and positive HBV infection, were significantly lower than in other groups. A miR-152 mimic could suppress cell growth, inhibit cell motility and increase caspase activity and apoptosis in HCC cell lines. Furthermore, Western blotting showed that the miR-152 mimic downregulated Wnt-1, DNMT1, ERK1/2, AKT and TNFRS6B signaling. Intriguingly, inverse correlation of TNFRF6B and miR-152 expression was found in HCC and bioinformatics confirmed that TNFRF6B might be a target of miR- 152.

CONCLUSIONS

Underexpression of miR-152 plays a vital role in hepatocarcinogenesis and lack of miR-152 is related to the progression of HCC through deregulation of cell proliferation, motility and apoptosis. miR-152 may act as a tumor suppressor miRNA by also targeting TNFRSF6B and is therefore a potential candidate biomarker for HCC diagnosis, prognosis and molecular therapy.

Mir-152 inhibits cell proliferation and colony formation of CD133(+) liver cancer stem cells by targeting KIT

miR152 is involved in diverse biological functions and development of disease. This study investigates the role of mir-152 in cell proliferation and colony formation of liver cancer stem cells. We show that exogenous overexpression of mir-152 suppresses cell proliferation and colony formation in CD133(+) hep3B cells. We also show that KIT is a direct target of miR-152 and miR-152 downregulates protein expression of KIT by directly binding to 3' untranslated region of KIT. Downregulation of KIT by specific siRNAs inhibits proliferation and colony formation of CD133(+) hep3B cells, which is similar to inhibitory effects of miR-152. Moreover, exogenous expression of KIT compromises inhibitory effects of miR-152 on cell proliferation and colony formation. Our findings suggest that mir-152 inhibits cell proliferation and colony formation of CD133(+) hep3B cells by targeting KIT.

In situ DNA-templated synthesis of silver nanoclusters for ultrasensitive and label-free electrochemical detection of microRNA

On the basis of the use of silver nanoclusters (AgNCs) in situ synthesized by cytosine (C)-rich loop DNA templates as signal amplification labels, the development of a label-free and highly sensitive method for electrochemical detection of microRNA (miRNA-199a) is described. The target miRNA-199a hybridizes with the partial dsDNA probes to initiate the target-assisted polymerization nicking reaction (TAPNR) amplification to produce massive intermediate sequences, which can be captured on the sensing electrode by the self-assembled DNA secondary probes. These surface-captured intermediate sequences further trigger the hybridization chain reaction (HCR) amplification to form dsDNA polymers with numerous C-rich loop DNA templates on the electrode surface. DNA-templated synthesis of AgNCs can be realized by subsequent incubation of the dsDNA polymer-modified electrode with AgNO3 and sodium borohydride. With this integrated TAPNR and HCR dual amplification strategy, the amount of in situ synthesized AgNCs is dramatically enhanced, leading to substantially amplified current response for highly sensitive detection of miRNA-199a down to 0.64 fM. In addition, the developed method also shows high selectivity toward the target miRNA-199a. Featured with high sensitivity and label-free capability, the proposed sensing scheme can thus offer new opportunities for achieving sensitive, selective, and simple detection of different types of microRNA targets.

microRNAs and Hepatitis B

The hepatitis B virus (HBV) infection is the leading cause of persistent liver diseases, cirrhosis, and hepatocellular carcinoma (HCC). However, the precise mechanism underlying the development of HBV-related diseases is not fully understood. In addition, the therapeutic strategies for the diseases are less than optimum. microRNAs (miRNAs) are small noncoding RNAs that have been described as a "fine-tuner" in various cellular events. The dysregulation of miRNAs play a role in the development of the cancer as well as viral interference. Recent articles have demonstrated that several miRNAs are deregulated by HBV infection and contribute to viral replication and pathogenesis. Thus, it suggests that the precise mechanism between miRNA and HBV biology will be leading to the development of the novel diagnosis and therapy. This chapter aims to provide the basic principals of miRNAs in development of the HBV-related diseases. We also discuss about the possibility of miRNAs on the clinical application for diagnosis and therapy of HBV-related diseases.

Therapeutic microRNAs targeting the NF-kappa B signaling circuits of cancers

MicroRNAs (miRNAs) not only directly regulate NF-κB expression, but also up- or down-regulate NF-κB activity via upstream and downstream signaling pathways of NF-κB. In many cancer cells, miRNA expressions are altered accompanied with an elevation of NF-κB activity, which often plays a role in promoting cancer development and progression as well as hindering the effectiveness of chemo and radiation therapies. Thus NF-κB-targeting miRNAs have been identified and characterized as potential therapeutics for cancer treatment and sensitizers of chemo and radiotherapies. However, due to cross-targeting and instability of miRNAs, some limitations of using miRNA as cancer therapeutics still exist. In this review, the mechanisms for miRNA-mediated alteration of NF-κB expression and activation in different types of cancers will be discussed. The results of therapeutic use of NF-κB-targeting miRNA for cancer treatment will be examined. Some limitations, challenges and potential strategies in future development of miRNA as cancer therapeutics are also assessed.

miRNA in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer deaths worldwide. Despite improvements in HCC therapy, the prognosis for HCC patients remains poor due to a high incidence of recurrence. An improved understanding of the pathogenesis of HCC development would facilitate the development of more effective outcomes for the diagnosis and treatment of HCC at earlier stages. miRNA are small, endogenous, non-coding, ssRNA that are 21-30 nucleotides in length and modulate the expression of various target genes at the post-transcriptional and translational levels. Aberrant expression of miRNA is common in various human malignancies and modulates cancer-associated genomic regions or fragile sites. As for the relationship between miRNA and HCC, several studies have demonstrated that the aberrant expression of specific miRNA can be detected in HCC cells and tissues. However, little is known about the mechanisms of miRNA-related cell proliferation and development. In this review, we summarize the central and potential roles of miRNA in the pathogenesis of HCC and elucidate new possibilities that may be useful as diagnostic and prognostic markers, as well as novel therapeutic targets in HCC.

Epigenetic modifications in fibrotic diseases: implications for pathogenesis and pharmacological targets

Organ fibrosis is a complex and chronic disorder that results from a variety of acute injuries and contributes to thirty percent of naturally occurring deaths worldwide. The main feature of organ fibrosis is the excessive accumulation and deposit of extracellular matrix, thereby leading to organ dysfunction, loss of elasticity, and development of a rigid organ. Accumulating evidence shows that epigenetic remodeling, including aberrant DNA methylation and noncoding RNA expression as well as histone post-translational modifications, play important roles in the pathogenesis of fibrosis through the regulation of fibroblast activation, differentiation, and apoptosis, as well as collagen synthesis and profibrotic gene transcription. In this review, we discuss the basic regulation of DNA methylation, noncoding RNA expression, and histone post-translational modification, and their participation in the pathogenesis and development of organ fibrosis. This review also provides the latest insights into the novel biomarkers and therapeutic targets for fibrosis through modulation of epigenetic remodeling.

Possible role of tocopherols in the modulation of host microRNA with potential antiviral activity in patients with hepatitis B virus-related persistent infection: a systematic review

Hepatitis B virus (HBV) infection represents a serious global health problem and persistent HBV infection is associated with an increased risk of cirrhosis, hepatocellular carcinoma and liver failure. Recently, the study of the role of microRNA (miRNA) in the pathogenesis of HBV has gained considerable interest as well as new treatments against this pathogen have been approved. A few studies have investigated the antiviral activity of vitamin E (VE) in chronic HBV carriers. Herein, we review the possible role of tocopherols in the modulation of host miRNA with potential anti-HBV activity. A systematic research of the scientific literature was performed by searching the MEDLINE, Cochrane Library and EMBASE databases. The keywords used were 'HBV therapy', 'HBV treatment', 'VE antiviral effects', 'tocopherol antiviral activity', 'miRNA antiviral activity' and 'VE microRNA'. Reports describing the role of miRNA in the regulation of HBV life cycle, in vitro and in vivo available studies reporting the effects of VE on miRNA expression profiles and epigenetic networks, and clinical trials reporting the use of VE in patients with HBV-related chronic hepatitis were identified and examined. Based on the clinical results obtained in VE-treated chronic HBV carriers, we provide a reliable hypothesis for the possible role of this vitamin in the modulation of host miRNA profiles perturbed by this viral pathogen and in the regulation of some cellular miRNA with a suggested potential anti-HBV activity. This approach may contribute to the improvement of our understanding of pathogenetic mechanisms involved in HBV infection and increase the possibility of its management and treatment.

Serum miR-152, miR-148a, miR-148b, and miR-21 as novel biomarkers in non-small cell lung cancer screening

Lung cancer, predominantly by non-small cell lung cancer (NSCLC), is the leading cause of cancer-related deaths over the world. Late diagnosis is one of important reasons for high mortality rate in lung cancer. Current diagnostic approaches have disadvantages such as low accuracy, high cost, invasive procedure, etc. MicroRNAs were previously proposed as promising novel biomarkers in cancer screening. In this study, we evaluated the predictive power of four candidate miRNAs in NSCLC detection. Our study involved 152 NSCLC patients and 300 healthy controls. Blood samples were obtained from the total 452 subjects. After miRNA extraction from serum, the expression of miRNAs in cases and controls were quantified by qRT-PCR and normalized to the level of U6 small RNA. Statistical analyses were performed to compare miRNA levels between cases and controls. Stratified analyses were employed to compare miRNA levels in NSCLC patients with different clinical characteristics. Serum miR-148a, miR-148b, and miR-152 were significantly downregulated in NSCLC patients. However, overexpression of serum miR-21 was observed in NSCLC patients. The combination of four candidate miRNAs exhibited the highest predictive accuracy in NSCLC screening compared with individual miRNAs (AUC = 0.97). Low level of miRNA-148/152 members may associate with advanced stage, large tumor size, malignant cell differentiation, and metastasis. High expression of miR-21 was possibly correlated with large size tumor and advanced cancer stage. Our results showed the dysregulation of miR-148/152 family and miR-21 in NSCLC patients. Hence, the four candidate miRNAs have great potential to serve as promising novel biomarkers in NSCLC screening. Further large-scale studies are needed to validate our results.

HIV-1 Tat induces DNMT over-expression through microRNA dysregulation in HIV-related non Hodgkin lymphomas

BACKGROUND

A close association between HIV infection and the development of cancer exists. Although the advent of highly active antiretroviral therapy has changed the epidemiology of AIDS-associated malignancies, a better understanding on how HIV can induce malignant transformation will help the development of novel therapeutic agents.

METHODS

HIV has been reported to induce the expression of DNMT1 in vitro, but still no information is available about the mechanisms regulating DNMT expression in HIV-related B-cell lymphomas. In this paper, we investigated the expression of DNMT family members (DNMT1, DNMT3a/b) in primary cases of aggressive B-cell lymphomas of HIV-positive subjects.

RESULTS

Our results confirmed the activation of DNMT1 by HIV in vivo, and reported for the first time a marked up-regulation of DNMT3a and DNMT3b in HIV-positive aggressive B-cell lymphomas. DNMT up-regulation in HIV-positive tumors correlated with down-regulation of specific microRNAs, as the miR29 family, the miR148-152 cluster, known to regulate their expression. Literature reports the activation of DNMTs by the human polyomavirus BKV large T-antigen and adenovirus E1a, through the pRb/E2F pathway. We have previously demonstrated that the HIV Tat protein is able to bind to the pocket proteins and to inactivate their oncosuppressive properties, resulting in uncontrolled cell proliferation. Therefore, we focused on the role of Tat, due to its capability to be released from infected cells and to dysregulate uninfected ones, using an in vitro model in which Tat was ectopically expressed in B-cells.

CONCLUSIONS

Our findings demonstrated that the ectopic expression of Tat was per se sufficient to determine DNMT up-regulation, based on microRNA down-regulation, and that this results in aberrant hypermethylation of target genes and microRNAs. These results point at a direct role for Tat in participating in uninfected B-cell lymphomagenesis, through dysregulation of the epigenetical control of gene expression.

Genome-wide methylation profiling of the different stages of hepatitis B virus-related hepatocellular carcinoma development in plasma cell-free DNA reveals potential biomarkers for early detection and high-risk monitoring of hepatocellular carcinoma

BACKGROUND

An important model of hepatocellular carcinoma (HCC) that has been described in southeast Asia includes the transition from chronic hepatitis B infection (CHB) to liver cirrhosis (LC) and, finally, to HCC. The genome-wide methylation profiling of plasma cell-free DNA (cfDNA) has not previously been used to assess HCC development. Using MethylCap-seq, we analyzed the genome-wide cfDNA methylation profiles by separately pooling healthy control (HC), CHB, LC and HCC samples and independently validating the library data for the tissue DNA and cfDNA by MSP, qMSP and Multiplex-BSP-seq.

RESULTS

The dynamic features of cfDNA methylation coincided with the natural course of HCC development. Data mining revealed the presence of 240, 272 and 286 differentially methylated genes (DMGs) corresponding to the early, middle and late stages of HCC progression, respectively. The validation of the DNA and cfDNA results in independent tissues identified three DMGs, including ZNF300, SLC22A20 and SHISA7, with the potential for distinguishing between CHB and LC as well as between LC and HCC. The area under the curve (AUC) ranged from 0.65 to 0.80, and the odds ratio (OR) values ranged from 5.18 to 14.2.

CONCLUSIONS

Our data revealed highly dynamic cfDNA methylation profiles in support of HBV-related HCC development. We have identified a panel of DMGs that are predictive for the early, middle and late stages of HCC development, and these are potential markers for the early detection of HCC as well as the screening of high-risk populations.

miRNA and methylation: a multifaceted liaison

miRNAs and DNA methylation are both critical regulators of gene expression. Aberration in miRNA expression or DNA methylation is a causal factor for numerous pathological conditions. DNA methylation can inhibit the transcription of miRNAs, just like coding genes, by methylating the CpG islands in the promoter regions of miRNAs. Conversely, certain miRNAs can directly target DNA methyltransferases and bring about their inhibition, thereby affecting the whole genome methylation pattern. Recently, methylation patterns have also been revealed in mRNA. Surprisingly, the two most commonly studied methylation states in mRNA (m6A and m5C) are found to be enriched in 3'-UTRs (untranslated regions), the target site for the majority of miRNAs. Whereas m5C is reported to stabilise mRNA, m6A has a destabilising effect on mRNA. However, the effect of mRNA methylation on its interaction with miRNAs is largely unexplored. The review highlights the complex interplay between microRNA and methylation at DNA and mRNA level.

Association of a microRNA-323b polymorphism with the persistence of hepatitis B virus infection by the enhancement of viral replication

Recent studies have shown that some mammalian microRNAs (miRNAs) play a role in antiviral defence. However, little is known about the role of miRNA-323b in hepatitis B virus (HBV)-host interaction. We explored whether single nucleotide polymorphism (SNP) of miRNA-323b affects HBV replication in a Korean HBV cohort. Genotyping was performed in a total of 1439 subjects composed of 404 spontaneously recovered (SR) subjects as normal controls and 1035 chronic carriers (CC) of HBV who were further classified into 313 patients with chronic hepatitis, 305 patients with liver cirrhosis and 417 patients with hepatocellular carcinoma. To confirm the effect of SNP of miRNA-323b on HBV replication in vitro, HepAD38 cells were transfected with miRNA-323b wild type or miRNA-323b SNP plasmid vectors, and HBV replication was induced for 5 days. HBV DNA was isolated and quantified using real-time PCR. The polymorphism rs56103835C>T in the pre-miRNA region of miRNA-323b revealed significant minor allele frequency (0.273). rs56103835C>T SNP showed significantly affect persistence of HBV in CC group compared with SR group (OR = 1.29, P = 0.009 in a codominant model; OR = 1.29, P = 0.03 in a dominant model; and OR = 1.78, P = 0.03 in a recessive model). In vitro, the total intracellular HBV DNA content was significantly reduced by miRNA-323b wild-type plasmid vector transfection (P = 0.014). The polymorphism of miRNA-323b was significantly associated with persistence of HBV by the enhancement of HBV replication (P = 0.021). Our findings provide a novel perspective on the role SNP of miRNAs in host-virus interactions in HBV infection.

Global epigenetic regulation of microRNAs in multiple myeloma

Epigenetic changes frequently occur during tumorigenesis and DNA hypermethylation may account for the inactivation of tumor suppressor genes in cancer cells. Studies in Multiple Myeloma (MM) have shown variable DNA methylation patterns with focal hypermethylation changes in clinically aggressive subtypes. We studied global methylation patterns in patients with relapsed/refractory MM and found that the majority of methylation peaks were located in the intronic and intragenic regions in MM samples. Therefore, we investigated the effect of methylation on miRNA regulation in MM. To date, the mechanism by which global miRNA suppression occurs in MM has not been fully described. In this study, we report hypermethylation of miRNAs in MM and perform confirmation in MM cell lines using bisulfite sequencing and methylation-specific PCR (MSP) in the presence or absence of the DNA demethylating agent 5-aza-2'-deoxycytidine. We further characterized the hypermethylation-dependent inhibition of miR-152, -10b-5p and -34c-3p which was shown to exert a putative tumor suppressive role in MM. These findings were corroborated by the demonstration that the same miRNAs were down-regulated in MM patients compared to healthy individuals, alongside enrichment of miR-152-, -10b-5p, and miR-34c-3p-predicted targets, as shown at the mRNA level in primary MM cells. Demethylation or gain of function studies of these specific miRNAs led to induction of apoptosis and inhibition of proliferation as well as down-regulation of putative oncogene targets of these miRNAs such as DNMT1, E2F3, BTRC and MYCBP. These findings provide the rationale for epigenetic therapeutic approaches in subgroups of MM.

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.

The impact of hepatitis B virus x protein and microRNAs in hepatocellular carcinoma: a comprehensive analysis

microRNAs (miRNAs) are evolutionarily conserved small non-coding RNAs, approximately 22 nucleotides (nts) in length, widely found in animals, plants, and viruses. Mature miRNAs control gene expression at a post-transcriptional level through blocking protein translation or inducing mRNA degradation. Many recent studies have shown that hepatitis B virus x protein (HBx), a viral protein with a crucial role in hepatogenesis, is associated with the regulation of miRNAs. This interaction impacts fundamental tumor processes, such as cell proliferation, differentiation, and apoptosis. In this review, we summarized the recent literature on the roles of HBx-regulated miRNAs in the pathogenesis of hepatocellular carcinoma.

Epigenetics in liver disease

Epigenetics is a term that encompasses a variety of regulatory processes that are able to crosstalk in order to influence gene expression and cell phenotype in response to environmental cues. A deep understanding of epigenetics offers the potential for fresh insights into the basis for complex chronic diseases and improved diagnostic and prognostic tools. Moreover, as epigenetic modifications are highly plastic and responsive to the environment, there is much excitement around the theme of epigenetic therapeutics, including not only new drugs but also more informed patient advice on lifestyle choices and their impact on pathology. This review briefly explains the molecular nature of the individual regulatory process that constitute epigenetics, including DNA methylation, histone modifications, chromatin remodeling, transcriptional control, and noncoding RNAs. The ways in which these epigenetic mechanisms influence liver physiology and disease will be considered in detail, particularly in the context of cancer, fibrosis, and nonalcoholic steatohepatitis. The current limitations associated with epigenetic profiling and therapeutics in liver disease are discussed, as is the intriguing possibility that environmental-induced epigenetic changes may become stable and heritable.

CONCLUSION

The aim of the review is to inform hepatologists of the emerging key epigenetic ideas of relevance to liver diseases that are highly likely to form a component of patient management and care in the next decade.

The potential role of epigenetic modifications in the heritability of multiple sclerosis

It is now well established that both genetic and environmental factors contribute to and interact in the development of multiple sclerosis (MS). However, the currently described causal genetic variants do not explain the majority of the heritability of MS, resulting in 'missing heritability'. Epigenetic mechanisms, which principally include DNA methylation, histone modifications and microRNA-mediated post-transcriptional gene silencing, may contribute a significant component of this missing heritability. As the development of MS is a dynamic process potentially starting with inflammation, then demyelination, remyelination and neurodegeneration, we have reviewed the dynamic epigenetic changes in these aspects of MS pathogenesis and describe how environmental risk factors may interact with epigenetic changes to manifest in disease.

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.

MiR-152 functions as a tumor suppressor in glioblastoma stem cells by targeting Krüppel-like factor 4

Glioblastoma (GBM) is the most common central nervous system tumor and the molecular mechanism driving its development is still largely unknown, limiting the treatment of this disease. In the present study, we explored the potential role of miR-152 in glioblastoma stem cells (GSCs) as well as the possible molecular mechanisms. Our results proved that miR-152 was down-regulated in human GSCs. Restoring the expression of miR-152 dramatically reduced the cell proliferation, cell migration and invasion as well as inducing apoptosis. Mechanistic investigations defined Krüppel-like factor 4 (KLF4) as a direct and functional downstream target of miR-152, which was involved in the miR-152-mediated tumor-suppressive effects in GSCs. Meanwhile, this process was coincided with the down-regulated LGALS3 that could be bound and promoted by KLF4, leading to attenuate the activation of MEK1/2 and PI3K signal pathways. Moreover, the in vivo study showed that miR-152 over-expression and KLF4 knockdown produced the smallest tumor volume and the longest survival in nude mice. Taken together, these results elucidated the function of miR-152 in GSCs progression and suggested a promising application of it in glioma treatment.

Epigenetic therapy as a novel approach in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common type of liver malignancy and one with high fatality. Its 5-year survival rate remains low and thus, there is a need for improvement of current treatment strategies as well as development of novel targeted methodologies in order to optimize existing therapeutic protocols. To this end, only recently, it was discovered that its pathophysiology also involves epigenetic alterations in DNA methylation, histone modifications and/or non-coding microRNA patterns. Unlike genetic events, epigenetic alterations are reversible and thus potentially considered to be an alternative option in cancer treatment protocols. In this review, we describe the general characteristics and resulted major alterations of the epigenetic machinery as well as current state of progress of epigenetic therapy (via different single or combinatorial experimental approaches) in HCC.

MiR-152 suppresses the proliferation and invasion of NSCLC cells by inhibiting FGF2

MicroRNAs (miRNAs) regulate the proliferation and metastasis of cancer cells. Here, we showed that miR-152 was downregulated in non-small-cell lung cancer (NSCLC) tissues and cell lines. Overexpression of miR-152 suppressed cell proliferation and colony formation and also limited migration and invasion. Fibroblast growth factor 2 (FGF2) was confirmed as a direct target of miR-152. FGF2 knockdown suppressed cell proliferation, colony formation, migration and invasion, whereas FGF2 overexpression partially reversed the suppressive effect of miR-152. Furthermore, the presence of miR-152 was inversely correlated with FGF2 in NSCLC tissues. Overall, this study demonstrated that miR-152 suppressed the proliferation and invasion of NSCLC cells by downregulating FGF2. These findings provide novel insights with potential therapeutic applications for the treatment of NSCLC.

MicroRNA-152 modulates the canonical Wnt pathway activation by targeting DNA methyltransferase 1 in arthritic rat model

Rheumatoid arthritis (RA) is an autoimmune and progressive systemic disease of unknown etiology. Research shows that fibroblast-like synoviocytes (FLS) participate in the cartilage erosion, synovial hyperplasia, inflammatory cytokine secretion and suggests that fibroblast-like synoviocytes (FLS) display a crucial role in RA pathogenesis. Recent studies have suggested the role of the Wnt signaling pathway in the pathogenesis of RA. In previous study, we identified that increased methyl-CpG-binding protein 2 (MeCP2) reduced the secreted frizzled-related protein 4 (SFRP4) expression in FLS in Arthritic rat model and the DNA methyltransferase (DNMT) inhibitor 5-Aza-2'-deoxycytidine (5-azadC) could induce the SFRP4 expression, indicating that DNMT has a key role in the differential expression of SFRP4. MicroRNAs (MiRNAs), which are small non-coding RNAs, are involved in diverse biological functions, regulation of gene expression, pathogenesis of autoimmune disease and carcinogenesis. In light of the directly down-regulation of miR-152 on DNMT1 expression by targeting the 3' untranslated regions of its transcript in nickel sulfide (NiS)-transformed human bronchial epithelial cells, we investigated whether miR-152 is aberrantly expressed and targets DNMT1 in FLS in Arthritic rat model. Our results demonstrated that the expression of miR-152 was specifically down-regulated in Arthritic rat model, whereas up-regulation of miR-152 in FLS resulted in a marked reduction of DNMT1 expression. Further experiments revealed that increased miR-152 indirectly up-regulated the SFRP4 expression, a negative regulator of WNT signaling pathway, by targeting the DNMT1. Moreover, activation of miR-152 expression in FLS could inhibit the canonical Wnt pathway activation and result in a significant decrease of FLS proliferation. MiR-152 and DNA methylation may provide molecular mechanisms for the activation of canonical Wnt pathway in RA. Combination of miR-152 and DNMT1 may be a promising treatment strategy for RA patients in which SFRP4 is inactivated.

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.

MicroRNAs as Mediators of the Ageing Process

Human ageing is a complex and integrated gradual deterioration of cellular processes. There are nine major hallmarks of ageing, that include changes in DNA repair and DNA damage response, telomere shortening, changes in control over the expression and regulation of genes brought about by epigenetic and mRNA processing changes, loss of protein homeostasis, altered nutrient signaling, mitochondrial dysfunction, stem cell exhaustion, premature cellular senescence and altered intracellular communication. Like practically all other cellular processes, genes associated in features of ageing are regulated by miRNAs. In this review, I will outline each of the features of ageing, together with examples of specific miRNAs that have been demonstrated to be involved in each one. This will demonstrate the interconnected nature of the regulation of transcripts involved in human ageing, and the role of miRNAs in this process. Definition of the factors involved in degeneration of organismal, tissue and cellular homeostasis may provide biomarkers for healthy ageing and increase understanding of the processes that underpin the ageing process itself.

Hepatitis B virus, HBx mutants and their role in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of death induced by cancer in the modern world and majority of the cases are related to chronic hepatitis B virus (HBV) infection. HBV-encoded X protein (HBx) is known to play a pivotal role in the pathogenesis of viral induced HCC. HBx is a multifunctional protein of 17 kDa which modulates several cellular processes by direct or indirect interaction with a repertoire of host factors resulting in HCC. HBX might interfere with several cellular processes such as oxidative stress, DNA repair, signal transduction, transcription, protein degradation, cell cycle progression and apoptosis. A number of reports have indicated that HBx is one of the most common viral ORFs that is often integrated into the host genome and its sequence variants play a crucial role in HCC. By mutational or deletion analysis it was shown that carboxy terminal of HBx has a likely role in protein-protein interactions, transcriptional transactivation, DNA repair, cell, signaling and pathogenesis of HCC. The accumulated evidence thus far suggests that it is difficult to understand the mechanistic nature of HBx associated HCC, and HBx mediated transcriptional transactivation and signaling pathways may be a major determinant. This article addresses the role of HBx in the development of HCC with particular emphasis on HBx mutants and their putative targets.

Advances in research of miR-148a in gastric cancer

Gastric cancer is one of the most frequent malignancies of the digestive system, and its incidence is on the rise in recent years. Surgical resection is the preferred treatment for gastric cancer. However, the rate of diagnosis of early gastric cancer is not high, and the quality of survival and 5-year survival rate of gastric cancer patients are low. MicroRNAs are a class of small non-coding RNAs that have been demonstrated to participate in tumor occurrence and development. The role of miR-148a in gastric cancer has received increasing attention in recent years, which offers a new possibility for the diagnosis and treatment of gastric cancer. This review summarizes the advances in understanding the role of miR-148a in gastric cancer.

MicroRNA-152 regulates DNA methyltransferase 1 and is involved in the development and lactation of mammary glands in dairy cows

MicroRNAs (miRNAs) are a class of small non-coding, endogenous regulatory RNAs that function by controlling gene expression at the post-transcriptional level. Using small RNA sequencing and qRT-PCR techniques, we found that the expression of miR-152 was significantly increased during lactation in the mammary glands of dairy cows producing high quality milk compared with that in cows producing low quality milk. Furthermore, DNA methyltransferase 1 (DNMT1), which is a target of miR-152, was inversely correlated with the expression levels of miR-152 in the mammary glands of dairy cows. Dairy cow mammary epithelial cells (DCMECs) were used as in vitro cell models to study the function of miR-152. The forced expression of miR-152 in DCMECs resulted in a marked reduction of DNMT1 at both mRNA and protein levels. This in turn led to a decrease in global DNA methylation and increased the expression of two lactation-related genes, serine/threonine protein kinase Akt (Akt) and peroxisome proliferator-activated receptor gamma (Pparγ). In contrast, inhibition of miR-152 showed the opposite results. By using an electronic Coulter counter (CASY-TT) and flow cytometer, we discovered that miR-152 enhanced the viability and multiplication capacity of DCMECs. In conclusion, miR-152 plays an important role in the development and lactation processes in the mammary glands of dairy cows. Our data provide insights into dairy cow mammary gland development and lactation.

Aberrant DNA methylation in hepatocellular carcinoma tumor suppression (Review)

Aberrant DNA methylation leads to altered gene expression, resulting in cancerous features. Numerous tumor suppressor genes are silenced by DNA methylation during hepatocarcinogenesis. Promoter CpG island hypermethylation is an important mechanism for inactivating tumor suppressor genes in hepatocellular carcinoma (HCC). Hypermethylation of CpG islands in the p16 (INK4a) and p15 (INK4b) promoters may increase the risk of developing HCC, particularly hepatitis B virus-related HCC. Environmental factors can lead to geographic variations in the methylation status of CpG islands. Aberrant DNA methylation of CpG islands is catalyzed by DNA methyltransferases (DNMTs). Thus, abnormal variations of DNMTs can contribute to hepatocarcinogenesis. In hepatitis-related HCC, microRNAs participate in hepatocarcinogenesis by directly targeting DNMTs, during which hepatitis B virus X acts as a regulator. DNA methylation may also contribute to HCC tumorigenesis by regulating the cell cycle. Based on the importance of DNA methylation in tumor suppression of HCC, certain DNA methylations may predict the risk of tumor development, tumor staging, patient survival and HCC recurrence.

MicroRNA-148b expression is decreased in hepatocellular carcinoma and associated with prognosis

MicroRNAs are small non-coding RNA molecules that have been shown to regulate the expression of genes linked to cancer. MicroRNA-148a (miR-148a) has recently been found to be involved in many critical processes in human malignancies. The present study is to clarify the expression pattern and prognostic role of miR-148b in human hepatocellular carcinoma (HCC). The expression of miR-148b was detected in 156 cases of HCC and 36 cases of normal control specimens by real-time PCR. Results showed that miR-148b expression was significantly decreased in HCC compared with that in normal control. It was also demonstrated that aberrant miR-148b expression was associated with vein invasion and TNM stage of HCC. Kaplan-Meier analysis showed that decreased miR-148b expression was associated with poor overall survival of patients. A multivariate survival analysis also indicated that miR-148b could be an independent prognostic marker. These results proved that miR-148b expression was decreased in HCC and associated with tumor invasion and progression. The present study also provides the first evidence that miR-148b could be an independent prognostic factor for patients with HCC, indicating the potential role of miR-148b as a prognostic marker in clinical practice, and the inhibition of miR-148b may even become a new therapeutic method for the treatment of HCC.

Downregulation of miR-101-3p by hepatitis B virus promotes proliferation and migration of hepatocellular carcinoma cells by targeting Rab5a

RAB GTPase 5A (RAB5A), a member of the Rab subfamily of small GTPases, acts as an oncogene and has been associated with various key cellular functions, including cell growth, differentiation, apoptosis and angiogenesis. Recently, it has been reported that the Rab5a gene is involved in the progression of cancer. Hepatocellular carcinoma (HCC) is one of the most common and aggressive cancers, and it is usually associated with persistent hepatitis B virus (HBV) infections. Emerging evidence suggests that HBV alters microRNA (miRNA) expression profiles, but the mechanisms underlying this process have not yet been fully elucidated. Here, we examine how HBV affects the production of miR-101-1, which has been shown to be downregulated in HCC. We found that HBV could repress miR-101-3p by inhibiting its promoter activity. Downregulation of miR-101-3p promoted cancer cell growth and migration, and a specific miR-101-3p inhibitor was able to enhance proliferation and migration. Moreover, we identified Rab5a was one of the target genes of miR-101-3p in HBV-related HCC. Forced expression of miR-101-3p in liver cell lines resulted in a marked reduction of the expression of Rab5a at both the mRNA and protein level by directly targeting the 3'untranslated region of Rab5a. Overexpression of Rab5a resulted in a reversal of the suppression of proliferation and migration of SMMC-7721 cells mediated by miR-101-3p. Taken together, our data show that HBV can downregulate miR-101-3p expression by inhibiting its promoter activity and that downregulation of miR-101-3p promotes HCC cell proliferation and migration by targeting Rab5a. This provides new insights into the mechanisms of HBV-related HCC pathogenesis.

Hepatitis B virus-induced hepatocellular carcinoma

Many factors are considered to contribute to hepatitis B virus (HBV) associated hepatocellular carcinoma (HCC), including products of HBV, HBV integration and mutation, and host susceptibility. HBV X protein (HBx) can interfere with several signal pathways that associated with cell proliferation and apoptosis, and the impact of HBx C-terminal truncation in the development of HCC has been implicated. Recent studies by advanced sequencing technologies have revealed recurrent HBV DNA integration sites in hepatoma cells and susceptible genes/SNPs play an important role in the pathogenesis of liver cancer. Epigenetic changes, immune and inflammatory factors are also important contributing factors for liver cancer. This mini-review provides an overview on the recent development of HBV induced HCC.

MicroRNA-148a is silenced by hypermethylation and interacts with DNA methyltransferase 1 in hepatocellular carcinogenesis

In general, microRNAs, a class of small (~21 nucleotide) non-coding RNAs, negatively regulate the expression of their target genes. Dysregulation of miRNAs is a common feature in human cancers, but this phenomenon has not been studied extensively in hepatocellular carcinoma (HCC). miR‑148a, a member of the miR-148/152 family, has been found to be downregulated in several tumor types and has been suggested to be a tumor suppressor gene; however, its function in HCC remains unclear. Herein, we describe the epigenetic regulation of miR-148a and its impact on HCC cells. We found that, due to the hypermethylation of its CpG island, miR-148a undergoes methylation-mediated silencing in HCC cell lines. Additionally, DNMT1, the DNA methyltransferase that maintains methylation patterns, is aberrantly upregulated in HCC cell lines, and its overexpression is responsible for hypermethylation of the miR-148a promoter. Intriguingly, the expression of DNMT1, which is a target of miR-148a, is inversely correlated with the expression of miR-148a in HCC cells. These results lead us to propose the existence of a negative feedback regulatory loop between miR-148a and DNMT1 in HCC. Importantly, we demonstrate that the overexpression of miR-148a significantly inhibits HCC cell proliferation and cell cycle progression. Our results suggest the existence of a novel miR-148a-DNMT1 regulatory circuit and indicate that miR-148a acts as a tumor suppressor during hepatocellular carcinogenesis. These results may provide a promising alterative strategy for the therapeutic treatment of HCC.

Functional analysis of miR-101-3p and Rap1b involved in hepatitis B virus-related hepatocellular carcinoma pathogenesis

MicroRNA-101(miR-101) has been shown to be down-regulated in hepatocellular carcinoma (HCC). The hepatitis B virus (HBV) is a major risk factor in the development and progression of HCC. However, the correlation between HBV and miR-101 has not yet been fully elucidated. In this study, we reported that HBV could repress miR-101-3p by inhibiting its promoter activity and identified the potential effects of miR-101-3p on some important biological properties of HCC cells by targeting Rap1b. Dual-luciferase reporter assays showed that HBV down-regulated miR-101-3p by inhibiting its promoter activity. Down-regulation of miR-101-3p promoted cell proliferation, migration, and reduced apoptosis, and resulted in up-regulation of Rap1b, while overexpression of miR-101-3p inhibited these processes. Moreover, overexpression of Rap1b was able to reverse the suppressed cell proliferation and migration mediated by miR-101-3p. Our data showed that HBV down-regulated miR-101-3p expression by inhibiting its promoter activity, which resulted in up-regulation of Rap1b, and down-regulation of miR-101-3p or up-regulation of Rap1b promoted proliferation and migration of HCC cells. This provides a new understanding of the mechanism of HBV-related HCC pathogenesis and the potential application of miR-101-3p in cancer therapy.

Identification of the collagen type 1 α 1 gene (COL1A1) as a candidate survival-related factor associated with hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is one of the major causes of cancer-related death especially among Asian and African populations. It is urgent that we identify carcinogenesis-related genes to establish an innovative treatment strategy for this disease.

Methods

Triple-combination array analysis was performed using one pair each of HCC and noncancerous liver samples from a 68-year-old woman. This analysis consists of expression array, single nucleotide polymorphism array and methylation array. The gene encoding collagen type 1 alpha 1 (COL1A1) was identified and verified using HCC cell lines and 48 tissues from patients with primary HCC.

Results

Expression array revealed that COL1A1 gene expression was markedly decreased in tumor tissues (log₂ ratio –1.1). The single nucleotide polymorphism array showed no chromosomal deletion in the locus of COL1A1. Importantly, the methylation value in the tumor tissue was higher (0.557) than that of the adjacent liver tissue (0.008). We verified that expression of this gene was suppressed by promoter methylation. Reactivation of COL1A1 expression by 5-aza-2′-deoxycytidine treatment was seen in HCC cell lines, and sequence analysis identified methylated CpG sites in the COL1A1 promoter region. Among 48 pairs of surgical specimens, 13 (27.1%) showed decreased COL1A1 mRNA expression in tumor sites. Among these 13 cases, 10 had promoter methylation at the tumor site. The log-rank test indicated that mRNA down-regulated tumors were significantly correlated with a poor overall survival rate (P = 0.013).

Conclusions

Triple-combination array analysis successfully identified COL1A1 as a candidate survival-related gene in HCCs. Epigenetic down-regulation of COL1A1 mRNA expression might have a role as a prognostic biomarker of HCC.

Multilayer-omics analyses of human cancers: exploration of biomarkers and drug targets based on the activities of the International Human Epigenome Consortium

Epigenetic alterations consisting mainly of DNA methylation alterations and histone modification alterations are frequently observed in cancers associated with chronic inflammation and/or persistent infection with viruses or other pathogenic microorganisms, or with cigarette smoking. Accumulating evidence suggests that alterations of DNA methylation are involved even in the early and precancerous stages. On the other hand, in patients with cancers, aberrant DNA methylation is frequently associated with tumor aggressiveness and poor patient outcome. Recently, epigenome alterations have been attracting a great deal of attention from researchers who are focusing on not only cancers but also neuronal, immune and metabolic disorders. In order to accurately identify disease-specific epigenome profiles that could be potentially applicable for disease prevention, diagnosis and therapy, strict comparison with standard epigenome profiles of normal tissues is indispensable. However, epigenome mechanisms show heterogeneity among tissues and cell lineages. Therefore, it is not easy to obtain a comprehensive picture of standard epigenome profiles of normal tissues. In 2010, the International Human Epigenome Consortium (IHEC) was established to coordinate the production of reference maps of human epigenomes for key cellular states. In order to gain substantial coverage of the human epigenome, the IHEC has set an ambitious goal to decipher at least 1000 epigenomes within the next 7–10 years. We consider that pathway analysis using genes showing multilayer-omics abnormalities, including genome, epigenome, transcriptome, proteome and metabolome abnormalities, may be useful for elucidating the molecular background of pathogenesis and for exploring possible therapeutic targets for each disease.

The role of microRNAs in hepatocarcinogenesis: current knowledge and future prospects

MicroRNAs (miRNAs) are small, noncoding RNA molecules that regulate gene expression post-transcriptionally through complementary base pairing with thousands of messenger RNAs. Although the precise biological functions of individual miRNAs are still unknown, miRNAs are speculated to play important roles in diverse biological processes through fine regulation of their target gene expression. A growing body of data indicates the deregulation of miRNAs during hepatocarcinogenesis. In this review, we summarize recent findings regarding deregulated miRNA expression and their possible target genes in hepatocarcinogenesis, with emphasis on inflammation-related hepatocarcinogenesis. Because miRNA-based strategies are being applied to clinical therapeutics, precise knowledge of miRNA functions is crucial both scientifically and clinically. We discuss the current open questions from these points of view, which must be clarified in the near future.

Modifiable risk factors in periodontal disease: epigenetic regulation of gene expression in the inflammatory response

Epigenetics as a modifiable risk factor in periodontal diseases has been investigated in light of the current knowledge of how chronic infection and inflammation can affect gene-specific epigenetic reprogramming in periodontal tissues. Epigenomic programming might be particularly sensitive to environmental influences, and a combination of physiological stressors and environmental exposures appears to affect the epigenomic program acquired by a cell during differentiation and throughout the cellular lineage lifespan. Viral and bacterial infections can establish several types of epigenetic modifications, which sometimes engage in a complex epigenetic crosstalk also reflecting in the establishment and progress of periodontal diseases. The inflammatory and metabolic states of the periodontal tissues are driven by the infectious stimuli, and the magnitude of the cellular and molecular signature response is further dictated by the host genetic and epigenetic traits associated with various systemic exposures, including smoking, obesity and diabetes/hyperglycemia. This review discusses the advances in epigenetics, focusing on the role of DNA methylation in the pathogenesis of periodontal disease and the potential of epigenetic therapy.

HCV core protein-induced down-regulation of microRNA-152 promoted aberrant proliferation by regulating Wnt1 in HepG2 cells

BACKGROUND

Hepatitis C virus (HCV) has been reported to regulate cellular microRNAs (miRNAs). The HCV core protein is considered to be a potential oncoprotein in HCV-related hepatocellular carcinoma (HCV-HCC), but HCV core-regulated miRNAs are largely unknown. Our preliminary experiments revealed significant down-regulation of microRNA-152 (miR-152) by HCV core protein in HepG2 cells. Through target gene prediction softwares, Wnt1 was predicted to be a potential target of miR-152. The present study was initiated to investigate whether miR-152 is aberrantly regulated by the HCV core protein, and involved in the regulation of the aberrant proliferation of HCV-HCC cells.

METHODS

MiR-152 levels were examined by stem-loop real-time RT-PCR (SLqRT-PCR). Cell proliferation was analyzed by MTT and colony formation assay. Cell cycle analysis was performed by flow cytometry. Luciferase reporter assay was conducted to confirm miRNA-target association. Wnt1 expression was determined by real-time qPCR and Western blotting.

RESULTS

HCV core protein significantly suppressed miR-152 expression, and led to significant Wnt1 up-regulation with a concomitant aberrantly promoted proliferation. Moreover, we validated that miR-152 inhibition promoted, while miR-152 mimics inhibited cell proliferation. Using, qRT-PCR and western blot, Wnt1 was demonstrated to be regulated by miR-152. Luciferase activity assay showed that while miR-152 mimics significantly reduced the luciferase activity by 83.76% (P<0.0001), miR-152 inhibitor showed no effect on luciferase reporter. Most notably, salvage expression of miR-152 after Ad-HCV core infection for 24 h almost totally reversed the proliferation-promoting effect of the HCV core protein, and meanwhile, reduced the expression of both Wnt1 mRNA and protein to basal levels.

CONCLUSION

These findings provide important evidence that the reduced miR-152 expression by HCV core protein can indirectly lose an inhibitory effect on Wnt1, which might, at least partially lead to cell proliferation of liver cancer cells. MiR-152 may have a therapeutic potential to suppress liver cancer proliferation.