MicroRNA gene expression profile of hepatitis C virus-associated hepatocellular carcinoma

Small molecules with big effects: the role of the microRNAome in cancer and carcinogenesis

Small non-coding RNAs-microRNAs, are potent negative regulators of gene expression. MicroRNAs are involved in multiple biological processes, metabolic regulation, including cell proliferation, differentiation, and programmed cell death. Since the dysregulation of these processes is a hallmark of cancer, microRNAs can be viewed as major contributors to the pathogenesis of cancer, including initiation and progression of cancer. This review focuses on microRNA biogenesis and function, and their role in cancer, metastasis, drug resistance, and tumorigenesis.

The let-7 family of microRNAs inhibits Bcl-xL expression and potentiates sorafenib-induced apoptosis in human hepatocellular carcinoma

BACKGROUND & AIMS

Bcl-xL, an anti-apoptotic member of the Bcl-2 family, is over-expressed in human hepatocellular carcinoma, conferring a survival advantage to tumour cells. The mechanisms underlying its dysregulation have not been clarified. In the present study, we explored the involvement of microRNAs that act as endogenous sequence-specific suppressors of gene expression.

METHODS

The expression profiles of microRNAs in Huh7 hepatoma cells and primary human hepatocytes were compared by microarray analysis. The effect of let-7 on Bcl-xL expression was examined by Western blot and a reporter assay. The involvement of let-7 microRNAs in human tissues was analysed by western blot and reverse transcription-PCR.

RESULTS

Microarray analysis, followed by in silico target prediction, identified let-7 microRNAs as being downregulated in Huh7 hepatoma cells in comparison with primary human hepatocytes, as well as possessing a putative target site in the bcl-xl mRNA. Over-expression of let-7c or let-7g led to a clear decrease of Bcl-xL expression in Huh7 and HepG2 cell lines. Reporter assays revealed direct post-transcriptional regulation involving let-7c or let-7g and the 3'-untranslated region of bcl-xl mRNA. Human hepatocellular carcinoma tissues with low expression of let-7c displayed higher expression of Bcl-xL protein than those with high expression of let-7c, suggesting that low let-7 microRNA expression contributes to Bcl-xL over-expression. Finally, expression of let-7c enhanced apoptosis of hepatoma cells upon exposure to sorafenib, which downregulates expression of another anti-apoptotic Bcl-2 protein, Mcl-1.

CONCLUSIONS

let-7 microRNAs negatively regulate Bcl-xL expression in human hepatocellular carcinomas and induce apoptosis in cooperation with an anti-cancer drug targeting Mcl-1.

Down-regulation of microRNA 10a expression in esophageal squamous cell carcinoma cells

This study identified significantly down-regulated microRNAs (miRs) specific for esophageal squamous cell carcinoma (ESCC) cells. Total RNA was extracted from ESCC cell lines (OE21 and TE10) and a non-malignant human esophageal squamous cell line (Het1A), and subjected to microarray analysis. Expression levels of miRs that showed significant down-regulation in ESCC cells compared to Het1A cells based on the comprehensive analysis were analyzed by quantitative reverse transcription polymerase chain reaction. Among the significantly down-regulated miRs, miR-10a expression levels in the five ESCC cell lines examined were significantly lower than in Het1A and the esophageal adenocarcinoma cells. Since miR-10a is a specific miR in ESCC, its clinical relevance was examined. Using ESCC tumor samples and non-cancerous tissue obtained endoscopically, the involvement of miR-10a in the clinicopathological findings was examined. MiR-10a expression was comparably down-regulated in the tumors of high-grade intraepithelial neoplasm and non-invasive ESCC, while the expression levels were elevated in the invasive ESCC tumors. Treatment with a demethylating agent, 5-aza-2'-deoxycytidine, restored miR-10a expression in OE21 cells. Only a modest additive or synergistic effect was observed in the presence of a histone deacetylase inhibitor, trichostatin A. These results imply that miR-10a may be differentially expressed in ESCC cells and may be involved in ESCC development and progression. The unique epigenetic regulation of miR-10a expression can be mediated via hypermethylation of the CpG islands proximal to its gene locus, at least in certain ESCC cells.

Micro-RNAs and breast cancer

Micro-RNAs (miRs) are a recently described class of genes, encoding small non-coding RNA molecules, which primarily act by down-regulating the translation of target mRNAs. miRs are involved in a range of normal physiological processes, notably differentiation and cell type determination. It has become apparent that they are also key factors in cancer, playing both oncogenic and tumour-suppressing roles. We discuss here what is known of miR biology in the normal breast, and of their emerging roles in breast cancer.

MicroRNA-15b represents an independent prognostic parameter and is correlated with tumor cell proliferation and apoptosis in malignant melanoma

MicroRNAs (miRNAs) are small noncoding RNAs ( approximately 22 bp) that posttranscriptionally regulate gene expression. MiRNAs possess oncogenic or tumor suppressor activity in various tumors but little is known about miRNA expression pattern in malignant melanoma. We determined the expression level of 16 potentially relevant miRNAs (miR-15a, miR-15b, miR-16, miR-34a, miR-210, let-7I, miR-23a, miR-23b, miR-24, miR-27a, miR-27b, miR-100, miR-137, miR-222, miR-373-1, miR-373*) by real-time PCR in 6 preparations of normal melanocytes vs. 10 melanoma cell lines and in formalin fixed paraffin embedded tissue of 11 melanocytic nevi versus 16 melanomas. MiR-15b and miR-210 were significantly upregulated, miR-34a was significantly downregulated in melanomas compared with melanocytic nevi. These 3 miRNAs were analyzed in a total of 128 primary melanomas from patients with detailed clinical follow-up information. High expression of miR-15b (but not miR-210 upregulation and miR-34a downregulation) was significantly associated with poor recurrence free survival and overall survival by univariate Kaplan-Meier and multivariate Cox analyses. Downregulation of miR-15b in two melanoma cell lines with high miR-15b expression by transfection with anti-miR-15b siRNA was associated with reduced tumor cell proliferation, whereas apoptosis was increased. In summary, miRNA expression levels show distinct differences comparing benign and malignant melanocytic cell proliferations and can provide independent prognostic informations. MiR-15b appears to represent a particular important miRNA in melanoma that is associated with poor prognosis and tumorigenesis.

Viral hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is the fifth most common cancer and the third leading cause of cancer death worldwide. Despite recent advances in the diagnosis and treatment of HCC, its prognosis remains dismal. Infection with hepatitis B virus (HBV) and hepatitis C virus (HCV) are the major risk factors for HCC. Although both are hepatotropic viral infections, there are important differences between the oncogenic mechanisms of these two viruses. In addition to the oncogenic potential of its viral proteins, HBV, as a DNA virus, can integrate into host DNA and directly transform hepatocytes. In contrast, HCV, an RNA virus, is unable to integrate into the host genome, and viral protein expression has a more critical function in hepatocarcinogenesis. Both HBV and HCV proteins have been implicated in disrupting cellular signal transduction pathways that lead to unchecked cell growth. Most HCC develops in the cirrhotic liver, but the linkage between cirrhosis and HCC is likely multifactorial. In this review, we summarize current knowledge regarding the pathogenetic mechanisms of viral HCC.

Down-regulation of Dicer in hepatocellular carcinoma

Dicer, the key enzyme in the RNAi pathway, is misregulated in tumor tissues. The altered expression of Dicer is associated with clinical characteristics in patients with cancer. Liver carcinoma and adjacent non-neoplastic tissues were obtained from 36 patients with hepatocellular carcinoma (HCC) undergoing surgery. Expressions of Dicer mRNA were evaluated using the Real-time reverse transcription-PCR in 36 liver carcinoma tissues and 36 adjacent histologically non-cancerous liver tissues. Dicer mRNA levels were evaluated in relation to age, sex, tumor number, tumor size, tumor stage, and distant metastasis. Dicer mRNA level was significantly lower in malignant tissues than in the corresponding non-neoplastic tissues in 34 of the 36 patients with HCC (94.4%). The Dicer expression level was not associated with clinical characteristics, including age, sex, tumor number, tumor size, tumor stage, or distant metastasis in HCC cases. These results demonstrate that Dicer is significantly down-regulated in HCC, suggesting that reduced expression of Dicer may play an important role during the process of hepatocarcinogenesis.

Association of a variant in MIR 196A2 with susceptibility to hepatocellular carcinoma in male Chinese patients with chronic hepatitis B virus infection

MicroRNAs (miRNAs) are small noncoding RNAs with regulatory functions as tumor suppressors and oncogenes. Recent studies have implicated that the rs11614913 SNP in MIR196A2 was associated with susceptibility of lung cancer, congenital heart disease, breast cancer and shortened survival time of nonsmall cell lung cancer. To assess whether this polymorphism is associated with susceptibility to and clinicopathologic characteristics of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC), a total of 560 patients with chronic HBV infection and 391 healthy volunteers were enrolled, and MIR196A2 polymorphism was genotyped by polymerase chain reaction-ligation detection reaction (PCR-LDR). In our study group, there was no significant association between MIR196A2 polymorphism and the risk of HBV-related HCC in all subjects, however, the risk of HCC was significantly higher with MIR196A2 rs11614913 CC genotype or C allele compared with those with the TT genotype or T allele in male patients. Furthermore, in a subsequent analysis of the association between this polymorphism and clinicopathologic characteristics, there was still no significant difference in both the distribution of genotype or allelic frequency. However, we observed that the T allele was significantly more frequent in male HCC patients with lymphatic metastasis. Our results suggested that MIR196A2 polymorphism was associated with susceptibility to HBV-related HCC in a male Chinese population.

Emerging role of microRNAs in liver diseases

MicroRNAs are a class of small non-coding RNAs that are found in plants, animals, and some viruses. They modulate the gene function at the post-transcriptional level and act as a fine tuner of various processes, such as development, proliferation, cell signaling, and apoptosis. They are associated with different types and stages of cancer. Recent studies have shown the involvement of microRNAs in liver diseases caused by various factors, such as Hepatitis C, Hepatitis B, metabolic disorders, and by drug abuse. This review highlights the role of microRNAs in liver diseases and their potential use as therapeutic molecules.

miR-10a contributes to retinoid acid-induced smooth muscle cell differentiation

MicroRNAs (miRs) have been reported to play a critical role in muscle differentiation and function. The purpose of this study is to determine the role of miRs during smooth muscle cell (SMC) differentiation from embryonic stem cells (ESCs). MicroRNA profiling showed that miR-10a expression is steadily increased during in vitro differentiation of mouse ESCs into SMCs. Loss-of-function approaches using miR-10a inhibitors uncovered that miR-10a is a critical mediator for SMC lineage determination in our retinoic acid-induced ESC/SMC differentiation system. In addition, we have documented for the first time that histone deacetylase 4 is a novel target of miR-10a and mediates miR-10a function during ESC/SMC differentiation. To determine the molecular mechanism through which retinoic acid induced miR-10a expression, a consensus NF-kappaB element was identified in the miR-10a gene promoter by bioinformatics analysis, and chromatin immunoprecipitation assay confirmed that NF-kappaB could bind to this element. Finally, inhibition of NF-kappaB nuclear translocation repressed miR-10a expression and decreased SMC differentiation from ESCs. Our data demonstrate for the first time that miR-10a is a novel regulator in SMC differentiation from ESCs. These studies suggest that miR-10a may play important roles in vascular biology and have implications for the diagnosis and treatment of vascular diseases.

Hepatitis C virus proteins modulate microRNA expression and chemosensitivity in malignant hepatocytes

PURPOSE

Hepatocellular cancer (HCC) is highly resistant to chemotherapy and is associated with poor prognosis. Chronic hepatitis C virus (HCV) infection is a major cause of HCC. However, the effect of viral proteins in mediating chemosensitivity in tumor cells is unknown. We postulated that HCV viral proteins could modulate therapeutic responses by altering host cell microRNA (miRNA) expression.

EXPERIMENTAL DESIGN

HepG2 malignant hepatocytes were stably transfected with full-length HCV genome (Hep-394) or an empty vector (Hep-SWX). MiRNA profiling was done by using a custom microarray, and the expression of selected miRNAs was validated by real-time PCR. Protein expression was assessed by Western blotting, whereas caspase activation was assessed by a luminometric assay.

RESULTS

The IC(50) to sorafenib was lower in Hep-394 compared with Hep-SWX control cells. Alterations in miRNA expression occurred with 10 miRNAs downregulated >2-fold and 23 miRNAs upregulated >2-fold in Hep-394 cells compared with controls. Of these, miR-193b was overexpressed by 5-fold in Hep-394 cells. miR-193b was predicted to target Mcl-1, an antiapoptotic protein that can modulate the response to sorafenib. The expression of Mcl-1 was decreased, and basal caspase-3/7 activity and poly ADP ribose polymerase cleavage were increased in Hep-394 cells compared with controls. Moreover, transfection with precursors to miR-193b decreased both Mcl-1 expression and the IC(50) to sorafenib.

CONCLUSIONS

Cellular expression of full-length HCV increases sensitivity to sorafenib by the miRNA-dependent modulation of Mcl-1 and apoptosis. Modulation of miRNA responses may be a useful strategy to enhance response to chemotherapy in HCC.

Involvement of miR-199a downregulation in the preventive effects of Jianpi Jiedu Recipe against experimental hepatocarcinoma in rats

AIM: To investigate the preventive effects of Jianpi Jiedu Recipe against diethylnitrosamine-induced hepatocarcinoma in rats and explore the involvement of miR-199a downregulation in this process.

METHODS: Male Wistar rats were randomly divided into three groups: normal control group (n = 25), model group (n = 40 ) and prevention group (n = 40). The normal control group was given normal saline [10 mL/(kg•d) ig] for 12 weeks, the model group was given diethylnitrosamine dissolved in drinking water (80 ppm) at a dose of 8 mg/(kg•d) for the same duration, and the prevention group was given both diethylnitrosamine at the same dose and Jianpi Jiedu Recipe [17.5 g/(kg•d), ig] for the same duration. Five rats in each group were executed at weeks 4, 8, 12 and 16, respectively, and the remaining rats were killed at week 20. Meanwhile, the mortality, incidence of ascites, and liver and spleen index were measured. Hematoxylin-eosin staining (HE) was used to examine hepatic pathological changes. The expression of miR-199a mRNA was detected by real-time reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS: At week 20, the mortality rate and the incidence rate of ascites were 0% and 0% in the normal control group, 42.5% and 87.5% in the model group, and 17.5% and 44.4% in the prevention group, respectively. The mortality rate and the incidence of ascites were significantly lower in the prevention group than in the model group (both P < 0.05). At week 16, the incidence of HCC was 100% in both the model group and prevention group and 0% in the normal control group, the incidence of grade III liver cancer was 100% (5/5) in the model group, and the incidences of grade I, II and III liver cancer were 40% (2/5), 40% (2/5 ) and 20% (1/5) in the prevention group, respectively. Compared with the model group, the liver and spleen index in the prevention group were significantly reduced at all time points (all P < 0.01). Real-time RT-PCR results showed that the expression of miR-199a was significantly upregulated in the model group. However, miR-199a expression was significantly downregulated in the prevention group at all time points except at week 16 (all P < 0.01).

CONCLUSION: Jianpi Jiedu Recipe has good preventive effects against hepatocarcinoma in rats perhaps partly by downregulating miR-199a expression.

Current knowledge of MicroRNAs and noncoding RNAs in virus-infected cells

Within the past few years, microRNAs (miRNAs) and other noncoding RNAs (ncRNAs) have emerged as elements with critically high importance in posttranscriptional control of cellular and, more recently, viral processes. Endogenously produced by a component of the miRNA-guided RNA silencing machinery known as Dicer, miRNAs are known to control messenger RNA (mRNA) translation through recognition of specific binding sites usually located in their 3' untranslated region. Recent evidences indicate that the host miRNA pathway may represent an adapted antiviral defense mechanism that can act either by direct miRNA-mediated modulation of viral gene expression or through recognition and inactivation of structured viral RNA species by the protein components of the RNA silencing machinery such as Dicer. This latter process, however, is a double-edge sword, as it may yield viral miRNAs exerting gene regulatory properties on both host and viral mRNAs. Our knowledge of the interaction between viruses and host RNA silencing machineries, and how this influences the course of infection, is becoming increasingly complex. This chapter aims to summarize our current knowledge about viral miRNAs/ncRNAs and their targets, as well as cellular miRNAs that are modulated by viruses upon infection.

miR-221 overexpression contributes to liver tumorigenesis

MicroRNA (miRNAs) are negative regulators of gene expression and can function as tumor suppressors or oncogenes. Expression patterns of miRNAs and their role in the pathogenesis of hepatocellular carcinoma (HCC) are still poorly understood. We profiled miRNA expression in tissue samples (104 HCC, 90 adjacent cirrhotic livers, 21 normal livers) as well as in 35 HCC cell lines. A set of 12 miRNAs (including miR-21, miR-221/222, miR-34a, miR-519a, miR-93, miR-96, and let-7c) was linked to disease progression from normal liver through cirrhosis to full-blown HCC. miR-221/222, the most up-regulated miRNAs in tumor samples, are shown to target the CDK inhibitor p27 and to enhance cell growth in vitro. Conversely, these activities can be efficiently inhibited by an antagomiR specific for miR-221. In addition, we show, using a mouse model of liver cancer, that miR-221 overexpression stimulates growth of tumorigenic murine hepatic progenitor cells. Finally, we identified DNA damage-inducible transcript 4 (DDIT4), a modulator of mTOR pathway, as a bona fide target of miR-221. Taken together, these data reveal an important contribution for miR-221 in hepatocarcinogenesis and suggest a role for DDIT4 dysregulation in this process. Thus, the use of synthetic inhibitors of miR-221 may prove to be a promising approach to liver cancer treatment.

Systematic identification of microRNA and messenger RNA profiles in hepatitis C virus-infected human hepatoma cells

In order to investigate the global and dynamic host microRNAs (miRNAs)/messenger RNAs (mRNAs) expression alteration during in vitro acute HCV infection, a comprehensive microarray analysis was performed using human hepatoma cells. Totally, 108 human miRNAs and 1247 mRNAs were identified whose expression levels changed for more than 2.0-fold in response to HCV infection. Upon HCV infection, signature from the unique miRNA expression pattern reflected the involvement of miRNA-regulated host cellular physiology and antiviral mechanism, whereas a preponderance of differentially regulated genes associated with metabolism, cell growth, apoptosis and cytokine/chemokine pathways. Furthermore, a reverse regulatory association of differentially expressed miRNAs and their predicted targets was constructed. Finally, the differentially expressed miRNAs such as miR-24, miR-149, miR-638 and miR-1181 were identified to be involved in HCV entry, replication and propagation. These results suggest that combined miRNA and mRNA profiling may have superior potential as a diagnostic and mechanistic feature in HCV infection.

Emerging role of microRNAs in liver diseases

MicroRNAs are a class of small non-coding RNAs that are found in plants, animals, and some viruses. They modulate the gene function at the post-transcriptional level and act as a fine tuner of various processes, such as development, proliferation, cell signaling, and apoptosis. They are associated with different types and stages of cancer. Recent studies have shown the involvement of microRNAs in liver diseases caused by various factors, such as Hepatitis C, Hepatitis B, metabolic disorders, and by drug abuse. This review highlights the role of microRNAs in liver diseases and their potential use as therapeutic molecules.

MicroRNA-145 in vascular smooth muscle cell biology: a new therapeutic target for vascular disease

Vascular smooth muscle cell (VSMC) phenotypic modulation and proliferation are critical cellular events in the development of a variety of proliferative vascular diseases. However, the molecular mechanisms involved in these cellular events are still unclear. MicroRNAs (miRNAs) represent a novel class of small, non-coding RNAs that negatively regulate gene expression via degradation or translational inhibition of their target mRNAs. In a previous study, we identified that miR-145 is the most abundant miRNA in normal arteries and VSMCs. However, the roles of miR-145 in VSMC biology and vascular disease are unknown. In our recent Circulation Research article, we found that the expression of miR-145 is significantly downregulated in dedifferentiated VSMCs and in balloon-injured arteries. Moreover, both in vitro and in vivo studies demonstrated that miR-145 is a critical modulator of VSMC phenotype and proliferation. This review article summarizes the current research progress regarding the roles of miR-145 in VSMC biology and discusses the potential therapeutic opportunities surrounding this miRNA in vascular disease.

Decreased expression of miR-125b and miR-100 in oral cancer cells contributes to malignancy

Altered microRNA (miRNA) expression profiles have been observed in numerous malignancies, including oral squamous cell carcinoma (OSCC). However, their role in disease is not entirely clear. Several genetic aberrations are characteristic of OSCC, with amplification of chromosomal band 11q13 and loss of distal 11q being among the most prevalent. It is not known if the expression levels of miRNAs in these regions are altered or whether they play a role in disease. We hypothesize that the expression of miRNAs mapping to 11q are altered in OSCC because of loss or amplification of chromosomal material, and that this contributes to the development and progression of OSCC. We found that miR-125b and miR-100 are down-regulated in OSCC tumor and cell lines, and that transfecting cells with exogenous miR-125b and miR-100 significantly reduced cell proliferation and modified the expression of target and nontarget genes, including some that are overexpressed in radioresistant OSCC cells. In conclusion, the down-regulation of miR-125b and miR-100 in OSCC appears to play an important role in the development and/or progression of disease and may contribute to the loss of sensitivity to ionizing radiation.

Loss of miR-122 expression in liver cancer correlates with suppression of the hepatic phenotype and gain of metastatic properties

Growing evidence indicates that microRNAs have a significant role in tumor development and may constitute robust biomarkers for cancer diagnosis and prognosis. In this study, we evaluated the clinical and functional relevance of microRNA-122 (miR-122) expression in human hepatocellular carcinoma (HCC). We report that miR-122 is specifically repressed in a subset of primary tumors that are characterized by poor prognosis. We further show that the loss of miR-122 expression in tumor cells segregates with specific gene expression profiles linked to cancer progression, namely the suppression of hepatic phenotype and the acquisition of invasive properties. We identify liver-enriched transcription factors as central regulatory molecules in the gene networks associated with loss of miR-122, and provide evidence suggesting that miR-122 is under the transcriptional control of HNF1A, HNF3A and HNF3B. We further show that loss of miR-122 results in an increase of cell migration and invasion and that restoration of miR-122 reverses this phenotype. In conclusion, miR-122 is a marker of hepatocyte-specific differentiation and an important determinant in the control of cell migration and invasion. From a clinical point of view, our study emphasizes miR-122 as a diagnostic and prognostic marker for HCC progression.

MiR-122/cyclin G1 interaction modulates p53 activity and affects doxorubicin sensitivity of human hepatocarcinoma cells

The identification of target genes is a key step for assessing the role of aberrantly expressed microRNAs (miRNA) in human cancer and for the further development of miRNA-based gene therapy. MiR-122 is a liver-specific miRNA accounting for 70% of the total miRNA population. Its down-regulation is a common feature of both human and mouse hepatocellular carcinoma (HCC). We have previously shown that miR-122 can regulate the expression of cyclin G1, whose high levels have been reported in several human cancers. We evaluated the role of miR-122 and cyclin G1 expression in hepatocarcinogenesis and in response to treatment with doxorubicin and their relevance on survival and time to recurrence (TTR) of HCC patients. We proved that, by modulating cyclin G1, miR-122 influences p53 protein stability and transcriptional activity and reduces invasion capability of HCC-derived cell lines. In addition, in a therapeutic perspective, we assayed the effects of a restored miR-122 expression in triggering doxorubicin-induced apoptosis and we proved that miR-122, as well as cyclin G1 silencing, increases sensitivity to doxorubicin challenge. In patients resected for HCC, lower miR-122 levels were associated with a shorter TTR, whereas higher cyclin G1 expression was related to a lower survival, suggesting that miR-122 might represent an effective molecular target for HCC. Our findings establish a basis toward the development of combined chemo- and miRNA-based therapy for HCC treatment.

MicroRNA expression profile in Lieber-DeCarli diet-induced alcoholic and methionine choline deficient diet-induced nonalcoholic steatohepatitis models in mice

BACKGROUND

Alcoholic and nonalcoholic steatohepatitis are leading causes of liver diseases worldwide. While of different etiology, these share common pathophysiological mechanisms and feature abnormal fat metabolism, inflammation and fibrosis. MicroRNAs (miRNA) are highly conserved noncoding RNAs that control gene expression at the post-transcriptional level either via the degradation of target mRNAs or the inhibition of translation. Each miRNA controls the expression of multiple targets; miRNAs have been linked to regulation of lipid metabolism and inflammation.

METHODS

We fed Lieber-DeCarli alcohol or methionine-choline-deficient (MCD) diets to C57Bl6 and analyzed livers for histopathology, cytokines by ELISA, alanine aminotransferase (ALT) by biochemical assay, and microRNA profile by microarray.

RESULTS

Both Lieber-DeCarli and MCD diets lead to development of liver steatosis, liver injury, indicated by increased ALT, and elevated levels of serum TNFalpha, suggesting that animal models portray the pathophysiological features of alcoholic and nonalcoholic fatty liver, respectively. We identified that Lieber-deCarli diet up-regulated 1% and down-regulated 1% of known miRNA; MCD diet up-regulated 3% and down-regulated 1% of known miRNA, compared to controls. Of miRNAs that changed expression levels, 5 miRNAs were common in alcoholic and nonalcoholic fatty livers: the expression of both miR-705 and miR-1224 was increased after Lieber-DeCarli or MCD diet feeding. In contrast, miR-182, miR-183, and miR-199a-3p were down-regulated in Lieber-deCarli feeding, while MCD diet lead to their up-regulation, compared to corresponding controls.

CONCLUSIONS

Our findings indicate etiology-specific changes in miRNA expression profile during steatohepatitis models, which opens new avenues for research in the pathophysiology of alcoholic and nonalcoholic fatty liver disease.

MicroRNA expression profile in Lieber-DeCarli diet-induced alcoholic and methionine choline deficient diet-induced nonalcoholic steatohepatitis models in mice

BACKGROUND

Alcoholic and nonalcoholic steatohepatitis are leading causes of liver diseases worldwide. While of different etiology, these share common pathophysiological mechanisms and feature abnormal fat metabolism, inflammation and fibrosis. MicroRNAs (miRNA) are highly conserved noncoding RNAs that control gene expression at the post-transcriptional level either via the degradation of target mRNAs or the inhibition of translation. Each miRNA controls the expression of multiple targets; miRNAs have been linked to regulation of lipid metabolism and inflammation.

METHODS

We fed Lieber-DeCarli alcohol or methionine-choline-deficient (MCD) diets to C57Bl6 and analyzed livers for histopathology, cytokines by ELISA, alanine aminotransferase (ALT) by biochemical assay, and microRNA profile by microarray.

RESULTS

Both Lieber-DeCarli and MCD diets lead to development of liver steatosis, liver injury, indicated by increased ALT, and elevated levels of serum TNFalpha, suggesting that animal models portray the pathophysiological features of alcoholic and nonalcoholic fatty liver, respectively. We identified that Lieber-deCarli diet up-regulated 1% and down-regulated 1% of known miRNA; MCD diet up-regulated 3% and down-regulated 1% of known miRNA, compared to controls. Of miRNAs that changed expression levels, 5 miRNAs were common in alcoholic and nonalcoholic fatty livers: the expression of both miR-705 and miR-1224 was increased after Lieber-DeCarli or MCD diet feeding. In contrast, miR-182, miR-183, and miR-199a-3p were down-regulated in Lieber-deCarli feeding, while MCD diet lead to their up-regulation, compared to corresponding controls.

CONCLUSIONS

Our findings indicate etiology-specific changes in miRNA expression profile during steatohepatitis models, which opens new avenues for research in the pathophysiology of alcoholic and nonalcoholic fatty liver disease.

miR-10 in development and cancer

The microRNA (miRNA) miR-10 family has attracted attention because of its conservation and the position of the miR-10 genes within the Hox clusters of developmental regulators. In several species, miR-10 is coexpressed with a set of Hox genes and has been found to regulate the translation of Hox transcripts. In addition, members of the miR-10 family are de-regulated in several cancer forms. Aside from acting in translational repression, miR-10 was recently found to bind a group of transcripts containing a terminal oligo-pyrimidine (TOP) motif and to induce their translation, thereby adding a new function to the miRNA repertoire.

MicroRNA signatures in liver diseases

MicroRNAs (miRNAs) are an emerging class of highly conserved non-coding small RNAs that regulate gene expression at the post-transcriptional level. It is now clear that miRNAs can potentially regulate every aspect of cellular activity, including differentiation and development, metabolism, proliferation, apoptotic cell death, viral infection and tumorigenesis. Recent studies provide clear evidence that miRNAs are abundant in the liver and modulate a diverse spectrum of liver functions. Deregulation of miRNA expression may be a key pathogenetic factor in many liver diseases including viral hepatitis, hepatocellular cancer and polycystic liver diseases. A clearer understanding of the mechanisms involved in miRNA deregulation will offer new diagnostic and therapeutic strategies to treat liver diseases. Moreover, better understanding of miRNA regulation and identification of tissue-specific miRNA targets employing transgenic/knockout models and/or modulating oligonucleotides will improve our knowledge of liver physiology and diseases.

MicroRNA-21 is overexpressed in human cholangiocarcinoma and regulates programmed cell death 4 and tissue inhibitor of metalloproteinase 3

Cholangiocarcinomas (CCAs) are aggressive cancers, with high mortality and poor survival rates. Only radical surgery offers patients some hope of cure; however, most patients are not surgical candidates because of late diagnosis secondary to relatively poor accuracy of diagnostic means. MicroRNAs (miRs) are involved in every cancer examined, but they have not been evaluated in primary CCA. In this study, miR arrays were performed on five primary CCAs and five normal bile duct specimens (NBDs). Several miRs were dysregulated and miR-21 was overexpressed in CCAs. miR-21 differential expression in these 10 specimens was verified by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). To validate these findings, qRT-PCR for miR-21 was then performed on 18 additional primary CCAs and 12 normal liver specimens. MiR-21 was 95% sensitive and 100% specific in distinguishing between CCA and normal tissues, with an area under the receiver operating characteristic curve of 0.995. Inhibitors of miR-21 increased protein levels of programmed cell death 4 (PDCD4) and tissue inhibitor of metalloproteinases 3 (TIMP3). Notably, messenger RNA levels of TIMP3 were significantly lower in CCAs than in normals.

CONCLUSIONS

MiR-21 is overexpressed in human CCAs. Furthermore, miR-21 may be oncogenic, at least in part, by inhibiting PDCD4 and TIMP3. Finally, these data suggest that TIMP3 is a candidate tumor suppressor gene in the biliary tree.

Advances in the relationship between microRNA and mechanism of human primary hepatocellular carcinoma

In genetics, microRNAs (miRNAs) are single-stranded RNA molecules of 19-22 nucleotides (nts) in length, which are non-coding RNAs and negatively down-regulate expression of their target genes in post-transcriptional level. Recently, many studies have shown that miRNAs are involved in the regulation of cell proliferation, differentiation, apoptosis and so on. The mutation, depletion or dysfunction of miRNAs was closely associated with occurrence and progression of human cancers. This review mainly discusses the advances in the relationship between miRNAs and hepatocellular carcinoma (HCC) in recent years.

Role of the miR-106b-25 microRNA cluster in hepatocellular carcinoma

MicroRNAs are tiny RNA molecules which serve as important post-transcriptional regulators of gene expression. Dysregulated expression of microRNAs has been observed in human cancers, indicating that microRNAs may function as oncogenes or as tumor suppressors. To date, the microRNAs encoded by the oncogenic miR-17-92 cluster, and its paralog the miR-106b-25 cluster, are among those which are differentially expressed in human cancers. In this study, we examined and confirmed the over-expression of these clusters in hepatocellular carcinoma and in hepatoma-derived cells. At least 50% of the tumor samples showed a greater than two-fold increase in the expression for miR-18 and for the miR-106b-25 cluster when compared with the corresponding paired non-tumor samples. Knock-down studies for the miR-106b-25 cluster, which includes miR-106b, miR-93 and miR-25, showed that the expression of the cluster is necessary for cell proliferation and for anchorage-independent growth. In tumors with high expression of this cluster, reduced expression of the BH3-only protein Bim, a miR-25 target, was observed. We further identified the transcription factor E2F1 as a target gene for miR-106b and miR-93 and it is likely that one of the roles of the miR-106b-25 cluster is to prevent excessively high E2F1 expression, which may then cause apoptosis. We conclude that there is aberrant expression of microRNAs encoded by the oncogenic miR-17-92 cluster and the miR-106b-25 cluster in hepatocellular carcinoma. The consistent overexpression of the miR-106b-25 cluster and its role in cell proliferation and anchorage-independent growth points to the oncogenic potential of this cluster.

MicroRNA signatures in liver diseases

MicroRNAs (miRNAs) are an emerging class of highly conserved non-coding small RNAs that regulate gene expression at the post-transcriptional level. It is now clear that miRNAs can potentially regulate every aspect of cellular activity, including differentiation and development, metabolism, proliferation, apoptotic cell death, viral infection and tumorigenesis. Recent studies provide clear evidence that miRNAs are abundant in the liver and modulate a diverse spectrum of liver functions. Deregulation of miRNA expression may be a key pathogenetic factor in many liver diseases including viral hepatitis, hepatocellular cancer and polycystic liver diseases. A clearer understanding of the mechanisms involved in miRNA deregulation will offer new diagnostic and therapeutic strategies to treat liver diseases. Moreover, better understanding of miRNA regulation and identification of tissue-specific miRNA targets employing transgenic/knockout models and/or modulating oligonucleotides will improve our knowledge of liver physiology and diseases.

MicroRNA involvement in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third cause of cancer-related death worldwide. Curative options for HCC are limited and exclusively available for patients carrying an early stage HCC. In advanced stages, traditional chemotherapy proved to be only marginally effective or even toxic. Thus, the identification of new treatment options is needed. New targets for non-conventional treatment will necessarily take advantage of progresses on the molecular pathogenesis of HCC. MicroRNAs (miRNAs) are a group of tiny RNAs with a fundamental role in the regulation of gene expression. Aberrant expression of several miRNAs was found to be involved in human hepatocarcinogenesis. miRNA expression signatures were correlated with bio-pathological and clinical features of HCC. In some cases, aberrantly expressed miRNAs could be linked to cancer-associated pathways, indicating a direct role in liver tumourigenesis. For example, up-regulation of mir-221 and mir-21 could promote cell cycle progression, reduce cell death and favour angiogenesis and invasion. These findings suggest that miRNAs could become novel molecular targets for HCC treatment. The demonstration of in vivo efficacy and safety of anti-miRNA compounds has opened the way to their use in clinical trials.

MicroRNA-101 regulates expression of the v-fos FBJ murine osteosarcoma viral oncogene homolog (FOS) oncogene in human hepatocellular carcinoma

MicroRNAs (miRNAs) have recently been proposed as a versatile class of molecules involved in regulation of various biological processes. Although there is emerging evidence that some microRNAs can function as oncogenes or tumor suppressors, the specific role of miRNA in human hepatocellular carcinoma (HCC) is unclear at this point. In this study, we examined the microRNA expression profiles in a set of 20 human HCC specimens by miRNA microarray and quantitative real-time polymerase chain reaction. The results showed that among the 20 HCC samples analyzed, microRNA-101 was significantly down-regulated twofold or more (twofold to 20-fold) in 16 samples compared with the matching nontumoral liver tissues. Using both a luciferase reporter assay and Western blot analysis, we showed that microRNA-101 repressed the expression of v-fos FBJ murine osteosarcoma viral oncogene homolog (FOS) oncogene, a key component of the activator protein-1 (AP-1) transcription factor. Moreover, using a luciferase expression vector (pAP-1-Luc) driven by seven copies of an AP-1 cis-element, we observed that microRNA-101 expression inhibited phorbol 12-myristate 13-acetate (PMA)-induced AP-1 activity. In in vitro Matrigel invasion and Transwell migration assays, enhanced microRNA-101 expression inhibited the invasion and migration of cultured HCC cells, respectively. These findings suggest that microRNA-101 may play an important role in HCC.

CONCLUSION

MicroRNA-101, which is aberrantly expressed in HCC, could repress the expression of the FOS oncogene.

Differential microRNA expression between hepatitis B and hepatitis C leading disease progression to hepatocellular carcinoma

MicroRNA (miRNA) plays an important role in the pathology of various diseases, including infection and cancer. Using real-time polymerase chain reaction, we measured the expression of 188 miRNAs in liver tissues obtained from 12 patients with hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) and 14 patients with hepatitis C virus (HCV)-related HCC, including background liver tissues and normal liver tissues obtained from nine patients. Global gene expression in the same tissues was analyzed via complementary DNA microarray to examine whether the differentially expressed miRNAs could regulate their target genes. Detailed analysis of the differentially expressed miRNA revealed two types of miRNA, one associated with HBV and HCV infections (n = 19), the other with the stage of liver disease (n = 31). Pathway analysis of targeted genes using infection-associated miRNAs revealed that the pathways related to cell death, DNA damage, recombination, and signal transduction were activated in HBV-infected liver, and those related to immune response, antigen presentation, cell cycle, proteasome, and lipid metabolism were activated in HCV-infected liver. The differences in the expression of infection-associated miRNAs in the liver correlated significantly with those observed in Huh7.5 cells in which infectious HBV or HCV clones replicated. Out of the 31 miRNAs associated with disease state, 17 were down-regulated in HCC, which up-regulated cancer-associated pathways such as cell cycle, adhesion, proteolysis, transcription, and translation; 6 miRNAs were up-regulated in HCC, which down-regulated anti-tumor immune response.

CONCLUSION

miRNAs are important mediators of HBV and HCV infection as well as liver disease progression, and therefore could be potential therapeutic target molecules.

MicroRNA-101, down-regulated in hepatocellular carcinoma, promotes apoptosis and suppresses tumorigenicity

Although aberrant microRNA (miRNA) expressions have been observed in different types of cancer, their pathophysiologic role and their relevance to tumorigenesis are still largely unknown. In this study, we first evaluated the expression of 308 miRNAs in human hepatocellular carcinoma (HCC) and normal hepatic tissues and identified 29 differentially expressed miRNAs in HCC tissues. miR-101, a significantly down-regulated miRNA, was further studied in greater detail because the signal pathway(s) regulated by miR-101 and the role of miR-101 in tumorigenesis have not yet been elucidated. Interestingly, decreased expression of miR-101 was found in all six hepatoma cell lines examined and in as high as 94.1% of HCC tissues, compared with their nontumor counterparts. Furthermore, ectopic expression of miR-101 dramatically suppressed the ability of hepatoma cells to form colonies in vitro and to develop tumors in nude mice. We also found that miR-101 could sensitize hepatoma cell lines to both serum starvation- and chemotherapeutic drug-induced apoptosis. Further investigation revealed that miR-101 significantly repressed the expression of luciferase carrying the 3'-untranslated region of Mcl-1 and reduced the endogenous protein level of Mcl-1, whereas the miR-101 inhibitor obviously up-regulated Mcl-1 expression and inhibited cell apoptosis. Moreover, silencing of Mcl-1 phenocopied the effect of miR-101 and forced expression of Mcl-1 could reverse the proapoptotic effect of miR-101. These results indicate that miR-101 may exert its proapoptotic function via targeting Mcl-1. Taken together, our data suggest an important role of miR-101 in the molecular etiology of cancer and implicate the potential application of miR-101 in cancer therapy.

Current progress in epigenetic research for hepatocarcinomagenesis

Hepatocellular carcinoma is the main type of primary liver cancer, and also one of the most malignant tumors. At present, the pathogenesis mechanisms of liver cancer are not entirely clear. It has been shown that inactivation of tumor suppressor genes and activation of oncogenes play a significant role in carcinogenesis, caused by the genetic and epigenetic aberrance. In the past, people generally thought that genetic mutation is a key event of tumor pathogenesis, and somatic mutation of tumor suppressor genes is in particular closely associated with oncogenesis. With deeper understanding of tumors in recent years, increasing evidence has shown that epigenetic silencing of those genes, as a result of aberrant hypermethylation of CpG islands in promoters and histone modification, is essential to carcinogenesis and metastasis. The term epigenetics refers to heritable changes in gene expression caused by regulation mechanisms, other than changes in the underlying DNA sequence. Specific epigenetic processes include DNA methylation, genome imprinting, chromotin remodeling, histone modification and microRNA regulations. This paper reviews recent epigenetics research progress in the hepatocellular carcinoma study, and tries to depict the relationships between hepatocellular carcinomagenesis and DNA methylation as well as microRNA regulation.

miR-198 inhibits HIV-1 gene expression and replication in monocytes and its mechanism of action appears to involve repression of cyclin T1

Cyclin T1 is a regulatory subunit of a general RNA polymerase II elongation factor known as P-TEFb. Cyclin T1 is also required for Tat transactivation of HIV-1 LTR-directed gene expression. Translation of Cyclin T1 mRNA has been shown to be repressed in human monocytes, and this repression is relieved when cells differentiate to macrophages. We identified miR-198 as a microRNA (miRNA) that is strongly down-regulated when monocytes are induced to differentiate. Ectopic expression of miR-198 in tissue culture cells reduced Cyclin T1 protein expression, and plasmid reporter assays verified miR-198 target sequences in the 3′ untranslated region (3′UTR) of Cyclin T1 mRNA. Cyclin T1 protein levels increased when an inhibitor of miR-198 was transfected into primary monocytes, and overexpression of miR-198 in primary monocytes repressed the normal up-regulation of Cyclin T1 during differentiation. Expression of an HIV-1 proviral plasmid and HIV-1 replication were repressed in a monocytic cell line upon overexpression of miR-198. Our data indicate that miR-198 functions to restrict HIV-1 replication in monocytes, and its mechanism of action appears to involve repression of Cyclin T1 expression.

Monocytes do not support HIV-1 replication, in part because they do not express adequate levels of essential cellular cofactors that mediate steps in the viral replication cycle. Monocytes become permissive for viral replication upon differentiation to macrophages, indicating that cellular cofactors are induced during the differentiation process. One such cofactor is Cyclin T1, which is not expressed in monocytes and is expressed at high levels following macrophage differentiation. Cyclin T1 functions to greatly stimulate the amount of HIV-1 produced in the infected cell. We identified a microRNA (miRNA) named miR-198 that represses the expression of Cyclin T1 in monocytes. miRNAs block expression of proteins by binding to messenger RNAs and preventing their translation by ribosomes. The expression levels of miR-198 are greatly reduced in macrophages, and this appears to allow translation of Cyclin T1 mRNA and expression of Cyclin T1 protein. Our study indicates that this miRNA restricts HIV-1 replication in monocytes. We think that it is possible, if not likely, that additional miRNAs in monocytes also restrict HIV-1 replication by repressing other essential cellular cofactors.

Expression profile of microRNA in epithelial cancer: diagnosis, classification and prediction

BACKGROUND

MicroRNAs (miRNAs), the small non-coding RNAs, regulate gene expression in a sequence-specific manner. Up to one-third of human messenger RNAs (mRNAs) appear to be miRNA targets. Each miRNA can target hundreds of mRNA transcripts and production of proteins directly or indirectly, while more than one miRNA can converge on a single transcript target. Therefore, potential regulatory circuitries afforded by miRNAs are enormous. Recent studies indicate that miRNAs act as key regulators of various fundamental biological processes, in which common pathways are shared with cancer.

OBJECTIVE/METHODS

To provide an overview of the potential application of miRNA profile in human epithelial cancer diagnosis, more than 180 miRNA-related publications have been reviewed.

CONCLUSION

Increasing evidence shows that the expression of miRNAs is remarkably deregulated in human cancer owing to multiple epigenetic and genomic alterations, and several miRNAs have been demonstrated to serve as tumor suppressor genes or oncogenes in cancer. The deregulated miRNA expression profile in human cancer may prove a powerful tool for cancer detection, diagnosis, classification and prognosis.

miR-122 targets an anti-apoptotic gene, Bcl-w, in human hepatocellular carcinoma cell lines

miR-122, a hepato-specific microRNA (miRNA), is frequently down-regulated in human hepatocellular carcinoma (HCC). In an effort to identify novel miR-122 targets, we performed an in silico analysis and detected a putative binding site in the 3'-untranslated region (3'-UTR) of Bcl-w, an anti-apoptotic Bcl-2 family member. In the HCC-derived cell lines, Hep3B and HepG2, we confirmed that miR-122 modulates Bcl-w expression by directly targeting binding site within the 3'-UTR. The cellular mRNA and protein levels of Bcl-w were repressed by elevated levels of miR-122, which subsequently led to reduction of cell viability and activation of caspase-3. Thus, Bcl-w is a direct target of miR-122 that functions as an endogenous apoptosis regulator in these HCC-derived cell lines.

Right hepatic lobectomy in elderly patients with hepatocellular carcinoma

BACKGROUND/AIMS

The outcome of hepatectomy in elderly patients with hepatocellular carcinoma have been reported, however neither the morphological nor functional hepatic regeneration in elderly patients have been fully investigated.

MATERIALS AND METHODS

Fifty-six patients with hepatocellular carcinoma, who underwent a right hepatic lobectomy over an 8-year period, were classified into three groups according to their age; group 1 (n = 7), more than 70 years of age; group 2 (n = 40), patients from 50 to 69 years of age and group 3 (n = 9), under 50 years of age. There were no significant differences regarding backgrounds or intra-operative parameters among the three groups. The perioperative hepatic function, postoperative complications and the regeneration rate of the remnant left lobe at 1 month after operation were compared.

RESULTS

No differences were found in the regeneration rate, however, the levels of the hepaplastin test and lecithin:cholesterol acyltransferase at 7 days after hepatectomy in group 1 (31.3%, 8.8 U) were significantly lower than those in groups 2 and 3 (37.4%, 18.4 U; 47.9%, 29.4 U, respectively). The incidence of hospital death due to hepatic failure in group 1 (42.9%) was also significantly higher than that of group 2 (5.0%) or group 3 (0%).

CONCLUSION

The decline of postoperative protein synthesis regardless of the voluminal regeneration is a characteristic of the elderly. This phenomenon might thus be an important promoter of postoperative hepatic failure which remains unpredictable using any type of examination. Therefore, at this time, a major hepatectomy is not recommended as a viable treatment alternative in the elderly.