The final part explores the clinical value of miRNA as prognostic and diagnostic markers. Hepatocellular carcinoma is a highly aggressive tumor that currently ranks the fifth most prevalent cancer worldwide. Although few studies have reported on promising treatment strategies for HCC, the dismal outcome remains unchanged; the median survival of most patients is still 6–9 months from diagnosis.15 Epidemiological studies have firmly established a number of etiologic risk factors in the development of HCC. These can be broadly divided into host factors and environmental factors. Host factors include male gender and genetic metabolic defects contributing to obesity,

whereas environmental factors entail viral hepatitis (types B and C) infections, excessive U0126 research buy chronic alcohol intake,

dietary aflatoxin B1 exposure, and cigarette smoking.15 Complex interactions among these factors ultimately lead to chronic liver disease and/or liver cirrhosis, and the increased risk of HCC development. Several studies have begun to examine for specific miRNA deregulation in hepatitis B virus (HBV)-related and hepatitis C virus (HCV)-related HCCs. While a microarray profiling study in 25 HCC specimens showed no significant difference in miRNA expression between HBV and HCV-associated cases,16 another complementary study measuring the expression of 188 miRNAs in 12 HBV-related and 14 HCV-related HCCs identified 19 miRNAs that could differentiate the HBV and HCV groups.17 Thirteen miRNAs exhibited a decreased expression in the HCV group (including miR-190, miR-134, miR-151), and six showed specific reduced expression in the HBV group (including AP24534 supplier miR-23a, miR-142-5p, miR-34c).17 Concordantly, several studies have also identified miRNAs that were differentially regulated by HBV or HCV. Transfection of the HCV genome resulted in downregulation of 10 miRNAs and upregulation of 23 miRNAs, amongst which elevated miR-193b expression was apparent.18 On the other hand, miR-96 was reported to be

distinctively upregulated in HBV-associated HCC tumors.19 Interactions between host miRNAs and HCV have also been studied. MiR-122, a liver-specific miRNA, is abundantly expressed all in liver tissues and accounts for 70% of the total liver miRNA population.20 Host miR-122 was found to accelerate ribosome binding to HCV RNA, which in turn stimulated viral translation.21 Functional inactivation of miR-122 could lead to 80% reduction of HCV RNA replication in HCC cell lines.22 In this connection, repression of miR-122 in HCC might represent a compensatory mechanism that confers resistance to HCV replication in HCC cells.22 Hepatocellular carcinoma predominantly affects men, with an incidence typically two to four times higher than in women.23 In an attempt to elucidate the role of miRNAs in this gender disparity, the expression profile of a panel of 17 frequently deregulated miRNAs was compared between male and female HCC patients.