6D). We also measured the mRNA levels of GSTP1 and CDH1 by real-time PCR in HepG2 cells after transfection. The GSTP1 mRNA expression level was significantly decreased in the miR-152 inhibitor group compared with the control group (Fig. 6B). This indicated that the inhibition of miR-152 could decrease GSTP1 expression by promoter DNA hypermethylation. However, the CDH1 mRNA level was not significantly changed after transfection, probably because

the increase in the DNA methylation level was not sufficient to inhibit the mRNA expression. Epigenetic dysregulation of cellular genes is an integral R428 solubility dmso feature in the development of human cancers. Increasing evidence has revealed that viral genes are some of the key players in regulating DNA methylation.33 The epigenetic mechanisms

involved in virus-associated cancers are poorly understood, although aberrant promoter hypermethylation is a prevalent phenomenon in human cancers closely associated with viruses, such as HBV-related HCC. Hypermethylation is responsible for the silencing of TSGs involved in hepatocarcinogenesis. The involvement of the HBx protein in epigenetic regulation during hepatocarcinogenesis has been demonstrated previously, and it involves the activation of DNMTs7, 34 and the recruitment of DNMTs and methyl-CpG binding proteins to the target gene promoters. Interestingly, a strong correlation between HBV infection and epigenetic alterations of TSGs, including cyclin-dependent kinase inhibitor 2A (p16INK4a),35, 36 insulin-like DAPT cell line growth factor binding protein 3,7 GSTP1,37 E-cadherin (CDH1),36, 38 and Ras association domain family 1A (RASSF1A),36 has been shown. However, how HBV affects the DNA methylation states remains unknown. In this study, we characterized the role of miR-152 in the regulation of DNA methylation in HBV-related HCC for the first time. miR-152 induced aberrant DNA methylation by directly targeting DNMT1. Our data showed that miR-152 was frequently down-regulated 上海皓元 in HBV-positive HCCs in comparison with corresponding noncancerous liver tissues. This indicated

that miR-152 may have a tumor-suppressive role in HCC development. Our findings indicated that miR-152 expression was inversely correlated with DNMT1 expression in HCC; the down-regulation of miR-152, resulting in an up-regulation of DNMT1, was significant in HCC development. DNMT1 has been reported to be necessary and sufficient for maintaining global methylation and aberrant CpG island methylation in human cancer cells.39 Transcriptional silencing by CpG island methylation is a prevalent mechanism of TSG suppression in cancers. It is well known that decitabine, a potent and specific hypomethylating agent and an inhibitor of the DNMT activity that mediates DNA methylation, has been approved by the US Food and Drug Administration to treat myelodysplastic syndromes. Decitabine is also being studied in the treatment of cancer.