title: microRNA-29 can regulate expression of the long non-coding RNA gene MEG3 in hepatocellular cancer.
abstract: The human genome is replete with long non-coding RNAs (lncRNA), many of which are transcribed and likely to have a functional role. Microarray analysis of >23,000 lncRNAs revealed downregulation of 712 (~3%) lncRNA in malignant hepatocytes, among which maternally expressed gene 3 (MEG3) was downregulated by 210-fold relative to expression in non-malignant hepatocytes. MEG3 expression was markedly reduced in four human hepatocellular cancer (HCC) cell lines compared with normal hepatocytes by real-time PCR. RNA in situ hybridization showed intense cytoplasmic expression of MEG3 in non-neoplastic liver with absent or very weak expression in HCC tissues. Enforced expression of MEG3 in HCC cells significantly decreased both anchorage-dependent and -independent cell growth, and induced apoptosis. MEG3 promoter hypermethylation was identified by methylation-specific PCR and MEG3 expression was increased with inhibition of methylation with either 5-Aza-2-Deoxycytidine, or siRNA to DNA Methyltransferase (DNMT) 1 and 3b in HCC cells. MiRNA-dependent regulation of MEG3 expression was studied by evaluating the involvement of miR-29, which can modulate DNMT 1 and 3. Overexpression of mir-29a increased expression of MEG3. GTL2, the murine homolog of MEG3, was reduced in liver tissues from hepatocyte-specific miR-29a/b1 knock-out mice compared with wild-type controls. These data show that methylation-dependent tissue-specific regulation of the lncRNA MEG3 by miR-29a may contribute to HCC growth and highlight the inter-relationship between two classes of non-coding RNA, miRNAs and lncRNAs, and epigenetic regulation of gene expression.
authors.affiliation: College of Medicine, and the Ohio State University Comprehensive Cancer Center, Ohio State University, Columbus, OH, USA.
authors.forename: C
authors.initials: C
authors.lastname: Braconi
authors.forename: T
authors.initials: T
authors.lastname: Kogure
authors.forename: N
authors.initials: N
authors.lastname: Valeri
authors.forename: N
authors.initials: N
authors.lastname: Huang
authors.forename: G
authors.initials: G
authors.lastname: Nuovo
authors.forename: S
authors.initials: S
authors.lastname: Costinean
authors.forename: M
authors.initials: M
authors.lastname: Negrini
authors.forename: E
authors.initials: E
authors.lastname: Miotto
authors.forename: C M
authors.initials: CM
authors.lastname: Croce
authors.forename: T
authors.initials: T
authors.lastname: Patel
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000235:genetics*; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics*; D035683:MicroRNAs / Q000502:physiology*; D009928:Organ Specificity; D011506:Proteins / Q000235:genetics*; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics*
chemical_list: C498907:MEG3 non-coding RNA, human; C532045:MIRN29a microRNA, human; D035683:MicroRNAs; D011506:Proteins; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated