title: Epigenetic silencing of miR-335 and its host gene MEST in hepatocellular             carcinoma.
abstract: MicroRNAs (miRNAs) are small non-coding RNAs that function as endogenous             silencers of target genes. Some tumor-suppressive miRNAs are known to be epigenetically             silenced by promoter DNA methylation in cancer. In the present study, we aimed             to identify miRNA genes that are silenced by DNA hypermethylation in hepatocellular             carcinoma (HCC). We screened for miRNA genes with promoter DNA hypermethylation             using a genome-wide methylation microarray analysis in HCC cells. It was found             that miR-335, which is harbored within an intron of its protein-coding host gene,             MEST, was downregulated by aberrant promoter hypermethylation via further methylation             assays, including methylation-specific PCR, combined bisulfite and restriction             analysis, bisulfite sequencing analysis and 5-aza-2'-deoxycytidine treatment.             The expression levels of miR-335 significantly correlated with those of MEST,             supporting the notion that the intronic miR-335 is co-expressed with its host             gene. The levels of miR-335/MEST methylation were significantly higher in 18 (90%)             out of 20 primary HCC tumors, compared to their non-tumor tissue counterparts             (P<0.001). The expression levels of miR-335 were significantly lower in 25             (78%) out of 32 primary HCC tumors, compared to their non-tumor tissue counterparts             (P=0.001). Furthermore, the expression levels of miR-335 were significantly lower             in HCC tumors with distant metastasis compared to those without distant metastasis             (P=0.02). In conclusion, our results indicate that expression of miR-335 is reduced             by aberrant DNA methylation in HCC.
authors.affiliation: Department of Molecular Gastroenterology and Hepatology, Kyoto                     Prefectural University of Medicine, Kyoto, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Dohi
authors.forename: Kohichiroh
authors.initials: K
authors.lastname: Yasui
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Gen
authors.forename: Hisashi
authors.initials: H
authors.lastname: Takada
authors.forename: Mio
authors.initials: M
authors.lastname: Endo
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Tsuji
authors.forename: Chika
authors.initials: C
authors.lastname: Konishi
authors.forename: Nobuhisa
authors.initials: N
authors.lastname: Yamada
authors.forename: Hironori
authors.initials: H
authors.lastname: Mitsuyoshi
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Yagi
authors.forename: Yuji
authors.initials: Y
authors.lastname: Naito
authors.forename: Shinji
authors.initials: S
authors.lastname: Tanaka
authors.forename: Shigeki
authors.initials: S
authors.lastname: Arii
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Yoshikawa
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000473:pathology; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D015894:Genome, Human; D056945:Hep G2 Cells; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D011506:Proteins / Q000235:genetics*
chemical_list: C556347:MIRN335 microRNA, human; D035683:MicroRNAs; D011506:Proteins; C103637:mesoderm specific transcript protein