title: MicroRNA-375 is downregulated in gastric carcinomas and regulates cell survival by targeting PDK1 and 14-3-3zeta.
abstract: We investigated expression profiles of microRNA (miRNA) in gastric carcinomas by use of a miRNA microarray platform covering a total of 470 human miRNAs. We identified 39 differentially expressed miRNAs in gastric carcinoma, of which six were significantly downregulated and the other 33 were upregulated. We found that miRNA-375 (miR-375) was the most downregulated and that its ectopic expression in gastric carcinoma cells markedly reduced cell viability via the caspase-mediated apoptosis pathway. Interestingly, we found that expression of miR-375 inhibited expression of PDK1, which is a direct target of miR-375, followed by suppression of Akt phosphorylation. Further analysis by gene expression microarray revealed that 14-3-3zeta, a potent antiapoptotic gene, was significantly downregulated at both the mRNA and protein levels in cells transfected with miR-375. The activity of a luciferase reporter containing the miR-375 binding sequence at the 3' untranslated region (UTR) of 14-3-3zeta mRNA was repressed by the ectopic expression of miR-375, suggesting that miR-375 targets the 3' UTR of 14-3-3zeta. In addition, knockdown of either PDK1 or 14-3-3zeta in gastric carcinoma cells induced caspase activation, which was also observed in miR-375-transfected cells, suggesting that miR-375 may exert its proapoptotic function, at least in part, through the downregulation of PDK1 and 14-3-3zeta. Taken together, we propose that miR-375 is a candidate tumor suppressor miRNA in gastric carcinoma.
authors.affiliation: Department of Molecular Pathology, Faculty of Medicine and Institute of Scientific Research, Oita University, Oita, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Tsukamoto
authors.forename: Chisato
authors.initials: C
authors.lastname: Nakada
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Noguchi
authors.forename: Masato
authors.initials: M
authors.lastname: Tanigawa
authors.forename: Lam Tung
authors.initials: LT
authors.lastname: Nguyen
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Uchida
authors.forename: Naoki
authors.initials: N
authors.lastname: Hijiya
authors.forename: Keiko
authors.initials: K
authors.lastname: Matsuura
authors.forename: Toshio
authors.initials: T
authors.lastname: Fujioka
authors.forename: Masao
authors.initials: M
authors.lastname: Seto
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Moriyama
mesh_terms: D048948:14-3-3 Proteins / Q000235:genetics*; D020413:3' Untranslated Regions; D000107:Acetylation; D017209:Apoptosis / Q000235:genetics; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics; D019175:DNA Methylation; D015536:Down-Regulation; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D035683:MicroRNAs / Q000096:biosynthesis* / Q000235:genetics; D051058:Oncogene Protein v-akt / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D034741:RNA, Small Interfering / Q000235:genetics; D013274:Stomach Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D014162:Transfection
chemical_list: D048948:14-3-3 Proteins; D020413:3' Untranslated Regions; D006657:Histones; D035683:MicroRNAs; C000631429:PDK1 protein, human; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D034741:RNA, Small Interfering; D051058:Oncogene Protein v-akt; D017346:Protein Serine-Threonine Kinases