title: MicroRNA-148a is silenced by hypermethylation and interacts with DNA methyltransferase 1 in gastric cancer.
abstract: Studies have shown that microRNA-148a (miR-148a) was proved to be silenced while DNA methyltransferase 1 (DNMT1) was over-expressed in gastric cancer. But the mechanism of aberrant expression of miR-148a and DNMT1 and their relationships in gastric cancer are still unknown. The aims of this study were to investigate the expression profile of miR-148a and DNMT1 and reveal whether they have any relationships. We used reverse-transcriptase quantitative real-time PCR, methylation-specific PCR and Western blot to measure the level of miR-148a expression, DNA methylation level and DNMT1 expression, respectively. Gastric cancer cells were transfected with plasmid or siRNA or treated with 5-aza-2'-deoxycytidine. Cell proliferation and apoptosis were detected by cell counting and flow cytometric analysis. In this study, we demonstrated that gastric cancer tissues and cell lines displayed a consistent down-regulation of miR-148a and hypermethylation of promoter region. DNMT1 was over-expressed in primary tumors and cell lines, while knockdown of DNMT1 using siRNA could decrease methylation level of miR-148a promoter and restore its expression. Furthermore, ectopic over-expression of miR-148a in cancer cell lines caused reduction in DNMT1 expression and inhibited cell proliferation, but no obvious change was found in apoptosis rate. These results suggest that miR-148a is inactivated by DNA hypermethylation of promoter region in gastric cancer, which is mediated through DNMT1 over-expression. Additionally, the silence of miR-148a reduces its suppression to DNMT1 in gastric cancer, and this may in turn result in over-expression of DNMT1 and promote DNA hypermethylation.
authors.affiliation: Department of General Surgery, Nanjing Medical University Affiliated Wuxi Second Hospital, No. 68, ZhongShan Road of Wuxi City, Wuxi, 214002, JiangSu Province, People's Republic of China.
authors.forename: Akao
authors.initials: A
authors.lastname: Zhu
authors.forename: Jiazeng
authors.initials: J
authors.lastname: Xia
authors.forename: Junbo
authors.initials: J
authors.lastname: Zuo
authors.forename: Shimao
authors.initials: S
authors.lastname: Jin
authors.forename: Hong
authors.initials: H
authors.lastname: Zhou
authors.forename: Lubin
authors.initials: L
authors.lastname: Yao
authors.forename: Hongyu
authors.initials: H
authors.lastname: Huang
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Han
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation; D018899:CpG Islands; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000502:physiology*; D019175:DNA Methylation; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D011401:Promoter Regions, Genetic; D013274:Stomach Neoplasms / Q000235:genetics* / Q000473:pathology
chemical_list: C550570:MIRN148 microRNA, human; D035683:MicroRNAs; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human