Epigenetically deregulated MIR-200c is involved in a negative feedback loop with DNMT3a in gastric cancer cells

Abstract

Aberrant methylation of miRNAs is commonly observed in cancers. In the present study, we investigated the regulation of the MIR-200 family and its role in regulating DNA methylation events in gastric cancer (GC). We demonstrated that MIR-200c was aberrantly expressed in GC and associated with histologic type and tumor progression. Hypermethylation of the promoter region was found to be responsible for the loss of MIR-200c in GC cells. Demethylation agents led to recovery of MIR-200c expression in GC cell lines. Moreover, DNMT3a knockdown abolished the hypermethylation of the MIR-200c gene and induced upregulation of MIR-200c expression, whereas ectopic DNMT3a expression increased MIR-200c promoter methylation and decreased MIR-200c expression. Conversely, transfection of MIR-200c led to downregulation of DNMT3a protein and induced endogenous pre-miR-200c and pri-miR-200c re-expression. Luciferase assays confirmed MIR-200c binding to the DNMT3a 3'UTR. Finally, ectopic expression of MIR-200c or knockdown of DNMT3a expression impeded GC cell growth, migration and invasion. Taken together, these observations demonstrates a novel epigenetic feedback loop between MIR-200c and DNMT3a in the carcinogenesis and progression of GC.