miR-148a suppresses cell invasion and migration in gastric cancer by targeting DNA methyltransferase 1

Gastric cancer (GC) is the fourth most common malignant tumor globally. The highest incidence of GC is found in Eastern Asia, particularly in China. It is therefore imperative to further elucidate the molecular pathogenesis of GC in order to identify new biomarkers and targets for effective therapy. In the present study, we determined whether miR-148a was aberrantly downregulated in gastric cancer tissues and significantly correlated with aggressive clinicopathological characteristics in the MGC-803, HGC-27 and GES-1 cell lines using reverse transcription-quantitative PCR and western blot analysis. The cell lines were obtained from 60 patients who presented at our hospital between September 2010 and July 2015. The results showed that, miR-148a was aberrantly downregulated in GC tissues and its expression was relatively lower in the MGC-803 and HGC-27 GC cell lines than in the normal gastric epithelial cell line, GES-1. The clinicopathological analysis revealed that a decrease of miR-148a was significantly correlated with lymph-node metastasis (P<0.01) and tumor node metastasis (TNM) stage (P< 0.05). The transwell assay showed that the re-expression of miR-148a significantly reduced cell migratory and invasive abilities in vitro (P< 0.01). The luciferase assay confirmed that, DNA methyl-transferase 1 (DNMT1) was a direct and functional target of miR-148a. The miR-148a inhibitor increased the expression of DNMT1 in HGC-27 cells and the re-expression of miR-148a reduced the expression of DNMT1 in MGC-803 cells as confirmed by western blot analysis. Furthermore, we found that the re-expression of DNMT1 reversed the inhibition of cell migration and invasion induced by miR-148a. Taken together, we demonstrated that miR-148a suppresses cell invasion and migration in gastric cancer by regulating DNMT1 expression. The miR-148a/DNMT1 axis may therefore be a new potential target for GC therapy.