MiR-148a Regulates The Expression Of E-cadherin By DNMT1 In Gastric Cancer

Background:miRNAs is a type of endogenous,single-stranded,non-coding small RNAs,18-22 nucleotides(nts)in length,which regulate gene expression by completely or partial complementary with the 3’-untranslated region(3’-UTR)of target m RNAs.In recent years,more and more studies have shown that they areinvolved in development and progression of various cancers,and affect a wide variety of physiological processes of cancer,includingcell proliferation,apoptosis,metastasis and invasion,by rgulating the expression of some oncogenes or tumor suppressors.Some miRNAs have been verified to be deregulated in gastric cancer and are closely associated with its development and progression.Among them,micro RNA-148a(miR-148a)is significantly downregulated in gastric cancer tissues,and can suppress cell proliferaration,apoptosis,metastasis and invasion.Aberrant methylation in gene promoter region is a critical mechanism underlying gene silencing,and is involved in carcinogenesis.Tumor suppressive gene CDH1 encoded E-cadherin protein is a classical adhesion connection protein,and the loss expression of which leads to the enhancement of tumor cells metastasis and invasion capacities.E-cadherin is downregulated in gastric cancer,which is associated with aberrant hypermethylation in promoter region.Studies have shown that miR-148 a can inhibit metastasis of gastric cancer by upregulation of E-cadherin,while the underlying mechanism is still unclear.Objective:To investigate the correlation between E-cadherin and miR-148 a,and explore the underlying mechanism of miR-148 a regulating E-cadherin expression in gastric cancer.Methods:The m RNA levels of E-cadherin and miR-148 a were detected by q RT-PCR,and proteinexpression of E-cadherin was assayed by western blot;A correlation between E-cadherin m RNA levels and that of miR-148 a in gastric cancer was investigated by Pearson correlation analyses;The relationship between aberrant methylation and E-cadherin expression was evaluated by treatment of gastric cancer cells with demethylation drug;The regulatory mechanism of miR-148 a modulating E-cadherin was analyzed by transfected of gastric cancer cells with miR-148 a mimics or DNMT1 si RNA.Results:1.E-cadherin m RNA expressions were downregulated in 75%(15/20)of gastric cancer tissues relative to corresponding normal tissues.In addition,positive correlation between E-cadherin and miR-148 a m RNA levels was found.2.miR-148 a expression significantly increased after transfection of gastric cancer cell lines with miR-148 a mimics.The expression level of E-cadherin significantly increased aftertransfected with miR-148 a mimics relative to control.3.After treatment of MGC-803 and SGC-7901 cells with 5-aza-d C,the m RNA and protein levels of E-cadherin significantly increased.4.The DNMT1 expression significantly decreased after transfection of MGC-803 and SGC-7901 cells with DNMT1 si RNA.The m RNA and protein levels of E-cadherin were significantly up-regulated after transfected with DNMT1 si RNA.Conclusion: The enforced expression of miR-148 a may contribute to the reactivation of E-cadherin by suppression of DNMT1.