Study On Expression Profile Of MicroRNA And Significance Of MiR-148a In Gastric Cancer

Aim: Screen for miRNAs which are abnormally expressed in gastric cancer tissues. Then investigate the biological role of specific miRNA in gastric cancer.Methods: miRNA microarrays were employed to detect the miRNA expression profiles of 6 gastric cancer tissues and their corresponding normal gastric epithelium. According to the profiles, chose miR-148a for further study. Firstly, Quantitative real-time PCR(qPCR) analysis was used to validate the microarray result. Secondly, SPSS software was used to analyze the relationship of miR-148a and clinico- pathological parameters in gastric cancer tissues. According to the software analysis, miR-148a may be related to a specific biological behavior. And then, target prediction software was used to look for miR-148a targets which were related to the biological behavior. Finally, qPCR was used to detect the expression of specific target. Meanwhile, 5-Aza-2'-deoxycitidine (5-aza-CdR, DAC) treatment was performed with BGC823. DAC with different concentrations (0, 2.5, 5μmol/L) were kept with the cells for two weeks, respectively. Cells were harvested on seventh day and forteenth day, then qPCR was performed to detect the expression changes of miR-148a and its potential target.Results: According to miRNA microarray, seven miRNAs .(miR-18a, miR-135b, miR-21, miR-297, miR-338-5p, miR-Plus-E1212 and miR-374b* ) were significantly increased in gastric cancer tissues, and nine miRNAs (miR-29b-2*, miR-1260, miR-Plus-E1241, sv40-miR-S1-5p, miR-148a, miR-29c, miR-647, miR-196b* and ebv-miR-BART5) were significantly downreguated in gastric cancer tissues. Then, the expressions of miR-148a in gastric cancer tissues were detected by qPCR, and the result was the same to miRNA microarray. According to SPSS software analysis, lower expression of miR-148a in gastric cancer was associated with pT(p=0.018), pN(p=0.04) and pTNM (p=0.029) staging. Meanwhile, qPCR analysis found that Robo 1, a potential targets of miR-148a, which was relation to invasion and metastasis of gastric cancer was differently upreguated in gastric cancer tissues(p=0.006). After treated with 5-aza-CdR, BGC823 cell tended to possess more miR-148a and less Robo 1 mRNA.Conclusion: Compared with normal gastric epithelium , many miRNAs were abnormally expressed in gastric cancer. miR-148a which was one of the significantly decreased miRNAs in gastric cancers was associated with pT, pN and pTNM staging of gastric cancer. Downregulation of miR-148a might promote gastric cancer invasion and metastasis due to its weakening regulation of Robo 1 mRNA. And the promoter hypermethylation of miR-148a gene may be an important reason for the downregulation of miR-148a in gastric cancer.