MiRNAs Mediate Demethylation Suppressing B7-H1 Expression Of Gastric Cancer

Objective: To explore miRNAs mediate demethylation suppressing B7-H1 expression of gastric cancer.Methods: B7-H1 expression of AGS was detected by FACS after exposure to different concentrations of 5-Aza-Cd for five days and 100u/ml of IFN-γfor 24 hour; Different microRNA profiles between B7-H1 negative AGS after exposure to different concentrations of 5-Aza-Cd for five days and 100u/ml of IFN-γfor 24 hour and B7-H1 positive AGS after exposure to IFN-γfor 24 hour only was dectected using microRNA microarray. With the help of prediction software (Targetscan)of microRNA, seven candidate microRNAs were selected and further microRNAs targeting B7-H1 mRNA were identified by transfection of mciroRNAs mimics and dual luciferase reporter vector; Expression of microRNA was detected by quantitative PCR and methylation status of DNA in upsteam of microRNAs was tested in AGS after exposure to different concentrations of 5-Aza-Cd for five days. Relationship among 5-Aza-Cd concentration, microRNA expression and methylation status of upstream of microRNA genes was statistically analyzed finally.Results: Expression of B7-H1 in AGS gradually increased along with the concentration of 5-Aza-Cd; miR-152 and miR-200b targeting B7-H1 mRNA suppressed expression of B7-H1; 5-Aza-Cd could promote miR-152 and miR-200b expressing and reduced methylation status of upsteam of miR-152 from 15.46% to 0.23% and miR-200b from 22.2% to 37.6% with both statistical significances(p<0.05).Conclusion: Demethylation promoted expression of miR-152 and miR-200b, which targeted B7-H1 mRNA and inhibited expression of B7-H1 in AGS.