Relationship Of MiR-19a/b With Multidrug Resistance Of Human Gastric Cancer Cells

Background Multidrug resistance (MDR) is the major factor of the failure of chemotherapyof gastric cancer patients. Cytological mechanism of MDR is intricate, involving multipleprocesses including dysregulation of MicroRNAs (miRNAs). Members of miR-17-92cluster,such as miR-17, miR-92a and miR-19a/b are considered as oncomiRs influencing multiplemalignant phenotypes of gastric cancer. However, the role of miR-19a/b in MDR of gastriccancer and its underlying mechanism remains unclear.Purpose With the study on miR-19a/b and multidrug resistance of human gastric cancer cellsand regulation on PTEN, we provide new target of conversing MDR of tumor.Methods Expressions of miR-19a/b were examined in multidrug-resistant gastric cancer celllines by quantitative Real Time-PCR (qRT-PCR).Through transfecting SGC7901miR-19a/bmimic or inhibitior to alter the expression of miR-19a/b, the effect of transfection were provedby qRT-PCR.The influence of miR-19a/b on the sensitivity of gastric cancer cells toanticancer drugs were investigated by MTT assay. The effects of miR-19a/b on drug effluxwere determined by fluorescence intensity assay of intracellular adriamycin (ADR). Theeffects of miR-19a/b on drug induced apoptosis were evaluated by Fluorescence activated cellsorting assay. The proteins related to drug efflux and cell apoptosis were examined byqRT-PCR and western blot. PTEN and AKT expression and AKT phosphorylation were alsoexamined by western blot and RT-PCR after miR-19a/b transfection.Results miR-19a/b was upregulated in MDR variants SGC7901/ADR and SGC7901/VCR compared with their parental cells SGC7901. Overexpression of miR-19a/b decreased thesensitivity of gastric cancer cells to anticancer drugs and vice versa. miR-19a/b upregulationaccelerated the efflux of ADR in gastric cancer cells by increasing mdr1and P-gp levels.miR-19a/b reduced gastric cancer cells susceptibility to drug-induced apoptosis by regulatingapoptosis-related proteins, including Bcl-2and Bax. Furthermore, miR-19a/b decreasedPTEN but increased AKT and phosphorylation of AKT in gastric cancer cells.Conclusion miR-19a/b promotes MDR of gastric cancer cells through accelerating drugefflux and inhibiting drug induced apoptosis. The underlying mechanisms of miR-19a/b couldbe delineated by targeting PTEN, resulting in increased AKT phosphorylation and P-gpup-regulation.