Induction of miR-31 causes increased sensitivity to 5-FU and decreased migration and cell invasion in gastric adenocarcinoma.

Drug resistance is the main obstacle in the treatment of gastric cancer, the third most common cause of cancer-related death in the world. Due to their small size, easy entrance to cells and multiple targets, microRNAs (miRs) are considered novel and attractive targets. In the current study, parental MKN-45, MKN-45-control vector, and MKN-45-miR-31 populations were compared in terms of cell cycle transitions, migration, cell invasion, and proliferation. In addition, downstream targets of miR-31, including E2F6, and SMUG1 were examined using Real-time RT-PCR and western blotting. MKN-45-miR-31 showed an increased sensitivity to 5-FU, decreased migration and cell invasion compared to the control groups (p = 0.0001, p = 0.01 and p = 0.01, respectively). There was a significant increase in the percentage of cells in G1/pre-G1 phase in MKN-45-miR-31 relative to the control groups (p = 0.001). Induction of miR-31 expression in MKN-45 caused a significant reduction of E2F6 and SMUG1 genes. Our findings indicated that induction of miR-31 expression could increase drug sensitivity, and diminish tumor cell migration and invasion of gastric cancer cells. Therefore, miR-31 can be considered as a potential target molecule in the targeted therapy of gastric cancer (Fig. 2, Ref. 43). Keywords: gastric cancer, miR-31, drug resistance, E2F6, SMUG1.