Metformin up-regulated miR-107 expression and enhanced the inhibitory effect of miR-107 on gastric cancer growth.

Gastric cancer (GC) is one of the most common malignant neoplasms and is the third leading cause of cancer-related death around the world. Metformin has been well reported to have an inhibitory effect on the growth of various cancers by regulating the expression of microRNAs (miRNAs). However, the specific miRNA(s) regulated by metformin in GC have not been identified. In this study, real-time reverse transcription polymerase chain reaction (RT-PCR) analysis indicated that miR-107 expression was up-regulated in metformin-treated SGC-7901 cells compared with untreated SGC-7901 and MGC803 cells. Amplification of miR-107 expression further reduced cell proliferation in metformin-treated GC cells. A bioinformatics analysis showed that mitogen-activated protein kinase 8 (MAPK8) was the common target of metformin and miR-107. MAPK8 expression is associated with immune cell infiltration in GC as well as overall GC patient survival. Our study demonstrates that miR-107 enhances the anti-cancer effects of metformin in GC tissues, which offers a novel strategy for the treatment of GC.