Mir-497 Regulates Cisplatin Resistance of Human Gastric Cancer Cell Line by Targeting IGF1R, IRS1 and BCL2

Purpose: Studies showed that drug resistance of gastric cancer cells could be modulated by the abnormal expression of miRNAs which targeted multiple cell signal pathways. Here we aimed to investigate the possible role of miR-497 in the development of cisplatin resistance in human gastric cancer cell line. Methods: miRNA Quantitative real-time PCR was used to detect the different miRNAs expression level between drug resistant and parental cancer cells. MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was used to test the drug resistance phenotype changes of cancer cells via over or down regulation of miRNAs. Dual-luciferase activity assay was used to verify the target genes of miRNAs. Western blot analysis, Immunohistochemistry, Immunofluorescence staining, Cell proliferation assay, clonogenic assay and apoptosis assay were used to elucidate the mechanism of miRNAs on modulating drug resistance of cancer cells. Results: miR-497 was significantly down-regulated in both gastric cancer tissues and various gastric cancer cell lines. Moreover, it was down-regulated in cisplatin-resistant gastric cancer cell line SGC7901/cisplatin (DDP) and the down-regulation of miR-497 was concurrent with the up-regulation of IGF1R/ IRS1 pathway related proteins, such as IGF1R, IRS1 and BCL2, compared with the parental SGC7901 cell line, respectively. In vitro drug sensitivity assay demonstrated that over-expression of miR-497 sensitized SGC7901/DDP cells to cisplatin. The luciferase activity of the above proteins 3'-untranslated regionbased reporters constructed respectively in SGC7901/DDP cells suggested that IGF1R, IRS1 and BCL2 were all the direct target genes of miR-497. Enforced miR-497 expression reduced its target proteins level, inhibited SGC7901/ DDP cells proliferation and sensitized SGC7901/DDP cells to DDP-induced apoptosis. Conclusions: Our findings suggested that hsa-miR-497 could modulate cisplatin resistance of human gastric cancer cell line at least in part by targeting IGF1R/IRS1 pathway.