miR‐506 enhances the sensitivity of human colorectal cancer cells to oxaliplatin by suppressing MDR1/P‐gp expression

Abstract Objectives Chemoresistance development represents a major obstacle to the successful treatment of colorectal cancer ( CRC ). The aim of this study was to elucidate the mechanism by which miR‐506 reverses oxaliplatin chemoresistance in CRC . Methods In this study, miR‐506 levels were measured in 74 patients with colon cancer via quantitative real‐time polymerase chain reaction ( qRT ‐ PCR ) and in situ hybridization ( ISH ). We subsequently analysed the relationship between miR‐506 expression and CRC patient survival via the Kaplan‐Meier method. MTT assay demonstrated the fractional survival rates and cell viability of HCT 116‐OxR, HCT 116‐OxR‐miR‐Ctrl and HCT 116‐OxR‐miR‐506 cells treated with oxaliplatin at different concentrations. Cell proliferation and apoptosis were assessed via flow cytometry ( FCM ) analysis and apoptosis assay. MDR 1 mRNA expression and P‐gp protein expression were assessed via qRT ‐ PCR and Western blotting ( WB ) respectively. Immunofluorescence (IF) staining demonstrated P‐gp expression in HCT 116‐OxR and HCT 116‐OxR‐miR‐506 cells. qRT ‐ PCR and WB were used to detect Wnt/β‐catenin pathway activity after miR‐506 overexpression. Results In the present study, in ISH and qRT ‐ PCR results demonstrated that miR‐506 is weakly expressed in chemoresistant CRC tissues. The low miR‐506 expression group exhibited lower 5‐year OS and lower 5‐year RFS than the high miR‐506 expression group. miR‐506 overexpression inhibited cell growth and increased oxaliplatin‐induced cell apoptosis in HCT 116‐OxR cells, as shown via FCM and apoptosis assay. We subsequently noted low MDR 1/P‐gp expression in HCT 116‐OxR‐miR‐506 cells via qRT ‐ PCR , WB and IF. Lastly, we demonstrated low MDR 1/P‐gp expression in HCT 116‐OxR‐miR‐506 cells via inhibition of the Wnt/β‐catenin by WB , MTT and FCM analysis. Conclusion Taken together, the findings of our study demonstrate that miR‐506 overexpression in HCT 116‐OxR cells enhances oxaliplatin sensitivity by inhibiting MDR 1/P‐gp expression via down‐regulation of the Wnt/β‐catenin pathway and thus provide a rationale for the development of mi RNA ‐based strategies to reverse oxaliplatin resistance in CRC cells.