Mir-221 Expression Level Correlates With Insulin-Induced Doxorubicin Resistance in Mcf-7 Breast Cancer Cells

Objective: insulin induces anti-cancer drugs resistance in tumor cells. however, the mechanism by which insulin induces its drug resistance effects is not clear. in the present study, the expression of mir-221 in insulin-treated mcf-7 cells in response to the anti-cancer drug doxorubicin, was investigated. materials and methods: in this experimental study, cell viability was evaluated using mtt (3-[4,5 dimethylthiazol-2- yl]-2,5-diphenyl tetrazolium bromide) assay. the expression level of mir-221 was determined by real time polymerase chain reaction (rt-pcr). furthermore, the expression of insulin receptor (ir) and cleaved caspase-3 protein was assessed by western blotting. results: the results showed that treatment of the mcf-7 cells with insulin reduced the anti-cancer effects of doxorubicin. viability of naive and insulin-treated cells following doxorubicin (dox) treatment was 62.9 ± 5.7% and 79 ± 7.2%, respectively. furthermore, the expression of mir-221 in insulin-treated cells was significantly increased (2.6 ± 0.37-fold change) as compared with the control group. a significant decrease (26%) in the expression of caspase-3 protein and a significant increase (24%) in ir were observed in insulin-induced drug resistant mcf-7 cells as compared to the naive cells. conclusion: together, the data showed a positive correlation between the expression of mir-221 and ir expression, but a negative correlation with caspase3 expression, in insulin-induced drug resistant mcf-7 breast cancer cells. this could suggest a new mechanism for the role of mir-221 in cancer drugs resistance induced by insulin.