Effect of insulin glargine and human insulin on proliferation of a human breast cancer cell line MDA-MB-231

Aim: To investigate the effect of insulin glargine and human insulin on proliferation of a human breast cancer cell line MDA-MB-231 and the role of ERK in the process. Methods: MDA-MB-231 cells were incubated with insulin glargine and human insulin at different concentrations and for different time courses. A specific ERK1/2 inhibitor, PD98059, was used either alone or in combination with insulin glargine or human insulin to test the involvement of ERK pathway in cell growth. Cell proliferation was evaluated using cell counting kit-8 reagents. Cell cycle distribution was analyzed by flow cytometry. Results: Both insulin glargine and human insulin dose-dependently enhanced MDA-MB-231 cell proliferation at the concentrations from 1 to 100 IU · L-1 after treatment for 96 h. At the concentration of 10 IU · L-1, both drugs promoted cell growth at 48, 72, and 96 h. The percentage of S + G2/M cells was significantly increased in both insulin glargine and human insulin treated groups as compared to untreated controls. No significant difference was observed between insulin glargine and human insulin in their effects on cell proliferation and cell cycle distribution. Cell proliferation was significantly inhibited by PD98059. However, in the presence of PD98059, both drugs still promoted cell proliferation significantly as compared to untreated controls. Conclusions: Insulin galrgine and human insulin similarly promote proliferation of MDA-MB-231 cells independent of ERK activation.