The proliferation kinetics of MCF-7 and T47D cells were detected by MTT assay, the results of which showed that all the concentrations of human insulin used herein (5.0 IU/L, 20 IU/L, 50 IU/L, and 100 IU/L) promoted MCF-7 and T47D breast cancer cell proliferation compared with the control treatment. The gene discussed is INS; the disease is breast cancer.