Objective:To investigate the effect of human insulin and insulin analogues combined with or without metformin on the proliferation of human mammary carcinoma cell line MCF-7. Methods:Firstly,human mammary carcinoma cell line(MCF-7) was treated with different concentrations(1,10,100,1 000 nmol/L) of insulin analogues or human insulin. Secondly,MCF-7 cells was treated with insulin analogues or human insulin at the concentration of 1 000 nmol/L,and the cell proliferation was tested by CCK-8 assay after 24 h,48 h and 72 h treatment. Thirdly,MCF-7 cells were treated with different concentrations(0,2.5,5,10,20 mmol/L) of metformin combined with human insulin or insulin analogues(1 000 nmol/L each). The proliferation of MCF-7 cells was also examined by CCK-8 assay. Results:Both insulin analogues and human insulin could increase the proliferation of cell line MCF-7. Glargine,Lispro and human insulin had a dose-and time-dependent effect on the cell proliferation while Detemir and Aspart had only a time-dependent effect. Metfomin could inhibit the proliferation of MCF-7 cells in a dose-dependent response. Metformin could decrease the effect on the proliferation that was induced by human insulin and insulin analogues. Conclusion:Human insulin and insulin analogues couid increase the proliferation of human mammary carcinoma cell line MCF-7. Metformin could decrease the proliferation of MCF-7 induced by human insulin and insulin analogues.