Objective To investigate the role of Cuilinl (Cul1) gene on human breast cancer cell proliferation.Methods The Cull small interfering RNA (siRNA) were transferred into MDA-MB-231 and BT-549 breast cancer cells.The expression of Cul1 gene in both cancer cells were assessed by Western blotting.The proliferation of both cancer cells after Cul1 interference were measured by cell counting kit-8 (CCK-8) assay.The cell cycle of breast cancer cells were detected by flow cytometry.The expression levels of Cyclin family (Cyclin A,Cyclin D1,Cyclin E) and CDK inhibitor proteins (p21 and p27) were detected by Western blotting.Results Cul1 siRNA could silence the expression of Cul1 gene in both breast cancer cells significantly.Cul1 interference could drastically decreased the ability of cell proliferation in both breast cancer cells and rose to its peak level at 96 h.The G1 population in both breast cancer cells treated by Cul1 siRNA [(29.49 ± 0.75) ％,(24.86 ± 0.52) ％] increased significantly than the ceils treated by control siRNA [(17.39 ± 0.56) ％,(12.73 ± 0.41) ％] at 6 h.The expression levels of Cyclin A,Cyclin D1,and Cyclin E proteins were drastically decreased in both breast cancer cells after Cul1 interference,at the same time,p21 and p27 protein expression levels was significantly increased.Conclusion Silence of Cul1 could suppress human breast cancer cell growth through down-regulation of Cyclin A,Cyclin D1,and Cyclin E proteins,up-regulation of p21 and p27 proteins making cell cycle arrest at G1 phase.