The underlying mechanism of deguelin regulating the cell cycle in human Burkitt’s lymphoma cell line Raji cells in vitro,and the cytotoxicity of deguelin to Raji cells and human peripheral blood monocular cells (PBMCs) were investigated.The effects of deguelin on the growth of Raji cells were studied by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium (MTT) assay.Apoptosis was detected through Hoechst 33258 staining.The effect of deguelin on the cell cycle of Raji cells was studied by a propidium iodide method.The expression levels of cyclin D1,P21 and pRb were examined by using Western blotting.The results showed that the proliferation of Raji cells was inhibited in the deguelin-treated group,with a 24-h IC 50 value of 21.61 nmol/L and a 36-h IC 50 value of 17.07 nmol/L.Proliferation in Raji cells was inhibited significantly by deguelin,while little change was observed in PBMCs.Deguelin induced G 2/M arrest in Raji cells.The expression of cyclin D1,P21 and pRb was dramatically down-regulated by deguelin in a dose-dependent manner.It was concluded that deguelin could inhibit the proliferation of Raji cells by arresting the cells at G 2/M phase and inducing the cell apoptosis.Moreover,deguelin selectively induced apoptosis of Raji cells with low toxicity to PBMCs.The antitumor effects of deguelin were related to the down-regulated expression of cyclin D1,P21 and pRb proteins. The underlying mechanism of deguelin regulating the cell cycle in human Burkitt’s lymphoma cell line Raji cells in vitro, and the cytotoxicity of deguelin to Raji cells and human peripheral blood monocular cells (PBMCs) were investigated. These effects of deguelin on the growth of Raji cells was studied by Hoechst 33258 staining. The effect of deguelin on the cell cycle of Raji cells was studied by 3- (4,5-dimethyl-2-thiazolyl) -2,5-diphenyl-2H- tetrazolium was studied by a propidium iodide method. The expression levels of cyclin D1, P21 and pRb were examined by using Western blotting. The results showed that the proliferation of Raji cells was inhibited in the deguelin-treated group, with a 24-h IC 50 value of 21.61 nmol / L and a 36-h IC50 value of 17.07 nmol / L. Proliferation in Raji cells was observed significantly by deguelin, while little change was observed in PBMCs. Deguelin induced G2 / M arrest in Raji cells. expression of cyclin D1, P21 and pRb was dramatically down-regulated by deguelin in a dose-dependent manner. It was therefore that deguelin could inhibit the proliferation of Raji cells by arresting the cells at G 2 / M phase and inducing the cell apoptosis. Moreover, deguelin selectively induced apoptosis of Raji cells with low toxicity to PBMCs. The antitumor effects of deguelin were related to the down-regulated expression of cyclin D1, P21 and pRb proteins.