Abstract: Objective:To investigate the effect of rhaponticin on apoptosis in human breast cancer SK-BR-3 cells.Methods:SK-BR-3 cells were treated with rhaponticin at the concentrations of 100,200,and 400 mol/L.Apoptosis was examined with Annexin V-FITC Apoptosis Detection Kit by flow cytometry.The expressions of Bcl-2 and Bax protein were analyzed by Western blot.caspase-3 activity was detected by special kit.Results:Rhaponticin induced obvious early apoptosis in SK-BR-3 cells in a concentration-dependent manner(P0.05 to P0.01).Western blot results showed that rhaponticin enhanced the expression of Bax protein,and inhibited the expression of Bcl-2 protein,which was gradually down-regulated following the increase of rhaponticin's concentration(P0.01).Meanwhile,rhaponticin induced the activation of caspase-3,and caspase-3 activity was increased with its concentration(P0.01).Conclusions:Rhaponticin can induce apoptosis in SK-BR-3 cells,which may be correlated to the down-regulation of Bcl-2,the upregulation of Bax,and the activation of caspase-3.