Objective: To study the mechanism of K562 leukemia cells proliferation and apoptosis induced by emodin. Methods: Inhibitory effect of emodin on proliferation of K562 leukemia cells was assayed by MTT method. The morphologic changes of K562 cells were observed under microscop after Wight-Giemsa staining. Apoptosis was checked by Annexin V/PI. The changes of cell cycle and apoptosis were detected by flow cytometry. The activities of Caspase-3

8

9 were checked by chromatometry to analyze the apoptosis of K562 cells. Results: The proliferation of K562 leukemia cells was significantly inhibited by emodin. The IC50 of K562 cells inhibited with emodin for 24 h

48 h and 72 h were 80

50 and 40 μmol/L respectively. Typical morphological changes of K562 cells were observed by microscopy. The proliferation of K562 cells was obviously inhibited in dose-dependent manner. In Annexin V/PI

emodin induced K562 cells toward apoptosis in dose-dependent manner(P<0.01). The result of flow cytometry indicated that the cell cycle was blocked in G0/G1 phase (P<0.01). After treated with emodin

the activities of Caspase-3

8

9 were significantly higher than those in the normal control (P<0.01). Conclusion:Emodin inhibits proliferation and induces apoptosis ofK562 leukemia cells

and up-regulatingthe experession of Caspase may be one of its mechanisms.