| In present,　tumor is a leading cause of human death in the world. Surgery,which almost invariably leaves behind some malignant cells, the standard treatment for most tumors continues to be radiation and chemotherapy. However, previous anti-tumor agents have limited effectiveness and leave patients weak and nauseated. Researchers are focusing on searching for new anti-tumor drugs. Chemical agents with strong activity but minimal toxicity would be expected to have potential utility as anti-tumor drugs.Apoptosis, also known as programmed cell death, plays a key role in tissue development and removal of damaged and premalignant cells. Apoptotic cells distinct from necrosis, appear to have characteristic changes including chromatin condensation, DNA fragmentation ,apoptotic bodies formation. Abnormal regulation of apoptosis has been implicated in tumor development. This mode of cell death has recently become a focus of interest in oncology and may also shed light on cancer therapy.Cancer differentiation treatment has become a new field of cancer therapy. Since dimethylsufoxide has been found to induce the differentiation of leukemia cells in vitro, many laboratories are intensively looking for effective inducers. The widely used model is the human leukemia cell HL-60.Diosgenin , a plant steroid, has been first isolated from Dioscorea tokoro in 1930.Diosgenin has been reported to be a anti-tumor agent, but ,the mechanism of anti-tumor is distinct. It has been reported that diosgenin induces differentiation of human erthroleukemia cell line(HEL TIB 180)through changing lipoxygenase activities[18]. Recently, diosgenin has been reported to induce apoptosis,cell cycle arrest in human osterosaroma 1547 cell line [22] .However ,the precise mechanism of diosgenin-induced apoptosis is still unclear. In addition, diosgenin was used to treat osteoporosis in the ovariectomized adult rat model[23]. There hasn,t any report whether diosgenin induces differentiation and apoptosis of human leukemia cell line(HL-60).The aim of our study is to investigate the apoptotic and differentiated effect of diosgenin on human leukemia cells and the mechanisms of diosgenin-induced HL-60 cell apoptosis. The present study shows that diosgenin inhibit HL-60 cell growth in a time-and dose-dependent manner. By morphological methods, NBT reduction test and phagocytosis test, diosgenin induced HL-60 cell differentiation at a concentration of 3.750mg?L-1 are demonstrated .It wat found that diosgenin-treated HL-60 cells differentiated mainly along the granulocytic lineage,as judged by analysis of cell-surface antigens.The plant steroid, diosgenin may be a potent inducer of differentiation of leukemic cells.We need to study the mechanism of diosgenin-induced HL-60 cell differentiation.We also study whether Diosgenin might induce apoptosis in human leukemia HL-60 cells. By morphological and biochemical methods, we found changes in cell morphology, such as condensation of chromatin, nuclear fragmentation, and apoptotic bodies, which were the most reliable markers of apoptosis. The appearance of a ladder-like DNA fragmentation pattern from Diosgenin treated HL-60 cells was shown in our experiment,which were detected by gel electrophoresis. In addition, the flow cytometric methods of identifying apoptotic cells-Annexin V-FITC Apoptosis kit and APO-BRDU kit were used. The results demonstrated strongly the occurrence of apoptosis in HL-60 cells treated with diosgenin in vitro.Diosgenin induces HL-60 cell apoptosis in lower concentrations and causes cell cycle arrest at G0/G1 phase by analysis of cell cycle distribution.Since Caspase-3 play major role in apoptosis,we study the effect of this protein on diosgenin-induced HL-60 cell apoptosis.Caspase-3 inhibitor partially blocked diosgenin-induced HL-60 cell death.The inhibitory rate is 24.63%. Caspase -3 activity of HL-60 cells induced with 7.500 and 15.000mg?L-1 diosgenin for 6h were detected by fluorescent quantitative assay. The Caspase-3 activity of induced cells increased signifi...
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