AIM:To investigate the effects of 17-AAG on apoptosis and cell cycle of HCT-15 cells and to clar-ify the related mechanisms .METHODS: MTT method was employed to evaluate the inhibitory effects of 17-AAG with Aifferent time and different doses on the proliferation of HCT-15 cells.The cells were stained with Annexin V-FITC/propid-iumiodide and measured by flow cytometry .The expression of STAT3, cyclin D1, Cyt C, caspase 9 and caspase 3 at mR-NA and protein levels was determined by RT-PCR and Western blotting .RESULTS:Treatment with 17-AAG at concentra-tion of 1.25~20 mg/L for 24 h and 48 h significantly inhibited the activity of HCT-15 cells at both time-and concentra-tion-dependent manners .Treatment with 17-AAG at concentrations of 0.425, 0.85 and 1.7 mg/L for 48 h significantly in-duced apoptosis and cell cycle arrest of HCT-15 cells.The exposure of 17-AAG at concentrations of 0.425, 0.85 and 1.7 mg/L for 48 h to the HCT-15 cells significantly down-regulated the expression of STAT 3 and cyclin D1 at mRNA and pro-tein levels, but up-regulated Cyt C, caspase 9 and caspase 3 mRNA and protein in a concentration-dependent manner . CONCLUSION:17-AAG inhibits the cell activity , induces apoptosis and G 1 arrest by down-regulating the expression of cyclin D1, and promoting the mitochondria apoptosis through STAT 3 pathway.%目的：观察17-AAG对人结直肠癌HCT-15细胞株凋亡和周期及相关分子机制的影响。方法：体外培养HCT-15细胞，分别给予不同剂量的17-AAG及不同作用时间，采用四甲基偶氮唑盐微量酶反应比色法（ MTT法）检测细胞的活力；Annexin V-FITC／PI双标记流式细胞术检测细胞凋亡；流式细胞术检测细胞周期的变化；RT-PCR和Western blotting法检测凋亡和周期相关因子的表达水平。结果：1．25～20 mg／L浓度的17-AAG作用24 h和48 h后对HCT-15细胞有显著抑制作用，且有明显的时间、剂量依赖性；0.425、0.85和1.7 mg／L浓度的17-AAG作用48 h后，各组细胞发生G1期阻滞及明显凋亡，STAT3 mRNA和蛋白的表达水平明显下降，凋亡和周期相关因子cyclin D1 mRNA和蛋白表达水平下调，Cyt C、caspase 9及caspase 3 mRNA和蛋白表达水平上调。结论：17-AAG对人结直肠癌细胞的活力具有明显抑制作用，使细胞周期发生G1期阻滞和细胞凋亡。17-AAG可能通过阻断STAT3通路下调cyclin D1而发生G1期阻滞；17-AAG可能通过阻断STAT3通路启动线粒体凋亡通路来诱导细胞凋亡。
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