Abstract： Objective To investigate the effects of MMI-166 on apoptosis and apoptosis-related protein expression of human pancreatic cancer SW1990 cells and its transplanted tumor,and explore possible mechanism.Methods The human pancreatic cancer xenograft model was constructed by using human pancreatic cancer SW1990 cells.Tumor-bearing nude mice were randomly divided into control and MMI-166 groups,and they were treated with normal saline or MMI-166 (200 mg · kg-1 · d-1) for 28 days.Apoptosis index (AI),p53,c-Myc,Bax,Bcl-2,Survivin,Caspase-1,Fas proteins were detected by deoxynucl-eotidyl transferase-mediated nick end labeling (TUNEL method) and Western blot.MMI-166 of different concentrations (0,50,100 μg/ml) were used to treat human pancreatic cancer SW1990 cell for 24 h.The c-Myc,Survivin proteins expressions were measured by Western blotting.Results Apoptosis index in MMI-166 group was 81.1 ±7.9,which was significantly higher than that in control group (21.3 ±2.2,P =0.000) ; the expressions of c-Myc,Survivin were 7715 ± 2229,4594 ± 1240,which were significantly higher than those in control group (16870 ± 2446,15208 ± 1903,P =0.000) ; the expressions of p53,Bax,Bcl-2,Caspase-1,Fas were not significantly different from those in control group.After 50,100 μg/ml MMI-166 treatment,the expression of c-Myc was significantly down-regulated (0.098 ± 0.003,0.073 ± 0.008 vs.0.169 ± 0.007,F =189.361,P ＜ 0.05) ; and the expression of Survivin was not significantly changed.Conclusions MMI-166 may induce cell apoptosis of SW1990 by down-regulating the expression of c-Myc.