Objective To investigate the effects of isoalantolactone on proliferation and apoptosis of human bladder cancerT2 4 cells and its mechanism. Methods CDT2 4 cells in the logarithmic phase were divided into the groups 1, 2, 3, 4, 5 and 6; cells in the groups 1-5 (experimental group) were added with different concentrations of isoalantolactone (5, 10, 20, 40, and 80 μmoVL), and group 6 with normal culture medium (control group) ; after 24, 48, 72 h of culture, the cell proliferation ab山ty of each group was detected by C C K-8 method. (2) T24 cells were divided into the groups A, B, C, D, and E; cells in the group A were cultured in medium without isoalantolactone, cells in the groups B and E were pretreated with 5 nmol/L N-acetylcysteine (NAC ) for 2 h, and cells in the groups C, D and E were cultured with 10, 20 and 20 μmol/L isoalantolactone; after 24 hours of culture, the apoptosis rate of each group was measured by flow cytometry, the level of reactive oxygen species (ROS) was detected by DC FH-DA, and the mitochondrial membrane potential was detected by JC-1 mitochondrial membrane potential. @ T24 cells were divided into 4 groups with 6 compound wells in each group; cells in the three groups were added with 10, 20 and 40 μ,moVL isoalantolactone, and cells in the other group were treated with culture medium without isoalantolactone (control group) ; after 24 hours of culture, Western blotting was used to detect apoptosis-related proteins Bax, B-lymphocyticoma-2 (Bcl-2), Cytochrome C, and Caspase-3. Results (D Compared with the group 1, the inh山山on rate of cell proliferation increased in the groups 2, 3, 4 and 5 (all P < 0. 05) ; compared with the group 2, the inhibition rate of cell proliferation increased in the groups 3, 4 and 5 (all P < 0. 05) ; compared with the group 3, the inh如tion rate of cell proliferation increased in the groups 4 and 5 (all P < 0. 05). @ Compared with the group A, the apoptosis rate and ROS content increased in the groups C and D (all P < 0. 05) ; compared with the group C, the apoptosis rate and ROS content increased in the group D (all P < 0. 05) ; compared with the group D, the apoptosis rate and ROS content were reduced in the group E (all P < 0. 05). Compared with the group A, the mitochondrial membrane potential of group C decreased (P < 0. 05). Compared with the group C, the mitochondrial membrane potential of group D decreased (P < 0. 05) ; compared with the group D, the cell mitochondrial membrane potential increased in the group E (P < 0. 05). @ Compared with the control group, the relative expression levels of Bax, Cytochrome C and Caspase-3 in the drug groups increased, and the relative expression levels of Bcl-2 decreased (all P <0 . 05); with the increase of concentration, the relative expression levels of Bax, Cytochrome C and Caspase-3 in the drug group increased, and the relative expression levels of Bcl-2 decreased (all P <0. 05). Co nclusion lsoala ntolactone can inhibit cell proliferation and induce apoptosis by promoting the accumulation of reactive oxygen specie, decreasing the mitochondrial membrane potential and regulating the expression of apoptosis-related proteins [ABSTRACT FROM AUTHOR]