Abstract: Objective: To investigate the inhibitory effect of SF2523, a dual inhibitor of BRD4 and PI3K, on the proliferation of human glioma stem cells TS576, and to preliminarily elucidate its mechanism. Methods: The human glioma stem cells TS576 were cultured and divided into control group and 0.25, 0.50,1.00 2.00 μmol·L^-1 SF2523 groups,and CCK-8 method was used to detect the survival rates of TS576 cells.The TS576 cells were divided into control group and 2 μmol·L^-1 SF2523 group,and the number of TS576 cells in various groups was detected by cell growth counting method.The TS576 cells were divided into control group, 1 and 2 μmol·L^-1 SF2523 groups,and the percentages of TS576 cells at different cell cycles in various groups were examined by flow cytometry.The TS576 cells were divided into control group, 1 and 2 μmol·L^-1 SF2523 groups,and the apoptotic rates of TS576 cells in various groups were detected by Annexin Ⅴ/PI staining. The TS576 cells were divided into control group, 1 and 2 μmol·L^-1 SF2523 groups, and the expression levels of cyclinD1, B-cell lymphoma-2(Bcl-2) and Bcl-2 associated X protein (Bax)proteins in the TS576 cells in various groups were detected by Western blotting method. Results: Compared with control group, the proliferation rates of TS576 cells in 0.25, 0.50,1.00 and 2.00 μmol·L^-1 SF2523 groups at 24, 48 and 72 h after treatment were significantly decreased (P<0.01).Compared with control group, the number of TS576 cells in 2 μmol·L^-1 SF2523 group was decreased significantly (P<0.05 or P<0.01). Compared with control group, the percentages of TS576 cells at G₁ phase in 1 and 2 μmol·L^-1 SF2523 groups were increased (P<0.05), the percentage of TS576 cells at S phase was decreased (P<0.05).The results of Annexin Ⅴ/PI staining showed that the apoptotic rates of TS576 cells in 1 and 2 μmol·L^-1 SF2523 groups were significantly increased at 72 h after treatment compared with control group (P<0.01). The results of Western blotting method showed that the expression levels of Bax protein in the TS576 cells in 1 and 2 μmol·L^-1 SF2523 groups were significantly increased (P<0.01), the expression levels of Bcl-2 and cyclinD1 were significantly decreased (P<0.05 or P<0.01), and the ratio of Bax/bcl-2 was also significantly increased (P<0.01). Conclusion: SF2523 can induce the G₁ phase arrest of TS576 cells by down-regulating the expression of cyclinD1 and promote the apoptosis of TS576 cells by up-regulating the expression of Bax and down-regulating the expression of Bcl-2, and then inhibit the proliferation of TS576 cells.

Key words: SF2523, glioma stem cells, cell proliferation, cell cycle, apoptosis