Objective To study the effect of cinobufagin (CB) on the proliferation inhibition and induction of apoptosis in glioblastoma cell lines U87 and its molecular mechanism. Methods A gradient concentration (0-20 μmol/L) of CB was used to treat the U87 glioma cells for 6 h, 12 h, 24 h and 48 h, respectively. Cell viabilities were determined by CCK-8 assay to discover the effects of different concentrations of CB on the proliferation of glioma cells. Different concentrations (1-20 μmol/L) of CB were used to treat the U87 glioma cells for 12 h and 24 h, hochest33342 staining assay was used to assess the apoptosis levels. Immunofluorescence staining was used to determine the expression of growth related proteins phospho-protein kinase B(T308)〔 p-AKT(T308)〕 in U87 glioma cells after being treated with CB for 24 h. Western blot was used to determine the apoptotic related proteins (BAX, cleaved-caspase 3, cleaved-caspase 9) and growth related proteins 〔phospho-inositide 3-kinase (p-PI3K), p-AKT(T308), p-AKT(S473), phospho-ribosomal protein S6 kinase (PS6), phospho-4E-binding protein 1 (p-4EBP1)〕. Results A significant effect of CB on the proliferation inhibition and induction of apoptosis in U87 glioma cells in a time- and dose-dependent manner was observed. Treatment with CB induced the expression levels of apoptosis-related protein, cleaved-caspase 3 and BAX, and the PI3K-AKT-4EBP1 signaling pathway related proteins p-AKT(T308) and p-4EBP1 were decreased. Conclusion CB can inhibit U87 glioma cells growth and induce apoptosis, which may involve the PI3K-AKT-4EBP1 and BAX-caspase signaling pathways.
