1-Oxoeudesm-11(13)-eno-12,8a-lactone induces G2/M arrest and apoptosis of human glioblastoma cells in vitro

Abstract

To investigate the effects of 1-oxoeudesm-11(13)eno-12,8a-lactone (OEL), a novel eudesmane-type sesquiterpene isolated from Aster himalaicus, on the cell cycle and apoptosis in human glioblastoma cells in vitro. Human malignant glioblastoma cell lines U87 and A172 were used. The cytotoxicity of OEL was examined using the MTT assay. Cell apoptosis was assessed with DAPI staining and flow cytometry. DNA damage was determined by measuring the phosphorylation of H2AX using immunofluorescence staining and Western blotting. Cell cycle profiles were measured with flow cytometry. The mRNA expression of p53 and p21Waf1/Cip1 was investigated using real-time PCR. The protein expression of γ-H2AX, caspase-9, caspase-3, p53, p21Waf1/Cip1, cyclin B1, and cdc2 was analyzed with Western blotting. Treatment of the malignant glioblastoma cells with OEL inhibited the cell growth in dose- and time-dependent manners (the values of IC(50) at 48 and 72 h were 29.5 and 16.99 μmol/L, respectively, in U87 cells; 7.2 and 9.5 μmol/L, respectively, in A172 cells). OEL (10-30 μmol/L) induced apoptosis and G(2)/M phase arrest in both U87 and A172 cells. OEL induced the phosphorylation of cdc2, a G(2)/M phase cyclin-dependent kinase, and decreased the expression of cyclin B1 required for progression through the G(2)/M phase in U87 cells. The compound remarkably increased the phosphorylation of H2AX in U87 cells. Moreover, OEL increased the mRNA and protein levels of p53 and its target gene p21(Waf1/Cip1) in U87 cells. The compound also induced p53 phosphorylation. Pretreatment with PFT-α, a specific inhibitor of p53 transcriptional activity, could partially reverse the inhibition of OEL on the viability of U87 and A172 cells. OEL suppresses the growth of human glioblastoma cells in vitro via inducing DNA damage, p53-mediated cell cycle arrest and apoptosis, thus warrants further studies as a lead compound of anti-glioblastoma drug.