| 摘要: | In recent years, some extract from plants was found to have anti-tumor effects, such as denbinobin from Shi-Hu, and zerumbone, from subtropical ginger Zingiber zerumbet Smith. Denbinobin, a phenanthraquinone derivative, and zerumbone, a sesquiterpene compound, were both shown to exert antitumor activities in several types of cancer cell lines. However, the precise mechanisms underlying cell death remain unclear. In this study, we investigated the apoptotic signaling cascade elicited by denbinobin and zerumbone in human glioblastoma multiforme (GBM) cells. Denbinobin and zerumbone concentration-dependently caused a decrease in the cell viability of GBM cells. A flow cytometric analysis of propidium iodide (PI)-stained cells demonstrated that denbinobin and zerumbone induced GBM cell apoptosis. Denbinobin and zerumbone evoked caspase-3 activation and degradation of poly (ADP-ribose) polymerase (PARP). N-benzyloxycarbonyl- Val-Ala-Asp- fluoromethylketone (zVAD-fmk), a broad-spectrum caspase inhibitor, prevented denbinobin- and zerumbone- induced cell death. In addition, denbinobin- and zerumbone- induced cell death were diminished by the transfection of wild-type (WT) Akt or IκB kinase (IKK) into GBM cells. Denbinobin and zerumbone reduced IKK phosphorylation in a time-dependent manner, and denbinobin- and zerumbone- dephosphorylated IKK were accompanied by a decrease in Akt phosphorylation. The phosphorylation status of forkhead in rhabdomyosarcoma (FKHR), a downstream signal molecule of Akt, was also diminished by the presence of denbinobin or zerumbone. Furthermore, transfection of GBM cells with WT IKKα markedly suppressed the decreases in Akt and FKHR phosphorylation caused by denbinobin or zerumbone. In contrast, transfection with WT IKKβ only slightly affected denbinobin’s or zerumbone’s action against IKK, Akt, and FKHR. These results suggest that IKKα inactivation, followed by Akt and FKHR dephosphorylation and caspase-3 activation, contributes to denbinobin- and zerumbone- induced GBM cell apoptosis. |
