The Mechanism Research Of Radiosensitization To Human U251Glioma Cell Line In Vitro Induced By Elemene

ObjectiveElemene(1-methyl-1-vinyl-2,4-diisopropenyl-cyclohexane),a natura lly occurring compound is extracted from the traditional Chinese medicinal herb curcuma wenyujin. As one of the national class II novel antitumor drugs in China,elemene has been shown to be effective against a wide range of tumours and fewer side effects than other cytotoxic agents in vitro and in vivo. Recently elemene has been demonstrated to enhance the sensitivity of human cancer cell lines in vitro and of carcinoma xenograft in vivo to radiation treatment.We have also recently shown that elemene can promote the radiosensitivity of U251Human glioma cell line in vitro.The underlying mechanism, however, is still unclear. In this study, we investigate the mechanism of it.MethodsInhibitive effect of elemene on U251cells and enhancement of radiosensitivity to U251cells incubated with elemene(40mg/L) were performed by the3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.U251cells were divided into four groups:control group, elemene group(40mg/L), irradiation group(3Gy) and combination group.Cell cycle and apoptosis of U251cells with different treatments were measured by flow cytometry,respectively. The expression of corresponding cell cycle control protein and apoptosis related protein was assayed by western blotting. The flow cytometry results and western blot results were assayed by two way ANOVA.ResultsThe fifty percent inhibit on concentration (IC50) of elemene against glioma cells after24h was72.04mg/L. Deducted elemene toxic effect,the cell growth inhibition rate of elemene and radiation combined group(40mg/L+2Gy/4Gy/6Gy/8Gy) was significantly increased (P<0.05) compared with the same radiation dose group performed by MTT assay in vitro. The cell apoptosis of combination (23.98%) compared with radiation group (9.45%) was significantly increased (P=0.000), and the G2/M period cells rate increased from6.63%to18.89%(P=0.000). Elemene and radiation existed interaction on cyclin B1expression (P=0.007). The cyclin B1relative expression of radiation was0.49which compared with control group (0.30) was significantly improved (P=0.021). But the cyclin B1relative expression of combination group was significantly reduced to0.20(P=0.002,compared with radiation group). Elemene could significantly reduce expression of cdc2, p-cdc2(Thrl61) and survivin (P<0.05).ConclutionElemene may enhance glioma U251cells radiasensitivity in vitro by reducing cdc2, p-cdc2(Thr161) and radiation-induced cyclinB1expression which can block cell cycle in G2/M period, and inhibiting survivm expression.