β-elemene enhances both radiosensitivity and chemosensitivity of glioblastoma cells through the inhibition of the ATM signaling pathway

Glioblastoma multiforme (GBM), a tumor associated with poor prognosis, is known to be resistant to radiotherapy and alkylating agents such as temozolomide (TMZ). beta-elemene, a monomer found in Chinese traditional herbs extracted from Curcuma wenyujin, is currently being used as an antitumor drug for different types of tumors including GBM. In the present study, we investigated the roles of beta-elemene in the radiosensitivity and chemosensitivity of GBM cells. Human GBM cell lines U87-MG, T98G, U251, LN229 and rat C6 cells were treated with beta-elemene combined with radiation or TMZ. We used MTT and colony forming assays to evaluate the proliferation and survival of the cells, and the comet assay to observe DNA damage. Expression of proteins was analyzed by immunoblotting. In the present study, we found that beta-elemene inhibited the proliferation and survival of different GBM cell lines when combined with radiotherapy or TMZ via inhibition of DNA damage repair. Treatment of GBM cells with beta-elemene decreased the phosphorylation of ataxia telangiectasia mutated (ATM), AKT and ERK following radiotherapy or chemotherapy. These results revealed that beta-elemene could significantly increase the radiosensitivity and chemosensitivity of GBM. beta-elemene may be used as a potential drug in combination with the radiotherapy and chemotherapy of GBM.