Combination treatment of TRAIL, DFMO and radiation for malignant glioma cells.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has shown potent and cancer-selective killing activity and drawn considerable attention as a promising therapy for cancer. Another promising cancer therapy is difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, which is oraly administered and well tolerated. Nevertheless, many types of cancer, including gliomas, have exhibited resistance to TRAIL-induced apoptosis and similarly the potency of DFMO should be enhanced to optimize therapeutic efficacy. In this study we sought to determine whether DFMO, in combination with TRAIL and radiation, could result in an enhanced anti-glioma effect in vitro. We investigated the effect of DFMO, TRAIL and radiation in various combinations on a panel of glioblastoma cell lines (A172, T98G, D54, U251MG). Viability and proliferation of the cells were examined with trypan blue exclusion assay, crystal violet and xCELLigence system. Apoptosis (Annexin-PI), cell cycle and activation of caspase-8 were tested with flow cytometry. BAD protein levels were determined by Western blot analysis. DFMO induced BAD overexpression. Combination treatment with DFMO, TRAIL and radiation significantly reduced cell viability in all cell lines tested. Increased induction of cell death and cell cycle arrest was confirmed with flow cytometry in A172 and D54 cell lines, while enhanced activation of annexin and caspase-8 was revealed in U251MG and T98G cells. The treatment of glioblastoma cell lines with combination of DFMO, TRAIL and radiation showed an enhanced effect. This combination treatment may represent a novel strategy for targeting glioblastoma.