Radt-28. disruption of bioenergetics enhances radio-sensitivity of patient-derived glioblastoma tumorspheres

Abstract INTRODUCTION Glioblastoma (GBM), the most common primary brain tumor, has been associated with poor prognosis despite various treatment modalities, the surgical resection accompanied by chemotherapy and radiotherapy. Although the importance of radiotherapy is well known, its combination with bioenergetics regulators has not been established in clinical practice. Here, we hypothesized that bioenergetics regulators improve the radio-sensitivity of GBM-tumorspheres (TS). METHODS Gene expression profiles of GBM patient-derived TSs were obtained from microarray. In vitro efficacies of the treatment were evaluated using clonogenic assay, 3D invasion assay, neurosphere-formation assay, and apoptosis-analysis. Protein expression was evaluated by western blot, and immunofluorescence was performed for detection of γH2AX foci. In vivo efficacies were confirmed using a mouse orthotopic-xenograft model. RESULTS GBM TSs with high-radioresistant or low-radioresistant were selected according to expression levels of radiation response associated genes. In order to select the bioenergetics regulators that significantly increased the radiotherapy effect of GBM-TSs, five bioenergetics regulators were combined which are oxidative-phosphorylation (OxPhos) inhibitor (IM156A), aldehyde-dehydrogenase inhibitor (gossypol) + OxPhos inhibitor (phenformin), fatty acid oxidation inhibitor (etomoxir), pentose-phosphate pathway inhibitor (dehydroepiandrosterone; DHEA) and glycolysis inhibitor (2-deoxy-D-glucose; 2DG). Amongst of these five bioenergetics regulators, DHEA and 2DG significantly augmented the therapeutic efficacies of ionizing radiation (IR) by reducing the survival fraction, stemness, and invasiveness in both high-radioresistant and low-radioresistant GBM TSs. IR combined with bioenergetics regulators (DHEA or 2DG) induced DNA damage response and apoptosis in low-radioresistant GBM TSs. In vivo experiments using a mouse orthotopic-xenograft model confirmed the tendency to prolong survival period and reduced the size in tumor after the combined treatment of 2DG with IR in low-radioresistant GBM TS. CONCLUSION These data proposes that the combination of bioenergetics regulators and radiotherapy is more effective than IR monotherapy itself. We expect that this combination regimen can strategically establish as a future treatment practice of GBM.