Abstract
INTRODUCTION: Glioblastoma multiforme (GBM) remains a challenge for clinicians due to resistance to conventional treatment with the DNA-damaging agent temozolomide (TMZ) and radiation. Improving outcomes has become imperative and there is a growing interest in targeting cancer cell metabolism. Based on work from our group and others, the metabolic autophagy pathway has emerged as a promising therapeutic target. There are a large number of clinical trials based on the autophagy inhibitor hydroxychloroquine (HCQ) and chloroquine (CQ), including a multi-centre Phase II study set up by our institution. While in established GBM cell lines autophagy acts as a pro-survival signal upon radiation, its role in GBM-initiating neural stem cells (GNS) in response to genotoxic stress is unknown.The objective of the present work is to investigate the role of autophagy in regulation of TMZ sensitivity in GNS. METHOD: We inhibited autophagy by pharmacological means and by stable knockdown of the essential autophagy gene ATG7. To study the response to TMZ, we have used viability assays, growth curves and western blots. RESULTS: Our findings show that both genetic and pharmacological inhibition of autophagy sensitises MGMT+ GNS cells to TMZ. In contrast, autophagy suppression does not affect the response to TMZ in MGMT- GNS cells, as well as in cells that have developed resistance via loss of hMSH6. Notably, autophagy inhibition results in downregulation of MGMT via a posttranscriptional mechanism. CONCLUSION: Modulation of MGMT is clinically relevant and this study has the potential to increase our understanding of mechanisms regulating sensitivity to DNA damaging agents in GBM.