Tracing Hypoxic State and Hypoxia Memory in Glioblastoma Progression

Hypoxia is linked to worse prognosis for cancers, including glioblastoma (GBM), the most common and highly lethal primary brain tumor. Hypoxic tumor cells are thought to be better equipped to survive therapy and spawn tumor recurrence, however, the trajectory of hypoxic cells during GBM expansion and their roles in recurrent GBM after therapy remain poorly understood. The main goal of this proposal is to apply a dual genetically encoded hypoxia-sensitive reporter system with lineage tracing capability to systematically characterize hypoxic tumor cells during GBM progression. The dual reporter system distinguishes tumor cells that are acutely hypoxic (marked by green fluorescence) from those with a history of hypoxia exposure (permanently marked with red fluorescence). Their cell fate will be traced across time and space during GBM progression in both primary and recurrent GBM models. The cellular study will be coupled with gene expression analysis on single cell level to unravel the molecular underpinning of malignant potency of hypoxic tumor cells. By comparing transcription profiles of acutely hypoxic versus hypoxia-exposed cells in primary and recurrent GBM, we will test the hypothesis that there exists a hypoxia memory, i.e., hypoxia-exposed cells retaining a set of hypoxia-induced genes that may be linked to survival fitness and tumorigenic potential. In conjunction to the descriptive part of our study, we have also devised a genetic platform to selectively ablate hypoxic population with temporal control to study their contribution to tumor progression in both primary and recurrent GBM. This functional data will provide direct evidence to test the central hypothesis that hypoxia contributes to tumor progression, and more importantly, tumor relapse after treatment. In summary, our innovative study will gain new insights into the link between hypoxia and GBM malignancy, and set the stage for the discovery of new prognostic tools and therapeutics targets to combat GBM.