Disruption of Ataxia-telangiectasia mutated kinase enhances radiation therapy efficacy in spatially-directed diffuse midline glioma models.

Diffuse midline gliomas (DMGs) are lethal brain tumors characterized by p53-inactivating mutations and oncohistone H3.3K27M mutations that rewire the cellular response to genotoxic stress. We used RCAS/tv-a retroviruses and Cre recombinase to inactivate p53 and induce native H3.3K27M mutations in a lineage- and spatially-directed manner. We generated primary mouse tumors that recapitulate human DMG. Disrupting ataxia-telangiectasia mutated kinase (ATM) enhanced the efficacy of radiation therapy in murine and patient-derived DMG models which increased survival. Microscopy-based in situ sequencing was used to spatially resolve transcriptional profiles in >750,000 single cells with or without ATM disruption and radiation therapy, revealing altered immune-neoplastic and endothelial cell interactions after treatment. An allelic series of primary murine DMG models with different p53 mutations confirmed that transactivation-independent p53 activity is a key mediator of radiosensitivity after ATM disruption. Our findings contribute primary DMG mouse models with deep profiling and reveal the mechanisms of treatment response to an actionable therapeutic strategy.