The inflammatory micro-environment induced by targeted CNS radiotherapy is underpinned by disruption of DNA methylation

Although targeted radiotherapy (RT) is integral to the increasing survival of cancer patients, it has significant side-effects, the cellular and molecular mechanisms of which are not fully understood. During RT epigenetic changes occur in neoplastic tissue, but few studies have assessed these in non-neoplastic tissue and results are highly variable. Using bulk DNA methylation and RNA sequencing as well as spatial transcriptomics (ST) in a unique cohort of patient tissue samples, we show distinct differences in DNA methylation patterns in irradiated brain tissue, whilst ST characterisation identifies specific micro-environmental niches present after irradiation and highlights neuropeptides that could be propagating neuroinflammation. We also show that in a cerebral organoid (CO) model of early changes in neurons after irradiation there are similar DNA methylation alterations and disruption of the DNA methylation machinery, suggesting that early but persistent epigenetic dysregulation plays a role in neurotoxicity. We provide a link between radiotherapy induced neuroinflammation and disruption of DNA methylation for the first time and suggest possible driving mechanisms for this chronic neuroinflammation. ### Competing Interest Statement The authors have declared no competing interest.