ATRX Loss in Glioma Results in Epigenetic Dysregulation of Cell Cycle Phase Transition

Abstract

ATRX, a chromatin remodeler protein, is recurrently mutated in H3F3A-mutant pediatric glioblastoma (GBM) and IDH-mutant grade 2/3 adult glioma. Previous work has shown that ATRX-deficient GBM cells show enhanced sensitivity to irradiation, but the etiology remains unclear. We found that ATRX binds regulatory elements of cell cycle phase transition genes in GBM cells, and there is a marked reduction in Checkpoint Kinase 1 (CHEK1) expression with ATRX loss, leading to early release of G2/M entry after irradiation. ATRX-deficient cells exhibit enhanced activation of master cell cycle regulator ATM with irradiation. Addition of the ATM inhibitor AZD0156 doubles median survival in mice intra-cranially implanted with ATRX-deficient GBM cells, which is not seen in ATRX-wildtype controls. This study demonstrates that ATRX-deficient high-grade gliomas (HGGs) display epigenetic dysregulation of cell cycle phase transitions, which opens a new window for therapies targeting this unique phenotype.