ATR and ovarian serous adenocarcinoma: Moreover, similar results have been seen in a patient-derived xenograft model of BRCA-mutant high-grade serous ovarian cancer, suggesting that PARP inhibition also increases reliance on ATR-dependent G2 arrest in BRCA-deficient cells [77], thus the combination of PARP and ATR inhibition may have benefits in other HDR-deficient cancers.