This finding suggests that cancers with DNA repair deficiency due to the mutations in HRR pathway-associated genes apart from BRCA1/2 could synergistically respond to the specific combinations of PARP and ATR inhibitors, and the combination strategy of PARP and DDR inhibitors could probably be expanded to treat other DNA repair-deficient cancers besides BRCA1/2-deficient cancers. Here, BRCA1 is linked to cancer.