We depleted ATM from the prostate cancer cell line PC-3 using CRISPR/Cas9 and found that although olaparib reduced cell proliferation, ATM-deficient cells did not undergo apoptosis unless olaparib was combined with an ATR inhibitor, either VE-821, as in [61] or AZD6738 [71], an ATR inhibitor in clinical trials [72]. Here, ATR is linked to prostate carcinoma.