Considering this evidence, the use of ATM inhibitor could sensitize cancer cells to the PARP inhibitor Olaparib as well [152,246]; so, the ATM inhibitor KU55933 was tested in the ATM-proficient HCT116 cell line and sensitized it to PARP-inhibitor Olaparib, decreasing the colony formation number after 14 days and the depletion of p53 enhanced the sensitivity [152]. Here, PARP1 is linked to cancer.