ATR and cancer: Other players involved in DDR can also be found defective in cancer, including breast cancer susceptibility gene 2 (BRCA2), RAD51, RAD52, partner and localizer of BRCA2 (PALB2), ataxia-telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3-related (ATR), constituting additional encouraging targets for cancer treatment [6,20].