BRCA1 and breast cancer: To this extent, PARP1 inhibition has proven to be successful when used in DDR deficient tumors such as BRCA1- or BRCA2-deficient breast cancer, ATM-deficient colorectal cancer [41], ATM-deficient lung cancer [42], TP53/ATM-deficient MCL [43], IGH/MYC-induced BRCA2 deficient Burkitt lymphoma [44] [and PTEN/TP53-deficient prostate cancer [45].