Evidence that BRCA/DNA-PK-deficient CML leukemia stem cells are highly sensitive to inhibitors of poly-(ADP-ribose) polymerase 1 (PARP1) [60] brought about a potential of targeting key DNA repair enzymes in CML, which are in synthetic lethal relationship with BCR-ABL. The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.