BCR and leukemia: Although there was no difference in white blood cell counts between Parp1 wild-type (Parp1+/+BATg/−) and Parp1 knockout BCR/ABL1 Tg mice (Parp1−/−BATg/−) (Supplemental Fig. 4), we found it interesting that leukemia development was delayed in Parp1−/−BATg/−; these mice survived longer than Parp1+/+BATg/− mice (Fig. 4b).