Since the rapidly upregulated PARP9 and PARP14 genes encode key survival proteins with strong anti-apoptotic effects in hematopoietic cells,20,21 their prompt simultaneous upregulation followed by the delayed induction of MCL-1L expression might explain the marked anti-apoptotic effect of IFNγ on imatinib treated CML stem/progenitor cells. Here, IFNG is linked to chronic myelogenous leukemia, BCR-ABL1 positive.