IKZF1 and leukemia: More rapid onset of leukemia in aged p190 BCR-ABL1 cells or more efficient leukemogenesis probably reflects more ‘target’ cells being transformed which, in turn, would increase the probability of the acquisition of secondary genetic abnormalities such as IKZF1 deletion which, at least for leukemia in patients with BCR-ABL1+ ALL, appear to be critical for malignant progression [8].