In chronic myeloid leukemia (CML) Ito et al. [12] showed the Nup98/HoxA9 fusion contributed to blast crisis through HoxA9 homeodomain binding to the Msi2 promoter resulting in gene over-expression, down-regulation of the Notch1 inhibitor Numb, and loss of the proliferation/differentiation equilibrium in hematopoietic stem cells (HSCs) [13]. Here, NUMB is linked to chronic myelogenous leukemia, BCR-ABL1 positive.