While the expression of p210-BCR-ABL mRNA in BM myeloid progenitors (Lin− cKit+, LK cells) derived from primary and secondary recipient mice was similar (Supplementary Figure 3C), we observed a dramatic upregulation of p210-BCR-ABL, both at the mRNA and protein levels, in B-cell progenitors derived from secondary recipient B-ALL mice (Fig. 2j, k). Here, KIT is linked to acute lymphoblastic leukemia.