BCR and acute lymphoblastic leukemia: TonB cells are derived from BaF3, a B-lymphoid cell line, and have been modified to conditionally express BCR-ABL upon addition of doxycycline.25 In this setting, expression of BCR-ABL was associated with a 2.3–3.3-fold reduction in expression of miR-17, -18a and -19a, in agreement with our findings in primary ALL samples (Supplementary Figure 1).