Thus, inhibition of BCR-ABL1 in pre-B ALL cells 1) recapitulates early B cell development, 2) directly shows that IGK, KDE, and IGL genes are rearranged in sequential order, and 3) provides a model for Ig L chain gene regulation in the human..     ///    We studied whether inhibition of BCR-ABL1 kinase activity using STI571 can relieve this differentiation block.     ///     The BCR-ABL1 kinase expressed in acute lymphoblastic leukemia (ALL) drives malignant transformation of pre-B cells and prevents further development. 