For the latter, we used primary BCR-ABL-positive precursor-B cell ALL blasts, which had been passaged through NOD/LtSz-scid IL-2Rγ null (NSG) mice (primograft, designated L4951 cells).23 Cells were incubated with either drug or vehicle control and the number of viable cells was determined over time. This evidence concerns the gene ABL1 and acute lymphoblastic leukemia.