SOS1 and chronic myelogenous leukemia, BCR-ABL1 positive: For this purpose, we generated an ad hoc mouse colony resulting from cross-mating a known transgenic p210BCR/ABL-driven CML mouse model [33,34] with our SOS1/2-KO system [19,26,35] (allowing us to generate WT, SOS1-KO, SOS2-KO, and SOS1/2-DKO mice).