Using a combined {Tec-p210BCR/ABL | SOS1/2-KO} mouse genetic model specifically generated for this report, we have now produced direct in vivo experimental evidence indicating that SOS1 genetic ablation causes the specific suppression of a variety of hematological alterations that constitute the typical hallmarks of p210-driven CML in mice and also significantly reduces the colony-forming ability of the population of HPCS from the bone marrow of p210BCR/ABL transgenic mice. Here, EVPL is linked to chronic myelogenous leukemia, BCR-ABL1 positive.