Interestingly, SOS1 ablation induced at a later age (8 months), when the onset of the disease has typically already started in these transgenic mice [33,34], did not produce any significant improvement in survival as compared to the control mice, suggesting a predominant functional contribution of SOS1 to the early stages of initiation, rather than to the progression of CML disease. This evidence concerns the gene SOS1 and chronic myelogenous leukemia, BCR-ABL1 positive.