ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: On the other hand, consistent with our prior observations [17], our analysis of p210BCR/ABL transgenic mice expressing normal levels of SOS1 and SOS2 (WT for both SOS1 and SOS2) showed that the development of p210BCR/ABL-driven CML in those animals was also accompanied by a significant increase in the relative weights of the spleen and the liver (black bars), as well as by important histological disorganization of the spleen (but not the liver) of the same diseased animals (Figure 4A,B).