Chronic myeloid leukemia (CML) is caused by the acquisition of the fusion gene BCR-ABL1 in hemopoietic stem cells, which is transformed into leukemia stem cells (LSCs) and is characterized by Philadelphia (Ph) chromosome rearrangements and the constitutive expression of the fusion protein BCR–ABL11. This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.