By analyzing different subpopulation of primitive CML cells it has been shown that an unusual autocrine IL-3-granulocyte colony-stimulating factor mechanism can provide a strong rational for the unusual performance of BCR-ABL expressing stem and progenitor cells (Chang et al., 1989; Holyoake et al., 2002). Here, ABL1 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.