Indeed, increasing evidence indicates that the canonical JAK2/STAT5 pathway is critical for primary CML stem/progenitor cells, which rely on cytokine-activated JAK2/STAT5 signaling in addition to BCR-ABL signaling [34, 43, 44, 48, 49]. This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.