CXCR4 and chronic myelogenous leukemia, BCR-ABL1 positive: The expression of C-X-C motif chemokine ligand 12 (or stromal derived factor 1α), the ligand for CXCR4, is reduced in the CML BMM due to increased secretion of granulocyte colony-stimulating factor adding to reduced retention of CML LSCs in the BMM79.