CXCR4 and leukemia: Acute myeloid leukemia (AML) is a malignant proliferative disease of myeloid hematopoietic stem cells and primitive cells with high heterogeneity.5, 6, 7, 8 The development and prognosis of AML are correlated with the factors such as the number of leukocytes in peripheral blood, cytogenetic abnormality, lactic dehydrogenase (LDH) level, body state, and others.3 Now, there have been increasing studies showing that the high expression of CXCR4 is a poor prognostic factor in some solid tumors and leukemia.3, 9, 10