CXCR4 and acute myeloid leukemia: SDF1 is an extracellular chemokine which is abundantly produced by the bone marrow microenvironment binds to and activates its receptor CXCR4 which is highly expressed on many non-malignant and malignant cells including breast cancer cell, normal haematopoietic CD34+ cells as well as AML blasts [23, 24].