CXCR4 and acute myeloid leukemia: Elevated protein expressions of various cluster of differentiation (CD) marker genes such as interleukin 2 receptor subunit alpha (IL2RA/CD25) [3–7], C-X-C chemokine receptor type 4 (CXCR4/CD184) [8–10], CD34 [11, 12] and CD56 [13, 14] have been shown to predict poor clinical outcome in AML.