CXCR4 and acute myeloid leukemia: Elevated CXCR4 expression has been associated previously with higher CXCR4 signaling (Doijen et al., 2017), indicating that upregulation of CXCR4 on AML cells is responsible for the CXCR4 signaling, potentially related to an increase in CXCR4 homodimer formation in the absence of ligand stimulation (Babcock et al., 2003).