CXCL12 and cancer: The biological importance of CXCR4 is further underscored by the observation that disruption of the SDF-1/CXCR4 axis has consequence on essential physiological processes such as homing of hematopoietic stem cells to marrow [14] and migration of immune cells to inflammatory sites [15], as well as patho-physiological processes such as HIV uptake by host cells [16] and cancer progression.