Chemokines and their receptors, principally the chemokine (C-X-C motif) ligand 12 (CXCL12) and its receptor CXCR4, have gained attention for their functional roles as being able to communicate between tumor cells and the tumor microenvironment including immune and vascular cells as also the stroma. The gene discussed is CXCL12; the disease is neoplasm.