CXCR4 and neoplasm: That is, the two receptors of SDF1, CXCR4 and CXCR7 individually interact not only with SDF1 but also several other ligands including chemokines; moreover the ligands interact with other chemokine receptors affecting tumor cell growth and metastasis, as well as regulation of chemotaxis in the immune cells and hematopoietic progenitor cells [14–16].