CXCL12 and neoplasm: Tumor-associated chemokines have at least five described roles in the biology of primary and metastatic disease: (1) control of leukocyte infiltration into the tumor (e.g., CCL2/MCP-1, CCL5/RANTES) [77,78]; (2) manipulation of tumor immune response (e.g., CCL4/MIP-1β); (3) regulation of angiogenesis (CXC chemokines); (4) actions such as autocrine or paracrine growth and survival factors (e.g., CXCL1, 2, 3, 8); and (5) direct the movement of tumor cell themselves (e.g., CXCL12, 19, 21) [79].