They home into the tumor site, following secretion of soluble factors, such as IL-6, IL-1β, and/or transforming growth factor-β1 (TGF-β1) by tumor cells, as well as the stromal cell-derived factor1α (SDF-1α) by stromal cells [10] that promote paracrine signaling in tumor cells. This evidence concerns the gene CXCL12 and neoplasm.