Moreover, CXC ligand 12 (CXCL12, also called stromal cell-derived factor-1, SDF-1), which is produced by stromal cells and binds to C-X-C chemokine receptor type 4 (CXCR4) on the surface of tumor cells, has been reported to be essential for cancer pathogenesis. This evidence concerns the gene CXCR4 and neoplasm.