CXCL12 and neoplasm: The latest study confirmed that CXCR4 interacts with its ligand SDF-1 and is associated with the metastasis of some tumors, and tumor cells with high expression of CXCR4 may, under the chemotactic movement and traction of SDF-1, transfer to some organs that act as a source of ligand production against a concentration gradient, thus forming organ specific metastasis.