The chemokine CXC ligand 12 (CXCL12), also known as stromal cell-derived factor 1 (SDF-1), is a chemokine protein that activates leukocytes and is usually induced by pro-inflammatory stimulants, such as LPS, TNF, or IL-1.CXCL12 is strongly chemotactic for lymphocytes. During embryogenesis, it induces hematopoietic cell migration from the fetal liver to the bone marrow and the formation of large blood vessels. In adults, CXCL12 has an important role in angiogenesis, where it recruits endothelial progenitor cells (EPCs) in the bone marrow through a CXCR4-dependent mechanism.CXCL12 also has a role in tumor metastasis, where cancer cells expressing the CXCR4 receptor are attracted to the target tissue. However, in breast cancer, elevated CXCL12 expression suggests a reduced risk of distal metastasis.