With regard to bone metastasis, CXC chemokine ligand 12 (CXCL12/SDF-1) and its receptor, CXCR4, participate in the development of skeletal metastasis by attracting cancer cells that express a high level of CXCR4 to bone marrow containing abundant CXCL1231, 32. The gene discussed is CXCR4; the disease is cancer.