Interestingly, CXCR4 ligand CXCL12/SDF-1α is prominent in bone marrow stromal cells with studies showing that CXCR4 cooperatively with other factors such as IL-11, CTGF and OPN facilitate osteolytic bone metastasis in breast cancer MDA-MB-231 cells [67, 68]. The gene discussed is CXCL12; the disease is breast cancer.