Indeed, recent studies showed that the binding of stromal cell-derived-factor-1 (SDF-1), also known as chemokine ligand 12 (CXCL12), to the C-X-C chemokine receptor 4 (CXCR4) increases the proliferation rates and stromal vascular endothelial growth of several types of cancer [15–17], including breast tumors [18–23]. The gene discussed is CXCL12; the disease is breast neoplasm.