MAFs activated by TGF-β1 increase the secretion of stromal cell-derived factor-1 (SDF-1, also known as C-X-C motif ligand 12, CXCL12), which binds to CXCR4 of tumor cells and promotes their TGF-β1 production in turn [41]. The gene discussed is CXCL12; the disease is neoplasm.