CXCL12 and cancer: Solute factors secreted by CAFs, such as IL-6, IL-33, TGF-β, CAF-derived cardiotrophin-like cytokine factor 1 (CLCF1), and stromal cell derived factor-1 (SDF-1), can produce cancer-promoting signals and participate in the signal transduction of cancer cells and other cells within the TME [161].