CXCL12 and cancer: A variety of cytokines secreted by cancer cells, and other stroma cells, is responsible for fibroblast recruitment and activation: epidermal growth factor (EGF), platelet-derived growth factor (PDGF), fibroblast growth factor 2 (FGF2), CXCL12 and TGF-β are key regulators of fibroblast recruitment and activation [151–158].