CXCL12 and neoplasm: CAFs can secrete ECM components (such as type I collagen or fibrin) and several soluble factors, such as growth factors (EGF, HGF, TGF-β), metalloproteinases (MMP-1, -2, -9) or chemokines (CXCL12), to promote tumor growth and metastasis (74, 95).