CXCL12 and hepatocellular carcinoma: CAFs are characterized by the secretion of high amounts of collagen in the HCC stroma or ECM, and the upregulation of the chemokine CXCL12, also known as stromal-cell-derived factor 1 (SDF-1), which stimulates tumor growth and neo-angiogenesis by the recruitment of endothelial progenitor cells [99].