CXCL12 and cancer: CAFs regulate tumor cell phenotype, metastasis and angiogenesis via releasing growth factors, pro-inflammatory cytokines and chemokines including C–X–C motif chemokine ligand 12 (CXCL12) [16, 17], which is robustly expressed in most cancers, and plays important roles in cancer growth, migration, invasion and angiogenesis [18–20].