CXCR4 and neoplasm: To counter anti-tumor immunity, PC cells release high-mobility group protein B1 (HMGB1), which combines with CXC-chemokine ligand 12 (CXCL12) produced by fibroblast activation protein (FAP)-positive CAFs to activate CXC-chemokine receptor 4 (CXCR4) on Teffs [89].