PPBP and neoplasm: CAFs contribute to ECM production by secreting CXCL16 and enhancing MMP expression, which increases tumor stiffness and alters ECM structure [45].The binding of PF4/CXCL4 and PPBP/CXCL7 to CXCL12, mediated by G protein-coupled receptors, promotes EMT and the expression of chemokines and cytokines [46].