FAP and cancer: The fibroblasts encompassed 4 major populations defined by key cancer-associated fibroblast (CAF) markers8–11, including fibroblast activation protein (FAP), alpha smooth muscle actin (αSMA, ACTA2), podoplanin (PDPN), and platelet-derived growth factor receptor beta (PDGFRβ) (Supplementary Fig. 1g, h).