FAP and neoplasm: Furthermore, the presence of FAP-positive elongated stromal cells (iCAFs) in both week 4 and 8 BxPC-3 tumors, but predominantly in week 8 and 10 and negligible in week 4 Panc-1-fl tumors (Supplementary Figure S6), indicates that FAP-expressing iCAFs mark an advanced tumor stage in the mouse models.