FAP and cancer: Cancer-associated fibroblasts (CAFs), expressing α-smooth muscle actin (α-SMA), fibroblast activation protein (FAP), and fibroblast-specific protein 1, are the most abundant stromal cells in the TME.7, 8, 9 CAFs have been studied in multiple cancer types and found to have roles in creating extracellular matrix structure, activation of angiogenesis, and regulation of epithelial cell proliferation.10