Hong et al. reported that TGF-β1 derived from gastric cancer cells activated the P-Smad2/3 pathway in normal fibroblasts leading to their transformation into CAFs with a high expression of fibroblast activation protein (FAP), platelet-derived growth factor receptor beta (PDGFRB), and alpha-smooth muscle actin (α-SMA). Here, SMAD2 is linked to gastric cancer.