CAFs in GC have been found to secrete cytokines, such as CXCL12, interleukin 11 (IL-11), stromal-derived factor 1 (SDR1), and fibroblast growth factor 9 (FGF-9), to promote epithelial–mesenchymal transition (EMT), the key initiator of tumor invasion and metastasis (Ham et al., 2019). This evidence concerns the gene FGF9 and gastric cancer.