PTK2 and gastric cancer: It has been determined that Lumican, an ECM proteoglycan belonging to the family of small leucine-rich repeat proteoglycans (SLRPs), is abundantly expressed by CAFs in gastric cancer (GC) stroma and that Lumican overexpression promotes GC tumorigenesis and metastasis by means of integrin β1/FAK signaling pathway activation [70].