For example, in gastric cancer (GC), several exosomal proteins have been reported to be associated with the progression of GC, including TGF-β1, human gastrokine 1, Cag A and apolipoprotein E. Yoon et al. found that the level of GKN1 in GC patients was significantly lower than that in healthy people. Here, GKN1 is linked to gastric cancer.