It is reported that gastric cancer‐derived exosomes can transfer various biological molecules to induce MMT of HMrSV5 cells, such as FasL, MMP2, nicotinamide N‐methyltransferase (NNMT), tripartite motif‐containing protein 3 (TRIM3), miR‐106 and miR‐21‐5p, which could regulate biological characteristics of HMrSV5 cells, thus facilitating metastasis of gastric cancer cells.44, 45, 46, 47, 48. Here, NNMT is linked to gastric cancer.