NNMT and gastric cardia adenocarcinoma: Results from gastric cardia adenocarcinoma indicate that nicotinamide N-methyltransferase (NNMT) is enriched in AQP5 expressing stem cells and that their stemness is maintained by NNMT-mediated nicotinamide metabolism, which causes reduction of H3K27 trimethylation and activation of WNT signaling [61].