GDNF and neoplasm: Previous studies have demonstrated some tumor cell–intrinsic pathways alteration in nerve-cancer cross-talk, such as Hippo signaling activated by vagal nerve innervation in gastric cancer (58), MAPK and PI3K-AKT signaling enhanced by vagal nerve innervation in pancreatic ductal adenocarcinoma (59), JAK2-STAT1 signaling upregulated by nerve-derived GDNF in head and neck cancer (40) and so on.