The inhibiting event can be toxic [37], infectious [11, 13], mutation of a tumor-suppressor gene in gastric progenitor cells [38], or deletion of a gene that is important in gastric barrier function, such as Claudin 18 [39], or for mucosal protection, such as TFF1 [40] or Muc5 [41]. Here, MUC5AC is linked to neoplasm.