Regulation of mucin and glycoconjugate expression: from normal epithelium to gastric tumors.

Gastric epithelium is protected by a mucus layer rich in MUC5AC and MUC6 mucins synthesised by the superficial epithelium and the glands, respectively. These cell populations also express specific fucosyltransferases that determine the glycosylation pattern of these gastric mucins. The maintenance of the structure and properties of the gastric mucus has been related to the degree of glycosylation and the oligomeric forms of the mucins. In gastric tumors, and in early preneoplastic lesions such as intestinal metaplasia, the glycosylation pattern detected in normal stomach is lost and, intestinal mucins, MUC2 and MUC4, can be ectopically detected in the gastric epithelium. These changes are biologically relevant because the binding of Helicobacter pylori to the gastric mucosa is mediated by blood group-related antigens. In vitro and animal models allowing the study of the gastric ecological niche and the requirements for its maintenance are essential for an understanding of the role of bacterial-mucosal interactions in pathological processes such as inflammation and cancer.