Why does Helicobacter pylori actually have Lewis antigens?

Fucosylation and gastrointestinal cancer

Fucose (6-deoxy-L-galactose) is a monosaccharide that is found on glycoproteins and glycolipids in verte-brates, invertebrates, plants, and bacteria. Fucosylation, which comprises the transfer of a fucose residue to oligosaccharides and proteins, is regulated by many kinds of molecules, including fucosyltransferases, GDP-fucose synthetic enzymes, and GDP-fucose transporter(s). Dramatic changes in the expression of fucosylated oligosaccharides have been observed in cancer and inflammation. Thus, monoclonal antibodies and lectins recognizing cancer-associated fucosylated oligosaccharides have been clinically used as tumor markers for the last few decades. Recent advanced glycomic approaches allow us to identify novel fucosylation-related tumor markers. Moreover, a growing body of evidence supports the functional significance of fucosylation at various pathophysiological steps of carcinogenesis and tumor progression. This review highlights the biological and medical significance of fucosylation in gastrointestinal cancer.

Role for alpha-L-fucosidase in the control of Helicobacter pylori-infected gastric cancer cells

Infecting about one-half of the global human population, Helicobacter pylori is well established as the primary cause of gastritis, duodenal ulcer, and gastric cancer. Currently there is no clear information regarding if and how host cells interact with H. pylori, and if such interactions are dependent on the type of gastric disease. Using fluorescently labeled fucose-containing glycoconjugates, we provide evidence observing both the uptake of L-fucose from gastric cancer cells to H. pylori and that human alpha-L-fucosidase 2 (FUCA2) is secreted only under coculture conditions (i.e., host cells infected with H. pylori). Upon depletion of FUCA2 by RNA interference and detection of translocated CagA (a virulence factor of H. pylori) in host cells, FUCA2 was found to be essential for H. pylori adhesion, in particular to the gastric cancer- and duodenal ulcer-specific strains. Additionally FUCA2 was shown to significantly enhance the expression of Lewis x antigen in H. pylori, which is critical for bacterial cell adhesion in the pathogenesis and defense strategy to escape host surveillance. These findings not only demonstrate an important connection between FUCA2 and the adhesion, growth, and pathogenicity of H. pylori, but also support the idea that FUCA2 is a potential target for clinical diagnosis and therapeutic intervention of H. pylori-related diseases.

The effect of Helicobacter pylori eradication treatment on the MUC 1 and Lewis antigens level in human gastric juice: a preliminary study

Helicobacter pylori is considered as a causative agent of gastritis, duodenal and gastric ulcers, and gastric cancer. During inflammation, association of the pathogen of gastric epithelial cells and mucins is considered important. It was postulated that Lewis b structures of secretory MUC 5AC mucin can be a receptor for the bacterium. Some authors also suggest that epithelial MUC 1 mucin may be implicated in the mechanism of infection. The main aim of our work was to support this last suggestion by evaluation of the possible changes in MUC 1 and Lewis a and b levels in gastric juice before and at the end of eradication treatment. The gastric juices of ten examined patients were chromatographed on a Sepharose 4 B column, electrotransferred on Immobilon P membranes, and assessed for MUC 1 and Lewis a and b structures using monoclonal antibodies. In 90% of examined patients, higher amounts of MUC 1 mucin were observed at the end of eradication treatment. Similar results for Lewis a and b structures were found. In the case of MUC 1 and Lewis b, the differences were statistically significant. Helicobacter pylori influences expression of the soluble form of MUC 1 mucin and Lewis a and b structures present in gastric juice.

MUC 1 mucin content in gastric juice of duodenal ulcer patients: effect of Helicobacter pylori eradication therapy

It has been suggested that Helicobacter pylori can interact via carbohydrate structures with gastric mucins. Particularly, the Lewis b structures of the secretory MUC 5AC mucin are considered to be putative receptors for bacterial adhesins. Also the epithelial MUC 1 mucin is implicated by some authors to have a major role in the mechanism of infection. The main objective of our study was to evaluate MUC 1 mucin levels in human gastric juice before and at the end of eradication therapy. Any possible changes could suggest the participation of MUC 1 in H. pylori infection. We assume that the amount of the soluble form of MUC 1 exfoliated to the juice correlates with MUC 1 expressed on epithelial cells. Gastric juice samples of 14 duodenal ulcer patients infected with H. pylori were assayed before and at the end of eradication. In all samples, DNA content was determined. Mucin fractions were isolated by gel exclusion chromatography. High molecular mass material containing MUC 1 was subjected to 4%-12% polyacrylamide gradient gels, electrotransfer to Immobilon P and immunodetection. In 12 infected patients (86%), the initial low level of MUC 1 mucin in gastric juice increased at the end of eradication. In comparison to the infected patients, neutral carbohydrate and DNA content in gastric juice diminished after treatment. Our results indicate that the bacterium affects the soluble form of MUC 1 mucin, thus suggesting a likely role of this mucin in the course of H. pylori infection.

Expression of Lewisb blood group antigen in Helicobacter pylori does not interfere with bacterial adhesion property

AIM: The finding that some Helicobacter pylori strains express Lewis b (Le^b) blood group antigen casts a doubt on the role of Le^b of human gastric epithelium being a receptor for H. pylori. The aim of this study was to determine if expression of Le^b in H. pylori interferes with bacterial adhesion property.

METHODS: Bacterial adhesion to immobilized Le^b on microtitre plate was performed in 63 H. pylori strains obtained from Singapore using in vitro adherence assay. Expression of Lewis blood group antigens was determined by ELISA assay.

RESULTS: Among 63 H. pylori strains, 28 expressed Le^b antigen. In vitro adhesion assay showed that 78.6% (22/28) of Le^b-positive and 74.3% (26/35) of Le^b-negative H. pylori isolates were positive for adhesion to immobilized Le^b coated on microtitre plate (P = 0.772). In addition, blocking of H. pylori Le^b by prior incubation with anti-Le^b monoclonal antibody did not alter the binding of the bacteria to solid-phase coated Le^b.

CONCLUSION: The present study suggests that expression of Le^b in H. pylori does not interfere with the bacterial adhesion property. This result supports the notion that Le^b present on human gastric epithelial cells is capable of being a receptor for H. pylori.