Importance of changes in epithelial cell turnover during Helicobacter pylori infection in gastric carcinogenesis.

The role of Helicobacter pylori in gastric carcinogenesis is supported almost exclusively by epidemiological data and prospective histopathological studies. From biological and molecular points of view, there is no evidence that H pylori or its cytotoxic products have any mutagenic effects. Nevertheless, this infection is associated with profound changes in the pattern of epithelial cell turnover in gastric glands, though the importance of these changes in gastric carcinogenesis is still controversial. H pylori infection increases cell proliferation and alters the distribution of cycling cells within these glands, but these changes can be reversed by successful eradication of the infection. Apoptosis seems to be increased in gastric epithelial cells during H pylori infection, as shown by in vitro studies. There is some, though no conclusive, evidence that this finding also occurs in H pylori positive subjects. It seems that cagA status influences the effect of H pylori on epithelial apoptosis in infected patients. An association of in vitro H pylori induced apoptosis with changes in the expression of pro- and anti-apoptotic genes is reported in the literature, but further study is necessary to clarify the effect of H pylori infection on the molecular events of the apoptotic pathway.