Helicobacter pylori infection affects the expression of PCNA, p53, c-erbB-2 and Bcl-2 in the human gastric mucosa.

Objective: Helicobacter pylori infection has been related to gastric carcinogenesis. This association is based on epidemiological data, pathological changes observed in the gastric mucosa, and chemical products from bacteria that may induce damage of DNA. In the present study we examined gastric endoscopic biopsies from patients with chronic gastritis, with and without H. pylori infection, and surgical biopsies from gastric cancer patients to evaluate whether this bacteria may induce changes in the expression of molecular markers associated with carcinogenesis.

Patients And Methods: the study involved 57 biopsies from the antral region of the stomach of patients with chronic gastritis and gastric cancer that were analyzed by immunohistochemistry. Molecular markers examined were: PCNA (Proliferating Cell Nuclear Antigen), p53, c-erbB-2, Bcl-2, and p21 H-ras.

Results: PCNA content of epithelial cells was significantly higher in H. pylori infected biopsies. Treatment aimed to eradicate H. pylori decreased the level of PCNA-positive cells in the group of patients that became H. pylori-negative as well as in H. pylori-positive patients. Nuclear p53 expression (used here as a surrogate marker for p53 mutation/inactivation) and c-erbB-2 expression were observed only in the group of patients that remained with the bacteria after treatment. A higher bcl-2 expression in lymphoid cells was observed in H. pylori-positive biopsies, and treatment did not change the expression of this protein. No significant expression of p21 H-ras was observed in the studied biopsies.

Conclusion: this study suggests that H. pylori is involved in the induction of molecular changes that might predispose human gastric mucosa cells to pre-neoplastic and neoplastic events.