Background: Helicobacter pylori (H. pylori) infection is considered as a carcinogen for gastric mucosa. The mechanism by which H. pylori are involved in gastric carcinogenesis is still unclear.

Objectives: The current study aimed to investigate the effects of H. pylori infection on immunohistochemical expression of p53 and Ki-67 genes in gastric specimens of patients with intestinal metaplasia (IM), dysplasia (DYS) and gastric cancer (GC).

Methods: In the study, 42 cases with IM, 38 with DYS and 42 with GC were selected from pathology archive of Ali-ebne-Abitaleb hospital, Zahedan, Iran; p53 and Ki-67 immunohistochemical study was done, accordingly. Kruskal-Wallis and Mann-Whitney U tests were used to compare the groups. Level of significance was set at P < 0.05.

Results: In IM specimens, expression of p53 and Ki-67 was significantly higher in the cases with H. pylori infection than those not infected with H. pylori. In DYS specimens, in the group with H. pylori infection, the expression of p53 was significantly higher while expression of Ki-67 was significantly lower than the group without H. pylori infection. In GC specimens, the expression of p53 was significantly higher in the group with H. pylori infection compared to the group without H. pylori infection. Expression of Ki-67 in the specimens with H. pylori infection was not significantly different from those without H. pylori infection.

Conclusions: The study results showed that p53 expression increased in IM, DYS and GC cases with H. pylori infection compared to those without H. pylori infection. The results also suggested that, Ki-67 expression was different in precancerous stages of gastric carcinogenesis, based on the infection with H. pylori.