Expression of π glutathione S-transferase in intestinal metaplasia and its relationship with Helicobacter pylori infection

Objective To study the dynamic change of glutathione S- transferase π (GST-π) in normal gastric mucosa, gastric mucosa with intestinal metaplasia (IM) and gastric cancer and to investigate the relationship between human carcinogen detoxification system and the virulence of Helicobacter pylori (H.pylori) in the stage of IM. Methods Two hundred and nineteen biopsy specimens of gastric mucosa, including 30 cases with normal gastric mucosa, 171 cases with IM and 18 cases with gastric cancer, were examined. The expression of GST-π was detected by S-P immunohistochemical method. High-iron diamine /alcian blue pH2.5/periodic acid -Schiff (HID-ABpH 2.5-PAS) method was used to classify IM. H.pylori infection was confirmed or excluded by hematoxylin-eosin (HE) staining, of H.pylori-DNA PCR and ELISA. The 80 cases with H.pylori infection were treated by bismuthate+amoxicillin+metronidazole for three months and then biopsy specimens were taken again from the original sites. Results The GST-π expression rate was 69.6% in gastric mucosa with IM, significantly higher than that in gastric cancer (44.4%, P0.05) and that in normal gastric mucosa (0%, P0.01). The GST-π expression rate in IM II, IM III, and IM I decreased in sequence (83.3%, 71.1%, and 48.9%). The GST-π expression rate in IM without H.pylori infection was 79.0%, significantly higher than that in IM with HP infection (64.2%, P0.05). The positive rate of GST-π expression in H.pylori-eradicated group was 81.9%, significantly higher than that before H.pylori eradication (63.8%, P0.01). The GST-π expression rate decreased from normal gastric mucous to IM and to gastric cancer, and from IM I→II→III too. Conclusion IM III with low or no expression of GST-π is a high-risk condition of gastric cancer. The risk of gastric cancer increases when low or no expression of GST-π is combined with H.pylori infection. The carcinogen detoxification role of GST-π and the virulence of H.pylori might interact each other in the stage of intestinal metaplasia, the precancerous condition of gastric cancer.