ORIGINAL ARTICLE

Effect of Helicobacter pylori on apoptosis and apoptosis related genes in gastric cancer cells

Y Yang¹, C S Deng¹, J Z Peng², B C-Y Wong³, S K Lam³ and H H-X Xia³

¹ Department of Gastroenterology, Zhongnan Hospital, Wuhan University, China
² Faculty of Medicine, Wuhan Science and Technology University, Wuhan, China
³ Division of Gastroenterology and Hepatology, Department of Medicine, The University of Hong Kong, Hong Kong, China

Correspondence to:
Correspondence to:
Dr H H-X Xia, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong, China;
hhxxia{at}hku.hk

Background/Aims: Helicobacter pylori induces the apoptosis of gastric epithelial cells in vivo and in vitro. However, the molecular mechanism has not been clarified. The aim of this study was to investigate the effect of H pylori on the apoptosis of gastric epithelial cells and the expression of apoptosis related genes in vitro.

Methods: Human gastric adenocarcinoma SGC-7901 cells were co-cultured with a cytotoxic H pylori strain, NCTC 11637, at various densities ranging from 3.2 x 10⁴ to 1.0 x 10⁸ colony forming units (CFU)/ml for 48 hours. Apoptosis in gastric cells was determined by transmission electron microscopy, Hoechst 33258 fluorochrome staining, and flow cytometry. The expression of apoptosis related proteins, Bcl-2, Bax, and c-Myc, was measured by an immunohistochemical method, and c-Myc mRNA expression was determined by the reverse transcription-polymerase chain reaction.

Results: Helicobacter pylori induces morphological changes typical of apoptosis. Both fluorochrome staining and flow cytometry showed that the apoptotic index began to increase when H pylori were at a density of > 1.6 x 10⁴ CFU/ml, and in a density dependent manner (p < 0.01; one way ANOVA). The expression of the Bax and c-Myc proteins and of c-Myc mRNA was increased, whereas Bcl-2 expression was decreased after co-culture for 48 hours.

Conclusions: Helicobacter pylori induced apoptosis in gastric epithelial cells is mediated by altered expression of the products of the Bcl-2, Bax, and c-Myc genes.

Keywords: Helicobacter pylori; gastric epithelial cells; apoptosis; Bcl-2; Bax; c-Myc

Abbreviations: CFU, colony forming units; OD, optical density; PAGE, polyacrylamide gel electrophoresis; RT-PCR, reverse transcription-polymerase chain reaction

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