Helicobacter pylori stimulates DNA synthesis in a small intestinal cell line in vitro

• <b>Background:</b> <i>Helicobacter pylori</i>, which causes gastritis and peptic ulcer, seems to be an important factor in the pathogenesis of gastric cancer and MALT lymphoma. Thus our aim was to examine whether <i>H. pylori</i> influences DNA synthesis in epithelial cells in vitro. <b>Methods:</b> Sonicated and water extracts of <i>H. pylori</i> (cytotoxic strains NCTC 11637, 88-23 and A5, and a noncytotoxic isogenic mutant of A5, A5 vac A) were diluted to a final concentration of 1/1,000, 1/100, 1/50 and 1/10. Water extracts of <i>Escherichia coli</i> were used as reference. IEC-6 cells were incubated during 24 h with fragments of <i>H. pylori</i> or extracts of the concentrations described above. The cells were labeled with ³H-methylthymidine for 4 h and processed for autoradiography. DNA synthesis was evaluated by the labeling index (LI). <b>Results:</b> The LI% of controls was 15.6 ± 5.1%. All the water extracts and sonicated strains of <i>H. pylori</i> increased the LI% in a dose-dependent manner (p < 0.001). The highest concentrations of the sonicated strains tended to reduce the LI%, although these values were still higher than those of the control group. The water extracts of <i>E. coli</i> increased the LI% in a dose-dependent manner (p < 0.0001). <b>Conclusion:</b> <i>H. pylori</i> stimulates DNA synthesis in epithelial cells in vitro, but no association was found with the presence of cytotoxin production. Our results suggest that hitherto unknown components of <i>H. pylori</i> may contribute to the increase in cell proliferation observed in gastritis and to the development of MALT lymphoma and gastric cancer.

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