HELICOBACTER-PYLORI STIMULATES DNA-SYNTHESIS IN A SMALL-INTESTINAL CELL-LINE IN-VITRO

Background: Helicobacter pylori, which causes gastritis and peptic ulc er, seems to be an important factor in the pathogenesis of gastric can cer and MALT lymphoma. Thus our aim was to examine whether H. pylori i nfluences DNA synthesis in epithelial cells in vitro. Methods: Sonicat ed and water extracts of H. pylori (cytotoxic strains NCTC 11637, 88-2 3 and A5, and a noncytotoxic isogenic mutant of A5, A5 vac A) were dil uted to a final concentration of 1/1,000, 1/100, 1/50 and 1/10. Water extracts of Escherichia coli were used as reference. IEC-6 cells were incubated during 24 h with fragments of H. pylori or extracts of the c oncentrations described above. The cells were labeled with H-3-methylt hymidine for 4 h and processed for autoradiography. DNA synthesis was evaluated by the labeling index (LI). Results: The LI% of controls was 15.6 +/- 5.1%. All the water extracts and sonicated strains of H. pyl ori increased the LI% in a dose-dependent manner (p < 0.001). The high est concentrations of the sonicated strains tended to reduce the LI%, although these values were still higher than those of the control grou p. The water extracts of E. coli increased the LI% in a dose-dependent manner (p < 0.0001). Conclusion: H. pylori stimulates DNA synthesis i n epithelial cells in vitro, but no association was found with the pre sence of cytotoxin production. Our results suggest that hitherto unkno wn components of H. pylori may contribute to the increase in cell prol iferation observed in gastritis and to the development of MALT lymphom a and gastric cancer.