Helicobacter pylori increases proliferation of gastric epithelial cells

The direct and indirect effects of Helicobacter pylori on cell kinetics of gastric epithelial cell line AGS were investigated by flow cytometric analysis of Ki-67 positive cells and by MTT assay. Flow cytometric analysis of Ki-67 positivity permits detection of cells that are in S-phase, whereas the MTT assay is a colometric measure of the number of viable cells. In the absence of added stimulants, 23.06 (4.88)% mean (SD) of AGS cells were Ki-67 positive. When cells were preincubated in the presence of H pylori, there was a significant increase in Ki-67 positivity (66.20 (7.89)%, p<0.001). This increase was not seen in cells cultured in the presence of Campylobacter jejuni (24.63 (8.11)% or Escherichia coli (21.66 (9.78)%). Pre-incubation of AGS cells with supernatants from both H pylori and mitogen activated peripheral blood lymphocytes also increased the per cent of cells that were Ki-67 positive (72.93 (8.68) and 69.96 (12.35)%; p,0.001) respectively. Similar results were also found in MTT assay. These data show that both H pylori directly and the immune/inflammatory response to H pylori indirectly can influence the rate of epithelial cell proliferation, suggesting this bacterium may be an initiating step in gastric carcinogenesis and an important co-carcinogenic factor in H pylori positive subjects.