Role of cag A-Positive Helicobacter pylori on Cell Proliferation, Apoptosis, and Inflammation in Biliary Cells

Background and Aims The pathogenesis of Helicobacter pylori in the human hepatobiliary system has not been clearly elucidated. We compared the effects of H. pylori cag A + and cag A − mutant strains on cell proliferation, apoptosis, and inflammation in a cholangiocarcinoma (CCA) cell line (KKU-100). Methods MTT and BrdU were used to determine cell viability and DNA synthesis, respectively. The results were further investigated by RT-PCR and Western-blot analysis. The production of interleukin-8 (IL-8) was measured by ELISA assay. Results At low H. pylori inocula (cell-bacteria ratio of 1:1), the H. pylori cag A + strain showed a significant stimulation in KKU-100 cell growth (109 ± 1.79%) and DNA synthesis (131 ± 3.39%) than did the H. pylori cag A − strain (95 ± 3.06% and 120 ± 2.32%, respectively), through activation of the anti-apoptotic bcl - 2 gene, MAP kinase and NF- κB cascade. By contrast, at high H. pylori inocula (cell-bacteria ratio of 1:200), the H. pylori cag A + strain showed a significant reduction in KKU-100 cell survival (49 ± 2.47%) and DNA synthesis (49 ± 1.14%) than did the H. pylori cag A − strain (60 ± 1.30% and 75 ± 4.00%, respectively), by increased iNOS , p53 and bax , while decreased bcl-2 . Additionally, caspase-8 and -3 protein were activated. The H. pylori cagA + strain had significantly stronger effect on IL-8 production than did the cagA − strain. Conclusions These results suggest that the H. pylori cag A + strain may play an important role in the development of biliary cancer by disturbing cell proliferation, apoptosis, and promoting cell inflammation in the CCA cell line.