Role of cagA-positive Helicobacter pylori on cell proliferation, apoptosis, and inflammation in biliary cells

Abstract

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 cagA(+) and cagA(-) 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 cagA(+) strain showed a significant stimulation in KKU-100 cell growth (109 ± 1.79%) and DNA synthesis (131 ± 3.39%) than did the H. pylori cagA(-) 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 cagA(+) strain showed a significant reduction in KKU-100 cell survival (49 ± 2.47%) and DNA synthesis (49 ± 1.14%) than did the H. pylori cagA(-) 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 cagA(+) 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.