The effect of Helicobacter pylori CagA on the HER-2 copy number and expression in gastric cancer

We investigated whether Helicobacter pylori (H. pylori) CagA contributes to the DNA copy change and mRNA transcript expression of the HER-2 gene and, consequently, affects HER-2 protein expression to evaluate the significance of CagA and HER-2 amplification in gastric cancer. We used the AGS and MKN1 gastric cancer and HFE-145 immortalized non-neoplastic gastric mucosa cell lines. We also confirmed the effects of CagA on HER-2 expression in human gastric cancer tissues and gastric mucosal tissues of H. pylori infected C57BL/6 mice. Ectopic CagA expression in AGS, MKN1 and HFE-145 cells showed a significant increase in HER-2 gene copy number and expression. The gastric mucosae of H. pylori infected C57BL/6 mice also showed increased HER-2 DNA copy number and protein expression. In addition, CagA expression was detected in 17 (56.7%) of 30 gastric cancer tissues, and eight (47%) of them showed HER-2 DNA amplification of more than two-fold. In immunohistochemistry, HER-2 overexpression was detected in 12 (40%) of 30 gastric cancers and a positive correlation was observed among DNA copy number, the mRNA transcript, and protein expression of the HER-2 gene in gastric cancer (P<. 0.05). These results suggest that H. pylori CagA may induce overexpression of the HER-2 protein by increasing HER-2 DNA and mRNA copy number.