H. pylori modifies methylation of global genomic DNA and the gastrin gene promoter in gastric mucosal cells and gastric cancer cells.

ABSTRACT

AIMS: The aim of this study was to evaluate the correlation between H. pylori infection and global DNA methylation, as well as the methylation levels of the gastrin promoters. MATERIALS AND METHODS: We constructed a eukaryotic expression vector, pcDNA3.1cagA, and transfected it into GES-1 gastric mucosal cells and SGC-7901 gastric cancer cells. Both cell lines were infected with the H. pylori/CagA+ strain NCTC11637. Then, we detected global DNA methylation by capture and detection antibodies, followed by colorimetric quantification. The methylation levels of the gastrin promoter were evaluated by base-specific cleavage and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. RESULTS: In H. pylori/CagA+-infected GES-1 and SGC-7901 cells, the methylation levels of genomic DNA decreased by 49.4% and 18.8%, and in GES-1 and SGC-7901 cells transfected with pcDNA3.1cagA, the methylation levels of genomic DNA decreased by 17.05% and 25.6%, respectively. Among 24 methylation sites detected in the gastrin promoter region, the methylation levels of 9 CpG sites were significantly decreased in H. pylori/CagA+-infected and pcDNA3.1 cagA-transfected cells in comparison to corresponding control cells. CONCLUSION: These results indicate that H. pylori/CagA+ decreases the methylation of the genome and the gastrin promoter at some CpG sites in gastric mucosal and gastric cancer cells.