Somatic mutation of mitochondrial DNA in Helicobacter pylori-associated chronic gastritis in patients with and without gastric cancer

Somatic mutations of the mitochondrial DNA (mtDNA) are associated with development of various types of human cancer. To elucidate the significance of somatic mutations of the mtDNA in gastric carcinogenesis, we examined mtDNA mutations in gastric cancers and in Helicobacter pylori-associated chronic gastritis (H. pylori-CG), which is associated with an increased risk for gastric cancer development. Specimens of gastric cancer and gastric mucosa were obtained from 73 gastric cancer patients with H. pylori-CG, 75 cancer-free H. pylori-CG patients and 30 H. pylori-negative healthy subjects. Mutations of a specific mononucleotide repeat (D310) of the mtDNA were examined by microsatellite assay. mtDNA mutations were detected in 9 of 56 (16%) gastric cancers, in 10 of 148 (7%) H. pylori-CG and none of the 30 H. pylori-negative healthy subjects. mtDNA mutations in H. pylori-CG were significantly more frequent in gastric cancer patients than in cancer-free patients (12% vs. 1%, p=0.008). In addition, mtDNA mutations in H. pylori-CG were significantly more frequent in patients with mtDNA mutated gastric cancer than in patients with mtDNA unmutated gastric cancer (66% vs. 4%, p<0.001). These data suggest that somatic mutations of the mtDNA may be involved in the early stages of gastric carcinogenesis.