Demonstration and characterization of mutations induced by Helicobacter pylori organisms in gastric epithelial cells
HELICOBACTER
Authors: Yao, Yuan; Tao, Hong; Park, Dong I. I.; Sepulveda, Jorge L.; Sepulveda, Antonia R.
Abstract
Background: Helicobacter pylori gastritis increases gastric cancer risk. Microsatellite instability-type mutations are secondary to deficient DNA mismatch repair. H. pylori gastritis is more frequent in patients with microsatellite instability-positive gastric cancers, and H. pylori organisms independently of inflammation can reduce DNA mismatch repair protein levels, raising the hypothesis that H. pylori organisms might lead to mutagenesis during infection. Materials and Methods: Mutations were detected using a green fluorescent protein reporter vector (pEGFP-CA13). Gastric cancer AGS cells transfected with pEGFP-CA13 were cocultured with H. pylori or Escherichia coli. The numbers of green fluorescent protein (GFP)-positive cells were determined, and GFP, hMSH2, and hMLH1 protein levels were measured by Western blot. The effect of H. pylori on CpG methylation status of hMLH1 was determined by methylation-specific polymerase chain reaction. Results: GFP levels and GFP-positive cell numbers in AGS cells cocultured with H. pylori significantly increased, as the levels of hMLH1 and hMSH2 dropped. H. pylori cocultures induced low-level CpG methylation of the hMLH1 promoter. Sequence analysis of cells cocultured with H. pylori showed an increased number of frameshift mutations and point mutations as compared to cells not cocultured with H. pylori (p = .03 and p = .001, respectively). Conclusions: This is the first report showing that H. pylori bacteria may lead to accumulation of genomic mutations, independently of underlying inflammation. This is associated with reduced DNA mismatch repair, and is at least in part associated with CpG methylation of the hMLH1 promoter. These data support the notion that H. pylori-induced mutations and epigenetic alterations in gastric epithelial cells during chronic gastritis may contribute to an increased risk of gastric cancer associated with H. pylori infection.
Association between interferon gamma 13-CA-repeats polymorphism and metastasis of nasopharyngeal carcinoma in a population of Northern China
INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY
Authors: Hao, Kaifei; Yan, Zhaohui; Shuang, Yu; Sun, Jinsong; Tao, Shudong; Fu, Wenyuan; Liu, Lei
Abstract
Interferon Gamma gamma (IFN-gamma) 13-CA-repeats polymorphism is associated with a variety of diseases; here we report its association with nasopharyngeal carcinoma (NPC) metastasis in a retrospective analysis of a cohort of 220 NPC patients in the northern China. The results showed that the distributions of CA13-/CA13-genotypes were significantly higher in the patients with lymph node metastasis (P< 0.05) and distant metastasis (P< 0.001); there was a significant difference between NPC patients with stage I+ II and those with stage III+ IV regarding CA13+/CA13-(P< 0.001) and CA13-/CA13-genotypes (P< 0.001); further analysis showed a more pronounced difference between NPC patients with stage I+ II+ III and those with stage IV for CA13-/CA13-genotype (P< 0.001), whereas no difference was found for CA13+/CA13-genotype (P= 0.790). Thus, we identify that IFN-gamma 13-CA-repeat polymorphism is significantly associated with the metastasis of NPC, which may provide insights into its prognosis and individualized treatment.