Background: To determine diagnostic importance of DNA methylation in patients with chronic atrophic gastritis and induction of ''Correa'' cascade for gastric cancer prevention. Material and methods: This present study included 80 patients with chronic atrophic gastritis associated with Helicobacter pylori. Diagnoses were confirmed by endoscopic, morphologic, serologic examinations. Age of patients varied from 17 to 78 years old. There were 52 (65%) males and 28 (35%) females. The control group consisted of 32 patients with morphological verified diagnosis of stage I-II gastric cancer. Examination with the purpose to determine hypermethylation of DNA was performed simultaneously in biopsy materials and blood plasma. Provoking factors of hypermethylation in 4 tumors' genes, APE, E-Cadherin, T1MP3, hMLHI were determined by quantitative methylation with use of Polymerase Chain Reaction. To evaluate the level of methylation we compared the analysis' results of biopsy and blood plasma tests. Blood serum samples and biopsy specimens were collected at diagnosis until the therapy is started. All patients with chronic atrophic gastritis infected with H. pylori underwent anti-H. pylori therapy according to the protocol. Chronic atrophic gastritis was found at morphologic examination in 40 (50%) patients according to ''Correa'' cascade. 36 (45%) patients had intestinal metaplasia, and 4 (5%) patients had dysplasia. Reaction was considered to be positive in cases, when the level of methylation in genes listed above was higher in blood serum than in biopsy materials. Results: High concentrations of methylated APE, T1MP3 and hMLIH in genes were found in blood serum of 8 (10%) patients. In the control group, all 32 patients with gastric cancer had high methylation level in blood serum. In the remaining 72 (90%) patients, no high concentration of DNA methylation was found. After the 2-nd course of anti-H. pylori therapy, patients underwent morphologic and endoscopic examinations according to the protocol. Eradication of H. pylori was determined in 86% patients who received therapy. Intestinal metaplasia decreased from 45% to 25% (20 patients). Mild dysplasia was found in 1.2% of cases. Repeated analysis of methylation level showed its decrease after anti-H. pylori therapy in 4 (50%) out of 8 patients. Conclusion: Genetic tests show that DNA methylation in patients with chronic atrophic gastritis has high diagnostic importance. Anti-H. pylori therapy at the different stages of ''Correa'' cascade has high level of induction in transforming into non invase gastric cancer.
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