Microsatellite Instability in Chronic Gastritis Associated with Gastric Cancer

Aim: to assess the microsatellite instability status in gastric mucosa to determine the possibility of its use as a predictive marker of carcinogenesis. Material and methods. The study included two groups of gastric mucosa specimens: Group 1 — 155 mucosa fragments of the distant tumor growth zone obtained from stomachs resected for malignant neoplasms; Group 2 — 100 fragments with chronic gastritis taken from patients with dyspeptic complaints. Gastrobiopsy specimens were examined histologically, immunohistochemically using mouse monoclonal antibodies (Diagnostic BioSystems, USA) to the MMR system proteins: MLH-1 (clone G168-15, dilution 1:50), MSH2 (clone DBM15.82, dilution 1:100), MSH6 (clone 44, dilution 1:50), PMS2 (clone A16-4, ready to use). MSI was studied with multiplex PCR evaluation of DNA microsatellites (NR-21, NR-24, NR-27, BAT-25, BAT-26) from paraffin sections, their analysis with capillary electrophoresis. The obtained data were processed with the Statistica 10.0 (StatSoft Inc., USA), presented using descriptive, analytical statistics. Results . Immunohistochemical examination revealed 8 microsatellite-unstable cases in gastric mucosa specimens of Group 1 and 0 cases in Group 2 (statistically significant differences, p = 0.024). All studied gastric tissue samples were assessed as microsatellite-stable based on PCR results. Conclusion. Detection of MMR deficiency in gastric mucosa of the distant tumor growth zone and its absence in morphologically comparable specimens obtained from patients with chronic gastritis may be considered as confirmation of the hypothesis of disturbances in the MMR system as an early event in carcinogenesis. This, in turn, may indicate the potential for studying MMR status as a component of a decision support system for assessing the risk of developing microsatellite-associated gastric cancer.