Global Genome Methylation Status in Gastritis Lesion in Comparison with Normal Adjacent Tissue and its Relationship with Clinicopathologic Findings
Objective: To determine the role of global genome methylation in gastritis lesion and its relation with clinicopathologic finding. Materials and Methods: The study was conducted on 44 gastritis and normal adjacent specimens using a technique composed of restriction enzyme digestion and pyrosequencing known as LUMA (LUminometric Methylation Assay). At first, DNA extracted from gastritis lesion and normal tissue was digested with HpaII (sensitive to methylation in recognition site) and MspI (insensitive). These enzymes leave an overhang after cutting which are then filled in a polymerase extension assay with stepwise addition of dNTPs using pyrosequencing. The comparison of the height of picks obtained form both enzymes provides the possibility to evaluate and compare global genome methylation level of normal and gastritis tissues. If the target site is fully methylated, the HpaII /MspI will approach toward zero .If not, this ratio will go around one. In the other conditions the ratio varies between 0-1. Results: According to our findings, gastritis tissue was significantly more hypomethylated (p=0.04) than the nornal tissue and Global genome methylation had no correlation with sex, age, microsatellite instability (MSI) and gastritis severity. Conclusion: Global DNA hypomethylation occurs in the gastritis lesion. Presumably the process of hypomethylation keeps falling in the next steps leading to gastric cancer.