Abstract
Leiomyomas constitute 2.5% of all resected neoplasms of the stomach. They are usually asymptomatic, but may present mucosal ulceration. Aberrant DNA methylation is a well-defined epigenetic change in human neoplasms; however, gene-acquired methylation may not necessarily be related with a malignant phenotype. In this report we analyzed in a gastric leiomyoma, the methylation status of 84 CpGI in tumor suppressor and DNA repair genes. We analyzed the tumor center (TC) and tumor periphery (TP) separately. We found aberrant methylation in 2/84 CpGI in the TC portion, that is, MLH1 and MSH3, and 5/84 CpGI in the TP, that is, MLH1, MSH3, APC, MSH6, and MGMT. The gene with the highest methylation percentage in the TC and TP was MLH1. Given that MLH1 methylation has been associated with microsatellite instability, we analyzed the status of the microsatellite Bat-26. We found that neither the TC nor the TP presented instability. The methylation of MLH1, MGMT, and APC has been described in GISTs, but to the best of our knowledge this is the first time that the methylation of these genes has been associated with gastric leiomyoma. Further research should be conducted to identify reliable molecular markers that could differentiate between GISTs and gastric leiomyomas.
Highlights
Gastric leiomyomas account for 2.5% of gastric neoplasms
Gene silencing by CpG islands (CpGI) hypermethylation in gene promoters can modulate pathways that control the basic function of the cell by acting directly on tumor suppressor genes and caretaker genes and indirectly on oncogenes through their regulators [5]
Results from recent investigations have shown that DNA methylation profiles contain tumor type-specific signatures which, in the future, could serve as biomarkers for clinical outcome [15]
Summary
Gastric leiomyomas account for 2.5% of gastric neoplasms. most of them are asymptomatic, patients may present upper gastrointestinal hemorrhage [1, 2]. Gastric leiomyomas appear as a large submucosal lesion, and generally endoscopic biopsies are not deep enough to be of any diagnostic value [3]. Most of these tumors are composed of spindle cells and display smooth muscle differentiation. The epigenome of tumors is characterized by global DNA hypomethylation and by gene-specific hypermethylation. The objective of this study was to analyze by methyl specific-multiplex ligation probe amplification (MS-MLPA) the methylation status of tumor suppressor and DNA repair genes in a gastric leiomyoma
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