Epigenetic Alterations in a Gastric Leiomyoma

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.

Epigenetic Modifications Compromise Mitochondrial DNA Quality Control in the Development of Diabetic Retinopathy

“…However, the significance of such differential methylation of the Mlh1 promoter in retinal microvasculature in the development of diabetic retinopathy remains to be investigated. In support, irregular methylation of the Mlh1 promoter is considered as a useful molecular marker to screen or diagnose precancerous and early endometrial malignancies,45 and the methylation of a small proximal region in the Mlh1 promoter is shown to correlate with the lack of its expression in colorectal cell lines 23…”