Aberrant DNA methylation in thymic epithelial tumors.

Aberrant DNA methylation plays a critical role in the development and progression of many types of cancer. To investigate whether DNA methylation is abnormal in thymic epithelial tumors (TETs), we analyzed global methylation levels and the methylation status of 9 tumor suppressor gene (TSG) promoters in 65 TET samples. We found evidence of TSG promoter hypermethylation and decreased TSG expression in severe TETs. Furthermore, relative to early-stage TETs, global DNA methylation levels were reduced and DNA methyltransferase expression was increased in advanced-stage TETs. Our results suggest that aberrant DNA methylation is associated with TET development.