Promoter Hypermethylation of theEMP3Gene in a Series of 229 Human Gliomas

Abstract

The epithelial membrane protein 3 (EMP3) is a candidate tumor suppressor gene in the critical region 19q13.3 for several solid tumors, including tumors of the nervous systems. The aim of this study was to investigate theEMP3promoter hypermethylation status in a series of 229 astrocytic and oligodendroglial tumors and in 16 GBM cell lines. The analysis was performed by methylation-specific PCR and capillary electrophoresis. Furthermore, the EMP3 expression at protein level was evaluated by immunohistochemistry and Western blotting analysis. Associations ofEMP3hypermethylation with total 1p/19q codeletion,MGMTpromoter hypermethylation,IDH1/IDH2andTP53mutations, andEGFRamplification were studied, as well as its prognostic significance. TheEMP3promoter hypermethylation has been found in 39.5% of gliomas. It prevailed in low-grade tumors, especially in gliomas with an oligodendroglial component, and in sGBMs upon pGBMs. In oligodendroglial tumors, it was strongly associated with bothIDH1/IDH2mutations and total 1p/19q codeletion and inversely withEGFRgene amplification. No association was found withMGMThypermethylation andTP53mutations. In the whole series, theEMP3hypermethylation status correlated with 19q13.3 loss and lack of EMP3 expression at protein level. A favorable prognostic significance on overall survival of theEMP3promoter hypermethylation was found in patients with oligodendroglial tumors.