Aberrant CpG island hypermethylation profile is associated with atypical and anaplastic meningiomas

Hypermethylation of promoter CpG islands is a common epigenetic event in a variety of human cancers. The aim of this study was to investigate whether promoter hypermethylation of cancer-related genes is involved in the development and progression of meningiomas. The methylation status at the promoter region of 10 cancer-related genes was examined by methylation-specific polymerase chain reaction in a cohort of 48 meningiomas including 16 benign, 19 atypical, and 13 anaplastic variants. The relationship of promoter hypermethylation and transcriptional silencing was determined by treatment of cells with demethylating agent 5-aza-2′-deoxycytidine followed by reverse transcription-polymerase chain reaction. Our results showed that 50% (24/48) of meningiomas exhibited promoter hypermethylation in at least one of the genes but not in normal leptomeninges, indicating that aberrant hypermethylation is tumor-specific. Promoter hypermethylation was detected in glutathione S-transferases P1 at 27%, thrombospondin-1 at 15%, retinoblastoma 1 at 10%, cyclin-dependent kinase inhibitor 2A at 10%, O6-methylguanine-DNA methyltransferase at 6%, and death-associated protein kinase 1, von Hippel-Lindau, p14ARF, and cyclin-dependent kinase inhibitor 2B, each at 4%. No promoter hypermethylation was detected in the tissue inhibitor of metalloproteinase 3 gene. Treatment of IOMM-Lee meningioma cell line with 5-aza-2′-deoxycytidine restored expression of O6-methylguanine-DNA methyltransferase and death-associated protein kinase 1, providing evidence that promoter hypermethylation contributes to transcriptional silencing. The frequencies of methylation of any single gene in benign, atypical, and malignant meningiomas were 6% (1/16), 74% (14/19), and 69% (9/13), respectively. Of 48 tumors, 13 (27%) showed that concurrent hypermethylation of two or more genes studied were of atypical or anaplastic type. Statistical analysis revealed that the incidence of promoter hypermethylation of any single gene, of multiple genes, or of glutathione S-transferase P1 was significantly associated with atypical and anaplastic meningiomas (P < .0001, P = .004, and P = .004, respectively). In conclusion, this study demonstrates that aberrant hypermethylation profile is associated with atypical and anaplastic meningiomas, suggesting that epigenetic change may be involved in malignant progression of meningiomas.