Effect of O 6 -methylguanine-DNA methyltransferase methylation in medulloblastoma

Medulloblastoma is a highly malignant brain tumor that predominately affects children and requires multimodal treatment, including chemotherapy with alkylating agents. O -methylguanine-DNA methyltransferase (MGMT) is a DNA repair enzyme that plays an important role in tumor resistance to alkylating agents. Recent studies demonstrated that promoter methylation suppresses the expression of and is associated with favorable outcomes of malignant glioma patients. However, the methylation status and its prognostic impact on medulloblastoma have not been fully elucidated to date. The objective of the present study was to investigate the association between status and clinical outcomes of pediatric medulloblastoma patients. The records of 15 patients with medulloblastoma treated at our institution were reviewed, and the methylation status of 18 CpG sites in the promoter region was determined using bisulfite sequencing analysis. A larger number of methylated CpG sites was identified in 9 patients with complete remission (median, 5 sites; range, 2-9 sites) compared with that in 6 patients with relapse (median, 2 sites, range, 1-4 sites; P=0.041). These results suggest that a higher number of methylated CpG sites in the promoter region are associated with a favorable outcome of medulloblastoma.