O6-Methylguanine-DNA methyltransferase protein levels in pediatric brain tumors.

Chloroethylnitrosoureas (CENUs) are commonly used in the treatment of pediatric and adult central nervous system (CNS) tumors. The antitumor activity of CENUs has been hypothesized to be due to an alkylation occurring at the O6-position of guanine in DNA. The DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) is responsible for the repair of these potentially cytotoxic lesions and may underlie tumor resistance to CENUs. The current study is the largest report of MGMT levels among newly diagnosed pediatric CNS tumors and the only study that has quantitated MGMT by both biochemical and Western immunoblot assays. Our results show a good correlation between the two methods (r = 0.66). Medulloblastoma/primitive neuroectodermal tumor and ependymoma had the highest level of MGMT, followed by high-grade glioma and low-grade glioma. These data may provide a guide to the use of CENUs in the treatment of pediatric CNS tumors.