[Detection of O6-methylguanine-DNA methyltransferase promoter methylation in chemotherapy for glioma]

Abstract

Background and objective: Epigenetic silencing of the DNA repair gene, O6-methylguanine-DNA methyltransferase (MGMT), is associated with the therapeutic response to methylating agents. This study was to assess the value of detecting the promoter methylation of MGMT gene in chemotherapy for glioma.

Methods: Methylation-specific PCR (MSP) was employed to detect MGMT promoter CpG island methylation in 39 samples of glioma taken from surgery. Western blot and immunohistochemistry were used to detect protein expression. MTT were employed to detect the sensitivity of two glioma cell lines to alkylating agents, ACNU and TMZ. The Kaplan-Meier curve was adopted to estimate the overall survival according to the methylation status of the MGMT promoter.

Results: Methylation of MGMT promoter CpG island was detectable in 46.2% of glioma tissues, but not in any normal tissues. The expression rate of MGMT protein was 61.5%. The status of MGMT methylation status was association with the protein level of MGMT (P<0.05). The MGMT gene was demethylated in glioma cell line SHG-44 following 5-Aza-CdR treatment; the expression of MGMT protein was restored and the resistance of SHG44 cells to alkylating agents was reversed. The overall survival was higher in patients with methylated MGMT promoter than in those with unmethylated MGMT promoter (P<0.05).

Conclusions: The status of MGMT promoter CpG island methylation is closely correlated to MGMT protein expression and sensitivity of cells to alkylating agents in glioma. Detection of the methylated sequences of MGMT may be used as a predictive factor for the treatment of glioma.