Department of Neurology, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil.
Clinics (Sao Paulo). 2011;66(10):1747-55. doi: 10.1590/s1807-59322011001000013.
The MGMT gene is epigenetically silenced by promoter hypermethylation in gliomas, and this modification has emerged as a relevant predictor of therapeutic response.
Fifty-one cases of glioblastoma were analyzed for MGMT promoter methylation by methylation-specific PCR and pyrosequencing, gene expression by real time polymerase chain reaction, and protein expression by immunohistochemistry.
MGMT promoter methylation was found in 43.1% of glioblastoma by methylation-specific PCR and 38.8% by pyrosequencing. A low level of MGMT gene expression was correlated with positive MGMT promoter methylation (p = 0.001). However, no correlation was found between promoter methylation and MGMT protein expression (p = 0.297). The mean survival time of glioblastoma patients submitted to adjuvant therapy was significantly higher among patients with MGMT promoter methylation (log rank = 0.025 by methylation-specific PCR and 0.004 by pyrosequencing), and methylation was an independent predictive factor that was associated with improved prognosis by multivariate analysis.
MGMT promoter methylation status was a more reliable predictor of susceptibility to adjuvant therapy and prognosis of glioblastoma than were MGMT protein or gene expression levels. Methylation-specific polymerase chain reaction and pyrosequencing methods were both sensitive methods for determining MGMT promoter methylation status using DNA extracted from frozen tissue.
1）分析脑胶质瘤中 O6-甲基鸟嘌呤-DNA-甲基转移酶（MGMT）启动子的甲基化状态与其基因和蛋白表达水平的相关性，2）确定使用 MGMT 预测脑胶质瘤患者辅助治疗反应的最可靠方法。
MGMT 基因在胶质瘤中因启动子高甲基化而被表观遗传沉默，这种修饰已成为治疗反应的一个相关预测因子。
通过甲基化特异性 PCR 和焦磷酸测序分析 51 例脑胶质瘤的 MGMT 启动子甲基化情况，通过实时聚合酶链反应分析基因表达情况，通过免疫组织化学分析蛋白表达情况。
甲基化特异性 PCR 和焦磷酸测序检测到脑胶质瘤中 MGMT 启动子甲基化的比例分别为 43.1%和 38.8%。MGMT 基因低表达与 MGMT 启动子甲基化阳性相关（p=0.001）。然而，在启动子甲基化与 MGMT 蛋白表达之间未发现相关性（p=0.297）。接受辅助治疗的脑胶质瘤患者中，MGMT 启动子甲基化患者的平均生存时间明显更长（log rank：甲基化特异性 PCR 为 0.025，焦磷酸测序为 0.004），多变量分析表明，甲基化是与改善预后相关的独立预测因子。
与 MGMT 蛋白或基因表达水平相比，MGMT 启动子甲基化状态是预测脑胶质瘤对辅助治疗的敏感性和预后的更可靠指标。使用从冷冻组织提取的 DNA 时，甲基化特异性聚合酶链反应和焦磷酸测序方法都是检测 MGMT 启动子甲基化状态的敏感方法。
