MGMT activity, promoter methylation and immunohistochemistry of pretreatment and recurrent malignant gliomas: a comparative study on astrocytoma and glioblastoma
MGMT activity, promoter methylation and immunohistochemistry of pretreatment and recurrent malignant gliomas: a comparative study on astrocytoma and glioblastoma
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DOI：
10.1002/ijc.25229
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发表时间：
2010-11-01
影响因子：
6.4
通讯作者：
Kaina, Bernd
中科院分区：
文献类型：
--
作者：
Christmann, Markus;Nagel, Georg;Kaina, Bernd
DNA修复蛋白O-6-甲基鸟嘌呤-DNA甲基转移酶（MGMT）是肿瘤细胞耐药性的关键因素。启动子甲基化、MGMT活性和免疫组织化学用于确定MGMT状态。然而，目前尚不清楚MGMT启动子甲基化是否与MGMT活性相关，以及治疗前肿瘤的MGMT启动子甲基化是否预测复发的MGMT状态。为了解决这些问题，我们测定了治疗前和复发性胶质母细胞瘤（GB，WHO IV级）和星形细胞瘤（WHO III级）中MGMT活性启动子甲基化和免疫反应性。我们发现，启动子甲基化的GB显示0-62 fmol/mg MGMT的范围，而非甲基化的肿瘤显示0-423 fmol/mg蛋白。对于星形细胞瘤，启动子甲基化的样品显示0-28 fmol/mg，而非甲基化的样品显示23-107 fmol/mg。启动子区甲基化程度与MGMT活性无相关性。给定30 fmol/mg蛋白质的阈值水平，我们发现在82.4%的肿瘤中启动子甲基化与无/低MGMT活性之间存在相关性。仅当排除肿瘤时观察到这种高相关性水平，显示半甲基化启动子（20%）。因此，半甲基化肿瘤的分类仍然存在疑问。此外，我们发现，39.1%的预处理GB和5.3%的recurrent是启动子甲基化，这是符合观察到的MGMT活性增加recurrent。尽管发现了个别例外，但数据显示GB和星形细胞瘤中启动子甲基化与MGMT活性缺乏/低之间存在总体相关性。我们还表明，启动子甲基化测定是优于免疫组化在确定MGMT状态定义的一个给定的MGMT活性水平上级。
The DNA repair protein O-6-methylguanine-DNA methyltransferase (MGMT) is a key player in tumor cell resistance. Promoter methylation, MGMT activity and immunohistochemistry are used for determining the MGMT status. However, it is unclear whether MGMT promoter methylation correlates with MGMT activity and whether MGMT promoter methylation of the pretreatment tumor predicts the MGMT status of recurrences. To address these questions, we determined MGMT activity promoter methylation and immunoreactivity in pretreatment and recurrent glioblastomas (GB, WHO Grade IV), and in astrocytomas (WHO Grade III). We show that GB that were promoter methylated display a range of 0-62 fmol/mg MGMT and tumors that were nonmethylated 0-423 fmol/mg protein. For astrocytomas, promoter-methylated samples displayed 0-28 fmol/mg and, nonmethylated samples, 23-107 fmol/mg. No correlation was found between the intensity of promoter methylation and MGMT activity. Given a threshold level of 30 fmol/mg of protein, we found a correlation between promoter methylation and no/low MGMT activity in 82.4% of the tumors. This high correlation level was only observed when tumors were excluded showing a hemimethylated promoter (20%). Therefore, classification of hemimethylated tumors remains questionable. Further, we show that 39.1% of pretreatment GB and 5.3% of recurrences were promoter methylated, which is in line with the observed increase of MGMT activity in recurrences. Although individual exceptions were found, the data show an overall correlation between promoter methylation and lack/low MGMT activity in GB and astrocytomas. We also show that promoter methylation assay is superior over immunohistochemistry in determining the MGMT status defined by a given MGMT activity level.