MGMT Promoter Methylation In Glioblastoma Research Articles

Quantitative analysis of MGMT promoter methylation in glioblastoma suggests nonlinear prognostic effect.

Epigenetic inhibition of the O6-methylguanine-DNA-methyltransferase (MGMT) gene has emerged as a clinically relevant prognostic marker in glioblastoma (GBM). Methylation of the MGMT promoter has been shown to increase chemotherapy efficacy. While traditionally reported as a binary marker, recent methodological advancements have led to quantitative methods of measuring promoter methylation, providing clearer insight into its functional relationship with survival. A CLIA assay and bisulfite sequencing was utilized to develop a quantitative, 17-point, MGMT promoter methylation index. GBMs of 240 newly diagnosed patients were sequenced and risk for mortality was assessed. Nonlinearities were captured by fitting splines to Cox proportional hazard models and plotting smoothed residuals. Covariates included age, Karnofsky performance status, IDH1 mutation, and extent of resection. Median follow-up time and progression-free survival were 16 and 9 months, respectively. A total of 176 subjects experienced death. A one-unit increase in promoter CpG methylation resulted in a 4% reduction in hazard (95% CI 0.93-0.99, P < .005). GBM patients with low levels of promoter methylation (1-6 CpG sites) fared markedly worse (HR = 1.62, 95% CI 1.03-2.54, P < .036) than individuals who were unmethylated. Subjects with medium levels of promoter methylation (7-12 sites) had the greatest reduction in hazard (HR = 0.48, 95% CI 0.29-0.80, P < .004), followed by individuals in the highest promoter methylation tertile (HR = 0.62, 95% CI 0.40-0.97, P < .035). Our findings suggest that the relationship between the extent of MGMT promoter methylation and survival in GBM may be nonlinear. These findings challenge the current understanding of MGMT and underlines the clinical importance of determining its prognostic utility. Potential limitations include censoring, sample size, and extraneous mutations.

Risk of Venous Thromboembolism in Grade II-IV Gliomas as a Function of Molecular Subtype.

To determine the incidence of venous thromboembolism (VTE) in lower-grade gliomas (LGGs, WHO grades II-III) and to stratify the risk of VTE by molecular subtype in gliomas grade II-IV, we performed a retrospective review of a large cohort of patients with glioma. We performed a retrospective analysis of a cohort of 635 adult patients with glioma with molecular testing seen at the University of Virginia with a diagnosis of diffuse glioma established from January 2005 to August 2017. Estimates of cumulative incidence of VTE were calculated with death as competing risk; significance was determined using the Fine and Gray model. Of 256 patients with LGG, 81 were isocitrate dehydrogenase (IDH) wild-type; 113 IDH mutant, 1p/19q codeleted; and 62 IDH mutant, 1p/19q intact. With a median follow-up of 17.9 months, the overall cumulative incidence of VTE was 8.2% for grade II (147 patients), 9.2% for grade III (109 patients), and 30.5% for grade IV (334 patients). In grade II-IV patients, absence of an IDH mutation was associated with a threefold increase in VTE risk when compared to IDH-mutant patients (hazard ratio 3.06, 95% confidence interval 2.03-4.64). In patients with glioblastoma, there was no difference in VTE incidence according to O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status. Patients with LGG have a higher VTE risk compared to the general population, which is decreased, but not eliminated, in the presence of an IDH mutation. MGMT promoter methylation in glioblastoma does not affect the incidence of VTE.

Correlation of the quantitative level of MGMT promoter methylation and overall survival in primary diagnosed glioblastomas using the quantitative MethyQESD method

AimsO(6)-methylguanine-DNA-methyltransferase (MGMT) promoter methylation is a high predictive factor for therapy results of temozolomide in patients with glioma. The objective of this work was to analyse the impact of MGMT...

MGMT gene promoter methylation and its correlation with clinicopathological parameters in glioblastomas.

MGMT (O6-methyl guanine DNA methyl transferase) promoter hypermethylation is a prognostic and predictive biomarker for glioblastomas (GBM). To evaluate the frequency of MGMT methylation status in a single institute series of 134 GBMs and correlate it with clinical (age, sex, location, survival) and other molecular parameters [such as p53 expression, alpha thalassemia/mental retardation syndrome X-linked (ATRX) expression, isocitrate dehydrogenase (IDH) 1R132H mutation, and epidermal growth factor receptor (EGFR) gene amplification]. One hundred and thirty-four GBMs were evaluated by methylation-specific polymerase chain reaction (MSP) for MGMT promoter methylation status. The results were correlated with the above mentioned clinicopathological parameters. MGMT gene promoter methylation was identified in 49.2% (66/134) GBMs, and was significantly associated with IDH1R132H mutation (14/66; 21%; P - value, 0.01) and ATRX loss (15/66; 23%; P - value, 0.01). Confluent necrosis was found to be significantly associated with MGMT unmethylation status (P - value: 0.002). Multivariable logistic regression analysis showed confluent necrosis as a single independent predictor (odds ratio [OR], 2.5; confidence interval [CI], 1.0-5.8; P - value, 0.04) of MGMT unmethylation status among all the parameters studied. The frequency of MGMT promoter methylation in GBMs was 49.2%, which was significantly associated with IDHR132H mutation and ATRX loss. In addition, the presence of confluent necrosis was significantly associated with MGMT unmethylation and was found to be an independent predictor of the same.

MGMT promoter methylation in glioblastoma.

MGMT promoter methylation in glioblastoma.

Radiomics signature: A potential biomarker for the prediction of MGMT promoter methylation in glioblastoma.

In glioblastoma (GBM), promoter methylation of the DNA repair gene O-methylguanine-DNA methyltransferase (MGMT) is associated with beneficial chemotherapy. To analyze radiomics features for utilizing the full potential of medical imaging as biomarkers of MGMT promoter methylation. Retrospective. In all, 98 GBM patients with known MGMT (48 methylated and 50 unmethylated tumors). 3.0T magnetic resonance (MR) images, containing T1 -weighted image (T1 WI), T2 -weighted image (T2 WI), and enhanced T1 WI. A region of interest (ROI) of the tumor was delineated. A total of 1665 radiomics features were extracted and quantized, and were reduced using least absolute shrinkage and selection operator (LASSO) regularization. After the support vector machine construction, accuracy, sensitivity, and specificity were computed for different sequences. An independent validation cohort containing 20 GBM patients was utilized to further evaluate the radiomics model performance. Radiomics features of T1 WI reached an accuracy of 67.54%. Enhanced T1 WI features reached an accuracy of 82.01%, while T2 WI reached an accuracy of 69.25%. The best classification system for predicting MGMT promoter methylation status originated from the combination of 36 T1 WI, T2 WI, and enhanced T1 WI images features, with an accuracy of 86.59%. Further validation on the independent cohort of 20 patients produced similar results, with an accuracy of 80%. Our results provide further evidence that radiomics MR features could predict MGMT methylation status in preoperative GBM. Multiple imaging modalities together can yield putative noninvasive biomarkers for the identification of MGMT. 4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1380-1387.

Real-Time Methylation-Specific Polymerase Chain Reaction for MGMT Promoter Methylation Clinical Testing in Glioblastoma: An Alternative Detection Method for a Heterogeneous Process.

To develop and evaluate a real-time methylation-specific polymerase chain reaction (RT-MSP) MGMT assay, with a particular focus on small biopsies and indeterminate testing results. We assessed formalin-fixed paraffin-embedded glioblastoma or gliosarcoma specimens (n = 641). A test-validation group (n = 51) with previously obtained reference laboratory (RL) results was used to determine performance characteristics of the RT-MSP assay. An indeterminate (equivocal) category was established for cases that could not be clearly classified as positive or negative. Overall agreement of RT-MSP and RL results was 91% (41/45 nonindeterminate cases). Discordant cases were tested by pyrosequencing, and results were most concordant with RT-MSP. Among cases with limited amounts of tissue (n = 7), six yielded valid results by RT-MSP (all negative); the single invalid result consisted of a stereotactic biopsy specimen obtained 14 years prior. A subset of indeterminate cases obtained during clinical testing (n = 18/575 [3%]) was also evaluated by pyrosequencing and showed a heterogeneous pattern of methylation across the eight interrogated CpG sites. The RT-MSP assay that we developed in-house is a robust clinical detection method for the heterogeneous process of MGMT promoter methylation in glioblastoma.

The prognostic value of MGMT promoter methylation in glioblastoma: A meta‐analysis of clinical trials

The DNA repair protein O6-Methylguanine-DNA methyltransferase (MGMT) is suggested to be associated with resistance to alkylating agents such as Temozolomide which is being used in treatment of patients with glioblastoma (GBM). Therefore, we evaluated the associations between MGMT promoter methylation and prognosis of patients with glioblastoma (GBM). Data were extracted from publications in Embase, PubMed, and the Cochrane Library. Data on overall survival (OS), progression-free survival (PFS), and MGMT methylation status were obtained and 4,097 subjects were enrolled. Data from 34 studies showed that MGMT methylated patients had better OS, compared to GBM unmethylated patients (pooled HRs, 0.494; 95%CI 0.412-0.591; p = 0.001). Meta-analysis of 10 eligible studies reporting on PFS, demonstrated that MGMT promoter methylation was not significantly associated with better PFS (pooled HRs, 0.653; 95%CI 0.414-1.030; p = 0.067). GBM patients with MGMT methylation were associated with longer overall survival, although this effect was not detected for PFS. Moreover, we performed further analysis in patients underwent a comprehensive imaging evaluation. This data showed a significant association with better OS and PFS, although further studies are warranted to assess the value of emerging marker in prospective setting in patients with glioblastoma as a risk stratification biomarker in clinical management of the patients.

Learning MRI-based classification models for MGMT methylation status prediction in glioblastoma

Background and ObjectiveThe O6-methylguanine-DNA-methyltransferase (MGMT) promoter methylation has been shown to be associated with improved outcomes in patients with glioblastoma (GBM) and may be a predictive marker of sensitivity to chemotherapy. However, determination of the MGMT promoter methylation status requires tissue obtained via surgical resection or biopsy. The aim of this study was to assess the ability of quantitative and qualitative imaging variables in predicting MGMT methylation status noninvasively. MethodsA retrospective analysis of MR images from GBM patients was conducted. Multivariate prediction models were obtained by machine-learning methods and tested on data from The Cancer Genome Atlas (TCGA) database. ResultsThe status of MGMT promoter methylation was predicted with an accuracy of up to 73.6%. Experimental analysis showed that the edema/necrosis volume ratio, tumor/necrosis volume ratio, edema volume, and tumor location and enhancement characteristics were the most significant variables in respect to the status of MGMT promoter methylation in GBM. ConclusionsThe obtained results provide further evidence of an association between standard preoperative MRI variables and MGMT methylation status in GBM.

118PD Prognostic significance of MGMT promoter methylation in glioblastoma, a retrospective study in the North-East of Iran

118PD Prognostic significance of MGMT promoter methylation in glioblastoma, a retrospective study in the North-East of Iran

IDH mutation and MGMT promoter methylation in glioblastoma: results of a prospective registry.

The relative contribution of isocitrate dehydrogenase mutations (mIDH) and O6-methylguanine-DNA methyltransferase promoter methylation (methMGMT) as biomarkers in glioblastoma remain poorly understood. We investigated the association between methMGMT and mIDH with progression free survival and overall survival in a prospectively collected molecular registry of 274 glioblastoma patients. For glioblastoma patients who underwent Temozolomide and Radiation Therapy, OS and PFS was most favorable for those with tumors harboring both mIDH and methMGMT (median OS: 35.8 mo, median PFS: 27.5 mo); patients afflicted glioblastomas with either mIDH or methMGMT exhibited intermediate OS and PFS (mOS: 36 and 17.1 mo; mPFS: 12.2 mo and 9.9 mo, respectively); poorest OS and PFS was observed in wild type IDH1 (wtIDH1) glioblastomas that were MGMT promoter unmethylated (mOS: 15 mo, mPFS: 9.7 mo). For patients with wtIDH glioblastomas, TMZ+RT was associated with improved OS and PFS relative to patients treated with RT (OS: 15.4 mo v 9.6 mo, p < 0.001; PFS: 9.9 mo v 6.5 mo, p < 0.001). While TMZ+RT and RT treated mIDH patients exhibited improved overall survival relative to those with wtIDH, there were no differences between the TMZ+RT or RT group. These results suggest that mIDH1 conferred resistance to TMZ. Supporting this hypothesis, exogenous expression of mIDH1 in independent astrocytoma/glioblastoma lines resulted in a 3-10 fold increase in TMZ resistance after long-term passage. Our study demonstrates IDH mutation and MGMT promoter methylation status independently associate with favorable outcome in TMZ+RT treated glioblastoma patients. However, these biomarkers differentially impact clinical TMZ response.

Assessing correlation between LINE-1 methylation and MGMT promoter methylation in glioblastomas.

e13048 Background: Genome-wide hypomethylation is one of the cancer characteristics. In malignant gliomas, hypermethylation of MGMT promoter serves as an important prognostic factor and a predictiv...

Prognostic Impact of MGMT Promoter Methylation in Glioblastoma - A Systematic Review

MGMT promoter methylation is currently considered the main prognostic biomarker in glioblastoma, yet some concerns remain about its actual impact on outcome. The aim of the present study was to analyze literature data on this topic. Therefore, a systematic review and analysis of recently published glioblastoma cohorts examining the relationship between MGMT methylation and prognosis was performed. We found that only 19/28 studies (68%) confirmed the prognostic value of MGMT methylation and/or its role in predicting response to temozolomide. In these studies, however, the population showed significantly lower rates of unfavorable prognosticators as compared with studies where MGMT methylation was not prognostic/predictive. Moreover, studies demonstrating a better prognosis for MGMT methylated cases had significantly lower rates of deaths at 3 and 6 months. Multivariate analysis showed that the 3-month and 6-month deaths are significantly associated with the prognostic/predictive value of MGMT methylation, and that the percent of MGMT methylated tumors and of patients treated with alkylating drugs trend towards statistical significance if modeled with the 6-month but not with the 3-month mortality rate. These results suggest that the paucity of short-term survivors may represent a bias in studies focusing on MGMT methylation and prognosis, and that a temporal threshold may be necessary in order to demonstrate the clinical benefit of MGMT promoter methylation.

Correlation between quantified promoter methylation and enzymatic activity of O 6-methylguanine-DNA methyltransferase in glioblastomas

The DNA repair protein O (6)-methylguanine-DNA methyltransferase (MGMT, AGT) is a determinant of the resistance of tumor cells to alkylating anticancer agents that target the O(6) position of guanine. MGMT promoter methylation in tumors is regarded as the most common predictor of the responsiveness of glioblastoma to alkylating agents. However, MGMT promoter methylation status has been investigated mainly by methylation-specific PCR, which is a qualitative and subjective assay. In addition, the actual enzymatic activities associated with the methylation status of MGMT have not been explored. In the present study, MGMT promoter methylation in glioblastomas was quantified by bisulfite pyrosequencing, and its correlation with enzymatic activity was determined using a novel quantitative assay for studying the functional activity of MGMT. MGMT enzymatic activity was assessed using fluorometrically labeled oligonucleotide substrates containing MGMT-specific DNA lesions and capillary electrophoresis to detect and quantify these lesions. In comparison with existing traditional assays, this assay was equally sensitive but less time consuming and easier to perform. MGMT promoter methylation was assessed in 41 glioblastomas by bisulfite pyrosequencing, and five samples with different values were chosen for comparison with enzymatic assays. Bisulfite pyrosequencing using primers designed to work in the upstream promoter regions of MGMT demonstrated high quantitative capability and reproducibility in triplicate measurements. In comparative studies, MGMT promoter methylation values obtained by bisulfite pyrosequencing were inversely proportional to the measured enzymatic activity. The present results indicate that the quantification of MGMT methylation by bisulfite pyrosequencing represents its enzymatic activity and thus, its therapeutic responsiveness to alkylating agents.

An analysis of image texture, tumor location, and MGMT promoter methylation in glioblastoma using magnetic resonance imaging

In glioblastoma (GBM), promoter methylation of the DNA repair gene O6-methylguanine-DNA methyltransferase (MGMT) is associated with benefit from chemotherapy. Correlations between MGMT promoter methylation and visually assessed imaging features on magnetic resonance (MR) have been reported suggesting that noninvasive detection of MGMT methylation status might be possible. Our study assessed whether MGMT methylation status in GBM could be predicted using MR imaging. We conducted a retrospective analysis of MR images in patients with newly diagnosed GBM. Tumor texture was assessed by two methods. First, we analyzed texture by expert consensus describing the tumor borders, presence or absence of cysts, pattern of enhancement, and appearance of tumor signal in T2-weighted images. Then, we applied space–frequency texture analysis based on the S-transform. Tumor location within the brain was determined using automatized image registration and segmentation techniques. Their association with MGMT methylation was analyzed. We confirmed that ring enhancement assessed visually is significantly associated with unmethylated MGMT promoter status (P=0.006). Texture features on T2-weighted images assessed by the space–frequency analysis were significantly different between methylated and unmethylated cases (P<0.05). However, blinded classification of MGMT promoter methylation status reached an accuracy of only 71%. There were no significant differences in the locations of methylated and unmethylated GBM tumors. Our results provide further evidence that individual MR features are associated with MGMT methylation but better algorithms for predicting methylation status are needed. The relevance of this study lies on the application of novel techniques for the analysis of anatomical MR images of patients with GBM allowing the evaluation of subtleties not seen by an observer and facilitating the standardization of the methods, decreasing the potential for interobserver bias.

Extent of MGMT promoter methylation correlates with outcome in glioblastomas given temozolomide and radiotherapy

Background:Epigenetic silencing of O6-methylguanine-DNA-methyltransferase (MGMT) by promoter methylation is associated with improved survival in glioblastomas treated with alkylating agents. In this study, we investigated MGMT promoter methylation in glioblastomas treated with temozolomide and radiotherapy in a single UK treatment centre.Methods:Quantitative methylation data at individual CpG sites were obtained by pyrosequencing for 109 glioblastomas.Results:Median overall survival (OS) was 12.4 months with 2-year survival of 17.9%. Pyrosequencing data were reproducible with archival samples yielding data for all glioblastomas. Variation in methylation patterns of discrete CpG sites and intratumoral methylation heterogeneity were observed. A total of 58 out of 109 glioblastomas showed average methylation >non-neoplastic brain in at least one clinical sample; 86% had homogeneous methylation status in multiple samples. Methylation was an independent prognostic factor associated with prolonged progression-free survival (PFS) and OS. Cases with methylation more than 35% had the longest survival (median PFS 19.2; OS 26.2 months, 2-year survival of 59.7%). Significant differences in PFS were seen between those with intermediate or high methylation and unmethylated cases, whereas cases with low, intermediate or high methylation all showed significantly different OS.Conclusions:These data indicate that MGMT methylation is prognostically significant in glioblastomas given chemoradiotherapy in the routine clinic; furthermore, the extent of methylation may be used to provide additional prognostic stratification.