O(6) -methylguanine-DNA methyltransferase (MGMT) promoter methylation and low MGMT-encoded protein expression as prognostic markers in glioblastoma patients treated with biodegradable carmustine wafer implants after initial surgery followed by radiotherapy with concomitant and adjuvant temozolomide

BACKGROUND:

O⁶‐methylguanine‐DNA methyltransferase (MGMT) promoter methylation status was proposed as a prognostic biomarker for patients with glioblastoma. However, the prognostic impact of MGMT in patients with newly diagnosed glioblastoma who receive carmustine‐releasing wafers (Gliadel) along with temozolomide (TMZ) is still unknown.

METHODS:

MGMT promoter methylation status and protein expression were analyzed in formalin‐fixed, paraffin‐embedded tumor specimens obtained from 111 French patients with newly diagnosed glioblastoma. Patients received the Gliadel wafers followed by radiotherapy plus concomitant and adjuvant TMZ chemotherapy while they were enrolled in a French multicenter prospective study.

RESULTS:

For the whole cohort, the median overall survival (OS) was 17.5 months, and the progression‐free survival was 10.3 months. Patients with tumors that harbored MGMT methylation had a significantly longer OS compared with patients who had wild‐type MGMT (21.7 months vs 15.1 months; P = .025). Similarly, patients who had low MGMT protein expression (≤15%) had a significantly improved OS compared with patients who had high MGMT expression (27.0 months vs 15.1 months; P = .021). The extent of resection was the strongest clinical predictor of outcome. In multivariate Cox models that were adjusted for sex, performance status, and extent of surgery, both MGMT methylation and protein expression were identified as independent prognosticators, and the finding was validated internally using a bootstrap resampling technique. Discrepancies were identified between protein expression and MGMT methylation status, thus suggesting that the 2 assays probably assess different biologic features.

CONCLUSIONS:

MGMT promoter methylation status and low MGMT expression both were identified as positive prognosticators in patients with newly diagnosed glioblastoma who underwent surgical resection and received Gliadel wafer implants followed by adjuvant radiotherapy and concomitant oral TMZ chemotherapy (the Stupp protocol). Cancer 2012. © 2012 American Cancer Society.     

Correlation of Clinical Features and Methylation Status of MGMT Gene Promoter in Glioblastomas

In an effort to extend the potential relationship between the methylation status of MGMT promoter and response to CENU therapy, we examined the methylation status of MGMT promoter in 44 patients with glioblastomas. Tumor specimens were obtained during surgery before adjuvant treatment, frozen and stored at -80 degrees C until for DNA extraction process. DNA methylation patterns in the CpG island of the MGMT gene were determined in every tumor by methylation specific PCR (MSP). These results were then related to overall survival and response to alkylating agents using statistical analysis. Methylation of the MGMT promoter was detected in 68% of tumors, and 96.7% of methylated tumors exhibited also an unmethylated status. There was no relationship between the methylation status of the MGMT promoter and overall survival and response to alkylating agents. Our observations do not lead us to consider promoter methylation of MGMT gene as a prognostic factor of responsiveness to alkylating agents in glioblastomas.     

Correlation between O<Superscript>6</Superscript>-methylguanine-DNA methyltransferase and survival in elderly patients with glioblastoma treated with radiotherapy plus concomitant and adjuvant temozolomide

Epigenetic silencing of the O⁶-methylguanine-DNA-methyltransferase (MGMT) gene by promoter methylation is correlated with improved progression-free survival (PFS) and overall survival (OS) in adult patients with newly diagnosed glioblastoma multiforme (GBM) who receive alkylating agents. The aim of this study is to determine the correlation between MGMT and survival in elderly patients with GBM treated with radiotherapy (RT) and temozolomide (TMZ). Eighty-three patients aged 70 years or older with histologically confirmed GBM treated with RT plus TMZ between February 2005 and September 2009 were investigated in this study. The methylation status of the MGMT promoter was determined by polymerase chain reaction analysis. Median PFS and OS were 7.5 and 12.8 months, respectively. The MGMT promoter was methylated in 42 patients (50.6%) and unmethylated in 41 patients (49.4%). Median OS was 15.3 months in methylated patients and 10.2 months in unmethylated patients (P = 0.0001). Median PFS was 10.5 months in methylated tumors and 5.5 months in unmethylated tumors (P = 0.0001). On multivariate analysis MGMT methylation status emerged as the strongest independent prognostic factor for OS and PFS (P = 0.004 and P = 0.005, respectively). The results of the present study suggest that MGMT methylation status might be an important prognostic factor associated with better OS and PFS in elderly patients with GBM treated with RT and TMZ.     

Clinical trial substantiates the predictive value of O-6-methylguanine-DNA methyltransferase promoter methylation in glioblastoma patients treated with temozolomide.

PURPOSE: In the setting of a prospective clinical trial, we determined the predictive value of the methylation status of the O-6-methylguanine-DNA methyltransferase (MGMT) promoter for outcome in glioblastoma patients treated with the alkylating agent temozolomide. Expression of this excision repair enzyme has been associated with resistance to alkylating chemotherapy. EXPERIMENTAL DESIGN: The methylation status of MGMT in the tumor biopsies was evaluated in 38 patients undergoing resection for newly diagnosed glioblastoma and enrolled in a Phase II trial testing concomitant and adjuvant temozolomide and radiation. The epigenetic silencing of the MGMT gene was determined using methylation-specific PCR. RESULTS: Inactivation of the MGMT gene by promoter methylation was associated with longer survival (P = 0.0051; Log-rank test). At 18 months, survival was 62% (16 of 26) for patients testing positive for a methylated MGMT promoter but reached only 8% (1 of 12) in absence of methylation (P = 0.002; Fisher's exact test). In the presence of other clinically relevant factors, methylation of the MGMT promoter remains the only significant predictor (P = 0.017; Cox regression). CONCLUSIONS: This prospective clinical trial identifies MGMT-methylation status as an independent predictor for glioblastoma patients treated with a methylating agent. The association of the epigenetic inactivation of the DNA repair gene MGMT with better outcome in this homogenous cohort may have important implications for the design of future trials and supports efforts to deplete MGMT by O-6-benzylguanine, a noncytotoxic substrate of this enzyme.     

Predictive impact of MGMT promoter methylation in glioblastoma of the elderly

O(6)-methylguanine-DNA-methyltransferase (MGMT) promoter methylation identifies a subpopulation of glioblastoma patients with more favorable prognosis and predicts a benefit from alkylating agent chemotherapy (CT). Little is known about its prevalence and clinical significance in older glioblastoma patients. We studied 233 glioblastoma patients aged 70 years or more (144 males, 89 females, median age: 74 years, range: 70.0-86.6 years), who were prospectively enrolled in the German Glioma Network, for MGMT promoter methylation by methylation-specific PCR (MSP) in all patients and DNA pyrosequencing in 166 patients. MGMT data were correlated with patient outcome. Median progression-free survival (PFS) was 4.8 months (95% CI: 4.3-5.3) and median overall survival (OS) was 7.7 months (95% CI: 6.3-9.0). MGMT promoter methylation was detected by MSP in 134 patients (57.5%). For the whole cohort, PFS was 5.2 versus 4.7 months (p = 0.207) and OS was 8.4 versus 6.4 months (p = 0.031) in patients with versus without MGMT promoter methylation. Patients with MGMT methylated tumors had longer PFS when treated with radiotherapy (RT) plus CT or CT alone compared to patients treated with RT alone. Patients with MGMT unmethylated tumors appeared to derive no survival benefit from CT, regardless of whether given at diagnosis together with RT or as a salvage treatment. Patients treated with RT plus CT or CT alone demonstrated longer OS when pyrosequencing revealed >25% MGMT methylated alleles. Taken together, MGMT promoter methylation may be a useful biomarker to stratify elderly glioblastoma patients for treatment with versus without alkylating agent CT.     

Aberrant MGMT (O6-methylguanine-DNA methyltransferase) promoter methylation in choroid plexus tumors

Aberrant methylation of the MGMT (O6-methylguanine-DNA methyltransferase) DNA-repair gene is a predictive marker for the response to chemotherapy with alkylating agents (e.g., temozolomide) in malignant gliomas. Since temozolomide is considered for the treatment of choroid plexus tumors, MGMT promoter methylation status was retrospectively assessed in 36 choroid plexus tumors using methylation specific PCR, combined bisulfite restriction analysis (COBRA), and clone sequencing. By methylation specific PCR, all samples demonstrated a signal for MGMT methylation. COBRA confirmed >10% methylation of CpGs 17 and 31 in 58% of tumors. Clone sequencing of six cases methylated by COBRA confirmed aberrant methylation including a previously recognized enhancer element. In conclusion, MGMT promoter methylation is frequent in choroid plexus tumors and can be quantified using COBRA. Determination of MGMT promoter methylation status might be useful for the stratification of patients for alkylator-based treatments in future clinical trials. The authors M. Hasselblatt and J. Mühlisch have contributed equally.     

CpG island hypermethylation of the DNA repair enzyme methyltransferase predicts response to temozolomide in primary gliomas.

PURPOSE: The DNA repair enzyme O(6)-methylguanine DNA methyltransferase (MGMT) inhibits the killing of tumor cells by alkylating agents, and its loss in cancer cells is associated with hypermethylation of the MGMT CpG island. Thus, methylation of MGMT has been correlated with the clinical response to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in primary gliomas. Here, we investigate whether the presence of MGMT methylation in gliomas is also a good predictor of response to another emergent alkylating agent, temozolomide. EXPERIMENTAL DESIGN: Using a methylation-specific PCR approach, we assessed the methylation status of the CpG island of MGMT in 92 glioma patients who received temozolomide as first-line chemotherapy or as treatment for relapses. RESULTS: Methylation of the MGMT promoter positively correlated with the clinical response in the glioma patients receiving temozolomide as first-line chemotherapy (n = 40). Eight of 12 patients with MGMT-methylated tumors (66.7%) had a partial or complete response, compared with 7 of 28 patients with unmethylated tumors (25.0%; P = 0.030). We also found a positive association between MGMT methylation and clinical response in those patients receiving BCNU (n = 35, P = 0.041) or procarbazine/1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (n = 17, P = 0.043) as first-line chemotherapy. Overall, if we analyze the clinical response of all of the first-line chemotherapy treatments with temozolomide, BCNU, and procarbazine/1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea as a group in relation to the MGMT methylation status, MGMT hypermethylation was strongly associated with the presence of partial or complete clinical response (P < 0.001). Finally, the MGMT methylation status determined in the initial glioma tumor did not correlate with the clinical response to temozolomide when this drug was administered as treatment for relapses (P = 0.729). CONCLUSIONS: MGMT methylation predicts the clinical response of primary gliomas to first-line chemotherapy with the alkylating agent temozolomide. These results may open up possibilities for more customized treatments of human brain tumors.     

Prognostic significance of O6-methylguanine-DNA methyltransferase determined by promoter hypermethylation and immunohistochemical expression in anaplastic gliomas.

PURPOSE: Anaplastic gliomas constitute a heterogeneous group of tumors with different therapeutic responses to adjuvant chemotherapy with alkylating agents. O6-Methylguanine-DNA methyltransferase (MGMT), a DNA repair protein, is one of the implicated factors in glioma chemoresistance.The prognostic value of MGMT remains controversial due in part to the fact that previous published studies included heterogeneous groups of patients with different tumor grades. The aim of this study was to evaluate the prognostic significance of MGMT in patients with anaplastic glioma. EXPERIMENTAL DESIGN: Ninety-three patients with anaplastic glioma were analyzed for MGMT protein expression by immunohistochemistry. In addition, for those patients from whom a good yield of DNA was obtained (n = 40), MGMT promoter methylation profile was analyzed by methylation-specific PCR. MGMT prognostic significance was evaluated together with other well-known prognostic factors. RESULTS: Fifty-one tumors (54.8%) showed nuclear staining of MGMT. There was a trend towards longer overall survival for those patients with negative MGMT immunostaining (hazard ratio, 1.66; P = 0.066). In a secondary analysis including those patients who actually received chemotherapy (n = 72), the absence of MGMT expression was independently associated with better survival (hazard ratio, 2.12; P = 0.027). MGMT promoter methylation was observed in 50% of the analyzed tumors. No statistical correlation between MGMT expression and MGMT promoter hypermethylation was observed. CONCLUSIONS: Unlike previous studies, we did not find a correlation between MGMT promoter methylation and survival. However, we observed a correlation between MGMT protein expression and survival in those patients who received chemotherapy thus suggesting that the absence of MGMT expression is a positive predictive marker in patients with anaplastic glioma.     

MGMT in primary and recurrent human glioblastomas after radiation and chemotherapy and comparison with p53 status and clinical outcome

The DNA repair protein O(6)-methylguanine-DNA methyltransferase (MGMT) plays a pivotal role in alkylating drug resistance. Here, we determined MGMT activity in primary and recurrent glioblastomas (GBM, WHO grade IV) of patients who received radiation therapy (RT) or RT plus chemotherapy with alkylating agents (temozolomide, chloroethylnitrosoureas). The mean MGMT activity of untreated GBM was 37 +/- 45 (range 0-205) fmol/mg proteins. In the 1st, 2nd and 3rd recurrences, MGMT activity increased from 66 +/- 50 (13-194) to 68 +/- 44 (14-143) and 182 +/- 163 (64-423) fmol/mg protein, respectively. Comparing patients who received RT only with RT plus chemotherapy, a significant increase of MGMT in 1st recurrences was only found after treatment with RT plus chemotherapy, indicating either selection of MGMT expressing cells or induction of the MGMT gene by alkylating agents. The p53 status was not significantly related to the MGMT expression level, although a trend for lower MGMT activity in p53 positively stained tumors was observed. Patients expressing MGMT activity of 相似文献   

O6-methylguanine-DNA methyltransferase methylation and TP53 mutation in malignant astrocytomas and their relationships with clinical course

Epigenetic silencing of O(6)-methylguanine-DNA methyltransferase (MGMT) by promoter methylation can confer cancer cells with an increased sensitivity to alkylating chemotherapeutic agents and a higher susceptibility to TP53 transition mutations. The aim of our study was to assess the correlation of promoter methylation of the MGMT gene with TP53 mutations and the clinical characteristics of malignant astrocytomas. We analyzed the MGMT promoter methylation and TP53 mutations in 45 malignant astrocytomas (16 anaplastic astrocytomas and 29 glioblastomas multiforme) treated prospectively with 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-2(2-chloroethyl)-3-nitrosourea, interferon-beta and radiation therapy, and evaluated their clinical usefulness. MGMT promoter methylation was found in 17 (38%) of the 45 newly diagnosed malignant astrocytomas. A clear trend existed between MGMT methylation and G:C to A:T transition mutations of TP53 (p = 0.0596). Patients with MGMT-methylated tumors displayed a greater chance of responding to adjuvant therapy as compared with those with MGMT-unmethylated tumors (p = 0.0393). TP53 mutation was not significantly associated with the clinical response (p = 0.1310). While neither MGMT methylation nor TP53 mutation had a significant effect on prognosis of the whole population, the presence of MGMT methylation emerged as a significant predictor of a longer survival when exclusively analyzing 29 patients with glioblastomas multiforme. These findings highlight the importance of MGMT methylation as a specific predictive factor for responsiveness to nitrosourea chemotherapy.     

Prognostic impact of O6‐methylguanine‐DNA methyltransferase silencing in patients with recurrent glioblastoma multiforme who undergo surgery and carmustine wafer implantation

BACKGROUND:

O⁶‐methylguanine‐DNA methyltransferase (MGMT) is a key enzyme in the DNA repair process after alkylating agent action. Epigenetic silencing of the MGMT gene by promoter methylation has been associated with longer survival in patients with newly diagnosed glioblastoma multiforme (GBM) who receive alkylating agents. In this study, the authors evaluated the prognostic value of different biomarkers in recurrent GBM and analyzed the changes in MGMT status between primary tumors and recurrent tumors.

METHODS:

Twenty‐two patients who had recurrent GBM and who underwent surgery with carmustine wafer implantation were enrolled prospectively between 2005 and 2007. The authors investigated the correlation between MGMT silencing in the tumor at recurrence and survival taking into account other clinically recognized prognostic factors. MGMT status was determined by using methylation‐specific polymerase chain reaction analysis, a high‐throughput quantitative methylation assay, and immunohistochemistry. In addition, expression analyses of human mutL homolog 1, human mutS homolog 2, and tumor necrosis factor α‐induced protein 3 at recurrence were conducted with regard to their prognostic impact.

RESULTS:

The median progression‐free survival (PFS) and overall survival (OS) rates after recurrence were 3.6 months and 9.9 months, respectively, and the 6‐month PFS rate after recurrence was 27.2%. On multivariate analysis, only age (P = .04) and MGMT promoter hypermethylation at recurrence, as determined by MethyLight technology (P = .0012) and methylation‐specific polymerase chain reaction (MSP) analysis (P = .004), were correlated with better PFS. On multivariate analysis, only MGMT promoter hypermethylation at recurrence, as determined by using MethyLight technology (P = .019) and MSP analysis (P = .046), was associated with better OS.

CONCLUSIONS:

MGMT methylation status was an important prognostic factor in patients with recurrent GBM who underwent surgery plus carmustine wafer implantation; therefore, it was useful in predicting the outcome of GBM therapy at recurrence. Cancer 2009. © 2009 American Cancer Society.     

MGMT基因启动子甲基化检测在脑胶质瘤化疗中的意义

背景与目的：如何预测和克服肿瘤细胞对化疗药物的耐药性,实施个体化治疗是肿瘤化疗急需解决的问题。与基因启动子甲基化密切相关的DNA损伤修复基因O^6-甲基鸟嘌呤-DNA甲基转移酶（O^6-methylguanine-DNA methyhransferase,MGMT）表观沉默与肿瘤对烷化剂药物化疗敏感性密切相关。本研究探讨检测MGMT基因启动子CpG岛甲基化在判断脑胶质瘤患者预后及预测肿瘤对烷化剂药物耐药性中的意义。方法：甲基化特异性PCR（MSP）法检测脑胶质瘤组织及肿瘤细胞株MGMT基因启动子甲基化状态,蛋白印迹和免疫组化法测定蛋白表达。MTF法检测肿瘤细胞株对烷化剂药物敏感性,将患者随访资料针对MGMT甲基化状态绘制Kaplan-Meier生存曲线,并进行log—rank检验分析。结果：39例脑胶质瘤患者组织MGMT基因启动子甲基化发生率为46．2％,蛋白表达阳性率为61．5％,且肿瘤组织中MGMT基因甲基化状态与蛋白表达显著相关（P〈0．05）：6例正常组织均未检测出基因甲基化。MGMT基因过甲基化的脑胶质瘤SHG44细胞株用5-Aza-CdR处理后完全脱甲基化．MGMT蛋白恢复了表达,同时细胞株对烷化剂药物敏感性也发生逆转．由敏感转变为耐受。在采用手术、放疗和烷化剂尼莫司汀化疗等综合治疗的39例脑胶质瘤患者中,MGMT基因甲基化的患者生存率显著高于MGMT基因未甲基化患者（P〈0．05）。结论：MGMT基因甲基化状态与蛋白表达及肿瘤细胞对烷化剂药物敏感性密切相关,有可能替代MGMT蛋白检测成为判断脑胶质瘤患者预后和预测肿瘤对烷化剂化疗耐药性的标志分子。     

MGMT promoter methylation in plasma of glioma patients receiving temozolomide

Promoter methylation of the O6-methylguanine-DNA methyltransferase (MGMT) gene plays a role in cellular response to alkylating agents. In the present study aimed to: (i) evaluate the concordance between MGMT promoter methylation status in tumor tissue and plasma; (ii) monitor MGMT promoter methylation status in plasma taken before and during temozolomide treatment; (iii) explore the value of MGMT promoter methylation status in plasma as a prognostic/predictive biomarker in glioma patients. We enrolled 58 patients with histologically confirmed glioma at different grades of malignancy. All patients underwent surgical resection and temozolomide treatment. Paraffin-embedded tumor tissue was available for 48 patients. Blood samples were collected from all patients before temozolomide treatment (baseline) and at each MRI examination for a 12-month period. MGMT promoter methylation status was assessed in both sample types by real time PCR with a specific probe. The frequency of MGMT promoter methylation was 60.4 % in tumor tissue and 41.38 % in plasma. MGMT promoter methylation status was concordant in the two sample types (Kappa = 0.75, 95 % confidence interval (CI) 0.57–0.93; p value <0.001). Overall and progression-free survival were longer in patients with methylated MGMT promoter. Mortality was higher in patients with unmethylated MGMT promoter, whether in tumor tissue [hazard ratio (HR) 2.21; 95 % CI 0.99–4.95] or plasma (HR 2.19; 95 % CI 1.02–4.68). Progression-free survival was shorter in patients with unmethylated MGMT promoter, whether in tissue (HR 2.30; 95 % CI 1.19–4.45) or plasma (HR 1.77; 95 % CI 0.95–3.30). The cumulative incidence of unmethylated MGMT promoter in plasma at baseline was 58 %, and reached virtually 100 % at 12 months. In conclusion MGMT promoter methylation status in tumor tissue and plasma was highly concordant, and both were associated with longer survival, supporting the role of the detection of methylated MGMT promoter in predicting treatment response. However we suggest caution in using plasma as a surrogate of tumor tissue due to possible false-negative results.     

MGMT analysis in gliomas

MGMT status is now regarded as a strong predictive factor of response to standard treatment of newly diagnosed glioblastomas involving temozolomide (TMZ) and radiotherapy. MGMT promoter methylation is also a prognostic factor - independent of treatment - in anaplastic gliomas. The predictive function can be explained by the role of the DNA repair enzyme MGMT, which antagonizes the effects of alkylating agents such as TMZ. MGMT promoter methylation could also reflect a particular molecular phenotype with its own specific prognostic significance. Since MGMT status determination is becoming a crucial biological marker in new clinical glioma trials, and is beginning to be used in day-to-day clinical practice, there is currently a strong need to determine the best technique for MGMT analysis. A French multicenter study has been set up for this purpose.     

Predictive value of the MGMT promoter methylation status in metastatic melanoma patients receiving first-line temozolomide plus bevacizumab in the trial SAKK 50/07

The O6-methylguanine-DNA-methyltransferase (MGMT) promoter methylation status is a predictive parameter for the response of malignant gliomas to alkylating agents such as temozolomide. First clinical trials with temozolomide plus bevacizumab therapy in metastatic melanoma patients are ongoing, although the predictive value of the MGMT promoter methylation status in this setting remains unclear. We assessed MGMT promoter methylation in formalin-fixed, primary tumor tissue of metastatic melanoma patients treated with first-line temozolomide and bevacizumab from the trial SAKK 50/07 by methylation-specific polymerase chain reaction. In addition, the MGMT expression levels were also analyzed by MGMT immunohistochemistry. Eleven of 42 primary melanomas (26%) revealed a methylated MGMT promoter. Promoter methylation was significantly associated with response rates CR + PR versus SD + PD according to RECIST (response evaluation criteria in solid tumors) (p<0.05) with a trend to prolonged median progression-free survival (8.1 versus 3.4 months, p>0.05). Immunohistochemically different protein expression patterns with heterogeneous and homogeneous nuclear MGMT expression were identified. Negative MGMT expression levels were associated with overall disease stabilization CR+PR+SD versus PD (p=0.05). There was only a poor correlation between MGMT methylation and lack of MGMT expression. A significant proportion of melanomas have a methylated MGMT promoter. The MGMT promoter methylation status may be a promising predictive marker for temozolomide therapy in metastatic melanoma patients. Larger sample sizes may help to validate significant differences in survival type endpoints.     

老年胶质母细胞瘤患者MGMT甲基化状态对放化疗及预后影响

目的:探讨O-6-甲基鸟嘌呤-DNA甲基转移酶(MGMT)基因启动子甲基化状态对老年胶质母细胞瘤(GBM)治疗及预后的影响。方法:回顾性分析天津市环湖医院2012—2018年收治的65例新诊断的老年GBM患者的临床资料。所有患者均在术后接受了调强放疗,49例患者接受了替莫唑胺单药化疗。依据MGMT启动子甲基化状态分为M...     

O6-Methylguanine DNA methyltransferase protein expression in tumor cells predicts outcome of temozolomide therapy in glioblastoma patients

O⁶-Methylguanine DNA methyltransferase (MGMT) is implicated as a major predictive factor for treatment response to alkylating agents including temozolomide (TMZ) of glioblastoma multiforme (GBM) patients. However, whether the MGMT status in GBM patients should be detected at the level of promoter methylation or protein expression is still a matter of debate. Here, we compared promoter methylation (by methylation-specific polymerase chain reaction) and protein expression (by Western blot) in tumor cell explants with respect to prediction of TMZ response and survival of GBM patients (n = 71). Methylated MGMT gene promoter sequences were detected in 47 of 71 (66%) cases, whereas 37 of 71 (52%) samples were scored positive for MGMT protein expression. Although overall promoter methylation correlated significantly with protein expression (χ² test, P < .001), a small subgroup of samples did not follow this association. In the multivariate Cox regression model, a significant interaction between MGMT protein expression, but not promoter methylation, and TMZ therapy was observed (test for interaction, P = .015). In patients treated with TMZ (n = 42), MGMT protein expression predicted a significantly shorter overall survival (OS; hazard ratio [HR] for death 5.53, 95% confidence interval [CI] 1.76–17.37; P = .003), whereas in patients without TMZ therapy (n = 29), no differences in OS were observed (HR for death 1.00, 95% CI 0.45–2.20; P = .99). These data suggest that lack of MGMT protein expression is superior to promoter methylation as a predictive marker for TMZ response in GBM patients.     

Outcomes in Elderly Patients with Glioblastoma Multiforme Treated with Short-Course Radiation Alone Compared to Short-Course Radiation and Concurrent and Adjuvant Temozolomide Based on Performance Status and Extent of Resection

(1) Background: Studies in elderly patients over the age of 65 with glioblastoma have shown survival benefits of short-course radiation therapy with concurrent and adjuvant temozolomide, making it the standard of care adopted at Juravinski Cancer Center. Our study retrospectively examines patients with GBM aged ≥ 70 at the JCC treated with short-course radiation alone compared to those treated with short-course radiation and concurrent and adjuvant TMZ, to determine if there is a difference in outcomes based on performance status. (2) Methods: A retrospective chart review was conducted at JCC using patients diagnosed with GBM in 2014–2017 (treated with the old protocol of short-course RT alone) versus those diagnosed in 2017–2019 (treated with the new protocol of short-course radiation and TMZ). Patient demographics, treatments, outcomes, and baseline KPS were analyzed. (3) Results: No clear benefit and more neurologic decline post treatment were seen in patients with borderline performance status and subtotal resection who underwent concurrent treatment with temozolomide and radiation. The addition of temozolomide was most helpful in patients with good performance status and a gross total resection. Variable outcomes were seen in patients with mixed traits. (4) Conclusions: This study suggests that performance status and extent of resection are significant determinants of patient response to treatment. In the case of elderly patients with borderline performance status and GTR or those with good performance status and STR, also described as “mixed traits”, it may be beneficial to pursue single modality treatment, ideally based on MGMT promoter methylation status as opposed to bimodality treatment in order to maintain the best QOL.     

Induction of MGMT expression is associated with temozolomide resistance in glioblastoma xenografts

Temozolomide (TMZ)-based therapy is the standard of care for patients with glioblastoma multiforme (GBM), and resistance to this drug in GBM is modulated by the DNA repair protein O(6)-methylguanine-DNA methyltransferase (MGMT). Expression of MGMT is silenced by promoter methylation in approximately half of GBM tumors, and clinical studies have shown that elevated MGMT protein levels or lack of MGMT promoter methylation is associated with TMZ resistance in some, but not all, GBM tumors. In this study, the relationship between MGMT protein expression and tumor response to TMZ was evaluated in four GBM xenograft lines that had been established from patient specimens and maintained by serial subcutaneous passaging in nude mice. Three MGMT unmethylated tumors displayed elevated basal MGMT protein expression, but only two of these were resistant to TMZ therapy (tumors GBM43 and GBM44), while the other (GBM14) displayed a level of TMZ sensitivity that was similar in extent to that seen in a single MGMT hypermethylated line (GBM12). In tissue culture and animal studies, TMZ treatment resulted in robust and prolonged induction of MGMT expression in the resistant GBM43 and GBM44 xenograft lines, while MGMT induction was blunted and abbreviated in GBM14. Consistent with a functional significance of MGMT induction, treatment of GBM43 with a protracted low-dose TMZ regimen was significantly less effective than a shorter high-dose regimen, while survival for GBM14 was improved with the protracted dosing regimen. In conclusion, MGMT expression is dynamically regulated in some MGMT nonmethylated tumors, and in these tumors, protracted dosing regimens may not be effective.     

Hypermethylation of O6-methylguanine-DNA methyltransferase promoter may predict nonrecurrence after chemotherapy in colorectal cancer cases.

PURPOSE: Because O(6)-methylguanine-DNA methyltransferase (MGMT) plays an essential role in repairing DNA damage caused by environmental alkylating chemicals, we were interested in determining whether we could see any obvious changes in the properties of colorectal cancers (CRCs) in which the MGMT gene had been silenced by hypermethylation and hence in which very few MGMT protein molecules were being produced. EXPERIMENTAL DESIGN: We used a methylation-specific PCR assay to determine the methylation status of the MGMT promoter in the DNA molecules extracted from CRC and nontumor tissue samples from 116 patients who had undergone CRC surgery and for whom clinical outcome information was available on file. RESULTS: We found evidence of MGMT promoter hypermethylation in 26 of 90 CRC cases, and we noted that the later the stage at which a tumor was diagnosed, the less likely its MGMT promoter was to be methylated (P = 0.03, adjusting for chemotherapy), especially for stage D patients (P = 0.01). We also found that CRC patients with unmethylated MGMT promoters were much more likely to experience recurrence within 36 months than patients with hypermethylated MGMT promoters (crude odds ratio, 14.0; 95% confidence interval, 2.42-81.01). After adjustment for stage, CRC patients with unmethylated MGMT promoters who had been exposed to chemotherapy were found to have a 5.3-fold greater risk of recurrence than those who had no exposure to chemotherapy (95% confidence interval, 1.15-30.92). CONCLUSIONS: Hypermethylation of the MGMT promoter may be predictive of a low risk of recurrence in CRC patients receiving adjuvant chemotherapy.