Prognostic Significance ofO6-Methylguanine-DNA Methyltransferase Determined by Promoter Hypermethylation and Immunohistochemical Expression in Anaplastic Gliomas

Clinical Relevance and Interplay between miRNAs in Influencing Glioblastoma Multiforme Prognosis

Glioblastoma multiforme (GBM) is usually treated with surgery followed by adjuvant partial radiotherapy combined with temozolomide (TMZ) chemotherapy. Recent studies demonstrated a better survival and good response to TMZ in methylguanine-DNA methyltransferase (MGMT)-methylated GBM cases. However, approximately 20% of patients with MGMT-unmethylated GBM display an unexpectedly favorable outcome. Therefore, additional mechanisms related to the TMZ response need to be investigated. As such, we decided to investigate the clinical relevance of six miRNAs involved in brain tumorigenesis (miR-181c, miR-181d, miR-21, miR-195, miR-196b, miR-648) as additional markers of response and survival in patients receiving TMZ for GBM. We evaluated miRNA expression and the interplay between miRNAs in 112 IDH wt GBMs by applying commercial assays. Then, we correlated the miRNA expression with patients' clinical outcomes. Upon bivariate analyses, we found a significant association between the expression levels of the miRNAs analyzed, but, more interestingly, the OS curves show that the combination of low miR-648 and miR-181c or miR-181d expressions is associated with a worse prognosis than cases with other low-expression miRNA pairs. To conclude, we found how specific miRNA pairs can influence survival in GBM cases treated with TMZ.

Quantitative analysis of MGMT promoter methylation status changes by pyrosequencing in recurrent glioblastoma

MGMT promoter methylation status can change in response to several factors, treatment with alkylating therapy being the mechanism more commonly cited in the literature. Some authors have attempted to quantify these alterations, with inconsistent results. This study aims to determine changes in MGMT promoter methylation status by pyrosequencing, which quantitatively yields results, in a cohort of patients reoperated for recurrent glioblastoma and having previously completed the Stupp protocol. Methylation status of the MGMT promoter gene of a total of 24 pairs of glioblastoma preselected tumor samples was retrospectively analyzed using pyrosequencing and depicted as percentages or categories (hypermethylated, intermediate methylation, unmethylated). Matched samples were compared using Wilcoxon signed-rank test, and log-rank test was used to establish a correlation with survival data. The median value of MGMT promoter methylation status declined after adjuvant treatment from 20.35% to 14.25% (p = 0.346). A significant correlation between methylation in primary samples and overall survival (p = 0.05) and progression-free survival (p = 0.024) was found. Intermediate methylation status at recurrence was linked to greater survival after progression, without reaching statistical significance (post-progression survival [PPS]) (p = 0.217). Although treatment with alkylating chemotherapy was a common feature in all patients of our cohort, switching in both directions was observed when MGMT promoter methylation status was analyzed as a continuous variable. These data suggest that the dynamics of epigenetics may be very complex and not entirely explained by clonal selection influenced by temozolomide.

Identification of MGMT Downregulation Induced by miRNA in Glioblastoma and Possible Effect on Temozolomide Sensitivity

Glioblastoma multiforme (GBM) remains one of the tumors with the worst prognosis. In recent years, a better overall survival (OS) has been described in cases subjected to Gross Total Resection (GTR) that were presenting hypermethylation of Methylguanine-DNA methyltransferase (MGMT) promoter. Recently, also the expression of specific miRNAs involved in MGMT silencing has been related to survival. In this study, we evaluate MGMT expression by immunohistochemistry (IHC), MGMT promoter methylation and miRNA expression in 112 GBMs and correlate the data to patients' clinical outcomes. Statistical analyses demonstrate a significant association between positive MGMT IHC and the expression of miR-181c, miR-195, miR-648 and miR-767.3p between unmethylated cases and the low expression of miR-181d and miR-648 and between methylated cases and the low expression of miR-196b. Addressing the concerns of clinical associations, a better OS has been described in presence of negative MGMT IHC, in methylated patients and in the cases with miR-21, miR-196b overexpression or miR-767.3 downregulation. In addition, a better progression-free survival (PFS) is associated with MGMT methylation and GTR but not with MGMT IHC and miRNA expression. In conclusion, our data reinforce the clinical relevance of miRNA expression as an additional marker to predict efficacy of chemoradiation in GBM.

Expression and methylation status of MMR and MGMT in well-differentiated pancreatic neuroendocrine tumors and potential clinical applications

PURPOSE

Recent studies claim that immune checkpoint inhibitors are effective in defective mismatch repair (dMMR) cancers. This raises the question of whether similar therapies are effective in PanNETs (pancreatic neuroendocrine tumors); however, in general, assessment of MMR status in PanNETs has been inconsistent in previous studies. MGMT (O6-methylguanine-DNA methyltransferase) is potentially important for guiding temozolomide (TMZ) therapy in glioblastoma. The number of reports on MGMT expression and promoter methylation in PanNETs are limited.

METHODS

In this study we assessed the expression of MGMT and MMR proteins MSH2, MSH6, MLH1 and PMS2 in a series of PanNETs by IHC. The methylation status of MGMT and MMR genes in a subset of PanNETs was further assessed by MS-MLPA analysis. Survival curves were constructed using the Kaplan-Meier method, and differences were assessed using the log-rank test. Multivariate Cox proportional hazards regression models were used to determine the prognostic value of the variables.

RESULTS

According to evaluation criteria for mismatch repair defects, none of PanNETs shown nuclear staining loss for MSH2, MSH6, MLH1, and PMS2. MGMT low-intensity PanNETs were more commonly found in higher grade, higher Ki67 index and non-functional tumors (P < 0.05). In multivariate analysis, stage III-IV and low-intensity MGMT were shown to be independent risk factors for progression of PanNETs in the entire cohort, non-functioning subgroup and G2 subgroup (P < 0.05 for all). MGMT promoter methylation tended to be higher in the group with low expression of MGMT, However, methylation of MGMT did not statistically correlate with low expression of MGMT (P = 0.153).

CONCLUSIONS

In conclusion, our study suggests that decreased expression of MGMT but not MMR is associated with a higher risk of progression of pancreatic neuroendocrine tumors.

Is IDH status the only factor predicting prognosis in newly diagnosed anaplastic glioma patients? Outcome evaluation and prognostic factor analysis in a single-institution large series

OBJECTIVE

Anaplastic gliomas (AGs) are an extremely heterogeneous group of primary brain tumors. More recently, new discoveries have indicated that isocitrate dehydrogenase (IDH) mutation status is the most important parameter predicting survival. The primary aim of the present analysis was to identify prognostic factors, other than IDH status, that eventually impact survival.

METHODS

Patients with available clinical, imaging, and molecular profile data who were amenable to resection were evaluated. The extent of resection (EOR) was defined as gross-total resection (GTR), near-total resection (NTR), subtotal resection (STR), or partial resection (PR). Residual tumor volume (RTV) was quantified. Following surgery, patients received adjuvant chemotherapy alone, radiation therapy plus concomitant and adjuvant temozolomide (TMZ), or sequential radio-chemotherapy. Clinical outcome was evaluated by neurological examination and MRI 1 month after treatment and every 4 months thereafter. Tumor progression was defined according to the Response Assessment in Neuro-Oncology (RANO) working group.

RESULTS

Among 402 patients referred to the authors' institution for AG, 142 were included in the present analysis. Eighty-eight (62%) were male and 54 (38%) were female, with a median age of 43 years (range 19-70 years). At admission, most patients had a Karnofsky Performance Scale score of 90-100 (84.5%) and were symptomatic (93.7%). Forty-eight (33.8%) patients had newly diagnosed anaplastic oligodendrogliomas (AOs), and 94 (66.2%) had anaplastic astrocytomas (AAs). Most of them had mutant IDH tumors (67.6%) and methylated O 6-methylguanine-DNA-methyltransferase (MGMT) promoter status (71.8%). GTR was performed in more than half of the patients (56.3%). RTV was detected in 83 (58.5%) patients. Following surgery, 72 (50.7%) patients received radiotherapy with concomitant and adjuvant TMZ, 48 (33.8%) received sequential radio-chemotherapy, and 22 (15.5%) received adjuvant chemotherapy alone. The median follow-up time was 40 months (range 16-146 months). The median PFS time and the 1-, 3-, and 5-year PFS rates were 35 months (95% CI 27-76) and 78.9% ± 3.4%, 49.7% ± 4.6%, and 42.7% ± 5.4%, respectively. The median OS time and the 1-, 3-, and 5-year OS rates were 91 months (95% CI 66-95) and 90.1% ± 2.5%, 70.9% ± 4.2%, and 61.8% ± 4.9%, respectively. Prognostic factors predicting survival other than molecular profile were the EOR and the RTV (p < 0.0001). Sequential radio-chemotherapy was the more effective treatment administered.

CONCLUSIONS

In addition to IDH status, EOR and the RTV have proved to statistically impact survival. The pivotal role of adjuvant radiotherapy has been recorded in all AG patients, regardless of tumor features.

The predominant expression of cancer stem cell marker ALDH1A3 in tumor infiltrative area is associated with shorter overall survival of human glioblastoma

Background

ALDH1A3 is a cancer stem cell marker in neoplasms including glioblastoma (GBM). However, the comprehensive role of ALDH1A3 in GBM remains unclear. This study attempted to investigate the expression of ALDH1A3 in human GBM tissues and its association with clinical parameters.

Methods

Thirty primary GBM and 9 control were enrolled in this study. ALDH1A3 mRNA and protein expression levels were detected by RT²-PCR and western blot, respectively. Immunohistochemistry and immunofluorescence staining were performed to evaluate the regional and cellular expression manner of ALDH1A3. The association of ALDH1A3 expression with multiple clinical parameters was analyzed.

Results

ALDH1A3 protein level, but not mRNA level, in a subgroup of GBM was significantly higher than that in the control group. ALDH1A3 immunoreactivity was detected heterogeneously in individual GBMs. Fifteen of 30 cases showed a positive of ALDH1A3 immunoreactivity which was predominantly observed in the tumor infiltrative area (TI). Double immunofluorescence staining revealed a co-localization of ALDH1A3 with GFAP in glial-shaped cells and in tumor cells. ALDH1A3 immunoreactivity was often merged with CD44, but not with CD68. Moreover, ALDH1A3 expression was positively associated with the tumor edema grade and inversely with overall survival (OS) (median OS: 16 months vs 10 months), but with neither MGMT promoter methylation status nor Ki67 index in GBM. An upregulation of ALDH1A3 was accompanied by a reduced expression of STAT3β and p-STAT3β.

Conclusions

Inter- and intra-tumoral heterogeneous expression of ALDH1A3 was exhibited in GBMs. A high immunoreactivity of ALDH1A3 in tumor infiltrative area was associated with shorter OS, especially in patients with MGMT promoter methylation. Our findings propose ALDH1A3 not only as a predictive biomarker but also as a potential target for personalized therapy of GBM.

Pulsed and Discontinuous Electromagnetic Field Exposure Decreases Temozolomide Resistance in Glioblastoma by Modulating the Expression of O6-Methylguanine-DNA Methyltransferase, Cyclin-D1, and p53

Background: Glioblastoma is a malignant and very aggressive brain tumor with a poor prognosis. Despite having chemotherapy concomitant with surgery and/or radiation therapy, the median survival of glioblastoma-affected people is less than 1 year. Temozolomide (TMZ) is a chemotherapeutic used as a first line treatment of glioblastoma. Several studies have reported that resistance to TMZ due to overexpression of O⁶-methylguanine-DNA methyltransferase (MGMT) is the main reason for treatment failure. Several studies described that pulsed-electromagnetic field (EMF) exposure could induce cell death and influence gene expression. Materials and Methods: In this study the authors assessed the effects of EMF (50 Hz, 70 G) on cytotoxicity, cell migration, gene expression, and protein levels in TMZ-treated T98 and A172 cell lines. Results: In this study, the authors show that treatment with a combination of TMZ and EMF enhanced cell death and decreased the migration potential of T98 and A172 cells. The authors also observed overexpression of the p53 gene and downregulation of cyclin-D1 protein in comparison to controls. In addition, T98 cells expressed the MGMT protein following treatment, while the A172 cells did not express MGMT. Conclusion: Their data indicate that EMF exposure improved the cytotoxicity of TMZ on T98 and A172 cells and could partially affect resistance to TMZ in T98 cells.

The Impact of Surgery in IDH 1 Wild Type Glioblastoma in Relation With the MGMT Deregulation

Object: The treatment of choice in glioblastoma (GBM) is the maximal surgical extent of resection (EOR) followed by adjuvant chemo-radiotherapy. Furthermore, methylguanine-DNA methyltransferase (MGMT) promoter methylation is associated with prolonged overall survival (OS) and progression free survival (PFS). The objective of the present study is correlate the biomolecular aspects in relation with EOR.

Materials and methods: We analyzed a series of 116 patients with IDH-1 wild type GBM and different EOR (Gross Total Resection—GTR-, Partial Resection—PR- and Biopsy), treated with adjuvant chemo-radiotherapy. The MGMT status was analyzed in terms of promoter methylation and protein expression.

Results: When GTR was possible, OS and PFS were significantly better compared to the other two groups (p = 0.001 and p = 0.035, respectively). MGMT methylation was significantly associated with better OS in the biopsy group (p = 0.022) and better OS and PFS in PR (p = 0.02 and p = 0.012, respectively), but not in the GTR group (p = 0.252 for OS, p = 0.256 for PFS) nor the PFS in the biopsy group (p = 0.259). MGMT protein expression levels do not show any association with OS and PFS, regardless of the type of surgery.

Conclusions: Our study confirms the positive association of a safe maximal EOR with better OS and PFS, and indicates a positive prognostic value of MGMT methylation status only in case of the presence of residual tumor tissue. MGMT protein expression seems not to play a clinical role in relation with the type of surgery.

Targeting the Sphingolipid System as a Therapeutic Direction for Glioblastoma

Glioblastoma (GBM) is the most commonly diagnosed malignant brain tumor in adults. The prognosis for patients with GBM remains poor and largely unchanged over the last 30 years, due to the limitations of existing therapies. Thus, new therapeutic approaches are desperately required. Sphingolipids are highly enriched in the brain, forming the structural components of cell membranes, and are major lipid constituents of the myelin sheaths of nerve axons, as well as playing critical roles in cell signaling. Indeed, a number of sphingolipids elicit a variety of cellular responses involved in the development and progression of GBM. Here, we discuss the role of sphingolipids in the pathobiology of GBM, and how targeting sphingolipid metabolism has emerged as a promising approach for the treatment of GBM.

Characterization of MGMT and EGFR protein expression in glioblastoma and association with survival

PURPOSE

Understanding the molecular landscape of glioblastoma (GBM) is increasingly important in the age of targeted therapy. O-6-Methylguanine-DNA methyltransferase (MGMT) promoter methylation and EGFR amplification are markers that may play a role in prognostication, treatment, and/or clinical trial eligibility. Quantification of MGMT and EGFR protein expression may offer an alternative strategy towards understanding GBM. Here, we quantify baseline expression of MGMT and EGFR protein in newly diagnosed GBM samples using mass spectrometry. We correlate findings with MGMT methylation and EGFR amplification statuses and survival.

METHODS

We retrospectively identified adult patients with newly diagnosed resected GBM. MGMT and EGFR protein expression were quantified using a selected reaction monitoring mass spectrometry assay. Protein levels were correlated with MGMT methylation and EGFR amplification and survival data.

RESULTS

We found a statistically significant association between MGMT protein expression and promoter methylation status (p = 0.02) as well as between EGFR protein expression and EGFR amplification (p < 0.0001). EGFR protein expression and amplification were more tightly associated than MGMT protein expression and methylation. Only MGMT promoter methylation was statistically significantly associated with progression-free and overall survival.

CONCLUSIONS

Unlike EGFR protein expression and EGFR amplification which are strongly associated, only a weak association was seen between MGMT protein expression and promoter methylation. Quantification of MGMT protein expression was inferior to MGMT methylation for prognostication in GBM. Discordance was observed between EGFR amplification and EGFR protein expression; additional study is warranted to determine whether EGFR protein expression is a better biomarker than EGFR amplification for clinical decisions and trial enrollment.

Prognostic significance of O6-methylguanine-DNA-methyltransferase (MGMT) promoter methylation and isocitrate dehydrogenase-1 (IDH-1) mutation in glioblastoma multiforme patients: A single-center experience in the Middle East region

OBJECTIVES

To determine the prevalence and prognostic value of MGMT promoter methylation and IDH1 mutation in glioblastoma multiforme (GBM) patients from the Middle East.

PATIENTS AND METHODS

Records of patients diagnosed between 2003 and 2015 were reviewed. MGMT promoter methylation was measured using methylation-specific polymerase chain reaction and IDH-1 mutation was reported. The primary endpoint was overall survival (OS).

RESULTS

A total of 110 patients were included. The median age was 51 years and 71 patients (64.5%) were males. The median diameter of GBM was 4.6 cm and 29 patients (26.4%) had multifocal disease. Gross total resection was achieved in 38 patients (24.9%). All patients received adjuvant radiation therapy, and 96 patients (91.4%) received concomitant temozolomide. At a median follow up of 13.6 months, the median OS was 17.2 months, and the OS at 1 and 2 years were 71.6% and 34.8%, respectively. On multivariate analysis, age at diagnosis (HR 1.019; P = 0.044) and multifocality (HR 2.373; P = 0.001) were the only independent prognostic variables. MGMT promoter methylation was found in 28.2% of patients but did not significantly correlate with survival (HR 1.160; P = 0.635). IDH-1 mutation was found in 10% of patients was associated with a non-significant trend for survival improvement (HR 0.502; P = 0.151).

CONCLUSION

Patients with GBM from the Middle East have adequate survival outcomes when given the optimal treatment. In our patient population, MGMT promoter methylation did not seem to correlate with outcomes, but patients with IDH1 mutation had numerically higher survival outcomes.

Outlining involvement of stem cell program in regulation of O6-methylguanine DNA methyltransferase and development of temozolomide resistance in glioblastoma: An Editorial Highlight for 'Transcriptional control of O6 -methylguanine DNA methyltransferase expression and temozolomide resistance in glioblastoma' on page 780

Glioblastoma is a malignant brain tumor that inevitably develops resistance to standard of care drug temozolomide (TMZ) due to a population of cells called cancer stem cells (CSCs). These cells utilize progenitor cell signaling programs and develop robust DNA repair machinery. In this editorial highlight we focus on stem cell regulation of TMZ resistance and discuss findings of Happold et al. () that outline direct transcriptional regulation of DNA repair enzyme O6-methylguanine DNA methyltransferase (MGMT) in glioblastoma CSCs through NFkB activation. The authors found that cells cultured in CSC propagating conditions exhibit increase in MGMT expression when compared to adherent differentiated monolayer cells. This in turn increases resistance to standard of care drug temozolomide (TMZ) in these cells. NFkB activation was found to directly activate expression of MGMT in sphere cultured GBM CSC.

Looking for A Place for Dose-Dense TMZ Regimens in GBM Patients: An Experience with MGMT Exploratory Evaluation

Prolonged exposure to temozolomide (TMZ) could improve clinical outcomes in recurrent glioblastoma multiforme (GBM) patients. We previously developed a dose-dense regimen of TMZ in a phase II study (180 mg/m² from days 1 to 5 every two weeks). A retrospective analysis of patients with macroscopic residual GBM treated with “post-induction” dose-dense TMZ was conducted, adding an explorative subgroup analyses among patients with different O⁶-methylguanine DNA methyltransferase (MGMT) expressions (negative vs positive, < vs ≥ of 50 % of cells stained, < vs ≥ 70% of cells stained). Thirty-six patients were evaluated; after a median follow-up of 36 weeks, median Progression Free Survival (PFS) and median Overall Survival (OS) were 19 and 34 weeks, respectively. MGMT expression (70% cut-off) and sex were confirmed as independent predictors for disease control rate (DCR) at multivariate analysis. At univariate analysis ECOG-PS, Sex (female), extensive tumor resection was shown to be related to a longer PFS, while MGMT expression (cut-off 70%) to a shorter PFS. Multivariate analysis with Cox hazard regression confirmed only ECOG-PS as an independent predictor for PFS. ECOG-PS showed to be significant related to a longer OS. Our analysis showed that dose-dense TMZ regimens are still an option for patients with recurrent GBM, but should be used for re-challenge treatments. MGMT immunohistochemistry high expression might be used as a “surrogate” negative predictor for DCR for dd-TMZ treatments.

MGMT: Immunohistochemical Detection in High-Grade Astrocytomas

Glioma therapeutic resistance to alkylating chemotherapy is mediated via O6-methylguanine-DNA methyltransferase (MGMT). We hypothesized that a CD45/HAM56/MGMT double-stained cocktail would improve MGMT discrimination in tumor cells versus inflammatory and endothelial cells (IEC). Total MGMT protein was quantified by IHC on 982 glioblastomas (GBM) and 199 anaplastic astrocytomas. Correcting for IEC was done by a CD45/HAM56/MGMT 2-color cocktail. Lowest IEC infiltrates (IEC "cold spots") were identified to quantitate MGMT as well as the percentage of IEC% in the IEC cold spots. MGMT promoter methylation (PM) was also determined. Among the GBM biopsies, mean uncorrected and corrected MGMT% were 19.87 (range 0-90) and 16.67; mean IEC% was 18.65 (range 1-80). Four hundred and fifty one (45.9%) GBM biopsies were positive MGMT PM. Both uncorrected and corrected MGMT% positivity correlated with PM. All 3 MGMT scores correlated with overall survival (OS) in GBM's. Cold spot IEC% was also positively associated with OS. These effects remained in a multivariate model after adjusting for age and disease status. Prognosis determined by correcting MGMT% score for IEC% is not improved in this analysis. However, IEC COLD SPOT score does provide additional prognostic information that can be gained from this correction method.

Real-time methylation-specific PCR for the evaluation of methylation status of MGMT gene in glioblastoma

The methylation status of the O6-methylguanine-DNA methyltransferase (MGMT) gene is a strong predictor for the efficacy of temozolomide chemotherapy and survival periods. However, the correlation between the extent of methylation and the difference in survival times has not been fully clarified. Simple and quantitative evaluations of the methylation status in the promotor region of the MGMT gene are expected to be worldwide standardized diagnostics. We applied real-time semi-quantitative methylation-specific polymerase chain reaction (SQ-MSP) of the MGMT gene promoter region to 84 glioblastoma patients. The SQ-MSP result showed that the ΔCt value, which represents the difference between uCt and mCt (uCt value – mCt value), is inversely correlated with overall survival. With adequate cutoff setting, this assay showed that those patients suffering from a tumor with low ΔCt (methylated) survived significantly longer than those having tumors with high ΔCt (un-methylated). The most significant difference was observed when the cutoff was set at a ΔCt of 2. Using this cutoff point, the result of MGMT immunohistochemical analysis was also significantly correlated with the methylation status examined with real-time SQ-MSP. These results collectively show that MGMT promoter methylation status actually affects patients’ survival and protein expression depending on its methylation level, and the extent of methylated CpGs would be better assessed with real-time SQ-MSP than with the standard gel-based MSP. This method is cost- and labor-saving compared with pyrosequencing, and significantly contributes to the accurate and objective prediction of patient survival.

Predicting O6-Methylguanine-DNA Methyltransferase Protein Expression in Primary Low- and High-Grade Gliomas Using Certain Qualitative Characteristics of Amide Proton Transfer-Weighted Magnetic Resonance Imaging

OBJECTIVE

To demonstrate that certain qualitative amide proton transfer-weighted (APTw) characteristics can provide practical imaging clues for predicting O6-methylguanine-DNA methyltransferase (MGMT) protein expression in primary low- and high-grade gliomas, preoperatively and noninvasively.

METHODS

Pathologically confirmed low- and high-grade gliomas with APT data and immunohistochemical (IHC) reports were recruited in this study. The MGMT protein expression status was classified by postsurgery specimen immunostaining. Subjects were divided into two groups, MGMT-positive and MGMT-negative group, according to the immunoreactivity of MGMT protein expression documented in IHC reports. APTw images scanned at 3T magnetic resonance preoperatively were retrospectively analyzed. Two neuroradiologists were trained to evaluate presence of certain APTw features. Kappa value was calculated to show the consistency between the 2 observers. The Mann-Whitney U test was used to evaluate relationships between the 2 groups on APTw features. Negative predictive value and positive predictive value was used to evaluate the ability of APTw characteristics in predicting MGMT protein expression. Receiver operating characteristic curve was used to evaluate the diagnostic performance of APTw characters. Two-tailed P < 0.05 was considered as statistically significant.

RESULTS

Forty-two subjects were recruited in this study. Among them 38 specimens presented positive MGMT immunostaining (MGMT-positive group), 4 specimens were negative MGMT immunostaing (MGMT-negative group). There were, respectively, 37 and 5 APTw images appeared positive and negative APTw features. Differences between tumors of positive and negative MGMT expression on qualitative APTw features were significant (P = 0.020). The consistency coefficient of the 2 observers was 0.876 (kappa = 0.876). Three of five llgliomas with negative APTw features showed MGMT-negative immunostaining, leading to a negative predictive value of 60%, and 36 of 37 cases presenting positive APTw characteristics were tumors of MGMT-positive expression, generating a positive predictive value of 97.3%. The area under curve was 0.849.

CONCLUSIONS

APTw characteristics could be promising imaging markers by which to predict IHC MGMT expression in primary low- and high-grade gliomas preoperatively and noninvasively.

MicroRNA-142-3p is involved in regulation of MGMT expression in glioblastoma cells

Background

Glioblastoma multiforme (GBM) is the most malignant brain tumor, and there is no effective treatment strategy. Patients with GBM have a median overall survival of only 14.6 months. Current treatment consists of safe and maximal surgical excision, followed by concurrent chemoradiotherapy and maintenance chemotherapy. There are several obstacles that hinder the effectiveness of this aggressive treatment. Temozolomide (TMZ) is an oral alkylating drug that acts through alkylating the O⁶ position of guanine in DNA that leads to cell death. However, the expression and enzymatic activity of the DNA repair protein MGMT limits the therapeutic benefit from treatment with TMZ. MGMT reduces the efficacy of alkylating drugs by removing the methyl or alkyl group from damaged O⁶-methylguanine. Expression levels of MGMT play an important role in the outcome of GBM patients. miRNAs are a group of small regulatory RNAs that control target gene expression by binding to mRNAs. miR-142-3p has been found to be an important factor in the development and maintenance of the oncogenic state.

Results

In this study, we sought to investigate whether miR-142-3p can regulate MGMT gene expression in GBM cells. Here, we show that miR-142-3p downregulates MGMT expression through binding to the 3′-UTR of MGMT mRNA, thus affecting protein translation. Responsiveness to TMZ was significantly enhanced after transfection with miR-142-3p. Overexpression of miR-142-3p also sensitized GBM cells to alkylating drugs.

Conclusion

Above all, our findings demonstrate that miR-142-3p plays a critical role in regulating MGMT expression, has great potential for future clinical applications, and acts as a new diagnostic marker for this intractable disease.

Immunohistochemical Features of O6-Methylguanine-DNA Methyltransferase Expression during Ovarian Endometriosis

A comparative immunohistochemical study for the expression of O6-methylguanine-DNA methyltransferase (MGMT) was performed in tissues of the eutopic endometrium and ovarian endometriosis. The highest level of MGMT expression in eutopic endometrial tissue was observed in epitheliocyte nuclei during the proliferative phase. In regions of endometriosis the expression of MGMT in epitheliocyte nuclei was shown to increase during stages I and II, but decreased in stages III and IV. The progression of endometriosis was accompanied by a gradual increase of study parameters in the nuclei and cytoplasm of stromal cells. These changes reflect the impairment of DNA reparation, which probably serves as a stage in the development and progression of endometriosis.

A comparison between oral chemotherapy combined with radiotherapy and radiotherapy for newly diagnosed glioblastoma: A systematic review and meta-analysis

The prognosis of glioblastoma (GBM), a major subtype of grade IV glioma, is rather poor nowadays. The efficiency of chemotherapy serving as the adjunct to radiotherapy (RT) for treating GBM is still controversial. In this study, we aim to investigate the overall survival (OS) and progression-free survival (PFS) in patients with newly diagnosed GBM received RT plus chemotherapy or with RT alone.Literatures were searched from the PubMed, Embase, and Cochrane Library between January 2001 and June 2015. Study selection was conducted based on the following criteria: randomized clinical trial (RCT) of adjuvant RT plus chemotherapy versus RT alone; studies comparing OS and/or PFS; and studies including cases medically confirmed of newly diagnosed GBM.Five RCTs (1655 patients) were eligible in this study. The meta-analysis showed a significant improvement in OS of patients treated with RT plus oral chemotherapy compared with that of RT alone (hazard ratio 0.70; 95% confidence interval, 0.56-0.88, P = .002).Adjuvant chemotherapy confers a survival benefit in patients newly diagnosed with GBM.

Dose-Dense Temozolomide in Patients with MGMT-Silenced Chemorefractory Colorectal Cancer

BACKGROUND

In a phase II study, we showed that temozolomide (TMZ) was tolerable and active in heavily pre-treated patients with advanced colorectal cancer (CRC) and MGMT methylation. A schedule of dose-dense TMZ may have enhanced activity due to the higher cumulative dose and induction of MGMT depletion, even in resistant tumors.

METHODS

Thirty-two patients with chemorefractory MGMT-methylated CRC were treated with TMZ at a daily dose of 75 mg/m(2) for 21 consecutive days every 4 weeks, for up to six cycles or until the occurrence of progressive disease/unacceptable toxicity. The primary endpoint was treatment activity in terms of objective response rate (ORR). MGMT protein expression was tested by immunohistochemistry (IHC) on two pooled cohorts: patients from the previous study of standard-dose TMZ and those from the current investigation.

RESULTS

From November 2013 to December 2014, 32 patients were treated at Fondazione IRCCS Istituto Nazionale dei Tumori. We observed only three episodes of grade 3 asthenia and no significant myelotoxicity. The ORR was 16 % (all partial responses occurring in RAS-BRAF-mutated tumors). Median progression-free survival (PFS) and overall survival (OS) were 2.3 and 6.7 months, respectively. Patients with MGMT-low expression by IHC had a significantly higher ORR (p < 0.0001) and PFS (p = 0.001) compared to those with MGMT-high expression, while no difference was observed in OS.

CONCLUSIONS

Our data confirm the encouraging activity of TMZ in chemorefractory CRC patients selected for MGMT silencing, even in the RAS-BRAF-mutated population. The role of MGMT IHC as a biomarker for improving patient selection warrants further prospective confirmation.

Is the prognostic significance of O6-methylguanine- DNA methyltransferase promoter methylation equally important in glioblastomas of patients from different continents? A systematic review with meta-analysis

BACKGROUND

O6-methylguanine-DNA methyltransferase (MGMT) is an independent predictor of therapeutic response and potential prognosis in patients with glioblastoma multiforme (GBM). However, its significance of clinical prognosis in different continents still needs to be explored.

PATIENTS AND METHODS

To explore the effects of MGMT promoter methylation on both progression-free survival (PFS) and overall survival (OS) among GBM patients from different continents, a systematic review of published studies was conducted.

RESULTS

A total of 5103 patients from 53 studies were involved in the systematic review and the total percentage of MGMT promoter methylation was 45.53%. Of these studies, 16 studies performed univariate analyses and 17 performed multivariate analyses of MGMT promoter methylation on PFS. The pooled hazard ratio (HR) estimated for PFS was 0.55 (95% CI 0.50, 0.60) by univariate analysis and 0.43 (95% CI 0.38, 0.48) by multivariate analysis. The effect of MGMT promoter methylation on OS was explored in 30 studies by univariate analysis and in 30 studies by multivariate analysis. The combined HR was 0.48 (95% CI 0.44, 0.52) and 0.42 (95% CI 0.38, 0.45), respectively.

CONCLUSION

In each subgroup divided by areas, the prognostic significance still remained highly significant. The proportion of methylation in each group was in inverse proportion to the corresponding HR in the univariate and multivariate analyses of PFS. However, from the perspective of OS, compared with data from Europe and the US, higher methylation rates in Asia did not bring better returns.

PIK3R1Met326Ile germline mutation correlates with cysteine-rich protein 61 expression and poor prognosis in glioblastoma

Despite therapeutic advances, glioblastoma represents a lethal brain tumor. Recently, research to identify prognostic markers for glioblastoma has intensified. Our previous study demonstrated that median progression-free survival (PFS) and overall survival (OS) of patients with high cysteine-rich protein 61 (CCN1) expression was significantly shorter than that of patients with low CCN1 expression. To understand the molecular mechanisms that regulate CCN1 expression, we examined 147 tumour samples from 80 patients with glioblastoma and 67 patients with lower grade glioma. Next-generation and Sanger sequencing showed that PIK3R1Met326Ile was more frequent in the CCN1 high expression group (10/37 cases, 27.0%) than the CCN1 low expression group (3/38 cases, 7.9%) in glioblastoma. This mutation was also detected in corresponding blood samples. In multivariate analysis, high CCN1 expression and PIK3R1Met326Ile in glioblastoma patients were prognostic factors for OS [HR = 2.488 (1.298–4.769), p = 0.006] and [HR = 2.089 (1.020–4.277), p = 0.0439], respectively. Thus, the PIK3R1Met326Ile germline appears to be correlated with CCN1 expression and poor prognosis in glioblastoma.

Outcome evaluation of patients with newly diagnosed anaplastic gliomas treated in a single institution

AIM

To evaluate the outcome of newly diagnosed anaplastic glioma patients treated in our institution in relation to the 2016 WHO classification suggestions.

METHODS

This retrospective study included patients who underwent surgery plus adjuvant chemotherapy alone or concomitant and adjuvant chemoradiotherapy. Response was recorded using the Response Assessment in Neuro-Oncology criteria.

RESULTS

123 patients were analyzed. The median progression-free survival time and the 2, 3 and 5 years progression-free survival rate were 27 months, 65.5, 21.2 and 21.2%; the 2, 3 and 5 years overall survival rate were 89.7, 83.0 and 58.4%. From the univariate/multivariate analysis, the factors conditioning survival were Karnofsky performance scale, extent of resection, IDH1 mutation status and presence of 1p/19q codeletion.

CONCLUSION

The choice of adjuvant treatment have to consider molecular assessment and, in our experience, the extent of surgical resection.

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.

MRI during radiotherapy of glioblastoma : Does MRI allow for prognostic stratification?

AIM

To evaluate the role of magnetic resonance imaging (MRI) as a predictor for the clinical course in patients with glioblastoma.

PATIENTS AND METHODS

In 64 patients with glioblastoma undergoing (chemo)radiotherapy MRI studies were obtained before radiation, after 30 gray (Gy), after 60 Gy and during follow-up. MRI findings were assigned to categories: definite progression, questionable progression, no change. Patients were followed clinically.

RESULTS

At 30 Gy, 23 of 64 patients (36 %) demonstrated definite (dp; n = 15) or questionable (qp; n = 8) progression; in 41/64 (64 %) no change was found compared with preradiation MRI. After radiotherapy at 60 Gy, 26 of 64 (41 %) patients showed dp (n = 18) or qp (n = 8). In 2 cases with qp at the 30 Gy MRI, progress was unquestionable in the 60 Gy MRI study. In the 64 patients, 5 of the 60 Gy MRIs showed dp/qp after being classified as no change at the 30 Gy MRI, 2 of the 30 Gy MRIs showed qp, while the 60 Gy MRI showed tumour regression and 3 fulfilled the criteria for pseudoprogression during ongoing radiotherapy. The 30 Gy study allowed for prognostic stratification: dp/qp compared to stable patients showed median survival of 10.5 versus 20 months.

CONCLUSION

MR follow-up after 30 Gy in patients undergoing (chemo)radiotherapy for glioblastoma allows prognostic appraisal. Pseudoprogression has to be taken into account, though rare in our setting. Based on these findings, early discussion of treatment modification is possible.

Evaluation of extracellular matrix protein CCN1 as a prognostic factor for glioblastoma

Recently, research efforts in identifying prognostic molecular biomarkers for malignant glioma have intensified. Cysteine-rich protein 61 (CCN1) is one of the CCN family of matricellular proteins that promotes cell growth and angiogenesis in cancers through its interaction with several integrins. In this study, we investigated the relationships among CCN1, O(6)-methylguanine-DNA methyltransferase expression, the tumor removal rate, and prognosis in 46 glioblastoma patients treated at the Okayama University Hospital. CCN1 expression was high in 31 (67 %) of these patients. The median progression-free survival (PFS) and overall survival (OS) times of patients with high CCN1 expression was significantly shorter than those of patients with low CCN1 expression (p < 0.005). In a multivariate Cox analysis, CCN1 proved to be an independent prognostic factor for patient survival [PFS, hazard ratio (HR) = 3.53 (1.55-8.01), p = 0.003 and OS, HR = 3.05 (1.35-6.87), p = 0.007]. Moreover, in the 31 patients who underwent gross total resection, the PFS and OS times of those with high CCN1 expression were significantly shorter than those with low CCN1 expression. It was concluded that CCN1 might emerge as a significant prognostic factor regarding the prognosis of glioblastoma patients.

Novel approaches for quantifying protein biomarkers in gliomas: benefits and pitfalls

The therapeutic paradigm of gliomas is changing from a general approach towards an individualized and targeted approach. Accordingly, the search for prognostic and predictive biomarkers, as well as the demand for quantitative, feasible and robust methods for biomarker analysis increases. We find that software classifiers can identify and quantify the expression of a given biomarker within different subcellular compartments and that such classifiers can exclude frequently occurring nontumor cells, thereby avoiding potential bias. The use of a quantitative approach provides a continuous measurement of the expression, allowing establishment of new cut-points and identification of patients with specific prognoses. However, some pitfalls must be noted. This article focuses on benefits and pitfalls of novel approaches for quantifying protein biomarkers in gliomas.

Regulation of expression of O6-methylguanine-DNA methyltransferase and the treatment of glioblastoma (Review)

O-6-methylguanine-DNA methyltransferase (MGMT) is an abundantly expressed nuclear protein dealkylating O⁶-methylguanine (O⁶-MG) DNA residue, thus correcting the mismatches of O⁶-MG with a thymine residue during DNA replication. The dealkylating effect of MGMT is relevant not only in repairing DNA mismatches produced by environmental alkylating agents promoting tumor pathogenesis, but also when alkylating molecules are applied in the chemotherapy of different cancers, including glioma, the most common primary tumor of the central nervous system. Elevated MGMT gene expression is known to confer resistance to the treatment with the alkylating drug temozolomide in patients affected by gliomas and, on the contrary, methylation of MGMT gene promoter, which causes reduction of MGMT protein expression, is known to predict a favourable response to temozolomide. Thus, detecting expression levels of MGMT gene is crucial to indicate the option of alkylating agents or to select patients directly for a second line targeted therapy. Further study is required to gain insights into MGMT expression regulation, that has attracted growing interest recently in MGMT promoter methylation, histone acetylation and microRNAs expression. The review will focus on the epigenetic regulation of MGMT gene, with translational applications to the identification of biomarkers predicting response to therapy and prognosis.

Biomarker-driven diagnosis of diffuse gliomas

The diffuse gliomas are primary central nervous system tumors that arise most frequently in the cerebral hemispheres of adults. They are currently classified as astrocytomas, oligodendrogliomas or oligoastrocytomas and range in grade from II to IV. Glioblastoma (GBM), grade IV, is the highest grade and most common form. The diagnosis of diffuse gliomas has historically been based primarily on histopathologic features, yet these tumors have a wide range of biological behaviors that are only partially explained by morphology. Biomarkers have now become an established component of the neuropathologic diagnosis of gliomas, since molecular alterations aid in classification, prognostication and prediction of therapeutic response. Isocitrate dehydrogenase (IDH) mutations are frequent in grades II and III infiltrating gliomas of adults, as well as secondary GBMs, and are a major discriminate of biologic class. IDH mutant infiltrating astrocytomas (grades II and III), as well as secondary GBMs, are characterized by TP53 and ATRX mutations. Oligodendrogliomas are also IDH mutant, but instead are characterized by 1p/19q co-deletion and mutations of CIC, FUBP1, Notch1 and the TERT promoter. Primary GBMs typically lack IDH mutations and demonstrate EGFR, PTEN, TP53, PDGFRA, NF1 and CDKN2A/B alterations and TERT promoter mutations. Pediatric gliomas differ in their spectrum of disease from those in adults; high grade gliomas occurring in children frequently have mutations in H3F3A, ATRX and DAXX, but not IDH. Circumscribed, low grade gliomas, such as pilocytic astrocytoma, pleomorphic xanthoastrocytoma and ganglioglioma, need to be distinguished from diffuse gliomas in the pediatric population. These gliomas often harbor mutations or activating gene rearrangements in BRAF.

Molecular genetics of gliomas

Diffusely infiltrating gliomas are the most common primary brain tumors and include astrocytomas, oligodendrogliomas, and oligoastrocytomas of grades II and III and glioblastoma (GBM), grade IV. Histologic classification is increasingly aided by molecular genetic studies, which assist in the diagnosis and provide prognostic and predictive value. Mutations in IDH1 are frequent in grades II and III astrocytomas, oligodendrogliomas, and oligoastrocytomas, as well as secondary GBMs. IDH1-mutated diffuse gliomas are distinct from their IDH1 wild-type counterparts based on clinical features, growth rates, and concurrent genomic alterations. Grades II and III astrocytomas, as well as secondary GBMs are characterized by IDH1, TP53, and ATRX mutations, whereas oligodendrogliomas most frequently harbor codeletion of 1p/19q and mutations in CIC, FUBP1, and the TERT promoter. Primary GBMs frequently show molecular alterations in EGFR, PDGFRA, PTEN, TP53, NF1, and CDKN2A/B, as well as TERT promoter mutations, but not IDH mutations. Pediatric GBMs have a distinctive molecular pathogenesis, as H3F3A and DAXX mutations are frequent, and their gene expression profile is different than adult GBMs. Other lower-grade gliomas of childhood, such as pilocytic astrocytoma and pleomorphic xanthoastrocytoma, are characterized by BRAF mutations or activating gene rearrangements involving BRAF.

Decitabine nanoconjugate sensitizes human glioblastoma cells to temozolomide

In this study, we developed and characterized a delivery system for the epigenetic demethylating drug, decitabine, to sensitize temozolomide-resistant human glioblastoma multiforme (GBM) cells to alkylating chemotherapy. A poly(lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) based nanoconjugate was fabricated to encapsulate decitabine and achieved a better therapeutic response in GBM cells than that with the free drug. After synthesis, the highly efficient uptake process and intracellular dynamics of this nanoconjugate were monitored by single-molecule fluorescence tools. Our experiments demonstrated that, under an acidic pH due to active glycolysis in cancer cells, the PLGA-PEG nanovector could release the conjugated decitabine at a faster rate, after which the hydrolyzed lactic acid and glycolic acid would further acidify the intracellular microenvironment, thus providing positive feedback to increase the effective drug concentration and realize growth inhibition. In temozolomide-resistant GBM cells, decitabine can potentiate the cytotoxic DNA alkylation by counteracting cytosine methylation and reactivating tumor suppressor genes, such as p53 and p21. Owing to the excellent internalization and endolysosomal escape enabled by the PLGA-PEG backbone, the encapsulated decitabine exhibited a better anti-GBM potential than that of free drug molecules. Hence, the synthesized nanoconjugate and temozolomide could act in synergy to deliver a more potent and long-term antiproliferative effect against malignant GBM cells.

Clinicopathological significance and potential drug target of O6-methylguanine-DNA methyltransferase in colorectal cancer: a meta-analysis

Emerging evidence indicates that O(6)-methylguanine-DNA methyltransferase (MGMT) is a candidate for tumor suppression in several types of human tumors including colorectal cancer (CRC). However, the correlation between MGMT hypermethylation and clinicopathological characteristics of CRC remains unclear. In this study, we conducted a systematic review and meta-analysis to quantitatively evaluate the effects of MGMT hypermethylation on the incidence of CRC and clinicopathological characteristics. A comprehensive literature search was done from Web of Science, the Cochrane Library Database, PubMed, EMBASE, CINAHL, and the Chinese Biomedical Database for related research publications written in English and Chinese. Methodological quality of the studies was also evaluated. Analyses of pooled data were performed with Review Manager 5.2. Odds ratio (OR) and hazard ratio (HR) were calculated and summarized, respectively. Final analysis from 28 eligible studies was performed. MGMT hypermethylation is found to be significantly higher in CRC than in normal colorectal mucosa, the pooled OR from 13 studies including 1085 CRC and 899 normal colorectal mucosa, OR = 6.04, 95 % confidence interval (CI) = 4.69-7.77, p < 0.00001. MGMT hypermethylation is also significantly higher in colorectal adenoma than in normal colorectal mucosa, but it is significantly less compared to that in CRC patients. Interestingly, MGMT hypermethylation is correlated with sex status and is significantly higher in female than in male. MGMT hypermethylation is also associated with high levels of microsatellite instability (MSI). The pooled HR for overall survival (OS) shows that MGMT hypermethylation is not associated with worse survival in CRC patients. The results of this meta-analysis suggest that MGMT hypermethylation is associated with an increased risk and high levels of MSI and may play an important role in CRC initiation. However, MGMT hypermethylation may play an important role in the early stage of CRC progression and development, as well as having limited value in prediction of prognosis in CRC patients. We also discussed that MGMT may serve as a potential drug target of CRC.

The future of high-grade glioma: Where we are and where are we going

High-grade glioma (HGG) are optimally treated with maximum safe surgery, followed by radiotherapy (RT) and/or systemic chemotherapy (CT). Recently, the treatment of newly diagnosed anaplastic glioma (AG) has changed, particularly in patients with 1p19q codeleted tumors. Results of trials currenlty ongoing are likely to determine the best standard of care for patients with noncodeleted AG tumors. Trials in AG illustrate the importance of molecular characterization, which are germane to both prognosis and treatment. In contrast, efforts to improve the current standard of care of newly diagnosed glioblastoma (GB) with, for example, the addition of bevacizumab (BEV), have been largely disappointing and furthermore molecular characterization has not changed therapy except in elderly patients. Novel approaches, such as vaccine-based immunotherapy, for newly diagnosed GB are currently being pursued in multiple clinical trials. Recurrent disease, an event inevitable in nearly all patients with HGG, continues to be a challenge. Both recurrent GB and AG are managed in similar manner and when feasible re-resection is often suggested notwithstanding limited data to suggest benefit from repeat surgery. Occassional patients may be candidates for re-irradiation but again there is a paucity of data to commend this therapy and only a minority of selected patients are eligible for this approach. Consequently systemic therapy continues to be the most often utilized treatment in recurrent HGG. Choice of therapy, however, varies and revolves around re-challenge with temozolomide (TMZ), use of a nitrosourea (most often lomustine; CCNU) or BEV, the most frequently used angiogenic inhibitor. Nevertheless, no clear standard recommendation regarding the prefered agent or combination of agents is avaliable. Prognosis after progression of a HGG remains poor, with an unmet need to improve therapy.

The potential for epigenetic analysis of paediatric CNS tumours to improve diagnosis, treatment and prognosis

Tumours of central nervous system (CNS) origin are the second most prevalent group of cancers in children, yet account for the majority of childhood cancer-related deaths. Such tumours show diverse location, cell type of origin, disease course and long-term outcome, both across and within tumour types, making treatment problematic and contributing to the relatively modest progress in reducing mortality over recent decades. As technological advances begin to reveal the genetic landscape of all cancers, it is becoming increasingly clear that genetic disruption represents only one 'layer' of molecular disruption associated with disease aetiology. Obtaining a full understanding of tumour behaviour requires an understanding of the cellular and molecular pathways disrupted during tumourigenesis, particularly in relation to gene expression. The utility of such an approach has allowed stratification of cancers such as medulloblastoma into subgroups based on molecular features, with potential to refine risk prediction. Given that epigenetic disruption is a universal feature of all human cancers, it is logical to speculate that interrogating epigenetic marks may help to further define the molecular profile, and therefore the clinical trajectory, of tumours. An integrated approach to build a molecular 'signature' of individual tumours that incorporates traditional morphological and demographic information, genetic and transcriptome analysis, in addition to epigenomics (DNA methylation and non-coding RNA analysis), offers tremendous promise to (i) inform treatment approach, (ii) facilitate accurate early identification (preferably at diagnosis) of variable risk groups (both good and poor prognosis groups), and (iii) track disease progression in childhood CNS tumours.

Prognostic value of MGMT methylation in colorectal cancer: a meta-analysis and literature review

The development of colorectal cancer (CRC) spans about 5-10 years, making early detection and prevention beneficial to the survival of CRC patients. To address inconsistencies in evidence regarding O(6)-methylguanine-DNA-methyltransferase (MGMT) methylation as a potential prognostic factor in CRC, we conducted a meta-analysis to evaluate MGMT methylation in CRC patients. Fourteen studies were included in the meta-analysis after screening 120 articles. The following items were collected from each study: author, published year, country, patient gender, MGMT methylation status, and patients' disease progression. Pooled hazard ratios and odd ratios with 95% confidence intervals (CIs) were calculated using fixed or random effect models depending on the heterogeneity between studies. The overall survival of CRC patients was found not to be significantly associated with MGMT methylation. Further subgroup analysis showed that the frequency of MGMT methylation was significantly higher in CRC than in normal tissues (p < 0.00001). MGMT promoter in CRC patients was more frequently methylated than in adenoma patients. In addition, MGMT methylation was significantly increased in adenoma than in normal tissues (p < 0.0001). In conclusion, MGMT methylation is central to the development of cancer that involves a stepwise carcinogenesis of normal adenoma carcinoma cascade. However, MGMT methylation is not associated with the prognosis of CRC.

Molecular pathways in gliomagenesis and their relevance to neuropathologic diagnosis

Gliomas are a large and diverse group of primary brain tumors that include those that are diffusely infiltrative and others that are well-circumscribed and low grade. Diffuse gliomas are currently classified by the World Health Organization as astrocytomas, oligodendrogliomas, or oligoastrocytomas and range in grade from II to IV. Glioblastoma (GBM), World Health Organization grade IV, is the highest grade and most common form of astrocytoma. In the past, the diagnosis of gliomas was almost exclusively based on histopathologic features. More recently, improved understanding of molecular genetic underpinnings has led to ancillary molecular studies becoming standard for classification, prognostication, and predicting therapy response. Isocitrate dehydrogenase (IDH) mutations are frequent in grade II and III infiltrating gliomas and secondary GBMs. Infiltrating astrocytomas and secondary GBMs are characterized by IDH, TP53, and ATRX mutations, whereas oligodendrogliomas demonstrate 1p/19q codeletion and mutations in IDH, CIC, FUBP1, and the telomerase reverse transcriptase (TERT) promoter. Primary GBMs typically lack IDH mutations and are instead characterized by EGFR, PTEN, TP53, PDGFRA, NF1, and CDKN2A/B alterations and TERT promoter mutations. Pediatric GBMs differ from those in adults and frequently have mutations in H3F3A, ATRX, and DAXX, but not IDH. In contrast, circumscribed, low-grade gliomas of childhood, such as pilocytic astrocytoma, pleomorphic xanthoastrocytoma, and ganglioglioma, often harbor mutations or activating gene rearrangements in BRAF. Neuropathologic assessment of gliomas increasingly relies on ancillary testing of molecular alterations for proper classification and patient management.

The prognosis of MGMT promoter methylation in glioblastoma patients of different race: a meta-analysis

O(6)-Methylguanine-DNA methyltransferase (MGMT) is a DNA repair gene. Epigenetic silencing of the MGMT promoter methylation compromises DNA repair and has been associated with longer survival in patients with glioblastoma (GBM) who receive alkylating agents. But the prognostic of MGMT promoter methylation in GBM patients of different race is still ambiguous. Based on an univariate or multivariate analysis between different race (Caucasian and Asian), a meta-analysis of the effects of MGMT promoter methylation on both progression-free survival (PFS) and overall survival (OS) among GBM patients was conducted. A total of 6,309 patients from 50 studies were involved in the analysis. Random effect models were applied to estimate the pooled hazard ratio (HR) with 95 % confidence intervals (CIs) for GBM patients of different race prognosis, the Chi square-based Q test was used to test heterogeneity. Begg's (funnel plot method) and Egger's linear regression tests were adopted to check publication bias (a bias with regard to what is likely to be published, among what is available to be published). The HR value estimated for OS was 0.524 (95 % CI 0.428-0.640) by univariate analysis and 0.427 (95 % CI 0.355-0.513) by multivariate analysis in Caucasian. The HR value estimated for OS was 0.892 (95 % CI 0.469-1.698) by univariate analysis and 0.562 (95 % CI 0.394-0.804) by multivariate analysis in Asian. The HR value estimated for PFS was 0.526 (95 % CI 0.372-0.743) by univariate analysis and 0.437 (95 % CI 0.356-0.537) by multivariate analysis in Caucasian. The HR value estimated for PFS was 0.132 (95 % CI 0.006-3.027) by multivariate analysis in Asian. This data revealed that GBM patients with MGMT promoter methylation had longer OS and PFS by univariate or multivariate analysis in Caucasian regardless of therapeutic intervention. However, GBM patients with MGMT promoter methylation only had longer OS by multivariate analysis in Asian.

MGMT promoter methylation and correlation with protein expression in primary central nervous system lymphoma

The O (6)-methylguanine-DNA-methyltransferase (MGMT) gene encodes for a DNA repairing enzyme of which silencing by promoter methylation is involved in brain tumorigenesis. MGMT promoter methylation represents a favorable prognostic factor and has been associated with a better response to alkylating agents in glioma and systemic lymphoma. Primary central nervous system lymphoma (PCNSL) is a rare and aggressive extranodal malignant lymphoma. The current standard of care, based on high-dose methotrexate chemotherapy, has improved prognosis but outcome remains poor for a majority of patients. Therapeutic progress in this field is conditioned by limited biological and molecular knowledge about the disease. Temozolomide has recently emerged as an alternative option for PCNSL treatment. We aimed to analyze the MGMT gene methylation status in a series of 24 PCNSLs, to investigate the relationship between methylation status of the gene and immunohistochemical expression of MGMT protein and to evaluate the possible prognostic significance of these biomarkers. Our results confirm that methylation of the MGMT gene and loss of MGMT protein are frequent events in these lymphomas (54 % of our cases) and suggest that they are gender and age related. MGMT methylation showed high correlation with loss of protein expression (concordance correlation coefficient = -0.49; Fisher exact test: p < 0.01), different from what has been observed in other brain tumors. In the subgroup of ten patients who received high dose chemotherapy, the presence of methylated MGMT promoter (n = 4), seems to be associated with a prolonged overall survival (>60 months in three of four patients). The prognostic significance of these molecular markers in PCNSL needs to be further studied in groups of patients treated in a homogeneous way.

The prognostic value of MGMT promoter methylation in Glioblastoma multiforme: a meta-analysis

The prognostic significance of O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation on Glioblastoma multiforme (GBM) remains controversial. A meta-analysis of published studies investigating the effects of MGMT promoter methylation on both progression-free survival (PFS) and overall survival (OS) among GBM patients was performed. A total of 2,986 patients from 30 studies were included in the meta-analysis. In all, the frequency of MGMT promoter methylation was 44.27 %. Five studies undertook univariate analyses and nine undertook multivariate analyses of MGMT promoter methylation on PFS. The pooled hazard ratio (HR) estimate for PFS was 0.72 (95 % CI 0.55-0.95) by univariate analysis and 0.51 (95 % CI 0.38-0.69) by multivariate analysis. The effect of MGMT promoter methylation on OS was evaluated in 15 studies by univariate analysis and 14 studies by multivariate analysis. The combined HR was 0.67 (95 % CI 0.58-0.78) and 0.49 (95 % CI 0.38-0.64), respectively. For GBM patients treated with Alkylating agent, the meta-risk remained highly significant by both univariate (HR = 0.58; 95 % CI 0.42-0.79) and multivariate analysis (HR = 0.42; 95 % CI 0.29-0.60). This study showed that MGMT promoter methylation was associated with better PFS and OS in patients with GBM regardless of therapeutic intervention, and associated with longer OS in GBM patients treated with alkylating agents.

The role of gene body cytosine modifications in MGMT expression and sensitivity to temozolomide

The DNA repair protein O(6)-methylguanine-DNA methyltransferase (MGMT) is known to play a role in sensitivity to temozolomide. Promoter hypermethylation of MGMT is commonly used to predict low expression levels of MGMT in gliomas, despite observed discordance between promoter methylation and protein levels. Here, we investigated the functional role of gene body cytosine modification in regulating levels of MGMT gene expression and sensitivity to temozolomide. In 91 human glioblastoma samples, we observed significant variation in MGMT expression levels in patients with an unmethylated promoter, with higher levels of gene body cytosine modification correlating with higher gene expression levels. Furthermore, inducing hypomethylation across the MGMT gene body with decitabine corresponded with decreased levels of MGMT gene expression in lymphoblastoid and glioblastoma cell lines, indicating an important functional role for gene body cytosine modifications in maintaining gene expression. We reasoned that the decrease in MGMT expression induced by decitabine may render resistant glioblastoma cell lines more sensitive to temozolomide. Consistent with this reasoning, we found that the MGMT-expressing glioblastoma cell lines exhibiting an unmethylated MGMT promoter that were pretreated with decitabine became significantly more sensitive to temozolomide. Overall, our results suggest a functional role for gene body cytosine modification in regulating gene expression of MGMT and indicate that pretreating patients whose tumors have an unmethylated MGMT promoter with decitabine before temozolomide treatment may increase their response to therapy.

Meningeal hemangiopericytomas: a clinicopathological study with emphasis on MGMT (O(6) -methylguanine-DNA methyltransferase) promoter methylation status

Meningeal hemangiopericytomas (HPCs) are aggressive dural-based tumors, for which no prognostic or predictive marker has been identified. Gross total resection is treatment of choice, but not easily achieved; hence, alkylating agents like temozolomide (TMZ) are now being tried. O(6) -methylguanine-DNA methyltransferase (MGMT) promoter methylation has proven prognostic and predictive value in glioblastomas. This study evaluates MGMT promoter methylation in meningeal HPCs to determine its role in HPC oncogenesis and its association with patient outcome. Meningeal HPCs diagnosed between 2002 and 2011 were retrieved and clinicopathological features reviewed. MGMT promoter methylation status was assessed by methylation-specific polymerase chain reaction (MSP) and immunohistochemistry (IHC) for MGMT protein. HPCs accounted for 1.1% of all CNS tumors. Forty cases were analyzed; the majority were adults (mean age = 41.4 years). Seventy percent were primary and 30% were recurrent tumors; 60% were grade II and 40% were grade III. MGMT promoter methylation was identified in 45% of cases, including Grade II (54.2%) and Grade III (31.3%) (P = 0.203). Promoter methylation was significantly (P = 0.035) more frequent in primary (57.1%) than in recurrent (16.7%) tumors. No correlation was noted between MGMT promoter methylation by MSP and MGMT protein expression by IHC, or with progression-free survival. Thus, a significant proportion of HPCs demonstrate MGMT promoter methylation, suggesting possible susceptibility to TMZ. As promoter methylation is more frequent in primary tumors, TMZ may serve as a therapeutic option in residual primary tumors. Epigenetic inactivation of MGMT in HPCs necessitates the assessment of prognostic and predictive value of MGMT promoter methylation in HPCs in larger clinical trials.

Prognostic and predictive roles of MGMT protein expression and promoter methylation in sporadic pancreatic neuroendocrine neoplasms

BACKGROUND/AIMS

O(6)-methylguanine-methyltransferase (MGMT) is an important enzyme of DNA repair. MGMT promoter methylation is detectable in a subset of pancreatic neuroendocrine neoplasms (pNEN). A subset of pNEN responds to the alkylating agent temozolomide (TMZ). We wanted to correlate MGMT promoter methylation with MGMT protein loss in pNEN, correlate the findings with clinico-pathological data and determine the role of MGMT to predict response to TMZ chemotherapy.

METHODS

We analysed a well-characterized collective of 141 resected pNEN with median follow-up of 83 months for MGMT protein expression and promoter methylation using methylation-specific PCR (MSP). A second collective of 10 metastasized, pretreated and progressive patients receiving TMZ was used to examine the predictive role of MGMT by determining protein expression and promoter methylation using primer extension-based quantitative PCR.

RESULTS

In both collectives there was no correlation between MGMT protein expression and promoter methylation. Loss of MGMT protein was associated with an adverse outcome, this prognostic value, however, was not independent from grade and stage in multivariate analysis. Promoter hypermethylation was significantly associated with response to TMZ.

CONCLUSION

Loss of MGMT protein expression is associated with adverse outcome in a surgical series of pNET. MGMT promoter methylation could be a predictive marker for TMZ chemotherapy in pNEN, but further, favourably prospective studies will be needed to confirm this result and before this observation can influence clinical routine.

Prognostic value of O-6-methylguanine-DNA methyltransferase loss in salivary gland carcinomas

BACKGROUND

The purpose of this study was to determine the prognostic value of O-6-methylguanine-DNA methyltransferase (MGMT) inactivation in a group of 286 patients with salivary gland carcinoma and matched histologically normal tissues.

METHODS

MGMT promoter methylation was studied in 36 patients with salivary gland carcinoma and 19 histologically matched normal tissues by pyrosequencing. MGMT protein expression was examined in 286 patients with salivary gland carcinomas and histologically matched normal tissues by immunohistochemistry on tissue microarrays. The results were correlated to demographic, clinicopathologic parameters, and disease follow-up data.

RESULTS

MGMT hypermethylation was significantly (p = .021) associated with the protein loss. MGMT loss was found in 39.2% of salivary gland carcinomas and was predominant in aggressive tumors (poorly differentiated, grade III, regional lymph node involved). MGMT loss significantly (p = .004) predicted poor clinical outcome of salivary gland carcinomas and defined high-risk subgroups in clinically favorable tumor groups.

CONCLUSION

We suggest that immunohistochemical evaluation of nuclear MGMT protein might serve as a tool for the prediction of overall survival in patients with salivary gland carcinoma.

Chemoradiation for anaplastic oligodendrogliomas: clinical outcomes and prognostic value of molecular markers

Combination of procarbazine, lomustine and vincristine (PCV) with radiation therapy (RT) has been associated with longer survival in patients with anaplastic oligodendroglioma (AO) and anaplastic oligoastrocytoma (AOA), especially in those with chromosome 1p/19q codeletion. We report a multicenter retrospective study of 84 consecutive adult patients with AO and AOA treated with RT plus concomitant and adjuvant temozolomide (TMZ) between February 2004 and January 2011. Correlations between chromosome 1p/19q codeletion, isocitrate dehydrogenase1 (IDH1) mutation, and O-6-methylguanine-DNA methyltransferase (MGMT) promoter methylation with survival outcomes have been analyzed. For all 84 patients the median overall survival (OS) and progression-free survival rates were 55.6 and 45.2 months, respectively. Grade 3 or 4 hematological toxicity occurred in 17 % of patients. Chromosome 1p/19q codeletion was detected in 57 %, IDH1 mutation in 63 %, and MGMT promoter methylation in 74 % of evaluable patients. In multivariate analysis the presence of chromosome 1p/19q codeletion was associated with significant survival benefit (median OS 34 months in noncodeleted tumors and not reached in codeleted tumors; HR 0.16, 95 % CI 0.03-0.45; P = 0.005). IDH1 mutation was also of prognostic significance for longer survival (P = 0.001; HR 0.20, 95 % 0.06-0.41), whereas MGMT promoter methylation was only of borderline significance. The study indicates that RT with concomitant and adjuvant TMZ is a relatively safe treatment associated with longer survival in patients with 1p/19q codeleted and IDH1 mutated tumors. Results from ongoing randomized studies will be essential to clarify if RT plus TMZ may provide survival as good as or better than RT combined with PCV for patients with AO and AOA.