Molecular predictors of progression-free and overall survival in patients with newly diagnosed glioblastoma: a prospective translational study of the German Glioma Network

New prognostic factors and calculators for outcome prediction in patients with recurrent glioblastoma: a pooled analysis of EORTC Brain Tumour Group phase I and II clinical trials

BACKGROUND

Prognostic models have been developed to predict survival of patients with newly diagnosed glioblastoma (GBM). To improve predictions, models should be updated with information at the recurrence. We performed a pooled analysis of European Organization for Research and Treatment of Cancer (EORTC) trials on recurrent glioblastoma to validate existing clinical prognostic factors, identify new markers, and derive new predictions for overall survival (OS) and progression free survival (PFS).

METHODS

Data from 300 patients with recurrent GBM recruited in eight phase I or II trials conducted by the EORTC Brain Tumour Group were used to evaluate patient's age, sex, World Health Organisation (WHO) performance status (PS), presence of neurological deficits, disease history, use of steroids or anti-epileptics and disease characteristics to predict PFS and OS. Prognostic calculators were developed in patients initially treated by chemoradiation with temozolomide.

RESULTS

Poor PS and more than one target lesion had a significant negative prognostic impact for both PFS and OS. Patients with large tumours measured by the maximum diameter of the largest lesion (⩾42mm) and treated with steroids at baseline had shorter OS. Tumours with predominant frontal location had better survival. Age and sex did not show independent prognostic values for PFS or OS.

CONCLUSIONS

This analysis confirms performance status but not age as a major prognostic factor for PFS and OS in recurrent GBM. Patients with multiple and large lesions have an increased risk of death. With these data prognostic calculators with confidence intervals for both medians and fixed time probabilities of survival were derived.

Isocitrate dehydrogenase 1 R132H mutation is not detected in angiocentric glioma

Mutations of isocitrate dehydrogenase-1 gene (IDH1), most commonly resulting in replacement of arginine at position 132 by histidine (R132H), have been described in World Health Organization grade II and III diffuse gliomas and secondary glioblastoma. Immunohistochemistry using a mouse monoclonal antibody has a high specificity and sensitivity for detecting IDH1 R132H mutant protein in sections from formalin-fixed, paraffin-embedded tissue. Angiocentric glioma (AG), a unique neoplasm with mixed phenotypic features of diffuse glioma and ependymoma, has recently been codified as a grade I neoplasm in the 2007 World Health Organization classification of central nervous system tumors. The present study was designed to evaluate IDH1 R132H protein in AG. Three cases of AG were collected, and the diagnoses were confirmed. Expression of mutant IDH1 R132H protein was determined by immunohistochemistry on representative formalin-fixed, paraffin-embedded sections using the antihuman mouse monoclonal antibody IDH1 R132H (Dianova, Hamburg, Germany). Known IDH1 mutation-positive and IDH1 wild-type cases of grade II to IV glioma served as positive and negative controls. All 3 patients were male, aged 3, 5, and 15 years, with intra-axial tumors in the right posterior parietal-occipital lobe, right frontal lobe, and left frontal lobe, respectively. All 3 cases showed characteristic morphologic features of AG, including a monomorphous population of slender bipolar cells that diffusely infiltrated cortical parenchyma and ensheathed cortical blood vessels radially and longitudinally. All 3 cases were negative for the presence of IDH1 R132H mutant protein (0/3). All control cases showed appropriate reactivity. IDH1 R132H mutation has been described as a common molecular signature of grade II and III diffuse gliomas and secondary glioblastoma; however, AG, which exhibits some features of diffuse glioma, has not been evaluated. The absence of mutant IDH1 R132H protein expression in AG may help further distinguish this unique neoplasm from diffuse glioma.

Prognostic value of three different methods of MGMT promoter methylation analysis in a prospective trial on newly diagnosed glioblastoma

Hypermethylation in the promoter region of the MGMT gene encoding the DNA repair protein O⁶-methylguanine-DNA methyltransferase is among the most important prognostic factors for patients with glioblastoma and predicts response to treatment with alkylating agents like temozolomide. Hence, the MGMT status is widely determined in most clinical trials and frequently requested in routine diagnostics of glioblastoma. Since various different techniques are available for MGMT promoter methylation analysis, a generally accepted consensus as to the most suitable diagnostic method remains an unmet need. Here, we assessed methylation-specific polymerase chain reaction (MSP) as a qualitative and semi-quantitative method, pyrosequencing (PSQ) as a quantitative method, and methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) as a semi-quantitative method in a series of 35 formalin-fixed, paraffin-embedded glioblastoma tissues derived from patients treated in a prospective clinical phase II trial that tested up-front chemoradiotherapy with dose-intensified temozolomide (UKT-05). Our goal was to determine which of these three diagnostic methods provides the most accurate prediction of progression-free survival (PFS). The MGMT promoter methylation status was assessable by each method in almost all cases (n = 33/35 for MSP; n = 35/35 for PSQ; n = 34/35 for MS-MLPA). We were able to calculate significant cut-points for the continuous methylation signals at each CpG site analysed by PSQ (range, 11.5 to 44.9%) and at one CpG site assessed by MS-MLPA (3.6%) indicating that a dichotomisation of continuous methylation data as a prerequisite for comparative survival analyses is feasible. Our results show that, unlike MS-MLPA, MSP and PSQ provide a significant improvement of predicting PFS compared with established clinical prognostic factors alone (likelihood ratio tests: p<0.001). Conclusively, taking into consideration prognostic value, cost effectiveness and ease of use, we recommend pyrosequencing for analyses of MGMT promoter methylation in high-throughput settings and MSP for clinical routine diagnostics with low sample numbers.

IDH mutations as an early and consistent marker in low-grade astrocytomas WHO grade II and their consecutive secondary high-grade gliomas

This study investigated the prognostic and predictive significance of IDH1 and IDH2 mutations in low-grade astrocytomas (LGA). The presence and consistency of IDH mutations during the progression of LGA to secondary high-grade gliomas (sHGG) were detected. Samples of patients with LGA and sHGG were investigated. The genomic regions around IDH1 codon 132 and IDH2 codon 172 were PCR amplified and directly sequenced. Furthermore, the MGMT promoter status was provided using the methylation-specific PCR. Our population comprised 71 patients with a total of 45 pairs of LGA and their consecutive sHGG. Median follow-up was 9.6 years. IDH mutations were found in 36/45 LGA (80%) and their sHGG without changes in the mutation status. A total of 71 patients with LGA were analyzed according to clinical and molecular tumor-related factors: 56/71 patients (78.8%) had an IDH mutation without significant influence on the progression-free or overall survival (OS), and 22/71 (31%) of the patients received postoperative radiotherapy (RT) after diagnosis of LGA. Patients with early RT but without IDH mutations had the shortest survival. Our study shows that IDH mutation status is stable during the progression course of LGA to sHGG. The presence of IDH mutations fails to demonstrate a significant influence on survival in the multivariate analysis of LGA patients. Early RT appears to be beneficial only LGA patients with IDH-mutations.

MGMT promoter methylation in gliomas-assessment by pyrosequencing and quantitative methylation-specific PCR

BACKGROUND

Methylation of the O(6)-methylguanine-DNA methyltransferase (MGMT) gene promoter is a favorable prognostic factor in glioblastoma patients. However, reported methylation frequencies vary significantly partly due to lack of consensus in the choice of analytical method.

METHOD

We examined 35 low- and 99 high-grade gliomas using quantitative methylation specific PCR (qMSP) and pyrosequencing. Gene expression level of MGMT was analyzed by RT-PCR.

RESULTS

When examined by qMSP, 26% of low-grade and 37% of high-grade gliomas were found to be methylated, whereas 97% of low-grade and 55% of high-grade gliomas were found methylated by pyrosequencing. The average MGMT gene expression level was significantly lower in the group of patients with a methylated promoter independent of method used for methylation detection. Primary glioblastoma patients with a methylated MGMT promoter (as evaluated by both methylation detection methods) had approximately 5 months longer median survival compared to patients with an unmethylated promoter (log-rank test; pyrosequencing P = .02, qMSP P = .06). One third of the analyzed samples had conflicting methylation results when comparing the data from the qMSP and pyrosequencing. The overall survival analysis shows that these patients have an intermediate prognosis between the groups with concordant MGMT promoter methylation results when comparing the two methods.

CONCLUSION

In our opinion, MGMT promoter methylation analysis gives sufficient prognostic information to merit its inclusion in the standard management of patients with high-grade gliomas, and in this study pyrosequencing came across as the better analytical method.

Isocitrate dehydrogenase mutations in gliomas: mechanisms, biomarkers and therapeutic target

PURPOSE OF REVIEW

Isocitrate dehydrogenases, IDH1 and IDH2, decarboxylate isocitrate to α-ketoglutarate (α-KG) and reduce NADP to NADPH. Point mutations of IDH1 and IDH2 have been discovered in gliomas. IDH mutations cause loss of native enzymatic activities and confer novel activity of converting α-KG to 2-hydroxyglutarate (2-HG). The mechanisms of IDH mutations in gliomagenesis, and their value as diagnostic, prognostic marker and therapeutic target have been extensively studied. This review is to summarize the findings of these studies.

RECENT FINDINGS

Crystal structural studies revealed conformation changes in mutant IDHs, which may explain the gain of function by mutant IDHs. The product of mutant IDHs, 2-HG, is an inhibitor of α-KG-dependent dioxygenases, which may cause genome-wide epigenetic changes in human gliomas. IDH mutations are a favorable prognostic factor for human glioma and can be used as biomarker for differential diagnosis and subclassification rather than predictor of response to treatment. Preliminary data suggested that inhibiting production of the substrate of mutant IDH enzymes caused slow-down of glioma cell growth.

SUMMARY

As valuable diagnostic and prognostic markers of human gliomas, there is still a lack of knowledge on biological functions of mutant IDHs, making targeting IDHs in glioma both difficult and unsecured.

Role of isocitrate dehydrogenase in glioma

Recently, the isocitrate dehydrogenase (IDH) enzymes have become a focal point for research aimed at understanding the biology of glioma and identifying novel targets for therapy. Following the publication of a landmark genetic sequencing study in 2008, which identified IDH1 as a frequently mutated gene in glioblastoma, much work has been carried out to further characterize the frequency, associations and clinical implications of IDH1/2 mutations. Mutations in IDH genes are thought to occur early in tumorigenesis and define a subgroup of glioma that are characterized by specific metabolic changes and improved prognosis. At present, assays identifying tumors with IDH1 mutations are clinically useful as prognostic markers. While the mechanisms linking IDH1/2 mutations to tumor development are still under investigation, the cellular milieu created by these mutations offers potential targets for the development of novel therapeutics.

Relationship between tumor enhancement, edema, IDH1 mutational status, MGMT promoter methylation, and survival in glioblastoma

BACKGROUND AND PURPOSE

Both IDH1 mutation and MGMT promoter methylation are associated with longer survival. We investigated the ability of imaging correlates to serve as noninvasive biomarkers for these molecularly defined GBM subtypes.

MATERIALS AND METHODS

MR imaging from 202 patients with GBM was retrospectively assessed for nonenhancing tumor and edema among other imaging features. IDH1 mutational and MGMT promoter methylation status were determined by DNA sequencing and methylation-specific PCR, respectively. Overall survival was determined by using a multivariate Cox model and the Kaplan-Meier method with a log rank test. A logistic regression model followed by ROC analysis was used to classify the IDH1 mutation and methylation status by using imaging features.

RESULTS

MGMT promoter methylation and IDH1 mutation were associated with longer median survival. Edema levels stratified survival for methylated but not unmethylated tumors. Median survival for methylated tumors with little/no edema was 2476 days (95% CI, 795), compared with 586 days (95% CI, 507-654) for unmethylated tumors or tumors with edema. All IDH1 mutant tumors were nCET positive, and most (11/14, 79%) were located in the frontal lobe. Imaging features including larger tumor size and nCET could be used to determine IDH1 mutational status with 97.5% accuracy, but poorly predicted MGMT promoter methylation.

CONCLUSIONS

Imaging features are potentially predictive of IDH1 mutational status but were poorly correlated with MGMT promoter methylation. Edema stratifies survival in MGMT promoter methylated but not in unmethylated tumors; patients with methylated tumors with little or no edema have particularly long survival.

Does gender matter in glioblastoma?

BACKGROUND The clinical outcome of glioblastoma (GBM) patients who receive radiotherapy alone or with chemotherapy is well established. However, little is known about how many patients do not receive this treatment. We consider it is important to investigate why a proportion of operated patients do not receive further treatment after surgery. METHODS We reviewed all consecutive GBM patients operated on in our hospital between January 2000 and December 2008. RESULTS A total of 216 patients with GBM were identified. Fifty-five (25%) did not receive any treatment after surgery. Univariate analysis showed that factors associated with no further treatment after surgery were older than 60 years (p=0.002), of female gender (p=0.03), had a KPS<70 (p<0.001) and had had a biopsy (p<0.001). Multivariate analysis indicated that age =60 years and KPS <70 were independent predictors of no further treatment after surgery. Gender was not an independent variable. However, women in the whole series were older than 60 years (p=0.01), and they had a worse KPS (p=0.02) and more biopsies (p=0.04) than men. In the whole group, median survival time was 10.4 months for men (n=125) vs. 7.2 months for women (n=91), log rank p<0.04. This difference was not observed in the group that was treated after surgery. CONCLUSIONS One out of four patients could not be treated after surgery. Independent predictors were older age and low KPS. These poor risk variables were more frequent in women and their survival was therefore lower than men in our series.

Comparative assessment of 5 methods (methylation-specific polymerase chain reaction, MethyLight, pyrosequencing, methylation-sensitive high-resolution melting, and immunohistochemistry) to analyze O6-methylguanine-DNA-methyltranferase in a series of 100 glioblastoma patients

BACKGROUND

There is a strong need to determine the best technique for O(6) -methylguanine-DNA-methyltranferase (MGMT) analysis, because MGMT status is currently used in clinical trials and occasionally in routine clinical practice for glioblastoma patients.

METHODS

The authors compared analytical performances and predictive values of 5 techniques in a series of 100 glioblastoma patients who received standard of care treatment (Stupp protocol).

RESULTS

MGMT promoter was considered methylated in 33%, 33%, 42%, and 60% of patients by methylation-sensitive high-resolution melting, MethyLight, pyrosequencing (with an optimal risk cutoff at 8% for the average percentage of the 5 CpGs tested), and methylation-specific polymerase chain reaction (MS-PCR), respectively. Fifty-nine percent of the samples had <23% (the optimal risk cutoff) of MGMT-positive tumor cells. The best predictive values for overall survival (OS), after adjustment for age and performance status, were obtained by pyrosequencing (hazard ratio [HR], 0.32; P < .0001), MS-PCR (HR, 0.37; P < .0001), and immunohistochemistry (HR, 0.43; P = .0005) as compared with methylation-sensitive high-resolution melting (HR, 0.52 P = .02) and MethyLight (HR, 0.6; P = .05). For progression-free survival (PFS), the best predictive values were obtained with pyrosequencing (HR, 0.35; P < .0001), methylation-sensitive high-resolution melting (HR, 0.46; P = .002), and MS-PCR (HR, 0.49; P = .002). Combining pyrosequencing and immunohistochemistry slightly improved predictive power for OS, but not for PFS. Poor reproducibility and interobserver variability were, however, observed for immunohistochemistry.

CONCLUSIONS

Good prediction of survival in addition to high reproducibility and sensitivity made pyrosequencing the best among the 5 techniques tested in this study.

Correlation of IDH1 mutation with clinicopathologic factors and prognosis in primary glioblastoma: a report of 118 patients from China

It has been reported that IDH1 (IDH1R132) mutation was a frequent genomic alteration in grade II and grade III glial tumors but rare in primary glioblastoma (pGBM). To elucidate the frequency of IDH1 mutation and its clinical significance in Chinese patients with pGBM, one hundred eighteen pGBMs were assessed by pyro-sequencing for IDH1 mutation status, and the results were correlated with clinical characteristics and molecular pathological factors. IDH1 mutations were detected in 19/118 pGBM cases (16.1%). Younger age, methylated MGMT promoter, high expression of mutant P53 protein, low expression of Ki-67 or EGFR protein were significantly correlated with IDH1 mutation status. Most notably, we identified pGBM cases with IDH1 mutation were mainly involved in the frontal lobe when compared with those with wild-type IDH1. In addition, Kaplan-Meier survival analysis revealed a highly significant association between IDH1 mutation and a better clinical outcome (p = 0.026 for progression-free survival; p = 0.029 for overall survival). However, in our further multivariable regression analysis, the independent prognostic effect of IDH1 mutation is limited when considering age, preoperative KPS score, extent of resection, TMZ chemotherapy, and Ki-67 protein expression levels, which might narrow its prognostic power in Chinese population in the future.

Recent advances in the molecular understanding of glioblastoma

Glioblastoma is the most common and most aggressive primary brain tumor. Despite maximum treatment, patients only have a median survival time of 15 months, because of the tumor’s resistance to current therapeutic approaches. Thus far, methylation of the O⁶-methylguanine-DNA methyltransferase (MGMT) promoter has been the only confirmed molecular predictive factor in glioblastoma. Novel “genome-wide” techniques have identified additional important molecular alterations as mutations in isocitrate dehydrogenase 1 (IDH1) and its prognostic importance. This review summarizes findings and techniques of genetic, epigenetic, transcriptional, and proteomic studies of glioblastoma. It provides the clinician with an up-to-date overview of current identified molecular alterations that should ultimately lead to new therapeutic targets and more individualized treatment approaches in glioblastoma.

Molecular profile of oligodendrogliomas in young patients

Several studies on molecular profiling of oligodendrogliomas (OGs) in adults have shown a distinctive genetic pattern characterized by combined deletions of chromosome arms 1p and 19q, O6-methylguanine-methyltransferase (MGMT) methylation, and isocitrate dehydrogenase 1 (IDH1) mutation, which have potential diagnostic, prognostic, and even therapeutic relevance. OGs in pediatric and young adult patients are rare and have been poorly characterized on a molecular and biological basis, and it remains uncertain whether markers with prognostic significance in adults also have predictive value in these patients. Fourteen cases of OGs in young patients (age, ≤ 25 years) who received a diagnosis over 7 years were selected (7 pediatric patients age ≤ 18 years and 7 young adults aged 19-25 years). The cases were evaluated for 1p/19q status, MGMT promoter methylation, p53 mutation, and IDH1 mutation. None of the pediatric cases showed 1p/19q deletion. In young adults, combined 1p/19q loss was observed in 57% and isolated 1p loss in 14% of cases. The majority of cases in both subgroups (71% in each) harbored MGMT gene promoter methylation. TP53 and IDH1 mutations were not seen in any of the cases in both the groups. To our knowledge, this is the first study to show that molecular profile of OGs in pediatric and young adult patients is distinct. Further large-scale studies are required to identify additional clinically relevant genetic alterations in this group of patients.

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.

Establishing the standard of care for patients with newly diagnosed and recurrent glioblastoma

The current standard of care for patients with newly diagnosed glioblastoma includes maximal safe tumor resection followed by concurrent external-beam radiation with daily low-dose temozolomide followed by 6 to 12 months of adjuvant temozolomide, typically by using a cycle of 5 consecutive days out of 28. Efforts to improve on these results from the European Organisation for Research and Treatment of Cancer (EORTC)/National Cancer Institute of Canada (NCIC) trial using either dose-dense chemotherapy strategies or combinations with signal transduction modulators have, to date, been unsuccessful. Two large international randomized trials examining the efficacy of adding bevacizumab, an antiangiogenic agent, to the standard treatment have been completed, with expectations of results within in the next 2 years. For recurrent glioblastoma, there are no firmly established standards of care. Although intracavitary insertion of carmustine-impregnated polymers has been approved by the U.S. Food and Drug Administration (FDA), this strategy is not widely used. Bevacizumab has been FDA approved for recurrent glioblastoma, but no randomized trial has clearly demonstrated a survival benefit. Alternative dosing schedules of temozolomide (i.e., metronomic) has modest activity even in patients with prior temozolomide exposure. Clinical trials testing small-molecule signal transduction modulators have been disappointing, although most report a small response rate, suggesting that molecularly definable tumor subpopulations may help guide treatment decisions. Successful implementation of marker-based treatment would lead to personalized care and the creation of individualized standards of care.

Glioblastoma biomarkers from bench to bedside: advances and challenges

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumour, with few available therapies providing significant improvements in mortality. Biomarkers, which are defined by the National Institutes of Health as 'characteristics that are objectively measured and evaluated as indicators of normal biologic processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention', have the potential to play valuable roles in the diagnosis and treatment of GBM. Although GBM biomarker research is still in its early stages because of the tumour's complex pathophysiology, a number of potential markers have been identified which can be measured in either brain tissue or blood serum. In conjunction with other clinical data, particularly neuroimaging modalities such as MRI, these proteins could contribute to the clinical management of GBM by helping to classify tumours, predict prognosis and assess treatment response. In this article, we review the current understanding of GBM pathophysiology and recent advances in GBM biomarker research, and discuss the potential clinical implications of promising biomarkers. A better understanding of GBM pathophysiology will allow researchers and clinicians to identify optimal biomarkers and methods of interpretation, leading to advances in tumour classification, prognosis prediction and treatment assessment.

Oncolytic virus-mediated manipulation of DNA damage responses: synergy with chemotherapy in killing glioblastoma stem cells

BACKGROUND

Although both the alkylating agent temozolomide (TMZ) and oncolytic viruses hold promise for treating glioblastoma, which remains uniformly lethal, the effectiveness of combining the two treatments and the mechanism of their interaction on cancer stem cells are unknown.

METHODS

We investigated the efficacy of combining TMZ and the oncolytic herpes simplex virus (oHSV) G47Δ in killing glioblastoma stem cells (GSCs), using Chou-Talalay combination index analysis, immunocytochemistry and fluorescence microscopy, and neutral comet assay. The role of treatment-induced DNA double-strand breaks, activation of DNA damage responses, and virus replication in the cytotoxic interaction between G47Δ and TMZ was examined with a panel of pharmacological inhibitors and short-hairpin RNA (shRNA)-mediated knockdown of DNA repair pathways. Comparisons of cell survival and virus replication were performed using a two-sided t test (unpaired). The survival of athymic mice (n = 6-8 mice per group) bearing GSC-derived glioblastoma tumors treated with the combination of G47Δ and TMZ was analyzed by the Kaplan-Meier method and evaluated with a two-sided log-rank test.

RESULTS

The combination of G47Δ and TMZ acted synergistically in killing GSCs but not neurons, with associated robust induction of DNA damage. Pharmacological and shRNA-mediated knockdown studies suggested that activated ataxia telangiectasia mutated (ATM) is a crucial mediator of synergy. Activated ATM relocalized to HSV DNA replication compartments where it likely enhanced oHSV replication and could not participate in repairing TMZ-induced DNA damage. Sensitivity to TMZ and synergy with G47Δ decreased with O(6)-methylguanine-DNA-methyltransferase (MGMT) expression and MSH6 knockdown. Combined G47Δ and TMZ treatment extended survival of mice bearing GSC-derived intracranial tumors, achieving long-term remission in four of eight mice (median survival = 228 days; G47Δ alone vs G47Δ + TMZ, hazard ratio of survival = 7.1, 95% confidence interval = 1.9 to 26.1, P = .003) at TMZ doses attainable in patients.

CONCLUSIONS

The combination of G47Δ and TMZ acts synergistically in killing GSCs through oHSV-mediated manipulation of DNA damage responses. This strategy is highly efficacious in representative preclinical models and warrants clinical translation.

MiR-195, miR-196b, miR-181c, miR-21 expression levels and O-6-methylguanine-DNA methyltransferase methylation status are associated with clinical outcome in glioblastoma patients

Glioblastoma multiforme (GBM) is the most frequently occurring primary malignant brain tumor; patients with GBM often have a very poor prognosis and differing responses to treatment. Therefore, it is very important to find new biomarkers that can predict clinical outcomes and help in treatment decisions. MicroRNAs are small, non-coding RNAs that function as post-transcriptional regulators of gene expression and play a key role in the pathogenesis of GBM. In a group of 38 patients with primary GBM, we analyzed the expression of eight microRNAs (miR-21, miR-128a, miR-181c, miR-195, miR-196a, miR-196b, miR-221, and miR-222). In addition, we examined the methylation status of O-6-methylguanine-DNA methyltransferase (MGMT) promoter by high-resolution melting analysis, as this has been shown to be a predictive marker in GBM. MGMT methylation status correlated with progression-free survival (P = 0.0201; log-rank test) as well as with overall survival (P = 0.0054; log-rank test). MiR-195 (P = 0.0124; log-rank test) and miR-196b (P = 0.0492; log-rank test) positively correlated with overall survival. Evaluation of miR-181c in combination with miR-21 predicted time to progression within 6 months of diagnosis with 92% sensitivity and 81% specificity (P < 0.0001). Our data confirmed that the methylation status of MGMT but also miR-21, miR-181c, miR-195, and miR-196b to be associated with survival of GBM patients. Above all, we suggest that the combination of miR-181c and miR-21 could be a very sensitive and specific test to identify patients at high risk of early progression after surgery.

Treatment of glioblastoma in "elderly" patients

OPINION STATEMENT

The number of patients over 65 with newly diagnosed glioblastoma is anticipated to increase significantly in coming decades as a result of demographic shifts in the United States. Older patients with this disease have a significantly worse life expectancy compared with patients under 65. Mounting clinical evidence suggests that fit elderly patients with glioblastoma benefit from the addition of temozolomide to standard surgery and radiation. As a result, for healthy patients over 65 we recommend maximal surgical debulking followed by involved-field radiotherapy (60 Gy in 30 fractions) with concurrent temozolomide (75 mg/m(2)/day) and 6 months of adjuvant temozolomide (150-200 mg/m(2)/day for five consecutive days/month). Patients over 65 with newly diagnosed or recurrent glioblastoma should also be considered for inclusion in clinical trials. MGMT is a validated prognostic marker in patients over 65 and may be useful in clinical decision-making in frail elderly patients. Age alone should not be a factor in deciding how patients with newly diagnosed glioblastoma should be treated.

Gene expression and network-based analysis reveals a novel role for hsa-miR-9 and drug control over the p38 network in glioblastoma multiforme progression

Background

Glioblastoma multiforme (GBM) is the most common, aggressive and malignant primary tumor of the brain and is associated with one of the worst 5-year survival rates among all human cancers. Identification of molecular interactions that associate with disease progression may be key in finding novel treatments.

Methods

Using five independent molecular and clinical datasets with a set of computational algorithms we were able to identify a gene-gene and gene-microRNA network that significantly stratifies patient prognosis. By combining gene expression microarray data with microRNA expression levels, copy number alterations, drug response and clinical data, combined with network knowledge, we were able to identify a single pathway at the core of glioblastoma.

Results

This network, the p38 network, and an associated microRNA, hsa-miR-9, facilitate prognostic stratification. The microRNA hsa-miR-9 correlated with network behavior and presents binding affinities with network members in a manner that suggests control over network behavior. A similar control over network behavior is possible through a set of drugs. These drugs are part of the treatment regimen for a subpopulation of the patients that participated in the TCGA study and for which the study provides clinical information. Interestingly, the patients that were treated with these specific sets of drugs, all of which targeted against p38 network members, demonstrate highly significant stratification of prognosis.

Conclusions

Combined, these results call for attention to p38 network targeted treatment and present the p38 network-hsa-miR-9 control mechanism as critical in GBM progression.

IDH mutations predict longer survival and response to temozolomide in secondary glioblastoma

Recent studies have shown that isocitrate dehydrogenase 1/2 (IDH1/2) mutations occur frequently in secondary glioblastoma. This study aimed to investigate their impact on temozolomide chemosensitivity and relationship with O(6)-methylguanine DNA methyltransferase (MGMT) promoter methylation in secondary glioblastoma. Searches for IDH1 and IDH2 mutations, 1p19q codeletion, MGMT promoter methylation, and p53 expression were carried out in a series of 86 secondary glioblastomas and correlated with progression-free survival and overall survival. Response to temozolomide was evaluated by progression-free survival, as well as by tumor size on successive MRI scans, then correlated with molecular alterations. IDH (IDH1 or IDH2) mutations were found in 58/79 patients (73.4%). IDH mutation, MGMT promoter methylation, and 1p19q codeletion were associated with prolonged progression-free survival in univariate (P < 0.001, P < 0.001, P = 0.003, respectively) and multivariate analysis (P < 0.001, P < 0.001, P = 0.035, respectively). IDH mutation (P = 0.001) and MGMT promoter methylation (P = 0.011) were correlated with a higher rate of objective response to temozolomide. Further analysis of response to temozolomide showed that patients with both IDH mutation and MGMT promoter methylation had the best response rate to temozolomide. IDH mutation appears to be a significant marker of positive chemosensitivity in secondary glioblastoma. Use of IDH status combined with MGMT promoter status as a stratification factor seems appropriate in future clinical trials involving temozolomide for the treatment of patients with secondary glioblastoma.

Survival of European patients with central nervous system tumors

We present estimates of population-based 5-year relative survival for adult Europeans diagnosed with central nervous system tumors, by morphology (14 categories based on cell lineage and malignancy grade), sex, age at diagnosis and region (UK and Ireland, Northern, Central, Eastern and Southern Europe) for the most recent period with available data (2000-2002). Sources were 39 EUROCARE cancer registries with continuous data from 1996 to 2002. Survival time trends (1988 to 2002) were estimated from 24 cancer registries with continuous data from 1988. Overall 5-year relative survival was 85.0% for benign, 19.9% for malignant tumors. Benign tumor survival ranged from 90.6% (Northern Europe) to 77.4% (UK and Ireland); for malignant tumors the range was 25.1% (Northern Europe) to 15.6% (UK and Ireland). Survival decreased with age at diagnosis and was slightly better for women (malignant tumors only). For glial tumors, survival varied from 83.5% (ependymoma and choroid plexus) to 2.7% (glioblastoma); and for non-glioma tumors from 96.5% (neurinoma) to 44.9% (primitive neuroectoderm tumor/medulloblastoma). Survival differences between regions narrowed after adjustment for morphology and age, and were mainly attributable to differences in morphology mix; however UK and Ireland and Eastern Europe patients still had 40% and 30% higher excess risk of death, respectively, than Northern Europe patients (reference). Survival for benign tumors increased from 69.3% (1988-1990) to 77.1% (2000-2002); but survival for malignant tumors did not improve indicating no useful advances in treatment over the 14-year study period, notwithstanding major improvement in the diagnosis and treatment of other solid cancers.

Evidence for sequenced molecular evolution of IDH1 mutant glioblastoma from a distinct cell of origin

PURPOSE

Mutation in isocitrate dehydrogenase 1 (IDH1) at R132 (IDH1(R132MUT)) is frequent in low-grade diffuse gliomas and, within glioblastoma (GBM), has been proposed as a marker for GBMs that arise by transformation from lower-grade gliomas, regardless of clinical history. To determine how GBMs arising with IDH1(R132MUT) differ from other GBMs, we undertook a comprehensive comparison of patients presenting clinically with primary GBM as a function of IDH1(R132) mutation status.

PATIENTS AND METHODS

In all, 618 treatment-naive primary GBMs and 235 lower-grade diffuse gliomas were sequenced for IDH1(R132) and analyzed for demographic, radiographic, anatomic, histologic, genomic, epigenetic, and transcriptional characteristics.

RESULTS

Investigation revealed a constellation of features that distinguishes IDH1(R132MUT) GBMs from other GBMs (including frontal location and lesser extent of contrast enhancement and necrosis), relates them to lower-grade IDH1(R132MUT) gliomas, and supports the concept that IDH1(R132MUT) gliomas arise from a neural precursor population that is spatially and temporally restricted in the brain. The observed patterns of DNA sequence, methylation, and copy number alterations support a model of ordered molecular evolution of IDH1(R132MUT) GBM in which the appearance of mutant IDH1 protein is an initial event, followed by production of p53 mutant protein, and finally by copy number alterations of PTEN and EGFR.

CONCLUSION

Although histologically similar, GBMs arising with and without IDH1(R132MUT) appear to represent distinct disease entities that arise from separate cell types of origin as the result of largely nonoverlapping sets of molecular events. Optimal clinical management should account for the distinction between these GBM disease subtypes.

Prognostic significance of alterations in IDH enzyme isoforms in patients with AML treated with high-dose cytarabine and idarubicin

BACKGROUND

IDH1 and IDH2 gene mutations are novel, recurring molecular aberrations among patients with normal karyotype acute myeloid leukemia (AML).

METHODS

Among 358 patients with AML treated on 4 protocols using high-dose ara-C plus idarubicin induction, pretreatment samples were available for 170 (median age 53 years, [range, 17-73]; 96% ≤65) and were evaluated for IDH1R132, IDH2R172, and IDH2R140 mutations or the codon 105 single nucleotide polymorphism (SNP) in IDH1.

RESULTS

IDH1 and IDH2 mutations were present in 12 (7%) and 24 (14%) of patients, and IDH1 G105 SNP in 24 (14%). Overall, 52 (30%) patients had IDH gene alterations. There was no association with complete response (CR), remission duration, overall survival, and event-free survival and any of the IDH alterations, and no association with a higher CR rate or survival with the 4 regimens for the 52 patients with aberrant IDH. Among the patients with diploid karyotype and NPM1(mut) FLT3(WT) genotype, those with IDH1 or IDH2 mutations had an inferior outcome.

CONCLUSIONS

IDH aberrations and IDH1 codon 105 SNP occur in about 30% of younger patients with AML, mostly with diploid karyotype. Using high-dose ara-C-based induction regimens, we did not detect an association with outcome for any of the aberrations.

IDH1/2 gene status defines the prognosis and molecular profiles in patients with grade III gliomas

BACKGROUND

The discovery of isocitrate dehydrogenase 1 and 2 gene (IDH1/2) mutations has enabled grade III glioma to be divided into mutated and wild-type IDH1/2 groups, which are known to carry different prognosis and molecular features. However, detailed subgroup analysis of grade III glioma is limited. To address this, we investigated molecular and prognostic features of grade III glioma with and without IDH1/2 mutation.

METHODS

We retrospectively analyzed 115 grade III glioma patients. Clinical parameters were obtained from medical records. The mutation of IDH1/2 and TP53 was analyzed by direct sequencing. O(6)-methylguanine methyltransferase gene (MGMT) gene promoter methylation status was determined by methylation-specific polymerase chain reaction. Detection of chromosome copy number changes of 1p, 7p (EGFR), 9p (CDKN2A), 10q (PTEN), and 19q was carried out by multiple ligation-dependent probe amplification. Patients were divided into two groups, mutated IDH1/2 and wild-type IDH1/2, for correlation with the factors analyzed.

RESULTS

In our series, as previously reported, IDH1/2 mutation was an independent prognostic marker for improved progression-free and overall survival (OS) (P < 0.0001 and P < 0.0001, respectively) in patients with grade III gliomas. Subgroup analysis found that incomplete resection, 7p gain, and TP53 mutation were independent prognostic factors of poor outcome in grade III glioma patients with mutated IDH1/2 (P = 0.0092, P = 0.015 and P = 0.026, respectively), while there were none in patients with wild-type IDH1/2.

CONCLUSIONS

IDH1/2 gene status was significantly associated with prognosis in grade III gliomas. Subgroup analysis found that poor prognostic factors existed even in patients with IDH1/2 mutation.

Recent advancements in multimodality treatment of gliomas

Gliomas account for the vast majority of malignant adult brain tumors. Even though tremendous effort has been made to optimize treatment of patients with high-grade glioma, the prognosis remains poor, especially for patients with glioblastoma. The dismal prognosis conferred by these tumors is in part caused by the tendency to diffusely infiltrate into neighboring brain tissue, but also by the inherent resistance of these tumors to both chemotherapy and radiation. This article reviews the recent advancements in multimodality treatment of patients with gliomas, both in the primary and recurrent setting, with an emphasis on the emerging targeted therapies. Moreover, the external beam radiotherapy options, including intensity modulated radiotherapy and particle (proton and carbon ion) radiotherapy are reviewed.

Value and limitations of immunohistochemistry and gene sequencing for detection of the IDH1-R132H mutation in diffuse glioma biopsy specimens

To assess the value of anti-isocitrate dehydrogenase 1 (IDH1) immunohistochemistry for evaluating diffuse gliomas, we analyzed anti-IDH1-R132H immunohistochemistry using monoclonal antibodies DIA-H09 and IMab-1 and IDH1 gene sequencing in formalin-fixed and paraffin-embedded biopsy samples of 95 diffuse gliomas. We found concordant immunostaining results using the 2 antibodies in 94 (98.9%) of the 95 cases, but DIA-H09 generally showed a higher signal-to-background ratio than IMab-1 did. Fifty-five percent of cases showed anti-IDH1-R132H immunostaining of virtually all tumor cells and 15% of only a fraction of tumor cells. All cases with complete or partial immunostaining of the tumor tissue carried the IDH1-R132H mutation. In all cases with negative immunostaining results (approximately 30%), genetic analysis showed IDH1 wild-type or non-R132H-IDH1 mutations. In a single tiny biopsy, both anti-IDH1-R132H antibodies showed immunoreactivity, but genetic testing was inconclusive. Our data confirm anti-IDH1-R132H immunostaining as a reliable method for evaluation of IDH1 gene mutation status. They also suggest the following: (i) in some cases, nonspecific background staining or regional heterogeneity of IDH1-R132H protein expression may necessitate confirmatory genetic analysis; (ii) for individual cases, anti-IDH1-R132H immunostaining may not reliably identify infiltrating tumor cells admixed with preexisting or reactive glial cells; and (iii) in tiny biopsies, immunohistochemistry may be more sensitive for detection of IDH1-R132H mutation than genetic analysis.

Adult glioblastoma multiforme survival in the temozolomide era: a population-based analysis of Surveillance, Epidemiology, and End Results registries

BACKGROUND

Survival after a glioblastoma multiforme (GBM) diagnosis remained static during the several decades before 1999. We hypothesized that the progressive increase in temozolomide use for GBM treatment that began in 1999 in the United States would be paralleled by a corresponding improvement in survival.

METHODS

We included 19,674 GBM cases, ages 20 years or greater, diagnosed 1993 to 2007 in the population-based Surveillance, Epidemiology, and End Results Program database. We used proportional hazards models to calculate calendar period hazard ratios (HR) and 95% confidence intervals (CI), adjusted for demographic covariates. We compared survival across periods using the Kaplan-Meier method.

RESULTS

Starting with cases diagnosed in 1999 to 2001, we observed a progressive decrease in HRs compared with cases diagnosed in 1993 to 1995. The multivariate-adjusted HR for 2005 to 2007 versus 1993 to 1995 was 0.69 (95% CI, 0.65-0.72). Age-stratified analyses revealed that this progressive decrease occurred in all age groups except 80+ years. Two-year survival increased from 7% among cases diagnosed in 1993 to 1995 and 1996 to 1998 to 9% among cases diagnosed in 1999 to 2001, 13% in 2002 to 2004, and 17% in 2005 to 2007. The disparity in survival between young and old patients increased in the temozolomide era, with 2-year survival of 39% among cases diagnosed at ages 20 to 44 years and 1% among cases diagnosed at 80+ years in 2005 to 2007.

CONCLUSIONS

We observed a modest, but meaningful, population-based survival improvement for GBM patients in the United States. Widespread adoption of temozolomide represents the most likely explanation, although other treatment advances, such as increased extent of surgical resection, also may have played a role.

Expression of VEGF and MMP-9 and MRI imaging changes in cerebral glioma

The purpose of the present study was to investigate the association of vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) expression with the histopathological grading of tumors in cerebral glioma. A total of 45 patients with pathologically confirmed cerebral glioma were divided into two groups: a low-grade group (grades I and II, 21 cases) and a high-grade group (grades III and IV, 24 cases). Immunohistochemical staining of tumor samples showed the percentages of tumors expressing VEGF and MMP-9 in the high-grade group to be 95.83 and 75%, respectively, significantly higher than those of the low-grade group (66.67 and 23.81%, P<0.05 and P<0.01, respectively). The magnetic resonance imaging (MRI) results indicated that the peripheral edema index (EI), enhancement percentage (EP), and the maximum diameter of the tumor in the high-grade group were significantly higher than those in the low-grade group (P<0.05, P<0.01, and P<0.05). Moreover, the expression of VEGF and MMP-9 was positively correlated with EI, EP and the maximum diameter of the tumor (P<0.05). Therefore, VEGF and MMP-9 expression were correlated to the invasion of glioma. The association of their expression levels with EI, EP and the maximum tumor diameter indicates that these markers may be used to estimate tumor malignancy for future clinical diagnosis and treatment.

Genomic profiles of glioma

Recent large-scale genomic profiling studies of glioma have yielded a proliferation of candidate subclasses, biomarkers and therapeutic targets for investigation. Some findings, such as that of IDH mutation in low-grade gliomas and secondary glioblastoma (GBM), fit well into established notions of different routes of gliomagenesis. Other results, such as the division of primary GBM based on signaling pathway alterations, suggest new pathogenetic routes with implications for treatment. The analysis of this data is still in the early stage. Nonetheless, several preliminary findings merit consideration in the development and interpretation of current clinical trials.

Promoter methylation and expression of MGMT and the DNA mismatch repair genes MLH1, MSH2, MSH6 and PMS2 in paired primary and recurrent glioblastomas

Epigenetic silencing of the O(6) -methylguanine-DNA methyltransferase (MGMT) gene promoter is associated with prolonged survival in glioblastoma patients treated with temozolomide (TMZ). We investigated whether glioblastoma recurrence is associated with changes in the promoter methylation status and the expression of MGMT and the DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6 and PMS2 in pairs of primary and recurrent glioblastomas of 80 patients, including 64 patients treated with radiotherapy and TMZ after the first operation. Among the primary tumors, the MGMT promoter was methylated in 31 patients and unmethylated in 49 patients. In 71 patients (89%), the MGMT promoter methylation status of the primary tumor was retained at recurrence. MGMT promoter methylation, but not MGMT protein expression, was associated with longer progression-free survival, overall survival and postrecurrence survival (PRS). Moreover, PRS was increased under salvage chemotherapy. Investigation of primary and recurrent glioblastomas of 43 patients did not identify promoter methylation in any of the four MMR genes. However, recurrent glioblastomas demonstrated significantly lower MSH2, MSH6 and PMS2 protein expression as detected by immunohistochemistry. In conclusion, reduced expression of MMR proteins, but not changes in MGMT promoter methylation, is characteristic of glioblastomas recurring after the current standards of care.

Isocitrate dehydrogenase mutations in diffuse gliomas: clinical and aetiological implications

The discovery of isocitrate dehydrogenase (IDH) mutations in gliomas is one example of the large impact that next-generation sequencing is having on the understanding of tumour biology and human disease in general. IDH mutations are early and common events in the development of astrocytomas, oligodendrogliomas and oligoastrocytomas. IDH mutations are also found in some myeloid malignancies and soft tissue tumours, but are rare in other malignancies. IDH mutation detection can be incorporated into routine pathology practice via immunohistochemistry and/or standard sequencing techniques and has great diagnostic value. An emerging theme is that IDH mutation status in gliomas is of great prognostic relevance, and there are proposals to include IDH mutation status in the next iteration of the WHO classification of gliomas. The mechanisms of action(s) of mutant IDH are not fully understood, but the understanding is progressing rapidly, and may provide a mechanism to link diverse proneoplastic processes such as oxidative damage and epigenetic dysregulation. There are exciting prospects of novel therapies for glioma patients emerging from the elucidation of these mechanisms. Given the diagnostic and prognostic implications of IDH mutation, and the potential for new therapies, all gliomas should be assessed for IDH mutation status in the future.

New insights into glioma classification based on isocitrate dehydrogenase 1 and 2 gene status

In glioma, mutations in the isocitrate dehydrogenase 1 and 2 (IDH1/2) genes have been receiving attention. IDH1/2 mutations are frequently found in grade II and III gliomas. These genetic alterations occur very early in gliomagenesis and strongly predict favorable outcome in patients with high-grade gliomas. Despite the evolution of studies on this topic, the underlying mechanism of the IDH1/2 mutations remains unknown. Here, we briefly review the current knowledge of IDH1/2 and discuss molecular diagnostics based on IDH1/2 gene status.

Molecular diagnostics of gliomas

CONTEXT

Gliomas are the most common primary brain tumors of adults and include a variety of histologic types and morphologies. Histologic evaluation remains the gold standard for glioma diagnosis; however, diagnostic difficulty may arise from tumor heterogeneity, overlapping morphologic features, and tumor sampling. Recently, our knowledge about the genetics of these tumors has expanded, and new molecular markers have been developed. Some of these markers have shown diagnostic value, whereas others are useful prognosticators for patient survival and therapeutic response.

OBJECTIVE

To review the most clinically useful molecular markers and their detection techniques in gliomas.

DATA SOURCES

Review of the pertinent literature and personal experience with the molecular testing in gliomas.

CONCLUSIONS

This article provides an overview of the most common molecular markers in neurooncology, including 1p/19q codeletion in oligodendroglial tumors, mutations in the isocitrate dehydrogenase 1 and 2 genes in diffuse gliomas, hypermethylation of the O(6)-methylguanine-DNA methyltransferase gene promoter in glioblastomas and anaplastic gliomas, alterations in the epidermal growth factor receptor and phosphatase and tensin homolog genes in high-grade gliomas, as well as BRAF alterations in pilocytic astrocytomas. Molecular testing of gliomas is increasingly used in routine clinical practice and requires that neuropathologists be familiar with these genetic markers and the molecular diagnostic techniques for their detection.

IDH1 R132H decreases proliferation of glioma cell lines in vitro and in vivo

OBJECTIVE

A high percentage of grade II and III gliomas have mutations in the gene encoding isocitrate dehydrogenase (IDH1). This mutation is always a heterozygous point mutation that affects the amino acid arginine at position 132 and results in loss of its native enzymatic activity and gain of alternative enzymatic activity (producing D-2-hydroxyglutarate). The objective of this study was to investigate the cellular effects of R132H mutations in IDH1.

METHODS

Functional consequences of IDH1(R132H) mutations were examined among others using fluorescence-activated cell sorting, kinome and expression arrays, biochemical assays, and intracranial injections on 3 different (glioma) cell lines with stable overexpression of IDH1(R132H) .

RESULTS

IDH1(R132H) overexpression in established glioma cell lines in vitro resulted in a marked decrease in proliferation, decreased Akt phosphorylation, altered morphology, and a more contact-dependent cell migration. The reduced proliferation is related to accumulation of D-2-hydroxyglutarate that is produced by IDH1(R132H) . Mice injected with IDH1(R132H) U87 cells have prolonged survival compared to mice injected with IDH1(wt) or green fluorescent protein-expressing U87 cells.

INTERPRETATION

Our results demonstrate that IDH1(R132H) dominantly reduces aggressiveness of established glioma cell lines in vitro and in vivo. In addition, the IDH1(R132H) -IDH1(wt) heterodimer has higher enzymatic activity than the IDH1(R132H) -IDH1(R132H) homodimer. Our observations in model systems of glioma might lead to a better understanding of the biology of IDH1 mutant gliomas, which are typically low grade and often slow growing.

Cell cycle and aging, morphogenesis, and response to stimuli genes are individualized biomarkers of glioblastoma progression and survival

BACKGROUND

Glioblastoma is a complex multifactorial disorder that has swift and devastating consequences. Few genes have been consistently identified as prognostic biomarkers of glioblastoma survival. The goal of this study was to identify general and clinical-dependent biomarker genes and biological processes of three complementary events: lifetime, overall and progression-free glioblastoma survival.

METHODS

A novel analytical strategy was developed to identify general associations between the biomarkers and glioblastoma, and associations that depend on cohort groups, such as race, gender, and therapy. Gene network inference, cross-validation and functional analyses further supported the identified biomarkers.

RESULTS

A total of 61, 47 and 60 gene expression profiles were significantly associated with lifetime, overall, and progression-free survival, respectively. The vast majority of these genes have been previously reported to be associated with glioblastoma (35, 24, and 35 genes, respectively) or with other cancers (10, 19, and 15 genes, respectively) and the rest (16, 4, and 10 genes, respectively) are novel associations. Pik3r1, E2f3, Akr1c3, Csf1, Jag2, Plcg1, Rpl37a, Sod2, Topors, Hras, Mdm2, Camk2g, Fstl1, Il13ra1, Mtap and Tp53 were associated with multiple survival events.Most genes (from 90 to 96%) were associated with survival in a general or cohort-independent manner and thus the same trend is observed across all clinical levels studied. The most extreme associations between profiles and survival were observed for Syne1, Pdcd4, Ighg1, Tgfa, Pla2g7, and Paics. Several genes were found to have a cohort-dependent association with survival and these associations are the basis for individualized prognostic and gene-based therapies. C2, Egfr, Prkcb, Igf2bp3, and Gdf10 had gender-dependent associations; Sox10, Rps20, Rab31, and Vav3 had race-dependent associations; Chi3l1, Prkcb, Polr2d, and Apool had therapy-dependent associations. Biological processes associated glioblastoma survival included morphogenesis, cell cycle, aging, response to stimuli, and programmed cell death.

CONCLUSIONS

Known biomarkers of glioblastoma survival were confirmed, and new general and clinical-dependent gene profiles were uncovered. The comparison of biomarkers across glioblastoma phases and functional analyses offered insights into the role of genes. These findings support the development of more accurate and personalized prognostic tools and gene-based therapies that improve the survival and quality of life of individuals afflicted by glioblastoma multiforme.

Pathway inhibition: emerging molecular targets for treating glioblastoma

Insights into the molecular pathogenesis of glioblastoma have not yet resulted in relevant clinical improvement. With standard therapy, which consists of surgical resection with concomitant temozolomide in addition to radiotherapy followed by adjuvant temozolomide, the median duration of survival is 12-14 months. Therefore, the identification of novel molecular targets and inhibitory agents has become a focus of research for glioblastoma treatment. Recent results of bevacizumab may represent a proof of principle that treatment with targeted agents can result in clinical benefits for patients with glioblastoma. This review discusses limitations in the existing therapy for glioblastoma and provides an overview of current efforts to identify molecular targets using large-scale screening of glioblastoma cell lines and tumor samples. We discuss preclinical and clinical data for several novel molecular targets, including growth factor receptors, phosphatidylinositol-3 kinase, SRC-family kinases, integrins, and CD95 ligand and agents that inhibit these targets, including erlotinib, enzastaurin, dasatinib, sorafenib, cilengitide, AMG102, and APG101. By combining advances in tumor screening with novel targeted therapies, it is hoped that new treatment options will emerge for this challenging tumor type.

Molecular heterogeneity in glioblastoma: therapeutic opportunities and challenges

Glioblastoma (GBM) has been recognized as a clinical and pathologic entity for more than a century. Throughout its history, its cells of origin have been in question. Its behavior is aggressive and despite decades of effort, median survival is just beginning to improve. Surgical techniques and radiotherapy schemas continue to be refined, but the most recent progress has been achieved through improved medical therapies. These are the result of both pharmacological advances and a deeper understanding of the biological characteristics of GBM. Due to a combination of its complex phenotype and organ-specific clinical manifestations, efforts to refine GBM treatment with targeted therapies largely have been frustrated. In this review, we discuss recent attempts to exploit new molecular insights, consider the reasons for slow progress in developing better treatments, and examine future therapeutic options.

Molecular markers in low-grade gliomas: predictive or prognostic?

PURPOSE

To investigate whether TP53 mutation, 1p/19q codeletions, O(6)-methylguanylmethyltransferase (MGMT) promoter methylation, and isocitrate dehydrogenase 1 (IDH1) mutation predict natural course of disease or response to radiotherapy or chemotherapy or both in low-grade glioma patients.

EXPERIMENTAL DESIGN

Cohort A consisted of 89 patients with diffuse astrocytoma World Health Organization (WHO) grade II (n = 40), oligoastrocytoma (n = 23), or oligodendroglioma (n = 26) who did not receive radiotherapy or chemotherapy after first operation and were monitored until progression [progressive disease (PD); n = 59] and beyond or until the end of follow-up (n = 30). Cohort B consisted of 50 patients with WHO grade II gliomas who received radiotherapy or chemotherapy at diagnosis. Tumors were analyzed for TP53 mutations, 1p/19q codeletions, MGMT promoter methylation, and IDH1 mutations.

RESULTS

Median progression-free survival (PFS) in cohort A was 4.1 years (95% CI: 3.1-5.1). No molecular marker was prognostic for PFS after surgery alone, using multivariate adjustment for histology, age, and extent of resection. IDH1 mutations were associated with prolonged survival from the diagnosis of PD in oligoastrocytomas (OA II)/oligodendrogliomas (O II) and with overall survival (OS) in all tumors. 1p/19q codeletion and IDH1 mutation were prognostic for PFS and OS in cohort B.

CONCLUSIONS

None of the parameters are sensitive prognostic biomarkers in WHO grade II glioma patients who do not receive radiotherapy or chemotherapy after surgery. Limitations of this study include the selection of patients with favorable outcome, the nonrandomized allocation of treatment, and the insufficient sample size to distinguish between effects of radiotherapy versus chemotherapy. Regardless of histology, IDH1 mutation status is the strongest prognostic marker for OS.

A distinct region of the MGMT CpG island critical for transcriptional regulation is preferentially methylated in glioblastoma cells and xenografts

O(6)-Methylguanine-DNA methyltransferase (MGMT) is a DNA repair protein that removes alkyl DNA adducts such as those induced by alkylating agents. Loss of MGMT expression through transcriptional silencing by hypermethylation of its CpG island (CGI) is found in diverse human cancers including glioblastomas. Glioblastomas that have MGMT methylation respond to temozolomide, an alkylating agent, resulting in improved survival. Consequently, assessment of MGMT methylation has become a therapy response and prognostic indicator. However, it is not clear whether the region of the MGMT CGI commonly analysed is the critical region involved in transcriptional control. We measured methylation levels at each CpG site for the entire MGMT CGI using bisulfite modification and pyrosequencing, and compared them with MGMT mRNA expression in glioblastoma cell lines, xenografts and normal brain tissues (41 samples). Two critical regions were identified (DMR1 and DMR2). DMR2 encompasses the commonly analysed region and was always methylated when DMR1 was methylated. A luciferase reporter assay showed that substitutions of several specific CpG sites within DMR2 significantly attenuated the promoter activity of the MGMT CGI. Our results indicate that several CpG sites within DMR2 play a critical role in the transcriptional control of MGMT, making DMR2 the optimal target for methylation testing. However, given the highly variable patterns of MGMT methylation associated with transcriptional silencing observed in this region among the tumours in this study, methylation levels need to be measured at a number of individual CpGs within DMR2 to confidently predict transcriptional silencing and thus sensitivity to alkylating agents.

Chromosome 7p11.2 (EGFR) variation influences glioma risk

While gliomas are the most common primary brain tumors, their etiology is largely unknown. To identify novel risk loci for glioma, we conducted genome-wide association (GWA) analysis of two case-control series from France and Germany (2269 cases and 2500 controls). Pooling these data with previously reported UK and US GWA studies provided data on 4147 glioma cases and 7435 controls genotyped for 424 460 common tagging single-nucleotide polymorphisms. Using these data, we demonstrate two statistically independent associations between glioma and rs11979158 and rs2252586, at 7p11.2 which encompasses the EGFR gene (population-corrected statistics, P(c) = 7.72 × 10(-8) and 2.09 × 10(-8), respectively). Both associations were independent of tumor subtype, and were independent of EGFR amplification, p16INK4a deletion and IDH1 mutation status in tumors; compatible with driver effects of the variants on glioma development. These findings show that variation in 7p11.2 is a determinant of inherited glioma risk.