Tumors with histological features of pilocytic astrocytoma (PA), but with increased mitotic activity and additional high-grade features (particularly microvascular proliferation and palisading necrosis) have often been designated anaplastic pilocytic astrocytomas. The status of these tumors as a separate entity has not yet been conclusively demonstrated and molecular features have only been partially characterized. We performed DNA methylation profiling of 102 histologically defined anaplastic pilocytic astrocytomas. T-distributed stochastic neighbor-embedding (t-SNE) and hierarchical clustering analysis of these 102 cases against 158 reference cases from 12 glioma reference classes revealed that a subset of 83 of these tumors share a common DNA methylation profile that is distinct from the reference classes. These 83 tumors were thus denominated DNA methylation class anaplastic astrocytoma with piloid features (MC AAP). The 19 remaining tumors were distributed amongst the reference classes, with additional testing confirming the molecular diagnosis in most cases. Median age of patients with MC AAP was 41.5 years. The most frequent localization was the posterior fossa (74%). Deletions of CDKN2A/B (66/83, 80%), MAPK pathway gene alterations (49/65, 75%, most frequently affecting NF1, followed by BRAF and FGFR1) and mutations of ATRX or loss of ATRX expression (33/74, 45%) were the most common molecular alterations. All tumors were IDH1/2 wildtype. The MGMT promoter was methylated in 38/83 tumors (45%). Outcome analysis confirmed an unfavorable clinical course in comparison to PA, but better than IDH wildtype glioblastoma. In conclusion, we show that a subset of histologically defined anaplastic pilocytic astrocytomas forms a separate DNA methylation cluster, harbors recurrent alterations in MAPK pathway genes in combination with alterations of CDKN2A/B and ATRX, affects patients who are on average older than those diagnosed with PA and has an intermediate clinical outcome.
Purpose: Rechallenge with temozolomide (TMZ) at first progression of glioblastoma after temozolomide chemoradiotherapy (TMZ/RT!TMZ) has been studied in retrospective and single-arm prospective studies, applying temozolomide continuously or using 7/14 or 21/28 days schedules. The DIRECTOR trial sought to show superiority of the 7/14 regimen.Experimental Design: Patients with glioblastoma at first progression after TMZ/RT!TMZ and at least two maintenance temozolomide cycles were randomized to Arm A [one week on (120 mg/m 2 per day)/one week off] or Arm B [3 weeks on (80 mg/m 2 per day)/one week off]. The primary endpoint was median timeto-treatment failure (TTF) defined as progression, premature temozolomide discontinuation for toxicity, or death from any cause. O 6 -methylguanine DNA methyltransferase (MGMT) promoter methylation was prospectively assessed by methylationspecific PCR.Results: Because of withdrawal of support, the trial was prematurely closed to accrual after 105 patients. There was a similar outcome in both arms for median TTF [A: 1.8 months; 95% confidence intervals (CI), 1.8-3.2 vs. B: 2.0 months; 95% CI, 1.8-3.5] and overall survival [A: 9.8 months (95% CI, 6.7-13.0) vs. B: 10.6 months (95% CI, 8.1-11.6)]. Median TTF in patients with MGMT-methylated tumors was 3.2 months (95% CI, 1.8-7.4) versus 1.8 months (95% CI, 1.8-2) in MGMT-unmethylated glioblastoma. Progression-free survival rates at 6 months (PFS-6) were 39.7% with versus 6.9% without MGMT promoter methylation.Conclusions: Temozolomide rechallenge is a treatment option for MGMT promoter-methylated recurrent glioblastoma. Alternative strategies need to be considered for patients with progressive glioblastoma without MGMT promoter methylation. Clin Cancer Res; 21(9); 2057-64. Ó2015 AACR.
Glioblastoma (GBM) is a highly aggressive brain tumour, where patients respond poorly to radiotherapy and exhibit dismal survival outcomes. The mechanisms of radioresistance are not completely understood. However, cancer cells with an immature stem-like phenotype are hypothesised to play a role in radioresistance. Since the progenitor marker neuron-glial-2 (NG2) has been shown to regulate several aspects of GBM progression in experimental systems, we hypothesised that its expression would influence the survival of GBM patients. Quantification of NG2 expression in 74 GBM biopsies from newly diagnosed and untreated patients revealed that 50% express high NG2 levels on tumour cells and associated vessels, being associated with significantly shorter survival. This effect was independent of age at diagnosis, treatment received and hypermethylation of the O6-methylguanine methyltransferase (MGMT) DNA repair gene promoter. NG2 was frequently co-expressed with nestin and vimentin but rarely with CD133 and the NG2 positive tumour cells harboured genetic aberrations typical for GBM. 2D proteomics of 11 randomly selected biopsies revealed upregulation of an antioxidant, peroxiredoxin-1 (PRDX-1), in the shortest surviving patients. Expression of PRDX-1 was associated with significantly reduced products of oxidative stress. Furthermore, NG2 expressing GBM cells showed resistance to ionising radiation (IR), rapidly recognised DNA damage and effectuated cell cycle checkpoint signalling. PRDX-1 knockdown transiently slowed tumour growth rates and sensitised them to IR in vivo. Our data establish NG2 as an important prognostic factor for GBM patient survival, by mediating resistance to radiotherapy through induction of ROS scavenging enzymes and preferential DNA damage signalling.Electronic supplementary materialThe online version of this article (doi:10.1007/s00401-011-0867-2) contains supplementary material, which is available to authorized users.
We explored the clinical and pathological impact of epidermal growth factor receptor (EGFR) extracellular domain missense mutations. Retrospective assessment of 260 de novo glioblastoma patients revealed a significant reduction in overall survival of patients having tumors with EGFR mutations at alanine 289 (EGFR). Quantitative multi-parametric magnetic resonance imaging analyses indicated increased tumor invasion for EGFR mutants, corroborated in mice bearing intracranial tumors expressing EGFR and dependent on ERK-mediated expression of matrix metalloproteinase-1. EGFR tumor growth was attenuated with an antibody against a cryptic epitope, based on in silico simulation. The findings of this study indicate a highly invasive phenotype associated with the EGFR mutation in glioblastoma, postulating EGFR as a molecular marker for responsiveness to therapy with EGFR-targeting antibodies.
The epidermal growth factor receptor vIII mutant (EGFRvIII) is found in~50% of all EGFR-amplified glioblastomas and constitutes a tumor-specific therapeutic target. To assess molecular testing approaches and the prognostic role of EGFRvIII in patients treated according to current standards of care, we compared different EGFRvIII detection methods and correlated EGFRvIII status with outcome in a prospective patient cohort of the German Glioma Network. In total, 184 newly diagnosed glioblastoma patients were investigated for EGFR amplification and for expression of EGFR and EGFRvIII by immunohistochemistry. Further, the EGFRvIII status was additionally studied by multiplex ligation-dependent probe amplification (MLPA) analysis and reverse transcription-PCR (RT-PCR). Immunohistochemistry demonstrated EGFRvIII in 34 of 184 patients (18%). RT-PCR or MLPA analysis detected four additional EGFRvIII-positive patients. Overall, RT-PCR and immunohistochemistry were more sensitive for EGFRvIII detection than MLPA. EGFRvIII status was not associated with progression-free and overall survival. EGFRvIII also had no prognostic significance in the subgroup of patients who were free from progression after concomitant radiochemotherapy and thus would be eligible for the ongoing ACT IV EGFRvIII vaccination trial. Age, extent of resection and O 6 -methylguanine DNA methyltransferase (MGMT) promoter methylation status appeared to be less prognostic in EGFRvIII-positive
Loss of heterozygosity (LOH) on chromosomal arms 1p and 19q is the most common genetic alteration in oligodendroglial tumors and associated with response to radio-and chemotherapy as well as favorable prognosis. Using microsatellite analysis, we previously identified the chromosomal regions 1p36. 22-p36.31 and 19q13.3, as candidate tumor suppressor gene regions being commonly deleted in these tumors. To identify genes within these regions that are downregulated in oligodendroglial tumors with LOH 1p/19q, we performed cDNA microarray-based RNA expression profiling of 35 gliomas with known allelic status on 1p and 19q, including 7 oligodendrogliomas and 8 diffuse astrocytomas of World Health Organization (WHO) grade II, as well as 14 anaplastic oligodendrogliomas and 6 anaplastic oligoastrocytomas of WHO grade III. The microarrays used for expression profiling carried 7,000 gene-specific cDNAs, with complete coverage of the genes located in 1p36. 13-p36.31 and 19q13.2-q13.33. Microarray analysis identified 8 genes from these regions (MGC4399, SRM, ICMT, RPL18, FTL, ZIN, FLJ10781 and DBP), which all showed significantly lower expression in 1p/19q-deleted gliomas when compared to gliomas without 1p/19q losses. Quantitative real-time reverse transcription-PCR analyses were performed for the MGC4399, ICMT and RPL18 genes and confirmed the microarray findings. In addition, we found that the cytosolic phospholipase A2 (PLA2G4C) gene at 19q13.3 demonstrated significantly lower expression in anaplastic oligodendrogliomas (WHO grade III) when compared to well-differentiated oligodendrogliomas (WHO grade II). Taken together, our study provides a set of interesting novel candidate genes that may play important roles in the pathogenesis of oligodendroglial tumors. ' 2006 Wiley-Liss, Inc.Key words: gene expression profiling; loss of heterozygosity; DNA microarray; oligodendroglioma; tumor suppressor gene Gliomas are the most common primary brain tumors and constitute a heterogeneous group of neoplasms with respect to morphological appearance, biological behavior, genetic alterations, as well as response to therapy and clinical outcome. Astrocytic tumors are the most common gliomas, with glioblastoma multiforme being the most malignant and, at the same time, most frequent astrocytic tumor. In contrast, oligodendroglial tumors, comprising oligodendrogliomas and mixed oligoastrocytomas, are estimated to account for only 5-18% of all gliomas.1 Molecular genetic studies have revealed that the development of astrocytic and oligodendroglial gliomas is caused by distinct genetic alterations, which may be important for the refinement of glioma classification based on genomic profiling.2 The genetic hallmark of oligodendroglial tumors is the combined loss of heterozygosity (LOH) on chromosomal arms 1p and 19q (LOH 1p/19q), which is rare in astrocytic tumors but found in up to 80% of oligodendrogliomas and 50% of oligoastrocytomas.3 Importantly, LOH 1p/19q has emerged as an independent predictive marker of better response to radio-and ...
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