Dataset Information

Spatial and temporal evolution of distal 10q deletion, a prognostically unfavorable event in diffuse low-grade gliomas

ABSTRACT: Background: The disease course of patients with diffuse low-grade glioma is notoriously unpredictable. Temporal and spatially distinct samples may provide insight into the evolution of clinically relevant copy number aberrations (CNAs). The purpose of this study is to identify CNAs that are indicative of aggressive tumor behaviour and can thereby complement the prognostically favorable 1p/19q co-deletion. Results: Genome-wide, 50 base pair single-end, sequencing was performed to detect CNAs in a clinically well-characterized cohort of 98 formalin-fixed paraffin-embedded low-grade gliomas. CNAs are correlated with overall survival as an endpoint. Seventy-five additional samples from spatially distinct regions and paired recurrent tumors of the discovery cohort were analysed to interrogate the intratumoral heterogeneity and spatial evolution. Loss of 10q25.2-qter is a frequent subclonal event and significantly correlates with an unfavorable prognosis. A significant correlation is furthermore observed in a validation set of 126 and confirmation set of 184 patients. Loss of 10q25.2-qter arises in a longitudinal manner in paired recurrent tumor specimens, whereas the prognostically favorable 1p/ 19q co-deletion is the only CNA that is stable across spatial regions and recurrent tumors. Conclusions: CNAs in low-grade gliomas display extensive intratumoral heterogeneity. Distal loss of 10q is a late onset event and a marker for reduced overall survival in low-grade glioma patients. Intratumoral heterogeneity and higher frequencies of distal 10q loss in recurrences suggest this event is involved in outgrowth to the recurrent tumor.

PROVIDER: EGAS00001000643 | EGA |

REPOSITORIES: EGA

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Publications

Evolution of DNA repair defects during malignant progression of low-grade gliomas after temozolomide treatment.

van Thuijl Hinke F HF Mazor Tali T Johnson Brett E BE Fouse Shaun D SD Aihara Koki K Hong Chibo C Malmström Annika A Hallbeck Martin M Heimans Jan J JJ Kloezeman Jenneke J JJ Stenmark-Askmalm Marie M Lamfers Martine L M ML Saito Nobuhito N Aburatani Hiroyuki H Mukasa Akitake A Berger Mitchell S MS Söderkvist Peter P Taylor Barry S BS Molinaro Annette M AM Wesseling Pieter P Reijneveld Jaap C JC Chang Susan M SM Ylstra Bauke B Costello Joseph F JF

Acta neuropathologica 20150228 4

Temozolomide (TMZ) increases the overall survival of patients with glioblastoma (GBM), but its role in the clinical management of diffuse low-grade gliomas (LGG) is still being defined. DNA hypermethylation of the O (6) -methylguanine-DNA methyltransferase (MGMT) promoter is associated with an improved response to TMZ treatment, while inactivation of the DNA mismatch repair (MMR) pathway is associated with therapeutic resistance and TMZ-induced mutagenesis. We previously demonstrated that TMZ tr ...[more]

PMID: 25724300

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Project description:Purpose: The most clearly established genetic hallmark in oligodendroglial tumors (OTs) is the combined loss of 1p/19q, a molecular alteration characteristic of tumors responding to therapy. Markers of tumoral progression have not yet been studied. Experimental Design: Novel markers of tumoral progression in OTs were sought through gene expression profiling analysis. Results: Unsupervised hierarchical cluster analysis classified OTs into two main groups associated with tumoral grade, independent of histological subtype and 1p/19q status. Differential gene expression analysis between low- and high-grade OTs revealed that only cell cycle-related genes were significantly upregulated in high-grade OTs. Among the deregulated genes, NDRG2 downregulation was detected in high-grade OTs with combined loss of 1p/19q. Expression analysis revealed low transcript levels of NDRG2 relative to non-tumoral brain tissue in 45% (9/20) of high-grade OTs. Furthermore, the low transcript levels of NDRG2 were significantly associated with a worse clinical outcome in patients. Transcript levels of NDRG2 were associated with promoter hypermethylation, which was detected in 38.4% (10/26) of high-grade OTs. The treatment of glioma cell lines T98 and LN18 with demethylating agents increased the mRNA expression levels of NDRG2 relative to the control cell line. Additionally, cell proliferation was significantly reduced and cell cycle was arrested in G1 phase after treatment with demethylating agents. Conclusions: Taken together, our results suggest that NDRG2 is a candidate tumor suppressor gene in OTs whose inactivation could be involved in tumoral progression and worse patient survival. The microarray study involved 28 glioma samples including oligodendrogliomas and oligoastrocytomas WHO grade II and III. Six non-tumoral brain tissues were used as controls, two of which were purchased from Stratagene (La Jolla, CA) and Clontech (Mountain View, CA). RNAs from several cell lines (Universal Human RNA, Stratagene, La Jolla, CA) was used as a standard reference in all hybridizations

Project description:The outcome of patients with anaplastic gliomas varies considerably depending on histology and single molecular markers such as codeletion of 1p/19q and mutations of the isocitrate dehydrogenase (IDH) gene. Whether a molecularly-based classification of anaplastic gliomas based on large scale genomic or epigenomic analyses is superior to histopathology, may reflect distinct biological subtypes, predict outcome and guide therapy decisions had yet to be determined. Epigenome-wide DNA methylation analysis, which also allows for the detection of copy-number aberrations, was performed in a cohort of 228 patients with anaplastic gliomas (astrocytomas, oligoastrocytomas and oligodendrogliomas), including 115 patients of the NOA-04 trial. We further compared these tumors with a group of 55 glioblastomas. Unsupervised clustering demonstrated two main groups based on IDH mutation status: CpG island methylator phenotype (CIMP) positive (77.5%) or negative (22.5%). CIMP+ (IDH mutant) tumors showed a further separation based on copy-number status of chromosome arms 1p and 19q, but not based on histopathology. CIMP- (IDH wild type) tumors on the other hand showed hallmark copy-number alterations of glioblastomas. These tumors clustered together with CIMP- glioblastomas without forming separate groups based on WHO grade. There was no Tumor classification based on CIMP and 1p/19q status was significantly associated with survival allowing a better prediction of outcome than the current histopathological classification alone: Patients with CIMP+ tumors with 1p/19q codeletion had the best prognosis, followed by patients with CIMP+ but intact 1p/19q status. Patients with CIMP- anaplastic gliomas had the worst prognosis. Collectively, our data suggest that anaplastic gliomas can be grouped into three molecular subtypes with clear association to underlying biology and clinical outcome based on IDH and 1p/19q status. The data do not provide a molecular basis for the diagnosis of anaplastic oligoastrocytoma.

Dataset Information

Spatial and temporal evolution of distal 10q deletion, a prognostically unfavorable event in diffuse low-grade gliomas

Publications

Evolution of DNA repair defects during malignant progression of low-grade gliomas after temozolomide treatment.

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