Supratentorial Ependymoma Research Articles

A De Novo Mouse Model of C11orf95-RELA Fusion-Driven Ependymoma Identifies Driver Functions in Addition to NF-κB

SUMMARYThe majority of supratentorial ependymomas (ST-ependymomas) have few mutations but frequently display chromothripsis of chromosome 11q that generates a fusion between C11orf95 and RELA (RELAFUS). Neural stem cells transduced with RELAFUS ex vivo form ependymomas when implanted in the brain. These tumors display enhanced NF-κB signaling, suggesting that this aberrant signal is the principal mechanism of oncogenesis. However, it is not known whether RELAFUS is sufficient to drive de novo ependymoma tumorigenesis in the brain and, if so, whether these tumors also arise from neural stem cells. We show that RELAFUS drives ST-ependymoma formation from periventricular neural stem cells in mice and that RELAFUS-induced tumorigenesis is likely dependent on a series of cell signaling pathways in addition to NF-κB.

A Mouse Ependymoma Model Provides Molecular Insights into Tumor Formation

Ozawa etal. present a murine tumor model resembling the most frequent molecular group of human supratentorial ependymoma, ST-EPN-RELA. Their model shows RELA-fusion-based de novo ependymoma tumorigenesis in the forebrain derived from neural stem cells.

Establishing a Preclinical Multidisciplinary Board for Brain Tumors.

Purpose: Curing all children with brain tumors will require an understanding of how each subtype responds to conventional treatments and how best to combine existing and novel therapies. It is extremely challenging to acquire this knowledge in the clinic alone, especially among patients with rare tumors. Therefore, we developed a preclinical brain tumor platform to test combinations of conventional and novel therapies in a manner that closely recapitulates clinic trials.Experimental Design: A multidisciplinary team was established to design and conduct neurosurgical, fractionated radiotherapy and chemotherapy studies, alone or in combination, in accurate mouse models of supratentorial ependymoma (SEP) subtypes and choroid plexus carcinoma (CPC). Extensive drug repurposing screens, pharmacokinetic, pharmacodynamic, and efficacy studies were used to triage active compounds for combination preclinical trials with "standard-of-care" surgery and radiotherapy.Results: Mouse models displayed distinct patterns of response to surgery, irradiation, and chemotherapy that varied with tumor subtype. Repurposing screens identified 3-hour infusions of gemcitabine as a relatively nontoxic and efficacious treatment of SEP and CPC. Combination neurosurgery, fractionated irradiation, and gemcitabine proved significantly more effective than surgery and irradiation alone, curing one half of all animals with aggressive forms of SEP.Conclusions: We report a comprehensive preclinical trial platform to assess the therapeutic activity of conventional and novel treatments among rare brain tumor subtypes. It also enables the development of complex, combination treatment regimens that should deliver optimal trial designs for clinical testing. Postirradiation gemcitabine infusion should be tested as new treatments of SEP and CPC. Clin Cancer Res; 24(7); 1654-66. ©2018 AACR.

Supratentorial Cortical Ependymomas: A Retrospective Series of 13 Cases at a SingleCenter.

Cortical ependymomas (CEs), supratentorial ependymomas that selectively involve the cerebral cortex, are relatively rare neoplasms that have not been extensively described. The purpose of our study was to identify the clinical features, radiologic characteristics, and treatment of a series of such tumors. Thirteen patients with CEs from our hospital were included in this study. Epidemiologic characteristics, clinical features, imaging findings, treatment methods, and clinical outcomes were reviewed retrospectively. The patients consisted of 7 men and 6 women with mean age of 31.1 ± 23.2 years (range, 4-74 years). The most common clinical manifestation was seizure (n= 11; 85%), followed by headache (n= 2; 15%). None of the tumors were incidentally detected. Eight CEs were located in the right hemisphere and 5 in the left side. The 2 most common tumor locations were the frontal (n=5; 38%) and parietal lobe (n= 5; 38%). All patients underwent surgical resection. Gross total resection was achieved in 12 patients (92%), and subtotal resection was performed in 1 patient (8%). Ten of the 11 patients who presented with seizure are seizure-free after surgery (91% seizure-free rate). According to the World Health Organization classification system, 9 tumors (69%) were Grade II (ependymoma) and 4 (31%) were Grade III (anaplastic ependymoma). The mean follow-up was 52 months (range, 20-88 months). No recurrence was observed in patients with Grade II CEs. Of 4 patients with Grade III CEs, 2 (50%) suffered from tumor recurrence after initial treatment. CEs are a rare subset of supratentorial ependymomas that selectively involve the cerebral cortex. Most CEs are low grade and present with seizures. Anaplastic CEs show a greater recurrence rate and a relatively poor prognosis. Gross total resection with or without adjuvant radiotherapy is currently the optimal treatment for CEs. CEs seem to have a more favorable prognosis than other supratentorial ependymomas.

C11orf95-RELA fusions and upregulated NF-KB signalling characterise a subset of aggressive supratentorial ependymomas that express L1CAM and nestin.

Ependymomas (EPN) show site specific genetic alterations and a recent DNA methylation profiling study identified nine molecular subgroups. C11orf95-RELA and YAP1 fusions characterise the RELA and YAP1 molecular subgroups, respectively, of supratentorial (ST)-EPNs. Current guidelines recommend molecular subgrouping over histological grade for accurate prognostication. Clinicopathological features of ST-EPNs in correlation with C11orf95-RELA and YAP1 fusions have been assessed in only few studies. We aimed to study these fusions in EPNs, and identify diagnostic and prognostic markers. qRT-PCR and Sanger Sequencing for the detection of C11orf95-RELA,YAP1-MAMLD1 and YAP1-FAM118B fusion transcripts, gene expression analysis for NFKB1, and immunohistochemistry for p53,MIB-1,nestin,VEGF, and L1CAM were performed. 88 EPNs (10-Grade I and 78-Grade II/III) from all sites were included. RELA fusions were unique to Grade II/III ST-EPNs, detected in 81.4% (22/27) and 18.5% (5/27) of pediatric and adult ST-EPNs respectively. ST-EPNs harbouring RELA fusions showed frequent grade III histology (81.5%), clear cell morphology (70.3%), upregulated NFKB1 expression, MIB-1 labelling indices (LI) ≥ 10% (77.8%), and immunopositivity for nestin (95.7%), VEGF (72%), L1CAM (79%), and p53 (64%). Presence ofRELA fusions, L1CAM immunopositivity and MIB-1 LI ≥ 10% associated with poor outcome. L1CAM showed 81% concordance with RELA fusions. YAP1-MAMLD1 fusion was identified in a single RELA fusion negative adult anaplastic ST-EPN. RELA fusions are frequent in ST-EPNs and associate with poor outcome. L1CAM is a surrogate immunohistochemical marker. RELA fusion positive ST-EPNs strongly express nestin indicating increased stemness. Further evaluation of the interactions between NFKB and stem cell pathways is warranted.

Supra-Tentorial Cortical Ependymoma in an Adult: Case Report and Review of the Literature

Supratentorial cortical ependymoma is a rare primary brain tumor in adults. Only 50 cases are reported in the literature including pediatric and adult patients. We report a 30-year-old male with sensory-type seizures who was found to have a right posterior frontal cortical lesion with large cystic component. The lesion was resected completely and histopathology and immunohistochemistry examinations confirmed anaplastic ependymoma WHO grade III. The patient received radiotherapy treatment post-surgery, and he was tumor free one year after treatment.

Supratentorial giant cell ependymoma with extensive tumour cell vacuolization and calcification

Supratentorial giant cell ependymoma with extensive tumour cell vacuolization and calcification

Therapeutic targeting of ependymoma as informed by oncogenic enhancer profiling.

SUMMARYGenomic sequencing has driven precision-based oncology therapy; however, genetic drivers remain unknown or non-targetable for many malignancies, demanding alternative approaches to identify therapeutic leads. Ependymomas are chemotherapy-resistant brain tumours, which, despite genomic sequencing, lack effective molecular targets. Intracranial ependymomas are segregated based on anatomical location – supratentorial region (ST) or posterior fossa (PF) – and further divided into distinct molecular subgroups that reflect differences in age of onset, gender predominance, and response to therapy1–3. The most common and aggressive subgroup, Posterior Fossa Ependymoma Group A (PF-EPN-A), occurs in young children and appears to lack recurrent somatic mutations2. Conversely, Posterior Fossa Ependymoma Group B (PF-EPN-B) tumours display frequent large-scale copy number gains and losses yet favourable clinical outcomes1,3. Greater than 70% of supratentorial ependymomas are defined by highly recurrent gene fusions in the NFκB subunit RELA (ST-EPN-RELA), and less frequently involve fusion of the gene encoding the transcriptional activator YAP1 (ST-EPN-YAP1).1,3,4 Subependymomas, a distinct histologic variant, can also be found within the ST and PF compartments accounting for the majority of tumours in the molecular subgroups ST-EPN-SE and PF-EPN-SE, respectively1. Here, we mapped active chromatin landscapes in 42 primary ependymomas in two non-overlapping primary ependymoma cohorts with the goal of identifying essential super enhancer associated genes on which tumour cells were dependent. Enhancer regions revealed putative oncogenes, molecular targets, and pathways, which when subjected to small molecule inhibitor or shRNA treatment, diminished proliferation of patient-derived neurospheres and increased survival in mouse models of ependymomas. Through profiling of transcriptional enhancers, our study provides a framework for target and drug discovery in other cancers recalcitrant to therapeutic development because of their lack of known genetic drivers.

Aggressive Supratentorial Ependymoma, RELA Fusion-Positive with Extracranial Metastasis: A Case Report.

Ependymoma is the third most common pediatric primary brain tumor. Ependymomas are categorized according to their locations and genetic abnormalities, and these two parameters are important prognostic factors for patient outcome. For supratentorial (ST) ependymomas, RELA fusion-positive ependymomas show a more aggressive behavior than YAP1 fusion-positive ependymomas. Extracranial metastases of intra-axial neuroepithelial tumors are extremely rare. In this paper, we report a case of aggressive anaplastic ependymoma arising in the right frontoparietal lobe, which had genetically 1q25 gain, CDKN2A homozygous deletion, and L1CAM overexpression. The patient was a 10-year-old boy who underwent four times of tumor removal and seven times of gamma knife surgery. Metastatic loci were scalp and temporalis muscle overlying primary operation site, lung, liver, buttock, bone, and mediastinal lymph nodes. He had the malignancy for 10 years and died. This tumor is a representative case of RELA fusion-positive ST ependymoma, showing aggressive behavior.

Ectopic Solitary Cortical Anaplastic Ependymoma in a Child: A Rare Entity with Short Illustrative Review

AbstractEpendymomas are usually infratentorial and intraventricular. They originate from the ependymal cell lining of the ventricles. Cortical extraventricular supratentorial ependymomas are rare and fewer than 15 cases are reported worldwide. In pediatric age group, seven cases are reported. We report a rare case of 4-year-old boy with right frontoparietal anaplastic ependymoma who underwent gross total excision of lesion.

135 Pediatric Supratentorial Ependymoma

Abstract INTRODUCTION Recent molecular analyses support a behavioral and clinical distinction between supratentorial and infratentorial ependymomas, with supratentorial tumors, in general, having a more favorable prognosis. The goal of this study was todescribe our experience managing supratentorial ependymoma in children. METHODS A prospectively maintained neurooncology database was queried to identify cases ofsupratentorial ependymoma treated atSt Jude Children's Research Hospital (SJCRH) and LeBonheur from 1990 through December 31, 2014. Clinical, operative, and radiographic information were reviewed. Outcome measures, determined by review of clinic notes and subsequent imaging, included extent of resection, progression free survival (PFS), overall survival (OS), recurrence of disease and method of post-failure treatment, seizures, requirement of anti-seizure medications, hydrocephalus requiring shunt placement, and death.Detection ofthe C11or95-RELA fusion or rearrangement was performed using iFISH in those patients whose tumor tissue was still available. RESULTS >Seventy-four cases (42% male) of supratentorial ependymoma were identified. Median age at diagnosis was 6.8 years. In total, 59 (79.7%) of 74 patients underwent gross total resection (GTR). Overall survival was a median of 7.4 years. Fifteen patients died of disease. Progression free survival was a median of 3.6 years. Eighty percent of those children whose initial resection was subtotal developed recurrence compared to 50.8% in those who had a GTR. For those patients that recurred, all 42 received further treatment, including further resection, chemotherapy and radiation. Molecular analysis was available for 52 patients (70.3%). Age less than 3, gross total resection, and tumor grade were not associated with improved PFS or OS. Absence of C11-or95-RLEA fusion was associated with a significantly worse PFS, although OS was similar. CONCLUSION Supratentorial ependymoma often have a more favorable prognosis compared toinfratentorial variants. Like many pediatric tumors, supratentorial ependymomas can bestratified based on clinical, surgical and possibly molecular variables.

Recent Advances in the Classification and Treatment of Ependymomas.

Ependymomas are a subgroup of ependymal glia-derived neoplasms that affect children as well as adults. Arising within any CNS compartment, symptoms at presentation can range from acute onset due to increased intracranial pressure to insidious myelopathy. The overall survival (OS) outcomes in adult patients across the subgroups is heterogeneous with subependymoma having an excellent prognosis often even in the absence of any treatment, whereas supratentorial ependymomas tend to be higher grade in nature and may have an OS of 5years despite gross total resection and adjuvant radiation. The rarity of ependymal tumors, together still only representing 1.8% of all primary CNS tumors, has been a long-standing challenge in defining optimal treatment guidelines via prospective randomized trials. Retrospective studies have supported maximal safe resection, ideally gross total resection, as the optimal treatment with adjuvant radiation therapy proffering additional tumor control. The evidence for efficacy of chemotherapy and targeted agents in adult ependymomas is minimal. Recent investigations of the molecular, genetic, and DNA methylation profiles of ependymal tumors across all age groups and CNS compartments have identified distinct oncogenic gene products as well as nine molecular subgroups correlating with similar outcomes. The 2016 World Health Organization of Tumors of the Central Nervous System update addresses some of these findings, although their clinical significance has not yet been fully validated. There are inconsistent survival outcomes in retrospective studies for ependymomas graded as II versus III, bringing into question the validity of histologic grading which is subject to high interobserver variability in part due to inconsistent application of mitotic count parameters.

Abstract CT051: Tumor treating fields in pediatric recurrent high-grade glioma and ependymoma

Abstract Background Recurrent or progressive pediatric CNS tumors have a poor prognosis under current treatment regimens. For children with high-grade gliomas (HGG), once progression occurs, most patients cannot be cured, and median survival remains < 1-2 years; overall survival of recurrent/progressive ependymoma is also poor in children. Tumor Treating Fields (TTFields) is an anti-mitotic cancer therapy for the treatment of recurrent (supratentorial) glioblastoma (GB).) A phase 3 clinical trial comparing TTFields monotherapy with physician’s choice chemotherapy in adult patients with recurrent GB demonstrated comparable overall survival and improved quality of life. In this multicenter feasibility trial we plan to examine the feasibility and device-related toxicity of TTFields in children with supratentorial HGG and ependymoma. The secondary objectives include: response rate, Event-Free Survival, compliance on use of device and Quality of Life (QoL) of tehe children (aged 8+) and families. Methods The Optune device will be worn ≥ 18 hours/day for at least 23 days out of 28 days of cycle one. Patients will have Brain MRI with and without contrast performed prior to therapy, after cycles 2, 4, 6, 9, then every 3 cycles thereafter until time of progression or completion of treatment. For those patients who complete at least 9 cycles of therapy, an MRI will be performed every 3 cycles for 2 years then every 4 months after completion of treatment.Treatment may continue up to 26 cycles pending observed benefit and safety. A sample size of 20 patients is needed with an interim analysis conducted after the first 11 patients. Kaplan-Meier estimates of EFS for all eligible patients who use the device for < 1 day will be provided separately for the HGG and Ependymomahistology-based cohorts. We will also estimate the rates of confirmed sustained objective responses (CR+PR) observed during treatment. All PROMIS and Neuro-QoL scores will be reported using T-score matrix (mean=50 and SD=10). The projected accrual rate is 1.5-2.5 patients per month. Patients will be followed for 2 years. Citation Format: Stewart Goldman, Arzu Onar-Thomas, Ira Dunkel, Eugene Hwang. Tumor treating fields in pediatric recurrent high-grade glioma and ependymoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT051. doi:10.1158/1538-7445.AM2017-CT051

Abstract 705: Elucidating pediatric brain tumor pathophysiology by assessing signal transduction pathway activation

Abstract A major problem in pediatric neuro-oncology is lack of insight into underlying tumor biology, making treatment with targeted therapy challenging for this group of patients. To enable targeted therapy choice, understanding of underlying signal transduction pathway activity is required, as well as availability of appropriate diagnostic tests to predict therapy response. We have developed a novel method to identify activity of the ER, AR, HH, Wnt, TGFbeta, NFκB, and PI3K signal transduction pathways in an individual tissue sample. Our method is based on measuring mRNA levels of the pathway transcription factor target genes and interpreting these expression levels using a knowledge-based Bayesian network computational model which infers the probability of activity of the respective transcription factor (Verhaegh et al, Cancer Res. 2014). Public patient sample datasets from the GEO database were used to investigate pathway activation in pediatric brain tumors. In normal brain tissue from medulla, cerebellum, cerebral cortex and thalamus (GSE50161), pathway analysis showed no significant oncogenic pathway activation. Observed pathway activity in medulloblastoma was strongly correlated with known pathway-activating mutations, which was used as initial validation of these models for use in pediatric brain tumor diagnostics. In ependymoma (GSE66354), three distinct subtypes were analyzed: infratentorial posterior fossa A (PFA), PFB and supratentorial. These tumors are known to have a subtype-dependent prognosis; mainstay of therapy is surgery and radiation. Tumor driving pathway identification in pediatric ependymoma using mutation analysis is usually not helpful because epigenetic mechanisms prevail (Mack et al, Brain Pathology 2013). Using our pathway activity analysis, we find remarkable differences between different types of ependymoma with respect to signal transduction pathway activity. For PFA we find high NFκB and Wnt pathway activity. The dominant NFκB activity is in agreement with the described inflammatory phenotype. On the other hand, for PFB we find low NFκB and Wnt pathway activity. Finally, for supratentorial ependymoma we find almost all samples to have an active Hedgehog and Wnt pathway. We also analyzed multiple other pediatric tumors for pathway activity, for which data will be presented. The above pathway activity results provide highly interesting leads for targeted therapy selection, and we expect that such pathway analysis will have clinical utility in a neoadjuvant setting to reduce tumor size prior to surgery, and possibly also in an adjuvant setting to prevent recurrences. Citation Format: Laurent Holtzer, Wim Verhaegh, Anja Van de Stolpe. Elucidating pediatric brain tumor pathophysiology by assessing signal transduction pathway activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 705. doi:10.1158/1538-7445.AM2017-705

Extra-axial ependymoma mimicking a meningioma

Supratentorial ependymomas are rare and are usually intra axial in location. We report a case of extra axial supra tentorial ependymoma in a girl which mimicked a falcine meningioma. Imaging, pathological features and management are described in this case report along with review of the literature. The possible origin of these tumors is discussed.

RARE-03. EPENDYMOMAS ARISING OUTSIDE OF THE CENTRAL NERVOUS SYSTEM: A CASE SERIES

Extracranial and extraspinal ependymomas are extremely rare tumors mostly published in the literature as case reports. Our institutional database was screened for patients with extra CNS ependymomas over a 25 year period. Eight patients with extra CNS ependymoma were identified. Five cases originated in the sacrum or subcutaneous sacral area, and the other 3 cases originating in the breast, lung and adnexa of the uterus. By histology, most cases were myxopapilary ependymomas (5 cases), 2 cases were grade 2 ependymoma and 1 case was an anaplastic ependymoma. Metastases occurred in 6 cases and 3 patients died due to progressive disease. Most cases required surgery, radiation and chemotherapy. Extra CNS ependymomas are very rare tumors that tend to metastasize, even though most cases are histologically classified as low grade ependymomas, suggesting that the tumor biology does not correlate with conventional histologic findings. Future plans include molecular phenotyping to determine if these rare cancers are molecular similar to the recent findings from infratentorial, supratentorial ependymomas or the metabolic profile of classic spinal myxopapillary ependymoma.

Novel fusion genes and chimeric transcripts in ependymal tumors

We have previously identified two ALK rearrangements in a subset of ependymal tumors using a combination of cytogenetic data and RNA sequencing. The aim of this study was to perform an unbiased search for fusion transcripts in our entire series of ependymal tumors. Fusion analysis was performed using the FusionCatcher algorithm on 12 RNA-sequenced ependymal tumors. Candidate transcripts were prioritized based on the software's filtering and manual visualization using the BLAST (Basic Local Alignment Search Tool) and BLAT (BLAST-like alignment tool) tools. Genomic and reverse transcriptase PCR with subsequent Sanger sequencing was used to validate the potential fusions. Fluorescent in situ hybridization (FISH) using locus-specific probes was also performed. A total of 841 candidate chimeric transcripts were identified in the 12 tumors, with an average of 49 unique candidate fusions per tumor. After algorithmic and manual filtering, the final list consisted of 24 potential fusion events. Raw RNA-seq read sequences and PCR validation supports two novel fusion genes: a reciprocal fusion gene involving UQCR10 and C1orf194 in an adult spinal ependymoma and a TSPAN4-CD151 fusion gene in a pediatric infratentorial anaplastic ependymoma. Our previously reported ALK rearrangements and the RELA and YAP1 fusions found in supratentorial ependymomas were until now the only known fusion genes present in ependymal tumors. The chimeric transcripts presented here are the first to be reported in infratentorial or spinal ependymomas. Further studies are required to characterize the genomic rearrangements causing these fusion genes, as well as the frequency and functional importance of the fusions. © 2016 Wiley Periodicals, Inc.

Region Specific Differences of Claudin-5 Expression in Pediatric Intracranial Ependymomas: Potential Prognostic Role in Supratentorial Cases

Ependymomas are common pediatric brain tumors that originate from the ependyma and characterized by poor prognosis due to frequent recurrence. However, the current WHO grading system fails to accurately predict outcome. In a retrospective study, we analyzed 54 intracranial pediatric ependymomas and found a significantly higher overall survival in supratentorial cases when compared to infratentorial tumors. Next we performed region-specific immunohistochemical analysis of the ependyma in neonatal and adult ependyma from the central canal of spinal cord to the choroid plexus of lateral ventricles for components of cell-cell junctions including cadherins, claudins and occludin. We found robust claudin-5 expression in the choroid plexus epithelia but not in other compartments of the ependyma. Ultrastructural studies demonstrated distinct regional differences in cell-cell junction organization. Surprisingly, we found that 9 out of 20 supratentorial but not infratentorial ependymomas expressed high levels of the brain endothelial tight junction component claudin-5 in tumor cells. Importantly, we observed an increased overall survival in claudin-5 expressing supratentorial ependymoma. Our data indicates that claudin-5 expressing ependymomas may follow a distinct course of disease. The assessment of claudin-5 expression in ependymoma has the potential to become a useful prognostic marker in this pediatric malignancy.

EPN-30YAP1-MAMLD1 FUSIONS ALONE ARE SUFFICIENT TO FORM SUPRATENTORIAL EPENDYMOMA-LIKE TUMORS IN MICE

EPN-30. YAP1-MAMLD1 FUSIONS ALONE ARE SUFFICIENT TO FORM SUPRATENTORIAL EPENDYMOMA-LIKE TUMORS IN MICE Kristian W. Pajtler1,2, Sebastian Brabetz1, Monika Mauermann1, Norman Mack1, Laura Sieber1, David T. W. Jones1, Hendrik Witt1,2, Huiqin Korkel-Qu3, Marc Zuckermann4, Jan Gronych4, Andrey Korshunov5,6, David Capper5,6, Hai-Kun Liu3, Stefan M. Pfister1,2, Marcel Kool1, and Daisuke Kawauchi1; German Cancer Research Center, Division of Pediatric Neurooncology, Heidelberg, Germany; University Hospital Heidelberg, Department of Pediatric Oncology, Hematology and Immunology, Heidelberg, Germany; German Cancer Research Center, Molecular Neurogenetics, Heidelberg, Germany; German Cancer Research Center, Molecular Genetics, Heidelberg, Germany; GermanCancer Research Center, Clinical Cooperation Unit Neuropathology, Heidelberg, Germany; University Hospital Heidelberg, Department of Neuropathology, Heidelberg, Germany Oncogenic fusions containing RELA orYAP1have recentlybeen identified as genetic hallmarks of distinct molecular subgroups of supratentorial ependymomas (ST-EPN), designated ST-EPN-RELA and ST-EPN-YAP1, respectively. ST-EPN-YAP1 tumors, exclusively found in pediatric patients, are molecularly andclinicallydifferentfromST-EPN-RELAtumors, suggesting that theyhave to be treated differently. YAP1 acts as a transcriptional regulator in the HIPPO tumor suppressor pathway. The lack of adequate models for ST-EPN-YAP1 has so far hindered efforts to develop effective targeted therapies for these tumors. In an attempt to model this subgroup, the most frequent fusion type, YAP1-MAMLD1, was constructed and cloned upstream of IRES-Luciferase into the pT2K transposable vector. The resulting vector was injected together with the Tol2 transposase into the lateral ventricle of E13.5 wildtype mouse embryos followed by transfection using an electroporation-based in vivo gene transferapproach.Afterbirth,YAP1-MAMLD1-expressing tumors,monitored using luciferase-based in vivo bioluminescence imaging, developed rapidly with 100% penetrance. The animals had to be sacrificed due to severe neurological symptoms on average at P20. Resulting tumors resembled molecular characteristics of their human counterparts. The YAP1-MAMLD1 protein was predominantly compartmentalized to the nuclei of tumor cells even when phosphorylated at serine residue 127, which normally retains YAP1 in the cytoplasm, implying constitutive activation of the YAP1 fusion protein. Conserved tumorigenic potential of transformed cells was confirmed by subsequent orthotopic transplantation of these tumor cells into immunocompromised recipient mice. We thus provide a novel model for ST-EPN-YAP1, which is currently entering first preclinical drug testings. Neuro-Oncology 18:iii30–iii39, 2016. doi:10.1093/neuonc/now070.29 #The Author(s) 2016. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

EPN-34EPIGENOMIC ANALYSIS OF EPENDYMAL TUMORS IDENTIFIES SUBGROUP SPECIFIC ENHANCERS CONTROLLING DISTINCT REGULATORY CIRCUITRIES

EPN-34. EPIGENOMIC ANALYSIS OF EPENDYMAL TUMORS IDENTIFIES SUBGROUP SPECIFIC ENHANCERS CONTROLLING DISTINCT REGULATORY CIRCUITRIES Lukas Chavez1,2, Kristian W. Pajtler1,2, Serap Erkek1,4, Hendrik Witt1,2, Susanne Grobner1,2, Zhiqin Huang5, Mark Zapatka5, Volker Hovestadt5, David T. W. Jones1,2, Jan O. Korbel4, Peter Lichter5, Stefan M. Pfister1,2, and Marcel Kool1,2; Division of Pediatric Neuro-oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany; German Cancer Consortium (DKTK), Heidelberg, Germany; Department of Pediatric Oncology, Hematology and Immunology, University Hospital, Heidelberg, Germany; Genome Biology Unit, European Molecular Laboratory (EMBL), Heidelberg, Germany; Division of Molecular Genetics, German Cancer Research Center (DKFZ), Heidelberg, Germany; Clinical Cooperation Unit Neuropathology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Department of Neuropathology, University of Heidelberg, Heidelberg, Germany RecentmolecularclassificationeffortsusingDNAmethylationprofiles from 500 ependymal tumors revealed six distinct intracranial molecular subgroups, three in the posterior fossa and three in the supratentorial region. The vast majorityofhigh-riskpatients, forwhomeffective therapeutic conceptsaredesperately needed, were restricted to posterior fossa Group A ependymomas, PF-EPN-A, and to the largest group of supratentorial ependymomas, ST-EPN-RELA, harboring fusions to the principal effector of canonical NF-kB signaling. The current inability to effectively target alterations of the NF-kB pathway in ST-EPN-RELA and the lackof recurrent mutations oralternative distinctdriver events inPF-EPN-A andmostof the other subgroupshave so far hindered the development of novel (subgroup-specific) treatment strategies. To get a better understanding what is driving these tumors, we have used H3K27acChIP-Seq, integrated with tissue-matched DNA methylation, DNAand RNA-sequencing, to analyze the active cis-regulatory landscape across 24 individual tumors from all six intracranial molecular subgroups. Quantitative comparisons of H3K27ac enrichments across subgroups identified common and subgroup-specific enhancers as well as super-enhancers, thereby confirming inter-subgroup heterogeneity. Systematic correlation analyses between enhancer activity and gene expression within topologically associated domains, combined with computational analyses of transcription factor binding sites at enhancer loci, identified regulatory circuitries governing distinct transcriptional landscapes that are likely responsible for subgroup divergence. Our integrated analysis of enhancer elements in primary human tumors reveals novel insights into the genome-wide cis-regulatory architecture of ependymoma subgroups and their potential origins and may have relevant implications for future, possibly lineage-specific, therapeutic targeting approaches. Neuro-Oncology 18:iii30–iii39, 2016. doi:10.1093/neuonc/now070.33 #The Author(s) 2016. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.