bluuebunny/crossref_metadata_2025 huggingface dataset:
EPEN-07. Brain-tumor communication reveals potential new therapeutic targets for pediatric ependymoma
Authors: Antonelli Roberta , Jiménez Carlos , Servidei Tiziana , Riccardi Riccardo , Martínez-Saez Elena , de Toledo Josep Sánchez , Roma Josep , Gallego Soledad , Llort Anna , Moreno Lucas , Segura Miguel
Published: June 2022

Pediatric brain tumors (PBTs) represent the most common solid malignancies in children and the leading cause of cancer-related deaths. Despite the fact that survival after a high-grade brain tumor diagnosis is slowly improving, overall survival remains poor compared with most other cancers, thereby highlighting the need for new therapies. This is particularly true for Ependymoma (EPN), the second most common PBT that, despite advances in the understanding of EPN biology, still shows a poor prognosis in approximately 40% of patients. Accumulative evidence reveals that the transcriptome of tumors can be modulated by the host tissue, with brain tumors or brain metastasis derived from extracranial tumors being at the forefront of these studies. Our hypothesis is that understanding the impact of brain-tumor communication may open up new opportunities for therapeutic intervention. To characterize gene expression changes in Ependymoma tumors caused by the tumor microenvironment the transcriptome of patient-derived EPN cells was analyzed comparing in vitro cultured cells, subcutaneous xenografts and orthotopic xenografts. 2734 differentially expressed genes were found after comparing in vitro grown cells versus brain xenografts. Sixty-five of those genes were also differentially expressed when comparing human expression data from aggressive EPN versus the rest of EPN tumours. Among these candidates NTRK2 and CALB2 stand out. Gene depletion phenotype using multiple shRNA showed that the in vivo tumor growth of NTRK2-depleted cells, (but not CALB2) was remarkably reduced compared with control cells. These results suggest that NTRK2 could be a potential new therapeutic target for the treatment of Ependymoma
EPEN-08. Single-cell transcriptome analysis defines a tumor-supportive microenvironment and tumor-stroma crosstalk in pediatric ependymoma and medulloblastoma.
Authors: Federico Aniello , Okonechnikov Konstantin , Carmona Enrique Blanco , Lammers Julie A S , Kranendonk Mariette E G , Gojo Johannes , Englinger Bernhard , Jiang Li , Nierkens Stefan , Calkoen Friso G J , van der Lugt Jasper , Filbin Mariella G , Jäger Natalie , Pfister Stefan M , Kool Marcel
Published: June 2022

Brain tumors are the leading cause of disease-related death in childhood and strong efforts are required to develop innovative and efficient therapeutic strategies for patients with high-risk disease. Key critical factor of pediatric brain tumors is their molecular heterogeneity; one of the aspects that contributes to such heterogeneity is the intrinsic capacity of the tumor cells to organize, shape and exploit the surrounding brain tumor microenvironment (TME) to sustain tumor growth and malignant progression. TME was proved to play a crucial role in several malignancies, but in pediatric brain malignancies this has not been fully elucidated yet. Here, we aimed at characterizing the TME cell populations and their contributions in ependymoma and medulloblastoma, two of the most common pediatric brain tumor entities. Single-cell transcriptome analysis (n=65 ependymomas; n=39 medulloblastomas) of publicly available tumor datasets, as well as newly generated data of primary tumors and matching patient-derived tumor xenografts (PDX), showed an extensive heterogeneity of TME cell types with distinctive expression signatures. Amongst the identified TME populations, analysis revealed pro-inflammatory and proliferating myeloid cells, tumor-infiltrating lymphocytes, active regulatory T cells and vascular progenitor cells. Comparative analysis between primary and PDX tumors showed that tumor cells stimulated the host microenvironment, which in turn exhibited tumor-associated stromal signatures. Applying a deconvolution method, using our single cell data as reference, on a bulk tumor cohort including PFA ependymomas with different degree of immune infiltration, we observed an enrichment of polarized macrophages and microglia cells in tumor with high infiltration. Next, we identified TME markers involved in tumor-supportive functions, such as immune suppression (TIGIT, FOXP3, BCL2, CD19, ICAM2), pro-inflammatory stimuli (CCL3, CCL4, IL1B, GPNMB), extracellular matrix remodeling (COL4A1) and angiogenic processes (ANGPT2). TME markers with emerging role in ependymoma and medulloblastoma can be considered as possible targets for tailored and more effective anti-tumor therapeutic strategies.
EPEN-09. Multi-omics characterization of the blood-brain barrier in molecular groups of ependymoma
Authors: Sundheimer Julia K , Benzel Julia , Gansert Cornelia , Statz Britta , Seitz Christian , Pfister Stefan M , Maaß Kendra K , Pajtler Kristian W
Published: June 2022

BACKGROUND: A major challenge in the treatment of brain tumors is the limited penetration of many drugs through the blood-brain barrier (BBB). BBB characteristics include endothelial cells connected by tight junction proteins (e.g. Claudin5) and expression of efflux transporters (e.g.P-gp) with the physiological role to limit the accumulation of potentially toxic substances in brain tissue. While BBB permeability shows anatomical region-specific characteristics and changes with age, brain tumors can also impact its integrity. To achieve therapeutically relevant drug concentrations in the tumor, characterization of the pathophysiological BBB is fundamental when developing (pre)clinical trials. Our study seeks to increase our understanding of the BBB composition in various molecular groups of ependymoma. RESULTS: Transcriptional BBB characteristics were assessed for primary ependymoma (n=440), cell lines (n=3), mouse models (n=22), and healthy brain controls (n=200). T-distributed stochastic neighbor embedding (tSNE)-based clustering analyses based on most relevant tight junction and efflux transporter gene sets revealed distinct molecular ependymoma group-specific expression patterns. While patient-derived xenografts models (PDX, n=20) showed high similarity with patient tumor samples, in utero electroporation-based (IUE, n=2) mouse models did not fully recapitulate these BBB characteristics. Supratentorial ependymoma with ZFTA fusions revealed a higher transcriptional expression level of important tight junctions (e.g.Claudin5) compared to other groups and normal brain which was confirmed at protein level in respective PDX models by using both western blot and ultra-high content imaging. CONCLUSION: Analyses of important BBB markers revealed significant differences between molecular groups of ependymoma, which may partly explain drug resistance of ependymoma with ZFTA fusion caused by a low BBB permeability. BBB characteristics of corresponding models suggest that IUE and PDX models representing ZFTA fusion-driven tumors cannot equally be used within preclinical drug trials. Findings will be further validated in preclinical studies while molecular BBB characterization will be expanded to other brain tumors.
EPEN-23. Interaction of epigenetic regulation and telomerase re-activation in high-risk ependymoma
Authors: Jaunecker Carola N , Kirchhofer Dominik , Madlener Sibylle , Laemmerer Anna , Gabler Lisa , Pirker Christine , Piontek Martin , Maaß Kendra , Okonechnikov Konstanitin , Englinger Bernhard , Jiang Li , Mayr Lisa , Senfter Daniel , Spiegl-Kreinecker Sabine , Stepien Natalia , Dorfer Christian , Filbin Mariella , Kool Marcel , Gojo Johannes , Berger Walter , Loetsch-Gojo Daniela
Published: June 2022

Ependymomas (EPN) account for 10% of pediatric CNS tumors. Among the ten subgroups characterized by DNA methylation profiling, tumors located in the supratentorial region that harbor ZFTA fusions (e.g. ZFTA-RELA), and tumors in the posterior fossa region group A (PF-A) represent the most aggressive entities. As currently therapy success relies on the extent of tumor resection and druggable targets are so far widely missing, new therapeutic approaches are urgently needed. Epigenetic dysfunction, resulting in aberrant histone modifications as well as altered DNA methylation patterns, majorly contributes to the aggressiveness of high-risk EPN. In earlier studies, we discovered that high-risk EPN is composed of a cellular hierarchy initiating from stem-cell like populations, frequently showing telomerase re-activation. Considering that epigenetic mechanisms regulate stemness maintenance and telomerase reverse transcriptase (TERT), we studied the impact of epigenetically active drugs on differentiation and telomerase re-activation in these tumors. Accordingly, we first investigated the basal expression levels of TERT and EZH2 in a panel of patient-derived high-risk EPN cell models of different subtypes (n=7). Interestingly, both, TERT and EZH2, were highly expressed predominantly in ZFTA-RELA cell models. Corroboratively, increased sensitivity of ZFTA-RELA cells towards the EZH2 inhibitor DZNep was observed in cell viability and clonogenic assays. While HDAC inhibitors were similarly active across high-risk EPN cell models, the BET inhibitor JQ1 more efficiently reduced survival of ZFTA-RELA cells. Treatment with DZNep resulted in a loss of H3K27me3 histone marks accompanied by decreased ubiquitination of H2AK119 in the investigated ZFTA-RELA cell models, and induced apoptosis indicated by PARP cleavage. Currently, impacts of direct or pharmacological EZH2 blockade on TERT promoter methylation, induction of senescence and differentiation are analyzed. Summarizing, we proof varying efficacy of epigenetically active drugs in high-risk EPN subgroups, in particular EZH2 inhibition in ZFTA-RELA cell models.
EPEN-27. Epigenetic dissection of spinal ependymomas (SP-EPN) separates tumors with and withoutNF2 mutation
Authors: Neyazi Sina , Yamazawa Erika , Kresbach Catena , Nagae Genta , Eckhardt Alicia , Umeda Takayoshi , Pohl Lara , Tatsuno Kenji , Saygi Ceren , Hana Taijun , Alawi Malik , Kim Phyo , Dorostkar Mario M , Higuchi Fumi , Suwala Abigail K , Takami Toshihiro , Wefers Annika , Nakanishi Yuta , Schweizer Leonille , Takai Keisuke , Engertsberger Lara , Komori Takashi , Mohme Theresa , Takami Hirokazu , Mynarek Martin , Nomura Masashi , Lamszus Karin , Mukasa Akitake , Kluwe Lan , Takayanagi Shunsaku , von Deimling Andreas , Ishii Kazuhiko , Benesch Martin , Imai Hideaki , Snuderl Matija , Frank Stephan , Ichimura Koichi , Hagel Christian , Mautner Viktor F , Rutkowski Stefan , Tanaka Shota , Aburatani Hiroyuki , Nobuhito Saito , Schüller Ulrich
Published: June 2022

Ependymomas encompass multiple, clinically relevant tumor types based on localization, genetic alterations, and epigenetic and transcriptomic profiles. Tumors belonging to the methylation class of spinal ependymoma (SP-EPN) represent the most common intramedullary neoplasms in children and adults. However, molecular data of SP-EPN are scarce, and clear treatment recommendations are lacking. The only known recurrent genetic events in SP-EPN are loss of chromosome 22q and NF2 mutations. Yet, it remains unclear whether SP-EPN with germline or sporadic NF2 mutations or with NF2 wild type status differ clinically or molecularly. To provide a comprehensive molecular profile of SP-EPN, we integrated epigenetic, genomic, transcriptomic, and histological analyses of up to 237 cases. Clustering of methylation data revealed two distinct molecular SP-EPN subtypes. The distribution of NF2 mutated cases differed significantly across these subtypes (p <0.0001): The vast majority of tumors harboring either a previously known NF2 germline mutation or a sporadic mutation were assigned to subtypes A, whereas subtype B tumors mainly contained NF2 wild type sequences. In addition, subtype A tumors showed a lower frequency of MGMT promoter methylation (p= 0.018) and contained almost all pediatric patients of the cohort. Whole-exome sequencing (30 cases) identified numerous mutations in NF2 wild type and mutated tumors. Mutated genes in NF2 wild type tumors were enriched for genes associated with cell cycle and cytoskeleton. RNA sequencing revealed two distinct transcriptional groups with upregulation of proliferative genes in one group and upregulation of cilial genes in the other group. The molecular subtypes displayed subtle, but significant differences in the appearance of histopathological characteristics, such as surfaces, inflammation, and hyalinized vessels. Investigation of clinical parameters is ongoing and will complete the picture of SP-EPN heterogeneity as an important basis for future clinical decision-making.
EPID-03. Epidemiology, treatment and outcomes of children and young adults with CNS tumors in Armenia
Authors: Hoveyan Julieta , Grigoryan Henrik , Hovsepyan Shushan , Avagyan Anna , Asatryan Eduard , Tamamyan Gevorg , Papyan Ruzanna , Sargsyan Lilit , Hakobyan Lusine , Bardakhchyan Samvel
Published: June 2022

BACKGROUND: CNS tumors are the most common solid tumors in children and the leading cause of cancer related deaths. The incidence of CNS tumors is 1.7-6.21 cases per 100000 children. The aim of current study is to analyze epidemiological data, treatment and outcomes of children and young adults (<25 years) with CNS tumors in Armenia during last 25 years. METHODS: We have collected data of pediatric and young adult patients treated in neurosurgery department, three major chemotherapy clinics and radiation therapy department from 01.01.1995 to 31.12.2020 in Armenia. Incidence by gender, age at diagnosis, the time from first complaints to diagnosis, histopathology results and overall survival rates were calculated. RESULTS: The population-based data revealed 176 patients diagnosed with primary CNS tumors during 25 years. Among them 98 (55.7%) were males. Mean age at diagnosis was 7.07 years and the mean time from the first complaints to diagnosis was 6.55 months. Medulloblastomas and other embryonal tumors (26.7%), low grade gliomas (16.5%), retinoblastomas (12.5%) and high grade gliomas (10.8%) were the most common diagnosed malignancies. Craniopharyngiomas, germ cell tumors and other malignancies were observed in 9.1% of patients. For 24.4% histopathological data was missing. Surgery, chemotherapy and radiation therapy were performed in Armenia for 62.5%, 33.5% and 19.3% patients respectively. Follow up information was available for 119 (67.6%) patients. 5-year overall survival was 76%. CONCLUSION: Embryonal tumors and gliomas were the most common diagnosed CNS malignancies in Armenia which is consistent with international data. Multimodal treatment was often not available in Armenia during study period, especially for early cases. We hope recent advances in surgery, chemotherapy, and radiotherapy will help to improve treatment outcomes.
EPID-08. Epidemiology of childhood brain tumors in Morocco
Authors: Erefai Ouassima , Haimer Amal , Habib Faouzi , Soulaymani Abdelmajid , Mokhtari Abdelrhani , Hami Hinde
Published: June 2022

INTRODUCTION: Brain tumors are the most common solid tumors and cause of cancer-related death in children less than 15 years of age. However, little is known about these tumors in Morocco. The aim of this study is to describe the epidemiological features of pediatric brain tumors in Morocco. METHODS: This is a descriptive retrospective study of pediatric brain tumor cases, diagnosed and treated between 1994 and 2015 at Al Azhar Oncology Center in Rabat. Patient’s age and sex, habitat area, overall survival and tumor characteristics were evaluated. RESULTS: During the study period, 41 children under the age of 15 years were diagnosed with brain tumors at Al Azhar Oncology Center. Brain tumors were more common among boys than girls, with a male-female ratio of 1.9. The average age of diagnosis was 7.47 ± 3.06 years (range 2-14 years). More than half (51.22%) of the cases were diagnosed in children aged 5-9 years. Regarding the habitat area, nearly two-thirds (62.50%) of children live at least 30 kilometer (km) away from the cancer center. Medulloblastoma was the most common tumor type with 34.15% of cases. Overall, one patient develops a metastasis. Among the cases for whom the outcome was known, five children died during the study period, consisting of three girls and two boys. CONCLUSIONS: Children’s brain tumors remain a serious public health problem in Morocco, especially with the limited number of specialized pediatric cancer centers. The travel burden is a significant factor affecting access to appropriate diagnosis and treatment and can impede the provision of high-quality care for cancer patients.
ETMR-01. Management of CNS tumor with BCOR internal tandem duplication with multimodalities therapy: Surgery, Intensive Chemotherapy, and Radiation
Authors: Mobark Nahla Ali , Alharbi Musa , Ballourah Walid , Alsultan Abdulrahman , El Manjomi Fahad , AlNaqib Zaid , Al-Banyan Ayman , Balbaid Ali Abdullah O , Abedalthagafi, MD Malak
Published: June 2022

The 2021WHO CNS tumor classification includes CNS tumors with internal tandem duplications in the BCL6 corepressor (BCOR) gene as a new entity of CNS embryonal tumors labelled high-grade neuroepithelial tumors with BCOR alterations (HGNET-BCOR) are characterized by genetic aberrations in the BCOR gene located at Xp11.4, leading to increased expression of BCOR mRNA and distinct DNA methylation profiles. currently no agreement on the optimal strategy to manage these rare tumors, which mostly occur in young children These tumors are usually treated as high grade glioma HGG with upfront radiation therapy with poor outcome. We report 2.5 years old boy presenting with headache and vomiting. MRI showed a well-defined left cerebellar mass, hyperintense in T2 and hypointense in T1, with restricted diffusion and no spinal CSF seeding metastases. He underwent gross surgical resection of the tumor initial pathological diagnosis was epithelioid high grade malignant neoplasm. Brain tumor methylation classifier analysis of resected tumor tissue confirmed a CNS tumor with BCOR internal tandem duplication (WHO grade 4). The patient was treated per COG ACNS0334 (3 induction cycles of vincristine, cyclophosphamide, cisplatin, etoposide, HDMTX, followed by consolidation with 3 cycles of carboplatin and thiotepa with autologous hematopoietic stem cell rescue). MRI brain before the start of chemotherapy showed a small recurrent mass within the surgical cavity. post-induction MRI detected stable-sized residual lesion in the surgical cavity; however, post-consolidation MRI showed complete resolution of the residual mass. The patient subsequently received craniospinal irradiation (36 Gy [CSI]) with a boost to the tumor bed up to 54 GY. By the time of writing this report our patient is still in complete remission. Our case showed that this aggressive brain tumor may respond well to intensive multimodalities therapy Further case studies and international prospective trials are needed to optimize the clinical management of these rare tumors.
ETMR-11. Transcriptional changes upon knockdown of alteredBCOR/BCORL1 transcripts in preclinical models of CNS embryonal tumors with BCOR-related alterations
Authors: Piontek Martin , Kirchhofer Dominik , Gabler Lisa , Lötsch-Gojo Daniela , Pirker Christine , Schmitt-Hoffner Felix , Jaunecker Carola N , Kool Marcel , Berger Walter , Gojo Johannes
Published: June 2022

BCL-6 transcriptional corepressor (BCOR) is an epigenetic regulator that silences gene expression mainly via the polycomb repressive complex 1.1 (PRC1.1). BCOR genomic alterations are found in a variety of different tumors and recently central nervous system (CNS) tumors with BCOR internal tandem duplication (ITD) were classified as a distinct molecular subgroup. We established and characterized two cell models derived from BCOR altered CNS tumor patients. One model is characterized by a frameshift mutation in the BCOR gene resulting in the expression of a truncated protein lacking the C-terminal PUFD domain required for correct assembly of the PRC1.1. Additionally, this model harbors a translocation of the BCOR homologue BCORL1. The second model has a characteristic internal tandem duplication (ITD) within the BCOR gene. To study the effects of mutated BCOR/BCORL1 on gene expression, we performed siRNA mediated knockdown of altered BCOR/BCORL1 transcripts in both models and analyzed transcriptional changes by mRNA expression array. Differentially expressed genes in BCOR/BCORL1 knockdown versus wild type conditions were enriched for signaling pathways involved in cell cycle progression, cell growth, DNA replication and cancer. This suggests that the alterations in BCOR/BCORL1 might have pro-oncogenic effects and thereby contribute to the aggressive phenotype of this disease. Especially in the BCOR ITD model knockdown of BCOR led to transcriptional downregulation of genes associated with the development of brain tumors such as FGF18, PDGFA and PDGFRA. Our results indicate that specific BCOR/BCORL1 alterations might impair its endogenous function as transcriptional repressor and deregulate the expression of multiple PRC1.1 target genes. An in depth characterization of epigenetic and transcriptional changes in BCOR/BCORL1 altered CNS tumors could lead to the identification of critical downstream effectors and ultimately reveal new therapeutic vulnerabilities.
GCT-05. Multi-institutional analysis of treatment modalities in metastatic germinoma in children
Authors: Shatara Margaret , Abu-Arja Mohammad H , MacDonald Shannon , Reiners Stephanie , Gorsi Hamza , Govender Dinisha , Dholaria Hetal , Nagabushan Sumanth , Schwartz Jonathan , Foo Jen Chun , Rajagopal Revathi , Perkins Stephanie , Bartels Ute , Zaghloul Mohamed S , Abdelhaleem Nada A , El-ayadi Moatasem , Abdelbaki Mohamed S
Published: June 2022

BACKGROUND: Primary intracranial germ cell tumors (GCTs) are rare heterogeneous tumors, with germinoma accounting for two-thirds of cases. Neoadjuvant chemotherapy with response-based reduced radiotherapy dose and field has become the standard management of localized CNS germinomas, however, treatment of primary metastatic disease has remained controversial. Furthermore, there is limited published research on the use of neoadjuvant chemotherapy in primary metastatic germinoma. METHODS: We performed a retrospective multi-institutional data collection and analysis of patients diagnosed with metastatic germinoma since 2000 to assess the overall survival (OS) and event-free survival (EFS) of the different treatment modalities administered. RESULTS: We identified 78 patients with germinoma, in two tertiary care centers, of which nine patients (11.5%; eight males) had metastatic disease. The median age at presentation was 13.3 years. All patients had a biopsy at presentation confirming the diagnosis. Three patients had positive CSF cytology (M1). Six patients received craniospinal irradiation (CSI) with boost to primary and metastatic sites, of which five patients received total CSI dose of 24 Gy, while the dose was unknown for one patient. One patient required one cycle of chemotherapy prior to CSI due to worsening visual changes, which subsequently resolved. One patient received two cycles followed by whole ventricular irradiation (WVI) of 23.4 Gy with a boost to the primary bed. One patient received WVI without neoadjuvant chemotherapy. One patient developed anoxic brain injury and only received chemotherapy. He died of recurrent progressive disease 15 months post-diagnosis. The median follow-up time was 77.5 months (range 15-130.5 months), with an OS of 88.9%. Further multi-institutional data collection and analysis is underway and will be presented at the meeting. CONCLUSION: We anticipate our results may elucidate the role of neoadjuvant chemotherapy in the treatment of metastatic germinoma, and whether when combined with lower CSI doses did not compromise EFS/OS.
GCT-19. Toward understanding of the pathogenesis of central nervous system germ cell tumors
Authors: Ichimura Koichi , Takami Hirokazu , Satomi Kaishi , Matsushita Yuko , Terashima Keita , Nishikawa Ryo
Published: June 2022

Central nervous system germ cell tumors (CNSGCT) are the most enigmatic brain tumors that arise predominantly in children and young adults. CNSGCTs are rare in Europe and North America, while they are rather common in East Asia. The genetic basis of the distinct regional prevalence is yet to be elucidated. The WHO Classification of Central Nervous System Tumours recognizes 6 subtypes of CNSGCT, however multiple subtypes are often present as a mixed tumor, and the subtype may change at the recurrence. In 2012, we organized the Intracranial Germ Cell Tumor Genome Analysis Consortium of Japan (iGCT Consortium) and have collected nearly 300 frozen tumor specimen and patients’ information for CNSGCT cases since then to comprehensively investigate the genomic/epigenomic mechanism of CNSGCT development. We found that alterations of the MAPK and/or PI3K pathways were present in approximately 50% of all subtypes of CNSGCTs, KIT mutations being the most common. Germinomas are characterized by global hypomethylation, indicating that their cell of origin may be primordial germ cells. Transcriptomic profiling suggested that germinomas and non-germinomatous germ cell tumors (NGGCTs) developed from the common cell of origin and then diverted at some stage. We also showed that components of mixed CNSGCT shared the identical somatic mutation while having distinct methylation profiles, supporting the common cell-of-origin theory. In this paper, we will present an overview of our investigation in the iGCT Consortium as well as some of the ongoing projects, single cell RNA sequencing among others.
HGG-10. Efficacy of convection-enhanced delivery of GB-13 (IL13.E13K-PE4E) in an orthotopic xenograft model of high-grade glioma is predicated on IL-13Rα2 expression.
Authors: Rechberger Julian , Porath Kendra , Schrecengost Randy , Sarkaria Jann , Daniels David
Published: June 2022

High-grade gliomas (HGG) encompass a large proportion of malignant tumors within the central nervous system. Despite advances in our understanding of underlying disease mechanisms, the prognosis remains dismal and efficacious therapies are lacking. As such, there is a dire, unmet, gap in clinical practice for treating this devastating disease. Here, we performed convection-enhanced delivery (CED) of GB-13 (also known as IL13.E13K-PE4E), a tumor-specific immunotoxin, into the mouse brain in an effort to assess safety and efficacy. Fifty-five nude mice were inoculated with cells from 3 distinct patient-derived HGG cell lines (low, medium and high IL-13Rα2 expression). After tumor size reached a pre-determined threshold, mice underwent stereotactic cannula placement into the tumor followed by a single 40-min ramped infusion (rate 0.2-0.8 ul/min) of GB-13 (volume of infusion 20 ul) at concentrations ranging from 5 to 50 ug/ml. Tumor progression was monitored semiweekly and animals were euthanized at the indication of progressive neurologic deficit. All animals tolerated the infusions without exhibiting any neurological changes. GB-13 decreased tumor burden and prolonged survival in a manner strongly associated with IL-13Rα2 expression. While no survival benefit was observed in animals harboring IL-13Rα2-low expressing HGG, IL-13Rα2-medium and -high animals lived significantly longer after GB-13 infusion than vehicle-treated animals (median survival prolongation >25 days). Postmortem examination of the brains revealed no morphological changes beyond the site of the cannula tract. While GB-13 decreased cell proliferation and increased the number of apoptotic cells, neuronal cell density in ipsilateral brain regions was retained and no monocyte infiltrate was evidenced following GB-13 exposure. These findings indicate that a single therapeutic infusion of GB-13 administered by CED is well tolerated and underscore the potential of IL-13Rα2-targeted therapies in a subset of HGG with increased IL-13Rα2 expression.
HGG-23. The presence ofROS1 fusions are not limited only to infantile hemispheric glioma.
Authors: Trubicka Joanna , Ciołkowski Maciej , Perek-Polnik Marta , Dembowska-Bagińska Bożenna
Published: June 2022

INTRODUCTION: Diffuse pediatric-type high-grade gliomas are diffuse gliomas with histological features of malignancy, typically occurring in children, and infants. For these tumors, precise classification, identification of prognostic and predictive factors requires molecular analysis. The ROS proto-oncogene 1 (ROS1) gene encodes a receptor tyrosine kinase that is involved in chromosomal rearrangements in numerous malignancies, and may be an attractive therapeutic target, since specific inhibitors have been approved for several neoplasms. Molecular evaluation including detection of ROS1 fusions in pediatric gliomas are not included in standard diagnostic tests so far, therefore data on its significance is still limited. We present two cases of pediatric ROS1 fusion-positive brain tumors. METHODS AND RESULTS: The patient no.1 was 1 year old boy with disseminated brain lesions. Histopathological examination displayed the presence of a neoplasm, which was composed of round and spindle-shaped cells with palisading necrosis, mitotic activity, and microvascular proliferation. The patient no.2 is 9 years old girl with tumor located in left frontal lobe. Microscopically, the neoplasm revealed the presence of oligodenroglial-like component with microvascular proliferation, and high mitotic activity. Targeted gene sequencing panel - Ampliseq Childhood Cancer Panel for Illumina was used to detect diagnostic and targetable gene fusions. In both of patients ROS1:GOPC gene fusions were detect. Identified fusions allowed to established diagnosis - infant-type hemispheric glioma with ROS1 fusion (patient no 1) and - diffuse pediatric-type high grade glioma with ROS1 fusion (patient no 2). CONCLUSIONS: Our results indicate, that the presence of ROS1 fusions are not limited to the infant-type hemispheric gliomas only and may play a role in other glioma entities. It may be worth to include this biomarker in the diagnostic panel of pediatric brain tumors to establish a more precise diagnosis and a potential therapeutic target. Funded by National Science Centre, Poland (2016/23/B/NZ2/03064).
HGG-54. CLK1 aberrant splicing in pediatric high-grade gliomas disrupts key oncogenic transcriptional programs
Authors: Naqvi Ammar , Ennis Brian , Jin Run , Gaonkar Krutika , Foster Jessica , Conkrite Karina , Rathi Komal , Kraya Adam , Sonawane Poonam , Madsen Peter , Storm Phillip , Resnick Adam , Rokita Jo Lynne
Published: June 2022

While much of the somatic coding variation underlying the oncogenic transformation of pediatric high-grade gliomas (HGGs) has been profiled, transcriptional splicing programs of these tumors remain under-explored. Here, we characterize aberrant alternative splicing in pediatric midline HGGs (n = 84). We identified 19,275 recurrent and significant (20% change from control, P < 0.05, FDR < 0.05) aberrant splicing events in 8,587 genes compared to non-diseased brainstem controls. Of those, 27% (n = 5,157) resulted in either a gain or loss of a known protein functional site within 3,294 genes. We prioritized splice variants affecting targetable kinases and found that mRNAs encoding CDC-like kinase 1 (CLK1), a known modulator of master splicing regulators, exhibit significantly increased exon 4 inclusion in midline HGGs. This leads to a gain of two known phosphorylation sites in CLK1, increased CLK1 protein expression and hyper-phosphorylation of Serine-rich splicing factors. To assess the impact of this event, we performed differential splicing and expression analyses, comparing tumors with the highest (n= 5) and lowest (n = 5) exon 4 inclusion. We discovered 3,037 genes to be differentially up-regulated in high exon 4 inclusion tumors with an enrichment of cancer-related pathways, including DNA repair, mitotic spindle, myogenesis and EMT. We next integrated these gene signatures with protein-protein interaction networks of kinase and transcription factors and show that increased CLK1 exon 4 inclusion disrupts critical regulatory networks, such as those involving FOXM1, which is implicated in cell cycle and proliferation processes. In summary, we describe aberrant splicing in pediatric HGGs as an additional mechanism that could drive tumorigenesis. Future work will focus on molecular validation and therapeutic targeting of CLK1 in available HGG models. Characterizing tumor-specific splicing variation has the potential to open new therapeutic strategies and understand mechanisms of treatment resistance in children with central nervous system tumors.
HGG-61.Landscape of cancer predisposition in pediatric high-grade glioma
Authors: Blattner-Johnson Mirjam , Sturm Dominik , Sievers Philipp , Jones Barbara , Schramm Kathrin , Balasubramanian Gnana Prakash , Sill Martin , Jäger Natalie , van Tilburg Cornelis M , Milde Till , Pajtler Kristian W , Dikow Nicola , Hirsch Steffen , Sutter Christian , Sahm Felix , Witt Olaf , Pfister Stefan M , Jones David T W
Published: June 2022

Current estimates indicate that approximately 8–10% of cancer incidence in young patients can be attributed to constitutional alterations in genes linked to tumor initiation. The rarity and highly heterogeneous nature of high-grade glioma (HGG) in children and adolescents requires coordinated efforts to capture the diversity of subtypes in a normal-tumor matched sequencing cohort. Combining sequencing data of two registries based at the Hopp Children's Cancer Center (KiTZ) Heidelberg (INFORM and MNP2.0) allowed us to investigate the landscape of constitutional alterations across 350 children with high-grade gliomas. Both cohorts independently showed a surprisingly high proportion of patients (17%) with constitutional pathogenic alteration variants in cancer predisposition genes (n=40/233 and 23/128). Our results confirm a high frequency of alterations affecting genes of the DNA mismatch repair (MMR) pathway in 44% of IDH-mutant tumors (n=12/27). Additionally, we observed an almost exclusive correlation of MSH6 constitutional variation and somatic mutation in the IDH1 gene (n=7/8). A hypermutator phenotype defined by a tumor mutational burden >10 mutations/mb) was linked in 14/17 patients to a constitutional alteration in one of the following MMR genes: MLH1, MSH2, MSH6 or PMS2, with IDH-wildtype cases mostly classified as ‘RTK1 subtype’ by DNA methylation analysis. Constitutional alterations in TP53 were found in 5% of the total cohort. Furthermore, these tumors occurred exclusively in the group of H3-/IDH-wildtype glioblastoma (12%), and 8/18 tumors belong to the pedHGG_MYCN subgroup (conversely, this represents 40% of all ‘MYCN subtype’ patients, a highly significant enrichment over other subtypes (p<0.001). The overall high percentage of constitutional alterations in pediatric HGG warrants human genetics counselling for all affected patients and their families. Additionally, the strong correlation of MSH6 and IDH mutations as well as Li-Fraumeni-Syndrome and MYCN positive signature should be further explored as this might open the avenue for much needed new therapeutic approaches.
IMG-08. Response assessment for pediatric craniopharyngioma: recommendations from the Response Assessment in Pediatric Neuro-Oncology (RAPNO) working group
Authors: Hoffman Lindsey M , Jaimes Camilo , Mankad Kshitij , Mirsky David M , Tamrazi Benita , Tinkle Christopher L , Kline Cassie , Ramasubramanian Aparna , Malbari Fatema , Mangum Ross , Lindsay Holly , Horne Vincent , Daniels David J , Keole Sameer , Grosshans David R , Poussaint Tina Young , Packer Roger , Cavalheiro Sergio , Bison Brigitte , Hankinson Todd C , Müller Hermann L , Bartels Ute , Warren Katherine E , Chintagumpala Murali
Published: June 2022

INTRODUCTION: Craniopharyngioma (CP) is a histologically benign tumor of the pituitary stalk that accounts for 4% of pediatric central nervous system (CNS) tumors. Given its location, CP often causes neuro-endocrine, hypothalamic, and vision dysfunction. Standard therapy consists of maximally safe resection +/- radiation therapy (RT). Medical management, including intra-cystic therapy, may have utility in certain contexts. Survival after CP is excellent, but quality of life is often poor secondary to functional deficits from the tumor and/or treatment. Few prospective CP trials have been performed, and response assessment has not been standardized. METHODS: The Response Assessment in Pediatric Neuro-Oncology (RAPNO) committee, formed of international experts in relevant subspecialties, devised consensus guidelines from published literature and/or expert opinion to assess CP response in prospective clinical trials. RESULTS: Magnetic resonance imaging (MRI) is the recommended radiological modality for baseline and follow-up CP assessment. Computed tomography can be useful for identification of calcification in the initial diagnostic work-up. The committee defined specific standard MRI-based sequences focused on comprehensive evaluation of the suprasellar space. Radiologic CP response is defined by two-dimensional measurements of both solid and cystic tumor components. Three-dimensional measurements are also encouraged in prospective trials. In certain clinical contexts, response of solid and cystic disease may be differentially considered based on their unique natural histories and responses to treatment (including transient cyst growth during or after RT). Importantly, the committee incorporated functional endpoints related to neuro-endocrine and visual assessments into CP response definitions. In most circumstances, cystic disease should be considered progressive only if growth is associated with acute, new-onset or progressive functional impairment. CONCLUSION: CP is a common pediatric CNS tumor for which standardized response parameters have not been defined. A RAPNO committee devised guidelines for baseline and longitudinal assessments of CP to uniformly define response in future prospective trials.
IMG-11. A COMPUTERISED CLINICAL DECISION SUPPORT SYSTEM FOR DIAGNOSING CHILDREN’S BRAIN TUMOURS USING FUNCTIONAL IMAGING AND MACHINE LEARNING
Authors: Rose Heather , Ahmed Arfan , Babourina-Brooks Ben , Khan Omar , MacPherson Lesley , Manias Karen , Peake Ashley , Ali Sana , Withey Stephanie , Worthington Lara , Novak Jan , Zarinabad Nilou , Grundy Richard , Arvanitis Theodoros , Peet Andrew
Published: June 2022

INTRODUCTION: Magnetic resonance imaging is a key investigation in the diagnosis of childhood solid tumours. Advanced techniques such as diffusion weighted imaging (DWI), magnetic resonance spectroscopy (MRS) and perfusion imaging probe the underlying cellular, chemical and vascular nature of the disease. Coupled with machine learning these scanning methods show improvement in diagnostic accuracy compared with conventional imaging. Advanced image analysis is not routinely available in hospitals. We present a clinical decision support system (CDSS) developed for advanced MR analysis and interpretation. METHOD: The CDSS was developed in house. The Children’s Cancer and Leukaemia Group Functional Imaging Group (CCLGFIG) Database, a national resource, was used to provide a repository of cases together with their advanced imaging and machine learning diagnostic classifiers. A new case is displayed alongside cases in the repository with known diagnoses, including summary statistics for relevant diagnostic categories. The CDSS was made available to radiologists, in their clinical environment for technical and clinical evaluation. Structured interviews were undertaken. The CDSS was developed as a computer app for multi-centre distribution. RESULTS: 436 MRS, 240 DWI and 85 perfusion cases were available for building repositories. Machine learning classifiers showed diagnostic accuracies for the major childhood brain tumour types of 85-95%. Comparison of MRS with a data repository was found to improve non-invasive diagnosis. Results from the CDSS can be uploaded to the CCLGFIG to support multicentre research. Positive feedback on the CDSS from clinicians included: ready access to advanced analysis; simple and efficient integration into clinical workflow; and assisted interpretation of advanced analysis. DISCUSSION: Advanced MR analysis techniques provide improved non-invasive diagnostic accuracy but are difficult to implement on clinical systems due to technical, infrastructure and training limitations. CONCLUSION: We have successfully released a CDSS for paediatric cancer within the hospital environment and assessed its suitability for clinical use.
IMMU-04. Transcriptional analysis reveals distinct microenvironmental subgroups across pediatric nervous system tumors
Authors: Nabbi Arash , Beck Pengbo , Delaidelli Alberto , Oldridge Derek A , Sudhaman Sumedha , Zhu Kelsey , Yang S Y Cindy , Mulder David T , Bruce Jeffrey P , Paulson Joseph N , Raman Pichai , Zhu Yuankun , Silll Martin , Brabetz Sebastian , Lambo Sander , Johann Pascal D , Resnick Adam C , Sorensen Poul H , Malkin David , Kool Marcel , Jones David T W , Pfister Stefan M , Jäger Natalie , Pugh Trevor J
Published: June 2022

INTRODUCTION: Recent clinical trials of immune checkpoint inhibitors indicated 5-11% response rate in pediatric patients depending on cancer type and expression of target proteins. Currently, a systematic analysis characterizing the immune microenvironment of childhood tumors is lacking. The main objective of this study is to uncover the features of immune microenvironment in pediatric nervous system tumors (pedNST). METHODS: We compiled transcriptomes of 925 tumors from three initiatives, Therapeutically Applicable Research To Generate Effective Treatments (TARGET, n = 149), International Cancer Genome Consortium (ICGC, n = 195) and Children Brain Tumor Tissue Network (CBTN, n = 581). We analyzed the performance of immune deconvolution tools and used publicly available datasets to define immune genesets. We conducted a consensus analysis to assign genes to cell-types and identify immunological groups. RESULTS: We found wide variability in immune infiltration across and within cancer types ranging from cold tumors such as medulloblastoma (2.7% infiltrate) to infiltrated entities such as neurofibroma (22.6%). Consensus clustering revealed four distinct immune clusters. The pediatric inflamed group (10%) included MYCN non-amplified neuroblastoma and ATRT. The myeloid-predominant group (30%) showed decreased infiltration of lymphoid cells but enrichment of myeloid cell genesets. The pediatric-cold group (42%) harbored no enrichment of immune genesets and included 72% of ependymomas and 65% of medulloblastomas. The immune excluded group (18%) showed depletion of immune cell-types and included sonic-hedgehog medulloblastoma. 71% of pedNST belonged to the lymphocyte depleted or immunologically quiet clusters, indicating the cold immune microenvironment in pedNST compared to adult cancers. CONCLUSION: We report characteristics of the immune microenvironment in pedNST. We found an overall cold microenvironment with low lymphocyte infiltration in this population compared to common adult cancers. We identified ~10% of tumors harboring a relatively inflamed microenvironment. Our data uncover characteristics of immune infiltration in pediatric tumors with potential implications to guide therapy.
IMMU-18. Targeting Antigen Presenting Cells to improve virotherapy efficacy in Diffuse Midline Gliomas
Authors: Labiano Sara , Marco-Sanz Javier , Laspidea Virginia , Garcia-Moure Marc , Puigdelloses Montserrat , Ausejo Iker , Hernández-Osuna Reyes , Becher Oren , Patiño-Garcia Ana , Gomez-Manzano Candelaria , Fueyo Juan , Alonso Marta M
Published: June 2022

With a 2-year survival less than 20%, Diffuse Intrinsic Pontine Glioma (DIPG) is the principal cause of pediatric death. Despite recent advances in the current treatments, the outcome for children with DIPGs remains dismal. Since the approval of T-VEC for melanoma by the FDA, oncolytic adenoviruses have emerged as a promising therapeutic strategy for brain tumors. Thus, our group launched the first world clinical trial phase I with the oncolytic adenovirus Delta-24-RGD (DNX-2401 in the clinic) for newly diagnosed DIPG (NCT03178032), which has shown safety and feasibility. Despite DNX-2401 increases the recruitment of T cells into the tumor, they usually become inactive due to the non-responsive tumor microenvironment evidencing the urgent need to improve this strategy focusing on the generation of effective long-term immune responses. Therefore, we decided to combine the Delta-24-RGD with the targeting of the costimulatory molecule CD40 in immunocompetent mice bearing orthotopic DIPG. The activation of the CD40 receptor, which is expressed by antigen presenting cells (APC) such as microglia, macrophages, and dendritic cells, is known to increase antigen presentation and enable T-cell priming and activation. Here, we observed that in addition to Delta-24-RGD anti-tumor effects, the stimulation of CD40 (using an agonistic antibody) on the tumor APCs results in a remodeling of the tumor immune compartment towards a proinflammatory scenario and a more efficient T-cell infiltration. Of importance, the combination therapy extends survival of treated mice as compared to single treatments or non-treated mice. In addition, we observe a complete regression of tumors in more than 40% of treated mice and the development of long-term anti-tumor immunity. We believe that these results provide a translational breakthrough in the treatment of these lethal tumors and open the door for a future innovative clinical trial.
LGG-13. The clinical and molecular characteristics of progressive hypothalamic/optic pathway pilocytic astrocytoma
Authors: Li Xiaoyu , Moreira Daniel , Bag Asim , Qaddoumi Ibrahim , Acharya Sahaja , Chiang Jason
Published: June 2022

Unresectable hypothalamic/optic pathway pilocytic astrocytoma (PA) can be challenging to manage due to repeated progressions despite multiple lines of therapy. To identify clinical and biologic factors associated with tumor progression, we retrospectively identified 72 unresectable non-NF1-associated hypothalamic/optic pathway PA. Tumors were classified as high-risk (50%) if they progressed after three or more lines of chemotherapy/targeted therapy, progressed after radiation, developed metastatic disease, or died of disease. DNA methylation profiling and transcriptome analysis (RNA sequencing) were performed on treatment-naïve tumors with available tissue (n=40), and the findings were validated by immunohistochemistry (IHC) on additional tumor tissue. The median follow-up of the entire cohort was 12.3 years. High-risk tumors were associated with male sex (M:F = 2.6:1), younger age at diagnosis (median 3.2 years vs. 6.7 years, P = 0.005), and high incidence of KIAA1549-BRAF fusion (81.5% vs. 38.5%, P = 0.0032). High-risk tumors demonstrated decreased CpG methylation and increased RNA expression in many mitochondrial genes and genes downstream of E2F and NKX2.3 transcription factors. Transcriptome analysis identified transcription factor TBX3 and proto-oncogene serine/threonine protein kinase PIM1 as common downstream targets of both E2F and NKX2.3 and potential drivers of tumor progression. IHC confirmed increased expression of TBX3 and PIM1 in high-risk tumors. PIM1 is known to increase the stability and transcriptional activity of MYC, and gene enrichment analysis identified enrichment of MYC targets. Signaling pathways known to be implicated in PA, such as MAPK and PI3K/AKT/mTOR, were also enriched, in addition to pathways related to mitochondrial biogenesis and oxidative phosphorylation. Our results support the model in which the p53-PIM1-MYC axis and TBX3 act alongside MAPK and PI3K/AKT/mTOR pathways to promote tumor progression, highlighting potential new targets for combination therapy and refining disease prognosis.