bluuebunny/crossref_metadata_2025_split huggingface dataset:
TMOD-23. A NOVEL BRAF V600E LOW-GRADE GLIOMA MOUSE MODEL HIGHLIGHTS EXOMIC AND TUMOR IMMUNE ALTERATIONS AND DIFFERING THERAPEUTIC RESPONSES IN LOW- AND HIGH-GRADE GLIOMAS
Authors: Marie Barrette Anne , Meyer Lasse , Hirata Yoko , Grossauer Stefan , Lu Edbert , Tamaki Whitney , Petritsch Claudia , Wang Wei 
Published: December 2020

Abstract
Pediatric low-grade glioma (pLGG), the most common brain cancer in children, is difficult to treat especially at recurrence. The BRAF V600E mutation is the second most common mutation in pLGG, and in a high-risk group for progression is associated with deletion of the tumor suppressor CDKN2A. A better understanding of the factors contributing to progression, in particular the role of the immune infiltrate is needed, but studies have been hindered by the lack of low-grade glioma mouse models. We utilized transgenic mice with a cre-activatable (CA) allele of BRAF V600E to generate endogenous models for low-grade gliomas. We found that BRAF V600E expression cooperates with hemizygous CDKN2A deletion to induce low-grade gliomas, with tumors forming at a greater latency than by homozygous deletion. Cell line derivatives from low-grade lesions continue to grow slower upon orthotopic injection than those we previously derived from high-grade tumors. Murine LGG can progress to higher grade tumors within the mouse lifespan and we observe exomic changes and alterations in the tumor immune infiltrate associated with progression, the details of which will be discussed at the meeting. High-grade cells’ phenotypic changes within in vivo passage are accompanied by exomic changes. The high-grade glioma immune infiltrate is altered by dual MAPK pathway inhibition with dabrafenib and trametinib. Adding dual immune checkpoint inhibition by anti-PD-L1 and anti-CTLA-4 antibodies significantly extends survival of dabrafenib-trametinib dual treatment. Human BRAF V600E mutant tumors reportedly have a higher tumor immune infiltrate than that of BRAF wildtype gliomas, consistent with our murine RESULTS: Here we present a novel model for BRAF V600E mutant gliomas in mice that has a frequent rate of progression, similar to human BRAF V600E mutant gliomas, and an active immune infiltrate in high grade tumors which makes them susceptible to the immunostimulatory effects of dual checkpoint inhibition.
TMOD-24. GENERATION AND CHARACTERIZATION OF A NOVEL TRANSGENIC IDO REPORTER MOUSE FOR IDO POSTTRANSLATIONAL MODIFICATION ANALYSIS IN SITU
Authors: Bell April , Zhai Lijie , Ladomersky Erik , Lauing Kristen , Bollu Lakshmi , Wainwright Derek 
Published: December 2020

Abstract
Glioblastoma (GBM) is the most common and aggressive primary central nervous system tumor in adults with a median survival of 14.6 months. GBM is a potently immunosuppressive cancer due in-part to the prolific expression of immunosuppressive indoleamine 2,3 dioxygenase 1 (IDO). Tumor cell IDO facilitates the intratumoral accumulation of regulatory T cells (Tregs; CD4+CD25+FoxP3+). Although immunosuppressive IDO activity is canonically characterized by the conversion of tryptophan into kynurenine, we have utilized transgenic and syngeneic mouse models and mutant glioma lines to demonstrate that tumor cell IDO increases Treg accumulation independent of tryptophan metabolism. Here, we address the gap in our understanding of IDO signaling activity in vivo. Subcutaneously-engrafted human GBM expressing human IDO-GFP cDNA was isolated from immunodeficient humanized NSG-SGM3 mice. The tumor was immunoprecipitated for the GFP tag using GFP-TRAP followed by mass spectrometry which revealed a novel methylation site on a lysine residue at amino acid 373 in the IDO C-terminus region. Western blot analysis of IDO protein also revealed the presence of tyrosine phosphorylation. Additionally, we recently created a new transgenic IDO reporter mouse model whereby endogenous IDO is fused to GFP via a T2A linker (IDO→GFP). This model allows for the isolation of IDO+ cells in real-time and without causing cell death, thereby creating the opportunity for downstream molecular analysis of in situ-isolated GFP+ cells. Collectively, our work suggests that IDO non-enzyme activity may involve the post-translational modifications we recently identified. As IDO activity may differ between in vitro and in vivo modeling systems, we will use the new IDO→GFP reporter mouse model for an improved mechanistic understanding of how immunosuppressive IDO facilitates Treg accumulation in vivo.
TMOD-27. EFFICACY OF SOLUBLE PANOBINOSTAT (MTX110) IN PRECLINICAL MODELS OF ADULT GLIOBLASTOMA
Authors: Ashley David , Keir Stephen T , Roskoski Martin A , Davies Rhian , Williams Ben , Damment Stephen J P , Conlon Kelly 
Published: December 2020

Abstract

INTRODUCTION
Panobinostat is a histone deacetylase (HDAC) inhibitor with antineoplastic and anti-angiogenic effects in glioma. HDAC inhibitors have demonstrated therapeutic efficacy preclinically via multiple mechanisms, including the induction of cell-cycle arrest, differentiation, senescence, apoptosis, mitotic cell death, autophagy, generation of reactive oxygen species, inhibition of angiogenesis and metastasis, and improvement in tumor immunity. One of the biggest challenges in treating glioblastoma is achieving effective local drug concentrations, and trials using systemic administration of therapeutics have failed in GBM despite compelling pre clinical evidence. MTX110 (Midatech Pharma plc) is a water-soluble form of panobinostat currently in clinical development for DIPG and medulloblastoma using direct tumour delivery. We explored the therapeutic potential of MTX110 in GBM in our preclinical in vivo adult brain tumor models.

METHODS
Tumor-bearing mice were stratified to either the vehicle control or treatment group based on median tumor volume and were treated with Panobinostat/MTX110 at a dose of 15mg/kg IP, twice weekly for 5 consecutive weeks. The response to treatment was assessed by delay in tumor growth in days, expressed as a T (Treated) - C (Control) value. Statistical analysis was performed using SAS (a statistical analysis program) and the Wilcoxon rank order test.

RESULTS
MTX110 produced non-significant growth delays of 10.76 and 2.01 days (p Value ≥ 0.072 NS) in IDH wild type xenograft lines. However, in an IDH1 mutated line, MTX110 produced a significant growth delay of 23.35 days (p Value ≤ 0.018). Further work is ongoing to look at the therapeutic potential of MTX110 in combination with radiation in both IDH wild type and IDH mutated xenograft lines.
TMOD-30. IDENTIFYING NEW DRIVERS OF GROUP 3 MEDULLOBLASTOMA
Authors: Beigi Masihi Meher , Lee Catherine , Garancher Alexandra , Furnari Grace , Wechsler-Reya Robert 
Published: December 2020

Abstract
Medulloblastoma (MB) is the most common malignant childhood brain tumor. MB can be divided into four major subgroups – WNT, Sonic hedgehog (SHH), Group 3 (G3-MB), and Group 4 (G4-MB) – that exhibit distinct genetic alterations, gene expression profiles, and clinical outcomes. Patients with G3-MB have the worst prognosis, and a deeper understanding of this form of the disease is critical for development of new therapies. Most G3-MBs express high levels of the MYC oncogene, suggesting that MYC plays an important role in tumorigenesis. However, MYC overexpression is not sufficient to drive tumor formation. To identify genes that cooperate with MYC to promote development of G3-MB, we performed an in vivo mutagenesis screen using mice expressing the Sleeping Beauty (SB) transposon. Cerebellar stem cells isolated from transposon/transposase-expressing transgenic mice were infected with viruses encoding Myc, and these cells were transplanted into the cerebellum of adult hosts. Tumors that arose were subjected to DNA and RNA sequencing to identify candidate genes, and these genes were subjected to functional analysis to determine whether they could cooperate with Myc to drive G3-MB. These studies identified the transcription factor Ras-responsive element binding protein 1 (Rreb1) as a potent Myc-cooperating gene. Tumors driven by Myc and Rreb1 (MR tumors) resemble G3-MB at a histological and molecular level. Moreover, RREB1 is overexpressed in human G3-MB, and knockdown of RREB1 expression impairs growth of G3-MB cell lines and patient-derived xenografts. Ongoing studies are aimed at identifying the molecular mechanisms by which Rreb1 contributes to tumor growth. Our studies demonstrate an important role for RREB1 in G3-MB, and provide a new model that can be used to identify therapeutic targets and develop more effective and less toxic therapies for this devastating pediatric brain tumor.
TMOD-31. NOVEL GENETIC CHARACTERIZATION OF MURINE MEDULLOBLASTOMA CELL LINES
Authors: Rumler Sarah , Maienschein-Cline Mark , Noronha Melline Fontes , Song Fei , Lock Andrew , Loeb Jeffrey , Nicholas M Kelly 
Published: December 2020

Abstract
Pre-clinical research in medulloblastoma (MB) is conducted either with human-derived cell lines or tumors arising in genetically engineered mice (GEM). Murine MB cell lines are not readily available. To begin in vitro immuno-oncology MB research, we identified murine MB cell lines from research laboratories to determine their fidelity to human cell lines and GEM models. Using PubMed, we identified murine MB cell lines of potential interest. Seven cell lines form two independent laboratories were identified. We characterized the cell lines’ behavior in culture and performed next generation sequencing (NGS) on four of them (two from each group) to determine the extent to which these cell lines resemble both human and GEM MB models. DNA and RNA were extracted from MB cell lines, quality and quantity assessed. Whole-exome sequencing was performed and post-capture libraries sequenced. The cell lines identified were derived from either FVB/N TP53 null mice carrying the N-MYC oncogene (GTML3 and GTML5) or C57Bl6/J TP53 null heterozygous ptch (-/+) mice (MM1 and MM3). GTML cells grow in suspension and form clusters. MM cells are adherent, growing in monolayers. Whole exome sequencing of the 4 lines revealed similarities between both GEM and human MB cell lines, demonstrating 25% of sixteen genes known to be affected in both GEM tumors and human MB cell lines. Furthermore, the four cell Iines shared five deleterious mutations previously not described in MB, suggesting they might play a role in MB tumorigenesis: Pde4d, Whrln, Olr156, RIKEN cDNA D630045J12, and Olfr159. These are the first data to describe these murine MB cell lines and demonstrates 1) they resemble both GEM tumors and human MB cell lines at the genome level, and 2) they offer the potential to identify heretofore unrecognized mechanisms in MB tumorigenesis.
TMOD-32. MUTATIONAL ANALYSIS OF THE C11orf95 DOMAIN AND SINGLE CELL RNASEQ PROFILE OF A MOUSE MODEL OF SUPRATENTORIAL EPENDYMOMA
Authors: Troung Kevin , He James , Randazzo Ericka , Dunnack Jesse , LoTurco Joseph 
Published: December 2020

Abstract
We used a recently developed mouse model to better understand the cellular and molecular determinants of tumors driven by the oncogenic fusion protein C11orf95-RELA. Our approach makes use of in utero electroporation and a binary transposase system to introduce human C11orf95-RELA sequence, wild type and mutant forms, into neural progenitors. We used single cell RNA-seq to profile the cellular constituents within the resulting tumors in mice. We find that approximately 70% of the cells in the tumors do not express the oncogene C11orf95-RELA and these non-oncogene expressing cells are a combination of different non-tumor cell cell-types, including significant numbers of T-cells, and macrophages. The C11orf95-RELA expressing tumor cells have a unique transcriptomic profile that includes both astrocytic and neural progenitor marker genes, and is distinct from glioblastoma transcriptomic profiles. Since C11orf95-RELA is believed to function through a combination of both activation of NF-κB response genes by constitutive activation of RELA, and genes not activated by NF-κB, we assessed the expression of NF-κB response genes across the populations of cells in the tumor. Interestingly, the genes that best defined the oncogene expressing tumor cell population were not enriched for NF-κB response genes relative. We hypothesized that the C110rf95 domain may function to bring RELA transcriptional activation to inappropriate non-NF-κB targets, and we therefore performed a point mutation analysis of the C110rf95 domain. We found that mutations in either of the cysteines or histidines that make up a possible zinc finger domain in C11orf95 eliminate the ability of the fusion to induce tumors. In cell lines, these loss-of-function point mutants still trafficked to nuclei, and activated NF-κB pathways. We are currently using RNAseq and CRISPR loss-of function to identify genes downstream of C11orf95-RELA that are required for tumorigenesis.
TMOD-36. THE DEVELOPMENT OF A NOVEL MOUSE MODEL TO STUDY THE ROLE OF HISTONE MUTATIONS AND MODIFICATIONS IN PEDIATRIC HIGH-GRADE GLIOMA
Authors: Grigore Florina , Day Charles , Hanson Nicholas , Langfald Alyssa , Sarkaria Jann , Daniels David , Hinchcliffe Edward , Robinson James 
Published: December 2020

Abstract
Pediatric glioblastoma and diffuse intrinsic pontine glioma are high-grade gliomas of children (pHGG) with a median overall survival of under 15 months and among the most lethal cancers. Mutations in histone H3.3 and H3.1 occur as an early event in pHGG. H3.3G34R/V-mutations occur in pHGG of cerebral hemispheres, and H3.3K27M mutations occur in midline pHGGs. Post-translational histone modifications (PTMs) serve to regulate gene expression by relaxing or compacting chromatin and by recruiting proteins, with subsequent silencing or activating effects. H3.3 Serine 31 (S31) shows reduced phosphorylation during mitosis in H3.3G34R/V and H3.3K27M mutant cell. Phosphorylation at S31 is restored in wildtype H3.3K27 CRISPR revertants. Serine to alanine (A) mutant H3.3 S31A are nonphosphorylatable in vitro. To study the influence of histone mutations and the role of altered PTM and including the loss of methylation and phosphorylation on tumorigenesis, we have developed an innovative model based on the RCAS/N-TVA mouse model. In this system, the expression of an oncogenic driver is linked to mutant histone expression using a self-cleaving peptide, and tumors develop following viral delivery to neural stem cells in newborn mice. This approach is necessary, as otherwise, clonal selection could prevent tumors from forming with mutations detrimental to growth. To establish the model, N-TVA mice were injected with RCAS H3.3K27M-P2A-PDGFB, RCAS H3.3G34R-P2A-PDGFB, or H3.3WT-P2A-PDGFB. The mean survival of mice injected with H3.3K27M and H3.3S31A was 81 and 68 days, respectively, and 100% of S31A mice developed HGG. In contrast, H3.3WT caused only low-grade tumors in 46% of the mice, and all mice survived until 100 days. In ongoing experiments with H3.3G34R, 23% of mice succumb to tumors by 80 days. These results provide mechanistic insights into the early establishment of pHGGs and established a new mouse model to study the role of histone mutation and PTMs in tumor development.
TMOD-37. IN VIVO COMPRESSION AND IMAGING FOR CAUSAL STUDIES OF MECHANICAL FORCES IN THE BRAIN
Authors: Datta Meenal , Nia Hadi , Seano Giorgio , Roberge Sylvie , Huang Peigen , Munn Lance , Jain Rakesh 
Published: December 2020

Abstract
Clinicians have long observed the effects of abnormal mechanical forces – edema (fluid pressure) in particular – in brain tumors and the surrounding normal brain tissue. However, it was not previously possible to dissect the direct effects of solid stress (i.e., “mass effect”), a mechanopathology resulting from solid components of the tumor tissue, on the brain from the biological and physiological adverse effects exerted by cancer cells. We recently developed for the first time an in vivo compression device that allows for causal and mechanistic studies that delineate the solid mechanical forces of a tumor growing in the brain from its biological effects. The brain poses a unique anatomical consideration of abnormal mechanical forces due to its physical confinement by the skull. We adapted standard transparent cranial windows normally used for intravital imaging studies in mice to include a tunable screw for controlled and acute or chronic compression and decompression in the brain. This compressive cranial window allows for longitudinal imaging of the surrounding brain tissue (cortex or cerebellum) over time (weeks or months) as the screw is lowered further into the brain tissue to recapitulate tumor growth-induced solid stress. Using this device, we have demonstrated that solid stress is causally linked to vascular and neurological dysfunction in the brain. We have also been able to utilize this preclinical system to screen for effective therapeutic interventions to reduce solid stress-induced neuronal death and improve neurological function. Beyond cancer, this technique can be used to study a variety of diseases or disorders that present with abnormal solid masses in the brain, including cysts and benign growths. Thus, mechanistic studies enabled by the compressive cranial window can elucidate the role of mechanics in brain tumor progression, and reveal novel targets for treatment.
ATRT-04. INHERITED RHABDOID PREDISPOSITION SYNDROME: A CASE OF CHOROID PLEXUS CARCINOMA AND ATYPICAL TERATOID RHABDOID TUMOR IN SIBLINGS
Authors: Judd Alexis , Wright Erin , Rush Sarah 
Published: December 2020

Abstract
Choroid plexus carcinoma (CPC) and Atypical teratoid/rhabdoid tumor (ATRT) are aggressive, malignant brain cancers most commonly arising in children less than 3 years of age. These tumors often have genetic alterations in the tumor suppressor gene SMARCB1/INI1. Rhabdoid predisposition syndrome (RTPS) categorizes patients with germline mutations in SMARCB1 or SMARCA4, leading to a markedly increased risk of developing rhabdoid tumors. Both CPC and ATRT have been demonstrated in patients with these rhabdoid predisposition syndromes. In general, these tumors tend to have a poor prognosis. However, with the presence of a SMARCB1 mutation they may have improved overall survival. We present two interesting cases of siblings with maternally inherited SMARCB1 mutations: one a 21-month-old male who presented with an ATRT and another a 10 month old female who presented with a CPC. The ATRT was treated as per the Children’s Oncology Group study ACNS0333 with high dose chemotherapy and stem cell rescue as well as cranial radiation. The CPC was treated as per CPT-SIOP 2009 with etoposide, cyclophosphamide and vincristine. Unlike other patients with these aggressive tumors, both of these patients are alive without evidence of disease recurrence 8 and 7 years post therapy, respectively. Additional genomic testing on both tumors is currently pending in order to potentially identify other mutations that may impact survival. These cases further illustrate the similar profile of two very different tumors with improved overall survival that may be secondary to mutations in SMARCB1 in RTPS.
ATRT-09. IDENTIFICATION OF HUB GENES IN ATYPICAL TERATOID/RHABDOID TUMORS BY MULTIPLE-MICROARRAY ANALYSIS
Authors: Liu Wei , Chai Yi , Wang Junhua , Zhang Yuqi 
Published: December 2020

Abstract

BACKGROUND
Atypical teratoid/rhabdoid tumors (ATRT) are rare, highly malignant neoplasms arising in infants and young children. However, the biological basis of ATRTs remains poorly understood. In the present study, we employed integrated bioinformatics to investigate the hub genes and potential molecular mechanism in ATRT.

METHODS
Three microarray datasets, GSE35943, GSE6635 and GSE86574, were downloaded from Gene Expression Omnibus (GEO) which contained a total of 79 samples including 32 normal brain tissue samples and 47 ATRT samples. The RobustRankAggreg method was employed to integrate the results of these gene expression datasets to obtain differentially expressed genes (DEGs). The GO function and KEGG pathway enrichment analysis were conducted at the Enrichr database. The hub genes were screened according to the degree using Cytoscape software. Finally, transcription factor (TF) of hub genes were obtained by the NetworkAnalyst algorithm.

RESULTS
A total of 297 DEGs, consisting of 94 downregulated DEGs and 103 upregulated DEGs were identified. Functional enrichment analysis revealed that these genes were associated with cell cycle, p53 signaling pathway and DNA replication. Protein-protein interaction (PPI) network analysis revealed that CDK1, CCNA2, BUB1B, CDC20, KIF11, KIF20A, KIF2C, NCAPG, NDC80, NUSAP1, PBK, RRM2, TPX2, TOP2A and TTK were hub genes and these genes could be regulated by MYC, SOX2 and KDM5B according to the results of TF analysis.

CONCLUSIONS
Our study will improve the understanding of the molecular mechanisms and provide novel therapeutic targets for ATRT.
ATRT-10. ATYPICAL TERATOID/RHABDOID TUMOR OF THE PINEAL REGION IN A PEDIATRIC PATIENT
Authors: Almeida Carlos , Mançano Bruna Minniti , Matsushita Marcus , Previdelli Stephanie , Lamim Marina Lopes , Faustino Fabio Costa , Souza Fernanda Magalhaes , Lourenço Lucas Dias 
Published: December 2020

Abstract

BACKGROUND
Atypical teratoid/rhabdoid tumor (ATRT) is a malignant neoplasm of the central nervous system and corresponds to 1.5% of all intracranial tumors. Mainly affects children under three years of age and shows aggressive behavior (most pediatric patients succumb to their disease within a year after the initial diagnosis, despite the treatment performed). Its place of occurrence in children is preferably in the posterior fossa, and it is rare to appear in other regions. There are only seven patients with ATRT reported on literature; all of them are adults. We present the case of a pediatric patient with a tumor in the pineal region diagnosed as ATRT. CASE REPORT: Three-year-old female patient admitted with occipital headache, vomiting, and seizure. Magnetic resonance imaging (MRI) showed obstructive hydrocephalus secondary to a solid-cystic lesion located at the pineal region that was 3.0 x 3.0 x 3.5 cm in size. Spine MRI did not reveal leptomeningeal spreading. We performed an occipital transtentorial approach to achieve the best safe resection possible, and a ventriculoperitoneal shunt. Histological examination revealed ATRT. The patient received adjuvant treatment with radiotherapy and chemotherapy according to the “Head Start” protocol. One year after the surgery, MRI did not identify any remaining lesion.

CONCLUSION
ATRT is an aggressive and rare neoplasm whose clinical picture depends on the location of the tumor; however, it must be considered in the differential diagnosis of tumors of the pineal region in the pediatric population.