bluuebunny/crossref_metadata_2025 huggingface dataset:
METB-07. MINIMALLY-INVASIVE DIAGNOSIS OF DIFFUSE LEPTOMENINGEAL GLIONEURONAL TUMOR (DLGNT) USING CEREBROSPINAL FLUID CELL-FREE DNA SEQUENCING IN PEDIATRIC AND YOUNG ADULT PATIENTS
Authors: Larsen Alexandra Giantini , Hill Katherine , Hickman Richard , Bale Tejus , Holle Bridget , Mellinghoff Ingo , Dunkel Ira , Souweidane Mark , Greenfield Jeffrey , Sait Sameer Farouk , Miller Alexandra , Karajannis Matthias
Published: June 2023

Diffuse leptomeningeal glioneuronal tumor (DLGNT) presents with nodular leptomeningeal disease throughout the neuroaxis. Histology shows variable presence of a low density intraparenchymal lesion containing OLIG2-expressing neoplastic cells. Molecularly, DLGNT is characterized by the presence of KIAA1549::BRAF fusion and chromosome arm 1p deletion. Concomitant gain of chromosome arm 1q is associated with poor prognosis. Diagnosis by meningeal biopsy is often non-diagnostic and we hypothesized analysis of cell free DNA (cfDNA) from cerebrospinal fluid (CSF) could represent a superior diagnostic modality. We analyzed CSF samples from 7 patients, median age of 18 years, with DLGNT including matched germline DNA. MSK-IMPACT, a hybridization capture-based next-generation DNA sequencing panel, was utilized to analyze the DNA. Prior tissue biopsy was done in 5/7 patients. Of these, biopsy was non-diagnostic in 3 patients and positive for the KIAA1549:BRAF fusion in 2. Analysis of CSF cfDNA detected KIAA1549::BRAF fusion in 5/7 (71%) of patients, including all patients with prior non-diagnostic biopsy or tissue quantity insufficient for molecular testing. Analysis of CSF cfDNA copy number profiles revealed 1p-/1q+ in 6 patients and 1p- only in the remaining 1 patient, fully concordant with available prior tissue testing in all instances. In 2 patients with prior tissue-confirmed KIAA1549::BRAF fusion, the fusion was not detected in CSF cfDNA during/after treatment with a MEK inhibitor, but additional somatic alterations and DNA copy number profiles were similar to the prior biopsies. Additional somatic alterations were identified in ATRX, BCOR, RARA, STAT5A, SPOP, PPM1D, MED12, KMT2C, RECQL and SETD2, including likely oncogenic secondary driver alterations that have not been previously reported in DLGNT. Given the high molecular diagnostic yield and concordance with open biopsy, cfDNA CSF sequencing should be considered as a first line diagnostic maneuver for patients with MRI findings suspicious for DLGNT, followed by open biopsy only if CSF is non-diagnostic.
HGG-07. OVEREXPRESSION OF A PLAG-FAMILY TRANSCRIPTION FACTOR DURING MURINE BRAIN DEVELOPMENT CAUSES BRAIN TUMOR FORMATION
Authors: Vaillant Jan , Wittmann Andrea , Keck Michaela-Kristina , Rozowsky Jacob S , Filbin Mariella G , Pfister Stefan M , Jones David T W , Kutscher Lena M
Published: June 2023

Pediatric-type gliomas are the most common type of central nervous system tumors in children. They are highly diverse regarding their molecular entities and clinical associations, and they differ from their adult counterparts. A subset of pediatric-type high grade gliomas, including H3K27M mutated diffuse midline glioma, overexpresses the developmentally regulated transcription factor gene PLAG1. Two novel tumor types displaying amplifications or fusions with the related PLAGL1 and PLAGL2 genes have also recently been described (PMIDs 36437415, 34355256). How PLAG-family dysregulation drives tumor formation is currently unknown, however. We generated a novel mouse model that overexpresses hPLAG1 during brain development using a Cre-LoxP approach. Mice that overexpress hPLAG1 together with loss of trp53 in the Nestin-Cre lineage develop brain tumors by 3 months of age with 100 % penetrance. Intriguingly, tumors develop in different brain regions, with hotspots in the thalamus or inferior hypothalamus, the latter likely emerging from the brainstem. All mouse brains contain regions in the brainstem, thalamus and the prefrontal cortex with diffuse patterns of PLAG1+; KI67+ proliferating single cells. Using bulk-RNA sequencing, we identified several genes involved in embryonic brain development, which are still active in the tumors of adult mice. We hypothesize that continued overexpression of PLAG1 locks cells in an aberrant developmental state, making them susceptible for further oncogenic hits and ultimately leading to pediatric glioma formation. We are currently using single-nucleus RNA-seq to determine the developmental trajectories of single tumor cells to identify putative cells-of-origin and primary developmental pathways. Our work will elucidate the consequences of PLAG1 overexpression in pediatric brain tumors and its contribution to tumorigenesis. In the future, we hope to identify genetic dependencies of PLAG1 to generate novel treatment options.
HGG-14. RAS PATHWAY MEDIATED REGULATION OF HISTONE METHYLTRANSFERASE AND TUMOR SUPPRESSOR SETD2 IN PEDIATRIC HIGH GRADE GLIOMA
Authors: Liou Angela , Moran Deborah , Dougherty Jacquelyn , Harvey Kyra , Brosius Stephanie , Labella Kay , De Raedt Thomas
Published: June 2023

BACKGROUND

Pediatric High-Grade Gliomas (pHGG) are a significant cause of cancer-associated deaths in children. Hemispheric pHGG have frequent loss of the NF1 tumor suppressor (15%) causing aberrant RAS pathway activation. Intriguingly, loss of SETD2, a H3K36 methyltransferase, significantly co-occurs with loss of NF1. We found that nearly 80% SETD2-mutant pHGG have inactive NF1 (Pedcbio, 18/23 cases, 78%; odds-ratio 25; FDR adjusted P-value <0.001), suggesting a functional link between SETD2 and RAS signaling. NF1 is a GTPase-activating protein that negatively regulates the RAS oncogenic pathway. SETD2 is an epigenetic regulator and tumor suppressor that tri-methylates H3K36 on active gene bodies during transcription. We found that RAS pathway activation regulates SETD2 function.

METHODS

First, we used mass spectrometry to identify phosphorylation sites on SETD2 and generated phospho-mimetics/mutants to determine if these sites alter H3K36me3 levels. Second, we assessed if modulating downstream RAS effector pathways with MEK and PI3K inhibitors altered the phosphorylation of identified sites using the PhosTag gel electrophoresis assay.

RESULTS

We found that T2441 phosphorylation was upregulated upon MEK inhibition and that expressing T2441D phospho-mimetic and T2441A phospho-mutants had a differential effect on global H3K36me3 levels, implicating T2441 as an important regulatory node. Additionally, we identified that Cyclin Dependent Kinases are likely responsible for T2441 phosphorylation and are now investigating how RAS regulates these kinases.

CONCLUSION

To our knowledge it is the first time a functional connection between RAS pathway activation and SETD2 function has been found. It remains to be seen how of if RAS pathway activation alters the tumor suppressor function of SETD2 in pHGG.
HGG-25. TARGETED DRUGS SYNERGIZE WITH DOUBLE ALKYLATOR THERAPY IN H3.3 G34R/V PEDIATRIC HIGH-GRADE GLIOMA
Authors: Haase Rebecca , Green Adam , Kilburn Lindsay , Filbin Mariella
Published: June 2023

Diffuse hemispheric H3 G34R/V mutant gliomas (G34R/V DHG) are lethal brain malignancies occurring in the cerebral hemisphere of adolescent patients with no effective treatment options. To date, standard care is adapted from adult treatment protocols which include maximal tumor resection, radiotherapy, and chemotherapy with temozolomide (TMZ). In a recent study led by the Children’s Oncology Group (COG, ACNS0423), the combination of the alkylators TMZ and lomustine (CCNU) showed improved event-free survival for pediatric high-grade glioma patients. Still, patient benefits remain limited and thus demand further improvement of treatment protocols. Therefore, the aim of this study is to identify FDA-approved blood-brain-barrier crossing compounds that specifically targeting known vulnerabilities of pediatric high-grade glioma that achieve synergistic treatment results when combined with the double alkylator approach. We conducted a compound screen in combination with TMZ and CCNU on G34R/V-tumor derived gliomaspheres to identify synergies based on cell viability assays in vitro. We identified three candidate agents - Fimepinostat, trametinib, and avapritinib, which inhibit different key oncogenic targets in pediatric high-grade glioma - Pi3K and histone-deacetylases, MAPKs, and PDGFRA, respectively. Our ongoing in vivo study elaborates the translatability of the identified combinatorial therapies in patient derived G34R/V DHG orthotopic xenograft models. We are comparing different study arms of single agent treatment and double as well as triple combinations of alkylators and the candidate agents. This study will serve to determine (i) treatment efficacy, as measured by tumor growth and survival, (ii) occurring side effects, especially alkylator-induced suppression of platelet counts, and (iii) molecular changes upon different treatments using single cell transcriptomics and immunohistochemistry. In summary, we present valuable pre-clinical data supporting the combination of alkylators with targeted agents as a novel treatment strategy in G34R/V DHG, which might be translated into a promising strategy of a new comparative study based on COG trial ACNS0423.
HGG-26. GENOMIC AND IMMUNE ANALYSIS OF PRIMARY REPLICATION-REPAIR DEFICIENT (RRD) GLIOMAS REVEALS THREE SUBGROUPS WITH DISTINCT DRIVERS AND RESPONSE TO IMMUNOTHERAPY: AN IRRDC REPORT
Authors: Fernandez Nicholas R , Das Anirban , Levine Adrian , Negm Logine , Nobre Liana , Bianchi Vanessa , Stengs Lucie , Chung Jiil , Nunes Nuno M , Edwards Melissa , Bouffet Eric , Hawkins Cynthia , Tabori Uri
Published: June 2023

BACKGROUND

Replication-repair deficiency (RRD) caused by germline/somatic defects in mismatch repair (MMRD) and/or polymerase-proofreading genes (PPD) drives 5-10% of gliomas in children, adolescents, and young adults (CAYA). Although RRD-gliomas harbour high mutation-burden (TMB), the basis of their heterogenous biology, clinical behavior, and response to immune-checkpoint inhibitors (ICI) is unknown.

METHODS

We analyzed the genome (whole exome, low-coverage genome), methylome, transcriptome (bulk, single-nuclei), and the immune-microenvironment of RRD-gliomas in a large cohort of IRRDC patients and correlated these with clinical outcomes and response to ICI.

RESULTS

Gliomas in 202 CAYA-patients uniformly harbored hypermutation and genomic microsatellite-instability. Median TMB was 297-mutations/megabase, with frequent mutations in TP53 (90%), ATRX (85%), RAS/MAPK (80%) and IDH1/2 (15%). MMRD (but not PPD) mutational signatures contributed to the enrichment of driver mutations in POLE, IDH1, and TP53 while common pediatric mutations (K27M, G34R/V and BRAF;p.V600E) not driven by MMRD signatures were absent. Paired analyses suggested acquisition of novel variants driven by the mutational signatures that also impacted the immune microenvironment. Multi-omic analyses classified RRD-gliomas into three subgroups: RRD1 (MMRD+PPD; 60%), RRD2 (MMRD-only; 23%), and RRD3 (MMRD+IDH1/2; 16%). All RRD1-gliomas were glioblastomas with earlier age of onset, enrichment in CMMRD, arose at diverse locations including the posterior-fossa, classified in proximity to methylation-RTK1-subclass, exhibited balanced copy number profiles, harbored the highest TMB (median: 409-mutations/megabase), and immunogenic PPD signatures. Conversely, RRD3-gliomas were frequent in Lynch syndrome, presented at an older age, with predominant localization in the forebrain, more complex genomic instability, clustered in proximity to IDH1-gliomas, and harbored lower TMB (median: 33-mutations/megabase). RRD1-gliomas revealed the highest immune infiltrates with significantly improved median post-ICI survival of 52-months versus <12-months for RRD2/3 (p<0.0001).

CONCLUSIONS

The distinct genomic subgroups of RRD-gliomas can explain their diverse clinical outcomes, highlighting the need for developing subgroup-specific, immune-directed treatment approaches for these patients.
IMG-06. RADIOMIC-BASED RISK STRATIFICATION OF PEDIATRIC LOW-GRADE GLIOMA REVEALS DIFFERENTIALLY EXPRESSED MOLECULAR PROCESSES CONTRIBUTING TO VARIABLE PATIENT PROGNOSIS
Authors: Kazerooni Anahita Fathi , Kim Meen Chul , Kraya Adam , Mahtabfar Aria , Haldar Debanjan , Rathi Komal , Khalili Nastaran , Familiar Ariana , Ware Jeffrey B , Bagheri Sina , Anderson Hannah , Storm Phillip B , Resnick Adam C , Vossough Arastoo , Davatzikos Christos , Nabavizadeh Ali
Published: June 2023

In pediatric low-grade gliomas (pLGG), prognosis and responses to treatments are heterogeneous. This heterogeneity may be explained by the differences in molecular composition of the tumors of the same histology and the likely upstream alterations following administered radiation or systemic therapy. Integration of radiomics and clinical variables could generate a non-invasive biomarker that provides upfront prediction about patient’s risk of progression. We show that our proposed radiomic-based risk-stratification signature for pLGGs is associated with alterations in transcriptomic pathways. Standard multiparametric MRI sequences of 134 pLGG patients from Children’s Brain Tumor Network (CBTN) were retrospectively collected and 881 quantitative radiomic features were extracted. A multivariate Cox proportional hazard’s (Cox-PH) regression model was fitted on clinical (age, sex, tumor location, and extent of tumor resection) along with radiomic variables using 5-fold cross-validation, to predict patient’s risk of progression. The Cox-PH model showed excellent performance in prediction of PFS and patient’s risk scores, supported by the concordance index of 0.78. Radiogenomic analysis was performed to determine the transcriptomic pathways (1594 pathways, c2 MsigDb Reactome v2022.1) that contribute to the pLGG risk, predicted by the radiomic signature. ElasticNet regression was applied on the scores obtained by gene set enrichment analysis (GSEA) (in 70/134 subjects) to predict radiomic-based risk scores. Increased risk, corresponded to upregulation of DNA repair pathways, dysregulation of lipophagy, fatty acid beta oxidation, and vitamin D pathways, which are tumor-promoting. BRAFfusion signaling inversely correlated with risk, consistent with known favorable prognosis of KIAA1549-BRAF fused pLGGs. Upregulation in immune related pathways and Toll-Like Receptor (TLR) signaling was associated with lower risk. This study elucidates the synergistic dynamics between the biological processes that promote the risk of progression and radiomic-based risk-stratification signature. The proposed biomarker may be used to encourage targeted therapies in patients with increased predicted risk.
IMMU-01. EVALUATING THE IMPACT OF CAR DESIGN ON THE TUMOR IMMUNE MICROENVIRONMENT AND ANTI-TUMOR RESPONSE IN SYNGENEIC GLIOMA MODELS
Authors: Haydar Dalia , Crawford Jeremy , Chou Ching-Heng , Guy Cliff , Yi Zhongzhen , Zoine Jaquelyn , Gottschalk Stephen , Roussel Martine , Thomas Paul , Krenciute Giedre
Published: June 2023

B7-H3 CAR T-cells have limited efficacy in immunocompetent mouse models indicating a suppressive role of the tumor immune microenvironment (TIME). In this study, we set to optimize B7-H3 CAR structure and examine the effects of CAR design on brain TIME. We generated a panel of second-generation B7-H3-specific CARs with different transmembrane (CD8, CD28), costimulatory (CD28, 4-1BB), and activation (ζ, mutζ) domains. We then compared the cytolytic activity, expansion, and anti-tumor activity of T-cells expressing these CARs. Results showed that T-cells expressing B7-H3 CARs with CD28 transmembrane/costimulatory domains have superior efficacy in vitro. Yet, providing optimized costimulation and signaling did not induce superior anti-glioma efficacy of B7-H3 CAR T-cells in vivo. Additionally, incorporating 4-1BB signaling into CD28-based CAR T-cells by expressing 4-1BBL on their cell surface enhances the therapeutic efficacy and persistence of B7-H3 CAR T-cells in vitro. However, transgenic expression of 4-1BBL in CD28-based CARs was not associated with further enhanced anti-glioma efficacy of B7-H3 CAR T-cells in vivo. Next, using high-dimensional flow cytometry and spatial transcriptomic analyses, we show that suppressive tumor-associated macrophages (TAMs) infiltrate tumors in non-responder mice and they predominantly surround the tumor edges. Additionally, minimal T-cell infiltrates were observed in these tumors with predominantly exhausted and dysfunctional phenotypes. Analysis of gene-expression signatures early after CAR T-cell treatment revealed that tumors treated with CD28-based CARs differentially upregulate genes associated with inflammatory myeloid responses. While treatment with other signaling domains’ containing CARs upregulates pathways predictive of suppressive TAM and regulatory/dysfunctional T-cell responses. We show that global depletion of brain macrophages using CSF1R inhibitor exacerbates CAR T-cell anti-tumor activity. In summary, our results show that specific CAR domains induce an early inflammatory immune hub predictive of potent anti-tumor responses. Additionally, inflammatory macrophages are needed for successful CAR T-cell activation and anti-glioma responses.
IMMU-11. PRECLINICAL HIGH-RISK PEDIATRIC BRAIN TUMOR MODELS FOR IMMUNOTHERAPY: HURDLES AND THE WAY FORWARD
Authors: Mishra Deepak , Morris Shelli , Popovsk Dean , Bondoc Andrew , Kumar Shiva Senthil , Rutka James , Huang Annie , Olson Jim , Fouladi Maryam , Drissi Rachid
Published: June 2023

Despite recent therapeutic advancements in the treatment of pediatric brain tumors, high-risk brain tumors (pHRBT) remain the leading cause of cancer-related deaths in children. In recent years, immunotherapy has become a viable treatment option for several cancers including brain tumors. However, several factors have limited the use of immunotherapy in the treatment of pHRBT. For example, an "immunologically cold" tumor environment has been predominantly implicated in the failure of checkpoint inhibitors (ICIs) as monotherapy in pHRBT. Nevertheless, priming the effects of ICIs with epigenetic modulators through a process called “viral mimicry” that induces the expression of human endogenous retroviruses has the potential to enhance immunotherapy by sparking a T-cell mediated immune response. However, the inadequate understanding of the limitations of the preclinical models has prevented the development of efficient immunotherapy strategies for pHRBT. Although several studies and reviews have compiled some limitations of the available models, a hands-on experience using preclinical models for ICIs testing has not been fully communicated. Here, we share our bedside to bench experience with syngeneic and humanized mouse models of DIPG, ATRT, and medulloblastoma using ICIs therapy in conjunction with an epigenetic alteration. We will present and discuss the limitations of mouse models for the development of immunotherapies for pHRBT. For instance, our results indicated that the baseline levels of MHC-I expression in patients’ DIPG tumors were comparable to matched normal tissue. However, these levels were significantly lower in mouse DIPG tumors. To compensate for this difference, we treated mice with IFN-γ in combination with an epigenetic modulator. Surprisingly, the addition of INF-γ had a negative effect on animal overall survival compared to the treatment with the epigenetic modulator alone. Together, our experience demonstrated the importance of suitability assessment of current models for developing and translating successful immunotherapy strategies to treat pHRBT.
IMMU-15. PHASE I TRIAL OF GD2.CART-CELLS AUGMENTED WITH A CONSTITUTIVELY ACTIVE INTERLEUKIN-7 RECEPTOR (C7R) FOR TREATMENT OF HIGH-GRADE PEDIATRIC CNS TUMORS
Authors: Lin Frank , Stuckert Austin , Tat Candise , Moeller Karen , White Mark , Ruggieri Lucia , Zhang Huimin , Lindsay Holly , Baxter Patricia , Malbari Fatema , Aldave Guillermo , Chintagumpala Murali , Parsons D Williams , Brenner Malcolm , Heslop Helen , Rooney Cliona , Omer Bilal
Published: June 2023

BACKGROUND

Treatment of pediatric CNS tumors with T-cells modified with chimeric antigen receptors (CARTs) provides an innovative approach. We employ GD2-directed CART-cells (GD2.CARTs) modified to express a constitutively active interleukin-7 receptor (C7R) to increase GD2.CART survival and function independent of external cytokines, thereby augmenting activity against GD2-expressing CNS malignancies.

METHODS

In a Phase I study, we investigated the safety of intravenous GD2.CART therapy for pediatric patients with H3K27-altered diffuse midline glioma (DMG) or other GD2-expressing recurrent CNS tumors. We used a 3 + 3 design in which the first treatment cohort received GD2.CARTs without C7R, while subsequent cohorts received GD2.CARTs co-transduced with C7R (C7R-GD2.CARTs) at two dose levels. As a secondary endpoint we measured disease response 6 weeks after CART infusion.

RESULTS

12 patients were treated without dose limiting toxicity. The first cohort (n=3: thalamic DMG, spinal DMG, recurrent AT/RT) received GD2.CARTs without C7R at 1x107 cells/m2. No toxicity was observed and all 3 patients had clinical neurological improvement lasting approximately 4 weeks before disease progression. The next two cohorts received C7R-GD2.CARTs at 1x107 cells/m2 (n=3) and 3x107 cells/m2 (n=6). Mild tumor inflammation associated neurotoxicity was observed in 7 of 9 (78%) patients, which was controlled with anakinra without need for corticosteroids. Cytokine release syndrome (CRS) was observed in 5 of 9 (56%) cases [grade 1 (n=4), grade 3 (n=1)], resolving with tocilizumab. Eight of 9 patients receiving C7R-GD2.CARTs had clinical improvement or stability for more than 8 weeks (up to 10 months at last follow-up) and received repeat cell infusions at 6 week intervals (range 2-4 cycles). Partial radiologic responses were confirmed for 2 of 7 (29%) patients with DMG.

CONCLUSION

Intravenous treatment with C7R-modified GD2.CARTs was well tolerated in children with CNS tumors, and the duration of clinical improvement was extended by C7R co-expression.
IMMU-20. EVALUATION OF B7-H3 NANOBODY CAR-T CELLS IN PEDIATRIC GLIOBLASTOMA
Authors: Fanuzzi Mia , Cole Allison , Singh Mohit Pratap , Li Dan , Wang Ruixue , Liang Tianyuzhou , Ho Mitchell , Nellan Anandani
Published: June 2023

Chimeric antigen receptor (CAR)-T cell therapies are an undoubted success in childhood acute lymphoblastic leukemia; however, this success has not translated clinically to any childhood solid tumor. B7-H3 has been found to be highly expressed in pediatric brain tumors and correlates with tumor progression and poor prognosis. We utilized a novel nanobody based CAR-T cell which can bind tumor antigens with high affinity. We hypothesize that anti-B7-H3 nanobody CAR-T cells mediate more potent antitumor effects both in vitro and in vivo compared to existing antibody-based B7-H3 CAR-T cells. High expression of B7-H3 was confirmed on the surface of two pediatric glioblastoma cell lines by flow cytometry and Quantibrite staining. B7-H3 nanobodies isolated from camel phage libraries were cloned into lentiviral CAR-T cell constructs. We manufactured CAR-T cells by lentiviral transduction of human T cells. Glioblastoma tumor cells were co-cultured with B7-H3 CAR-T cells vs. control T cells. We confirmed B7-H3 specific cytokine release by CAR-T cells via ELISA and effective tumor cell killing via two different cytotoxicity assays (impedance or luciferase based). Nanobody based B7-H3 CAR-T cells exhibited statistically significant higher cytokine release and cytotoxicity compared to antibody based B7-H3 CAR-T cells. In vivo studies are currently evaluating the efficacy of intracerebroventricular delivery of B7-H3 CAR-T cells against two orthotopic glioblastoma models utilizing multiple human donor T cells in immunocompromised mice. We are simultaneously developing a syngeneic orthotopic glioblastoma model to evaluate the nanobody based B7-H3 CAR-T cell cross-reactive in mice utilizing an immunocompetent model. Careful investigation of CAR-T cell therapy in appropriate immunocompetent in vivo models is needed to develop effective immunotherapy for clinical application.
IMMU-23. RESEARCH ON MULTI-ANTIGEN T CELL INFUSION AGAINST NEURO-ONCOLOGIC DISEASE (ReMIND)
Authors: Cruz Conrad Russell , Gomez Stephanie , Geiger Ashley , Grant Melanie , DiCioccio Rachel , Fortiz Maria , Lang Haili , Datar Anushree , Shibli Abeer , Reynolds Emily , Lazarski Christopher , Wachspress Mariah , Pezzella Gloria , Gomez Daisy , Tanna Jay , Hoq Fahmida , Hanley Patrick , Kilburn Lindsay , Rood Brian , Packer Roger , Bollard Catherine , Hwang Eugene
Published: June 2023

INTRODUCTION

Pediatric patients with recurrent or progressive central nervous system (CNS) tumors have poor prognoses and clearly require improved therapies. Previous studies that used ex vivo expanded T cells show promising efficacy against viral infections. The polyclonal nature of these T cells, capable of recognizing multiple antigens, can be of potential benefit to patients with high-risk brain tumors, where intratumoral heterogeneity plays a prominent role in therapeutic resistance.

METHODS

Patients with CNS malignancies received T cells in a phase I dose escalation study (NCT03652545). The safety and feasibility of infusing ex vivo expanded, autologous T cells was determined in patients with newly diagnosed diffuse intrinsic pontine gliomas (DIPGs, Arm A, infused up to 5 months post irradiation) or recurrent/progressive non-brainstem CNS malignancies with (Arm C) or without (Arm B) lymphodepletion.

RESULTS

As of April 2023, 46 patients were enrolled on study. A total of 30 patients received infusions (8 in Arm A, 18 in Arm B, 4 in Arm C) that were well tolerated. One patient experienced a severe potentially-related adverse event (tumor swelling). In Arm A (DIPG), median OS was 12 months post-diagnosis (one patient survived for 31 months). In arm B, median OS was 11 months post T cell infusion, with 6 patients still alive (longest four years after treatment). In Arm C, 3/4 patients remain alive 4+ months from infusion (one patient had a potential pseudoprogression based on scans).

CONCLUSIONS

Autologous T cells can be expanded from pediatric patients with CNS malignancies and are well tolerated. Data suggests that TAA-T products may induce an anti-tumor response, with or without lymphodepletion, and prolong survival. Efforts are ongoing to analyze immune correlates which are focused on evaluating circulating T cell clones and investigating changes in peripheral blood gene signatures and circulating plasma proteins.
LGG-05. IMAGING-BASED DEEP LEARNING FOR EVENT-FREE SURVIVAL PREDICTION IN PATIENTS WITH PEDIATRIC LOW-GRADE GLIOMA
Authors: Zapaishchykova Anna , Hayat Hasaan , Ye Zezhong , Vajapeyam Sridhar , Chopra Rishi Balraj , Boyd Aidan , Liu Kevin X , Aerts Hugo J W L , Bandopadhayay Pratiti , Haas-Kogan Daphne A , Nabavidazeh Ali , Resnick Adam C , Mueller Sabine , Poussaint Tina Y , Cooney Tabitha M , Kann Benjamin H
Published: June 2023

Pediatric low-grade gliomas (pLGGs) have heterogeneous outcomes, making individualized clinical decision-making challenging. Imaging-based biomarkers for progression and/or recurrence may better risk-stratify pLGG patients and guide management. We developed and externally validated a deep learning (DL) algorithm to predict event-free survival (EFS) in pLGG using multi-institutional databases. We collected linked, T2-weighted diagnostic Magnetic Resonance Images (MRI) and clinical data for patients with WHO grade 1-2 pLGG (diagnosed from 1991-2017) from the Children’s Brain Tumor Network (CBTN, n=176, median follow-up: 3.7 years, IQR=2-6.8 years) for model development and internal validation, and Boston Children’s Hospital (BCH, n=219, median follow-up: 8.8 years, IQR=4-13.4 years) for external validation. Leveraging a self-supervised learning approach, we trained a DL Unet model for tumor segmentation and used it for extracting image features. We combined 12 DL-imaging features with three clinical variables (age, sex, and surgical resection status (gross total/subtotal/no resection) and trained a Deep Cox Mixtures(DCM) model for survival analysis. We externally validated the performance of three models: clinical, DL-imaging, and combined DL-imaging and clinical. The combined DL-imaging and clinical model outperformed the clinical alone and DL-imaging alone models for prediction of 3-year EFS (time-dependent AUC: 0.85, 0.73, 0.53, respectively) with improved calibration (Integrated Brier Score: 0.08, 0.13, 0.15, respectively). Using the combined DL-imaging and clinical model output, patients were divided into low and high-risk groups based on mean event probability (3-year EFS 53% vs 86%, p=0.02). Variables associated with poor EFS were imaging score, lower age, and lack of gross total resection. In conclusion, deep learning-derived, MRI-based imaging features may improve prediction of event-free survival and risk stratification for patients with pLGG.
LGG-15. SINGLE-NUCLEUS AND BULK RNA SEQUENCING OF PEDIATRIC PILOCYTIC ASTROCYTOMAS REVEALS CNS LOCATION-ASSOCIATED TUMOR CELL AND MICROENVIRONMENTAL HETEROGENEITY
Authors: Lammers Julie A S , Rozowsky Jacob S , Kranendonk Mariëtte E G , Schouten-van Meeteren Antoinette Y N , Meijer Lisethe , Calkoen Friso G , Hoving Eelco W , Wesseling Pieter , van der Lugt Jasper , Kester Lennart A
Published: June 2023

BACKGROUND

Pilocytic astrocytomas are the most common pediatric central nervous system (CNS) tumors. While the overall survival is generally favorable, a substantial part of the patients relapse, resulting in long-term complications. Additionally, pilocytic astrocytomas show limited genetic heterogeneity and are often driven by a single molecular event. The role of the tumor microenvironment (TME) in disease progression is yet unknown. Here, we aimed to delineate the composition of the tumor in pilocytic astrocytomas originating from different CNS locations.

METHODS

We collected 112 tumor samples, out of which a subset (n = 10) was used for single-nucleus RNA-sequencing (10X Genomics). These tumor samples originated from various CNS locations: posterior fossa (n = 64), supratentorial (n = 38) and spinal (n = 10). Clinical characteristics, DNA methylation profiles, whole exome/genome sequencing and bulk RNA sequencing data were available for most of these samples.

RESULTS

Single-nucleus RNA-sequencing revealed substantial heterogeneity amongst both tumor and TME cells, which mainly associated with tumor location. While a large proportion of tumor cells expressed gene signatures related to oligodendrocyte precursor cells (OLIG1/2, PDGFRA), a subset of tumor cells was characterized by high expression of astrocyte genes (AQP4, GFAP). Moreover, we defined multiple populations of lymphocytes and myeloid cells, with the latter constituting the vast majority of non-neoplastic cells. Deconvolution of the bulk RNA sequencing data showed heterogeneous involvement of the TME. Additionally, the relative abundances of TME cells varied considerably across CNS locations. We are currently correlating the relative proportions of tumor and TME cell populations with clinicopathological data.

CONCLUSION

Single-nucleus RNA-sequencing demonstrated transcriptional differences in both tumor cell states and TME cell populations, which associated with CNS location. Future research should elucidate the importance of the cellular composition of the tumor in pilocytic astrocytomas.
LGG-19. MULTI-MODALITY CHARACTERIZATION OF PEDIATRIC LOW-GRADE GLIOMA: THE ADDED VALUE OF DIFFERENT DATA MODALITIES
Authors: Haldar Debanjan , Kazerooni Anahita Fathi , Mahtabfar Aria , Khalili Nastaran , Familiar Ariana , Kraya Adam , Kim Meen Chul , Tu Wenxin , Haldar Shuvanjan , Bagheri Sina , Anderson Hannah , Viswanathan Karthik , Shaikh Ibraheem , Ware Jeffrey , Storm Phillip , Vossough Arastoo , Resnick Adam , Nabavizadeh Ali
Published: June 2023

Characterization of pediatric low-grade glioma (pLGG) remains a significant challenge in the field of neuro-oncology, with a need for more effective precision diagnostics. Multi-modal analysis, which incorporates data from varied sources, has the potential to provide a comprehensive understanding of the underlying biology of pediatric brain tumors. Despite its potential, the utilization of true multi-modality clustering remains limited in pediatric brain tumor research. In this study, we aimed to address this gap by using a clustering model that incorporated genomics, radiomics, and clinical variables (age, sex, and tumor location) to group patients into distinct clusters. 103 patients with pLGGs were included. Mutations data was derived from whole genome sequencing obtained through the PedCBioportal. Radiomic data was obtained from MR imaging through the Children’s Brain Tumor Network and included features from pre- and post-contrast T1, T2, FLAIR, and ADC sequences. Categorical variables included sex (male vs female), genetic mutation status for 10 selected genes (BRAF, FGFR1, TSC1, TSC2, NF1, MYB, EGFR, ALK, IDH1, and RB1) that are known to play a role in the pathogenesis of pLGG (mutated vs non-mutated), and tumor location (9 categories). Continuous variables included age (days) and radiomic features. All numerical variables were normalized and reduced into principal components that captured 90% of the variance in the data prior to clustering. Various clustering iterations were performed incorporating combinations of radiomic, genomic, and clinical data. Our models identified two distinct clusters and the PFS differences between clusters approached statistical significance with the integration of information from all modalities when compared to any combination of subsets of data, highlighting the complementary value of these modalities in providing a comprehensive characterization of pLGG. This study provides preliminary evidence for the utility of multi-modality data clustering in improving our understanding of pLGG and supports further investigation into this approach.
MDB-08. THYROID HORMONES INHIBIT MEDULLOBLASTOMA PROGRESSION THROUGH INDUCING TUMOR CELL DIFFERENTIATION
Authors: Yang Zeng-jie , Yang Yijun , Heller Allie , Rives Silvia Valdes
Published: June 2023

Hypothyroidism is commonly detected in patients with medulloblastoma (MB), a pediatric brain tumor, which is generally considered as a treatment-related complication. Although reduced levels of thyroid hormone (TH) significantly correlate with poor survival of patients with MB, the possible link between TH signaling and MB pathogenicity is unknown. Here, we found that TH plays a critical role in MB pathogenicity through regulating the terminal differentiation of tumor cells. In the absence or with reduced levels of TH, unliganded TRα (a nuclear TH receptor) physically interacts with EZH2 to epigenetically repress the expression of NeuroD1, a transcription factor dictating terminal differentiation of neuronal progenitors and MB cells. However, TH reverses EZH2-mediated repression of NeuroD1 through interfering with the binding between EZH2 and TRα, thereby stimulating terminal differentiation of tumor cells and repressing MB pathogenicity. Moreover, TH promotes extensive differentiation and suppresses the proliferation of tumor cells from different molecular subgroups of MB5 including hedgehog (HH) group as well as group 3 (G3) MB, suggesting that TH-induced differentiation is not restricted by oncogenic mutations in tumor cells. Consequently, TH treatment significantly inhibits the in vivo growth of SHH- and G3-MB via stimulating tumor cell differentiation, with no induction of tumor cell apoptosis or death, indicating that TH signaling represents a novel therapeutic entry-point for broad treatment of MB. These findings elucidate the mechanisms underlying terminal differentiation of MB cells, establish an unprecedented association between TH signaling and MB progression. Our studies provide compelling evidence for a promising tumor therapeutic modality by promoting tumor cell differentiation.
MDB-18. MOLECULARLY-DEFINED MEDULLOBLASTOMA: POPULATION-LEVEL PATTERNS IN THE UNITED STATES, 2018-2019
Authors: Ostrom Quinn T , Price Mackenzie , Neff Corey , Cioffi Gino , Waite Kristin A , Kruchko Carol , Barnholtz-Sloan Jill S
Published: June 2023

Medulloblastoma is one of the most common types of brain and other CNS tumors among the pediatric population in the US. Molecularly-defined brain tumor histopathologies—including medulloblastoma subtypes—were incorporated into US cancer registry reporting for individuals with brain tumors beginning in 2018. We assessed the epidemiology and overall survival (OS) patterns for medulloblastoma in children and adolescents, highlighting molecularly-defined subtypes. Children and adolescents (0-19 years) that were histopathologically diagnosed with medulloblastoma from 2018-2019 and had brain molecular marker data were identified within the Commission on Cancer’s National Cancer Database (NCDB) and Central Brain Tumor Registry of the United States databases, which combines data from CDC’s National Program of Cancer Registries (NPCR) and NCI’s Surveillance, Epidemiology, and End Results (SEER) Programs. Incidence rates per 100,000 population with 95% confidence intervals (95CI) were estimated for histopathologies with ≥16 cases. One-year OS was estimated using NCDB data for histopathologies with ≥50 cases with follow-up through 2020 using Kaplan-Meier methods. There were 601 cases of histopathologically-confirmed medulloblastoma diagnosed in children and adolescents from 2018-2019, 39.6% of which had available molecular subtype information. Overall incidence of medulloblastoma was 0.37 (95CI=0.34-0.40). Incidence of medulloblastoma subtypes was 0.05 (95CI=0.04-0.06) for SHH-activated & TP53wt, 0.02 (95CI=0.01-0.02) for WNT-activated, 0.08 (95CI=0.06-0.09) for nonWNT/nonSHH, while SHH-activated & TP53mut was too rare to calculate incidence. One-year OS for all medulloblastoma was 96.6% (95CI=92.1%-100.0%). One-year OS for nonWNT/nonSHH was 96.6% (95CI=92.8%-100.0%), and for SHH-activated & TP53wt was 93.7% (95CI=87.1%-100.0%). Other subtypes occurred too rarely to calculate survival. Our findings provide the initial US epidemiological estimates for molecularly-defined medulloblastoma histopathologies in children and adolescents. As improvements in collection completeness lead to increased molecular subtype availability, the robustness of these estimates will increase. Collection of these data are essential for understanding the epidemiology of this important childhood and adolescent brain tumor.
MDB-25. LARGE CELL/ANAPLASTIC MEDULLOBLASTOMA REPRESENTS MORE THAN ONE DISEASE ENTITY
Authors: Krause Katharina , Goschzik Tobias , Doerner Evelyn , Pietsch Torsten
Published: June 2023

Medulloblastoma (MB) with predominant large cell or anaplastic cytological features have been identified to be associated to an aggressive clinical course and poor survival. Because cases can show mixed cytologies, these histologically defined MB types were merged in the recent WHO classification of tumors of the CNS to large cell/anaplastic (LC/A) MB. In this study, we collected FFPE samples of 137 LC/A MB of all age groups (0-39 years) diagnosed at the DGNN Brain Tumor Reference Center in Bonn, Germany, and performed a comprehensive histological, immunophenotypical, genetic and epigenetic analysis by next-generation panel sequencing (NGS), 450k/850k methylation bead-array hybridization and molecular inversion probe (MIP) technology. 73% of cases showed predominant anaplastic histology, 27% predominant large cell histology. Methylation-based subtyping and sequencing showed that the cohort of LC/A MB represented different biological entities: 6% WNT-MB, 7% SHH-MB-TP53-wildtype, 10% SHH-MB-TP53-mutant, and 77% non-WNT/non-SHH MB (with predominant epigenetic subtype II). High-resolution copy number profiling by MIP demonstrated MYC amplification in 40% of non-WNT/non-SHH MB. MYC amplification was highly associated to infant disease and predominant large cell histology. On the contrary, predominant anaplastic histology was highly associated to non-infant disease, MYCN amplification and SHH activation. By NGS we detected recurrent mutations in 37 MB-related genes; the frequency of mutations of individual MB-related genes differed significantly between the histologically and genetically defined MB types. Our data clearly demonstrate that large cell MB and anaplastic MB represent different biological entities. Therefore, and also in respect to the future development of targeted treatment approaches to these highly malignant MB types, they should be precisely diagnosed as separate MB entities.
OTHR-03. CLASSIFICATION OF BRAIN TUMORS BY NANOPORE SEQUENCING OF CELL-FREE DNA FROM CEREBROSPINAL FLUID
Authors: Afflerbach Ann-Kristin , Rohrandt Christian , Brändl Björn , Sönksen Marthe , Hench Jürgen , Frank Stephan , Börnigen Daniela , Alawi Malik , Mynarek Martin , Winkler Beate , Ricklefs Franz , Synowitz Michael , Dührsen Lasse , Rutkowski Stefan , Wefers Annika K , Müller Franz-Josef , Schoof Melanie , Schüller Ulrich
Published: June 2023

For exact molecular diagnosis of CNS tumors, tumor tissue obtained through surgery is usually needed. However, knowledge on the molecular tumor type beforehand might influence surgical strategies and reduce surgery-associated risks. Molecular analyses of liquid biopsies have therefore gained increasing interest in order to secure diagnosis before surgery or to replace surgery in rare instances. Moreover, the minimally invasive nature of liquid biopsies enables a tight and longitudinal tumor monitoring with potentially higher sensitivity than imaging approaches. In this study, we applied Nanopore sequencing to 129 cell-free DNA (cfDNA) samples from the cerebrospinal fluid (CSF) of brain tumor patients, with 70.5% coming from pediatric patients. We analyzed copy number variations (CNV) and methylation patterns with a recently published random forest classifier (NanoDx). Circulating tumor DNA (ctDNA) was detected and successfully classified the tumor in 45% of all technically successful samples, both in pre- and early post-surgery samples as well as in samples from >14 days post-surgery, often with clinically unclear residual tumor or disease relapse. In all samples containing detectable tumor DNA, CNV analysis was more frequently successful than methylation analysis with overall detection rates of 88% and 44%, respectively. CNV analysis revealed diagnostic alterations, such as C19MC amplifications in ETMR as well as Chr.1q gain and Chr.6q loss in PFA ependymoma, which are important prognostic markers. Methylation analysis also allowed the classification of tumors with balanced genomes, like craniopharyngiomas. Finally, we were able to perform longitudinal analyses and found aberrations in the CNV profiles that were private to the tumor relapse, highlighting the potential of liquid biopsies to detect potentially relevant changes of tumor biology. Our results show that Nanopore sequencing is a promising approach to establish initial tumor diagnosis and to monitor disease courses by lumbar punctures.
TRLS-09. USE OF A PAN-PEPTIDE CHECKPOINT INHIBITOR IN THE TREATMENT OF CENTRAL NERVOUS SYSTEM TUMORS
Authors: Moertel Christopher , Pluhar G Elizabeth , Olin Michael
Published: June 2023

Immunotherapy has revolutionized clinical management of a select group of malignancies by offering a long-term, durable treatment response. Unfortunately, only a small percentage of brain cancers respond. The combination of multiple checkpoint inhibitors may result in serious immune-related adverse events. We have developed a Pan-Immune Checkpoint Ligand that simultaneously controls multiple immune checkpoints. The CD200 immune checkpoint modulates the immune system through a single inhibitory receptor (CD200R1) and multiple activation receptors (CD200ARs). We developed a peptide ligand, CD200AR-L, that targets the CD200ARs, which results in activation of the immune system and suppression of the inhibitory effects of CD200 and other immune checkpoints. Treatment of high-grade glioma in companion dogs with autologous tumor lysate vaccinations and CD200AR-L resulted in a two-year progression-free survival rate of 20% with no significant adverse events. We believe this response is due to the ability of CD200AR-L to modulate multiple immune checkpoints through shared signaling molecules in both the CD200 and PD-1/PD-L1 checkpoint pathways. Our preliminary data demonstrate that CD200R1 and PD-1 mediated immune checkpoint signaling is through SHIP1. CD200AR-L overcomes the immunosuppressive effects of the tumor-derived CD200 and PD-L1 by downregulating these checkpoints on both antigen-presenting cells (APC) and T-cells. CD200AR-L also downregulates PD-1 on APCs and inhibits the upregulation of PD-1 and CTLA4 on T cells. This translational research has led to the initiation of a phase I dose-escalation clinical trial for recurrent glioblastoma in adults (NCT04642937) and the writing of an IND for a pediatric HGG/DIPG trial.
TRLS-12. INTRAVENTRICULAR B7-H3 CAR T CELLS FOR DIFFUSE INTRINSIC PONTINE GLIOMA: INTERIM ANALYSIS OF BRAINCHILD-03 ARM C
Authors: Vitanza Nicholas , Ronsley Rebecca , Wilson Ashley , Huang Wenjun , Seidel Kristy , Pinto Navin , Gust Juliane , Gardner Rebecca , Jensen Michael , Park Julie
Published: June 2023

BACKGROUND

BrainChild-03 is a first-in-human phase 1 clinical trial delivering repeated intraventricular B7-H3 CAR T cells to children with central nervous system (CNS) tumors without lymphodepleting chemotherapy.

METHODS

We report on the ongoing Arm C for patients with diffuse intrinsic pontine glioma (DIPG), currently enrolling at the highest Dose Regimen (10x10^7 B7-H3CARs/dose). Primary endpoints are feasibility and safety. Secondary endpoints are disease response and correlatives of CAR-T activity.

RESULTS

19 patients have enrolled. All had successful CAR-T manufacturing. 17 patients were treated; 13 received sufficient doses for safety evaluation (4 doses/8 weeks) without a dose limiting toxicity (DLT). One patient had a DLT (pontine hemorrhage 8 days post-initial dose). The 5 unevaluable patients include: 2 on protocol not yet evaluable, 2 left the study due to rapid progression, and 1 did not meet eligibility to initiate treatment. Overall, patients have received 134 doses (median: 8/patient, range: 1-36). Adverse events include headache (93%), nausea/vomiting (79%), and fever (57%). Cytokine release syndrome (CRS) or immune effort cell-associated neurotoxicity syndrome (ICANS) have not occurred. Of 14 evaluable patients, 8 enrolled after progression, including some with metastases. Patients with progressive DIPG at enrollment have a median survival of 278 days post-initial dose (3/8 alive). Patients who enrolled before progression have a median overall survival of 207 days (6/6 alive) with 1 patient still receiving protocol therapy after 18 months (36 doses).

We have found localized CSF circulating CAR T cells and cytokine elevations supporting local immune activation. CSF mass spectrometry shows modulation of B7-H3 and immune analytes (CD14, CD163, CSF-1, CXCL13).

CONCLUSION

Repeated intraventricular B7-H3 CAR T dosing has been feasible for children with DIPG, even after progression, with evidence of local immune activation. Tolerability and prolonged stable disease suggest the potential for clinical benefit allowing for future cellular enhancements and combinations.
washington (1850–1854)
Authors: Adams Henry
Published: June 2023

Except for politics, Mount Vernon Street had the merit of leaving the boy-mind supple, free to turn with the world, and if one learned next to nothing, the little one did learn needed not to be unlearned. The surface was ready to take any...
harvard college (1854–1858)
Authors: Adams Henry
Published: June 2023

One day in June, 1854, young Adams walked for the last time down the steps of Mr. Dixwell’s school in Boylston Place, and felt no sensation but one of unqualified joy that this experience was ended. Never before or afterwards in his life did...
the press (1868)
Authors: Adams Henry
Published: June 2023

At ten o’clock of a July night, in heat that made the tropical rainshower simmer, the Adams family and the Motley family clambered down the side of their Cunard steamer into the government tugboat, which set them ashore in black darkness at the end...