bluuebunny/crossref_metadata_2025 huggingface dataset:
LGG-02. DRUG-CLASS SPECIFIC GENE-BASED MAPK SENSITIVITY SCORES (MSS) PREDICT SENSITIVITY TO MAPK INHIBITORS AND IDENTIFY IMMUNE INFILTRATION AS PUTATIVE TARGET IN PEDIATRIC LOW-GRADE GLIOMAS
Authors: Sigaud Romain , Albert Thomas K , Heß Caroline , Hielscher Thomas , Winkler Nadine , Walter Carolin , Münter Daniel , Selt Florian , Usta Diren , Ecker Jonas , Brentrup Angela , Hasselblatt Martin , Thomas Christian , Varghese Julian , Capper David , Thomale Ulrich W , Driever Pablo Hernáiz , Simon Michèle , Horn Svea , Herz Nina Annika , Koch Arend , Sahm Felix , Hamelmann Stefan , Andrade Augusto Faria , Jabado Nada , Schouten-van Meeteren Antoinette Y N , Hoving Eelco , Brummer Tilman , van Tilburg Cornelis M , Pfister Stefan M , Witt Olaf , Jones David T W , Kerl Kornelius , Milde Till
Published: June 2023

INTRODUCTION

Pediatric low-grade gliomas (pLGG), the most common brain tumors in children, are driven by alterations in the MAPK pathway. Several clinical trials have shown the potential for MAPK inhibitors (MAPKi) treatment in pLGG. However, the range of response is broad, even within entities sharing the same driving genetic MAPK alteration. A predictive stratification tool is needed to identify patients that will be more likely to benefit from MAPKi therapy.

METHODS

We generated gene-expression-based MAPKi sensitivity scores (MSS) for each MAPKi class (BRAFi, MEKi, ERKi), based on MAPK-related genes differentially regulated between MAPKi sensitive and non-sensitive cell lines from the Genomics of Drug Sensitivity in Cancer (GDSC) dataset. Single sample Gene Set Enrichment Analysis (ssGSEA) was used to measure and validate our MSSs in the GDSC dataset and an independent PDX dataset (XevaDB). The validated signatures were tested in a pLGG-specific background, using gene expression data from PA cell lines and primary pLGG samples.

RESULTS

Our MSS could differentiate MAPKi sensitive cells in the GDSC dataset, and significantly correlated with MAPKi response in the XevaDB PDX dataset. The MSS were able to differentiate glioma entities with differing MAPK alterations from non-MAPK altered entities, and showed the highest scores in pLGG. The MSSs were heterogeneous within pLGG entities with a common MAPK alteration, as observed in MAPKi clinical studies. Intriguingly, a strong correlation between our MSS and the predicted immune cell infiltration rate, as determined by the Estimate score, was observed and confirmed in a pLGG scRNA sequencing dataset.

CONCLUSION

These data demonstrate the relevance of gene-expression signatures to predict response to MAPKi treatment in pLGG, and will be further investigated in a prospective manner in upcoming clinical trials. In addition, our data could suggest a role of immune infiltration in the response to MAPKi in pLGG that warrants further validation.
LGG-04. CLINICALLY RELEVANT MODELING OF FUSION-DRIVEN PEDIATRIC LOW GRADE GLIOMAS USING DROSOPHILA MELANOGASTER
Authors: Jung Geena , Jain Payal , Liang Zizhuo , Li Feng , Rathi Komal , Chen Xin , Straka Joshua , Koptyra Mateusz , Sanchez-maldonado Stephanie , Fathikazerooni Anahita , Familiar Ariana , Nabavizadeh Ali , Waanders Angela , Huang Xi , Resnick Adam , Song Yuanquan
Published: June 2023

Pediatric low-grade gliomas (PLGGs) are the most common brain tumors in children, with varying degrees of brain invasion. Recent whole-genome sequencing has identified a rare gene fusion involving RAF1, a RAF isoform. Unlike other RAF fusions, RAF1 fusions are resistant to existing RAF inhibitors. Therefore, aside from surgical resection with adjuvant chemotherapy and radiation therapy, there are few targeted therapeutic alternatives for RAF1-fusion-driven PLGGs. Despite the prevalence and challenges this disease presented, our understanding of PLGGs was limited by a lack of genetic models. We ultimately picked Drosophila melanogaster as our model organism due to the conservation of major signaling pathways between flies and humans. Furthermore, this connection between humans and flies, coupled with other technical advantages associated with this model organism, like short generation cycle and its powerful genetic toolbox, makes Drosophila melanogaster an ideal organism to study the genesis and progression of PLGGs. With the help of the GAL4/UAS system, we established four fusion-driven PLGG fly genetic models and found that glial overexpression of QKI-RAF1, a fusion gene in pilocytic astrocytomas, induces an invasion-like phenotype with aberrant glial migration. This migration defect was suppressed by glial overexpression of repulsive guidance signaling receptors Robo2 or PlexA/B, indicating the dysregulation of repulsive guidance signaling pathways. Immunostaining coupled with quantitative analysis revealed that Robo2 expression is downregulated in migrating tumor cells in flies, which is recapitulated in mouse astrocytes overexpressing QKI-RAF1 and PLGG patients with RAF fusions. We further broaden our findings by profiling the tumor transcriptomes, revealing potential downstream effectors, including the G protein-coupled receptor GPR180/CG9304, and inhibition of which suppresses tumor invasion in flies. Taken together, we present the PLGG fly model system, leading to the discovery of Robo2, Plexins, and GPR180/CG9304 as potential therapeutic targets.
LGG-06. DEVELOPMENT OF A WEB-BASED MOBILE DEVICE CALCULATOR APPLICATION FOR PREDICTING SHORT- AND LONG-TERM SURVIVAL IN PEDIATRIC OPTIC PATHWAY GLIOMA: A POPULATION-BASED DATABASE ANALYSIS
Authors: Brown Nolan , Kuo Cathleen , Gendreau Julian
Published: June 2023

Optic pathway gliomas (OPG) are low-grade lesions arising from the astrocytes of the visual pathway and diencephalon. For most patients, observation appears to be the treatment of choice, but it remains unclear how frequently serial imaging should be obtained and at what point lesions can be deemed to have become quiescent. There is therefore an ongoing need for prognostication tools that can accurately predict the behavior of OPG to help identify those lesions meriting therapeutic intervention. In the present study, we leverage population-level data from the Surveillance, Epidemiology, and End Results program (SEER) database to develop a predictive calculator for overall survival (OS) in pediatric OPG. Accordingly, we extracted all available patient-level data from the SEER database. Training and testing datasets were established. Cox proportional hazards regressions were then used to identify independent predictors of survival, and model validation was performed. A total of 1,052 pediatric patients met inclusion criteria. Most were between 5 to 9 years old (45.7%), males (51.6%), white (85.6%), non-Hispanic (82.1%), and 232 patients (22.1%) came from houses with a median income less than $54,999, while 111 patients (10.6%) lived in a rural county. Nearly 90% of patients did not undergo surgical debulking. Twenty-three patients (2.2%) received radiotherapy and 294 (27.9%) received chemotherapy. Additionally, univariate and multivariate analyses were performed to identify variables associated with OS. Median household income and subtotal resection were found to be predictors of OS on univariate analysis. Furthermore, on multivariate analysis, median household income greater than $55,000 and subtotal resection were predictive of higher OS. Age at diagnosis, sex, rural versus urban setting, benign versus malignant behavior, and use of chemotherapy or radiotherapy did not appear to affect OS. Finally, we created a calculator (https://spine.shinyapps.io/optic_glioma/) using our model to estimate 5-,10-, and 1-year OS probability and other survival outcomes.
LGG-09. CLINICAL ACTIVITY OF PAN-RAF INHIBITOR TOVORAFENIB IN THE REGISTRATIONAL PEDIATRIC LOW-GRADE GLIOMA ARM OF THE PHASE 2 FIREFLY-1 (PNOC026) STUDY
Authors: Kilburn Lindsay , Khuong-Quang Dong-Anh , Nysom Karsten , Landi Daniel , Ziegler David , Driever Pablo Hernáiz , Leary Sarah , Bailey Simon , Van der Lugt Jasper , Perreault Sebastien , Waanders Angela , Baxter Patricia , Witt Olaf , Hargrave Darren , McCowage Geoffrey , Zhao Xin , Da Costa Daniel , Cox Michael , Manley Peter , Hansford Jordan
Published: June 2023

Genomic alterations of BRAF are common oncogenic drivers in pediatric low-grade glioma (pLGG). Tovorafenib is an investigational, oral, selective, brain-penetrant, small molecule, type II panRAF inhibitor. FIREFLY-1 (NCT04775485) is a multicenter phase 2 study evaluating the efficacy and safety of tovorafenib monotherapy in patients with BRAF-altered cancers. Registrational arm 1 includes patients 6 months-25 years of age with recurrent or progressive LGG previously treated with ≥1 prior line of systemic therapy. Tovorafenib 420 mg/m2 (≤600 mg) is administered weekly, in 28-day cycles, (tablet or liquid suspension formulation) until progression. The primary endpoint of arm 1 is ORR, as defined by RANO criteria and determined by blinded independent review. As of September 28, 2022, arm 1 had enrolled 77 patients and is fully accrued. All patients had ≥6 months of follow-up. Median age at enrollment was 8 years (range 2-21). Patients had received a median of 3 prior lines of systemic therapy (range: 1-9); 60% had received prior MAPK pathway-targeted agents. The most common tumor site was optic pathway (51%). Sixty-four patients harbored a tumor BRAF fusion/rearrangement (83%) and 13 (17%) a V600E mutation. Median duration of tovorafenib treatment is 8.4 months (range 0.7-16.8); 59 patients (77%) remained on treatment at data cutoff. ORR in 69 RANO-evaluable patients was 64%, [3 CR, 41 PR (10 unconfirmed) and 19 SD] with a clinical benefit rate of 91%. The most common treatment-related adverse events (TRAEs) of any grade were hair color changes (75%), increased creatine phosphokinase (64%), anemia (46%), fatigue (42%) and maculopapular rash (42%). Two patients (3%) discontinued tovorafenib due to TRAEs. Updates from a longer follow-up on the 77 patients in arm 1 will be presented. Tovorafenib was generally well tolerated and showed encouraging evidence of antitumor activity in children and young adults with refractory BRAF-altered LGG.
LGG-11. COGNITIVE, ACADEMIC, AND QUALITY OF LIFE OUTCOMES IN SURVIVORS OF PEDIATRIC LOW-GRADE GLIOMA: CHALLENGING THE ‘BENIGN TUMOR’ PERCEPTION
Authors: Nagabushan Sumanth , Hamayun Mashaal , Fardell Joanna E , Donoghoe Mark , Bland Elizabeth , Bye Ann , Jacobson Erica , Manoharan Neevika , Ziegler David S , McLoone Jordana K , Johnson Alexandra M , Cohn Richard J
Published: June 2023

High survival rates in pediatric low-grade gliomas (pLGG) may overshadow potentially significant long-term toxicities and functional impact. Chemo-radiation sequelae are well documented, in contrast to those who undergo surgical resection or observation alone. We performed a retrospective cohort study from 2000-2015, assessing cognitive, academic, and quality of life (QoL) impact on 45 eligible pLGG survivors aged 0-16 years at diagnosis, at a median 7.4 years post-treatment. A multidisciplinary panel oversaw proxy questionnaires for young children (<7 years), proxy and self-reported for adolescents (8-15 years) and self-reported for young adults (>15 years). Data included demographics; tumor and treatment; early school (young child) progress; academic and occupation achievement (adolescents and young adults); health; and lifestyle issues. The incidence of abnormalities in the domains studied were compared to published population statistics. 16% of survivors underwent observation alone, and 84% surgery (58% complete resection). 57% of survivors experienced cognitive deficits. Young children (50%) and adolescents (42%) had low cognitive functioning scores, correlating with poor academic (p < 0.01) and standardised school educational tests’ performance. 42% of mainstream school attendees required learning support; 33% examination assistance; 50% completed secondary education and 22% a tertiary degree, but had attention (young child and adolescent), and memory (young adult) issues. 65.9% of survivors had at least one neurological concern, highest in adolescents (70%). Language deficits (42.9%), pain, fatigue, and hearing loss (28.6 %) in young children; and vision/sleep difficulties (35%); fatigue (30%) and mobility (25%) in adolescents were reported. Young adults suffered headaches (47.1%) and fatigue (29.4%). Young children (57%) suffered more emotional disturbance than adolescents (16%). Anxiety (23%) and depression (14%) reflected poor QoL on Emotion Thermometer scales in all survivors. These findings challenge the ‘benign’ label of pLGG and highlights the importance of close psychosocial surveillance in helping survivors achieve their best emotional and educational potential.
LGG-23. OUTCOMES UTILIZING BRAF INHIBITION MONOTHERAPY IN BRAFV600E MUTATED PEDIATRIC LOW GRADE GLIOMAS
Authors: McThenia Sheila , Reddy Kartik , Goldman-Yassen Adam E , Gray Rachel , Connelly Erin , Patteson Brooke , Aguilera Dolly , Castellino Robert Craig , Fangusaro Jason Ronald , Janss Anna , Mazewski Claire , MacDonald Tobey
Published: June 2023

BACKGROUND

Pediatric low-grade glioma (pLGG) tumorigenesis is driven by activation of the RAS/RAF/MAPK pathway. pLGGs have an overall survival over 95%; however, patients harboring a BRAFV600E alteration may have worse outcomes. Combined BRAF/MEK inhibition following incomplete resection demonstrated improved outcome in pLGG compared to combined carboplatin/vincristine chemotherapy. We evaluated efficacy and tolerability of single agent BRAF inhibitor treatment in our single institution pLGG cohort.

METHODS

We performed a single institution retrospective analysis, (2013-2023) at Children’s Healthcare of Atlanta on patients 0-21 years old with new or progressive BRAFV600E mutated pLGG, who were treated off-study with BRAF inhibitor monotherapy. We evaluated 2-year Progression Free Survival (PFS) and Objective Response (CR+PR). All toxicities were evaluated and described.

RESULTS

We identified fifteen patients with BRAFV600E mutated pLGGs treated with BRAF inhibitor monotherapy. Median age of diagnosis: 5.8 years (0.20–18.0). Histologic diagnosis: pilocytic astrocytoma (PA)(N=3); atypical PA (N=1); ganglioglioma (N=3); atypical ganglioglioma (N=3); pleomorphic xanthoastrocytoma (PXA)(N=2); LG neuroepithelial tumor (N=1); infiltrating glioma (N=1); and LGG (NOS)(N=1). Tumor location: hypothalamus/optic chiasm (N=5); third ventricle/thalamus (N=3); parietal/temporal lobe (N=3); brainstem (N=2); and cervicomedullary junction/spinal cord (N=2). Mean therapy duration: 30.7 months (3.9-74.6). Median follow-up: 32.6 months (16-78.1). Two-year PFS: 80% (12/15). Objective Response(OR) for 14 evaluable patients at 1-year on initial BRAF inhibitor therapy: 43% (0/14 CR+6/14 PR). Patients tolerated treatment with Grade 1 rash being the most common toxicity. Three of 15 patients (20%) discontinued therapy due to toxicities, including rashes, arthralgias/myalgias (Grade 2), and one corneal lesion.

CONCLUSIONS

In our small cohort of incompletely resected BRAFV600E mutated pLGGs, BRAF inhibition monotherapy was effective and well tolerated with an OR comparable to published outcomes of dual MEK/BRAF inhibitor therapy. This promising treatment should be further studied in prospective clinical
MDB-09. IMPACT OF PRDM6 ON CHROMATIN ACCESSIBILITY, GENE EXPRESSION, AND MEDULLOBLASTOMA FORMATION
Authors: Schmidt Christin , Husain Sarah , Carlson Annika , Cohen Sarah , Westelman Samantha , Wang Linyu , Weiss William , Schwer Bjoern
Published: June 2023

Group 4 medulloblastoma (MB) is the most common medulloblastoma subgroup and shows high incidence of metastasis and late-onset relapse cases. These tumors lack a unifying oncogenic driver and treatment targets, despite extensive genomic characterization. Group 4 MBs are characterized by recurrent genetic alterations in chromatin modifiers and amplification of stemness genes. A substantial fraction of Group 4 MBs are characterized by enhancer hijacking through tandem duplication of SNCAIP, resulting in high expression of PRDM6, a putative transcriptional repressor and histone methyltransferase. Some PRDM6-overexpressing medulloblastoma cases show additional mutations in chromatin regulators and high MYCN expression. We set out to elucidate the impact and oncogenic potential of sustained PRDM6 expression in early neural stem cell populations and patient-derived medulloblastoma cells. We find that PRDM6 expression in human iPSC-derived neuroepithelial stem cells (NESCs) results in tumor growth in mice at low penetrance. Moreover, we find that PRDM6 expression in MYCN-overexpressing NESCs does not further alter tumor aggressiveness or survival in vivo. Notably, PRDM6 overexpression in the patient-derived Group 3 MYC-amplified D283-Med cell line causes significantly increased aggressiveness of tumor growth and shorter survival in mice. At the cellular level, PRDM6 localizes to the nucleus, suggesting a role in gene expression regulation. Consistent with this notion, ATAC-seq and RNA-seq analysis of PRDM6-NESCs and PRDM6-D283-Med cells reveals major changes in chromatin accessibility and gene expression, specifically upregulation of integrin family members and gene family members of focal adhesion and extracellular matrix receptor interaction pathways. We conclude that PRDM6 promotes tumor growth in NESCs and may play a role in tumor maintenance through interactions with the extracellular matrix and tumor microenvironment.
MDB-13. CURRENT STATUS OF DIAGNOSIS AND TREATMENT FOR HIGH-RISK STAGE M2/M3 NON-WNT SUBTYPES MEDULLOBLASTOMA IN SOUTH CHINA
Authors: Cai Linbo , Lai Mingyao , Li Juan
Published: June 2023

OBJECTIVE

To analyze the current diagnosis and treatment status of high-risk stage M2/M3 non-WNT types medulloblastoma in China, and explore the optimal treatment option.

METHODS

The inclusion criteria were as follows: (1) age≤18 years old; (2) medulloblastoma was diagnosed by surgical pathology at initial diagnosis; (3) molecular subtyping: non-WNT types; (4) Chang’s stage: M2/M3. Exclusion criteria: cases of WNT molecular subtype were excluded. Clinical data of the patients were included in the analysis, and the overall survival rate and the survival difference between each molecular subtype group were analyzed.

RESULTS

A total of 247 children with medulloblastoma under 18 years old were admitted to Guangdong Sanjiu Brain Hospital from January 1, 2017, to December 31, 2022. In line with the inclusion criteria, a total of 31 children were enrolled in the present study. All patients were treated with conventional radiotherapy and chemotherapy according to the Chinese Guidelines for diagnosing and treating medulloblastoma. The median age of enrolled patients was 5 years (range 1-15 years), counting 21 males and 10 females. According to the Chang staging system, 16 patients were in the M2 stage, and 15 were in the M3 stage. 8, 11, and 12 patients were in Group 3, Group 4, and SHH molecular subgroups, respectively. Survival analysis showed that the 5-year survival rate of 31 children was 50.2%, and there was no significant difference in the 5-year survival rate between different molecular subgroups (p=0.57).

CONCLUSIONS

The overall prognosis of high-risk M2 and M3 staged medulloblastoma is poor. Except for the WNT subtype, the optimal treatment strategy for medulloblastoma with metastasis is still worth exploring.
MDB-19. MULTIOMIC PROFILING OF MEDULLOBLASTOMA REVEALS SUBTYPE-SPECIFIC TARGETABLE ALTERATIONS AT THE PROTEOME AND N-GLYCAN LEVEL
Authors: Godbole Shweta , Voss Hannah , Schlumbohm Simon , Schumann Yannis , Peng Bojia , Mynarek Martin , Rutkowski Stefan , Dottermusch Matthias , Dorostkar Mario M , Koshunov Andrey , Mair Thomas , Pfister Stefan M , Neumann Philipp , Hartmann Christian , Weis Joachim , Liesche-Starnecker Friederike , Guan Yudong , Schlüter Hartmut , Schüller Ulrich , Krisp Christoph , Neumann Julia E
Published: June 2023

Medulloblastomas (MBs) are malignant pediatric brain tumors which are clinically and histologically very heterogeneous. Epigenomic and transcriptomic analyses have advanced the understanding of these tumors and four main molecular subgroups – which themselves comprise several subtypes- have been defined: WNT-activated MB, Sonic hedgehog (SHH)-activated MB, Group3 and Group4 MB. Despite tremendous advances in classification and stratification, the pathogenesis of subtypes is still poorly understood and there is still a lack of targeted therapies. In contrast to nucleic acids, proteins more directly account for the phenotype and hold the potential to discover clinically relevant phenotypes, new biomarkers and therapy targets. In this study, we put together a harmonized cohort of 167 MB samples and integrated proteome data with DNA methylome and N-glycan data. At proteome level, we found six stable subtypes which could be assigned to two main molecular signatures namely-transcriptional/translational processes (pWNT, pG3myc and pSHHt) and synaptic/immunological processes (pG3, pG4 and pSHHs). pG3myc MB showed poor survival and accumulated high risk features such as anaplastic histology, epigenetic subtype II and MYC amplification. They showed an overlap of proteome patterns with favorable pWNT MBs but displayed significantly different protein abundancies of the vincristine resistance associated TriC/CCT complex and N-glycan turnover associated factors. Of note. N-glycan profiles distinguished MB subtypes and pG3myc MBs were enriched by complex bisecting N-glycans. We further identified Tenascin C (TNC) and Palmdelphin (PALMD) as suitable biomarkers for the pWNT and pG3myc MBs, respectively. Integration of proteome and DNA methylome data revealed that pWNT MBs showed the highest correlation of data modalities among MB subtypes, indicating a higher conservation of biological processes compared to other proteome subtypes. Our results shed light on new targetable alterations in MB and set a foundation for potential immunotherapies targeting glycan structures.
MDB-24. A DATA-DRIVEN APPROACH FOR THE IDENTIFICATION OF NEW SYNERGISTIC DRUG COMBINATIONS AGAINST NEURAL CANCERS
Authors: Popova Gergana , Larsson Ida , Koc Alper , Krona Cecilia , Nelander Sven
Published: June 2023

High-risk medulloblastomas are tumours with a poor survival prognosis (≤ 50%), which are currently treated with radiation therapy and DNA-damaging chemotherapy. The severe side effects of these treatments, including developmental problems and secondary tumours, underscore the need for new treatments with reduced toxicity. An attractive target for such therapy is the Myc-family proteins since high-risk medulloblastomas amplify either N-Myc (SHH-MB, G4-MB) or c-Myc (G3-MB). While the proteins from the Myc family themselves are often referred to as pharmacologically intractable, their levels and activity can be modulated by indirect targeting, e.g. inhibition of proteins located upstream or downstream of c-Myc/N-Myc. The diverse cellular processes and pathways that c-Myc and N-Myc are involved in, however, suggest that several Myc pathways must be interrupted simultaneously to achieve a lasting effect. To identify such multimodal interventions against Myc, we performed a principal component analysis of RNA sequencing data from patient-derived medulloblastoma cells (MB002, G3, MYC-amplified) and DAOY cells (SHH-group, no MYC amplification) that were treated with 120 small molecules. In the subsequent analysis, we focused on a selection of ~ 40 genes that represent common upstream regulators and downstream targets of either c-Myc or N-Myc. Applying a principal component analysis to these particular markers, we expect that the drugs that affect different pathways associated with c-Myc activity and are located at the opposite ends of the PC1 and PC2 axis should have a synergistic effect. Additionally, we expected that the drugs located closer to each other, which affect closely related pathways, would either have no effect or would be antagonistic. Our PCA distribution method can be used to select synergistic combinations in a manner that is easily extended to new compounds. This approach may allow fast screening of compounds for estimation of the treatment effect.
MDB-32. TRANSLATION OF NON-CANONICAL OPEN READING FRAMES AS A CANCER CELL SURVIVAL MECHANISM IN CHILDHOOD MEDULLOBLASTOMA
Authors: Hofman Damon , Ruiz-Orera Jorge , Yannuzzi Ian , Murugesan Rakesh , van Dinter Jip , Clauser Karl , Condurat Alexandra , Herman Amy , Shanmugam Vignesh , Zhou Kevin , Vogelzang Jayne , Wang Li , Roth Jennifer , Ligon Keith , Phoenix Timothy , Root David , Golub Todd , Bandopadhayay Pratiti , van Heesch Sebastiaan , Prensner John
Published: June 2023

High-risk medulloblastoma is one of the most recalcitrant pediatric cancers, and children with MYC-amplified disease frequently succumb to relapsed disease. Extensive analyses of the coding genome in this disease have characterized additional somatic events in some subsets of patients, though most tumors lack targetable mutations and do not yield insights regarding their aggressive behavior. At the same time, medulloblastoma is known to exhibit extensive rewiring of translational control in MYC-driven tumors, consistent with recent genetic evidence that the impact of this transcription factor on control of mRNA translation may be the most critical aspect of its function during tumorigenesis. Therefore, to propose previously unknown mechanisms for this disease, we have investigated the functional impact of translation of non-canonical open reading frames (ORFs) across medulloblastoma model systems. We demonstrate that these ORFs are commonly translated in medulloblastoma model systems and patient tumors, correlating with disease subtype. Using genome-wide CRISPR/Cas9 screens, we found that ORFs are frequently essential for cell survival in medulloblastoma and describe widespread reliance on upstream open reading frames (uORFs) in particular. From these, we identify a uORF in the ASNSD1 gene that is selectively upregulated and required for maintenance of cell survival by coordinating the function of the prefoldin-like complex, a poorly understood complex implicated in post-translational control. Together, our findings provide a blueprint for oncogenic uORFs as critical disease mediators both in medulloblastoma and, by extension, human cancers more broadly.
MDB-37. CDK9 IS A DRUGGABLE MEDIATOR SUSTAINING MYC-DRIVEN TRANSCRIPTIONAL CIRCUITRY IN MEDULLOBLASTOMA
Authors: Krishna Madhavan , Walker Faye , Sobral Lays Martin , Wang Dong , Veo Bethany , Balakrishnan Ilango , Pierce Angela , Serkova Natalie , Foreman Nicholas , Venkataraman Sujatha , Vibhakar Rajeev , Dahl Nathan
Published: June 2023

Though long recognized as a master regulator of cell proliferation across a wide range of cancers, Myc has proven elusive to direct therapeutic targeting. The CDK9-containing PTEFb, complexed with either BRD4 or SEC, facilitates Myc-driven transcriptional programs and is necessary for sustaining expression of Myc itself. Advances in development of clinical-grade CDK9 inhibitors creates an opportunity to examine this as a rational therapy for Myc-driven medulloblastoma (Myc-MB). In order to define the enhancer-promoter circuitry driving Myc expression in medulloblastoma, we performed chromosome conformation capture (Hi-C) from primary patient Myc-MB samples. Using a combination of CUT&RUN and RNA-seq, we find that treatment with the CDK9 inhibitor zotiraciclib depletes Myc binding and transcriptional activity at enhancer elements within the Myc topologically associated domain, largely abrogating transcriptional output from the Myc promoter. This leads to a decrease in Myc binding genome-wide with a concordant downregulation of hallmark Myc-driven transcriptional programs. Myc-MB cell lines are sensitive to CDK9 inhibition at low nanomolar concentrations, with a loss of fitness as measured by decreased proliferative or clonogenic potential and a marked induction of apoptosis. Clinically relevant CDK9 inhibitors show variable efficacy in vivo, but CNS-penetrant agents achieved a significant prolongation in xenograft survival. Together, these data demonstrate that CDK9 catalytic activity represents a druggable vulnerability underpinning Myc-driven transcriptional programs. The development of CNS-penetrant CDK9 inhibitors may open new avenues for rational therapy in these high-risk medulloblastomas.
MDB-41. TARGETING EPIGENETIC REGULATORS TO INHIBIT GROUP 3 MEDULLOBLASTOMA MIGRATION
Authors: Jangde Nitish , Walter Thomas Jordan , Ayad Nagi
Published: June 2023

Medulloblastoma highly malignant type of childhood brain cancer which develops at the cerebellum. Medulloblastoma can be grouped into four molecular subtypes; Sonic Hedgehog (Shh), Wnt, group 3, and group 4 based on their molecular development. Mostly group 3 medulloblastoma are highly malignant subtype. Medulloblastoma migration from the cerebellum to the leptomeningeal space and spinal cord is critical for worsening the symptoms. Targeting the medulloblastoma migration would potentially attenuate the symptoms. Identifying potential epigenetic regulators and targeting them might be an effective approach to cure the symptoms in medulloblastoma patients. CRISPR epigenome library screening targeting more than 500 epigenetic factors by using more than 3000 sgRNA can help to identify potential epigenetic regulators to medulloblastoma migration. Group 3 medulloblastoma tumor is highly malignant so, we have selected a group 3 medulloblastoma human cell line D425 for our study. CRISPR epigenome library or sg RNA targeting 500 epigenetic genes was introduced into D425 cells with the help of lentiviral particles. The cells were antibiotically selected and expanded after selection. In vitro, trans-well migration assays were performed with technical and biological replicates. The cells that migrated through the transmembrane were collected and the cells which did not show any migration were also collected followed by enrichment. The DNA isolation followed by amplification of barcoded sequences identifiers tagged to different sgRNAs were size selected and undergone for Illumina NGS sequencing. The NGS sequencing results will reveal the key epigenetic factors involved in the migration of Group 3 medulloblastoma. After confirmation of pathway analysis and in vitro and in vivo validation would identify potential factors. This study will ultimately help us to find a potential epigenetic regulator for targeted therapy to inhibit migration of group 3 medulloblastoma to reduce the symptoms and combine with other effective drugs to establish synergistic effects for treatment.
MDB-42. UNCOVERING DYNAMIC CHANGES IN MEDULLOBLASTOMA ASSOCIATED VASCULATURE IN ZEBRAFISH
Authors: Morris Elysse , Daignault-Mill Sheena , Ju Robert J , da Silva Jason , Gordon Emma , Wainwright Brandon , Stehbens Samantha , Genovesi Laura , Lagendijk Anne
Published: June 2023

Medulloblastoma (MB) is an embryonal-derived lesion arising in the cerebellum, contributing to 20% of childhood brain tumours and 63% of intracranial embryonal tumours. Currently, standard of care includes surgical resection and chemotherapy, used in conjunction with radiation. While these treatments have significantly improved survival rates, the therapy side effects are detrimental to survivors’ quality of life. Furthermore, relapse occurs in 30% of patients and unfortunately these are untreatable and therefore fatal for 95% of patients. It is presumed that in patients that present with a recurrent tumour, initial treatment has been ineffective. A major cause of this can be the heterogenous vasculature in and around the tumour. Recent studies have identified that the blood brain barrier (BBB), in the context of MB, is highly heterogenous with differences in BBB cellular composition and integrity between MB sub-types and within single tumours. It remains unclear however, how these vascular differences emerge and what the primary defects are. This gap in our knowledge is mainly due to the lack of models that allow long-term live imaging. We have established a xenograft approach to examine human MB tumour cells in zebrafish embryonal brains. We have validated that human Medulloblastoma cells of the Group 3 (Gp3) MB subgroup, are viable in zebrafish brains. This work has also identified that in the presence of these human Gp3 MB tumour cells, the local vasculature becomes dysmorphic and tortuous over time. Timelapse imaging of these tumour and vasculature interactions demonstrates that there is a rapid and long ranging angiogenic response with new vessel sprouts growing towards the tumour cells. By utilising our large range of transgenic zebrafish lines, we will continue investigating how MB cells interact and alter distinctive BBB cell types and how these changes impact vessel function.
MDB-43. GRADIENT ENTROPY-BASED RADIOMIC RISK-SCORE FROM T1-WEIGHTED PRE-TREATMENT MRI SCANS CAN PREDICT SURVIVAL IN PEDIATRIC MEDULLOBLASTOMA
Authors: Bareja Rohan , Ismail Marwa , Martin Doug , Nayate Ameya , Yadav Ipsa , Labbad Murad , Tamrazi Benita , Salloum Ralph , Margol Ashley , Judkins Alexander , Iyer Sukanya , de Blank Peter , Tiwari Pallavi
Published: June 2023

BACKGROUND

Medulloblastoma (MB) is the most frequent malignant brain tumor in children with an inadequate 5-year survival rate of 70-75%. A key determinate in MB treatment (consisting of radiation, chemotherapy) is the accurate risk-stratification of patients into low- and high-risk. The current stratification approaches (Chang’s classification, molecular categorization) are sub-optimal in predicting individual patient outcomes. Reliable risk-assessment approaches can significantly impact treatment management. Our group previously developed a new radiomics feature COLLAGE that measures the orientation of local intensity gradients as an estimate of lesion heterogeneity. We hypothesize that the disorder (i.e., heterogeneity) in orientation of local per-voxel intensity measured by COLLAGE, will tease-out differences in patients with low - versus high-risk MB tumors.

METHODS

T1-weighted MRI scans of 49 pediatric MB patients were retrospectively collected from Children’s Hospital Los Angeles and Cincinnati Children’s Hospital Medical Center. Registration of the scans was performed via age-specific pediatric atlases, followed by skull stripping and bias correction. Ground truth annotations for tumor sub-compartments; enhancing tumor, edema, and non-enhancing tumor, were generated by two experienced radiologists. Then, 52 Collage features were extracted from each of these sub-compartments, followed by conducting a Lasso model and a cox-proportional hazards model to identify the top features for risk-stratification. A continuous risk score was created for every patient and a risk threshold was obtained from the fitted cox model to stratify patients into low- and high-risk.

RESULTS

Our risk-score consisted of 13 top COLLAGE features from edema and 14 from non-enhancing tumor sub-compartments, respectively, and demonstrated significant differences between low- and high-risk patients (p = .017 for edema, p =0.0027 for non-enhancing tumor).

CONCLUSION

Our preliminary analysis suggests that gradient-entropy radiomic risk score maybe able to predict overall survival in pediatric MB tumors. In future, we plan to include additional patients to perform independent multi-site analysis.
MDB-45. SELECTIVE B7-H3 INHIBITORS NI1 AND NI4 REDUCE AGGRESSIVENESS OF GROUP 3 MEDULLOBLASTOMA
Authors: Krishnan Prakadeeswari Gopala , Kanchan Ranjana , Doss David , Alfrefaei Hamdan , Agarwal Prachi , Chhonker Yashpal , Murry D J J , Trippier Paul , Mahapatra Sidharth
Published: June 2023

Medulloblastoma (MB) is a primary childhood malignancy of the central nervous system (CNS). Clinically heterogenous MB are sub-grouped into four molecular subgroups, i.e. Wingless (WNT), Sonic Hedgehog (SHH), Group 3, and Group 4. Among all, Group 3 MB (G3MB) is known to be the most aggressive form, with less than 50% five-year survival. G3MB are associated with large-cell/anaplastic (LCA) histology, distinctive methylation profile, amplification of MYC, and isochromosome 17q (i17q). Targeting these high-risk molecular features unique to G3MB has been challenging, necessitating alternative approaches to therapy for G3-MB. One innovative approach is immunotherapy, which is largely impeded by inhibitory immune checkpoints. B7 homolog 3 (B7-H3/CD276), an immunosuppressive immune checkpoint protein and member of B7 superfamily, is significantly enriched in pediatric malignancies of CNS including G3MB. The enhanced expression of B7-H3/CD276 has been associated with aggressive and metastatic potential. B7-H3/CD276 is also a primary target of miR-1253, a novel tumor suppressor gene silenced in G3MB. Using a structure-based drug discovery pipeline, we screened the ChemBridge library of compounds to discover selective B7-H3 small-molecule inhibitors. Selective B7-H3 inhibitors Ni1 and Ni4 exhibited strong binding scores, CNS penetrance, and oral bioavailability. In vitro, both compounds had appreciably low IC50 values of 3µM (Ni1) and 0.75µM (Ni4). Further, both compounds inhibited wound healing and colony formation. Ni1 shifted the thermostability of B7-H3, suggesting in vitro biding. Ni1 has also undergone PK/PD and MTD studies in vivo, showing stability in serum, good blood-brain barrier permeability, and a half-life of 8 hours. We are now elucidating B7-H3-activated downstream signaling through JAK2/STAT3 signaling and testing the in vivo efficacy for Ni1 against G3MB tumors in a murine model.
SURG-02. MAGNETIC RESONANCE-GUIDED HIGH-INTENSITY FOCUSED ULTRASOUND (MRGHIFU) FOR TREATMENT OF LOW GRADE GLIOMA IN A PEDIATRIC PATIENT
Authors: Chesney Kelsi , Patel Nirali , Keating Gregory , Packer Roger , Keating Robert
Published: June 2023

INTRODUCTION

Transcranial magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU) has demonstrated efficacy in the treatment of adult essential tremor through targeted thermoablation visualized in real-time with MR thermography. The minimally invasive nature of MRgHIFU and lack of ionizing radiation makes it an appealing treatment modality for pediatric patients. There is limited data describing MRgHIFU for pediatric brain tumors. This case report describes the use of MRgHIFU to treat a low grade glioma in a pediatric patient.

METHODS

A prospective, non-randomized, single-arm study enrolled patients 8-22 years old with benign intracranial tumors requiring intervention to be treated with the ExAblate 4000 System. Clinical and radiographic examinations were performed at the following intervals after treatment: 1 day, 14 days, 3 months, 6 months, and 1 year.

RESULTS

One patient was treated with MRgHIFU in 2022. A 12 year-old female with headaches and Neurofibromatosis Type 1 (NF1) without prior medical or surgical treatment presented with a progressive enhancing lesion in the right parieto-occipital region. Stereotactic biopsy confirmed pathological diagnosis of a low-grade glioma. MRgHIFU was used to treat the lesion with 5 sonications ranging 600-800 watts resulting in immediate T2 and FLAIR changes. There were no complications or adverse events. MRI demonstrated slight volume reduction after one year. The patient scored herself a 7 on the Patient Global Impression of Change scale for considerable improvement. Her headaches improved and she participates actively in school and sports.

CONCLUSION

MRgHIFU is an attractive alternative to open craniotomy and/or radiation for pediatric patients with benign brain tumors. In our experience with one patient, the use of MRgHIFU for treatment of a low-grade glioma demonstrated safety in addition to radiographic disease control at 1 year with favorable patient impression scores. Additional patient enrollment and extended follow-up time will be necessary to determine generalizability and therapeutic longevity.
SURG-05. MRI-GUIDED FOCUSED ULTRASOUND BLOOD-BRAIN BARRIER DISRUPTION INCREASES DRUG DELIVERY AND EFFICACY IN AN ORTHOTOPIC DIPG MODEL
Authors: Martinez Payton , Nault Genna , Steiner Jenna , Wempe Michael , Pierce Angela , Brunt Breaunna , Slade Mathew , Mongin Andrew , Song Jane , Song Kang-Ho , Ellens Nicholas , Serkova Natalie , Green Adam , Borden Mark
Published: June 2023

Diffuse intrinsic pontine glioma is the most common and deadliest pediatric brainstem tumor and is difficult to treat with chemotherapy in part due to the blood-brain barrier (BBB). Focused ultrasound (FUS) and microbubbles (MBs) have been shown to cause BBB disruption (BBBD), allowing larger chemotherapeutics to enter the parenchyma. Panobinostat is an example of a promising in vitro agent in DIPG with poor BBB penetrance. In this study, we hypothesized that using FUS to disrupt the BBB allows higher concentrations of panobinostat to accumulate in the tumor, providing a therapeutic effect. Mice were orthotopically injected with a patient-biopsied DIPG cell line, BT-245. After two weeks of growth, MR images guided FUS targeting to the tumor location. Microbubbles (25µl/kg, IV) and FUS (Frequency: 1.515 MHz, PNP: 0.77MPa, PRF: 1Hz, PL: 10ms, treatment time: 3 minutes) were applied to half the mice. Passive cavitation data (PCD) was collected and analyzed. Panobinostat was given (10mg/kg IP) to all mice. After 1.5 hours, a subset of mice were sacrificed to determine the concentration of panobinostat in tumor and cortex areas. We showed a 3-fold drug concentration increase in the tumor region while only slightly increasing the concentration in the forebrain. The remaining mice received three weekly treatments. Half were treated with FUS/MB and panobinostat, while others received panobinostat only. MRI was taken weekly to evaluate BBBD extent and tumor growth. PCD during treatments showed ideal cavitation of microbubbles illustrating safety and consistency across all treatments. The combination of panobinostat and FUS exhibited a tumor size decrease of 71% on MRI compared to panobinostat alone. Furthermore, FUS/MB improved the mean survival from 21 to 31.5 days (p=0.0001). Our study demonstrates that FUS-mediated BBBD can increase the delivery of panobinostat to an orthotopic DMG tumor, providing a strong therapeutic effect and increased survival.
OTHR-02. CHIMERIC AURORA A KINASE (AURKA) DEGRADERS EFFICIENTLY TARGET N-MYC
Authors: Valinciute Gintvile , Eing Lorenz , Mihalic Jeffrey , Casey Colleen E , Tian Hua , Adhikari Bikash , Guiducci Cristiana , Rountree Ryan , Grohmann Christoph , Sridharan Sangita , Lu Ya-Wen , Vezina-Dawod Simon , Wegrzyniak Eric , Chaterjee Abhinav , Hansen Gwenn M , Maris John M , Mossé Yael P , Eilers Martin , Wolf Elmar , Roussel Martine F
Published: June 2023

MYC family proteins are primary drivers of oncogenic processes in a variety of cancer histologies. N-myc overexpression and amplification induce aggressive pediatric cancers, the most common of which are solid extracranial tumors in children (neuroblastoma, NB) and malignant pediatric CNS tumors (medulloblastoma, MB). Due to the oncogenic addiction observed in these tumor types, N-myc is considered an attractive therapeutic target. However, direct small molecule targeting of N-myc remains technically challenging. Alternative approaches to target this pathway include inhibiting proteins thought to stabilize N-myc, such as Aurora A kinase (AURKA). While inhibition of AURKA was found to be effective in preclinical tumor studies, no AURKA inhibitors have been approved for clinical use due to a lack of efficacy. Here, we aim to develop chimeric degrader molecules suitable for preclinical and clinical use that degrade AURKA and concomitantly reduce N-myc levels. We used automated solid-phase synthesis to generate a library of >1000 chimeric degraders using derivatives of six known AURKA ligands (Series 1-6). Due to the limitations of using N-myc-driven MB cells in vitro, we employed NB cells as the proof-of-concept model. While the degraders based on five of the ligands showed efficient AURKA degradation, only degraders based on series 3 and 6 could also diminish N-myc. Selected series were further characterized in pharmacokinetic and pharmacodynamic experiments using NB tumor xenografts implanted in the flank in CD1-nude mice. In summary, chimeric degraders based on two individual AURKA ligands efficiently degraded AURKA and N-myc in vitro and in vivo, providing the foundation for further development of novel therapies for patients with N-myc-driven cancers. Further studies will focus on assessing antitumor properties of lead candidates in NB and patient-derived orthotopic MB xenograft models.
OTHR-07. CIRCULATING MIRNAS AS A NON-INVASIVE MONITORING TOOL FOR PEDIATRIC BRAIN TUMORS
Authors: Coyle Anne , Rathi Komal , Arif Shehbeel , Hollawell Madison , Beck Christopher , Choudhari Namrata , Smith Tiffany , Naqvi Ammar , Madsen Peter , Tucker Alexander , Storm Phillip , Resnick Adam , Foster Jessica , Koptyra Mateusz
Published: June 2023

Current management of pediatric brain tumor patients relies on imaging as the only non-invasive tool available for monitoring therapeutic response and tumor progression. Results are often inconclusive and unable to capture biological changes that presage progression on imaging. Circulating miRNA provides an attractive non-invasive platform because miRNA’s essential role in regulating gene expression, stability in bio-fluids, selective over-expression in tumors, and subsequent active release from tumors into the extracellular environment. We aimed to establish the prognostic and monitoring value of miRNA biomarkers for pediatric brain tumors. We performed miRNA profiling of CSF (n=33) and plasma (n=53) samples across a cohort of 54 pediatric brain tumors from 6 histologies (low grade glioma, ependymoma, germ cell tumor, medulloblastoma, atypical teratoid rhabdoid tumor and high-grade glioma). We utilized unsupervised consensus clustering, differential expression, and machine learning methods to explore miRNA biomarkers. Plasma miRNA signatures were correlated with WHO Grade while CSF signatures revealed a correlation with leptomeningeal disease and higher disease burden (p<0.05). The expression of circulating miRNA revealed histology-specific signatures for low grade glioma, medulloblastoma and germinoma in plasma and CSF (p<0.05). We identified miRNA signatures of significant translational value: (1) A medulloblastoma specific miRNA in CSF can serve as a potential biomarker for tumor monitoring (medulloblastoma specificity was confirmed in independent tissue-based dataset); (2) Pilocytic astrocytoma can be distinguished from high grade glioma in CSF; (3) Most intriguingly, in plasma, miRNA expression identified pilocytic astrocytoma that had relapsed in several months after initial intervention (p<0.05). These results support circulating miRNA in plasma and CSF as biomarkers of diverse clinical diagnostic and prognostic measures. Further utilization of this approach provides unique platforms to inform liquid biopsy-based management in the clinical setting.