bluuebunny/crossref_metadata_2025_split huggingface dataset:
ATRT-16. THE PI3K INHIBITOR PAXALISIB COMBINES SYNERGISTICALLY WITH THE MEK INHIBITOR MIRDAMETINIB TO TARGET ATYPICAL TERATOID/RHABDOID TUMORS
Authors: Malebranche Kristen , Findlay Tyler , Geethadevi Anupa , Eberhart Charles , Raabe Eric , Rubens Jeffrey 
Published: June 2023

Abstract
Atypical teratoid/rhabdoid tumors (AT/RT) are aggressive pediatric brain tumors and the most common malignant brain tumors of infancy. The four-year event-free survival rate is only 37%. There are limited treatment options for patients with relapsed AT/RT, but precision therapies may help improve survival for patients with this deadly disease. We have previously identified strong activation of the PI3K-AKT-mTOR (mTOR) signaling pathways in AT/RT. Paxalisib is a highly brain-penetrant PI3K inhibitor acting upstream of mTOR. We find that Paxalisib slows tumor growth in orthotopic xenograft models of AT/RT and extends median survival from 40 to 54 days (p=0.001, log-rank test). RNASeq after mTOR pathway inhibition identifies reflexive activation of the RAS-RAF-MEK-ERK (MAPK) pathway as a possible mechanism of therapy resistance (KEGG pathway analysis). The RAS-RAF-MEK-ERK (MAPK) pathway plays a pivotal role in regulating cell growth and survival and activation of the pathway which contributes to the aggressive growth of numerous cancers. Mirdametinib is a small, allosteric MEK inhibitor currently used in clinical trials for both pediatric low- and high-grade gliomas (PD0325901). We find that dual inhibition of both the mTOR and MAPK pathways by Paxalisib and Mirdametinib synergize to reduce AT/RT growth and viability (Bliss synergy score 16.77). Paxalisib also combines with Mirdametinib to induce high levels of apoptosis and cell senescence (as determined by western blot: cPARP, pRB, P21, P16). Naïve treatments and a current survival study in mice bearing AT/RT orthotopic tumors suggest that combination therapy decreases mTOR and MAPK pathway activation (as determined by western blot). These data support using Paxalisib and Mirdametinib combination therapy as a promising novel therapy to treat relapsed AT/RT.
BIOL-06. UNDERSTANDING OLIGODENDROCYTE PROGENITOR CELL CONTRIBUTION TO GLIOMAGENESIS USING A NOVEL PHARMACOGENETIC ABLATION TOOL
Authors: Xing Lulu , Merson Tobias , Petritsch Claudia 
Published: June 2023

Abstract
In the central nervous system (CNS), gliomas represent almost 50% of all pediatric tumors and due to their complex histological and biological heterogeneity, aggressive standard treatment consisting of surgery and chemoradiotherapy remains ineffective. As a result, more biologically based therapies are urgently needed, and this requires a deeper knowledge of the etiology and biology of gliomas and the tumor microenvironment. Oligodendrocyte progenitor cells (OPCs) are a potential origin of human gliomas (as suggested by studies in genetically engineered mouse models) and human OPC-like tumor cells contribute to tumor heterogeneity and malignancy. Resident (non-neoplastic) OPCs have been found to intermix with glioma cells and proliferate within the tumor microenvironment. The significance of the interactions of resident OPCs and glioma cells remains unknown. We hypothesize that resident OPCs functionally integrate into the tumor cell network and affect tumor properties. We have generated a novel mouse model of conditional OPC ablation to overcome methodological challenges of most current approaches that often result in partial and transient OPC ablation, which limits our understanding of long-term function of OPCs. Here in our study, we have successfully developed a novel pharmacogenetic model of conditional OPC ablation, eliminating 98.6% of all OPCs throughout the mouse brain for up to 12 days post ablation. In the future, we plan to combine the mouse model of complete OPC ablation with orthotopic glioma models to reveal the longitudinal and spatial functional roles and the necessity for resident OPCs in the tumor context. Understanding the OPC-tumor cell crosstalk by using our state-of-the-art approach at both cellular and molecular levels will have significant clinical implications for improving treatment for patients with pediatric gliomas.
BIOL-08. RADIATION DRIVES METASTASIS IN MEDULLOBLASTOMA THROUGH AN INFLAMMATORY PROCESS
Authors: Nor Carolina , Kharas Kaitlin , Rasnitsyn Alexandra , Vladoiu Maria , Ramaswamy Vijay , Raleigh David , Taylor Michael 
Published: June 2023

Abstract
Current treatment for medulloblastoma is comprised of surgery, radiotherapy (RT) and/or chemotherapy. Although the primary tumor is controlled with this approach, recurrent metastatic disease is ubiquitously fatal. However, little is known about the biology of metastatic recurrences in medulloblastoma. In the present study, we observe across 3 non-overlapping cohorts of infant medulloblastoma that patients recur locally without focal RT and metastatically after focal RT. Using 3 independent murine flank xenograft medulloblastoma models, we found that the incidence of leptomeningeal metastasis was significantly increased in mice that received RT compared to sham controls. We have also found a significant increase in viable circulating tumor cells after RT. Our multi-omics (bulk RNA-seq, scRNA-seq and proteo/phosphoproteomics) approach using immunocompetent sporadic medulloblastoma models treated with RT showed activation of the innate inflammatory response through the overexpression of chemokines, cytokines and activation of immune cell types. In situ analysis of protein expression after RT showed a gradual increase in the abundance of macrophages, neutrophils and dendritic cells after RT, suggesting increased permeability and cell trafficking across the blood brain barrier. Applying live intravital microscopy using a low molecular weight vascular dye (150kDa), we observed a striking increase in blood vessel permeability in RT vs sham-treated brain tumors. Our observations support a model where RT drives metastasis through inflammation. To test this, we applied lipopolysaccharide (LPS), an inflammation inducing treatment, to a sporadic murine medulloblastoma model which significantly increased the metastatic burden. We then treated a xenograft model with dexamethasone in combination with RT, which resulted in total abrogation of metastatic dissemination compared to RT alone. Collectively, our findings suggest that while external beam irradiation is an effective and essential treatment for medulloblastoma, it may facilitate metastatic dissemination through an inflammation-induced process. These findings can help inform potential approaches to prevent disseminated relapsed disease.
BIOL-09. PROTEOMIC ANALYSES REVEAL THAT CO-CULTURE OF DIFFUSE INTRINSIC PONTINE GLIOME (DIPG) WITH CORTICAL ORGANOIDS ALTERS CELL ADHESION, DNA SYNTHESIS AND REPLICATION, AND DENDRITIC GROWTH SIGNALLING
Authors: Prior Victoria , Maksour Simon , Miellet Sara , Hulme Amy , Mirzaei Mehdi , Wu Yunqi , Dottori Mirella , O’Neill Geraldine 
Published: June 2023

Abstract
Diffuse Intrinsic Pontine Gliomas (DIPGs) are deadly brain cancers in children for which there is currently no effective treatment. In part, this can be attributed to preclinical models that lack essential elements of the in vivo tissue environment, resulting in treatments that appear promising preclinically, but fail to result in effective cures. Recently developed co-culture models combining stem cell-derived brain organoids with brain cancer cells provide tissue dimensionality and a human-relevant tissue-like microenvironment. As these models are technically challenging and time consuming it is imperative to establish whether interaction with the organoid influences DIPG biology and thus warrants their use. To address this question, we cultured DIPG cells with GFP-expressing cortical organoids. We created “mosaic” co-cultures enriched for tumour cell-neuronal cell interactions, where disaggregated spheroids and organoids were mixed and allowed to reform, versus “assembloid” co-cultures enriched for tumour cell-tumour cell interactions, where preformed tumour spheroids and organoids were combined. Sequential window acquisition of all theoretical mass spectra (SWATH-MS) was used to analyse the proteomes of DIPG fractions isolated by flow-assisted cell sorting. Control proteomes from DIPG spheroids were compared with DIPG cells isolated from mosaic and assembloid co-cultures. This revealed that tumour cell adhesion was reduced, and DNA synthesis and replication were increased, in DIPG cells under either co-culture condition. By contrast, the mosaic co-culture was alone associated with pathways implicated in dendrite growth. We propose that co-culture with brain organoids is a valuable tool to parse the contribution of the brain microenvironment to DIPG tumour biology.
BIOL-11. PRECLINICAL MODELLING OF PEDIATRIC BRAIN TUMORS USING ORGANOID TECHNOLOGY
Authors: Roosen Mieke , Meulenbroeks Chris , Stathi Phylicia , Maas Joris , Morscio Julie , Bunt Jens , Kool Marcel 
Published: June 2023

Abstract
Molecular characterization has resulted in improved classification of pediatric brain tumors, leading to many novel (sub)types with distinct oncodriving events. To study tumor biology and to perform translational research on each of these tumors, preclinical models are essential. However, we are currently lacking sufficient models, especially in vitro, to represent each (sub)type and their heterogeneity.
To generate large series of preclinical in vitro models for pediatric brain tumors, we are using organoid technology. Cells from patient samples and patient-derived xenograft samples have been taken into culture to establish 3D organoids using tumor type specific culture conditions. These organoid lines retain the molecular characteristics of the original tumor tissue. They can be used to perform high-throughput drug screens, genetic manipulations, and co-cultures with, for instance, immune cells.
Viable tissue is not always available for all tumor (sub)types and specific oncodrivers. To circumvent this lack of tissue, we can also induce tumors in vitro. Therefore, we generate cerebral and cerebellar brain organoids from human pluripotent stem cells. These organoids mimic human developing brain cells and can be genetically manipulated to model different brain tumor types. These genetically engineered brain tumor models allow us to study the cellular origins of pediatric brain tumors and the different tumor driving mechanisms. Tumors induced in the brain organoids histologically and molecularly resemble human patient samples based on (single cell) transcriptomic analyses. Moreover, the tumor cells are able to establish xenografts in mouse brains.
In summary, organoid technology provides a novel avenue to establish in vitro models for pediatric brain tumors. At the meeting we will present data for various new ependymoma, medulloblastoma and embryonal brain tumor organoid models.
BIOL-23. LOSS OF MICRORNAS COOPERATES WITH TUMOR SUPPRESSORS TO INITIATE MYC-DEPENDENT METASTATIC MEDULLOBLASTOMA
Authors: Llaguno Sheila Alcantara , Nazarenko Inga , Chen Yuntao , Sun Daochun , Gudenas Brian , Saulnier Olivier , Rocca Gaspare La , Pedraza Alicia , Burns Dennis , Bale Tejus , Ventura Andrea , Northcott Paul , Taylor Michael , Parada Luis 
Published: June 2023

Abstract
To determine the role of microRNA regulation in brain tumor development, we incorporated a conditional allele of the microRNA processing enzyme Dicer to a glioma mouse model based on inactivation of the tumor suppressors Nf1, Trp53, and Pten using the Nestin-creERT2 transgene. Loss of Dicer and tumor suppressors at adult ages led to glioma development; however, mutant mice tamoxifen induced at early postnatal ages developed medulloblastoma (MB) instead of glioma. The switch in tumor spectrum occurred with 100% penetrance and the cerebellar tumors were histologically indistinguishable from human MB. The minimum genetic mutations required for MB formation were Dicer1 and Trp53, while additional loss of Pten produced more invasive tumors with leptomeningeal metastasis. Analysis of tumor transcriptome and MB subtype-specific markers show that Dicer tumors most resemble human Sonic Hedgehog (SHH) MB. The presence of leptomeningeal metastasis, Trp53 loss and upregulation of Mycn and Gli2 in the setting of activated Shh signaling suggests that this model phenocopies extremely high risk p53-mutated SHH MB, which carries poor prognosis and is associated with the majority of treatment failures in SHH MB. Analysis of pre-symptomatic mutant mice showed proliferative defects and retained cells in the external granule cell layer (EGL), suggesting that tumors may arise from cerebellar granule neuron precursors (CGNPs). However, targeting CGNPs using Math1-creERT2 did not lead to MB development, suggesting that an earlier EGL precursor may be required for tumorigenesis. Dicer tumors exhibit reduced microRNAs and RNA-induced silencing complexes consistent with loss of Dicer. One of these downregulated microRNAs, miR-101, is a regulator of Mycn and its overexpression leads to Mycn downregulation and inhibition of MB growth. Likewise, genetic and pharmacologic inhibition of Myc leads to inhibition of MB growth. These studies demonstrate a role for microRNAs in Myc-dependent MB development and show an alternative pathway for SHH MB tumorigenesis.
DIPG-06. PRECLINICAL EVALUATION OF A NOVEL ACVR1 INHIBITOR IN DIFFUSE INTRINSIC PONTINE GLIOMAS
Authors: Kumar Shiva Senthil , Shoffner Rebecca , Devine Brendan , Drissi Rachid 
Published: June 2023

Abstract
Diffuse intrinsic pontine glioma (DIPG) is an incurable brain disease in children. DIPG is refractory to current available therapies. Hence, new therapeutic approaches are urgently needed. About 80% of DIPGs harbor histone 3 lysine to methionine (H3K27M) mutation, in H3-3A (encoding H3.3 histone) and H3C2 (encoding H3.1 histone) genes. One quarter of DIPG tumors harbor somatic mutations in ACVR1 gene, encoding the serine/threonine kinase receptor ALK2. ACVR1 mutations co-segregate with H3.1K27M mutation, representing a specific tumour subtype with distinct clinicopathological and molecular features. These mutations are associated with an aberrant activation of SMAD pathway believed to promote cell proliferation in DIPGs. In the present studies, we evaluated the effectiveness of an orally bioavailable ALK inhibitor, TP-0184 (Tolero Pharmaceuticals) in ACVR1 mutated (ACVR1-mut) and wildtype (ACVR1- WT) DIPG models. Our results indicate that TP-0184 effectively inhibited cell proliferation in primary-patient derived DIPG cell lines. However, we did not observe any selectivity toward ACVR1 mutations. TP-0184 does not induce cell death, but rather cell cycle inhibition, arresting cells in G2/M phase. Interestingly, when treated with ionizing radiation (IR), ACVR1-mut cells preferentially activated SMAD signaling compared to ACVR1-WT. We are currently evaluating the combination efficacy of TP-0184 with IR in our in vitro and in vivo DIPG models. Data on tumor growth kinetics, survival and the effect on SMAD signaling pathway will be presented and discussed.
DIPG-09. ATOVAQUONE RADIOSENSITISES DIFFUSE MIDLINE GLIOMAS BY INHIBITING MITOCHONDRIAL METABOLISM AND HYPOXIA
Authors: Mudassar Faiqa , Chang Cecilia , Ing Prunella , Nguyen Sandy , Cook Kristina M , Warnken Zachary N , O’Neill Geraldine , Shen Han , Hau Eric 
Published: June 2023

Abstract
Diffuse Midline Glioma (DMG) is a uniformly fatal paediatric brainstem tumour with median survival of less than 1 year. Radiotherapy has been the only effective treatment for decades, but most DMGs recur within several months due to radioresistance. The hypoxic tumour microenvironment, a main feature of solid tumours including gliomas, is a major contributor to radioresistance and impedes the efficacy of radiotherapy. Therefore, alleviating tumour hypoxia to enhance the effectiveness of radiotherapy is a therapeutic strategy to improve survival outcomes of DMG patients. Here, our strategy is to decrease the oxygen consumption rate (OCR) of DMG cells by targeting their mitochondria, which in turn will alleviate hypoxia by sparing more oxygen and subsequently improve the radiosensitivity of DMG cells. Specifically, we performed a high-throughput screening to identify potent OCR inhibitors using a library of 1963 FDA-approved drugs. The most promising OCR inhibitor identified was atovaquone, a drug used for treatment of pneumocystis pneumonia and malaria. We found that atovaquone inhibited mitochondrial metabolism of DMG cells by specifically targeting the mitochondrial complex III. It induced the formation of mitochondrial reactive oxygen species suggesting that it increases oxidative stress. It alleviated hypoxia and decreased the expression of hypoxia-inducible factor-1a in several 3-dimensional DMG neurospheres and improved the radiosensitivity of a range of DMG cultures. To overcome the issues of poor bioavailability of commercially available atovaquone resulting in low therapeutically effective brain concentrations, we tested its efficacy against the amorphous solid dispersion (ASD) atovaquone formulation which appears to enhance the atovaquone levels in the brain. We found that both the formulations inhibited OCR and hypoxia at similar doses and improved the radiosensitivity of DMG. With these promising findings, our further work is assessing the in vivo efficacies of commercially available atovaquone and ASD atovaquone formulation using orthotopic DMG models.
DIPG-12. OUTCOMES IN PEDIATRIC MALIGNANT CENTRAL NERVOUS SYSTEM TUMORS UTILIZING TEMOZOLOMIDE, BEVACIZUMAB, AND IRINOTECAN
Authors: Reel Sarah , Smiley Natasha Pillay , Hummel Trent , Lane Adam 
Published: June 2023

Abstract
High-grade glioma (HGG) and diffuse intrinsic pontine glioma (DIPG) are the most common high-grade glial tumors in pediatrics. Hummel et al. assessed the feasibility of bevacizumab (BVZ) ± temozolomide (TEM) with radiation, followed by BVZ, irinotecan (IRO) ± TEM. The regimen conferred no survival benefit to patients with DIPG. The study was limited by sample size. Further defining efficacy of this therapy is important. We aimed to examine the outcomes of patients with HGG and DIPG treated with BVZ, IRO, and TEM. This is a retrospective review of patients treated at Cincinnati Children’s Hospital from 03/2005 to 10/2022. We examined progression-free survival (PFS) and overall survival (OS). Descriptive analyses were used to examine age, sex, diagnosis, and tumor location. 47 patients were treated with BVZ, IRO ± TEM. Patients were 55% female and 45% male. Average age at diagnosis was 12 years. The diagnoses included patients with HGG (45%), DIPG (51%), and other tumor types (4%). 79% of patients were treated at initial diagnosis with the regimen of BVZ in addition to IRO ± TEM. 21% of patients were treated at progression. Median OS for patients with DIPG and HGG was 12.4 months and 35.9 months, respectively. 3-year OS for DIPG was 10.8% (SE 7.2%) and for HGG it was 48.6% (SE 11.0%). Median PFS for DIPG and HGG was 7.7 and 19.0 months, respectively. 1-year PFS for DIPG was 31.9% (SE 10.7%). For HGG it was 65.6% (SE 10.6%). 3-year PFS for HGG was 20.2% (SE 9.0%). The limitations of this study are that newly diagnosed and recurrent patients are included and the study does not examine radiologic and biologic data. Results from this study show promising data for OS and PFS. Additional studies are needed to further examine larger cohorts of patients to demonstrate survival benefit from this regimen.
DIPG-15. CONCURRENT GB-13 (IL13.E13K-PE4E) IMPROVES THE EFFICACY OF RADIATION THERAPY IN DIFFUSE INTRINSIC PONTINE GLIOMA
Authors: Rechberger Julian S , Schrecengost Randy S , Zhang Liang , Ge Jizhi , Nonnenbroich Leo F , Sarkaria Jann N , Daniels David J 
Published: June 2023

Abstract
Diffuse midline glioma with H3 K27 alterations (DMG) is the most aggressive primary malignant brain tumor in the pediatric population. Radiation therapy (RT) is the standard-of-care; however, it has not demonstrated a significant improvement in overall survival or stalled disease progression, and children usually succumb to disease within 12-15 months of diagnosis. Consequently, finding efficient treatments for DMG remains one of the most critical unmet needs in modern neuro-oncology. Interleukin 13 receptor subunit alpha 2 (IL-13Rα2) is a cell-surface receptor upregulated in ~80% of DMG versus normal brain, posing a potentially promising therapeutic target. Immunotherapies harnessing IL-13Rα2 to selectively delivery cytotoxic payloads, such as pseudomonas exotoxin A (PE), to tumor cells have been previously demonstrated to be safe in DMG patients and efficacious in preclinical models of DMG with high IL-13Rα2 expression using convection-enhanced delivery (CED). Furthermore, there is evidence that PE-based therapies can sensitize cells to RT. In this study, we utilized in vitro and in vivo models of DMG to evaluate clinically-relevant combination treatments of RT and the IL-13/PE immunotoxin GB-13 (IL13.E13K-PE4E). GB-13 improved the effectiveness of low-dose RT in multiple DMG cell lines by promoting caspase activation, which boosted apoptotic cell death. Intratumoral administration of GB-13 via chronic CED decreased tumor burden and prolonged survival in both DMG patient-derived orthotopic xenograft and genetically engineered mouse models. When GB-13 and RT were administered concurrently, this impact became even more prominent, informing future preclinical and clinical investigation of a potentially efficacious therapeutic approach in a subset of DMG.
DIPG-16. ACUTE VERSUS PROLONGED CONVECTION-ENHANCED DELIVERY OF ALISERTIB INTO H3 K27M-MUTANT MODELS OF DIFFUSE MIDLINE GLIOMA
Authors: Rechberger Julian S , Zhang Liang , Ge Jizhi , Daniels David J 
Published: June 2023

Abstract
Convection-enhanced delivery (CED) is a potentially promising strategy to administer therapeutics directly into the brainstem of children harboring H3 K27-altered diffuse midline glioma (DMG). While early-phase clinical trials have demonstrated the safety of this technique, efficacy has yet to be achieved. Here, we describe how different variations of CED may be exploited to extend survival in a DMG murine patient-derived orthotopic xenograft model. Either 1-day (8 µL/hr) or 7-day (1 µL/hr) continuous CED infusions were performed to deliver an equivalent volume of the aurora kinase inhibitor alisertib to the mouse brainstem. Bioluminescence and magnetic resonance images were acquired to monitor tumor progression, validate CED catheter positioning, and analyze infusion-related imaging changes. Both infusion regimens significantly prolonged survival versus control (median survival benefit of 6.5 and 8 days, p=0.03 and p=0.01, for 1-day and 7-day CED, respectively). Postmortem examination of brains revealed no signs of tissue necrosis, cavitary lesions, or cellular (inflammatory) infiltrate at the site of infusion. However, the tumor parenchyma surrounding the cannula tract was markedly hypocellular in treated animals. Alisertib induced a robust increase in H3 K27 trimethylation along with decreased H3 K27M and Ki-67. Our findings indicate that CED of alisertib is well tolerated and effective, in both the acute and prolonged setting, underscoring the potential of this approach in the management of DMG.