bluuebunny/crossref_metadata_2025_split huggingface dataset:
GERM-04. PRIMARY INTRACRANIAL GERM CELL TUMORS ARE MORE PREVALENT AMONG PEDIATRIC PATIENTS OF ASIAN/PACIFIC ISLANDER RACE/ETHNICITY IN THE UNITED STATES
Authors: Lamba Nayan , Iorgulescu Bryan 
Published: June 2021

Abstract

Introduction
Primary intracranial germ cell tumors (GCTs) appear to be more prevalent among pediatric patients in eastern Asia than in the U.S. Herein we use cancer registry data to evaluate whether GCT prevalence differs by race/ethnicity among U.S. pediatric patients.

Methods
Pediatric patients (age≤14) presenting between 2004–2017 with a primary intracranial GCT were identified by ICD-O-3 histological and topographical coding from the National Cancer Database (comprising &gt;70% of cancers newly-diagnosed cancers in the U.S.), and categorized by NICHD age stages. Patients’ age, sex, race/ethnicity, and overall survival, and tumor location and size were evaluated.

Results
889 pediatric patients with primary intracranial GCTs were identified, which were overwhelmingly male (64.8%) and pure germinomas (64.0%). Non-germinomatous (24.5%) and mixed (11.5%) tumor types were in the minority. Overall, primary GCTs comprised 4.9% of intracranial tumors in pediatric males and 2.9% of intracranial tumors in pediatric females. Asian/Pacific Islander pediatric patients in the U.S. had a notably higher prevalence of GCTs: among Asian/Pacific Islander males, 10.6% of all brain tumors were GCTs, compared to only 4.5% in White non-Hispanic patients, 2.8% in Black non-Hispanic patients, and 6.0% in Hispanic patients. Despite the much lower prevalence of GCTs among female patients overall, this predominance also persisted for Asian/Pacific Islander females, among whom 7.5% of brain tumors were GCTs, compared to only 2.5% in White non-Hispanic patients, 2.4% in Black non-Hispanic patients, and 4.1% in Hispanic patients. Overall, 9.4% of pediatric primary intracranial GCTs occurred in patients of Asian/Pacific Islander race/ethnicity, in contrast to 4.0% of diffuse astrocytic/oligodendroglial tumors, 2.8% of other astrocytic tumors, or 4.6% of embryonal tumors.

Conclusions
Primary intracranial GCTs affect a substantially larger proportion of both male and female pediatric patients of Asian/Pacific Islander race/ethnicity in the United States.
HGG-04. TARGETING GABAERGIC NEURON-GLIOMA SYNAPSES IN DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG) THROUGH ANTI-EPILEPTIC DRUG REPURPOSING
Authors: Barron Tara , Mehta Vilina , Woo Pamelyn , Monje Michelle 
Published: June 2021

Abstract
Pediatric high-grade gliomas, including diffuse intrinsic pontine glioma (DIPG), are the leading cause of brain cancer-related death in children. While enormous progress has been made in recent years for many forms of cancer, high-grade gliomas remain seemingly intractable, indicating that fundamental aspects of glioma growth are not yet sufficiently understood. Neuronal activity drives glioma growth both through paracrine signaling and through direct neuron-to-glioma synapses. Recently glutamatergic, AMPA receptor-dependent synapses were discovered between microenvironmental neurons and malignant glioma cells. The depolarizing current that results from synaptic and other forms of electrical neuron-glioma signaling promotes pediatric high-grade glioma proliferation and regulates growth. Neuron-glioma cell synapses mediated by other neurotransmitters remain largely unexplored, though glioma cells express genes encoding neurotransmitter receptors such as GABAA receptor subunits. Using whole-cell patch clamp electrophysiology in patient-derived DIPG xenografts, we have identified functional GABAergic neuron-to-glioma synapses mediated by GABAA receptors. GABAergic input has a depolarizing effect on glioma cells, but the magnitude of depolarization is heterogeneous between high-grade glioma subtypes and between patient-derived DIPG xenograft models. As membrane depolarization increases glioma proliferation, depolarizing GABAergic inputs to glioma cells could promote DIPG progression. Drugs that stimulate GABA signaling, such as benzodiazepines, are often given to pediatric glioma patients to treat nausea, seizures or anxiety. In patient-derived DIPG xenograftn models, lorazepam, a benzodiazepine that increases GABAA receptor conductance, increases glioma growth. Conversely, levetiracetam, an anti-epileptic drug that reduces synaptic transmission including at GABAergic neuron-glioma synapses, reduces glioma proliferation in patient-derived DIPG xenografts. This emerging understanding of brain cancer neurophysiology reveals new therapeutic targets and highlights commonly used drugs about which more study is required in this disease context.
HGG-05. NEURONAL ACTIVITY PROMOTES PEDIATRIC HIGH-GRADE GLIOMA GROWTH THROUGH A NLGN3-CSPG4 SIGNALING AXIS
Authors: Gillespie Shawn , Kim Yoon , Geraghty Anna , Woo Pamelyn , Monje Michelle 
Published: June 2021

Abstract
High-grade gliomas, including diffuse intrinsic pontine glioma (DIPG), are a lethal group of cancers whose progression is strongly regulated by neuronal activity {Venkatesh 2015}{Venkatesh 2017}{Venkatesh 2019}. One way in which glioma cells sense neuronal activity is via interaction with the ectodomain of post-synaptic adhesion protein neuroligin-3 (NLGN3), which is cleaved and released into the tumor microenvironment (TME) by the sheddase ADAM10. This interaction drives glioma growth, but the relevant binding partner of shed NLGN3 (sNLGN3) on glioma cells is currently unknown. Here, we report that sNLGN3 binds to chondroitin sulfate proteoglycan 4 (CSPG4), in turn inducing regulated intramembrane proteolysis (RIP) of CSPG4, and initiating a signaling cascade within DIPG cells to promote tumor growth. CSPG4 RIP involves activity-regulated ectodomain shedding by ADAM10 and subsequent gamma secretase-mediated release of the intracellular domain in healthy oligodendroglial precursor cells (OPCs), putative cells of origin for several forms of high-grade glioma {Sakry 2014}{Nayak 2018}. Incubation of high-grade glioma cells or healthy OPCs with recombinant NLGN3 is sufficient to augment ADAM10-mediated ectodomain release of CSPG4 and subsequent gamma secretase-mediated cleavage of the CSPG4 intracellular domain (ICD). Pre-treatment of glioma cells or OPCs with an ADAM10 inhibitor entirely blocks NLGN3-induced CSPG4 shedding. Acute depletion of CSPG4 via CRISPR gene editing renders glioma cells insensitive to the growth-promoting effects of NLGN3 application in vitro. We are now performing experiments to better discern how the CSPG4 ICD regulates signaling consequences downstream of sNLGN3 binding. In addition, we are using surface plasmon resonance to investigate whether the shed ectodomains of NLGN3 and CSPG4 remain in complex or only transiently interact. Altogether, our data form a critical missing link in understanding how glioma cells sense, translate and respond to neuronal activity in the TME and identify a new therapeutic target to disrupt neuron-glioma interactions.
HGG-10. THE BLOOD-BRAIN BARRIER IN DIPG: INVESTIGATING REGION-SPECIFIC DIFFERENCES IN PERMEABILITY
Authors: Ung Caitlin , Upton Dannielle , Tsoli Maria , Ziegler David 
Published: June 2021

Abstract
Diffuse Intrinsic Pontine Glioma (DIPG) is the most aggressive pediatric high-grade glioma with median survival of only 12 months from diagnosis. Current therapies are essentially palliative. The blood-brain barrier (BBB) is a major obstacle, limiting delivery of effective chemotherapeutics into the brain. We hypothesized that tumors in the brainstem region have a BBB less permeable than tumors in other brain regions. We have confirmed the presence of an intact BBB in three orthotopic models of DIPG by Evans Blue extravasation assay. Immunohistochemical staining of CD13+ pericytes and CD34+ endothelial cells in healthy mouse brain compared to orthotopic DIPG model showed higher levels of both components in brainstem compared to cortical region. Single-cell RNA sequencing experiments are currently being undertaken to investigate region-specific differences in BBB cell populations and the impact of DIPG on signaling pathways that govern permeability. To determine if tumor location impacts therapeutic outcome, we performed in vivo efficacy studies with DIPG orthotopically injected into cortical region or brainstem region and treated with SAHA, HDAC inhibitor, or temsirolimus, mTOR inhibitor. Temsirolimus or SAHA was ineffective at extending survival in mice injected with DIPG in the brainstem compared to control. However, temsirolimus led to a significant improvement in survival in mice injected with DIPG cells in cortical region (median survival 85 days) compared to control (median survival 69 days (P≤0.01)). This suggests that the same tumor in cortical region may respond to systemic therapy that is ineffective in the brainstem and that the intact BBB in the brainstem is a major reason for treatment failure in DIPG. In conclusion, the BBB in the brainstem and in the presence of DIPG may be altered, changing signaling pathways that affect permeability. Understanding the brainstem cerebrovasculature may potentially lead to a novel strategy to treat DIPG as well as other brain tumors.
HGG-16. DISSECTING THE EFFECT OF ATM DELETION ON RADIOSENSITIVITY IN DIFFUSE MIDLINE GLIOMAS WITH H3K27M MUTATION
Authors: Guerra Garcia Maria , Deland Katherine , Luo Lixia , Ma Yan , Williams Nerissa , Stewart Connor , Kirsch David , Reitman Zachary 
Published: June 2021

Abstract
Diffuse midline gliomas (DMGs) are responsible for a large proportion of childhood brain tumor deaths. Currently, radiation therapy is thought to be one of the most effective treatment options, but more than 90% of children still die within 2 years of diagnosis. DMGs are defined by somatic histone 3 K27M (H3K27M) mutations that have been shown to promote the G0/G1 to S cell cycle transition. The majority of DMGs also contain loss-of-function mutations in TP53. Prior research demonstrated that orthotopic xenograft and primary mouse models of non-H3K27M-mutated gliomas with inactivation of p53 are preferentially radiosensitized by inactivation of Ataxia Telangiectasia Mutated (ATM), a kinase that mediates DNA repair in response to DNA damage caused by radiation. The high frequency of mutations that deregulate p53 in DMGs raises the possibility that H3K27M-mutant DMGs may also be radiosensitized by ATM inhibition, representing a unique therapeutic opportunity. Here, we hypothesize that H3K27M-mutant DMGs that have loss of function of p53 will be radiosensitized by loss of ATM. To test this hypothesis, we used the RCAS-TVA viral gene delivery system to generate genetically-faithful primary mouse models of H3K27M-mutant DMG with p53 deletion, and we used Cre recombinase to delete Atm in the tumor cells of these mice and generated littermate controls that retained Atm. Mice were imaged weekly via luciferase-based bioluminescence to track tumor development and irradiated with three daily fractions of 10 Gy after tumor detection. We subsequently quantified the survival of mice without neurological decline following irradiation. In separate cohorts, we collected primary tumors after irradiation to verify H3K27M expression and to assess cell cycle arrest and mechanisms of cell death. These studies will elucidate mechanisms by which ATM inactivation can radiosensitize H3K27M-mutant DMGs with nonfunctioning p53, which will guide the design of clinical trials testing ATM inhibitors in DMG patients.
HGG-25. PRMT5 PROMOTES TUMOR GROWTH BY MAINTAINING STEMNESS OF PEDIATRIC HIGH-GRADE GLIOMA CELLS
Authors: DeSisto John , Knox Aaron , Chatwin Hannah , Balakrishnan Ilango , Venkataraman Sujatha , Vibhakar Rajeev , Green Adam 
Published: June 2021

Abstract

Background
Pediatric high-grade gliomas (pHGG) are aggressive tumors that together constitute the most common cause of childhood cancer mortality. Tumor stem cells that drive proliferation of pHGG resist chemotherapy and radiation, complicating treatment. The arginine methyltransferase PRMT5 maintains self-renewal in neural stem cells through epigenetic modifications. We hypothesized that PRMT5, which we identified as a potential driver of diffuse midline glioma (DMG) through an shRNA screen, plays a similar role in pHGG.

Methods
Using lentiviral delivery of shRNA, we knocked down (KD) PRMT5 in cortical pHGG and DMG cell lines and performed phenotypic, mechanistic and self-renewal assays. We irradiated PRMT5 KD and control cells to study sensitization. We orthotopically injected mice with PRMT5 KD pHGG cells, and with DMG cells in which PRMT5 was knocked out (KO) using CRISPR-Cas.

Results
In cellular models of cortical pHGG and DMG, PRMT5 KD significantly reduced proliferation, inhibited cell cycle progression, increased apoptosis resistance, and decreased self-renewing cell frequency. A relative shift of PRMT5 from the cytoplasm to the nucleus accompanied differentiation induced by PRMT5 KD. Epigenetic changes accompanying PRMT5 KD included increased H3K27me3, a global transcription inhibitor, and decreased H3K27M expression in DMG. PRMT5 KD sensitized pHGG cells to radiation, increasing cell death 17–30%. PRMT5 KD/KO significantly increased survival in mice and decreased tumor aggressiveness and proliferation, but mice still died of tumor-related effects.

Conclusions
PRMT5 maintains self-renewal and drives proliferation in preclinical pHGG models. In cellular and in vivo models, PRMT5 KD/KO produces epigenetic changes, including increased H3K27me3 levels and diminished H3K27M, that may reduce proliferation and self-renewal. Future work includes elucidation of the mechanisms by which PRMT5 produces the observed changes. Because PRMT5 KD/KO does not eliminate tumor growth, we plan to further study combining PRMT5 KD/KO and clinical-grade small molecule PRMT5 inhibitors with radiation and chemotherapeutic agents.
HGG-35. IDENTIFICATION OF G PROTEIN-COUPLED RECEPTOR 17 (GPR17) UP-REGULATION IN PAEDIATRIC H3 K27M-MUTANT DIFFUSE MIDLINE GLIOMA AND EXAMINATION OF ITS ROLE IN DIFFUSE MIDLINE GLIOMA CELL LINES
Authors: Loveson Katie , Fillmore Helen 
Published: June 2021

Abstract
Paediatric H3 K27M-mutant diffuse midline glioma (pDMG) is an incurable, aggressive childhood brain malignancy, that arises in a region- and age-specific nature. The underlying pathophysiology suggests dysregulation of postnatal neurodevelopmental processes causing aborted cell differentiation. The cell of origin is unclear, but data suggests an oligodendrocytic lineage (OPC), supported by the over-expression of transcription factors such as Olig1 and Olig2 in 80% of DIPG cases. In-depth bioinformatics and principal component analyses (PCA) of genes involved in brain development and pDMG support reports of OPC gene dysregulation and led to the identification of the G-protein coupled receptor 17 (GPR17) and its association with pDMG. GPR17, a rhodopsin-like orphan GPCR (unknown ligand), has the typical features of the GPCR superfamily, seven transmembrane domains (TM1-TM7), eight amphipathic helices, an extracellular N-terminal domain, and an intracellular C-terminus. GPR17 has been implicated in several normal physiological and pathological processes, such as oligodendrocyte differentiation, spinal cord injury and brain injury. GPR17 mRNA and protein expression was confirmed in all pDMG cell lines tested. Using a well-characterised agonist (MDL 299,51) and antagonist (HAMI3379) to modulate GPR17 function in pDMG cell lines resulted in phenotypic and genomic changes as well as in cell growth and migration. HAMI3379, a GPR17 specific antagonist resulted in a significant reduction in GPR17 mRNA and protein expression (p&lt;0.006) and a significant reduction in migration (p&lt;0.0025). When pDMG cells were pretreated with HAMI3379 in combination with known cytotoxic agents (Bleomycin, a radiation mimic, Panobinostat or Vincristine), there was a decrease in cell viability compare to cytotoxic agent alone. There are no current effective therapies for pDMG patients and the ability of blocking GPR17 function to enhance sensitivity to standard therapies is appealing and warrants further investigation.
HGG-41. CHARACTERIZATION OF THE IMMUNE RESPONSE FOLLOWING VARIOUS RADIOTHERAPY TREATMENTS IN GLIOBLASTOMA
Authors: Cocito Carolina , Branchtein Mylene , Gongora Tatyana , Dahmane Nadia , Greenfield Jeffrey 
Published: June 2021

Abstract
Malignant gliomas represent 6.5% of all childhood brain neoplasms with a 5-years survival rate of less than 20%. Current standard of care for these tumors include radiotherapy; recent data in solid tumors indicate that adequate radiation protocols may synergize with immunotherapy strategies for better outcomes. Nonetheless, a great discrepancy between preclinical studies and clinical trials outcomes persists, the basis of which is not fully understood. One hypothesis may be due to different radiation protocols used. We used the GL261 syngeneic mouse model of glioma to test this hypothesis and characterize the immune response to radiotherapy, with either a single dose of 10Gy, a dose often used in preclinical models, or a fractionated treatment of 2Gy for five consecutive days (2Gyx5), as fractioned radiotherapy is most often used in patients. The immune content of the brain and the blood was assessed by flow cytometry in un-irradiated (control), 10Gyx1 and 2Gyx5 treated mice for three weeks after radiation. In the brain, both radiation regimens drastically reduced the number of CD45+ cells for the first two weeks after treatment. When compared to controls, 10Gyx1 but not 2Gyx5 treated mice showed a significant increase in tumor infiltrating lymphocytes (CD3+) starting from the second week following treatment. This effect persisted until three weeks post treatment. The 10Gyx1 dose was better tolerated by the resident microglia (CD45lowCD11b+) when compared to the 2Gyx5 treatment. Our data describe the dynamics through which the immune microenvironment responds to two radiation regimens over time. Our results show that 10Gyx1 is the most effective regimen to impede tumor growth and to induce lymphocyte infiltration once the system recovers from the treatment. Our work suggests that, in the GL261 model, the fractionated radiation treatment we tested may be less optimal in priming glioma cells to the immune system.
IMMU-01. THE ONCOLYTIC VIRUS DELTA-24-RGD IN COMBINATION WITH AN AGONISTIC CD40 MAB INDUCES A DURABLE AND SYNERGISTIC ANTI-TUMOR IMMUNE EFFECT IN DIPG PRECLINICAL MODELS
Authors: Labiano Sara , Laspidea Virginia , Garcia-Moure Marc , Puigdelloses Montserrat , Becher Oren J , Gomez-Manzano Candelaria , Fueyo Juan , Patiño-Garcia Ana , Alonso Marta M 
Published: June 2021

Abstract
With a 2-year survival less than 20%, Diffuse Intrinsic Pontine Glioma (DIPG) is the principal cause of pediatric death. Despite recent advances in the current treatments, the outcome for children with DIPGs remains dismal. Since the approval of T-VEC for melanoma by the FDA, oncolytic adenoviruses have emerged as a promising therapeutic strategy for brain tumors. Thus, our group launched the first world clinical trial phase I with the oncolytic adenovirus Delta-24-RGD (DNX-2401 in the clinic) for newly diagnosed DIPG (NCT03178032), which has shown safety and feasibility. Despite DNX-2401 increases the recruitment of T cells into the tumor, they usually become inactive due to the suppressive tumor microenvironment evidencing the urgent need to improve this strategy focusing on the generation of effective long-term immune responses. Therefore, we decided to combine the Delta-24-RGD with the targeting of the costimulatory molecule CD40 in two unique orthotopic immunocompetent mouse models of DIPG. The activation of the CD40 receptor, which is expressed by antigen presenting cells (APC) such as microglia, macrophages and dendritic cells, is known to increase antigen presentation and enable T-cell priming and activation. Here, we have observed that in addition to Delta-24-RGD anti-tumor effects, the stimulation of CD40 on the tumor APCs results in a remodeling of the tumor immune compartment with a more efficient T-cell tumor infiltration. Of importance, there is an increase of the survival of mice treated with the combination as compared to single treatments or non-treated mice. In addition, the combination therapy induced a complete regression of tumors in 25% of treated mice indicating the development of long-term anti-tumor immunity. We believe that these results provide a translational breakthrough in the treatment of these lethal tumors and open the door for a future innovative clinical trial.
LGG-09. SENOLYTIC AGENT NAVITOCLAX TARGETS VINBLASTINE- AND MAPK INHIBITORS-INDUCED SENESCENT TUMOUR CELLS IN PAEDIATRIC LOW GRADE GLIOMAS
Authors: Guiho Romain , Selt Florian , Stone Thomas , Jacques Thomas , Hargrave Darren , Gil Jesús , Witt Olaf , Milde Till , Barbera Juan Pedro Martinez 
Published: June 2021

Abstract
Pilocytic astrocytoma (PA, WHO grade I), the most common paediatric brain tumour, is characterized by constitutive activation of the MAPK pathway. PA tumours show a slow growth, without tendency to progress to high-grade malignancies. However, a significant group of patients for whom a total resection is not feasible require additional therapy. The typical proliferative index of a PA, measured by Ki-67 staining, is 1–2%, whereas a large part of the tumour is Ki-67 negative and expresses markers of oncogene-induced senescence (OIS) such as SA-β-Gal positivity and the cell cycle inhibitors p16INK4a (CDKN2A) and p21Cip1 (CDKN1A). Conventional treatments (i.e. chemotherapy) tend to target only proliferative cells and the effect of new molecularly targeted therapies (e.g., MAPK pathway inhibitors) on senescent cells remains unclear. Here, we discuss the opportunities to combine these therapies with new compounds targeting the senescent cells, referred to as senolytics, using three different PA models. (1) Ex vivo culture of human PA tumours (2) Two cell lines: the DKFZ-BT66 PA human cell line, carrying the oncogenic driver KIAA1549:BRAF-fusion, used as a model of OIS; and the proliferative BT40 cell line harbouring the BRAFV600E mutation; (3) In vivo xenograft model induced by orthotopic transplantation of BT40 cells. We have previously shown that OIS cells exhibit an increased sensitivity to senolytic compounds, such as navitoclax, a clinically approved BCL2/XL inhibitor, relative to proliferative controls (Buhl et al, Clin Cancer Res. 2019). Our current research demonstrates that treatments with low doses of chemotherapy (e.g., vinblastine) or MAPK inhibitors (e.g., dabrafenib or trametinib) triggers a therapy-induced senescence response in proliferative cells (e.g., abolished proliferation, SA-β-Gal positivity, SASP production), making these senescent cells sensitive to senolytic compounds, including navitoclax. Together, our research provides a strong rationale supporting the combined use of senolytics with current conventional and targeted therapies against human PA.