bluuebunny/crossref_metadata_2025_split huggingface dataset:
HGG-24. PRECLINICAL EFFICACY OF THE BRAIN PENETRANT CYCLIN-DEPENDENT KINASE INHIBITOR ZOTIRACICLIB IN PEDIATRIC DIFFUSE MIDLINE GLIOMAS
Authors: Mueller Timothy , Yadavilli Sridevi , Laternser Sandra , Cianciolo Chiara , Przystal Justyna , Bonner Erin , Biery Matt C , Vitanza Nicholas A , Grotzer Michael , Mueller Sabine , Nazarian Javad 
Published: June 2021

Abstract
Children diagnosed with diffuse midline gliomas (DMG), including diffuse intrinsic pontine glioma (DIPG), have extremely poor outcomes with a median overall survival of 9–12 months from initial diagnosis. Standard-of-care is limited to focal radiation therapy, given the paucity of effective targeted therapies for DMG. To identify effective drugs for treatment of children diagnosed with DMG, we investigated the brain-penetrating multi cyclin-dependent kinase inhibitor Zotiraciclib (ZTR/TG02). ZTR has demonstrated encouraging response rates and a benign safety profile in phase 1 trials of adults with high-grade glioma. It is thought to achieve its anti-cancer activity mainly by transcription disruption, a previously described vulnerability of DMGs, by inhibiting multiple cyclin-dependent kinases 9 and 7 (CDK9, 7). We found that ZTR robustly reduces viability of different patient derived DMG cells in a dose-dependent manner, with a median IC50 of 201 nM across eight tested cell lines (range 11–1258 nM, 72 hrs). Consistently, we observed loss of RNA polymerase II phosphorylation after 24 hours of treatment, indicating effective CDK9 inhibition at low drug concentrations and after short incubation time. This effect was followed by depletion of short-lived proteins including MYC and the anti-apoptotic factor MCL-1. Putative biomarkers of response and resistance were identified in silico using DepMap data analysis. To assess the safety profile of ZTR, we exposed our zebrafish model to various drug concentrations and found the drug to be safe at IC50 molarity. Ongoing in vitro and in vivo studies evaluating the efficacy of ZTR in combination with promising combination therapies for more effective treatment of children with DMG are also underway.
HGG-28. ONCOGENIC TYROSINE KINASE GENE FUSIONS IN SUPRATENTORIAL HIGH GRADE GLIOMAS OF YOUNG CHILDREN - COMPARISON OF RNA- AND DNA-BASED METHODS FOR THEIR RELIABLE DETECTION
Authors: Pietsch Torsten , Gielen Gerrit , Waha Andreas , Doerner Evelyn , von Bueren Andre O , Vokuhl Christian , Kristiansen Glen , Kramm Christof 
Published: June 2021

Abstract
High-grade diffuse gliomas in early childhood are characterized by a more favorable outcome compared to older children. We have shown in previous studies that these tumors are characterized by stable genomes. The occurrence of tyrosine kinase gene fusions in high-grade gliomas of infancy may represent therapeutic targets. 50 glioblastomas (GBM) with supratentorial location occurring in children younger than four years were retrieved from the archives of the Brain Tumor Reference Center, Institute of Neuropathology, Bonn University. DNA and RNA were extracted from FFPE tumor samples. Gene fusions were identified on the DNA level by FISH using break-apart probes for ALK, NTRK1, -2, -3, ROS1 and MET and Molecular Inversion Probe (MIP) methodology. On the RNA level, fusion transcripts were detected by targeted RNA sequencing as well as Nanostring assay with fusion-specific probes. 37 supratentorial GBM occurred in the first year of life, 13 GBM between one and four years. 18 cases showed fusions of ALK to different partners; all occurred in the first year of life (18/37, 48.6%). Fusions of ROS1 were found in 5, MET in 3, NTRK1, -2, -3 in 10 cases. 12 cases showed no and two cases novel fusions. The different methods led to comparable results. Only recurrent fusions with known fusion partners were detectable with fusion sequence-specific Nanostring probes and library construction for targeted RNA sequencing failed in a fraction of cases. Break-apart FISH led to reliable results on the next day, and MIP technology represented the most sensitive method for analysis of FFPE samples. Gene fusions involving the tyrosine kinase genes ALK, MET, ROS1 and NTRK1, -2, -3 occurred in 72% of glioblastomas of young children; most frequent were ALK fusions occurring in infant GBM. DNA-based MIP technology represented the most robust and sensitive assay. A combination of RNA- and DNA-based methods to detect these fusions with high reliability is recommended.
HGG-39. ALTERNATIVE SPLICING OF NEUROFIBROMIN 1 IS ASSOCIATED WITH ELEVATED MAPK ACTIVITY AND POOR PROGNOSIS IN HIGH-GRADE GLIOMA
Authors: Siddaway Robert , Milos Scott , Vadivel Arun , Dobson Tara , Swaminathan Jyothishmathi , Ryall Scott , Pajovic Sanja , Nazarian Javad , Becher Oren , Brudno Michael , Ramani Arun , Gopalakrishnan Vidya , Hawkins Cynthia 
Published: June 2021

Abstract
Despite a good understanding of the coding mutations underlying high-grade gliomas (HGG), their prognosis remains poor. We sought to characterize their transcriptional alterations and how this contributes to pathogenesis. We analyzed a large cohort of pediatric HGG (pHGG) by DNA sequencing (n=79) and RNA-Seq (n=63 plus normal brain, n=20), finding spliceosome mutations that are associated with increased splicing burden. High levels of alternative splicing were found in known cancer driver genes, with enrichment for chromatin regulators (including the SWI/SNF and NuRD complexes) and the RAS/MAPK pathway, in particular neurofibromin 1 (NF1). Both pediatric and adult HGG preferentially expressed NF1-II, a less active RAS GTPase, resulting in increased RAS/MAPK activity resulting from inclusion of exon23a into the GAP-related domain of NF1. In IDH wild-type, adult HGG, NF1-II was associated with reduced survival independently from RAS/MAPK pathway mutations. NF1 exon23a splicing was regulated by REST-mediated suppression of splicing factors controlling its inclusion. Together, our results identify a novel mechanism by which HGG can activate RAS/MAPK signaling and other oncogenic pathways to promote tumorigenesis independently from direct mutations.
HGG-40. FOCUSED ULTRASOUND ENHANCES ETOPOSIDE DELIVERY IN A MURINE PONTINE GLIOMA MODEL
Authors: Englander Zachary , Wei Hong-Jian , Pouliopoulos Antonios , Yoh Nina , McQuillan Nicholas , Tazhibi Masih , Wang Tony , Bruce Jeffrey , Canoll Peter , Feldstein Neil , Zacharoulis Stergios , Konofagou Elisa , Wu Cheng-Chia 
Published: June 2021

Abstract

Background
Diffuse intrinsic pontine glioma (DIPG) is a devastating pediatric brain cancer with limited treatment options and poor survival. The delivery of systemic therapies in this disease is severely limited by the blood-brain barrier (BBB). Focused ultrasound combined with intravenous microbubbles (FUS+MB) can effectively open the BBB permitting the entry of drugs across the cerebrovasculature. Etoposide is a chemotherapy frequently used in pediatric oncology with well-established anti-tumor effects but limited efficacy when administered systemically in DIPG. Given that FUS+MB in DIPG is not well studied, our goal was to determine the feasibility of ultrasound-mediated BBB opening and etoposide delivery in a preclinical murine pontine glioma model.

Methods
A syngeneic, orthotopic model was established by stereotactic injection of PDGF-B+PTEN-/-p53-/- murine glioma cells into the pons of B6 albino mice. Mice were randomly divided into control (n=6) or FUS+MB groups (n=6). A single-element, spherical-segment FUS transducer (center frequency=1.5MHz) driven by a function generator through a power amplifier was used with concurrent microbubble injection to sonicate the tumor and its margins on post-injection day 14. Immediately after treatment, 5 mg/kg of intraperitoneal etoposide was administered to all 12 mice. All animals underwent cardiac puncture and blood sampling, followed by transcardiac perfusion and brain harvesting. Liquid chromatography-mass spectometry was performed on both serum and tumor tissue to measure etoposide levels.

Results
Contrast-enhanced MRI demonstrated successful BBB opening in all FUS+MB mice. Compared to control (mean=20.98ng/g), etoposide concentration in the sonicated tumor tissue (mean=164.77ng/g) was nearly eight times greater. Lastly, the mean brain tumor–to-serum ratio was more than fivefold higher in the treated mice (1.50%) compared with the control mice (0.28%) (P&lt;0.005).

Conclusions
FUS+MB is hereby shown successful in BBB opening and enhanced delivery of etoposide in a preclinical pontine glioma model.
IMMU-06. DELTA-24-RGD EXPRESSING POSITIVE IMMUNE MODULATORS SHOW ANTI-DIPG EFFECT AND INCREASE TUMOR IMMUNE INFILTRATION
Authors: Laspidea Virginia , Gupta Sumit , Puigdelloses Montserrat , Labiano Sara , Ausejo-Mauleon Iker , de la Nava Daniel , Becher Oren J , Gumin Joy , Fueyo Juan , Gomez-Manzano Candelaria , Alonso Marta M 
Published: June 2021

Abstract
Diffuse Intrinsic Pontine Gliomas (DIPG) are aggressive pediatric brain tumors that arise in the pons of children, being the leading cause of pediatric death caused by cancer. We have previously demonstrated that Delta-24-RGD administration is safe and efficacious in DIPG preclinical models, indicating that it could be a good candidate as therapeutic approach for DIPG. However, our data underscore that there is still room to improve the anti-DIPG effect obtained with Delta-24-RGD. For that purpose, we have constructed three new virus by engineering Delta-24-RGD with different T cell activators: 4-1BBL (Delta-24-ACT), OX40-L (Delta-24-RGDOX) and GITRL (Delta-24-GREAT), to further increase the immune response generated by the viral effect. In vitro, the three virus were able to infect murine and human DIPG cell lines, produce oncolytic effect in a dose-dependent manner and express the corresponding functional ligand (4-1BBL, OX40L or GITRL) in the membrane of infected cells (almost 100% of cells expressing them at 10 MOIs). As expected, viral replication was optimal in human cell lines but semipermissive in murine cells. In vivo, the intratumoral administration of armed oncolytic viruses was safe and significantly increased survival of mice bearing orthotopic DIPG murine tumors, leading to long-term survivors. In addition, we analyzed the effect of the virus in the tumor microenvironment by flow cytometry and immunohistochemistry, which indicated that there was a significant increase of immune infiltration in brains of treated mice. Moreover, the immune infiltrated showed a functional active phenotype. Although deeper characterization is needed, these data show that the incorporation of a positive immune modulator into Delta-24-RGD could improve the oncolytic effect of the virus by boosting the immune response, while maintaining a safe profile in immunocompetent models offering a feasible option treatment for DIPG.
IMMU-07. “STROKE MIMICS” ARE NOT BENIGN IN IMMUNOCOMPROMISED CHILDREN
Authors: Mahdi Jasia , Bach Alicia , Smith Alyssa , Tomko Stuart , Fields Melanie , Griffith Jennifer , Morris Stephanie , Guerriero Rejean , Noetzel Michael , Guilliams Kristin , Agner Shannon 
Published: June 2021

Abstract

Objective
To determine the clinical variances between strokes and stroke mimics in a pediatric immunocompromised population that consists of children with central nervous system (CNS) and non-CNS malignancies and a history of solid organ transplantation.

Methods
We performed a retrospective cohort analysis of stroke alert activations in patients with high-grade gliomas, low-grade gliomas, atypical teratoid rhabdoid tumors, rare CNS tumors, B-cell acute lymphoblastic leukemia, T-cell acute lymphoblastic leukemia, osteosarcoma, and solid organ transplants at St. Louis Children’s Hospital between February 2013 and September 2019. We categorized final diagnoses as strokes or stroke mimics. We classified diagnoses as a neurologic emergency if the diagnosis necessitated changes in management.

Results
Out of 217 stroke alerts, 31 alerts occurred for 28 patients meeting inclusion criteria. All final diagnoses constituted neurologic emergencies, including: stroke (39%), chemotherapy-related neurotoxicity (29%), tumor progression (19%), and seizures/posterior reversible encephalopathy syndrome (13%). Patients meeting inclusion criteria with strokes and stroke mimics presented similarly, with the exception of altered mental status, which was more prevalent in patients with strokes than stroke mimics (p = 0.03). One child received hyperacute thrombectomy for stroke. Only 58% of children with stroke mimics had complete resolution of their presenting neurologic symptoms. Children with strokes and stroke mimics had similar mortality incidences of 33% and 37%, respectively.

Conclusions
Although all acute neurologic changes in immunocompromised children are not strokes, stroke mimics in this population are neither benign nor self-limited and carry long-term neurologic morbidity and mortality. This study highlights the utility of an acute stroke evaluation infrastructure and the need for acute and long-term neurology involvement in the care of these patients.
IMMU-10. USE OF A SINGLE PEPTIDE CHECKPOINT INHIBITOR FOR TREATMENT OF CENTRAL NERVOUS SYSTEM TUMORS
Authors: Moertel Christopher , Xiong Zhengming , Pluhar G-Elisabeth , Olin Michael 
Published: June 2021

Abstract
Cancer immunotherapy has revolutionized clinical management of malignancies by generating long-term, durable control of tumors. Unfortunately, these therapies often cause serious immune-related adverse events. In addition, only a small percentage of solid tumors respond to these therapies and there is little efficacy in CNS tumors. Our research is focused on the CD200 immune checkpoint, which modulates the immune system through the inhibitory receptor (CD200R1) and activation receptors (CD200AR). We demonstrated that targeting the CD200AR with a checkpoint peptide ligand (CD200AR-L) activates the immune system and renders it impervious to the inhibitory effects of CD200. In a pre-clinical canine spontaneous high-grade glioma trial, CD200AR-L, with autologous tumor lysate vaccination, resulted in a 20% two-year progression-free survival; no toxicities or adverse effects were observed. We suggest this result was due to the ability of the CD200AR-L to modulate multiple immune checkpoints. During the characterization of the CD200AR-L, we discovered signaling molecules are shared by the CD200 and PD-1/PD-L1 checkpoint pathways, suggesting these immune checkpoints are connected. Our preliminary studies demonstrated that the inhibitory CD200R1 and PD-1 mediate immune checkpoint signaling activities through the SHIP1/2. Moreover, CD200AR-L overpowers the suppressive effects of CD200 and PD-L1, which are both shed by tumors, by downregulating the inhibitory CD200R1 and PD-1 on both antigen-presenting cells (APC) and T-cells. In addition, CD200AR-L downregulates PD-1 on APCs and inhibits the upregulation of PD-L1 and CTLA4. These studies led to the discovery that the novel peptide modulates the CD200, PD-1/PD-L1 and CTLA-4 pathways, providing the basis for the translatable development of a CD200-directed peptide for clinical use against multiple tumors including gliomas. These studies led to FDA approval of this peptide for the first in human phase I single center, open-label, dose-escalation clinical trial (NCT04642937) in adult and pediatric trial for children with recurrent malignant brain tumors.
IMMU-13. CUSTOMIZABLE MULTI-LAMELLAR RNA-NANOPARTICLES FOR PEDIATRIC GLIOMA
Authors: Mendez-Gomez Hector , McGuiness James , grippin Adam , Weidert Frances , Carrera-Justiz Sheila , Mitchell Duane , Sayour Elias 
Published: June 2021

Abstract

Background
Since the preponderance of pediatric gliomas are mutationally ‘bland,’ immune checkpoint inhibitors are unlikely to mediate therapeutic benefit. Alternately, immunologic response can be induced de novo against pediatric gliomas with mRNA cancer vaccines. Messenger RNA represents a paradigm shift in vaccinology (i.e. COVID-19) given its flexibility, commercialization, and propensity to confer rapid protection with only a single vaccine.

Objective
We sought to develop a new mRNA platform with an optimized backbone for insertion of both personalized and/or “off the shelf’ (i.e. H3K27M) transcripts for rapid induction of anti-tumor activity against pediatric gliomas.

Approach
We synthesized an mRNA backbone with optimized 5’ and 3’ UTRs for delivery of gene transcripts pertinent to pediatric brain tumors using a lipid-nanoparticle (NP) delivery vehicle. This vaccine utilizes a novel engineering design that layers tumor derived mRNA into a lipid-nanoparticle (NP) “onion-like” or multi-lamellar package.

Results
We demonstrate immunogenicity of RNA-NPs delivering either personalized glioma mRNA or H3K27M mRNA. RNA-NPs localize to myeloid cells in murine KR158b brain tumors and activate dendritic cells that supplant regulatory intratumoral myeloid populations inducing antigen-recall response with long-term survivor benefit. Our optimized mRNA backbone yielded significantly improved anti-tumor efficacy compared with commercial backbones. We have shown this approach can be refined for co-delivery of immunomodulatory RNAs (i.e. GM-CSF) and/or delivery of siRNAs targeting immunoregulatory axes (PD-L1) in murine brain tumors (GL261). We have since established safety of RNA-NPs in acute/chronic murine GLP toxicity studies without cross-reactivity to normal-brain, and launched a large-animal canine brain tumor trial which demonstrated RNA-NPs to be feasible, safe and immunologically active.

Conclusion
RNA-NPs reprogram the brain tumor microenvironment while inducing a glioma-specific immune response. We have since received FDA-IND approval for first-in-human trials (IND#BB-19304) in pediatric patients with high-grade gliomas (PNOC020 study, NCT04573140).
LGG-04. MULTIOMIC ANALYSIS OF MAPK PATHWAY ACTIVITY IN PEDIATRIC PILOCYTIC ASTROCYTOMA
Authors: Sigaud Romain , Selt Florian , Hielscher Thomas , Stefanski Anja , Overbeck Nina , Usta Diren , Kocher Daniela , Remke Marc , Picard Daniel , Pfister Stefan M , Jones David T W , Brummer Tilman , Witt Olaf , Milde Till 
Published: June 2021

Abstract

Introduction
Pilocytic astrocytomas (PA) are the most common pediatric brain tumors. They are characterized by MAPK pathway alterations, leading to its constitutive activation and modulating the balance between cell proliferation and the oncogene-induced senescence (OIS) sustained by senescence-associated secretory phenotype (SASP) factors. This makes PA suitable for MAPK inhibitor (MAPKi) therapies, showing encouraging results in phase 1/2 clinical trials. Little is known about the molecular implications of MAPK downregulation in the proliferating and senescent compartments.

Methods
DKFZ-BT66 PA cells derived from a primary KIAA:BRAF-fusion positive PA cell line, were used as model system. Gene expression and phospho-proteomic datasets were generated from DKFZ-BT66 cells, in both the proliferative and senescent states, and treated with the MEKi trametinib for different time-spans. A time course analysis based on differentially expressed genes was performed, followed by a single-sample gene set enrichment analysis (ssGSEA). Analysis of the phospho-proteomic data is ongoing.

Results
Differential gene expression analysis revealed that MEK inhibition leads to the inhibition of the OIS-SASP gene program in senescent DKFZ-BT66. ssGSEA showed that most MAPK-related signatures were downregulated upon MEKi treatment, while pathways related to upstream MAPK activators (including FGFR, NTRK and TGFB pathways) were upregulated, in both proliferating and senescent DKFZ-BT66. Genes regulated by the MAPK pathway and involved in OIS-SASP were identified by analyzing genes differentially regulated between proliferating and senescent DKFZ-BT66, and modulated upon MEKi treatment.

Conclusion
This data suggests that MAPKi reverses OIS in senescent PA cells, while inducing the activation of MAPK upstream regulators in proliferating and senescent PA cells, identifying putative co-targets that could help prevent growth rebound upon MAPKi withdrawal. Furthermore, the identification of the MAPK-related OIS-SASP genes provide insight about the regulation of OIS-SASP by the MAPK pathway. Validation of this data with the ongoing phospho-proteomic analysis and in primary samples is needed.
LGG-08. TREATMENT OUTCOMES AND TOLERABILITY OF TRAMETINIB IN PROGRESSIVE CIRCUMSCRIBED LOW-GRADE GLIOMAS
Authors: Hanzlik Emily , Archambault Bridget , Dairi Mays , Schroeder Kristin , Patel Mallika , Lipp Eric S , Boucree Song , Peters Katherine , Ashley David , Landi Daniel 
Published: June 2021

Abstract
Circumscribed low-grade gliomas comprise roughly one-third of pediatric CNS tumors. Most of these tumors are caused by activating mutations in the mitogen-activated protein kinase (MAPK) pathway. Drugs targeting the MAPK pathway are effective in other cancers and are being utilized in low-grade gliomas. We describe treatment outcomes and toxicities in a series of thirteen low-grade glioma patients treated with trametinib. We performed a retrospective chart review to evaluate response on T2/FLAIR MRI images per updated RANO criteria, visual outcomes, tolerability, and durability of response in progressive low-grade glioma patients treated with trametinib. Thirteen patients age 22 months to 34 years were included. Best radiographic response on therapy included 2/13 partial response, 3/13 minimal response, 5/13 stable disease, and 3/13 progressive disease. Diagnoses included pilocytic astrocytoma (n=6), desmoplastic infantile ganglioglioma (DIG; n=1), and low-grade glial neoplasms (n=2). Molecular drivers included BRAF:KIAA1549 fusion (n=3), V600E mutation (n=1), and somatic NF1 mutation (n=1). Three patients had germline NF1. In patients with partial or minimal response, best response was seen after longer durations of therapy; 4 of 5 best responses occurred after at least 12 months on therapy. Five patients completed prescribed therapy. Three patients remain stable off therapy at 6, 12, and 21 months; two patients recurred at 1 and 10 months off therapy. Skin manifestations were the predominant form of toxicity. This was more severe in older males, and symptoms improved with intermittent dosing. All patients with optic pathway tumors showed at least stable vision throughout treatment, with some patients having dramatic improvement. Trametinib is effective and well-tolerated in patients with low-grade glioma. Dermatologic toxicity can be mitigated by intermittent dosing. Best responses tended to occur later in therapy, sometimes after relatively stable MRIs. Patients with optic pathway lesions showed stable to improved vision even in the absence of significant radiographic response.