bluuebunny/crossref_metadata_2025 huggingface dataset:
METB-08. GENOMIC AND MOLECULAR PROFILING OF PEDIATRIC CENTRAL NERVOUS SYSTEM TUMORS: A SINGLE INSTITUTION ANALYSIS
Authors: Kline Cassie , Lin Fumin , Liou Angela , Kraya Adam , Cole Kristina , Fisher Michael , Li Marilyn
Published: June 2023

BACKGROUND

Molecular characterization has revolutionized management of pediatric central nervous system (CNS) tumors, with genomic sequencing for diagnosis and determination of actionable variants now largely considered standard of care. We report a single institution’s experience performing genomic sequencing for pediatric CNS tumors over nearly five years.

METHODS

Nucleic acid isolated from tumor tissue and paired normal specimens from patients at Children’s Hospital of Philadelphia (CHOP) undergoes paired next generation sequencing (NGS) and copy number analyses of 237 cancer genes and a fusion panel of more than 700 exons of 117 cancer genes (tumor only). All variants are tiered 1-4 according to known clinical significance. Descriptive statistics summarize clinical and molecular data and ensemble-based methods will be used to correlate molecular and clinical characteristics.

RESULTS

Between January 1, 2016 and June 30, 2020, 497 patients ≤ 21 years old with median age of 9.5 years (n=243 females; 49%) contributed to 539 cases across 25 CNS tumor subtypes. The most common diagnoses were pilocytic astrocytoma (n=118), medulloblastoma (n=49), and diffuse midline glioma (DMG; n=39). Clinically significant variants (tier 1,2) were detected in 91% of the patients. Most tumors demonstrated tier 1,2 single nucleotide variants (SNV)/insertions/deletions (n=263, 53%), most commonly in TP53>BRAF>H3F3A, and/or CNVs (n=310, 62%), most commonly gains of 7q>7p>1q. Thirty percent of tumors demonstrated tier 1,2 fusions (n=149), most commonly involving BRAF, NTRK2, or FGFR. Average tumor mutation burden in patients without germline predispositions was 3.5/Mbp (standard deviation 3.8). Germline/presumed germline pathogenic variants were found in 18% (90/497) of patients tested with most common germline alterations in TP53 followed by NF1 and APC.

CONCLUSION

A large, single site cohort of molecularly characterized CNS tumors demonstrate the clinical and biologic utility of real-time, institution-based genomic sequencing. Molecular findings in correlation with clinical characteristics and outcomes are underway.
METB-11. EXPANSION OF THE PEDIATRIC BRAIN TUMOR ATLAS: AN OPEN SCIENCE EFFORT OF CHILDREN’S BRAIN TUMOR NETWORK, KIDS FIRST DATA RESOURCE AND CHILDHOOD CANCER DATA INITIATIVE
Authors: Koptyra Mateusz , Farrow Bailey , Sullivan Catherine , Coleman Noel , Rathi Komal , Van Kuren Nicholas , Zhu Yuankun , Heath Allison , McGrory Stephanie , Kraya Adam , Guo Yiran , Brown Miguel , Huang Xiaoyan , Kim Meen Chul , Zhang Bo , Ennis Brian , Rokita Jo Lynne , Friedman Christopher , Mason Jennifer , Lilly Jena , Cuellar Ximena , Duros Trang , Nguyen Thinh , Drake Emmett , Helili Zeinab , Frenkel Beth , Trooskin Gerri , Familiar Ariana , Viswanathan Karthik , Beck Christopher , Hollawell Madison , Baubet Valerie , Madsen Peter , Kline Cassie , Patton Tatiana , Arya Kamnaa , Cardona Dani , Velasco Ryan , Santi Mariarita , Storm Phillip B , Resnick Adam C ,   Children’s Brain Tumor Network
Published: June 2023

Pediatric central nervous system cancers are the leading disease-related cause of death in children and there is urgent need for curative therapeutic strategies for these tumors. To address the urgency, Children’s Brain Tumor Network (CBTN) has advanced an open science model to accelerate the research discovery for pediatric brain tumors. In first phase of Open Pediatric Brain Tumor Atlas (OpenPBTA) effort CBTN together with Pacific Pediatric Neuro-Oncology Consortium (PNOC) and Gabriella Miller Kids First Data Resource Center (KFDRC) created and characterized over 1000 clinically annotated pediatric brain tumors.

The second phase of the OpenPBTA, through resource awards and collaboration across KFDRC, the NCI Childhood Cancer Data Initiative (CCDI), Clinical Proteomic Tumor Analysis Consortium (CPTAC), Center for Cancer Research and partnered institutions and foundations has expanded molecular characterization for an additional 1900 pediatric brain tumor patients and their families. This includes the processing and characterization of >8000 specimens across >50 brain tumor diagnoses. This expansion builds off multimodal data including whole genome, RNA, miRNA and methylation sequencing, proteomics, lipidomics and/or metabolomics. Molecular data is linked to longitudinal clinical data, imaging data, histology images, and pathology reports.

The data deposition in the cloud-based environment of the NCI’s CCDI and KFDRC to provide near real-time integration, dissemination, processing, and sharing capability. The approach leverages the DRC platform’s cloud-based computational environment through CAVATICA portal shareable pipelines. Data can be explored via PedcBioPortal, a data visualization/analysis application integrating additional public and deposited datasets.

This OpenPBTA expansion released with no embargo provides one of the largest deeply characterized cohorts of samples and associated clinical data for >3000 pediatric brain tumor patients. CBTN’s open-science, rapid-release model aims to accelerate pediatric biomarker and drug discovery research and supports clinical trial development on behalf of changing the outcome for kids with brain tumors.
HGG-02. METABOLIC TARGETING OF HIGH-GRADE GLIOMAS WITH MTAP LOSS
Authors: Subramaniam Bavani , Kritzer Bettina , Putnam Ethan , Cunningham Gary , Bhattacharya Surajit , Packer Roger , Bornhorst Miriam , Nazarian Javad
Published: June 2023

Malignant transformation of pediatric glioma is often associated with homozygous deletion of CDKN2A. With CDKN2A loss, MTAP which is in the same chromosomal location, 9p21, is homozygously deleted in a majority of HGGs and some LGGs. The MTAP gene codes for methylthioadenosine phosphorylase (MTAP) protein which plays an important role in methionine salvage pathway. Absence of MTAP results in accumulation of 5’-methylthioadenosine (MTA), de novo purine synthesis, and tumor cell dependency on protein arginine methyltransferase 5 (PRMT5) and its substrate provider, methionine adenosyltransferase II alpha (MAT2A). We hypothesize that drugs targeting PRMT5, MAT2A, and de novo purine synthesis, in combination with drugs targeting hyper-activated RAS/MAPK pathway, will be effective in inhibiting MTAP-null glioma growth. Patient-derived glioma cells were validated for MTAP loss using genome sequencing, RNA sequencing and western blot. MTA accumulation caused by MTAP loss was validated through high-performance liquid chromatography. Cells were subjected to monotherapy and combination drug therapy with PRMT5, MAT2A and de novo purine synthesis inhibitors, in addition to drugs targeting RAS/MAPK signaling pathway. Additionally, MTAP-null (MTAPnull) in vivo models are being developed.We show accumulation of MTA in MTAPnull cells compared to MTAP-wild type (MTAPWT) cells, caused by loss of MTAP that cleaves MTA to adenine and 5-methylthioribose-1-phosphate (MTR). Accumulation of MTA makes MTAPnull glioma cells more sensitive to MAT2A inhibitor AG-270 in comparison to MTAPWT cells. Additionally, dual-drug therapies involving MTA and AG-270 result in additive effect on MTAPnull cells and antagonistic effect on MTAPWT cells. De novo purine synthesis inhibitor and drugs targeting the RAS/MAPK pathways also exhibited cell growth inhibition of MTAPnull cells. Overall, metabolic targeting of HGGs bearing CDKN2A/MTAP loss is indispensable for targeted therapy and for minimizing toxicity towards surrounding normal cells lacking similar mutations.
HGG-04. INFANTILE HIGH GRADE GLIOMA: HONG KONG EXPERIENCE
Authors: Ning Lau Sarah Sau , Ku Dennis Tak Loi , Liu Pak Yin Anthony
Published: June 2023

OBJECTIVE

To review local infantile high-grade glioma (IHG) patients and their outcome.

BACKGROUND

Infantile high-grade glioma is diagnosed in patients less than 12 months of age. Studies have shown that it displays a more stable genome, and are usually single mutation driven. The most identifiable mutations are receptor tyrosine kinase (RTK) fusion, such as NTRK family, ROS1, ALK and MET. The current principal treatment remains to be surgery, but it is challenging for a complete resection due to hemispheric involvement. Chemotherapeutic drugs for IHG are still under debate, with targeted therapy showing efficacy in promoting tumour shrinkage. Despite being a challenging CNS tumour, the overall survival of IHG is superior to other paediatric high-grade gliomas. Result: We identified 7 IHG patients in our local data. Mean age of diagnosis was 3 months. There were 4 males and 3 females. Six patients had histological diagnosis of glioblastoma and 1 patient had diagnosis of anaplastic astrocytoma. One patient had her tumour located in infratentorial region. Three patients had multilobar involvement. NTRK fusion was found in 4 patients (NTRK fusion, ETV6-NTRK3 fusion and TPR-NTRK1 fusion). ALK fusion was found in 1 patient (HMBOX1-ALK). All patients underwent chemotherapy, with four patients switched to NTRK inhibitor afterwards. Surgery was performed at various time points for these patients. One patient passed away at 22 months of age at submission of this abstract.

CONCLUSION

A local review gives us more insight into the updated diagnosis, management and outcome of infantile patients diagnosed with high-grade glioma. Infantile high-grade glioma should be regarded as a unique tumour entity and a multidisciplinary approach is paramount in improving survival for this group of patients.
HGG-06. CHARACTERIZATION OF THE EFFECT OF THE ORAL IRON-MIMETIC GALLIUM MALTOLATE ON PEDIATRIC GLIOBLASTOMA GROWTH IN VIVO
Authors: Al-Gizawiy Mona M , Wujek Robert T , Zoss Casey J , Tanaka Ryuma , Mirza Shama P , Chitambar Christopher R , Schmainda Kathleen M
Published: June 2023

BACKGROUND

Glioblastoma (GBM) is a highly aggressive CNS tumor that is associated with poor outcome. This dire prognosis is due in part to its poor response to the limited treatment options available. Iron and iron proteins play a key role in the growth of brain tumors, with our published studies showing that the ferrobiology of adult GBM can be exploited for therapeutic purposes. Here, we further elucidate the inhibitory effects of oral gallium maltolate (GaM) in pediatric GBM in vivo.

METHODS

Pediatric SJ-GBM2 cells were stereotactically implanted into the right striatum of male athymic rats. Advanced MR imaging at 9.4T was carried out weekly starting two weeks after implantation. Daily oral GaM (50mg/kg) or vehicle were provided on tumor confirmation. Longitudinal advanced MRI parameters were processed for enhancing tumor ROIs in OsiriX 8.5.1 (lite) with Imaging Biometrics Software (Imaging Biometrics LLC). Statistical analyses included Kaplan-Meier survival plots, linear mixed model comparisons, and t-statistic for slopes comparison.

RESULTS

The sensitivity of the in vivo pediatric GBM xenografts to GaM was consistent with our previous in vitro work. Median overall survival was 21 days in the controls and 49 days in the treatment group (p=0.014). GaM-treated xenograft tumors grew significantly slower than control tumors (p=0.031). Histologically, xenograft tumors recapitulated the aggressive growth features of clinical specimens, such as invasive margins. Unlike adult GBM xenografts in our previous studies, pediatric GBM xenografts did not exhibit vessel normalization or a reduction in pro-angiogenic markers in response to GaM. Additionally, MIB-1% (p=0.6583) and mitotic index (p=0.7097) were not affected by treatment. Yet, transferrin receptor and H-ferritin expression patterns in GaM-treated tumors suggested cellular iron deprivation.

CONCLUSION

Monotherapy with GaM provides a significant survival benefit in pediatric GBM, and further studies are planned to optimize the benefit of GaM in pediatric GBM.
IMG-01. LONGITUDINAL FMRI OF VISUAL, AUDITORY AND MOTOR FUNCTION IN PEDIATRIC CRANIOPHARYNGIOMA AFTER TREATMENT WITH PROTON RADIOTHERAPY
Authors: Zou Ping , Hua ChiaHo , Uh Jinsoo , Conklin Heather , Merchant Thomas , Sitaram Ranganatha
Published: June 2023

INTRODUCTION

Craniopharyngioma accounts for approximately 4% of childhood central nervous system tumors and has a 5-year overall survival rate exceeding 90%. Survivors of childhood craniopharyngioma may experience neurologic sequalae, including visual and fine motor deficits, and subclinical hearing loss associated with tumor and treatment. Contemporary treatment includes radical surgery or more limited surgery and proton radiotherapy (PRT). Here we report on a longitudinal fMRI study probing visual, auditory, and motor function in pediatric craniopharyngioma patients. METHOD: The study (NCT01419067) was IRB approved and informed consent was obtained for each patient. Functional MR images were acquired at 4 time points: after surgery and before PRT (TP1), and 18-months (TP2), 36-months (TP3), and 60-months (TP4) after PRT. Data from a sensory survey fMRI task (visual: flashing checkerboard; auditory: dissonant ascending/descending pure tones; and sensory/motor: button pushing when stimuli were on) for 67 patients were analyzed at the 4 time points. The median age was 11.7 years (range 8.3-20.2 years) and the female/male ratio was 37/30.

RESULTS

Significant brain activation was seen in visual cortices, auditory cortices, and supplementary motor area (SMA) and motor cortices for all 4 time points. Over the time, visual and motor cortices showed minimum changes in activation; however, there was a small increase in SMA. For the auditory cortices, the activation volume in Heschl’s gyri increased bilaterally, and the lateralization index decreased (TP1: 70%; TP2: 46%; TP3: 39%; and TP4: 26%) due to larger increases in the right Heschl’s gyrus.

CONCLUSION

Increasing activation in Heschl’s gyri, especially on the right side, after PRT suggests decreasing efficiency in distinguishing tones in these patients. These findings may be associated with late effects involving the specific gyri or neuropathways affected by surgery or irradiation.
IMMU-02. CMV-EXPANDED T-CELLS IN GLIOBLASTOMA PATIENTS: TRANSLATIONAL RESEARCH
Authors: Kampers Linde F C , Rajabpour Golnaz , Bitar Michael , Schirrmacher Volker , Stücker Wilfried , Van Gool Stefaan W
Published: June 2023

Human cytomegalovirus (CMV) is a contributing factor to tumour expansion and progression in glioblastoma patients. Patient-derived non-modified CMV-specific T cells can be isolated, ex vivo re-stimulated with CMV and expanded before IV infusion. Adoptive T cell Therapy with expanded CMV-specific T cells and has been shown to improve GBM prognosis. We aimed to develop a CMV-specific T cell expansion protocol. PBMCs were isolated from blood of 12 healthy CMV-antibody positive donors and 9 patients (three glioblastoma patients, four prostate cancer patients, one pancreatic cancer and one rectal cancer patient). CMV-pulsed stimulating and responding PBMC (S:R ratio = 1:2) were cultured in RPMI supplemented with IL-21 and subsequent IL-2 addition for 9 days. Cell quality was ensured via cell surface staining and intracellular cytokine assays. Product sterility was tested with aerobic and anaerobic sterility assays, Endotoxin test and mycoplasma tests. Autologous CMV-specific T cells were successfully isolated from CMV positive donors and cancer patients. Ex vivo analysis of CMV-specific T cells after in vitro CMV restimulation and expansion resulted in 6.81 x 106 to 2.52 x 108 viable cells (Δ1.09 x 108 with Δ90% viability) with antigen-specific active T-cell frequencies ranging from 15.10% to 41.98% (median 38.39%) in healthy donors and 14.78% to 54.75% of total CD8+ T cells (median 31.42%) in cancer patients. A cell culture protocol was developed to expand autologous CMV-specific CD8+ T cells from patients. Product release criteria were defined as 1-2 x 107 cells per m2 body surface area with a >50% viability rate and >15% CMV-specific CD8+ T cells within the total T cell population. The translation of the cell culture protocol within a GMP setting is envisioned. The efficacy of such treatment has to be elaborated once the cell product is approved for medicinal use.
IMMU-03. IDENTIFICATION OF GENETIC BIOMARKERS TO PREDICT RESPONSE TO HSV-1 G207 AND POLIO:RHINOVIRUS IMMUNOTHERAPY
Authors: Thompson Eric , Kang Kyung-Don , Zhang Hengshan , Brown Michael , Stevenson Kevin , Friedman Gregory
Published: June 2023

BACKGROUND

The polio:rhinovirus chimera, PVSRIPO, and the herpes simplex virus, G207, are viral immunotherapies with promising results in Phase I trials of pediatric high-grade glioma (pHGG) and medulloblastoma. While some patients have durable responses, others have no benefit. The purpose of this study is to identify genes that putatively confer resistance to viral immunotherapy.

METHODS

A panel of medulloblastoma and pHGG cell lines were treated with either PVSRIPO or G207 and categorized into “sensitive” and “resistant” groups based viability. Flow cytometry was used to quantify cell receptor expression (CD111 for G207, CD155 for PVSRIPO). RNA sequencing was completed on treated resistant and sensitive cells.

RESULTS

D341 and D556 medulloblastoma had < 50% viability at 72h (G207) and 24h (PVSRIPO) and were categorized as sensitive; D283 and D324 were categorized as resistant. There was a correlation between CD111 expression and cell viability (Spearman r=0.71) but no correlation between CD155 and viability. The number of significantly differentially expressed (DE) genes (adjusted p≤0.05) was significantly higher in sensitive compared to resistant medulloblastoma, both for enriched (mean 666.4±614 vs. 454.6±377.4, P=0.0422) and depleted (826.9±645.5 vs. 449±367.8, P=0.0167) genes after treatment. There were few shared DE genes between cells treated with PVSRIPO and G207: GCLM, LANCL2, and RBM3 were enriched while ADAMTS1 and VEGFA were depleted. Likewise, there were few shared DE genes enriched between medulloblastoma and pHGG cell lines treated with G207: GPSM2, CHECK2, SEPTIN2, EIF4G2, GCLM, GDAP1, LANCL2, and PWP1.

CONCLUSIONS

Genetic analysis demonstrates minimal overlap in DE genes between the two viral immunotherapies. PVRIPO and G207 infection resulted in significantly more DE gene expression in sensitive vs. resistant cells. GCLM and LANCL2 are enriched by both PVSRIPO and G207 and in medulloblastoma and pHGG. These genes may serve as potential biomarkers in predicting response to viral immunotherapy.
IMMU-13. PRECLINICAL EFFICACY OF MULTI-ANTIGEN (HER2/EGFR806/B7-H3/IL13RA2) TARGETING QUAD-CAR T CELLS AGAINST DIFFUSE MIDLINE GLIOMA
Authors: Myers Carrie , Timpanaro Andrea , Song Edward , Meechan Michael , Chen Alex , Biery Matthew , Reid Aquene , Gwiazda Kamila , Baldwin Michael , Gustafson Joshua , Gardner Rebecca , Jensen Michael , Vitanza Nicholas
Published: June 2023

BACKGROUND

Diffuse midline glioma (DMG), including diffuse intrinsic pontine glioma (DIPG), remains a fatal disease. We have published the preclinical efficacy of HER2, EGFR806, and B7-H3 CAR-T cells and opened 3 trials (BrainChild-01, -02, and -03, respectively) that have delivered >350 intracranial CAR T doses to >70 enrolled children with recurrent/refractory CNS tumors and DIPG/DMG. While these trials have demonstrated the feasibility and tolerability of repeated, locoregional CAR-T cell dosing, responses have not been uniform in part due to tumor heterogeneity.

METHODS

Seattle Children’s Therapeutics generated multi-antigen (HER2, EGFR806, B7-H3, IL13ra2) quad-CAR T cells and we performed IND-enabling preclinical studies using CNS tumor models including DMG models (PBT-22, PBT-27, and PBT-29).

RESULTS

Quad-CAR T cells were generated by transducing T cells with a mixture of four vectors. The specificity of these CARs is conferred by scFv binding domains derived from the monoclonal antibodies Herceptin, mAb806, and MGA271 for HER2, EGFR806, and B7-H3, respectively. The IL13-zetakine, aligned with NCT00730613, carries an E13Y mutation in place of an scFv for specificity. In vitro, the quad-CAR T cells demonstrated significant in vitro cytolysis and cytokine (IL-2, IFNy, TNFa) production compared to mock (untransduced) CAR-Ts. In vivo, pilot studies in a GFP:ffLuc+Her2 U87 orthoptic xenograft mouse model showed significant survival (p<0.001). To validate against DMG, we are conducting a larger study of single dose intracranial quad-CAR T cells in an orthotopic xenograft PBT-29 DMG mouse model. While ongoing, at day 19 post-treatment there is already a significant bioluminescence decrease (p<0.001). In vivo studies will be completed and complimented by tumor spatial transcriptomics.

CONCLUSION

Quad-CAR T cell targeting of DMG is highly effective preclinically. A phase I trial of repeated, locoregional quad-CAR T cells for children with recurrent/refractory CNS tumors and DIPG/DMG is FDA-approved and will open in 2023.
IMMU-14. WAKING THE SLEEPING GIANT: TLR7/8 AGONIST TREATMENT STIMULATES TUMOR-ASSOCIATED MYELOID CELLS FOR MEDULLOBLASTOMA IMMUNOTHERAPY
Authors: Pauneto Coral Alicea , Hwang Duhyeong , Malawsky Daniel , Kim Kyoungtea , Park Christopher , Sokolsky Marina , Gershon Timothy
Published: June 2023

Medulloblastomas contain large myeloid populations and we have identified a novel therapy that effectively recruits these non-tumor cells for anti-cancer effect. Medulloblastoma myeloid cells have bivalent functions, supporting tumor growth through IGF1 secretion and immunosuppression, or inhibiting tumor growth through diverse mechanisms including phagocytosis. We investigated a nanoparticle formulation of the TLR7/8 agonist Resiquimod (POx-Resiquimod), administered to Gfap-Cre/SmoM2 (G-Smo) mice that are engineered to develop SHH medulloblastomas, using animal survival time studies, flow cytometry and single-cell trancriptomics (scRNA-seq). POx-Resiquimod treatment increased the survival of G-Smo mice as a single agent and sensitized the typically radiation-resistant G-Smo tumors to radiation therapy. Mechanistically, POx-resiquimod increased the proportions of myeloid cells in medulloblastoma, while blocking IGF1 secretion and re-polarizing the myeloid population from anti-inflammatory to pro-inflammatory. POx-resiquimod induced phagocytosis-related genes, including CD72 and the scavenger receptor MARCO. Functional studies confirmed that POx-resiquidmod increased tumor cell phagocytosis, linking molecular changes to changes in myeloid cell behavior. Our data show that the innate immune function of myeloid cells can be harnessed for medulloblastoma treatment and identify the nanoparticle-delivered TLR7/8 agonist POx-Resiquimod as a specific and effective new agent for medulloblastoma immunotherapy that can be combined with existing modalities.
IMMU-16. IDENTIFICATION OF TUMOR REJECTION ANTIGENS FOR PRECISION ADOPTIVE CELLULAR THERAPY FOR PEDIATRIC GLIOMAS
Authors: Trivedi Vrunda , Yang Changlin , Ogando-Rivas Elizabeth , Dyson Kyle , Mitchell Duane
Published: June 2023

BACKGROUND

Identifying tumor rejection antigens remains a major barrier to developing effective antigen-directed immunotherapeutics and their application to pediatric brain tumors. Recent progress in the field of cancer immunogenomics has facilitated the search for tumor-specific antigens by applying comprehensive cancer genomics to tumor antigen discovery. Using a custom antigen prediction pipeline, we performed in silico antigen prediction across a broad array of antigen classes including neoantigens, tumor-associated antigens (TAAs), and fusion proteins for human and murine medulloblastoma tumors. We generated antigen-specific T-cells and validated the antigen-mediated immune responses for the development of precision adoptive cellular therapy.

METHODS

We evaluated WES and RNA-seq data from 170 medulloblastoma patients available through ICGC and performed a comprehensive immunogenomic analysis of subgroup-specific transcription profiles to identify candidate antigen targets. Antigen-specific T-cells were generated from healthy donor PBMCs stimulated against commonly recurring neoantigens and TAAs and immune response was evaluated using IFNγ secretion. Furthermore, we performed tumor antigen discovery for preclinical medulloblastoma models Ptch1 (sonic hedgehog driven) and NSC (Group 3 MYC-driven) and validated the antigen-mediated immune responses of ex vivo expanded antigen-specific T-cells.

RESULTS

Antigen prediction analysis revealed most tumors expressed a higher proportion of immunogenic TAAs than neoantigens and fusion proteins. The neoantigens and TAAs evaluated in this study showed significantly higher IFN-γ secretion in an antigen-dependent manner for both the human and murine platform validation. We thus confirmed the capability to produce functional tumor antigen-specific T-cells that can be leveraged into adoptive cellular therapy for the treatment of medulloblastoma.

CONCLUSION

Medulloblastomas are immunologically heterogeneous, and identifying potential tumor rejection antigens is desirable to develop personalized immunotherapies for the patients. Using a custom antigen prediction and ex vivo antigen-specific T-cell expansion pipeline, we identified potential tumor rejection antigens with important implications for the development of antigen-directed cellular therapies.
LGG-10. TREATMENT-RELATED MYELODYSPLASTIC SYNDROME FOLLOWING CHEMOTHERAPY FOR PEDIATRIC LOW-GRADE GLIOMA
Authors: Power Phoebe , Payne Susannah , Walsh Rebecca , Manoharan Neevika , Nelson Adam
Published: June 2023

Treatment-related myeloid neoplasms are rare though well-defined secondary malignancies associated with prior cytotoxic treatment, (particularly alkylating agents and topoisomerase inhibitors). They are rarely associated with primary central nervous system tumours and have historically carried a very poor prognosis. Pediatric low-grade gliomas (pLGG) are the most common CNS tumours of childhood, and up to 50% of patients will require adjuvant therapy. This has traditionally consisted of low-dose metronomic chemotherapy, although the advent of genomic profiling and identification of molecular drivers of pLGG means novel targeted therapies are changing this paradigm. There has only been a single reported case of treatment-related myeloid leukaemia secondary to pLGG treatment. We present a novel case of a 17-year-old girl with treatment-related myelodysplastic syndrome following chemotherapeutic treatment for pLGG. The patient was initially diagnosed at age 4 with a metastatic pilomyxoid astrocytoma (primary suprasellar lesion with spinal metastases) and received first-line treatment with a vincristine and carboplatin regimen. She had disease progression at age 7 and received second-line treatment with thioguanine, procarbazine, lomustine and vincristine. Following further progression at age 16, a biopsy of the suprasellar mass showed a pilocytic astrocytoma with a KIAA1549-BRAF fusion. Prior to commencing a targeted treatment as third-line therapy, she was noted to have a macrocytic anaemia, which subsequently evolved to a bicytopenia. Bone marrow analysis showed a hypocellular marrow with an abnormal myeloid clone with a chromosomal 1q gain, consistent with a diagnosis of treatment-related myelodysplastic syndrome. Germline analysis was negative for bone marrow failure predisposition gene abnormalities. She is currently undergoing workup for bone marrow transplant. Given the poor prognosis of treatment-related myeloid neoplasms, this case represents an important note of caution when choosing appropriate therapy for pLGG, especially given the evolving role for targeted treatments in this disease with otherwise very favourable long-term survival.
LGG-16. NOVEL COMBINATION THERAPIES FOR PEDIATRIC LOW-GRADE GLIOMA AND CHARACTERIZATION OF THE UNDERLYING CELL DEATH MECHANISMS
Authors: Zeiser Constantia , Rösch Lisa , Herter Sonja , Peterziel Heike , Selt Florian , Milde Till , Witt Olaf , Oehme Ina
Published: June 2023

BACKGROUND

The majority of pediatric low-grade gliomas (pLGGs) harbor a MAPK/ERK pathway overactivating alteration, making them suitable for MAPK-targeted therapies such as MEK inhibition. However, MEK inhibitor treatment alone is in most cases not sufficient to induce complete response, and a rapid rebound of the tumor is the consequence after withdrawal of the therapy.

METHODS

To identify novel cytotoxic drug combinations, we screened 89 clinically relevant drugs in combination with the MEK inhibitors trametinib and binimetinib. We assessed the regression of cultured 3D microtumors of patient-derived BT40 and BT314 cells, both harboring a BRAFV600E mutation. Depending on the inducible expression of SV40 large T antigen, the BT314 model can reflect two states, proliferation and oncogene-induced senescence. The area of spheroids was measured both in brightfield and with the fluorescent dye TMRE (mitochondrial polarization) at the start and the end of the treatment (6 days). Moreover, metabolic activity was determined through bulk ATP measurement. Drug hit combinations were further analyzed for the successful induction of cell death using high-content microscopy (HCM) imaging and enzymatic caspase activity assays. The microscopic readouts included Hoechst 33342 for the detection of nuclear morphology, BODIPY for sensitizing lipid peroxidation and CM-H2DCFDA as a general oxidative stress indicator. The images were analyzed with the automated image analysis program CellProfiler and the machine learning application CellProfiler Analyst.

RESULTS

The screening identified the following drug hits: navitoclax (BCL-2 family inhibitor), BRAF inhibitor dabrafenib, mTOR inhibitor everolimus and selinexor, a selective inhibitor of nuclear export. All drugs increased apoptotic cell death and ROS levels at clinically achievable drug concentrations, except the mTOR inhibitors. These results are currently validated in vivo with BT40 zebrafish embryo xenograft models.

CONCLUSION

Combinations of MEK inhibitors with navitoclax, dabrafenib or selinexor resulted in sufficient apoptosis to induce regression of pLGG microtumors in vitro.
MDB-01. ELUCIDATING THE ROLE OF THE BAIAP2-CDC42 INTERACTION MEDULLOBLASTOMA
Authors: Ruiz Luz , Suter Rober , Jangde Nitish , Ayad Nagi
Published: June 2023

Medulloblastoma is the most common malignant pediatric brain tumor. Despite advancements in treatment, there is still no significant improvement in survival rates. This indicates novel, more effective treatment options are necessary. In addition, when medulloblastoma is metastasized outside the central nervous system, there is worst mortality rate. The regulatory properties of metastasis and invasion are still not well understood. We sought to identify potential key regulators for these processes in medulloblastoma. Single-cell RNA sequencing data was collected for medulloblastoma patients and an experiment with a Tg (Neurod-Smoothened*A1) mouse. We identified BAIAP2 and CDC42 to be differentially expressed compared to non-tumor brain cells. Previous literature shows that these genes are implicated in oncogenic properties including invasion, migration, and proliferation in different cancers and neurological diseases. We hypothesize that distinct cell populations within medulloblastoma should show different expressions of BAIAP2 and CDC42, specifically those involved in invasion and migration. We determined that BAIAP2 and CDC42 have higher expression in medulloblastoma tumors compared to the control. In our data, the cell population enriched for microtubule depolymerization had a high expression of BAIAP2, unlike the other clusters. This study is important because BAIAP2 and CDC42 have yet to be characterized in medulloblastoma. Our data suggest a potential role for BAIAP2 and CDC42 in the pathophysiology of medulloblastoma which can possibly be a target for future studies.
MDB-02. NUCLEAR ENVELOPE PHOSPHATASE CTDNEP1 MUTATIONS POTENTIATE AGGRESSIVE MEDULLOBLASTOMA BY TRIGGERING MYC ACTIVATION AND GENOMIC INSTABILITY
Authors: Lu Richard , Luo Zaili
Published: June 2023

MYC-driven medulloblastomas are highly aggressive childhood brain tumors, however, the molecular and genetic events triggering MYC amplification and malignant transformation remain elusive. Here we report that mutations in CTDNEP1, a CTD nuclear-envelope-phosphatase, are the most significantly enriched recurrent alterations in MYC-driven medulloblastomas, and define high-risk subsets with poorer prognosis. Ctdnep1 ablation promotes the transformation of murine cerebellar progenitors into Myc-amplified medulloblastomas, resembling their human counterparts. CTDNEP1 deficiency stabilizes and activates MYC activity by elevating MYC serine-62 phosphorylation, and triggers chromosomal instability to induce p53 loss and Myc amplifications. Further, phosphoproteomics reveals that CTDNEP1 post-translationally modulates the activities of key regulators for chromosome segregation and mitotic checkpoint regulators including topoisomerase TOP2A and checkpoint kinase CHEK1. Co-targeting MYC and CHEK1 activities synergistically inhibits CTDNEP1-deficient MYC-amplified tumor growth and prolongs animal survival. Together, our studies demonstrate that CTDNEP1 is a potent tumor suppressor in highly aggressive MYC-driven medulloblastomas by controlling MYC activity and mitotic fidelity, pointing to a CTDNEP1-dependent targetable therapeutic vulnerability.
MDB-17. THE PTBP2 SPLICING FACTOR IS ESSENTIAL IN GROUP 3/4 MEDULLOBLASTOMA
Authors: Caisova Veronika , Rivero-Hinojosa Samuel , Chintala Navya , Lu I-An , Huizhen Zhang , Mochizuki Aaron , Yang Jianhua , Rood Brian
Published: June 2023

Medulloblastoma (MB) is a common malignant pediatric brain tumor with significant heterogeneity among its four molecular subgroups WNT, SHH, Group 3 and 4. Group 3/4 MB are aggressive with a relatively poor prognosis indicating a critical need for novel therapeutic targets. Since the transcriptomic profiling of MB subgroups has not resulted in the expected identification of therapeutic potential, we focused on a proteomic approach. Building upon our previously published quantitative proteomic study, we selected 157 proteins significantly over-expressed in Group 3/4 MB. By using targeted loss-of-function CRISPR-Cas9 screen in four MB cell lines, we identified 17 essential genes shared by at least 2 of the cell lines. The PTBP2 splicing factor was essential to the survival of all cell lines. PTBP2 is an RNA binding protein involved in splicing regulation playing an important role during neuronal maturation. We hypothesize that persistent expression of PTBP2 results in a differentiation arrest and preservation of proliferative potential. To evaluate the role of PTBP2 in group 3/4 MB biology, we used single target CRISPR-Cas9 to stably knock-out PTBP2 expression in D556 and MB002 MB cells. We performed bulk RNA-seq and quantitative proteomics of these KO clones along with CLIP-seq to map PTBP2 targeted transcripts. We also performed phenotype assays in KO clones. RNA-seq in PTBP2 KO MB cells revealed 2,213 differentially expressed genes predominantly involved in neuronal differentiation and antigen presentation. These genes were cross-referenced with quantitative proteomics and eCLIP data. Phenotype assays of PTBP2 KO cells revealed reduced proliferation and migration compared to controls. To study the effect of PTBP2 on MB differentiation, we stimulated MB002 PTBP2 KO cells with FBS and observed increased surface attachment and differentiated morphology compared to controls. This suggests that persistent PTBP2 expression inhibits differentiation in MB cells with an attendant increase of proliferation activity.
MDB-28. DEEP LEARNING-BASED PERSONALIZED SURVIVAL PREDICTION FOR MEDULLOBLASTOMA
Authors: Stefan Sabina , Northcott Paul , Hovestadt Volker
Published: June 2023

Medulloblastoma is one of the most common malignant brain tumors in children and a leading cause of cancer-related death in this age group (5-year survival rate of ~70%). However, survival outcomes are heterogeneous, and currently associated with only a small number of clinical and molecular parameters. Instead, in this work we aim at exploiting the wealth of hidden information in genome-wide DNA methylation array data to predict accurate personalized survival probability curves for Group 3 and 4 medulloblastoma patients, the subgroups associated with the most heterogeneous outcomes. To accomplish this, we implemented a sparse neural network trained on DNA methylation and copy-number variation (CNV) profiles of over 900 medulloblastoma patients. Our network is designed specifically to leverage censored data for training, and makes no assumptions about the underlying distribution of the output survival probability curves. Furthermore, the architecture of our network is biologically interpretable, enabling us to probe the underlying biology driving survival. Our results demonstrate excellent discrimination and calibration, with a 5-year AUROC of 0.8. We compare our results to currently used stratification schemes on validation cohorts, including SJMB03 clinical trial data, and demonstrate significantly improved risk stratification (c-index of 0.66 vs 0.74, p < 0.0001). We find several cases in which patients assumed to be low-risk were predicted to progress rapidly, and vice versa, motivating possible refinement of risk categories in clinical practice. Our approach, which is based entirely on DNA methylation array data, may facilitate the de-escalation of therapy for low-risk patients to minimize treatment-related side effects and the intensification of treatment for high-risk individuals. The approach can be extended to other cancer types, and highlights the value of AI in healthcare towards realizing the goal of personalized medicine.
MDB-31. PRELIMINARY STUDY ON BIOLOGICAL SIGNIFICANCE OF WTX G435D MUTATION IN MEDULLOBLASTOMA
Authors: Hu Yuanjun , Wang Jing , Chen Zhongping
Published: June 2023

BACKGROUND:

Previously, we reported a case of familial medulloblastoma without hereditary tumor syndrome. Through analysis of the whole genome sequencing of the family members, we found a common germline WTX (c.1863C>T, p.Gly435Asp) mutation in this family: cytosine (C) at position 63411863 on X chromosome was replaced by thymine (T), and the corresponding amino acid was glycine Gly (G) at position 435, which was converted to aspartic acid Asp (D). We conduct this study to explore the biological significance of this mutation in medulloblastoma cell lines.

METHODS:

Medulloblastoma cells (cell lines and primary cells) with stable WTX (c.1863C > T) hybrid mutation were contstrcuted by lentivirus transfection. The effects of WTXG435D on proliferation, invasion and chemosensitivity of medulloblastoma cells were investigated in vitro and in vivo.

RESULTS:

Proliferation and invasion ability of WTXG435D medulloblastoma cell were significantly weaker than WTX WT cells, and they were more sensitive to radiation and chemotherapy(cisplatin, vincristine) treatment in vitro. In vivo, animal experiments also showed that intracranial in situ tumors formed by WTXG435D medulloblastoma cells were more sensitive to radiotherapy and chemotherapy than in situ tumors formed by WTXWT ones, and the survival was longer.

CONCLUSION:

WTX (c.1863C>T, p. Gly435Asp) mutation could reduce the proliferation and invasion ability of medulloblastoma cells, and enhance the sensitivity of radiotherapy and chemotherapy. Which could be a potential therapeutic target for further investigation.
SURG-03. LAYER-BY-LAYER CORE-SHELL NANOPARTICLES FOR THE DELIVERY OF HDAC INHIBITORS TO THE CENTRAL NERVOUS SYSTEM
Authors: Marand Michael H , Han Emily , Kim Seung Hyun , Hammond Paula T , Straehla Joelle P
Published: June 2023

Diffuse midline gliomas (DMGs) present unique challenges in pediatric cancer care. The location of DMGs often renders the tumor inoperable and radiation produces only a temporary effect. One promising approach in DMG treatment is histone deacetylase (HDAC) inhibitors. However, HDAC inhibitors are difficult to deliver to primary central nervous system (CNS) tumors because of low blood-brain barrier (BBB) permeability and poor accumulation in tumor tissues. The BBB permeability is particularly restricting for DMGs, which maintain a relatively intact BBB. To overcome these delivery challenges, we developed a new polymer-lipid core-shell nanoformulation for the delivery of HDAC inhibitors to the CNS that does not rely on polyethylene glycol (PEG) for colloidal stability. Removing PEG allows for surface charge manipulation to generate charged nanoparticles amenable to layer-by-layer assembly with alternately charged polyelectrolytes. This modular platform allows the addition of targeting moieties to enhance the delivery of HDAC inhibitor core-shell nanoparticles across the BBB and into DMG cells. HDAC inhibitors panobinostat and quisinostat were loaded into core-shell nanoparticles comprised of a poly(lactide-co-glycolide) (PLGA) core and a phospholipid shell. Nanoparticles were characterized using dynamic light scattering and transmission electron microscopy exhibiting favorable properties for in vivo delivery (panobinostat nanoparticle diameter 91.6 ± 1.0 nm, polydispersity index 0.115 ± 0.013). The release of HDAC inhibitors from layered and unlayered core-shell nanoparticles was investigated using high-performance liquid chromatography. The deacetylating activity of nanoencapsulated agents was confirmed in vitro in patient-derived DMG neurosphere models. CNS pharmacokinetic parameters are currently being investigated after intravenous delivery of drug-loaded nanoparticles in non-tumor-bearing mice, including cerebrospinal fluid and brain tissue concentrations of the encapsulated agents. Future studies will investigate brain biodistribution of core-shell HDAC inhibitor nanoparticles in orthotopic DMG tumor-bearing mice, comparing intravenous and local delivery strategies.
OTHR-01. SUCCESSFUL DEVELOPMENT OF A LOCAL-REGIONAL POST-MORTEM BRAIN TUMOR DONATION PROGRAM
Authors: Mark Melissa , Sowell Kelsey , Zapata Deborah
Published: June 2023

Patient tumor tissue is vital to development of therapeutic interventions in the setting of refractory CNS tumors. Patients and families who participate in tumor donation (TD) report meaning making and improved bereavement outcomes. Provider discomfort is a significant barrier to autopsy participation. Families who are not approached for tumor donation report distress or a feeling of a missed opportunity. Our center developed a process to offer all patients who died from their disease the option to participate in TD as a standard of care. Discussions around TD are best done in the context of a multidisciplinary team well known to the patient and family lead by the treating oncologist. Opportunities to discuss TD present themselves at predictable time points in the disease trajectory: day one talk, treatment discussion, time of recurrence, clinical deterioration, advance care planning discussions, end of life, and immediately-post mortem. Our practice is in the setting of a free-standing children’s hospital. We are not a phase one site. In 2022 seven patients in our neuro-oncology program died from progressive disease. Seven of seven chose to participate in TD. We partnered with a regional phase one center and SWIFTY foundation to coordinate logistics and enrollment. All tumor procurements occurred off site at the funeral home selected by each family. To facilitate family comfort with TD a local team member was present at the time of harvest and kept family updated in process in real time via phone call at the following time points: time of harvest, completion of harvest, tissue arrival at research site. Future directions include offering structured post-mortem visits with families to review research findings with primary treating oncologist in conjunction with the research team and conducting prospective studies with bereaved families to better understand the impact of TD on bereavement.
OTHR-09. A RETROSPECTIVE COHORT STUDY EXAMINING RADIOLOGIC AND CLINICAL CHARACTERISTICS OF CHILDREN AND ADOLESCENTS WITH ATYPICAL/COMPLEX PINEAL CYSTS
Authors: Tahbaz Meghan , Malvar Jemily , Khan Sara , Tamrazi Benita , Chi Yueh-Yun , Robison Nathan
Published: June 2023

INTRODUCTION

The significance of atypical or complex pineal cysts (CPC) on magnetic resonance imaging (MRI) is often unclear, and the appropriate management has not been well defined. We conducted a retrospective cohort study of children and adolescents (0-18 years of age) with complex pineal cysts noted on brain MRIs obtained at Children’s Hospital Los Angeles (CHLA) prior to 05/31/2022.

METHODS

We retrospectively reviewed electronic medical records at CHLA to identify patients <18 years of age who were diagnosed with CPC upon MRI between January 1, 2010 and May 31, 2022. CPC were defined as cysts that are multi-cystic, enhancing, ≥1 cm in size, have a solid component, or exhibit restricted diffusion. Patients were identified by an automated Boolean search of a radiology report database; individual reports were then reviewed for eligibility. Patients with normal pineal glands or simple (<1 cm) pineal cysts were excluded. Electronic medical records were evaluated for patient chief complaint, initial clinical and radiographic symptoms, tumor markers (beta-human chorionic gonadotropin and alpha-fetoprotein), and final diagnosis.

RESULTS

We identified a cohort of 175 patients; 106 (61%) were female. Mean age at initial MRI was 8.36 years of age (SD 5.36). Tumor markers were measured in 52 patients (30%). The most common presenting symptoms for patients were headache (34%), seizures (26%), nausea/vomiting (19%), weakness/fatigue (17%), and dizziness (12%). Additional presenting symptoms included ataxia, sensory changes, and anxiety. Pineal malignancies were identified in 4 patients (2.2%), which consisted of a pituitary pure germinoma, a pineal region parenchymal tumor, and two pineoblastomas. The remaining 98% of patients (171 patients) either had a benign pineal cyst or were categorized as unknown.

CONCLUSION

Most CPC are not associated with malignant neoplasms and represent incidental findings with scant clinical significance.
OTHR-13. IDENTIFYING INDIVIDUALS WITH PRIMARY CENTRAL NERVOUS SYSTEM TUMORS AT RISK FOR HEREDITARY CANCER SYNDROMES USING A STATEWIDE CANCER REGISTRY
Authors: Whipple Nicholas , Yu David Zhe , Cheshier Samuel , Schiffman Joshua , Curtin Karen , Kohlmann Wendy
Published: June 2023

INTRODUCTION

Central Nervous System (CNS) tumors are associated with hereditary cancer syndromes (HCS), especially among pediatric and AYA populations. Using population-based resources, we evaluated the proportion of patients meeting HCS testing criteria.

METHODS

Cases of CNS tumors diagnosed in individuals ages 0-39 were identified through the Utah Cancer Registry. Using the Utah Population Database, cases were linked to cancer family history and, when available, to HCS genetic data. A genetic counselor and pediatric neuro-oncologist reviewed family pedigrees containing ≥2 CNS tumors.

RESULTS

We identified 347 CNS tumors in 320 individuals, from 161 families (FSIR P<0.05). The most common tumors were: astrocytoma (n=93), pituitary (n=38), glioma (n=34, 4 optic nerve), glioblastoma (n=32), meningioma (n=31), oligodendroglioma (n=24), and medulloblastoma (n=20). Sixteen individuals had multiple cancers: 9 had ≥ 2 CNS tumors, 7 had CNS and non-CNS tumors. Of those with multiple tumors, 3 met criteria for NF2, 1 for NF1, and 1 for Chompret. 213 individuals (67%) met criteria for HCS testing based on their personal cancer history. Criteria met included glial tumor (< age 40) (n=163), NF2 (n=14), NF1 (n=12), rhabdoid tumor predisposition (n=10), Chompret (n=7), VHL (n=3), medulloblastoma—SHH (n=3), DICER1 (n=1). Germline data were available for 23 individuals, and 14 had a germline mutation (Li Fraumeni Syndrome=8, VHL=3, APC=1, DICER1=1). An additional 12 people met Chompret criteria based on their CNS tumor plus family history. Of these 4 had germline testing, of which 3 had LFS.

CONCLUSIONS

In our cohort, 70% of individuals met criteria for HCS testing. However, this may be an underestimate because many syndromes associated with CNS tumors also predispose to non-CNS tumors, which were not included in the initial query. Research on the actual prevalence of HCS in individuals with CNS tumors requires germline data in a queryable form in the medical record.