bluuebunny/crossref_metadata_2025 huggingface dataset:
HGG-43. DIFFUSE PEDIATRIC HIGH GRADE GLIOMA SUCCESSFULLY TREATED WITH MULTIMODAL THERAPY
Authors: Agarwal Vibhuti , Nagasubramanian Ramamoorthy , Maxwell Rochelle , Douglas-Lindsay Dorothea , Mercado Catherine , Hayes Laura , Chandra Tushar
Published: June 2024

BACKGROUND

Pediatric high grade glioma (HGG) have a dismal prognosis despite aggressive treatment. In this report, we discuss a patient with HGG successfully treated with combination of resection, radiotherapy, chemotherapy, and biologic therapy.

RESULTS

An 8-year-old male presented with intermittent headaches, vomiting and fatigue. Imaging demonstrated four solid/cystic enhancing intra-axial lesions within the left cerebral hemisphere- two within the left frontotemporal region, one in the superior parietal region, and one in the temporal lobe, all with perilesional edema and resultant subfalcine herniation with midline shift. The patient underwent subtotal resection of the frontotemporal and parietal lesions. Histopathology was consistent with glioblastoma. Whole exome sequencing revealed alterations in TP53, ATRX, PTEN, TSC2 as well as subclonal mutation in NF1. The tumor was unable to be further classified by DNA methylation. However histopathologic and molecular findings support the diagnosis of diffuse pediatric-high grade glioma, H3-wildtype and IDH-wildtype. The patient received adjuvant 59.4 Gy focal proton therapy with concurrent temozolomide and maintenance chemotherapy with temozolomide and lomustine for 6 cycles. End of therapy imaging demonstrated complete resolution of all sites of disease. Due to high likelihood of recurrence, the patient was subsequently started on targeted therapy with everolimus and ribociclib which continue to be well tolerated without dose adjustments. The patient remains stable and without recurrence 2.5 years since diagnosis, and 15 months since initiation of biologic therapy. Additionally, the patient underwent testing for cancer predisposition which revealed presence of TP53 heterozygous mutation consistent with Li-Fraumeni syndrome. The patient remains without other malignancies on surveillance imaging per LFS guidelines.

CONCLUSION

Our case report illustrates the value of both chemotherapy and biologic therapy in treatment of HGG. In addition to this, it emphasizes the importance of germline testing for cancer predisposition in patients with high grade tumors.
HGG-48. THE BLOOD-BASED TELOMERIC DNA C-CIRCLE ASSAY CAN DETECT ALTERNATIVE LENGTHENING OF TELOMERES (ALT) IN PEDIATRIC HIGH-GRADE GLIOMAS
Authors: Lehman Tenley E , Deal Jenna L , Lee Jihyun , Foster Jessica B , Koptyra Mateusz P , Burrow Trevor A , Koneru Balakrishna , Cole Kristina A , Reynolds C Patrick
Published: June 2024

BACKGROUND

High-grade gliomas (HGG) comprise ~10% of pediatric brain tumors; 40% of pediatric HGG use the alternative lengthening of telomeres (ALT) mechanism to maintain replicative immortality. ALT cancers share a unique biology providing potential therapeutic targets. Extrachromosomal telomere DNA repeats, termed C-circles, can be detected by a unique PCR assay, providing a sensitive and specific biomarker for ALT cancers. C-circles have been detected in ALT tumors and serum of ALT patients. We have adapted the C-circle assay (CCA) to provide a sensitive and specific assay with cfDNA in patient plasma. Here we determined if cfDNA in plasma can be used to detect patients with ALT-positive HGG.

METHODS

Frozen plasma samples were collected in Streck tubes at time of surgery prior to resection from patients with HGG. DNA was extracted and quantified. Isothermal rolling C-circle amplification and real-time telomere PCR was performed followed by analysis. The C-circle positive neuroblastoma cell line, CHLA-90, and C-circle negative neuroblastoma cell line, CHLA-20, served as the positive and negative controls respectively. CCA values in plasma of 2 and above indicate positivity for C-circles.

RESULTS

Plasma samples were analyzed by CCA from three pediatric patients whose brain tumors were previously biopsied and identified as ATRX mutation positive. ATRX mutation indicates ALT however, not all ALT cancers have ATRX mutations. All plasma samples were above the 2.0 cutoff at 3.37, 3.13, and 4.59 and thus classified as C-circle positive.

CONCLUSIONS

This preliminary cohort shows that the CCA has potential for identifying ALT pediatric brain tumors using cfDNA from plasma. As novel therapies effective against ALT HGG are developed, the plasma CCA may allow accelerated initiation of neoadjuvant therapy to shrink tumor prior to surgical resection and lessen or prevent the need for tumor biopsy. Expansion of the initial test cohort is underway. Supported by NCI UO1 CA63988.
HGG-49. INTERNEURONS THAT BITE: A CELLULAR DELIVERY SYSTEM FOR PEDIATRIC HIGH-GRADE GLIOMA
Authors: Brosius Stephanie N , Manley William , Harvey Kyra , Galanaugh Jamie , Labella Kay , Liou Angela , Anderson Stewart , De Raedt Thomas
Published: June 2024

BACKGROUND

High-grade gliomas (HGG) represent the leading cause of cancer-related mortality in children due to a lack of curative therapies. Challenges of cellular therapies in brain tumors include the lack of unique tumor antigens, downregulation of targeted antigens, and immune suppressive tumor microenvironment. To circumvent these obstacles, we devised a cellular delivery system using post-mitotic migratory cortical inhibitory interneuron precursors (MCIPs) to deliver therapeutic payloads in an antigen-independent manner. Notably, HGGs secrete the same chemoattractants stimulating long-distance MCIP migration as during normal fetal development, leading to the hypothesis that MCIPs would preferentially migrate to HGG cells.

METHODS

MCIP to HGG cell migration was assessed in vitro using transwell migration assays, and in vivo via stereotactic injection of MCIP and glioma xenografts in nude mice. As proof of principle, MCIPs were equipped with an EGFR or CD19 control bispecific T-cell engager (BiTE) which activates T-cells upon their linkage to the tumor cells resulting in glioma elimination. Equipped MCIPs were co-cultured with HGG cells and CD8 T-cells at an effector to target ratio of 4:1. Results were validated in vivo via xenografts of HGG, MCIPs, and either a single dose of CD8 T-cells or repeated T-cell dosing via intraventricular cannula. Survival was evaluated via Kaplan-Meier curves.

RESULTS

MCIPs migrated preferentially to the majority of HGG cell lines in vitro and in vivo. This migration was mediated, at least in part, via CXCR4 ligands. MCIPs secreting an EGFR-BiTE potently killed HGG cells in vitro versus CD19-BiTE controls. Furthermore, nude mice xenografted with HGG and EGFR-expressing MCIPs experienced prolonged survival versus controls.

CONCLUSION

These data suggest that MCIPs form a viable cellular delivery system and can be equipped with various agents targeting HGG. Modified MCIPs could be differentiated from induced pluripotent stem cells and injected into the resection cavity margins to eliminate residual cells.
HGG-53. MULTI-DIMENSIONAL INTEGRATIVE PROFILING IDENTIFIES BCL2L1 METHYLATION AS A PREDICTIVE BIOMARKER FOR MCL-1 ACTIVITY IN PEDIATRIC HIGH-GRADE GLIOMAS
Authors: Adjumain Shazia , Sun Claire Xin , Bradshaw Gabrielle , Chew Nicole , Tsui Vanessa , Lee Hanbyeol , Loi Melissa , Zhukova Nataliya , Habarakada Dilru , Ludlow Louise , Neeman Naama , Daniel Paul , Firestein Ron
Published: June 2024

BACKGROUND

Pediatric high-grade gliomas (pHGGs) pose a significant challenge as the most aggressive central nervous system tumors in children. The lack of effective treatment and poor survival rates emphasize the critical need for innovative therapies to improve the prognosis of pediatric patients with pHGG.

METHODS

We executed CRISPR-cas9 knockout (KO) screenings in 65 pediatric and 10 adult high-grade glioma (HGG) cell lines to explore unique functional dependencies associated with pHGGs. Drug assays were carried out to assess the targetability of a gene dependency of interest in pHGG cell lines. Subsequently, Random Forest machine learning algorithm was employed on ‘omics’ datasets to identify biomarkers indicative of drug response. Finally, biomarkers were confirmed through sequencing-based methods across various pediatric cancers.

RESULTS

CRISPR-cas9 KO screens revealed 8 crucial genes essential for pHGG growth, namely MCL-1, ATIC, DHFR, EED, HDAC2, PARP1, PDK1, PIK3CA and TYMS. Among these, Myeloid Cell Leukemia (MCL-1) was further characterized as it emerged as the top differential genetic dependency in pHGGs. Consistent with this, MCL1 inhibitors exhibited potent anti-cancer activity on 43% of pHGG cell lines. Multi-feature prediction analysis identified 140 features correlated to response. Strikingly, a previously undescribed methylation site within the BCL2L1 locus, cg00300298, ranked in the top 5% of features. Tissue analysis revealed a wide range of other pediatric brain cancers that harbor the BCL2L1 cg00300298 methylation mark as compared to non-malignant brain tissue. Lastly, we validated the utility of BCL2L1 methylation as a predictive biomarker of MCL1 inhibitor sensitivity across a large panel of pediatric brain cancer cell lines.

CONCLUSION

Using an integrated genomic approach, we identify MCL1 as a distinct therapeutic target in BCL2L1-methylated pediatric brain cancers. This offers a rational approach for stratifying patients who may benefit from MCL1 inhibitors.
IMG-17. CHANGES IN GRAY MATTER VOLUMES AND THEIR RELATION WITH NEUROPSYCHOLOGICAL DOMAIN SCORES IN SURVIVORS OF A CHILDHOOD POSTERIOR FOSSA TUMOR
Authors: Bullens Kristien , Blommaert Jeroen , SLeurs Charlotte , Lemiere Jurgen , Jacobs Sandra
Published: June 2024

Posterior fossa tumors (PFT) often need neurotoxic radiotherapy (RT). These may affect the brain and contribute to neurocognitive impairment later in life. Therefore, we investigated region-based gray matter volumes (GMV) and their relation to neurocognitive functioning (NF) in PFT survivors. T1-weighted MRI (MPRAGE, resolution=.98x.98x1.2mm) and NF composite scores based on a compressive neuropsychological test battery: total Intelligence, verbal comprehension, working memory, perceptual reasoning, processing speed, language, learning and memory, complex attention (CA), and cognitive flexibility (CF), were analyzed for 17 survivors of PFT (12males, 5females, mean age at diagnosis=8.5±4.5y) and 19 age- and sex-matched controls. Cortical- and subcortical GMV were analyzed with region-based morphometry (RBM, fastsurfer). GMV and NF-scores were compared between controls and survivors, and surgery-only versus RT. Post-hoc analyses correlated GMV with NF-scores and clinical parameters (radiotherapy-dose, time since treatment, and time since diagnosis). Comparing controls with survivors, lower GMV were found for overall subcortical GMV (pFDR=0.020) as well as for several subcortical subregions: bilateral thalamus and bilateral ventral diencephalon (pFDR<0.01). Larger GMV was observed in the left inferiotemporal region (pFDR=0.027). Survivors obtained lower NF-scores on all domains (pFDR<0.007) except for CA and CF. RT-survivors had lower GMV in bilateral thalamus (pFDR<0.05), right ventral diencephalon (pFDR=0.033), and central corpus callosum (pFDR=0.033) compared to surgery-only. Higher GMV were found in bilateral middle temporal regions (pFDR<0.05). NF-scores were lower in RT- survivors, but none reached statistical significance after multiple comparison correction. Significant, positive correlations between GMV of bilateral thalamus and right ventral diencephalon was found for the working memory. Differences in GMV and NF scores were observed in PFT survivors. In this limited group, RT-survivors showed more deviant GMV compared to surgery-only survivors and controls. These results also suggest a potential relationship between deviant GMV and worse NF. Notwithstanding, research in larger populations is needed to validate our findings.
IMG-21. HOW CAN WE BEST UTILISE HISTORICAL IMAGING DATASETS FOR RESEARCH IN PAEDIATRIC NEURO-ONCOLOGY? A REVIEW OF HISTORICAL PRE-OPERATIVE IMAGING PERFORMED FOR 92 PAEDIATRIC BRAIN TUMOUR PATIENTS WITH COMPARISON TO 2021 SIOPE GUIDELINES
Authors: Dockrell Simon , Vaughan Kate , Kilday John-Paul , Kamaly-Asl Ian , McCabe Martin , Stivaros Stavros
Published: June 2024

BACKGROUND

Utilisation of historical imaging is important for studying long-term outcomes in paediatric brain tumours often pooling data across multiple centres retrospectively over many years. Disparities in MRI sequence parameters, imaging planes, fields of view and resolution limit quantitative radiomic analysis and segmentation algorithms. We review historical imaging datasets, analysing the MRI scans performed assessing suitability for modern research techniques.

METHODS

Retrospective review of presenting MRI scans was performed in 92 paediatric brain tumour patients between 2006-2020. Whether imaging was performed internally at our paediatric neurosciences centre or externally at their referring hospitals was recorded. Image sequences, planes and slice thickness were compared with 2021 SIOPE guidelines for paediatric brain tumour imaging. T2 signal intensities for tumour, white and grey matter were compared for scans completed in different centres. Statistical testing was performed with T-Test and Paired T-Test.

RESULTS

75% of patients had all SIOPE essential sequences and 60.9% were in the recommended planes. Only 1 patient had the desired slice thickness in all sequences recommended for 1.5T scanners. 38.5% had T1 and 27.8% had post-contrast T1 in the ≤1mm slice thickness recommended for 3T scanners. Comparison between 62 internal and 30 external scans revealed statistically significant differences in T2 signal intensities for regions of interest (ROI) within tumour, white and grey matter (p<0.01). Comparison of matched ROI for 12 patients imaged internally and externally demonstrated statistically significant differences in T2 signal intensities (p<0.05). Differences persisted despite normalisation of T2 signal intensity as ratios between tumour and the weighted mean of white and grey matter (p<0.01).

CONCLUSIONS

This study highlights the challenges of non-standardisation of imaging resolution and acquisition parameters in historical imaging. One approach to utilise these datasets is to use qualitative classifications where human experts label imaging features and encode data for future statistical or machine learning analysis.
IMG-22. ASL PERFUSION LIGHTBULB SIGN: A POTENTIAL PATHOGNOMONIC FEATURE OF PEDIATRIC POSTERIOR FOSSA HEMANGIOBLASTOMA
Authors: Simsek Onur , Sheth Nakul , Manteghinejad Amirreza , Wannasarnmetha Mix , Bhatia Aashim
Published: June 2024

INTRODUCTION

Hemangioblastoma is a rare vascular tumor which occurs within the central nervous system in children. Differentiating hemangioblastoma from other posterior fossa tumors can be challenging on imaging and preoperative diagnosis can change neurosurgical approach. We hypothesize a ‘lightbulb sign’ (diffuse homogenous intense hyperperfusion within solid component of tumor) will help differentiate hemangioblastoma from other posterior fossa tumors.

METHODS

In this retrospective case-control study, we only included pathology-proven cases of hemangioblastoma, while the control group consisted of other randomly selected pathology-proven posterior fossa tumors from January 2022 to January 2024. Two blinded neuroradiologists analyzed all applicable MRI sequences. Their perfusion analysis also included the “lightbulb sign” as an extra criterion. Disagreements between the radiologists were confirmed by a third pediatric neuroradiologist. Chi-square and Fisher’s exact test were used to analyze the data.

RESULTS

95 patients were enrolled in the study, 57(60%) were male. The median age at diagnosis was 8 (IQR: 3-14). Out of the enrolled patients, 8 had hemangioblastoma, and 87 had other posterior fossa tumors, including medulloblastoma (n=31), pilocytic astrocytoma (n=23), posterior fossa ependymoma type A (n=16), and other tumors (n=17). The comparison of hemangioblastoma vs non-hemangioblastoma showed that peripheral edema (p=0.020, OR=1.8) and T2 flow void (p=0.021, OR=1.7) favors hemangioblastoma, whereas reduced diffusion (low ADC) (p=0.002, OR=2.3) and ventricular system extension (p=0.001, OR=2.4) favors non-hemangioblastoma tumors. 42 cases also had perfusion studies. While high perfusion favors hemangioblastoma (p=0.021, OR=2.9), the lightbulb sign shows a complete distinction since all the ASL series of hemangioblastoma cases (n=4) showed the lightbulb sign, whereas none of the non-hemangioblastoma cases (n=38) showed the sign (p<0.001).

CONCLUSION

Lightbulb-like intense and homogenous hyperperfusion pattern on ASL allows differentiation of hemangioblastoma from other posterior fossa tumors in children.
IMG-24. MAPK-ALTERED PEDIATRIC LOW-GRADE GLIOMA: MRI HINTS TO EXPLAIN THE INTERPLAY BETWEEN GLIOMA AND IMMUNE CELLS
Authors: Ramaglia Antonia , Piccolo Gianluca , Molteni Marta , Mercuri Claudia , Gaggero Gabriele , De Marco Patrizia , Pavanello Marco , Rossi Andrea , Garrè Maria Luisa , Milanaccio Claudia , Verrico Antonio
Published: June 2024

BACKGROUND

In MAPK-altered pediatric low-grade glioma (pLGG), immune infiltration may be involved in treatment response. It is debated whether tumor immune cell infiltration is due to expansion of endogenous resident microglia or to the active recruitment of bone marrow-derived microglial progenitors from the bloodstream. This study aimed to investigate the relation between neuroradiological features of MAPK-altered pLGG and treatment response to MAPK-inhibitors (MAPKi).

METHODS

We conducted a retrospective analysis of all patients with unresectable BRAF-V600E mutated brain pLGG, radiotherapy naïve, treated with MAPKi at our institution since 2015. MRI studies were reviewed by two experienced neuroradiologist and tumor response assessed according to RAPNO criteria.

RESULTS

12 patients were enrolled (9 female). Median age at treatment start was 6.2 years (range 2.7–14.3 years). Four were pilocytic astrocytomas, 6 gangliogliomas, and 2 desmoplastic infantile gangliogliomas. Five patients received MAPKi as first line, 7 following other chemotherapy lines. Median follow-up was 4.1 years (range 2.5–8.7 years). Tumor response was associated with contrast enhancement (CE): 9 out of 10 patients with CE at treatment onset had at least partial response and subsequent CE resolution, while both 2 out of 2 patients without CE showed stable disease. A 4-year old contrast enhancing-ganglioglioma who reached partial response and CE resolution with MAPKi, presented disease progression four days after treatment withdrawal; treatment re-start determined tumor and CE reduction after only 7 days.

CONCLUSIONS

We hypothesize that brain-blood barrier breakage is induced by tumor infiltration of bloodstream immune cells, and that this trafficking is stimulated by tumor cell secreted products and determined by microglial progenitors shift from the bloodstream to the tumor site. MAPKi treatment may incite blood-brain barrier reconstitution as it reduces the trafficking between tumor site and bloodstream.

ACKNOWLEDGEMENT

This work was supported by grant number NET-2018-12366666 NeuroArtP3 from the Italian Ministry of Health.
IMMU-08. OUTCOME OF PATIENTS WITH RECURRENT MEDULLOBLASTOMA AND EPENDYMOMA TREATED WITH PEMBROLIZUMAB, AN IMMUNE CHECKPOINT INHIBITOR: A PEDIATRIC BRAIN TUMOR CONSORTIUM STUDY (PBTC045)
Authors: Hwang Eugene I , Kilburn Lindsay B , Mitchell Duane A , Lin Tong , Young-Poussaint Tina , Robinson Giles , Gajjar Amar , Lenzen Alicia , Dorris Kathleen , Robison Nathan , Fangusaro Jason R , Fouladi Maryam , Onar-Thomas Arzu , Dunkel Ira J
Published: June 2024

BACKGROUND

Children with recurrent medulloblastoma and ependymoma typically have a dismal prognosis. Immune checkpoint blockade has revolutionized treatment of some resistant cancers. PBTC045 is a safety and preliminary efficacy study of pembrolizumab, a PD-1 inhibitor, in children with recurrent/progressive brain tumors. Here we present the strata that included children with recurrent/progressive ependymoma and medulloblastoma.

METHODS

Eligibility included patients aged 1-21 years old with recurrent/progressive ependymoma or medulloblastoma and with functional scores >70, no greater than physiologic steroid usage and standard washout periods, among other eligibility criteria. Pembrolizumab was administered at 2mg/kg IV every three weeks. Tumor tissue (if available) and serum were collected for correlative studies. Primary endpoints included toxicity and response, and two stages were planned requiring objective responses for potential expansion.

RESULTS

Patients with progressive ependymoma (Stratum D, n=13) or medulloblastoma (Stratum E, n=14, one ineligible) were enrolled. The median age at diagnosis was 3.37 years (range, 1-12.7) and 7 years (range, 2.2-13.1), respectively. The median age at study entry was 8.5 and 11.4 years, respectively. There were no first-stage objective responses in either stratum, and thus the expansion arms were not initiated. Grade 3 or greater treatment-related adverse events included rash (n=1), anemia (n=1) and neutropenia (n=2), with no dose-limiting toxicities. The median progression-free survival (PFS) for ependymoma and medulloblastoma were 1.38 months (range, 1.08-1.51) and 1.41 months (range, 1.22-3.45), respectively. Immune correlative analyses are ongoing.

CONCLUSIONS

Immune checkpoint inhibition holds potential for CNS cancer treatment, and as a single agent, is well tolerated. However, in the current study, checkpoint inhibition monotherapy does not appear to significantly prolong survival or induce radiographic responses in children with recurrent/progressive ependymoma or medulloblastoma. Potential incorporation of checkpoint inhibitors into treatment for these patients will likely require combinatorial approaches that may be informed by the correlative science.
IMMU-12. STANDARD OF CARE PLUS INDIVIDUALIZED MULTIMODAL IMMUNOTHERAPY (IMI) TO TREAT H3.3G34 DIFFUSE MIDLINE GLIOMA
Authors: Van Gool Stefaan W , Kosmal Jennifer , Van de Vliet Peter , Stuecker Wilfried
Published: June 2024

BACKGROUND

The prognosis of patients with H3.3G34 diffuse midline glioma is uniformly dismal. Since approval of IO-Vac® as advanced therapy medicinal product (27/05/2015), we treated two young patients with IMI in connection to the standard of care.

METHODS

BN (male 14y, diagnosis 01/2022) and JV (female 21y, diagnosis 12/2021) received partial resection resp. biopsy. Both underwent standard radiochemotherapy.

RESULTS

BN received 3/6 TMZ/Lomustin maintenance chemotherapy before start IMI. JV started with 1/12 TMZ courses together with IMI. Five-day immunogenic cell death (ICD) immunotherapy (Newcastle Disease Virus bolus injections and local modulated electrohyperthermia) were added to each maintenance chemotherapy block. After maintenance chemotherapy plus ICD immunotherapy, both received active-specific immunotherapy with two IO-Vac® vaccinations (autologous mature dendritic cells loaded with ICD-induced antigenic extracellular microvesicles). Both started with modulatory immunotherapy (4x ipilimumab/nivolumab q3w and further 6x nivolumab q4w) in combination with maintenance ICD immunotherapy. BN had a spinal relapse 19 months after initial diagnosis. He restarted with local radiotherapy and thereafter Lomustin plus Nivolumab, ultimately stopped due to arthritis. He died 24 months after diagnosis. Because of the observation of spreading disease, JV is now further treated with maintenance ICD immunotherapy using local modulated electrohyperthermia to the brain and to the upper and lower spine. She shows no evidence of progressive disease after >25 months.

CONCLUSIONS

The addition of IMI to standard of care for young patients with H3.3G34 diffuse midline glioma might give a glimpse of hope, and further anecdotal experiences should be collected. Additional treatment of the spinal axis with modulated electrohyperthermia might be required for patients with DMG.
IMMU-15. CARTART: A SURFACE TARGET IDENTIFICATION TOOL FOR TUMORS
Authors: Joshi Nikhil , Murugesan Rakesh , Beaubien Ezra , McManus Olivia , Wilson Cullen , Harvey Kyra , Mishra Deepak , Hajeebu Sreehita , Madsen Peter , Foster Jessica
Published: June 2024

BACKGROUND

Cell surface proteins are valuable for generation of targeted and immune-based cancer therapies. While large molecular datasets are available for multiple central nervous system (CNS) tumors, identifying such targets on a tumor-level scale to generate novel therapeutics for patients is limited by a lack of analytical pipelines. Here, we present CARTarT (CAR-T Target identification Tool), a no-code, web application that utilizes user-inputted bulk transcriptomic data to identify putative surface targets for pediatric tumors.

METHODS

CARTarT was built on R 4.3.1 and performs differential gene expression between tumors and normal tissue (GTEX) utilizing an empirical bayes method. Data is then filtered based on predicted-surfaceome expression, non-immune cell expression, and limited normal tissue expression to mitigate possible off-target toxicities. Targets are finally scored using a weighted scoring metric based on RNA-level log fold change, t-value, average tumoral expression, and prevalence in oncogene databases to prioritize putative targets. Targets with a score less than 0.20 were removed from our final table. A total of 919 samples from OpenPedCan were utilized to validate the tool.

RESULTS

Amongst diffuse midline glioma specimens (n=196), we identified 100 putative surface targets. 60 (60%) of surface targets were previously identified oncogenic or cancer-associated genes. 17 surface targets (15%) are shown to have previously described immune or targeted therapeutics across cancer types, most notably identifying B7-H3, IL13RA2, EGFR, and GPC2. In addition, we identified 45 targets with potential across multiple pediatric neuro-oncologic malignancies (high grade glioma, medulloblastoma, ependymoma, atypical teratoid/rhabdoid tumor) including CHRNA5, GLP1R, B7-H3 and GPC2.

CONCLUSION

These findings highlight the potential utility of CARTarT as a no-code solution for surface target identification and describe established and novel surface targets across numerous pediatric CNS tumors. We present CARTarT to the scientific community as an open-access opportunity to advance immune-based and targeted therapies for tumors.
IMMU-17. A PHASE I STUDY OF INTRATUMORAL/PERITUMORAL HERPES SIMPLEX VIRUS-1 MUTANT HSV1716 IN PATIENTS WITH REFRACTORY OF RECURRENT HIGH-GRADE GLIOMAS: A PEDIATRIC BRAIN TUMOR CONSORTIUM STUDY
Authors: Mochizuki Aaron Y , Hummel Trent R , Cripe Timothy , Fouladi Maryam , Stevenson Charles B , Pollack Ian , Mitchell Duane , Poussaint Tina Young , Onar-Thomas Arzu , DeWire-Schottmiller Mariko , Pillay-Smiley Natasha
Published: June 2024

BACKGROUND

Immune-modulatory strategies, including checkpoint inhibition and tumor vaccines, have been tested in efforts to mitigate the pro-tumor microenvironment in pediatric high-grade glioma (pHGG). HSV1716 is a first-generation oncolytic virus that was previously reported safe with evidence of response in pediatric patients with relapsed or refractory extracranial tumors and in adults with high-grade glioma.

METHODS

PBTC-037 was a multicenter, phase I trial developed and performed by the Pediatric Brain Tumor Consortium (PBTC) to estimate the maximum tolerated dose or recommended phase II dose of HSV1716 administered during surgical resection. Patients aged 12 to 21 years with recurrent or refractory pHGG for whom surgical resection was clinically indicated were eligible. After maximal tumor resection, patients received one intraoperative dose of HSV1716.

RESULTS

Two patients were enrolled; one was later deemed ineligible (due to out-of-window screening evaluations) yet was continued in follow up for safety. Shortly after enrollment of the 2 patients, the study was closed to accrual due to a change in the sponsor’s investment focus. One patient completed the 8-week reporting period without toxicities. The only grade 3 or higher adverse event noted was grade 3 hyperglycemia at 2- and 3-months post injection. The second patient that was later deemed ineligible received the injection of HSV1716 and had no evidence of dose-limiting toxicity. The two patients had progressive disease 1.9 and 2.9 months after enrollment; both eventually died due to progressive disease at 7.5 months.

CONCLUSIONS

We describe the administration of HSV1716 to two pediatric patients with recurrent high-grade glioma, without evidence of dose-limiting toxicity. Oncolytic viruses are currently being tested in pediatric patients in larger trials and in combinatorial trials in other tumor types. Despite the limited numbers, the data presented here will hopefully provide incremental steps toward improved immunovirotherapy of pediatric brain tumors.
IMMU-18. ENHANCING GD2.CAR T CELL THERAPY FOR DIFFUSE MIDLINE GLIOMA WITH LSD1 AND HDAC INHIBITORS
Authors: Murdaugh Rebecca L , Shekar Meghan , Eberl Brittany R , Tremblay Jack R , Richard Rosemary U , Nguyen Linh , Omer Bilal , Anastas Jamie N
Published: June 2024

BACKGROUND

Chimeric antigen receptor T cells against the glycolipid GD2 (GD2.CARTs) have shown promise against Diffuse Midline Glioma (DMG) in clinical trials but are not yet curative. Previous studies in neuroblastoma demonstrate that histone deacetylase inhibitor (HDACi) treatment can increase GD2 on tumor cells and improve targeting by GD2.CARTs. Our lab previously found that simultaneous HDACi and lysine-demethylase 1 inhibitor (LSD1i) treatment in DMG cells causes synergistic alterations in gene expression and reduces DMG growth. Here, we find that treating GD2-low DMG cell lines with combinations of LSD1i and HDACi improves DMG response to GD2.CARTs.

METHODS

Surface expression of GD2 before and after LSD1i/HDACi treatment were analyzed using immunofluorescence microscopy and flow cytometry. The cytotoxicity of GD2.CARTs against DMG cells was determined from co-culture experiments and in patient-derived orthotopic xenograft models using flow cytometry and bioluminescent imaging.

RESULTS

Since low target antigen expression is one mechanism by which tumor cells can escape CAR T cell therapy, we profiled GD2 expression on 9 different H3K27M-mutant DMG cell lines. This analysis shows that only 5 of the 9 cell lines exhibit high GD2 expression while the remaining 4 lines have low GD2 expression. When treating these cell lines with GD2.CARTs, we find that low GD2 expression on DMG cells correlates with tumor cell escape and resistance to GD2.CARTs. Treating GD2-low DMG cells with LSD1i+HDACi increases GD2 expression and enhances tumor cell targeting by GD2.CARTs in subsequent co-culture assays. Further studies in mice bearing GD2-low DMG tumors were initially GD2.CART-insensitive but showed reduced tumor growth when pre-treated with LSD1i+HDACi before intravenous GD2.CART infusion.

CONCLUSIONS

These studies suggest that variable GD2 expression is a major driver of DMG resistance to GD2.CARTs and that LSD1i+HDACi pre-treatment may improve DMG patient responses to GD2.CART therapy by increasing target antigen expression.
IMMU-19. COMBINATION IMMUNOTHERAPY SEQUENCE MATTERS: VACCINE PRIOR TO ONCOLYTIC HSV VIROTHERAPY ENHANCES TUMOR-SPECIFIC T CELL RESPONSES AND EFFICACY
Authors: Kang Kyung-Don , Totsch Stacie K , Ishizuka Andrew S , Gary Sam E , Rocco Abbey , Fan Aaron , Zhou Li , Valdes Pablo A , Lee SeungHo , Li Jason , Peruzzotti-Jametti Luca , Blitz Sarah , Garliss Christopher M , Johnston James M , Markert James M , Lynn Geoffrey M , Bernstock Joshua D , Friedman Gregory K
Published: June 2024

BACKGROUND

Safety and preliminary efficacy have been demonstrated with intratumoral oncolytic, engineered HSV immunotherapy; however, few responses have been durable, suggesting that augmented, prolonged anti-tumor T cell responses are likely required to maintain tumor remission. We hypothesized that combining the direct oncolytic effect and innate immune stimulus of oHSV with a vaccine that fosters T cell mediated immunity would lead to more prolonged tumor responses.

METHODS

We examined the preclinical efficacy of combining intratumoral oHSV with an intravenous (via tail vein) self-assembling nanoparticle vaccine co-delivering peptide antigen to E7 and Toll-like receptor-7 and -8 agonists (TLR-7/8a), termed ‘SNAPvax™’, compared to either therapy alone or control in a TC-1 E7-expressing tumor model in immunocompetent mice. We also assessed how SNAPvax™ timing (before or after oHSV) affected efficacy, viral replication by viral recovery assay, and T cell activation and responses via intracellular cytokine staining of CD8+ T cells in the blood and tetramer staining.

RESULTS

The oHSV-vaccine combination prolonged survival compared to control or either agent alone. Critically, survival was significantly enhanced when SNAPvax was given before oHSV compared to after oHSV. Increased effectiveness was associated with reduced tumor volume, increased tumor antigen specific CD8+ T cells, and amplified viral recovery.

CONCLUSIONS

These results demonstrate the criticalness of combination immunotherapy timing with improved efficacy seen when vaccine was given prior to oHSV, which was mediated by tumor specific CD8+ T cells and increased viral replication. Our data provide preclinical support for translation of this novel combination therapy to clinical trial.
IMMU-20. INNATE IMMUNE EVASION IN MYC-AMPLIFIED MEDULLOBLASTOMA
Authors: Vo Jeremy , Mitra Juni S , Knox Aaron , Picard Daniel , Vibhakar Rajeev , Hankinson Todd , Mitra Siddhartha S
Published: June 2024

BACKGROUND

While major advances have been made in improving the quality of life and survival of children with most forms of medulloblastoma (MB), those with MYC-driven tumors (Grp3-MB) still suffer significant morbidity and mortality. Here, we report a cell surface proteome analysis of Group3-MB cell lines after direct MYC inhibition to identify changes in surface proteins and sensitivity to macrophage-mediated phagocytosis.

METHODS

We had previously demonstrated the preferential activity of HDACi (CI994) in MYC-driven medulloblastoma. CI-994, showed significant cell viability reduction mediated by reduction in the MYC (mRNA and protein), induction of apoptosis in MYC-driven medulloblastoma. In this study, we directly inhibited MYC using MYCi975 and OMO-MYC and carried out a cell surface proteomic analysis on Group3-MB cell lines to reveal CD24 and CD59 as potential immune evasion markers. While CD24 is a potential don’t eat me signal, CD59 is a ubiquitously expressed cell-surface glycosylphosphatidylinositol-anchored protein that acts as an inhibitor to the membrane attack complex and protects cells from CDC. In certain tumors, CD59 expression is enhanced, posing a significant obstacle to treatment by hindering effective monoclonal antibody-induced CDC. We use inhibitors to CD24 and CD59 to confirm their role as innate immune evasion proteins in Group 3MB.

RESULTS

Meta-analysis of published datasets reveals CD24 and CD59 as strong prognostic indicators in Group3-MB as well as within the Group3g-subtype. Inhibition of MYC reduces surface levels of CD24, increasing macrophage-mediated phagocytosis. The use of a blocking anti-CD24 mAb significantly enhanced macrophage-mediated phagocytosis. Furthermore, a significant reduction in surface expression was observed in CD59. Blocking CD59 mAb significantly enhanced anti-CD47 mAb mediated phagocytosis. Combined treatment of anti-CD24 and anti-CD47 significantly enhanced the survival of Grp3-MB tumor-bearing mice.
IMMU-22. B7-H3 NANOBODY CAR-T AND SOLUBLE TREM2 GENETICALLY ENGINEERED MYELOID CELL THERAPY IN MURINE SYNGENEIC GLIOBLASTOMA
Authors: Cronk James C , Meskini Rajaa El , Fanuzzi Mia , Atkinson Devon , Householder Debbie , Puebla Mariela , Bassel Laura , Ball Brendan , Montalvan Emily San Andres , Li Dan , Kaczanowska Sabina , Ho Mitchell , Kaplan Rosandra N , Ohler Zoe Weaver , Nellan Anandani
Published: June 2024

BACKGROUND

Myeloid immunosuppression can be a major impediment to CAR-T cell therapy for CNS tumors. Importantly, CAR-T cells are often evaluated in immunocompromised mice which cannot accurately recapitulate the tumor immune response or tumor microenvironment. CNS tumor macrophages express TREM2, an important driver of immunosuppression. This study combines B7-H3 targeting nanobody CAR-T cells which are cross reactive in humans and mice (currently being evaluated for clinical development) with genetically engineered myeloid cells (GEMys) expressing soluble TREM2 (sTREM2) in a syngeneic mouse model of glioblastoma (GBM), with the aim of blocking TREM2-mediated immunosuppression to enhance CAR-T cell function.

METHODS

Syngeneic murine GBM, designed to mimic human GBM and generated at the Center for Advanced Preclinical Research (CAPR), was used for all studies. B7-H3 nanobody CAR-T cells were generated from mouse splenic T cells. In vitro tumor killing assays were performed by xCELLigence. sTREM2 GEMys were generated from bone marrow progenitor cells using lentiviral transduction. For in vivo studies, mice underwent orthotopic implantation of tumors and placement of an MRI-compatible, permanent catheter-port system for serial intracerebroventricular (ICV) administration of cell therapies. Mice were treated with CAR-T and/or GEMy therapies, evaluated weekly for tumor burden by MRI, and were monitored for survival.

RESULTS

Syngeneic GBM expression of B7-H3 was confirmed by flow cytometry, immunofluorescence, and western blot. B7-H3 nanobody CAR-T cells demonstrated effective killing of GBM by xCELLigence. sTREM2 GEMys were successfully generated and confirmed to produce sTREM2. Cell therapies were successfully infused ICV via the implanted catheter-port system, demonstrating safety and feasibility of this model for serial ICV cellular therapy.

CONCLUSIONS

B7-H3 nanobody CAR-T cells were validated against syngeneic GBM, and we have demonstrated safety and feasibility of ICV catheter administration of cellular therapies in vivo. Future studies will continue to evaluate in vivo timing and efficacy of CAR-T and GEMy therapy.
LGG-02. ELUCIDATING THE ROLE OF FGFR1 ALTERATIONS IN PEDIATRIC GLIOMAS
Authors: Apfelbaum April A , Morin Eric , Bahadur Sher , Sturm Dominik , Novikov Dana , DiGiacomo Jeromy , Cameron Amy , Rechter Patrick , Cusick Margaret M , Oh Sehee , Jeon Hyesung , Vogelzang Jayne , Jones Jacquelyn , Bossi Connor , De Nguyen Quang- , Jones David T W , Eck Michael J , Fischer Eric S , Ligon Keith L , Bandopadhayay Pratiti
Published: June 2024

BACKGROUND

Pediatric brain cancers are the leading cause of cancer-related deaths in children. We (and others) have recently found that close to 10% of all pediatric gliomas, encompassing low-grade gliomas (LGGs) and high-grade gliomas (HGGs), harbor recurrent driver alterations in FGFR proteins, most frequently FGFR1, the gene encoding Fibroblast Growth Factor Receptor 1. In pediatric gliomas, FGFR1 alterations present as either structural variants (SVs), including kinase duplications and fusion proteins, or kinase-activating single nucleotide variants (SNVs). Recurrent FGFR1 alterations represent a promising therapeutic target for precision medicine approaches, however a challenge has been the lack of clinical trials for FGFR inhibitors. A major goal of this project is to identify preclinical FGFR inhibitor candidates for FGFR1-altered pediatric gliomas.

METHODS

We have generated isogenic mouse and human neural stem cell (NSC) models driven by FGFR1 and BRAF alterations commonly seen in pediatric gliomas to test the oncogenic properties and therapeutic capacities of these alterations.

RESULTS

We found that NSC lines grow independent of growth factors and form tumors in mice. RNA-sequencing of these lines revealed the FGFR1-altered lines are enriched in neuronal gene programs. The FGFR1-altered models are exquisitely sensitive to the four FDA-approved panFGFR inhibitors Infigratinib, Erdafitinib, Pemigatinib, and Futibatinib. However, the FGFR1 SNV + PTPN11 co-occurring SNV line is the least sensitive to FGFR inhibition, which suggests combination therapies may be needed. Combination drug studies with FGFR inhibition in our FGFR1-altered lines reveal the best synergy with mTOR inhibition. Finally, we present examples of case studies of patients with FGFR1-altered tumors treated with targeted inhibitors.

CONCLUSIONS

Taken together, our studies have established models that have generated key insights into the biology of FGFR1-altered gliomas and how to best target them therapeutically.
LGG-03. PREDICTIVE VALUE OF ACQUIRED NYSTAGMUS FOR PEDIATRIC BRAIN TUMOR ASSOCIATED VISUAL IMPAIRMENT: A RETROSPECTIVE STUDY
Authors: Teeuwen Sophie , Oostenbrink Rianne , Porro Giorgio , Meijer Lisethe
Published: June 2024

BACKGROUND

Visual impairment (VI), defined as visual acuity (VA) loss or visual field (VF) defects, is common in pediatric brain tumors of the optic pathway and may impact the quality of life. VI is a challenge to establish, especially in young children. However, pediatric brain tumor patients might concurrently have acquired nystagmus (AN), which can easily be observed. The aim of this study was to investigate whether AN is predictive of VI in pediatric brain tumor patients. If correlated, AN could be an early warning sign for brain tumor related VI, warranting MRI scanning to prevent further visual deterioration, thus decreasing morbidity and mortality.

METHODS

Data on tumor characteristics, VA (in LogMAR), VF, (type of) AN and other ophthalmic investigations were collected from the medical records of pediatric brain tumor patients in the Máxima Pediatric Brain Tumor Ophthalmology cohort (MP-BT-O cohort). These characteristics between children with (nystagmus group) and without (control group) AN were compared to determine the predictors of VI.

RESULTS

The MP-BT-O cohort consists of 389 children (≤18y) with a brain tumor who had visual assessment, 95 children had AN (24.4%). The mean best corrected visual acuity (BCVA) was 0.10 LogMAR [CI 0.06-0.14] in the control and 0.50 LogMAR [CI 0.35-0.66] in the nystagmus group (p<0.001). Nystagmus type was found to be a significant predictor of VI (p<0.001). Specifically horizontal AN (a decrease in BCVA of 0.75 LogMAR, p<0.001) and mixed AN (a decrease in BCVA of 0.61 LogMAR, p<0.001) were independent predictors of VI, corrected for tumor location (p=0.04) and age at diagnosis (an increase in BCVA of -0.02 LogMAR per year, p<0.001).

CONCLUSIONS

Acquired nystagmus, especially horizontal and mixed nystagmus, is an independent predictor of VI in pediatric brain tumor patients and should be interpreted as a warning sign for the presence of VI.
LGG-12. INTEGRATED CLINICAL AND MOLECULAR CHARACTERIZATION OF 200 DISSEMINATED PEDIATRIC LOW-GRADE GLIOMAS
Authors: Levine Adrian , Bennett Julie , Li Cyril , Rana Mansuba , Yuditskiy Richard , Ho I-Chen , Haizel-Cobbina Joseline , Hansford Jordan , Luck Amanda , Ludlow Louise , Eisenstat David , Toledano Helen , Masoud Roaya , Fukuoka Kohei , Yamasaki Kai , Nakano Yoshiko , Mushtaq Naureen , Minhas Khurram , Bukhari Syed Ibrahim , Stuecklin Ana Guerreiro , Weiser Annette , Jadrijevic-Cvilje Filip , Fleming Adam , Campbell Shawde , Cacciotti Chantel , Erker Craig , van Landeghem Frank , Wilson Bev , Black Karina , MacNeil Mary , Cheng Sylvia , Dunham Chris , Larouche Valerie , Giannakouros Panagiota , Fonseca Adriana , Williamson Lane , Plant-Fox Ashley , Levy Jean Mulcahy , DeMarsh Samantha , Vega José Velázquez , Patil Prabhumallikarjun , Nasrallah MacLean , Santi-Vicini Mariarita , Nelson Ernest , Graham Richard , Raskin Scott , Fernandes Igor , Dewan Michael , Tabori Uri , Hawkins Cynthia
Published: June 2024

Pediatric low-grade gliomas (PLGG) have excellent outcomes overall but are a major clinical challenge when disseminated. Diffuse leptomeningeal glioneuronal tumor (DLGNT) is a recognised entity both clinically and pathologically, however many disseminated LGG (DLGG) fall outside this diagnosis. To better understand the clinical and molecular features of DLGG as well as risk factors for dissemination, we assembled an international consortium of 30 sites, contributing over 200 patients with clinical annotation, along with genomic and methylation profiling. DLGG have worse progression-free (PFS) and overall survival (OS) than PLGG overall (p<0.0001). Seventy (35%) presented with a localized mass and secondary dissemination, including some with initial gross-total resection. The most common growth pattern observed (n=77, 40%) is a dominant suprasellar/optic pathway tumor with leptomeningeal drop-metastases involving the brainstem and spinal cord. Only 27 (14%) patients had diffuse tumors (without an identifiable dominant mass), and these had significantly worse OS (p=0.03). The most common pathologic diagnosis was pilocytic/pilomyxoid astrocytoma (n=92; 53%). DLGNT comprised a minority of cases (n=23, 14%), with a trend (p=0.056) towards worse survival compared to other diagnoses. The most frequent molecular alteration was BRAF fusion (78/151 with molecular testing; 52%), followed by FGFR mutations or fusions (18/151; 12%). BRAF V600E was underrepresented (14/151; 9%). 1p deletion was rare (17 patients) but highly associated with DLGNT. Methylation classification (n=70) was highly concordant with histologic diagnoses rather than clinical behavior. Importantly, patients who received upfront targeted therapies (TT; BRAF and/or MEK inhibition, n=9) had better PFS compared to those receiving chemotherapy (n=146, p=0.05). Furthermore, patients who were treated sequentially with chemo then TT had longer PFS on TT (p=0.011). This study presents the largest cohort of DLGG to date, expanding our understanding of the clinical, pathologic, and molecular features of this disease and supports the use of upfront targeted therapy.
LGG-13. UNRAVELING THE SPATIAL TUMOR MICROENVIRONMENT OF PEDIATRIC LOW-GRADE GLIOMAS USING IMAGING MASS CYTOMETRY
Authors: Faria Andrade* Augusto , Sigaud* Romain , Puligandla* Evan , Liu Bridget , Karimi Elham , Schmid Simone , Selt Florian , Driever Pablo Hernáiz , Koch Arend , Sahm Felix , Sievers Philipp , Pfister Stefan M , Witt Olaf , Jones David T W , Capper David , Walsh* Logan , Jabado* Nada , Milde* Till
Published: June 2024

Pediatric low-grade gliomas (pLGG) are the most common brain tumors in children and are associated with significant morbidity. Therefore, there is an urgent need for novel therapeutic strategies. While some studies have described pLGG’s tumor microenvironment (TME) from bulk RNAseq and scRNAseq, little is known about the spatial architecture of pLGG and its association with clinico-molecular features. Our study utilized imaging mass cytometry and a panel of 35 metal-labelled antibodies to unravel the spatial organization of key TME cell populations in 120 primary pLGG samples from the LOGGIC Core BioClinical DataBank. Cellular neighborhood analysis was performed to map the spatial organization of pLGG TME. Several clinic-molecular features (entity, tumor location, genetic driver alteration, disease progression status, age and sex) were used to measure their putative association with the enrichment of key cell populations and cellular structures to identify diagnosis and prognosis markers. Here, we identified a predominant presence of myeloid cells in the TME, particularly notable in optic pathway tumors, which exhibited unique immune profiles. Optic pathway tumors demonstrated elevated immune subsets, delineating distinct architectural features in the TME of this brain region. Spatial analysis defined cellular neighborhoods and specific interactions thereof, including myeloid interaction and macrophage-abundant regions. Clinically, these myeloid cell populations, associated with an increased expression of the immune checkpoint protein TIM3, suggesting the presence of an immuno-suppressive environment, were associated with inferior survival outcomes. Importantly, we identified an immunophenotype signature based on the presence of 4 myeloid cell populations significantly associated with progression free survival in our cohort. Our study underscored the need for accurate identification of immune cell populations influencing tumor progression, offering valuable insights for the identification of prognostic markers, and for the development of effective therapeutic strategies, such as immune checkpoint inhibitors, for the treatment of pLGG.