Primary Brain Tumors Research Articles

CSIG-04. ANTI-TUMOR RESPONSE OF ONCOMAGNETIC MONOTHERAPY IN GLIOBLASTOMA

Abstract BACKGROUND Glioblastoma (GBM) is the most lethal primary malignant brain tumor with a median survival of 15–20 months. Concurrent temozolomide (TMZ) chemotherapy and radiation (XRT) remain the current standard of care (SOC) treatment for newly diagnosed GBM. The addition of tumor treating fields (TTFs) improves median survival for newly diagnosed GBM from 16 to 20.9 months. This modest improvement underscores the urgent need to identify a new treatment modality as a safe and effective therapy. PURPOSE The noninvasive Oncomagnetic device developed in our laboratory selectively kills glioblastoma (GBM) in vitro. We studied the cellular and molecular effects of Oncomagnetic monotherapy (OMT) on GBM cell lines and investigated immune response in a syngeneic mouse model. RESULTS OMT significantly reduces cell proliferation and cell survival in vitro. OMT induces persistent ROS primarily by increasing superoxide level in cancer cells and reduces mitochondrial-membrane potential in GBM cells. It also induces DNA damage and arrests cells in G1-phase of the cell cycle. Whole-body Oncomagnetic stimulation caused a substantial retardation of tumor growth and reduction of the contrast-enhanced tumor volume in 9.4T MRI scans. OMT showed significant increase in overall survival in treated mice. We also observed upregulated immune response indicated by RNA sequencing data obtained from OMT-treated GBM cells as well as in treated GBM mouse tumor sections by imaging mass cytometry analysis. The tSNE analysis of various immune clusters suggests significant increase in immune response by activating CD4+, CD8+, murine-macrophages and M1-macrophages located at tumor site in the treated group. CONCLUSION The obtained data indicate significant anti-tumor response by inhibiting cancer signaling pathways and an increased immune response. Our findings suggest unique mechanism of action for OMT stimulation and provide a strong rationale for standalone OMT for GBM.

CNSC-47. SENOLYTICS ERADICATE SENESCENT MICROGLIA IN THE BRAIN PARENCHYMA AND IMPROVE SURVIVAL IN OLDER ADULT MICE WITH GLIOBLASTOMA

Abstract BACKGROUND Glioblastoma (GBM) is the most common aggressive primary malignant brain tumor in adults with a poor median survival rate. Despite the aggressive standard of care treatment combining surgical resection, chemo-, and radio-therapy, the median overall survival (OS) is only ~15-18 months. Progressively increasing subject age is inversely associated with GBM patient OS such that older adults tend to have significantly worse survival outcomes compared to younger counterparts. Senescent cells accumulate in the body during progressive aging and contribute to worse outcomes in older adult mice with GBM. Senolytics are pharmacologics that cause senescent cells to undergo cell death. OBJECTIVE To comprehensively profile the treatment effect of senolytics combined with or without immunotherapy in mice with GBM across the lifespan. METHODS Young 7-9- and older adult 97-104-week-old wild-type (WT; C57BL/6) and 110-130-week-old INK-ATTAC mice with or without intracranial SB28 cells were treated with or without brain radiation (RT), PD-1 mAb, and an IDO enzyme inhibitor with the senolytics, dasatinib + quercetin, or the AP compound that induces p16INK4A+ senescent cell death in INK-ATTAC mice (n=5/group). The quantification of beta-galactosidase positive cells by flow cytometry was performed on brain-resident neurons, astrocytes, oligodendrocytes, microglia, as well as dendritic cells, macrophages, neutrophils, T cells in the tumor and non-tumor bulk mass. Overall survival was also evaluated. RESULTS Senolytics or AP compound treatment both decrease beta-galactosidase positive microglia in the older adult brain with GBM (p<0.05). Combining radio- and immuno-therapy with senolytics improves overall survival of older adult mice with intracranial GBM (p<0.05). CONCLUSIONS Our ongoing work aims to understand how senescent microglia affect neuronal health and function in the older adult brain with GBM. KEYWORDS Glioma, senescence, senolytic.

STEM-12. A NEURONAL STEM-LIKE PHENOTYPE IN GRADE 4 IDH-MUTANT ASTROCYTOMA WITH CDKN2A/B LOSS IS ASSOCIATED WITH CUX2 DEFICIENCY

Abstract Diffuse gliomas represent the most common type of primary adult malignant brain tumor historically diagnosed and graded from histologic criteria alone. Gliomas harboring isocitrate dehydrogenase (IDH) 1 or 2 mutations are associated with lower grade tumors and portend a favorable prognosis relative to IDH-wildtype glioma. However, the loss of CDKN2A/B in IDH-mutant astrocytoma confers an aggressive high grade phenotype and is the strongest implicated molecular alteration associated poor clinical survival, thus is now sufficient to define a grade 4 tumor regardless of histologic grade. However, there remains no effective therapies targeted at molecular subgroups in aggressive gliomas to date. Here, we sought to elucidate the biologic pathways and functional outcomes associated with the acquisition of high-grade behavior under loss of CDKN2A/B in IDH-mutant astrocytoma to inform future therapeutic strategies. We analyzed a cohort of patient IDH-mutant astrocytomas with RNA sequencing data and found the increased expression of regulators of embryonic nervous system development and signaling concurrent with CDKN2A/B loss. Using grade 4 IDH-mutant astrocytoma patient-derived (PDX) and cell-lines harboring CDKN2A/B homozygous deletion, we stably re-expressed p14ARF, p15INK4B, and p16INK4A using a Tet-inducible system. IDH-mutant cell lines with re-expression of p14, p15, or p16 displayed differential transcription factor activation, impaired neurosphere capability, decreased colony formation, and lower neurosphere proliferation. Intriguingly, RNA-seq data revealed CUX2, a transcription factor known to control neuronal precursor behavior, as the likely candidate regulating the differential expression profile across CDKN2A/B status. We observed increased CUX2 expression in cell lines stably re-expressing p14, p15, and p16. We validated the CUX2 signature across publicly available datasets of IDH-mutant astrocytoma where CUX2 expression negatively correlated with loss of CDKN2A/B in patient tumors. Together our work suggests CUX2 deficiency in IDH-mutant astrocytoma with CDKN2A/B deletion enables an increased neuronal stem-like phenotype in these grade 4 tumors.

TMIC-60. BRATS-PATH: ASSESSING HETEROGENEOUS HISTOPATHOLOGIC REGIONS IN GLIOBLASTOMA

Abstract Glioblastoma, the most common malignant primary adult brain tumor, poses significant diagnostic and treatment challenges due to its heterogeneous molecular and micro-environmental profiles. To this end, we organize the BraTS-Path challenge to provide a public benchmarking environment and a comprehensive dataset to develop and validate AI models for identifying distinct histopathologic glioblastoma sub-regions in H&E-stained digitized tissue sections. We identified 188 multi-institutional diagnostic slides of glioblastoma (IDH-wt, Gr.4) cases, from the TCGA-GBM and TCGA-LGG data collections, following their reclassification according to the 2021 WHO classification criteria. Sub-regions were selected according to distinctive morphology of histopathologic features and included aggressive tumor biology and areas consistent with potential treatment effect. Selected sub-region annotations included cellular tumor, geographic necrosis, cortical infiltration, pseudopalisading necrosis, microvascular proliferation, white matter penetration, regions dense with macrophages, leptomeningeal infiltration, and presence of lymphocytes. We obtained 107,340 patches of size 512x512 from the 9 sub-regions. A global network of board-certified expert neuropathologists defined and followed a systematic annotation protocol based on clinical definitions and only delineated sub-regions with high confidence, thus ensuring high-quality standardized data. Each tissue section was assigned to an annotator-approver pair, with the annotator delineating sub-regions and the approver ensuring the consistency of the annotations. By crowdsourcing annotations, the BraTS-Path challenge harnesses the collective expertise of clinical neuropathologists and fosters a collaborative environment to advance the neuro-oncology field. The anticipated developed algorithms are expected to integrate state-of-the-art computational methods, achieving high accuracy in identifying diverse histopathologic features and advancing clinical decision-making processes. The BraTS-Path challenge aims to bridge the gap between research and clinical practice by promoting the development of AI-driven tools for precise tumor characterization. This collaborative effort can significantly enhance our understanding of glioblastoma, improve diagnostic accuracy, and inform treatment strategies, thereby contributing to better patient outcomes.

BIOM-28. WHOLE EXOME TUMOR MOLECULAR PROFILING FROM CEREBROSPINAL FLUID (CSF): PRELIMINARY RESULTS OF A PILOT STUDY

Abstract BACKGROUND Tissue sampling for molecular profiling has become an integral part of the diagnosis, prognosis, and management of CNS malignancies. However, many tumors are surgically inaccessible, and even biopsy of accessible lesions conveys some risk, and the possibility of sampling error. We evaluated the accuracy and potential utility of CSF liquid biopsy for identifying mutations in patients with intracranial tumors. METHODS CSF samples were collected from ventricular reservoirs and stored at -80 degrees Celsius until analyzed. Cell-free nucleic acids were extracted, concentrated, and quantified. Samples over 110ng quantification were normalized to 110ng and input into library prep. Library prep was done using v3.5 of Caris Assure and whole exome sequencing in an S2 FC on a Novaseq 6000. Bioinformatic analysis was performed. RESULTS CSF samples were obtained from 20 patients (10 gliomas, 5 CNS lymphomas, 5 metastases), 19 of whom also had tumor specimens available. Two hundred eighty-one mutations were identified: 17 (6.6%) in tumor only, 184 (72.4%) in CSF only, and 80 (31.5%) in both. Key alterations found in CSF include: IDH, TERT, ATRX in gliomas, and MYD88, PIM1, BCL2, TERT in lymphomas. Glioma CSF with IDH1 mutations did not have PTEN mutations (with one exception, in which the CSF was collected 3 years after the tissue). Targetable mutations in metastases included PIK3CA, NF1, and BRCA. CONCLUSION These preliminary results suggest that CSF liquid biopsy may be useful for identifying mutations in primary and metastatic brain tumors. Serial sampling is feasible, and may disclose changes in diagnostic and/or driver mutations over time, with important therapeutic and diagnostic implications. Many mutations were found in CSF alone. CSF may capture the entire molecular landscape of the tumor, overcoming the sampling error inherent in tissue biopsies. Prospective studies are underway to further elucidate the clinical applications of this technique.

PATH-06. TRANSLATION INTO CLINICAL PRACTICE OF THE G1-G7 MOLECULAR SUBGROUP CLASSIFICATION OF GLIOBLASTOMA

Abstract Glioblastoma is the most frequent and malignant primary brain neoplasm. Glioblastoma growth is promoted by alterations in mediators from five major pathways: MAPK and PI3K canonical growth pathways, telomere elongation/TERT, cell cycle G1-phase and the p53 pathway. In a recent breakthrough study on a prospective Discovery cohort, I proposed the first all-inclusive molecular classification of glioblastoma into seven subgroups, G1-G7, based on MAPK pathway activation. New data from a subsequent, prospective Validation cohort validated the G1-G7 molecular subgroup classification, showing significant demographic and molecular differences between subgroups. Beside the initial histologic diagnosis, the G1-G7 classification requires next generation sequencing (NGS) of formalin-fixed paraffin-embeded (FFPE) samples and genomic-transcriptomic correlations between DNA mutations, copy number variations (CNVs) and RNA expression. Thus, in the Combined cohort containing tumors from over 220 glioblastoma patients, aproximately 75% of cases fell into three major subgroups, G1/EGFR, G3/NF1 and G7/Other, whereas the rest of 25% cases made up the four minor subgroups, G2/FGFR3, G4/RAF, G5/PDGFRA and G6/Multi-RTK. The name of the mutated most upstream, non-redundant, MAPK pathway effector corresponds to each subgroup, except for the G7/Other subgroup in which MAPK activation is minimal and PI3K pathway activation is dominant. The effectors of the other four pathways may be redundant; however, genomic-transcriptomic correlations showed subgroup specificity, with opposing trends for the G1/EGFR and G7/Other molecular subgroups. This first, all-inclusive, molecular subgroup classification of glioblastoma in a large prospective patient cohort allowed integrated pathway analysis, risk stratification and demographic comparison between Caucasian/White and African-American/Black patients. Most importantly, its implementation into clinical practice opened the avenue to controlled therapeutic approaches.

TMET-07. RADIORESISTANT GLIOBLASTOMA EVADES MITOCHONDRIAL LIPOTOXICITY THROUGH ALTERED DGKB AND DGAT1

Abstract Glioblastoma (GBM) is the most common and aggressive primary brain tumor, with a median survival of only 15 months despite multimodal therapy. Radiotherapy is a conventional therapy of GBM treatment, but the development of radioresistance often leads to tumor recurrence and treatment failure. To elucidate the molecular mechanisms underlying radioresistance in GBM, we established radioresistant GBM cell lines through repeated exposure to ionizing radiation. Transcriptomic analysis revealed that diacylglycerol kinase beta (DGKB), an enzyme that converts diacylglycerol (DAG) to phosphatidic acid, was significantly downregulated in radioresistant GBM cells. Functional studies demonstrated that knockdown of DGKB or expression of a kinase-dead DGKB mutant resulted in DAG accumulation and reduced fatty acid oxidation. Conversely, overexpression of DGKB activated fatty acid oxidation, increased reactive oxygen species (ROS) production, and sensitized GBM cells to radiation. Interestingly, we found that radiation upregulated the expression of diacylglycerol acyltransferase 1 (DGAT1), which catalyzes the conversion of DAG to triglycerides. Knockdown of DGAT1 using shRNA or miR-3918 mimic reduced lipid droplet formation and enhanced radiosensitivity both in vitro and in vivo. Furthermore, using Connectivity Map, we identified cladribine as a potential radiosensitizing agent that increases DGKB and decreases DGAT1. Cladribine effectively sensitized GBM cells to radiation and significantly prolonged the survival of mice bearing GBM xenografts. In conclusion, our study reveals a novel mechanism by which radioresistant GBM cells maintain lipid homeostasis through downregulation of DGKB and upregulation of DGAT1 to evade lethal mitochondrial lipotoxicity. Targeting the DGKB-DGAT1 axis represents a promising therapeutic strategy to overcome radioresistance and improve the outcomes of GBM patients.

EXTH-25. OPTIMIZATION OF NEW CHEMOTHERAPEUTIC AGENTS BY INTRA-ARTERIAL INFUSION IN GLIOBLASTOMAS

Abstract Being the most aggressive malignant primary brain tumor, glioblastoma (GBM) is a difficult disease to treat. The first line treatment is well established, but most patients will relapse before or during the treatments. The overall survival is only 14,6 months while the progression-free survival is 6,9 months. In Sherbrooke, Dr Fortin prioritize the intra-arterial (IA) administration of chemotherapeutic agents (CTA) as a second line treatment. Unfortunately, certain patients will not respond or will even develop chemoresistance to the agents. Therefore, there is a strong need for bringing more CTAs onto clinical care. The maximal tolerable dosage (MTD) of every agent was first determined. Every CTAs were then administered IA by retrograde infusion in the external carotid but also intravenously (IV) by the caudal vein. We used the Fischer-F98 glioma rat model in our studies. For the efficacy study, we implanted 10 000 F98 cells into their brain. After 10 days, they received the treatment associated to their group. The animals were followed every day and were euthanized when their condition was too deteriorated. The dosages found in the MTD study for topotecan and cytarabine was 4 mg/kg and 8,75 mg/kg respectively while paclitaxel was too toxic. As for the efficacy study, the IA group of topotecan showed a promising outcome with a higher survival rate (29 days) compared to the IV one (23,5 days). As for the cytarabine, the opposite was observed (IA: 22 days, IV: 26,5 days). While topotecan and cytarabine could be given intra-arterially, only topotecan showed conclusive results. More animals will be added to this group to confirm this outcome. Cytarabine is not a good option since the IV group survived a longer time than the IA group. As for the paclitaxel, the intra-tumoral infusion will be tested to see if we can get positive results.

CSIG-30. EXPLORING THE ROLE OF CAPICUA (CIC) IN RESISTANCE MECHANISMS OF MEK INHIBITORS IN GLIOBLASTOMA

Abstract Glioblastoma multiforme (GBM) is the most common and fatal primary brain tumor, resistant to conventional therapy. Despite its heterogeneous nature, a key feature of GBM is aberrant kinase signaling. Specifically, hyperactivation of receptor tyrosine kinases (RTK) and their downstream tumorigenic effectors Ras/MEK/Extracellular Signal Regulated Kinase (ERK) pathway are attributed to the aggressive nature of GBM. Capicua (CIC) is a High Mobility Group (HMG) box transcriptional repressor that directly binds to DNA and counteracts the transcription of genes typically expressed only in response to RTK activation such as oncogenic transcription factors ETV1/4/5. Hyperactive MEK/ERK signaling in GBM causes CIC degradation. The mechanism of CIC’s repressor function is not well understood, however, transcriptional repressors (like CIC) typically form co-repressor complexes to repress target genes. We discovered a novel interaction between CIC and the transcriptional regulator yin yang 1 (YY1), a context-dependent transcription factor that can repress or activate gene expression. We uncovered that 90-kDa ribosome S6 protein kinase (p90RSK), a downstream effector of ERK and a known CIC regulator, mediates the CIC/YY1 interaction. Interestingly, we found re-activation of p90RSK following MEK/ERK inhibition implicating p90RSK in the resistance mechanism of RTK/MEK/ERK inhibition in GBM. We hypothesize that p90RSK inhibition will stabilize the CIC/YY1 co-repressor complex and re-sensitize towards MEK/ERK inhibition. Patient-derived glioma stem-like cells (GSCs) were treated with increasing doses of BI-D1870 or LJI308 (p90RSK inhibitors) with and without selumetinib (MEK inhibitor) and various functional assays were performed to examine the effect of p90RSK inhibition on the CIC/YY1 complex and sensitization to MEK/ERK inhibition. Treatment with BI-D1870 and LJI308 markedly reduced viability and mRNA expression of ETV1/4/5 indicating that p90RSK inhibition may mediate CIC /YY1 DNA binding ability. Importantly, inhibiting p90RSK sensitized GSCs to MEK/ERK inhibition. These results highlight the importance of downstream p90RSK inhibition in stabilizing CIC/YY1 repressor complex function and sensitizing cells to RTK/MEK/ERK inhibition.

NCOG-12. TREATMENT AND MORTALITY OF PRIMARY BRAIN TUMORS: A SINGLE CENTER OBSERVATIONAL STUDY OF GLIOBLASTOMAS AND ASTROCYTOMAS

Abstract Glioblastoma multiforme (GBM) is a WHO grade IV malignant tumor with a relatively poor prognosis (median survival of 15 months). Astrocytomas are WHO grade I-III tumors with a better prognosis than GBM; their median survival ranging from 2-10 years. We assessed the response to various mainstay treatment modalities in patients with GBM and astrocytoma, expecting to find that surgery and stereotactic radiation (SRS) treatment confer greater survival benefits than non-surgical and whole brain radiation (WBRT) options. We analyzed 108 patients at St. Luke’s University Health Network (SLUHN) who were previously diagnosed with a primary brain tumor consistent with GBM (90) or astrocytoma (18) prior to January 1, 2023. Mainstays of treatment were surgery with or without different radiation modalities (WBRT and SRS, and WBRT+SRS). Glioblastoma typically affected older patients (65.5), had mostly single lobe involvement (86.7%), and was predominantly located in the frontal (41.1%) and temporal lobes (37.7%). Astrocytoma was slightly younger (51.2), less often single lobe (72.2%), and mostly involved the frontal (44.4%), temporal (44.4%), and parietal lobes (33.3%). GBM found the greatest benefit from WBRT (without co-occurring SRS) with an increase of 16.4 months to 20.2 months (p=.789). Surgery, regardless of radiation status, appeared to provide the greatest benefit for patients with astrocytoma increasing average lifespan from 36.7 months to 53.6 months (p=.181). Patients with glioblastoma that underwent surgery also had increased survival of 18.2 months compared with nonsurgical patients at 12 months (p=0.097). While we were interested to see the impact these treatment modalities had on patient survival, our sample size was small and our results lacked statistical significance. Future studies with greater sample sizes would help determine whether statistical significance is correlated with meaningful clinical outcomes.

TMET-08. RADIATION-INDUCED SLC25A22 CONTRIBUTES TO GLIOBLASTOMA RADIORESISTANCE ACQUISITION THROUGH REMODELING GLUTAMATE METABOLISM

Abstract Glioblastoma Multiforme (GBM), a malignant primary brain tumor, is treated by surgical resection followed by chemo- and radiotherapy. Nevertheless, most GBM patients show dismal prognosis due to the radioresistance acquisition of GBM cells via metabolic rewiring. Therefore, it is urgently required to discover how metabolic rewiring attributes to GBM radioresistance, and its targeting strategies. To identify GBM radioresistance driver genes, we previously established radioresistance GBM cells (RGCs) via repetitive in vivo selection, followed by mRNA sequencing, and selected candidate genes that are altered in RGCs (fold change>2 or <0.5, p-value<0.05) and also related with GBM patients’ prognosis. Here, we focused on amino acid transmembrane transporter (Gene Ontology: 0003333) and found that SLC25A22 was the most increased in RGCs. SLC25A22 exhibits uni-directional properties, exporting glutamate to cytosol, resulting in cytosolic glutamate accumulation in RGCs. Using 13C glutamine isotope tracing analysis following mitochondrial fractionation, we quantified the mitochondrial metabolic flux of glutamine. Despite decreased 13C glutamate efflux from RGCs mitochondria after genetic inhibition of SLC25A22, glutamine metabolites (a-ketoglutarate, succinate, malate, fumarate) remained constant. Cytosolic glutamate, as a substrate, is incorporated into various biosynthetic pathways, especially glutathione (GSH) and proline synthesis pathways in radioresistant GBM cells. GSH protects GBM cells by scavenging radiation-induced reactive oxygen species. Whereas, proline, a rate-limiting substrate for collagen biosynthesis, leads GBM cells to show an invasiveness phenotype via extracellular matrix remodeling. Genetic inhibition of SLC25A22 using short hairpin RNA (shRNA) or microRNA-184 mimic suppresses RGCs radioresistance and aggressiveness. Additionally, intranasal administration of microRNA-184 mimic prolonged the survival (median survival: 26 days after irradiation) of GBM-bearing mice, compared with non-target control (median survival: 16 days after irradiation). Together, our study demonstrates that SLC25A22 upregulation confers GBM radioresistance by inducing cytosolic glutamate-driven biosynthesis and suggests SLC25A22 as a therapeutic target to overcome GBM radioresistance.

TMOD-12. DEFINING THE ROLE OF THE DAAM2 R414W GERMLINE VARIANT IN FAMILIAL GLIOMA

Abstract Malignant glioma is the most common primary brain tumor in adults, leading to high morbidity and mortality due to its aggressive nature and limited efficacious treatment options. To improve this prognosis, research has focused on genetic factors that may contribute to glioma. While most glioma cases arise from sporadic somatic mutations, approximately 5-10% are classified as familial glioma, stemming from inherited genetic variations. Although several studies have explored mechanisms behind somatic mutations in glioma, less is known about hereditary variants that promote glioma susceptibility. We recently discovered five germline mutations in Daam2 (Dishevelled associated activator of morphogenesis 2) from familial glioma patients. To examine the role of these mutations in familial glioma, we overexpressed these mutations in patient-derived glioma stem-like cells, which were subsequently orthotopically xenografted into immunodeficient mice. We identified that one of these mutations, Daam2-R414W, promotes tumor cell proliferation both in vitro and in vivo. To further understand the role of the Daam2-R414W mutation in familial glioma, we generated a knock-in immunocompetent mouse model with the Daam2-R414W mutation. In these mutant mice, we found an increased number of proliferating glial progenitor cells in the subventricular zone compared to Daam2 wildtype mice, suggesting the potential of the Daam2-R414W mutation to influence glial progenitor expansion to stimulate glioma initiation. Furthermore, to establish a potential mechanism, we performed proteomic profiling of Daam2 wildtype and Daam2-R414W overexpression tumors and found enrichment of Git1, a GTPase-activating protein involved in cytoskeletal remodeling, suggesting that the Daam2-R414W variant may interact with Git1 to promote tumor invasion. Our findings thus far identify a hereditary genetic variant with the potential to increase the risk of glioma, shedding light on the repercussions of a human developmental gene variant and its potential to disrupt normal cellular machinery to promote malignancy and glioma development.

QLTI-12. COST ANALYSIS OF EMERGENCY PROCEDURES FOR BRAIN TUMORS – WHEN YOU CAN WAIT

Abstract BACKGROUND Neurosurgery is expensive and requires advanced technology to achieve the best outcomes, especially for brain tumors. Generally patients are prepared during consultations for a brain tumor surgery, with anesthesiology, cardiology, neuropsychology and other specialties evaluations. Ideally, the hospitalization is planned before and patient is admitted only when is in good conditions. However some patients with brain tumors are evaluated in emergency department and sometimes require urgent procedures. OBJECTIVE This study aimed to estimate the direct cost of specialized care for adult neuro-oncological patients considering previous scheduled procedures versus urgent surgeries and another factors that may impact decision about nonelective procedures. METHODS This observational economic analysis describes the direct cost of care of neuro-oncological patients in Santa Casa de São Paulo, Brazil. Only adult patients with a common primary brain tumor were included. RESULTS The global mortality rate considering all patients were 12.7% and 92.3% of them occurred in nonelective procedures. Also these patients had a greater infection rate and period of hospitalization. Because of this we reviewed when a patient with brain tumor really need an urgent procedure. Despite several patients are initially diagnosed through ER investigation, probably the majority could be compensated through ambulatory consultations and after admitted with better conditions. Situations in which emergency surgery are required include acute hydrocephalus and non-compensated intracranial hypertension. CONCLUSIONS These patients usually have difficulty access to neurosurgical evaluation and so, only look for health assistance when the disease cause severe disability. Emergency surgeries were associated with an increased rate of infections and mortality. The findings of this study could be used by policymakers for resource allocation and to perform economic analyses to establish the value of neurosurgery in achieving global health goals. severe disability. KEY WORDS: costs; brain tumor; emergency; infections

CNSC-26. INVESTIGATING THE ROLE OF QUAKING IN REGULATING MHC II ANTIGEN PRESENTATION IN TUMOR-ASSOCIATED MACROPHAGES OF GBM

Abstract Glioblastoma (GBM) is the most common and malignant primary brain tumor with a median survival rate of 14 months. Despite the success of immunotherapy in treating various cancer types, its efficacy remains poor in GBM. Such limitation can be attributed to the profound immunosuppressive tumor microenvironment of GBM enriched with the tumor-associated macrophages (TAMs). Quaking (Qki) is an RNA-binding protein that is mutated or deleted in more than 35% of GBM patients. Decreased levels of Qki in TAMs associates with worsened survival rates and responsiveness to immunotherapy in GBM mouse and patients. Moreover, Qki is a tumor suppressor gene in GBM and a major regulator in phagocytosis, a fundamental biological process in delivering antigens to major histocompatibility complex class II (MHC II). MHC II-restricted antigen presentation in macrophages of GBM is important in maintaining the fitness of cytotoxic and helper T cells required in anti-tumor response. However, the mechanism through which Qki regulates MHCII expression and presentation has yet to be elucidated. I hypothesize that Qki promotes MHC II expression in TAMs, thereby constraining the development and progression of GBM. In vitro assays like immunofluorescent staining, qRT-PCR, cell co-culture system, and flow cytometry will be performed involving QPP (Qk-/-Trp53-/-; Pten-/-) mouse brains, QPP cells, and mouse macrophage cell lines. A positive correlation between transcriptomic and protein expression levels of Qki, MHC II, and CIITA (a master regulator of MHC II) was confirmed in both mouse QPP and human GBM samples. Moreover, bone-marrow-derived macrophages activated by QPP cell supernatant shows upregulated levels of Qki and thus MHC II genes. A preliminary conclusion is that Qki plays a permissive role in MHCII expression in TAMs of GBM. Further downstream impact of Qki in TAMs will be evaluated in T cell activity and in transcription of MHC II in TAMs.

TMET-15. INVESTIGATING THE IL4I1-AHR AXIS IN GLIOBLASTOMA METABOLISM

Abstract Glioblastoma (GB) is the most frequent and malignant form of primary brain tumors in adults. Despite multi-modal therapy consisting of surgery, radio- and chemotherapy, tumors recur and overall survival remains poor. Previously, we identified that besides the classical tryptophan-catabolizing enzyme tryptophan-2,3-dioxygenase (TDO2), the L-amino acid oxidase interleukin-4-induced 1 (IL4I1) is able to activate the transcription factor aryl hydrocarbon receptor (AHR) via production of downstream metabolites. Activation of the AHR in GB may promote tumor progression e.g. by inhibiting anti-tumor immune responses. In this study, we aim to elucidate further the specific effects of the metabolic enzyme IL4I1 and its metabolites on AHR activation in GB. Further, we set out to identify and validate novel AHR target genes downstream of IL4I1. Harnessing the IL4I1-AHR axis might lead to the development of novel therapy strategies helping to overcome resistance in GB in the future.

NCOG-13. ASSESSING CAREGIVER OUTCOMES OF PRIMARY BRAIN TUMOR PATIENTS: A SYSTEMATIC REVIEW OF THE LITERATURE

Abstract BACKGROUND Family caregivers in neuro-oncology are known to have high levels of unmet support needs. Intervention trials and effective support options are scarce. The Response Assessment in Neuro-Oncology (RANO-) Cares working group has been established to determine standards of caregiver outcomes (CO) research reporting in neuro-oncology. We present the current state of methodological quality of reporting on neuro-oncology caregiver outcomes in randomized controlled trials (RCTs). METHODS A systematic literature review (PubMed/Medline, Embase, Web of Science, Emcare, Cochrane Library, PsycINFO; July 2023) was performed to assess to what degree RCTs assessing outcomes of family caregivers of adult primary brain tumor patients adhere to established reporting standards. Using Covidence, screening and data extraction was independently performed by two researchers, with a third guiding consensus. A 33-item checklist (23 applicable to secondary analysis reports) based on the International Society for Quality of Life (ISOQOL) Research criteria for patient-reported outcome reporting was utilized to assess reporting standards. Risk of bias was assessed per RCT. RESULTS Fifteen publications (12 unique RCTs) included 684 neuro-oncology caregivers, with low overall risk of bias. Ten publications (66%) reported on COs as a primary aim and eight (80%) of these satisfied ≥2/3 of the key methodological criteria. Of the five secondary analysis reports (33%) two met ≥2/3 of applicable key criteria. Criteria often missed are related to sample size calculations, details on statistical approaches, discussion of limitations and clinical significance of studies. Only three of the 12 RCTs were definitive trials aimed at improving COs and five should be considered as pilot or feasibility studies. CONCLUSION RCTs investigating neuro-oncology COs have high reporting standards and risk of bias was low. Future studies should focus on specific caregiver interventions to reduce high caregiver burden and with that patients’ quality of life.

NIMG-19. DEUTERIUM METABOLIC IMAGING INTERROGATES THE HISTONE H3K27M MUTATION AND PROVIDES AN EARLY READOUT OF RESPONSE TO THERAPY IN DIFFUSE MIDLINE GLIOMAS

Abstract Diffuse midline gliomas (DMGs) are lethal primary brain tumors in children that are driven by recurrent lysine 27 to methionine mutations in histone H3 (H3K27M). Radiation is standard of care and the imipridones ONC201 and ONC206 have emerged as promising therapies for DMG patients. Although magnetic resonance imaging (MRI) is the mainstay for patient management, it does not reliably assess response to therapy. Therefore, the goal of this study was to identify metabolic alterations induced by H3K27M that can be leveraged for non-invasive metabolic imaging of DMGs. Using patient-derived (BT245, SF8628, SF7761, SU-DIPG-6, DIPG7, SU-DIPG-13) and syngeneic (26-B7, 26-C2) models, we show that the H3K27M mutation upregulates glucose metabolism via glycolysis to lactate. Silencing the H3K27M mutation reduces glycolytic capacity and depletes lactate, an effect that is associated with downregulation of rate-limiting glycolytic enzymes and transporters (SLC2A1, HK2, PFKFB3, PGK1, SLC16A3). Deuterium metabolic imaging (DMI) is a novel, clinical stage method of tracing glucose metabolism in vivo. Our studies show that lactate production from [6,6-2H]-glucose is spatially localized to tumor vs. normal brain in mice bearing intracranial BT245, SF8628 or 26-B7 xenografts at clinical magnetic field strength (3T). Lactate production from [6,6’-2H]-glucose is reduced in patient-derived (BT245, SF8628, SF7761) or syngeneic (26-B7) cells treated with radiation, ONC201 or ONC206. Importantly, lactate production is reduced at an early timepoint (5 days) following treatment with ONC206, when changes cannot be detected by MRI, in mice bearing intracranial BT245 or SF8628 xenografts. Collectively, our studies link the H3K27M mutation with elevated glycolysis and identify [6,6’-2H]-glucose as a safe, orally administered contrast agent for visualizing the metabolically active lesion and for imaging early response to therapy in DMGs in vivo. Clinical translation of our studies will provide physicians with a much-needed tool to determine whether DMG patients are responding to standard and experimental therapies under development.

NCMP-11. FACTORS INFLUENCING MANAGEMENT STRATEGY AND CLINICAL OUTCOMES IN LOW-GRADE IDH-MUTANT ASTROCYTOMA: A 10-YEAR INSTITUTIONAL CASE SERIES

Abstract BACKGROUND Low-grade IDH-mutant astrocytomas are rare primary brain tumors that typically affect young adults and slowly progress to more aggressive lesions when untreated. Since lengthy follow-up is required to identify high-risk subgroups and useful therapeutic strategies, consensus recommendations after maximal safe resection are still based on low-level evidence and remain unclear. METHODS Retrospective chart review of all adult patients with a pathological diagnosis of low-grade (grade 2) IDH-mutant astrocytoma from 2013–2023 at a multi-site tertiary care center was performed. Cases without confirmatory IDH-mutation testing or at least 6-month follow-up imaging were excluded. RESULTS A total of 32 patients were included with a mean age of 35.6 years (range: 18–69) and 15 (46.9%) females. Mean follow-up was 40.3 months (range: 8.1–120.7). Preoperative average maximal tumor diameter was 4.1cm (range: 1.4–7cm) with 18 (56.3%) cases involving eloquent cortex. Gross total resection (GTR) was achieved in 12 (37.5%) cases. Observation was the most prevalent postoperative management strategy (n=21, 65.6%), followed by temozolomide-based chemoradiation (n=5, 15.6%), temozolomide alone (n=2, 6.3%), PCV (n=2, 6.3%), radiation alone (n=1, 3.1%), and carboplatin (n=1, 3.1%). Progression of disease (POD) was eventually seen in 17 (53.1%) cases with a median progression-free survival (PFS) of 41.9 months. While GTR was protective against POD (OR:0.14, p=0.019*), initial postoperative management with adjuvant chemotherapy and/or radiation was not (OR:1.09, p=0.907). Additionally, seizures during the follow-up period were significantly associated with POD and a reduced PFS (median 32.5 versus 71.7 months, HR:3.88, p=0.013*). There were no differences in EOR or tumor localization between patients who did and did not have seizures during follow-up. CONCLUSIONS Although limited by sample size, this 10-year series confirms the importance of maximizing EOR for low-grade IDH-mutant astrocytoma and suggests that seizures during follow-up can identify high-risk cases that may benefit from more aggressive treatment.

TMIC-02. SINGLE-CELL HIGH-DIMENSIONAL MASS CYTOMETRY (CYTOF) REVEALS IMMUNE LANDSCAPE OF PITUITARY NEUROENDOCRINE TUMORS

Abstract Pituitary neuroendocrine tumors (pitNETs) are a group of neoplasms in the sellar region, ranking as the second most common primary brain tumors, with some exhibiting aggressive behaviors. While immunohistochemical staining has been utilized to characterize the tumor immune microenvironment (TIME) of pitNETs, single-cell analysis remains underexplored. High-dimensional mass cytometry (CyTOF) offers a valuable approach for precise quantification of intratumoral leukocytes and potential therapeutic insights. We prospectively enrolled 56 patients with pitNETs of varying endocrine function, histology, and lineage. CyTOF, employing heavy metal-tagged antibodies, was employed to simultaneously measure 37 cellular parameters at single-cell resolution. Analysis revealed a total of 71,049 CD45+ immune cells. Macrophages (mean, 50.7%) and T cells (mean, 28.7%) were the predominant leukocytes, followed by NK cells, dendritic cells, B cells, and neutrophils. The immune cell composition within the TIME exhibited heterogeneity, with distinct patterns observed between functioning and non-functioning pitNETs. Functioning pitNETs displayed fewer macrophages (28.9% vs. 62.9%) and more T cells (44.9% vs. 19.6%) compared to non-functioning pitNETs. Subgroups within functioning (somatotroph, mammosomatotroph, lactotroph) and those within non-functioning pitNETs (null-cell, gonadotroph, corticotroph) shared similar immune profiles, respectively. PIT-1 lineage pitNETs demonstrated a T cell-dominated pattern, while SF-1, T-PIT, and null-cell lineage pitNETs exhibited macrophage predominance. In functioning pitNETs, macrophage abundance negatively correlated with invasiveness, Ki-67 index, and recurrence, while CD4 T cells showed positive correlations. Further unsupervised clustering identified 27 subpopulations of intratumoral immune cells, with some serving as critical predictors of tumor behavior. Our study provides a comprehensive single-cell immune profile of pitNETs, revealing distinct features across subtypes and targeted therapeutic implications.

TMET-14. ENOLASE 2 IS A UNIQUE METABOLIC VULNERABILITY INDUCED BY THE 1P19Q CODELETION IN OLIGODENDROGLIOMAS

Abstract Gliomas are devastating primary brain tumors in adults. The presence of an isocitrate dehydrogenase mutation combined with a chromosomal 1p/19q codeletion discriminates oligodendrogliomas from astrocytomas. The goal of this study was to leverage metabolic vulnerabilities induced by the 1p/19q codeletion for oligodendroglioma therapy. The 1p19q codeletion results in loss of enolase 1 (ENO1), which converts 2-phosphoglycerate to phosphoenolpyruvate during glycolysis. Here, we show that enolase 2 (ENO2) is upregulated in patient-derived oligodendroglioma (SF10417, BT88, BT54) models relative to astrocytoma (BT142, SF10602) and normal human astrocytes. ENO2 is also elevated in oligodendroglioma patient biopsies relative to astrocytoma or gliosis. Mechanistic studies indicate that inhibiting MEK1 or ERK1 abrogates ENO2 expression, suggesting that the MAPK pathway upregulates ENO2 in oligodendrogliomas. Next, we examined the therapeutic potential of targeting ENO2 in oligodendrogliomas. Genetic ablation of ENO2 or pharmacological inhibition using POMHEX inhibited the viability of SF10417 and BT88 cells with IC50 values of ~50 nM. In contrast, the IC50 for BT142 and SF10602 astrocytoma cells was ~5-8 uM, highlighting the exquisite dependence of oligodendrogliomas on ENO2. However, ENO2 inhibition did not lead to cytotoxicity in patient-derived oligodendroglioma cells or intracranial tumor xenografts. To assess the metabolic consequences of ENO2 inhibition and identify potential compensatory alterations, we traced [U-13C]-glucose metabolism in vivo in mice bearing intracranial SF10417 tumors. Although POMHEX abrogated glycolytic metabolism downstream of 2-phosphoglycerate, it shunted glucose towards biosynthesis of serine, glycine, methionine and purine nucleotides, an effect that was driven by phosphoglycerate dehydrogenase (PHGDH), the rate-limiting enzyme for serine biosynthesis. Importantly, the novel PHGDH inhibitor PHGDH-D8 was synthetically lethal in combination with POMHEX in oligodendroglioma cells and the combination induced apoptosis in mice bearing intracranial SF10417 tumors. Collectively, we exploit a mechanistic understanding of metabolic vulnerabilities induced by the 1p19q codeletion to identify combined inhibition of ENO2 and PHGDH as a novel therapeutic opportunity for oligodendrogliomas.