Aggressive Tumor Research Articles

PATH-03. SPATIAL-RESOLVED METABOLOMICS ANALYSIS IN HISTOLOGICAL AND MOLECULAR GLIOBLASTOMAS USING A MOF/MXENE-ASSISTED LDI-MSI PLATFORM

Abstract Glioblastoma (GBM) is a highly aggressive primary brain tumor encompassing both histological and molecular subtypes. Metabolites within the tumor microenvironment play critical roles in regulating tumor behavior and response to therapy. Understanding their spatial distribution provides valuable insights for diagnosis and treatment. We investigated metabolite patterns of histological GBMs (hist-GBMs) and molecular GBMs (mol-GBMs) by developing a novel MOF/MXene platform for enhanced surface-assisted laser desorption/ionization mass spectrometry. Utilizing this platform, we analyzed the metabolomes of three hist-GBMs and three mol-GBMs. Our platform exhibited exceptional sensitivity, repeatability, and stability in detecting metabolite molecules. Analysis of the metabolomes revealed distinct spatial distributions and concentrations of various metabolites, including carbohydrates, amino acids, organic acids, nucleotides, and their precursors. Notably, certain metabolites such as TG(15:0/20:3n6/20:5(5Z,8Z,11Z,14Z,17Z)), PG(20:3(6,8,11)-OH(5)/i-21:0), and SM(d20:1/20:3(6,8,11)-OH(5)) were significantly enriched in hist-GBMs compared to mol-GBMs, while others, including lithocholic acid glycine conjugate, PE(P-16:0/14:1(9Z)), and CE(11:1D5), exhibited higher peak intensity in mol-GBMs. Overall, our findings underscore the existence of unique metabolomic signatures distinguishing hist-GBMs from mol-GBMs. In conclusion, heterogeneous metabolite distributions among hist-GBMs and mol-GBMs were revealed by our novel MOF/MXene assisted LDI-MSI platform, and unique metabolic signatures were identified. Advanced metabolomics analysis holds promise for precise biomedical diagnostics and individualized therapeutic strategies in GBMs.

EXTH-29. EVALUATION OF THE ANTITUMOR EFFECT OF A CHEMOTHERAPY-LOADED DEVICE FOR THE TREATMENT OF PRIMARY BRAIN TUMORS

Abstract Glioblastoma (GBM) is the most frequent and aggressive primary brain tumor in adults. Tumor recurrence is therefore inevitable, and median survival is just over 14 months. Currently available treatments are inadequate and do not provide optimal tumor control. We believe that treatment localized directly at the tumor site will eliminate a greater number of infiltrating tumor cells while significantly reducing systemic toxicity. For this project, we are collaborating with a team specializing in bioengineering, who have produced a biomaterial enabling the gradual release of various chemotherapeutic agents. Our aim is to use this biomaterial to deliver chemotherapeutic agents to the tumor site through the surgical cavity. Cell-based assays were carried out using glial tumor cells in the presence of the biomaterial containing chemotherapeutics. A survival study was realized with the Fischer F98 rat model, which underwent partial tumor resection followed by injection of biomaterial containing chemotherapy. Histological studies of brains and resected tissues were also carried out to assess the effect of the biomaterial on the brain environment. In vitro assays showed a strong cytotoxic effect against glial tumor cells at 24h, 48h and 72h of biomaterial-drug incubation. The combination of two chemotherapeutic agents showed the best cytotoxic effect on glial tumor cells. We also performed a partial tumor resection and insertion of the chemotherapy-loaded biomaterial into the surgical cavity of the F98 glioma bearing rat. Similar to in vitro studies, the combination of two antineoplastic agents shows a significant improvement in animal survival. In conclusion, the in vitro and in vivo results of this study show that the combination of chemotherapy has the greatest antitumor effect. We hope that these exciting results will lead to the development of a new treatment for patients with glioblastoma and potentially other diseases where complete tumor resection is impossible.

DISP-17. OUTCOMES, CLINICAL AND MOLECULAR CHARACTERISTICS OF HISPANIC PATIENTS WITH IDH WILDTYPE GLIOBLASTOMA

Abstract BACKGROUND Knowledge about outcomes in Hispanic patients with gliomas is scant and mainly derived from tumor registries. IDH wild-type glioblastomas (GBM) are the most common and aggressive malignant primary brain tumor. Hispanics account for 19% of US population, reaching 29% in Florida and 65% in Miami-Dade County. As a reference center for GBM serving the community of South Florida we provide care for many Hispanic patients. Herein, we aim to describe the clinical and molecular features, including RNA seq analysis of Hispanic vs non-Hispanic patients with IDH wild-type GBM. METHODS Retrospective study of adult patients with diagnosis of IDH Wild-type Glioblastoma, who had NGS testing, treated at University of Miami. RESULTS 179 patients were included, 63 (35%) were Hispanic. 41 (65%) of Hispanic patients were males as compared to 65 (56%) of the non-Hispanics. Median age at diagnosis was 54 years (45-67) for the Hispanic vs 62 (54-72) years for non-Hispanic, p=.002. With a median follow up of 17 months (CI 95% 14-19), median overall survival for Hispanic patients was 22 months (18-25) and 23 months (18-28) for non-Hispanics, p=.99. 42 (23%) patients were enrolled in clinical trials, of whom 21 (50%) were Hispanic, meaning 33% of Hispanic patients enrolled. The molecular characteristics from these patients by next-generation sequencing, including RNA seq, are being analyzed. CONCLUSIONS In our series of IDH wild-type Glioblastomas, Hispanic patients were significantly younger at diagnosis compared to non-Hispanic patients, but there were no differences in overall survival. 33% of Hispanic patients were enrolled in clinical trials. As the latest growing ethnic group in the USA, major efforts have to be made to better understand the disease characteristics and outcomes of this particular population. To our knowledge this will be the first report of the molecular characteristics by NGS from Hispanic patients with GBM.

RADT-06. IDENTIFICATION OF NEW RADIATION RESPONSE PREDICTOR GENES FOR GLIOBLASTOMACRUCIAL CONTRIBUTION OF THE LUNATIC FRINGE GENE (LFNG)

Abstract Glioblastoma (GBM) is adults’ most common aggressive primary intracranial tumor. The current standard of care involves maximal safe surgery followed by radiochemotherapy. OBJECTIVE our study was to identify genes that predict response to radiochemotherapy. MATERIALS AND METHODS We collected molecular and clinical data, including primary glioma mRNA expression, from two international online databases - TCGA and CCGA. A total of 76 cases were examined, with 41 patients in the TCGA cohort and 35 in the CCGA cohort. The patients were divided into two groups before assessing the data. Group 1 included patients who were alive at the time of the analysis, and Group 2 included patients who had passed away. Then, we performed a single-center Moroccan transcriptomic study involving 28 cases to assess the impact of the individualized gene in our environment. RESULTS The following genes, namely SRPX, S100A16, LFNG, CD5, CMBL, and TCTN2, are among the top genes co-overexpressed in TCGA and CGGA patients. We conducted a multivariate COX survival test, taking into account known prognostic clinical parameters, and found that the LFNG gene is the only marker of poor prognosis independent of other clinical markers in TCGA and CGGA patients treated with radiotherapy. Our results indicate that patients who overexpress LFNG have elevated IFNg levels and low granzyme B levels, while the levels of perforin and granzyme A remain unaffected by LFNG variation. Furthermore, our results demonstrate positive correlations between LFNG gene expression and four immune checkpoints (PD1, PDL1, CTLA4, and VISTA), but negative correlations only with TIM3. CONCLUSION Our findings suggest that LFNG could serve as a useful biomarker for identifying patients with poor prognosis and that LFNG expression may be associated with specific immune checkpoint expression patterns. These results have important implications for the development of new therapeutic approaches in the treatment of TCGA and CGGA patients.

DNAR-06. EPITRANSCRIPTOMIC TRNA MODIFICATIONS TARGETING ADENOSINE (A) AT POSITION 37 IN GBM

Abstract GBM stands as the most aggressive brain tumor in adults. The median overall survival is less than 2 years despite conventional treatments. Recent advancements in DNA analysis have delineated the molecular characteristics of gliomas, leading to revisions in the WHO classification based on DNA profiles. However, the role of RNA modifications, epitranscriptomics, remains poorly understood in glioma. In this study, we underscore the significance of tRNA modifications targeting adenosine at position 37 in GBM. Transfer RNA isopentenyl transferase 1 (TRIT1) is identified as an isopentenyl transferase catalyzing the conversion of A into i6A at position 37 of tRNA, a nucleotide adjacent to the anticodon region. Additionally, i6A is further modified to 2-methylthio i6A (ms2i6A) by cyclin-dependent kinase 5 regulatory subunit associated-protein 1 (CDK5RAP1) within mitochondrial tRNA. Analysis of TCGA data reveals elevated TRIT1 mRNA expression levels in GBM compared to non-tumor samples. Furthermore, a low expression group of TRIT1 in gliomas demonstrates improved survival outcomes according to data from the CGGA, implicating TRIT1 in glioma progression. Functional assays involving TRIT1 knockdown in human GBM cell lines result in decreased cell viability, indicating its functional significance. Moreover, our data suggest that this phenotype may be mediated through translational control of selenoprotein W (SEPW1) via tRNA^(Ser)Sec modification. GO analysis of TRIT1 and SEPW1 in TCGA data further supports this proposed mechanism. At position 37 of tRNA, we also found that CDK5RAP1 in mitochondrial tRNAs is indispensable for sustaining glioblastoma initiating cell (GIC)-related traits. CDK5RAP1 maintains the self-renewal capacity, undifferentiated state, and tumorigenic potential of GICs, independent of translational control of mitochondrial proteins. Notably, CDK5RAP1 abrogates the antitumor effect of i6A by converting i6A to ms2i6A and shields GICs from excessive autophagy triggered by i6A. This work underscores the critical role of tRNA modifications in glioma pathogenesis. We will report these findings alongside RNA modification profile data and clinical data from glioma patients.

IMMU-22. TWIST1-MEDIATED ENDOTHELIAL PLASTICITY DRIVES GLIOBLASTOMA RESISTANCE TO CAR T IMMUNOTHERAPY

Abstract Glioblastoma (GBM) is the most common and most aggressive malignant primary brain tumor in adults. Among the most lethal human malignancies, GBM is highly resistant to cytotoxic treatments and molecularly targeted therapies, and also generally refractory to T cell–based immunotherapies, largely due to their immunologically cold nature, i.e., characterized by a paucity of tumor T cell infiltrates that result from the immunosuppressive microenvironment. Here, we identify a distinct mechanism driven by spatiotemporal interaction of leukocytes with tumor stromal cells, namely, mesenchymal-like population of endothelial cells (ECs) form an immunosuppressive vascular niche that regulates macrophage polarization and induces GBM resistance to CAR T immunotherapy. Our single-cell transcriptome analyses of human and mouse GBM tumors identify a subpopulation of ECs acquire robust immunosuppressive phonotypes to drive alternative macrophage polarization. These ECs are spatially localized proximately to immunosuppressive macrophages and selectively express Twist1. Furthermore, we reveal a Twist1/SATB1-mediated sequential transcriptional activation mechanism, through which Twist1+ tumor ECs produce osteopontin to locally promote immunosuppressive macrophage phenotypes. Genetic or pharmacological ablation of Twist1 reverses macrophage-mediated immunosuppression and enhances T cell infiltration and activation, leading to reduced GBM growth and extended mouse survival. Importantly, pharmacological inhibition and lipid nanoparticle-mediated targeted inactivation of Twist1 overcome GBM resistance to Egfrviii CAR T cell immunotherapy. Thus, these findings uncover a spatially restricted mechanism controlling vasculature-mediated tumor immunity and suggest that targeting endothelial Twist1 may offer exciting opportunities for GBM immunotherapy.

CSIG-15. ACROLEIN INDUCES THE MIR-30A-5P/NCAM AXIS VIA THE AKT/GSK3Β/Β-CATENIN PATHWAY, PROMOTING GLIOMA PROGRESSION

Abstract Glioblastoma (GBM), the most aggressive brain tumor, exhibits resistance to treatment and thrives in low-oxygen (hypoxic) environments, leading to the accumulation of reactive oxygen species (ROS). Hypoxia activates the hypoxia-inducible factor (HIF)-1α pathway, enhancing tumor malignancy. Acrolein, a reactive aldehyde produced during lipid peroxidation in hypoxia, induces toxicity through DNA damage, inflammation, mitochondrial dysfunction, and oxidative stress. Our previous study found elevated acrolein levels in hypoxic glioma cells and linked acrolein-induced DNA damage (Acr-dG) with poor GBM prognosis. However, the role of acrolein in GBM progression remains unclear. This study aims to elucidate the impact of acrolein on GBM. In vitro experiments demonstrated acrolein production under hypoxia, which increased glioma cell migration and spheroid formation. RNA sequencing identified five affected pathways: cell adhesion molecules, PI3K-AKT signaling, ECM-receptor interaction, MAPK signaling, and neuroactive ligand-receptor interaction. Acrolein downregulated NCAM (neural cell adhesion molecule) via the miR-30a-5p-AKT-GSK3β/β-catenin axis in GBM cell lines and patient-derived cells. Overexpressing NCAM reduced cell migration and spheroid formation. Lower NCAM levels in GBM tissues correlated with poor patient survival. This study suggests the potential of NCAM as a therapeutic target for GBM and provides insights into early detection and treatment strategies for this malignancy.

DDDR-44. REPURPOSING SSRI/SNRI TARGETING NEUROTRANSMITTER SIGNALING TO OVERCOME RESISTANCE TO CDK9 INHIBITORS IN DIFFUSE MIDLINE GLIOMA

Abstract Diffuse midline glioma (DMG) is a subset of aggressive brain tumors with few effective therapies. Cyclin-dependent kinase 9 (CDK9i) inhibitors such as zotiraciclib (ZTR) are in clinical trials for glioma, but CDK9i treatment alone may be ineffective due to the development of resistance. To identify CDK9i resistance mechanisms, we analyzed the transcriptomes of DMG xenograft tumors after three weeks of treatment with ZTR, which revealed that transcripts encoding synaptic signaling regulators such as glutamate receptors were overexpressed in surviving cells, suggesting that altered regulation of synaptic signaling may mediate CDK9i resistance. We also performed drug synergy screens using a library of FDA-approved and bioactive compounds and found that drugs that modulate neurotransmitter signaling, such as SSRIs and SNRIs (selective serotonin and serotonin/norepinephrine reuptake inhibitors), increased DMG sensitivity to an IC25 dose of ZTR. Follow-up studies confirm that combinations of structurally distinct CDK9i (ZTR, AZD4573) and SSRI/SNRI (sertraline, duloxetine) synergistically reduce DMG growth in neurospheres by BLISS analysis and show that co-treatment with CDK9i and SSRI/SNRI strongly induces the apoptotic marker cleaved caspase 3 and reduces the CDK9 target phos-Pol2Ser2. Additional phospho-proteomic analyses identified differentially phosphorylated proteins following CDK9i+SSRI treatment, including chromatin regulators, Pol2 elongation factors, and splicing regulators. Further RNAseq studies reveal that CDK9i+SSRI treatment resulted in more robust transcriptional changes than either drug alone, including the downregulation of transcripts associated with ZTR resistance such as GRIA3/4, and SYT12. These observations suggest that CDK9i +SSRI/SNRI drug combinations may overcome some of the transcriptional changes underlying CDK9i resistance. Finally, preclinical studies show that co-treatment with low doses of AZD4573 and sertraline reduces the growth of orthotopic DMG xenografts and prolongs overall survival. Taken together, these data suggest that SSRI/SNRI and CDK9i might be used in combination to synergistically reduce DMG growth and overcome CDK9i resistance.

EPCO-21. ELUCIDATING THE FUNCTIONAL RELEVANCE OF ATRX-DEFICIENCY IN H3.3-G34-MUTANT DIFFUSE HEMISPHERIC GLIOMA

Abstract Diffuse hemispheric gliomas (DHGs) account for 30% of aggressive cerebral tumors in children and young adults, exhibiting abysmal outcomes. Co-existing recurrent mutations in H3.3 histones at residue G34 (H3.3-G34R/V mutation) and concurrent inactivating mutations in TP53 and α-thalassemia/intellectual disability-X-linked gene (ATRX) implicate a coordinated molecular effort to drive oncogenesis. ATRX, a core component of the SWItch/Sucrose Non-Fermentable chromatin remodeling complex, regulates the incorporation of histone H3.3 into chromatin sites across the genome to maintain epigenome integrity. Yet, it is unclear how ATRX loss combines with H3.3-G34R/V mutations to influence cellular phenotype and dysregulate neuro-developmental programs. We propose that ATRX deficiency coordinates with key oncogenic partners by inducing oncogenic transcriptional programs and neuro-developmental pathways in DHGs. To investigate this, we employed CRISPR-editing to model H3.3-G34R followed by ATRX knockdown (ATRX-KD) in a TP53 mutant (TP53-mut) human-induced pluripotent stem cell (h-iPSC) line, developing an isogenic system to map contributions to epigenetic dysfunction made by specific molecular alterations. Upon differentiation of our h-iPSCs to neural stem cells (NSCs), we found unique transcriptional profiles associated with each genetic alteration, with upregulation of forebrain progenitor genes driven by ATRX-loss. Hierarchal clustering of normalized transcript counts revealed gene signatures from each model driving unique functional pathways, with the ATRX-KD and the triple mutant (TP53-mut, ATRX-KD, H3.3-G34R) signatures enriched for neural development pathways. Additionally, both signatures were associated with published transcriptional profiles of G34-mutant DHGs, emphasizing the disease relevance of our models. Further, time-course analysis using cerebral organoids uncovered distinct morphological changes with each alteration, with the triple mutant exhibiting impaired differentiation at later time points. These latter findings suggest that ATRX deficiency transcriptionally influences early neuronal differentiation, effects further refined by H3.3-G34 mutation. To conclude, our innovative models demonstrate the involvement of ATRX in neuro-developmental and differentiation phenotypes, illuminating underlying molecular features of aggressive DHGs.

EXTH-27. POLYCOMB OVERACTIVITY DRIVES TUMORIGENESIS IN AGGRESSIVE CUSHING’S DISEASE

Abstract INTRODUCTION Aggressive Cushing’s disease (CD) tumors (Ki67 > 3%) exhibit rapid growth, poor postsurgical outcomes, and resistance to conventional therapies. Polycomb group (PcG) proteins are canonical epigenetic silencers that can drive tumor aggressiveness. We asked if PcG underlies rare but fatal pituitary tumor progression. METHODS We performed paired multiome analysis (single nucleus RNAseq and ATACseq) in 5 aggressive CD adenomas, and adjacent normal gland. We verified protein expression with multiplexed immunohistochemistry (mIHC) and PcG activity by H3K27me3 ChIPseq. Aggressive murine pituitary tumor cells ATT20 were treated using PcG inhibitors (DZNep, tazemetostat), HDAC inhibitor (vorinostat), or siRNA (Ezh2, Suz12). PcG binding to the POMC promoter was assessed by reverse chromatin immunoprecipitation (rChIP). We treated one patient off-label with oral vorinostat 400mg daily for 6 days prior to radiation. RESULTS PcG loci (EZH2 and EED) were more accessible in aggressive CD adenoma versus normal gland corticotrophs, and EZH2, SUZ12 and EED mRNA was robustly overexpressed. mIHC confirmed SUZ12, EZH2 and H3K27me3 overexpression, and ChIPseq confirmed polycomb overactivity in aggressive CD adenomas. Polycomb inhibition by DZNep, vorinostat, or siRNAs led to proliferative arrest and Pomc suppression in ATT20 cells (P < 0.05 versus controls). Vorinostat enriched Suz12 at the Pomc promoter (P < 0.01), confirming direct silencing. In a patient with aggressive CD and hypercortisolemia despite two prior surgeries, a single course of vorinostat decreased cortisol (24mcg/dL to 7.5mcg/dL) and ACTH (63.7pg/mL to 44.9pg/mL) prior to radiation therapy initiation. CONCLUSIONS PcG hyperactivity is associated with a more aggressive CD phenotype. We report here the therapeutic potential of HDAC inhibition against aggressive CD adenomas in a first-in-human application.

EXTH-67. ONCOLYTIC ADENOVIRAL INFECTION OF CHORDOMA ACHIEVES TREATMENT EFFICACY THROUGH IMMUNOGENIC CELL DEATH AND TUMOR MICROENVIRONMENT ALTERATION

Abstract Chordomas are locally aggressive neoplasms of the axial skeleton with recurrence rates approaching 40%. Moreover, recurrent chordomas are nearly impossible to eradicate—highlighting an unmet clinical need. Immunotherapeutic approaches, such as immune checkpoint inhibition (ICI), has been a successful tool to modulate the tumor microenvironment (TME) towards a pro-inflammatory, antitumor state. There is emerging interest in exploring immunomodulatory agents for chordomas. Oncolytic viral (OV) therapy uses genetically modified viruses which selectively replicate in tumor cells, mediate tumor cell lysis, and initiate a pro-inflammatory response within the infected TME. These findings suggest that OV therapy may be a clinically relevant, novel immunotherapeutic approach for chordoma. Using the replicating oncolytic adenovirus Delta-24-RGD, we investigate the efficacy of chordoma treatment using in vitro approaches, ex vivo bone scaffolds, and in vivo murine models. Additionally, we explore the underlying mechanism of OV cytotoxicity, immunogenic cell death, Brachyury modulation, and reshaping of the TME towards a pro-inflammatory state. Across a panel of human chordoma cell lines, Delta-24-RGD achieved viral infectivity, oncolysis and immunogenic cell death. This treatment response was similarly demonstrated in chordoma cultured in bone scaffold models. Delta-24-RGD infection was associated with concomitant Brachyury downregulation within both infected and uninfected chordoma cells in vitro, suggesting a pleiotropic effect following oncolytic viral infection. In vivo models of CH22 chordoma treated with Delta-24-RGD demonstrated shrinkage in tumor volume and enhanced overall survival. Utilizing a human chordoma tissue microarray, the immunosuppressive macrophage marker CD163 was associated with shortened recurrence free survival. Using macrophage/chordoma co-culture, Delta-24-RGD infection achieved a reduction in macrophage expression of CD163. Taken together, Delta-24-RGD demonstrated efficacy in multiple models of chordoma including mice bearing CH22 tumors. The chordoma TME is associated with clinical outcomes and Delta-24-RGD infection reverses a deleterious immunosuppressive immune profile. These studies provide a framework for future clinical trial implementation for patients with metastatic or recurrent chordoma.

CSIG-07. JAK1/STAT1/3 COOPERATES WITH THE CIC-FUSIONS TO DRIVE CIC-REARRANGED SARCOMAS

Abstract CIC-rearranged sarcoma (CRS) is an rare disease driven by a specific fusion protein involving the CIC gene. Occurrence in the brain is 3% in all CRS patients. The native CIC protein is a transcriptional repressor of the (RTK)/Ras/ERK signaling pathway, which is one of the most tumorigenic pathways in cancer. The most common rearrangement is with the double homeobox 4 (DUX4) transcription factor (CIC-DUX4), and others, such as CIC-NUTM1 fusions, have been identified in a subset of pediatric primitive neuroectodermal tumors. However, the molecular mechanisms by which CIC-fusions drive CRS remain unknown. Preliminary data shows that CIC-DUX4/NUTM1 fusions activate JAK and its downstream effector STAT1/3. We hypothesize that the JAK/STAT1/3 signal transduction pathway cooperates with CIC-fusions to induce the expression of oncogenic transcription factors ETV1/4/5 and drive these sarcomas. We show high levels of JAK1/STAT1/3 activation in patient-derived CRS cell lines (NCC-SCC-89/C) as compared to other sarcoma cell lines without the fusion. JAK1 inhibition using Solicitinib and Ruxolitinib reduced phosphorylation of STAT1/3 as well as protein and mRNA expression of ETV1/4/5, promoter activity of ETV5, cell proliferation and tumorgenicity. Interestingly DUX4 is involved in histone acetylation and STAT1 has been shown to activate p300/CBP complex which lead us to evaluating the role of STAT1 in the gene activation CRS. We elucidate mechanistically that the fusion proteins increase binding of STAT1/3 at the promoters of ETV 1/4/5. Importantly, JAK1 inhibition effectively reduces histone acetylation induced by CIC-fusions at the promoters of ETV1/4/5. To evaluate the pre-clinical effect of targeting the JAK1/STAT1/3 pathway, A CRS cell line (NCC-SCC-89/C) were grafted into NSG mice. Ruxolitinib treatment significantly reduced tumor volume, STAT activation, and ETV1/4/5. In conclusion, we show that the JAK1/STAT1/3 pathway plays a critical role in cooperating with CIC-fusions to drive CRS, providing insight into potential therapeutic avenues for these aggressive tumors.

CTIM-27. DOC1021 CELL-BASED VACCINATION AS ADJUVANT THERAPY FOR GLIOBLASTOMA: PHASE I CLINICAL TRIAL ANALYSIS

Abstract Glioblastoma is an aggressive tumor for which median survival remains 14-18 months despite aggressive standard of care. Cellular immunotherapy approaches have recently shown promise. Homologous antigenic loading is an ex-vivo technique that leverages p38MAPK and mTORC1 signaling cascades to initiate powerful cDC1-like skewing in monocyte-derived dendritic cells, leading to downstream induction of tissue-infiltrating, cytolytic effector memory T-cells. This open-label phase I clinical trial evaluated the autologous dendritic cell vaccine DOC1021 prepared through homologous antigenic loading and administered bilaterally near the deep cervical lymph nodes. Three courses of vaccine were administered every 2 weeks after completion of chemoradiation, adjuvanted concurrently with six weeks of weekly type I interferon. Four dose levels from 3.5x106 to 3.6x107 total vaccine cells were tested. Tumor progression prior to vaccination was not an exclusion criterion. Sixteen newly diagnosed IDH-WT patients completed treatment, median age 63 years and 94% MGMTp unmethylated. The most common related AEs were grade 1 injection-site reactions and grade 1-3 fatigue and urticaria. No DLTs were observed. Immunohistochemistry of tumors derived from early post-vaccination second resections showed enhanced CD8+ T-cell infiltration and pathologic findings consistent with residual rather than relapsed GBM in 2/3 patients. Analysis of post-vaccination PBMC in dose level cohorts 2-4 indicated expansion of both CD4+ (13/13) and CD8+ (11/13) central memory T-cell compartments (p<0.002 and p<0.05, respectively) as well as expansion of CD8+CD127+ T-cells (12/13; p<0.001). Among three patients for whom tissue was obtained pre- and post-vaccination, clinical outcomes correlated with Visium spatial transcriptomic analysis. Median survival for the MGMTp unmethylated cohort (n=15) has not yet been reached but is statistically greater (p<0.05) than that of matched historic controls. The results indicate that DOC1021 is safe, can be effectively integrated within existing standards of care and is potentially efficacious in a challenging patient population.

Therapeutic potential of targeting the FLNA-regulated Wee1 kinase in adrenocortical carcinomas.

Filamin A (FLNA) is poorly expressed in adrenocortical carcinomas (ACC) compared to adenomas (ACA). Its presence is associated to a less aggressive tumour behaviour, potentially due to its role in negatively regulating IGF1R signalling. Upregulation of G2/M Wee1 kinase was shown in FLNA-deficient mouse neural progenitor cells, and it has been reported in several tumours. This study explored Wee1 expression in ACC and its regulation by FLNA, the effects of Wee1 inhibitor AZD1775, and the impact of FLNA on its efficacy in ACC cell lines and primary cells. Analysis of FLNA and Wee1 proteins revealed elevated Wee1 and reduced FLNA in ACC compared to normal adrenal gland. FLNA knockdown increased Wee1 protein in NCI-H295R, MUC-1, and in primary ACC cells. Higher p-CDK1 and cyclin B1 were shown in FLNA-silenced MUC-1, while decreased Wee1, p-CDK1 and cyclin B1 resulted after FLNA overexpression. Wee1 reduction was reverted by lactacystin treatment and FLNA transfection increased p-Wee1 (Ser123), suggesting FLNA's role in targeting Wee1 for degradation. AZD1775 dose-dependently reduced proliferation and viability in ACC cell lines and primary cultures, and it triggered MUC-1 cell death. Similar effects were induced by Wee1 silencing. FLNA depletion augmented AZD1775's efficacy in reducing proliferation and potentiating apoptosis in MUC-1 and primary cells. In conclusion, we demonstrated that FLNA regulates Wee1 expression by promoting its degradation, suggesting that low FLNA typical of ACC leads to increased Wee1 with consequent cancer cells growth. It proposes Wee1 inhibition as a new potential therapeutic approach for ACC, particularly for those lacking FLNA.

EPCO-39. MULTIOMIC AND CLINICAL ANALYSIS OF MULTIPLY RECURRENT MENINGIOMAS REVEALS RISK FACTORS, UNDERLYING BIOLOGY, AND INSIGHTS INTO EVOLUTION

Abstract Although meningiomas, the most common primary brain tumor, are often effectively treated with surgery and radiation, an important subset of meningiomas behave aggressively and are characterized by treatment resistance and multiple recurrences. Prior work has yet to specifically study multiply recurrent meningiomas (MRMs), including whether they are molecularly distinct from non-recurrent meningiomas (NRMs) at initial diagnosis and whether the molecular features of MRMs evolve with subsequent recurrences. The objective of this study was to identify clinical and molecular features associated with MRMs and determine if longitudinal molecular changes occur in paired MRM samples. In this dual institution study, clinical parameters were collected for 1,186 meningioma patients. After propensity score matching, 31 MRMs were matched to 84 NRMs. Molecular sequencing including whole exome sequencing (n=44), EPIC bead chip methylation array (n=43), and RNA-sequencing (n=66) were performed. On multivariable binomial logistic regression, MRMs were significantly associated with male sex (P=0.012), subtotal resection (P=0.001), higher number of meningiomas on presentation (P=0.017), and histopathological sheeting (P=0.002). Multiomic analysis of primary meningiomas revealed MRMs exhibit greater global copy number alternations (CNA) (P=0.0113) and increased DNA methylation (P=0.0161). Integrated methylation profiling and RNA-sequencing identified candidate driver genes of MRMs. Among these genes, we demonstrate that knockdown of EDNRB, a locus with higher promoter methylation and decreased gene expression in MRMs, leads to increased meningioma cell proliferation, suggesting a tumor suppressor function. CNAs, subclonal evolution, and methylation profiles of MRMs did not significantly change from primary tumor to recurrence, even after radiation treatment, suggesting MRMs are molecularly aggressive from initial diagnosis. Overall, we identify several novel clinical and molecular risk factors associated with MRMs. MRMs harbor unique molecular features on presentation, which do not appear to change during evolution and after treatments, which has implications for development of biomarkers and therapeutic agents for these aggressive tumors.

ANGI-11. SEX DIFFERENCES IN SOX2 GLIOBLASTOMA EXPRESSION OUTSIDE MRI-DEFINED CONTRAST ENHANCEMENT AT AUTOPSY

Abstract INTRODUCTION Sex-determining region Y-box 2 (SOX2) has recently been used as a marker for pluripotency to identify cellular glioblastoma invasion pathologically. This can be used to identify areas of tumor invasion consisting of sparse individual cells, likely highlighting the furthest margin of tumor invasion. This study aligned large format SOX2 stained tissue samples to conventional MRI to determine demographic factors that impact the presence of SOX2 positive invasion outside the T1 contrast-enhanced tumor margin. METHODS The cohort for this study consisted of 36 IDH-wildtype glioblastoma patients (23 male, 13 female, mean age=61.9). Tissue samples from areas of suspected tumor invasion and normal tissue were collected at autopsy, stained for SOX2, digitized at 40X resolution, and automatically segmented for SOX2 positive staining cell percent (SOX2+%) at MR resolution using a color deconvolution algorithm. Contrast enhanced T1 scans from acquisitions close to death were annotated manually for tumor presence and aligned to the T2-weighted FLAIR image. Tissue data was then aligned to MR images using a custom in-house software that relies on manually defined control points to generate a nonlinear transform that warps tissue into MR space while correcting for tissue shrinkage. Mean SOX2+% was computed for each patient outside of contrast enhancement and compared across age and sex as demographic factors. RESULTS Males were found to have a higher SOX2+% than females outside contrast enhancement (t=2.09, p=0.045), while no association with age was observed (r=0.146, p=0.397). CONCLUSIONS Sex differences were observed for non-enhancing SOX2 positivity, which may relate to the more aggressive tumors identified in male patients in some studies. Further research into the mechanisms behind sex differences in tumor growth patterns and molecular characteristics impacting the infiltration of tumor beyond the MR defined region is needed.

EPCO-13. HUMAN ENDOGENOUS RETROVIRUS (HERV) PLAYS A CRITICAL ROLE IN ONCOGENIC MECHANISM INIDH1-WILD TYPE GLIOBLASTOMAS

Abstract IDH1-wildtype (WT) GBMs are the most common and aggressive tumors of the central nervous system (CNS), with a median survival rate of 12-15 months, and are resistant to clinical therapies due to their heterogenous molecular phenotype. In this study, we developed a pipeline to dissect the potential role of human endogenous retroviruses (HERVs) in patient derived glioma stem cells (GSCs) and integrated our findings with published epigenomic datasets for enhancers (H3K27ac), CTCF, and chromatin toplogy (Hi-C). We found high expression of several HERV transcripts in IDH1-WT GBMs as compared to IDH1-mutant variants. Epigenomic analysis of these upregulated HERVs showed association with both enhancer marks and CTCF deposition. Annotation of HERVs to their nearest genes, followed by Gene Set Enrichment Analysis (GSEA), identified involvement of actin-filament based mechanisms and regulation of immune phenotype. Integration of these findings identified MER61 (ERVMER61-1), a potential regulator of Interleukin-6 and showed alteration in chromatin looping and enhancer occupancy. To summarize, our work points to novel mechanisms of GBM pathogenesis, through involvement of HERVs in cell migratory and immune dysfunction, warranting further investigations into these oncogenic mechanism to identify and develop novel therapeutic options for GBM.

TMET-22. OVERCOMING RESISTANCE: PANOBINOSTAT SENSITIZES 2DG-RESISTANT PEDIATRIC HIGH-GRADE GLIOMAS WITH H3.3 K27M/G34R MUTATIONS TO APOPTOSIS

Abstract BACKGROUND Pediatric high-grade gliomas (pHGG) harboring H3.3 K27M/G34R mutations present formidable challenges in treatment due to their aggressiveness and resistance to standard chemotherapy. Our preliminary investigations have shown promising results, indicating that combining 2-deoxyglucose (2DG), a glycolytic inhibitor, with DNA-damaging agents synergistically inhibits pHGG growth. However, prolonged exposure to 2DG induces resistance, necessitating the exploration of alternative therapies. This study aims to investigate the potential of panobinostat, a histone deacetylase inhibitor, in sensitizing 2DG-resistant pHGG with H3.3 K27M/G34R mutations to apoptosis. METHODS Transcriptomic analysis via Illumina NovaSeq 6000 and metabolomic profiling employing Liquid Chromatography-High-Resolution Mass Spectrometry was used to delineate the molecular landscape of naive and 2DG-resistant pHGG cell lines. Functional assays, including the Agilent Seahorse Mito Stress Test and flow cytometry, assessed bioenergetics and mitochondrial dynamics. Intracellular NAD+ and NADH levels were quantified utilizing NAD+/NADH Glo assays, while apoptotic markers and metabolic stress were measured using the Annexin V-FITC Conjugates for Apoptosis Detection kit and western blot. RESULTS Comparative analysis revealed increased transketolase activity in 2DG-resistant cells, augmenting the interaction between the pentose phosphate pathway and glycolysis, resulting in elevated levels of NADPH and ATP. Additionally, these resistant cells displayed enhanced reliance on mitochondrial energy metabolism, as evidenced by substantial increases in mitochondrial membrane potential and mass, coupled with elevated NAD+ levels. Subsequent treatment with panobinostat induced a significant decrease in NAD+ biosynthesis and ATP generation. Furthermore, this intervention triggered the upregulation of pro-apoptotic BCL-2 family proteins, particularly BAX and BAK, concomitant with a notable reduction in mitochondrial membrane potential and the accumulation of reactive oxygen species. Consequently, heightened caspase-3 activity ensued, leading to significantly elevated cell death rates in 2DG-resistant gliomas. CONCLUSION Our findings highlight panobinostat as a promising therapy to resensitize 2DG-resistant pHGG cells to apoptosis, offering hope for treating these aggressive tumors with H3.3 K27M/G34R mutations.

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-18. MAPPING TUMOR HABITATS IN IDH-WILD TYPE GLIOBLASTOMA: INTEGRATING MR IMAGING, PATHOLOGIC, AND RNA DATA FROM IVY GLIOBLASTOMA ATLAS PROJECT

Abstract BACKGROUND To identify biologic correlates and spatially validate intratumoral subregions (tumor habitat) using diffusion-weighted and dynamic susceptibility contrast-imaging on a comprehensive pathology map of the isocitrate dehydrogenase (IDH)-wild type whole glioblastoma sample using the Ivy Glioblastoma Atlas Project (Ivy GAP). METHODS Complete data of 20 patients with 168 slides of IDH-wild type glioblastoma were obtained from the IvyGAP (http://glioblastoma.alleninstitute.org/). On MRI, tumor habitats were defined using voxel-wise clustering of apparent diffusion coefficient (ADC) and cerebral blood volume (CBV) maps for contrast-enhancing lesion (CEL) and peritumoral non-enhancing lesion (NEL). On pathology slides, normalized areas of leading edge (LE), infiltrating tumor (IT), cellular tumor (CT), hypervascular lesion (CThypervascular), and perinecrotic lesion (CTperinecrotic) were obtained. Gross specimen pictures were co-registered on MRI images for co-localization and correlation between MRI tumor habitats. Pathologic areas were calculated using Pearson’s correlation coefficient. RNA sequencing of 67 RNA-seq samples was assessed using 4 Neftel subtypes and further correlated with pathology. RESULTS Six tumor habitats were correlated: hypervascular, hypovascular cellular, and hypovascular hypocellular habitats for CEL and NEL. CT was strongly correlated with hypovascular cellular habitat in CEL (C2, r = 0.238, p =.005). IT was strongly correlated with hypovascular cellular habitat in NEL (C5, r = 0.294, p =.017). CThypervascular was correlated with hypervascular habitat in NEL (r = 0.195, p =.023). CTperinecrotic was correlated with imaging necrosis (r = 0.199, p =.005). Astrocyte-like subtypes were positively correlated with IT (r = 0.256, p <.001), while mesenchymal-like subtypes were positively correlated with CTperinecrotic area (r = 0.246, p <.001). CONCLUSION Pathologically matched tumor subregions were cellular tumor with hypovascular cellular habitat in CEL and infiltrative tumor with hypovascular cellular habitat in NEL. Identification of the most aggressive tumor portion, and infiltrative tumor portion using non-invasive imaging can be achieved using MRI tumor habitats.