Neuro-Oncology

Diffuse intrinsic pontine glioma (DIPG), now classified within diffuse midline glioma, H3K27-altered, remains a lethal pediatric brainstem tumor with limited therapeutic options. Here, we integrated public DIPG transcriptomic datasets, protein-protein interaction modeling, functional enrichment, immune deconvolution, survival analysis, and DepMap CRISPR dependency data to nominate candidate mitotic vulnerabilities. Differential expression analysis comparing 27 DIPG tumors with 6 brainstem low-grade glioma comparator samples identified a proliferative transcriptional program enriched for chromosome segregation, nuclear division, and cell-cycle pathways. Network analysis prioritized a compact mitotic hub module containing CDK1, AURKB, TOP2A, CDC20, CDCA8, and related G2/M regulators. CIBERSORT analysis of an independent DIPG cohort inferred low cytotoxic T-cell signal, consistent with an immune-cold phenotype, although immune-cell fractions require orthogonal validation. Survival analysis showed that neither inferred immune scores nor a composite mitotic hub score significantly stratified overall survival. DepMap CRISPR gene-effect data nominated CDK1, AURKB, TOP2A, and BIRC5 as candidate dependencies across brain tumor models. These findings provide a computational framework for prioritizing mitotic vulnerabilities in DIPG and support experimental validation in disease-relevant models.

CREB-regulated transcription coactivator 1 (CRTC1) regulates neuronal development, plasticity, and activity-dependent transcription, but its role in medulloblastoma (MB) remains poorly understood. We investigated expression of the CRTC1 gene during human cerebellar development and across pediatric brain tumors and examined its molecular and clinical associations in MB using public transcriptomic datasets. CRTC1 was broadly expressed in the developing cerebellum, with cell-state-specific variation within the granule-cell lineage. Among pediatric brain tumors, MB showed the highest median CRTC1 expression, which differed significantly among MB molecular groups and subtypes, with highest levels in Group 4 MB. High CRTC1 expression was associated with longer overall survival specifically in Group 3 {beta} MB and remained significant after correction across the 12 molecular subtypes. Within Group 3 {beta} tumors, CRTC1 expression was inversely associated with enrichment of mitochondrial and bioenergetic processes, including oxidative phosphorylation, mitochondrial organization, and mitochondrial translation, whereas CRTC1-high and CRTC1-low tumors displayed distinct transcriptional profiles. CRTC1 was also associated with selected cell-type-related transcriptional signatures related to the tumor microenvironment. These findings identify CRTC1 as a marker of biologically and clinically relevant transcriptional heterogeneity in Group 3 {beta} MB and support further investigation of its functional and prognostic significance.

Histone H3-G34R and H3-K27M mutations define distinct diffuse high-grade glioma subtypes diffuse hemispheric glioma (DHG), midline (DMG), and pontine gliomas (DIPG). We characterized pathway-architectures using cBioPortal and pedcBioPortal for H3-G34R (n=112) and H3-K27M (n=727) mutated-gliomas, co-mutations, copy numbers (CNA), and variant data (n=112/727, n=86/578, n=51/313). We evaluated altered-genes as oncogenic by OncoKB, Gene-Ontology (GO) heatmaps and process-enrichment using clusterProfiler (Benjamini-Hochberg-adjusted p<0.05). H3-G34R-gliomas harbored near-universal TP53 (94.1%), ATRX (81.4%) co-mutations and PDGFRA alteration (54.9% mutation; 17.1% amplification) within 4q12 amplicon that includes KIT and KDR. Pathway-enrichment converged on G1/S cell-cycle checkpoints, and epigenetic regulation, driven principally by TP53, ATRX, PTEN, BCOR, TERT, FBXW7, and PPM1D. CDK6 amplification was rare (2.6%), despite H3-G34R association with CDK6-dependency including benefit from CDK4/6 inhibition. H3-K27M-gliomas displayed PI3K/AKT pathway activation (PIK3CA, 14.9%; NF1, 13.3%; PDGFRA, 10.8%, PIK3R1, 7.8%; PTEN, 5.7%) and developmental signatures through NF1, PTEN, and SOX10 (4.95%) mutations. TP53 (62.2%) and ATRX (21.2%) co-mutations were less frequent in H3-K27M versus H3-G34R, while PPM1D was H3-K27M-enriched (19.3%). MGMT promoter methylation occurred frequently in H3-G34R (65.2%, 15/23) versus H3-K27M-gliomas (5.4%, 4/74), despite genome-hypomethylation of H3-G34R. H3-G34R-gliomas, unlike H3-K27M, upregulated ganglionic GSX2, DLX1, DLX2, and FOXG1. SOX10 was upregulated in H3-K27M-gliomas, versus H3-G34R. Lack of MGMT methylation in H3-K27M-gliomas correlates with temozolomide resistance; we previously reported imipridones ONC201/ONC206 reduce MGMT, EZH1 and EZH2 expression in H3-K27M-glioma cells. Divergent PDGFRA-mutations among MGMT-methylated versus unmethylated H3-G34R-gliomas warrants investigation of PDGFRA-signaling and epigenetic regulation. Our findings suggest divergent precision oncology therapeutic strategies to exploit unique vulnerabilities in H3-K27M and H3-G34R-gliomas.

Mismatch repair (MMR) deficiency contributes to temozolomide (TMZ) resistance in a subset of isocitrate dehydrogenase 1/2 mutant (IDHmut) gliomas, creating a need for therapies that retain activity despite MMR loss. We evaluated the novel interstrand crosslinking agent KL-50, alone and in combination with the histone deacetylase inhibitor belinostat, in patient-derived IDHmut glioma models. MSH6 knockout or constitutive expression established four matched MMR-proficient and MMR-deficient culture models. Drug responses were assessed using live cell count and cytotoxicity assays, and KL-50 monotherapy was tested in intracranial BT142 orthotopic xenografts. LOEWE synergy analysis, RNA sequencing, and a genome-wide CRISPR knockout screen assessed combination activity and potential mechanisms. MMR deficiency increased TMZ GI values 2.2- to 30.4-fold, whereas KL-50 retained antiproliferative activity and showed enhanced cytotoxicity in selected MMR-deficient models. In TMZ-naive, MMR-proficient BT142 xenografts, KL-50 increased median survival from 107.5 to 194 days. Two of eight treated mice had no histologically detectable residual tumor after 220 days post-engraftment. KL-50 and belinostat exhibited synergistic cytotoxicity in BT142, 905, and TS603 IDHmut glioma cultures. Transcriptomic gene ontology analyses identified downregulation of DNA repair pathways following histone deacetylase inhibition, including terms for homologous recombination and double-strand break repair. The CRISPR screen identified depletion of PKMYT1-targeting gRNAs during KL-50 treatment, implicating this mitotic checkpoint kinase as a candidate determinant of drug sensitivity. PKMYT1 expression was also reduced by histone deacetylase inhibition. These findings support further preclinical development of KL-50, alone and in combination with belinostat, for IDHmut gliomas including tumors with MMR-associated TMZ resistance.

Background: Pediatric and adult brain tumors, including glioblastoma, astrocytoma, ependymoma, and medulloblastoma, remain associated with poor prognosis despite advances in surgery, radiation, and chemotherapy. Therapeutic resistance, tumor heterogeneity, and treatment-related toxicity highlight the need for clinically relevant models that enable precision medicine and immunotherapy development. Methods: Freshly dispersed tumors (FDTs), low-passage patient-derived brain tumor (PBT) spheroid lines, and matched patient-derived xenograft (PDX) models were established from patients with primary brain tumors. Models were characterized using single-cell and bulk RNA sequencing, whole-exome sequencing, multiparameter flow cytometry, and immunohistochemistry. PBTs were compared with matched FDTs to evaluate model fidelity. Results: PBT lines were established in approximately 68% of cases and retained key patient-specific genomic alterations, including IDH1, MGMT, TP53, and PTEN, with expression of therapeutically relevant targets, including IL13R2, EGFR, HER2, WNT1, JAK1/2, and NOTCH1-4. Gene expression profiles of PBTs closely correlated with matched FDTs (R = 0.38, P = 0.0038). PBT and PDX models preserved intratumoral heterogeneity and non-clonal populations, enabling identification of therapy-resistant subclones during in vitro selection. Molecular analyses identified Stearoyl-CoA Desaturase1 (SCD1) as an overexpressed biomarker across glioma PBTs and matched patient tumors. Ingenuity Pathway Analysis identified SCD1 as an upstream regulator of EGFR-, TP53-, and CYCS-associated signaling networks implicated in tumor progression and immune suppression. Conclusions: Clinically relevant PBT and matched PDX models recapitulate molecular, transcriptional, and histopathological characteristics of primary brain tumors. These platforms provide tools for biomarker discovery, therapeutic testing, and precision immunotherapy development, while identifying SCD1 as a biomarker and therapeutic target in glioma.

ABSTRACT Background: High grade glioma (HGG), encompassing IDH-wildtype glioblastoma (CNS WHO grade 4), diffuse midline glioma (CNS WHO grade 4), oligodendroglioma (IDH-mutant and 1p/19q-codeleted) CNS WHO grade 3, together with IDH-mutant astrocytoma of CNS grade 3 and grade 4, represents the most lethal group of adult diffuse gliomas. Despite significant efforts, obtaining improvements in patient survival has been limited, in part, by difficulties in comprehensive ex vivo modeling of the complexities of HGG. Although organotypic slice cultures and other platforms have shown promise, existing models often fail to capture the intrinsic cellular heterogeneity, microenvironment, and architecture of HGG, restricting investigations into their fundamental biology as well as design of novel therapeutics. Methods: We developed a patient-derived HGG organotypic slice culture (GOSC) platform demonstrating long-term preservation of intrinsic tumor characteristics. Vibratome-sectioned slices were cultured in defined medium under conditions approximating those in situ: reduced oxygen (4%), low glucose (2.5 mM), and no added growth factors. The characteristics of GOSCs after 28 days in culture, including expression of immunotherapy targets, were compared to parental tumors using histological staining, immunofluorescence, multiplexed PhenoCycler (CODEX) imaging, bulk RNA-seq expression profiling, and CAR T cell killing assays. Results: GOSCs preserved the histopathology, cell heterogeneity, tumor microenvironment, and tissue architecture of their parental tumors throughout at least 28 days in culture. Importantly, GOSCs retained parental patterns of immunotherapy target expression, and CAR T cells co-cultured with GOSCs demonstrated target-specific killing consistent with parental tumors. Conclusions: This ex vivo GOSC platform offers long-term preservation of the cellular and structural properties of parental HGG tumors, thereby providing a robust tool for extended preclinical studies, and facilitating development and evaluation of advanced tumor-targeting strategies.

Group 3 medulloblastomas (G3MB) carry the worst prognosis among medulloblastoma subtypes, yet molecularly targeted therapies remain elusive. Standard treatments cause severe long-term morbidity in survivors. Here, we identify tumor-derived sphingosine kinase 2 (SPHK2) as an essential driver of G3MB initiation and progression. SPHK2 exacerbates local immunosuppression by suppressing cytotoxic T-cell and NK-cell activity while promoting regulatory T-cell infiltration. Genetic or pharmacologic SPHK2 inhibition using Opaganib attenuates pro-survival tumor signaling and restores anti-tumor immunity, significantly improving survival in syngeneic G3MB mouse models. Combining Opaganib with fractionated low-dose radiation (f-LDRT) further enhances antigen presentation and reprograms tumor-associated myeloid cells toward an anti-tumor phenotype. This combination therapy markedly prolongs survival without inducing significant toxicity. Overall, our study establishes SPHK2 as a previously unrecognized therapeutic target and presents a safe, effective, microenvironment-reprogramming regimen for G3MB. One Sentence SummaryDirect inhibition of tumor-derived SPHK2 overcomes local immunosuppression and downregulates pro-survival signaling in Group 3 medulloblastoma, while combination with fractionated low-dose radiation further enhances anti-tumor immunity and significantly improves survival.

BackgroundRadiotherapy can provide durable local control for optic pathway-hypothalamic glioma (OPHG), but its use is limited by concern regarding delayed vascular, endocrine, visual, oncological, and neurological toxicities. ObjectiveTo systematically characterize and quantify the safety of radiotherapy and radiosurgery for OPHG and explore clinically relevant modifiers of treatment-related toxicity. MethodsPubMed, Scopus, Web of Science, Embase, Cochrane, Google Scholar, and ClinicalTrials.gov were searched from inception through 1 June 2026. Eligible non-randomized studies reporting safety outcomes after radiotherapy or radiosurgery were included. Random-effects binomial-normal generalized linear mixed-effects models were used to pool proportions, with exact conditional models for sparse comparative analyses. ResultsThirty-five studies were included, of which 31 contributed event-level data to at least one quantitative safety outcome. The pooled incidence of any treatment-related toxicity was 8.46% (95% CI, 1.37-38.01%). Vasculopathy occurred in 9.44% (95% CI, 5.22-16.49%). Secondary neoplasms occurred in 5.41% (95% CI, 2.23-12.53%), decreasing to 2.83% under a strict malignant-event definition. Incident endocrinopathy had the highest pooled estimate at 21.19% (95% CI, 4.72-59.31%) and increased with longer follow-up. Treatment-related visual toxicity was 2.26%, whereas radiation-related mortality was 0.59%. Radiation necrosis, severe toxicity, and treatment-attributed neurocognitive toxicity were sparsely reported. ConclusionLate toxicity following radiotherapy for OPHG is heterogeneous, with endocrinopathy, vasculopathy, and secondary neoplasms representing the principal quantifiable safety concerns. Treatment decisions should therefore be individualized, with prolonged vascular, endocrine, visual, and oncological surveillance and further prospective evaluation of contemporary radiation techniques.

Background: IDH1 mutations in diffuse gliomas undergo epigenetic transformation and metabolic stress, through accumulation of 2-hydroxyglutarate. While these tumours generally exhibit a less aggressive phenotype, significant prognostic heterogeneity persists. The extent to which the One Carbon Metabolism (OCM) network is rewired in IDH1-MT gliomas and its contribution to this heterogeneity remain poorly understood. Methods: We analysed the expression of 64 OCM genes using TCGA and CGGA transcriptomic datasets (n = 709). Composite OCM score, Cohen's d, PCA and driver gene analysis were used to quantify effect sizes between IDH1-WT and MT cohorts. Prognostic relevance was assessed using Kaplan-Meier and Cox regression analyses. OCM metabolic rewiring and dependency were validated using in vitro U87 IDH1-WT and IDH1-R132H mutant glioblastoma cell line models. Furthermore, immune microenvironment interactions were evaluated using CIBERSORTx to dissect OCM-associated correlations. Results: Using transcriptional profiling and targeted in-vitro validation, we reveal a distinct two-state metabolic phenotype governed by the OCM network. We demonstrate that while IDH1-MT tumors primarily rely on a suppressed metabolic phenotype, they are supported by compensatory mitochondrial pathways and an aggressive subset aberrantly hyperactivates specific proliferative OCM genes. This high aggregate OCM score was significantly associated with poor overall survival in the IDH1-MT cohort (CGGA HR = 1.61, p < 0.001), identifying an aggressive subset that predominates the favourable IDH mutation status. Functional validation showed aggressive IDH1-MT cells lose their baseline metabolic flexibility with changes in critical OCM genes and exhibit a strict auxotrophic dependence. Further, we also define that OCM rewiring was also associated with immune cell abundance, suggesting high OCM activity correlating with monocyte infiltration and low M2 macrophage polarisation. Conclusion: Our findings offer a framework to identify high-risk patients and propose translational strategies for IDH1-MT tumors that may be refractory to standard IDH inhibitors. Therefore, the study presents a conceptual model for metabolic precision therapy defining OCM metabolic subsets that distinguish indolent, mitochondrial-dependent tumours from aggressive, proliferation-dependent phenotypes in IDH1-MT gliomas.

Pediatric posterior fossa group A (PFA) ependymoma is an aggressive, chemo-resistant brain tumor with a poor 10-year overall survival and no therapeutic options at relapse. Although conventionally classified as immune-cold, the spatial organization and therapeutic relevance of its rare immune infiltrates remain poorly characterized. Here, we present a spatially resolved immune analysis of 14 PFA ependymoma sections using published Visium spatial transcriptomics data analyzed through a multi-stage immune-focused computational framework combining reference-guided deconvolution, functional lymphocyte state scoring, ligand-receptor inference, and {beta}/{gamma}{delta} T cell immunotherapy opportunity scoring. Lymphocyte-associated hotspots were identified in 6 of 14 sections and, among confidently classified hotspots, were dominated by inflammatory-associated and retention-associated transcriptional states rather than cytotoxic or exhausted programs. These hotspots were preferentially confined to myeloid- and mesenchymal-rich tumor zones with near-complete exclusion from epithelial regions; ligand-receptor analysis identified four candidate restriction axes (SPP1-CD44, FN1-integrin, collagen VI-integrin, and APP-CD74). Immunotherapy opportunity scoring revealed heterogeneous and spatially compartmentalized {beta} and {gamma}{delta} T cell recognition landscapes across sections: {beta}T ligand availability and immunosuppressive tone both rose in the mesenchymal compartment, while the two components of {gamma}{delta} phosphoantigen-mediated recognition were spatially and transcriptionally dissociated from one another. Together, these findings reframe PFA ependymoma not as a monolithic immune desert but as a tumor type with spatially compartmentalized, mechanistically tractable immune niches, and provide a generalizable computational strategy for mapping immune architecture and T cell therapy susceptibility in low-infiltrated pediatric CNS tumors.

We present a spatial transcriptomic atlas of 19 pediatric brain tumor patients spanning nine major and rare diagnoses, including seven relapses, revealing their spatial cellular and molecular organization. Each tumor section resolves into 2 - 4 recurrent spatial archetypes across 11 biological themes, with some mirroring developmental lineage patterns - for example, oligodendrocyte-lineage programs in pilocytic astrocytomas. Spatially inferred copy-number analysis identifies relapse-associated putative clones. In one rare embryonal tumor, spatial niches in the primary tumor harboring putative clones colocalized with an archetype enriched for nervous system development and glioblast-lineage programs. In one ependymoma and one pilocytic astrocytoma, relapse-associated putative clones preferentially localized to the vasculature, suggesting regrowth during relapse may be seeded by clonal selection of residual tumor cells within specialized microenvironmental niches. This resource provides an open-access spatially resolved map via an interactive viewer to inform research on pediatric brain tumor ecosystems, relapse biology, and therapeutic strategies.

BackgroundMeningiomas are the most common primary nervous system neoplasm in adults. There are few good cellular models, especially of high grade/malignant meningiomas, to use to identify new therapeutic agents and treatment regimens. The widely available, partially characterized, NF2-wildtype (NF2wt) Grade 3 malignant meningioma cell line IOMM-Lee can help meet this need. MethodsWe generated new data to better characterize IOMM-Lee genomic and mtDNA variants, proliferation rate and colony-forming efficiency and sensitivity to ionizing radiation as a function of ATM kinase activity. A screen of 349 anti-cancer drugs identified multiple, mechanistically distinct clinical use drugs with nanomolar IC50 values and high drug sensitivity prediction scores. ResultsExome sequencing confirmed that IOMM-Lee is NF2wt, and contains a pathogenic TERT-promoter (c.-124C>T) variant. Population doubling times (PDT) were short (19-21 hrs), and colony forming efficiency (CFE) high, of up to 87%. IOMM-Lee is comparatively radiosensitive with a D10 of [~]3.9 Gy, and could be radiosensitized by AZD-1390-mediated ATM kinase inhibition. Thirty-four anti-cancer compounds spanning several mechanistic classes were identified that potently suppressed cell proliferation at sub-micromolar IC50 values with high Breeze 2.0 Drug Sensitivity Scores. Importance of the StudyWe provide new data to better characterize IOMM-Lee, the most widely used cell line model of human Grade 3 malignant meningioma. These data identify and characterize IOMM-Lee genomic alterations and mtDNA variants; quantify growth kinetics and ionizing radiation sensitivity; and identify multiple mechanistically distinct, clinical use drugs with nanomolar IC50 values, high drug sensitivity prediction scores and potential as meningioma systemic therapies. Our data more clearly locate IOMM-Lee in the landscape of genomically-defined meningiomas, and will aid better use of this experimentally tractable cell line model to understand meningioma biology and identify more effective malignant meningioma therapies and treatment regimens. Key pointsO_LIIOMM-Lee lacks NF2 mutations, though is clearly related to but distinct from many other meningiomas and meningioma cell lines. C_LIO_LIIOMM-Lee grows rapidly, is comparatively radio-sensitive, and can be suppressed by several mechanistic classes of anti-cancer agents at clinically achievable, sub-micromolar IC50 values with high Drug Sensitivity Scores. C_LIO_LIThe experimental tractability, simplicity and versatility of IOMM-Lee can facilitate analyses of many aspects of meningioma biology and therapeutic development across a wide range of in vitro, high throughput and in vivo xenograft/organoid protocols. C_LI

Isocitrate dehydrogenase (IDH)-mutant gliomas represent most lower-grade diffuse gliomas in young adults. Although IDH-mutant gliomas initially behave indolently relative to IDH-wildtype counterparts, they undergo inevitable malignant transformation. The mechanisms driving this progression remain poorly defined. We analyzed a unique longitudinal cohort of two patients with IDH-mutant diffuse gliomas, each with matched WHO grade 2, 3, and 4 tumours. Spatial transcriptomics (NanoString GeoMx and 10X Visium), combined with differential expression, spatially variable gene analysis, and gene ontology enrichment, were used to define transcriptional programs underlying progression. Unexpectedly, across both patients, higher-grade tumours demonstrated reduced proliferation at the infiltrative margin as measured by Ki67. Spatial transcriptomic analysis identified an enrichment of invasion-associated genes associated with increasing tumour grade. In an independent bulk RNA-seq cohort, expression of this spatially derived program did not outperform grade-only PFS or OS analysis. These observations underscore the need to develop new metrics that account for spatial evolution that occurs across progression, but escapes detection in bulk analyses and provide the rationale for prioritizing migration-, cytoskeletal- and stress-associated programs for further investigation.

Increasing evidence indicates that neurotransmitter signaling and neuronal interactions are important determinants of glioma biology. However, the clinical and biological significance of serotonin (5-hydroxytryptamine; 5-HT) receptor expression in lower-grade glioma (LGG) remains poorly understood. Here, we investigated G protein-coupled 5-HT receptor genes in LGG using transcriptomic and clinical data from The Cancer Genome Atlas (TCGA-LGG) and Chinese Glioma Genome Atlas (CGGA) cohorts. Initial survival screening identified HTR1A, HTR2A, HTR2C, and HTR6 as the genes most consistently associated with longer overall survival (OS). Multivariable Cox regression further identified HTR2A and HTR6 as independently associated with longer OS after adjustment for age, sex, tumor grade, and IDH/1p19q molecular subtype. Expression of the four genes was preferentially associated with molecular features of less aggressive gliomas, particularly IDH-mutant tumors. Single-cell RNA-sequencing (scRNA-seq) data supported malignant glioma cells as a major source of their expression, while cell-type deconvolution revealed strong positive associations with neuronal enrichment and inverse associations with stromal and immune signatures. Transcriptome-wide co-expression and Gene Ontology analyses showed that all four receptor genes were associated with neuronal and synaptic programs involving neurotransmitter release, synaptic vesicle function, ion channels, and synaptic signaling. These transcriptional programs were particularly coherent in IDH-mutant gliomas and more heterogeneous in IDH-wildtype tumors. Together, these findings identify a subset of 5-HT receptor genes associated with favorable clinical and molecular features in LGG and suggest that their expression may mark a neuronal/synaptic differentiation state, particularly within IDH-mutant gliomas.

BackgroundGlioblastoma (GBM) is characterized by neurological dysfunction caused by tumor cells that interact with and alter neuronal circuits. However, the specific neuronal populations and molecular mechanisms most susceptible to GBM invasion remain poorly understood. MethodsWe created a human tumor-brain organoid model by combining U87 glioblastoma cells with iPSC-derived neural organoids. This system enabled us to study tumor-neural interactions over an extended period under standard temozolomide (TMZ) treatment. We used single-cell transcriptomics to monitor cell-type-specific responses. ResultsOur model recapitulated the diffuse infiltration observed in patients, leading to extensive structural remodeling and a profound loss of neuronal and glial populations. Single-cell analysis revealed that TMZ suppressed proliferative and biosynthetic programs but enriched for stress-responsive, mesenchymal-like, and therapy-adapted tumor states. Notably, GABAergic neurons exhibited the greatest transcriptional vulnerability, with [~]36% (7,499 of 20,659) of genes differentially expressed. Invasion triggered endoplasmic reticulum stress and shut down metabolic, respiratory, synaptic, and ion-homeostatic pathways. Crucially, SLC12A5-expressing GABAergic neurons plummeted from 31% to 12%, accompanied by a sharp decline in KCC2 protein expression. While TMZ partially rescued neuronal metabolic and electron transport chain function, it failed to restore SLC12A5/KCC2 expression or inhibitory signaling. ConclusionsGBM invasion leads to a continued imbalance of chloride in GABAergic networks, and this disruption remains even after undergoing tumor-targeted chemotherapy. This human iPSC-derived tumor-brain organoid platform provides a reliable and scalable system for studying complex tumor-neural interactions and exploring therapeutic approaches that aim to eliminate the tumor while preserving neural function.

Background: Brain-penetrant histone deacetylase inhibitors (HDACi) are promising radiosensitizing agents for glioblastoma (GBM). HDAC inhibitors can impair DNA damage response (DDR) pathways and promote persistent DNA damage. Here, we evaluated whether combined inhibition of HDAC and the DNA repair kinase, ataxia-telangiectasia mutated (ATM), could synergize with radiation (IR) and improve therapeutic efficacy in GBM. Methods: In vitro dose-response assays were performed in patient-derived xenograft (PDX)-derived glioma stem cells (GSCs) with both inhibitors of HDAC (quisinostat, QST) and ATM (AZD1390) with or without IR treatment to assess synergy. Pharmacodynamic responses were evaluated by immunoblotting for histone acetylation, DDR signaling, and DNA damage markers. Transcriptomic analyses were performed to evaluate treatment-associated changes in DNA repair pathways. The combination of QST, AZD1390, and IR was further evaluated in an orthotopic GBM survival study. Results: Combined treatment with QST and AZD1390 produced synergistic radiosensitization in multiple GSC models in vitro. Furthermore, QST combined with IR suppressed transcription of homologous recombination (HR) pathway genes in GSCs, impairing double-strand break repair capacity through an epigenetic mechanism that does not directly inhibit ATM kinase activity. Pharmacodynamic analyses confirmed that QST increased histone acetylation while AZD1390 suppressed ATM signaling, together impairing complementary mechanisms to increase radiosensitivity of GSCs. In an orthotopic GBM model, QST combined with IR significantly prolonged survival compared with IR alone. However, the addition of AZD1390 did not provide a significant survival benefit beyond QST+IR, and AZD1390 combined with IR did not significantly improve survival relative to IR alone. Conclusions: Combined HDAC and ATM inhibition with QST and AZD1390 enhances radiosensitivity in patient-derived GBM cells, mechanistically underpinned by QST-mediated increase in DNA damage and dual disruption of DDR through complementary, non-overlapping mechanisms. However, this in vitro synergy did not confer additional survival benefit beyond QST+IR in an orthotopic GBM model under the dosing conditions tested, suggesting pharmacological limitations with the tumor microenvironment or suboptimal dosing schedules may have constrained in vivo efficacy.

Background: Glioblastoma (GBM) is an aggressive brain malignancy characterized by therapeutic resistance and frequent recurrence. Glioma-initiating cells (GICs), also known as glioma stem cells (GSCs), contribute to these features through self-renewal and resistance to genotoxic stress. Radiation therapy can paradoxically replenish the GIC compartment by inducing stem-like properties in non-stem glioma cells. We investigated whether exosomes mediate bidirectional communication that maintains the balance between GIC and non-stem populations at steady state and following irradiation. Methods: Exosomes were isolated from GIC-enriched gliomaspheres and differentiated monolayer cultures of the patient-derived GBM lines HK-374 and HK-390. Vesicles were characterized by transmission electron microscopy, nanoparticle analysis, and detection of CD63. Recipient cells were exposed to exosomes with or without 4 Gy irradiation. GIC abundance and function were evaluated using a ZsGreen-ornithine decarboxylase degron reporter, sphere-formation assays, and extreme limiting dilution analysis. Exosomal protein cargo was characterized by liquid chromatography-tandem mass spectrometry and Gene Ontology enrichment analysis. Single-cell RNA sequencing was used to evaluate changes in cellular composition upon exosome treatment. Results: Isolated vesicles displayed characteristic exosomal morphology, a mean diameter of 41.6 +/- 14.7 nm, and CD63 expression. Irradiation produced a 12-fold increase in GIC reporter-positive cells among initially reporter-negative differentiated cells. Gliomasphere-derived exosomes significantly and dose-dependently suppressed this radiation-induced phenotype conversion and reduced functional GIC frequency and self-renewal in both patient-derived lines. Conversely, exosomes from GIC-depleted monolayer cultures increased reporter-positive cells two- to three- fold and enhanced the frequency and self-renewal of existing GICs. Proteomic analysis identified 1,796 exosomal proteins, including 336 differentially abundant candidates. Gliomasphere-derived exosomes were enriched in proteins associated with translation, RNA binding, actin organization, cytoskeletal regulation, and intracellular trafficking. Monolayer-derived exosomes were enriched in extracellular-matrix and stem-cell-niche components, including NID2, LAMA5, LAMB1, LAMB2, LAMC1, THBS1, TGFBI, IQGAP3, and APOE. Single-cell transcriptomic analysis showed that gliomasphere-derived exosomes prevented the radiation-induced expansion of neural progenitor-like cells, consistent with suppression of an induced stem-like state. Treatment of gliomaspheres with monolayer-derived exosomes left their overall cellular composition largely but enriched MYC-target, E2F-target, and oxidative-phosphorylation programs, suggesting that increased sphere formation may partly reflect enhanced proliferative capacity. Conclusions: GBM cells use exosomes to establish a bidirectional feedback circuit between stem-like and differentiated tumor-cell compartments. GIC-derived exosomes constrain radiation-induced conversion of non-stem glioma cells into GICs, whereas differentiated-cell-derived exosomes promote a niche that supports GIC maintenance and self-renewal, potentially through expansion of a mixed-vascular-like population containing neurovascular progenitors. Whether exosomal IQGAP3 contributes to the expansion of this GIC population remains to be determined. These findings identify exosome-mediated intercellular communication as a potential mechanism regulating GBM cellular homeostasis, treatment resistance, and recurrence.

Glioblastoma (GBM) is characterized by marked heterogeneity, glioma stem-like cells (GSCs), and resistance to therapy. Because GSCs share features with neural progenitor cells (NPCs), we investigated whether neurodevelopmental programs contribute to their response to irradiation. Transcriptional profiling of four patient-derived GSC lines revealed cell line-specific responses, with radiosensitivity correlating with the magnitude of p53 activation and basal expression of its negative regulator, MDM2. Despite this heterogeneity, radiation consistently activated p53-dependent pathways and suppressed cell-cycle programs. Among these, genes associated with primary hereditary microcephaly (MCPH) that regulate NPC proliferation were coordinately repressed. Single-cell RNA sequencing localized this response to G2/M-cycling cells. FOXM1 was similarly reduced following irradiation, emerged as a candidate regulator of a subset of MCPH genes, and correlated with their expression in GBM tumors. Pharmacological inhibition of FOXM1 reduced expression of selected MCPH genes and enhanced radiosensitivity in U251 cells. Together, these findings identify coordinated suppression of a FOXM1-associated MCPH program as part of the GBM radiation response, while suggesting that the radiosensitizing effects of pharmacological FOXM1 inhibition extend beyond this transcriptional axis.

Diffuse midline glioma is an epigenetically driven disease defined by alterations targeting the histone post-translational modification H3K27me3 resulting in epigenetic rewiring and imposing unique metabolic dependencies. ACVR1-mutations arise in ~25% of DMG H3K27-altered patients and impart a selective dependency on the kinase it encodes (ALK2), however ALK2 inhibitors show modest single-agent efficacy in vivo. In an attempt to better understand the cellular consequences of ALK2 inhibition to identify mechanistically-driven drug combinations, integrated multi-omics analysis was performed and revealed a novel role for ALK2 in cholesterol homeostasis while CRISPR and high-throughput drug screens identified hits targeting cholesterol metabolism as sensitisers to ALK2i. In vivo assessment of ALK2i plus clinically well-tolerated statins revealed a significant increase in the median survival compared to vehicle. Forced differentiation of DMG cells from an oligodendrocyte precursor-like to an astrocyte-like cell-state and led to a significant decrease in ALK2i sensitivity and synergy with statins, which was phenocopied when DMG cells were co-cultured with normal astrocytes. We identify a previously unappreciated role for ALK2 signalling in cholesterol homeostasis, showing cell-state dependency, and identify a rational combinatorial strategy for clinical translation.

Glioma is a fatal tumor of the central nervous system (CNS) with limited therapeutic options. While immune checkpoint inhibitors (ICI) are gaining traction as a novel alternative treatment for human gliomas (HG), clinical trials have yielded mixed results. A proposed major barrier to ICI therapy in cancer is epithelial-mesenchymal plasticity (EMP)-driven intratumoral immunosuppression. However, studying this mechanism is difficult in ex vivo and murine models, which fail to adequately replicate cancer cell-immune cell interactions. Formalin-fixed, paraffin-embedded (FFPE) patient-derived canine glioma (CG) samples represent an attractive alternative approach. Although mechanistic perturbation is unachievable in archival FFPE tissues, CG is notoriously 'cold' immunologically and is actively being investigated as a comparative model of HG. Moreover, the immune microenvironment in CG advantageously develops under exposure to environmental conditions directly shared with humans. Yet, it remains unknown whether CGs harbor heterogeneous niches combining varied plastic phenotypes and immunosuppressive populations. Defining the immune landscape of CG in relation to EMP is therefore critical to determining its potential as a comparative model for immunotherapy response in HG. By combining standard histology, immunohistochemistry, and tissue microarray-based spatial transcriptomics, we analyzed 30 low-grade (LGr) and high-grade (HGr) FFPE CG cases (n=10 cases/subtype): astrocytomas (4xLGr, 6xHGr), oligodendrogliomas (1xLGr, 9xHGr), and undefined gliomas (3LxGr, 7xHGr). All CG subtypes harbored heterogeneous immunosuppressive niches associated with varied EMP phenotypes. Astrocytomas exhibited a more-mesenchymal identity correlated with recruitment of tumor-associated macrophages (TAMs). Oligodendrogliomas displayed a strong stem-like signature and uniquely upregulated a FOXP3/LAG3/SNAI1 triad, positioned directly at the interface of immunosuppression and EMP. Across all CG subtypes, a more-mesenchymal phenotype co-occurred with TAMs, and intratumoral T-cell dysfunction and exhaustion. We conclude that CG replicates the EMP-immunosuppression heterogeneity seen in humans. Importantly, our results emphasize the existence of subtype-specific mechanisms of EMP and immune evasion, underscoring the major relevance of subtyping for translational applications.