Neuro-Oncology

BackgroundTelomerase reactivation, a hallmark of many cancers, is associated with expression of its catalytic subunit, hTERT. However, the prognostic significance of telomere maintenance mechanisms in pediatric medulloblastoma remains poorly defined. MethodsIn this multi-institutional retrospective study of telomerase expression and hTERT regulation in newly diagnosed children with medulloblastoma, hTERT and MYC expression were assessed by qRT-PCR, normalized to non-neoplastic brain control samples. hTERT promoter methylation was analyzed using quantitative pyrosequencing and Illumina 450k methylation array. Cox proportional-hazard regression analyses evaluated the association of hTERT expression with progression-free survival (PFS) or overall survival (OS). Spearman correlation and Kruskal-Wallis tests correlated hTERT promoter methylation and expression and assessed variations among medulloblastoma subgroups, respectively. ResultsAmong 74 patients with available hTERT expression and outcome data, higher expression was associated with worse OS (HR=1.22, 95% CI: 1.01-1.47, p=0.036) and PFS (HR=1.17, 95% CI: 1.00-1.37, p=0.051) after adjusting for subgroup. Similar results were obtained when adjusting for metastatic status. Group 3 patients had the highest hTERT expression (p=0.001). Pyrosequencing data were available for 61 patients and 450k methylation array data for 292 patients. hTERT promoter was differentially methylated across subgroups with WNT followed by group 3 demonstrating the highest methylation on 450k (p<0.0001), findings that were confirmed by pyrosequencing. hTERT promoter methylation positively correlated with hTERT expression (Spearman correlation=0.42, p=0.02 by 450k and 0.34, p=0.007 by pyrosequencing). No significant correlation was observed between hTERT and MYC expression. ConclusionElevated hTERT expression is associated with worse PFS and OS in medulloblastoma across subgroups, supporting telomerase inhibition as a potential therapeutic strategy.

BackgroundThe Netrin-1 dependence receptor pathway plays critical roles in neural development, but its expression landscape and prognostic significance in glioblastoma (GBM) remain poorly characterized. MethodsSingle-cell RNA-seq data from 148,019 cells across 34 tumors (Neftel et al., 2019) were analyzed to map Netrin-1 pathway gene expression across GBM cellular states. Differential gene expression and pathway enrichment analyses were performed on NEO1-defined subpopulations. Bulk RNA-seq survival analysis was conducted across three independent GBM cohorts TCGA (n=106), CGGA mRNAseq_325 (n=137), and CGGA mRNAseq_693 (n=237), totaling 480 patients. Primary analysis used continuous Cox regression (per-SD hazard ratios); meta-analysis employed fixed-effects inverse-variance weighting. ResultsIn GBM single-cell data, Netrin-1 pathway genes showed state-specific enrichment --NEO1, DCC, NTN1, and RGMB were predominantly expressed in oligodendrocyte-precursor (OPC) and neural-progenitor (NPC) states. Cells positive for NEO1 were enriched for neural differentiation programs (nervous system development, p=9.6x10-; Axon Guidance, p=2.8x10-), whereas NEO1-negative cells were dominated by ribosomal/translational and immune activation programs. In the 3-cohort survival meta-analysis, NTN1 (Netrin-1 ligand) emerged as the sole gene reaching meta-analytic significance as a risk factor (Meta HR=1.163 per SD, 95% CI 1.056-1.281, p=0.0021, I{superscript 2}=0%, 3/3 cohorts concordant), while DCC and RGMB showed directionally consistent protective trends (DCC: Meta HR=0.938, 95% CI 0.858-1.025, p=0.156; RGMB: Meta HR=0.979, 95% CI 0.881-1.087, p=0.686; both 3/3 cohorts concordant). NEO1 itself did not independently predict survival (Meta HR=1.008, 95% CI 0.885-1.147, p=0.910). After Bonferroni correction for 10 genes tested (threshold p<0.005), only NTN1 met strict significance. In exploratory sex-stratified analysis of a single cohort (CGGA 693, n=237), NEO1 and NTN1 exhibited female-specific risk enhancement (NEO1: HR=1.417, p=0.014; NTN1: HR=1.249, p=0.019), with minimal effects in males. UNC5B showed context-dependent risk in MGMT-unmethylated tumors (HR=1.331, p=0.037). These sex-dimorphic findings require independent validation. ConclusionsThe Netrin-1 pathway exhibits divergent prognostic trends in GBM, with NTN1 as a risk factor and DCC trending toward protection--consistent with the dependence receptor model. These findings, which should be interpreted as hypothesis-generating, nominate NTN1 as a candidate therapeutic target and highlight the potential importance of sex-stratified evaluation in future Netrin-1-directed trials. Independent replication in larger cohorts is warranted.

Oligodendroglioma is a primary central nervous system tumor classified by the presence of isocitrate dehydrogenase (IDH) mutations and codeletion of 1p/19q. Here we describe the generation of an IDH-mutant 1p/19q-codeleted oligodendroglioma mouse model using in utero electroporation. We identified IDH1R132H, PIK3CAE545K, CicKO, Fubp1KO and Cdkn2aKO as the optimal combination (termed OligoCdkn2a) to drive fully penetrant tumors that histologically resemble human grade II/III IDH-mutant, 1p/19q-codeleted oligodendroglioma. Replacing Cdkn2a with Trp53 loss in this mouse model shifted tumor histology towards high grade astrocytoma. OligoCdkn2a tumors displayed metabolic and transcriptional changes associated with IDH and CIC mutations, and single cell sequencing identified a bias towards oligodendrocyte differentiation compared to an IDH wild-type glioblastoma mouse model. OligoCdkn2a tumors represent the first mouse model system to recapitulate the genetic, histological and transcriptional features of human IDH-mutant 1p/19q-codeleted oligodendrogliomas, offering a platform to further dissect tumor biology and test new therapeutic strategies.

Diffuse intrinsic pontine glioma (DIPG) is a devastating pediatric brain tumor with limited treatment options. Emerging evidence indicates infiltration of tumor-associated macrophages (TAMs) within tumor sites, accompanied by an immunosuppressive tumor microenvironment (TME). However, the mechanisms underlying macrophage recruitment and communication between TAMs and other cellular compartments within brain tumors remain poorly understood. Bulk RNA sequencing of 26 DIPG autopsy specimens with matched normal brain tissue, single-cell RNA sequencing data from eight DIPG patients integrated with public pediatric high-grade glioma (pHGG) datasets, and in vitro transwell and flow cytometry assays collectively indicated that DIPG tumors actively recruit monocytes through chemokine-mediated mechanisms. The chemokine expression of tumor cells is driven by a mesenchymal-like (MES-like) lineage state rather than histone mutations, as evidenced by significant correlation between MES-like lineage scores and chemokine expression scores across 46 pHGG cell lines. CellChat analysis identified APP-CD74 signaling as a prominent tumor cell-TAM interaction pathway, supported by immunofluorescence validation. Notably, APP expression was significantly reduced in DIPG tumor tissues compared with normal brain tissue at both the RNA and protein levels. Recombinant APP stimulation of THP-1-derived macrophages induced a robust proinflammatory response, including upregulation of M1-like markers, enrichment of interferon-related pathways, and elevated secretion of inflammatory cytokines. Collectively, these findings indicate that APP suppression in tumors attenuates the antitumor activity of TAMs and promotes an immunosuppressive microenvironment. Furthermore, protein modeling and docking analyses identified the APP-CD74 binding interface, providing a structural basis for therapeutic targeting.

Background Platinum refractory paediatric germ cell tumours (GCTs) carry a poor prognosis, with five year survival below 30% and no validated molecular stratification tool. The biological mechanisms underlying platinum resistance in this population remain poorly defined, limiting the development of targeted therapeutic strategies and early warning biomarkers. Methods We performed integrated plasma multi-omics profiling in 105 pediatric GCT patients (54 refractory and 51 treatment naive) using data-independent acquisition proteomics, untargeted metabolomics, and exploratory lipidomics. Candidate biomarkers were validated using ELISA and spatial multiplex immunofluorescence. Predictive models were constructed using logistic regression and evaluated by ROC analysis, calibration, and decision-curve analysis. Results Multiomics integration has revealed the coordinated dysregulation of sphingolipid metabolism, extracellular matrix remodeling, and immune checkpoint signaling in refractory diseases. Lipidomic analysis demonstrated a significant depletion of sphingolipid associated species, including lysophosphatidylserine, lysophosphatidylethanolamine, and phosphatidylserine. Proteomic profiling identified the upregulation of LAG3 and HTRA1, which was validated by ELISA. Multiplex immunofluorescence demonstrated the spatial enrichment of exhausted CD8 + LAG3 T cells adjacent to CK-PAN tumor cells in refractory tumors. A plasma biomarker panel integrating LAG3, HTRA1, and AFP showed improved discrimination of refractory disease (AUC = 0.821) compared with AFP alone. Conclusions Our study identified a sphingolipid HTRA1 LAG3 immune evasion axis as a defining molecular feature of refractory pediatric germ cell tumors and proposed a clinically applicable plasma biomarker panel for early risk stratification.

Background: Extent of resection remains central to meningioma management, yet Simpson grading is subjective and may not reflect measurable postoperative residual disease. We compared surgeon-reported Simpson grade, report-derived radiological grading, and residual tumour volumetry across a multicentre cohort. Methods: We performed a retrospective study across two tertiary neurosciences centres comprising four hospitals, including patients undergoing primary cranial meningioma resection from 2006 to 2025. Postoperative magnetic resonance imaging (MRI) reports were harmonised using weakly supervised natural language processing based on term frequency-inverse document frequency (TF-IDF) and a linear support vector machine classifier. Residual tumour volume was segmented from contrast-enhanced postoperative MRI and log-transformed. Concordance between Simpson and radiological gross-total/subtotal resection classification was assessed using absolute agreement and prevalence-adjusted bias-adjusted kappa (PABAK). Cox models assessed recurrence-free survival, with bootstrap validation and anatomical and scan-timing sensitivity analyses. Results: Among 912 patients, recurrence or residual progression occurred in 281. Surgical-radiological agreement was substantial but imperfect (absolute agreement 74%; PABAK 0.61), with lower agreement in skull-base and parafalcine-parasagittal tumours. In adjusted models, recurrence hazard increased with Simpson grade (hazard ratio 1.54, 95% confidence interval 1.37-1.72), radiological grade (1.92, 1.68-2.20), and log-transformed residual volume (1.20, 1.16-1.24; all p<0.0005). Optimism corrected concordance increased from Simpson grade to radiological grade and log-volumetry (0.692, 0.733, and 0.748), with this ranking preserved across sensitivity analyses. Conclusions: Imaging-based postoperative residual disease measures outperformed Simpson grade. TF-IDF-assisted report-derived grading provides a scalable bridge to volumetry, while quantitative residual volume offers the strongest prognostic representation.

BackgroundConvection-enhanced delivery of topotecan enables sustained local chemotherapy for recurrent glioblastoma and was associated with reduced tumor proliferation in our previous phase 1B clinical trial. That trial incorporated a paired pre- and post-treatment biopsy design - rare in glioblastoma clinical research - enabling tissue-anchored assessment of drug effect without reliance on radiographic or survival endpoints, which are notoriously difficult to interpret in this disease. However, the cellular and molecular consequences of local chemotherapy within the treated tumor microenvironment remain incompletely defined. MethodsWe integrated paired, MRI-localized pre- and post-treatment biopsies from a first-in-human CED-topotecan trial (n=5), leveraging the paired biopsy architecture, in which each patient serves as their own control and post-treatment specimens are spatially annotated relative to the MRI-defined infusion zone, to generate tissue-based evidence of drug effect without requiring large patient numbers. These biopsies were integrated with complementary experimental models, including a time-resolved syngeneic murine glioma CED model, acute patient-derived glioblastoma slice cultures, and in vitro human microglial and glioma systems. Clinical biopsies were analyzed by bulk RNA-seq, cell-type deconvolution, and multiplex immunofluorescence. Murine tumors were analyzed by survival, immunofluorescence, and single-cell RNA-seq; patient-derived slice cultures were profiled by single-cell RNA-seq. ResultsIn paired human biopsies, CED-topotecan induced spatially restricted transcriptional remodeling within the infusion zone, characterized by suppression of proliferative tumor programs and enrichment of inflammatory, interferon, hypoxia, and mesenchymal signatures. Cell-type deconvolution and immunofluorescence linked this response to myeloid remodeling, including enrichment of monocyte-derived tumor-associated macrophage states, increased MARCO-positive myeloid populations, and pH2AX-positive genotoxic stress within Iba1-positive myeloid cells. In the murine CED model, topotecan prolonged survival and reduced tumor cellularity, while also inducing inflammatory and DNA-damage programs in tumor-associated macrophages that evolved by 7-days toward hypoxia, angiogenesis, TGF-{beta} signaling, and mesenchymal/tissue-remodeling programs. Human slice culture and in vitro microglial systems confirmed stress-coupled inflammatory and DNA-damage responses in human myeloid cells. ConclusionsLocal topotecan delivery produces spatially structured tumor cytotoxicity together with a genotoxic, stress-coupled inflammatory myeloid response that evolves toward mesenchymal macrophage remodeling. By integrating paired clinical biopsies with time-resolved and mechanistic experimental models, this study provides a framework for understanding how local chemotherapy reshapes the glioblastoma microenvironment and for future studies evaluating dose, schedule, treatment duration, and combination strategies. These findings demonstrate that paired, spatially annotated tissue sampling from small, precisely characterized clinical cohorts can yield mechanistic insight that conventional radiographic and survival endpoints cannot provide, and support tissue-based response assessment as the appropriate paradigm for evaluating novel locoregional therapies in glioblastoma.

IntroductionCraniopharyngioma (CP) comprises two distinct histological subtypes, adamantinomatous craniopharyngioma (ACP) and papillary craniopharyngioma (PCP), which are often challenging to distinguish preoperatively. Approximately 95% of PCP harbor the BRAF V600E mutation, whereas ACP lacks this alteration, making PCP uniquely sensitive to BRAF and MEK inhibition. However, in the absence of a reliable preoperative classification strategy, targeted therapy has been limited to recurrent disease or to cases with histological confirmation. This study aims to describe and prospectively evaluate a pragmatic preoperative classification strategy and short-course neoadjuvant BRAF and MEK inhibition followed by surgery in newly diagnosed, preoperatively classified PCP. Methods and analysisThis is a prospective, single-arm, open-label study. Patients with newly diagnosed craniopharyngioma will be screened using an integrated preoperative strategy combining imaging-based prediction and selective cerebrospinal fluid (CSF) cell-free DNA testing for BRAF V600E in indeterminate cases. Twelve participants preoperatively predicted as PCP and BRAF V600E positive will receive dabrafenib 150 mg twice daily plus trametinib 2 mg once daily for up to three 28-day cycles, followed by transnasal endoscopic surgery. Assessments are scheduled at days 7, 14, 28, 56, and 84 until surgery. The primary endpoint is objective response rate, assessed by contrast-enhanced MRI using RANO 2.0 criteria. Secondary outcomes include progression-free survival, local disease control, endocrine outcomes of the hypothalamic-pituitary-adrenal and hypothalamic-pituitary-thyroid axes, visual and cognitive outcomes, postoperative diabetes insipidus, surgical complexity, and concordance between the preoperative classification strategy and postoperative pathology and BRAF V600E status. Exploratory analyses will evaluate treatment-related changes in tumor vascularity, tissue characteristics, and post-treatment molecular alterations in tumor tissue. Ethics and disseminationThis protocol has been approved by the Ethics Committee of Huashan Hospital, Fudan University (KY2024-028). Written informed consent will be obtained from all participants. Results will be disseminated through peer-reviewed publications and scientific conferences. Trial registration numberChiCTR2400081636 STRENGTHS AND LIMITATIONS OF THIS STUDYO_ST_ABSStrengthC_ST_ABS[tpltrtarr] This study proposes an integrated, clinically applicable preoperative strategy that combines imaging-based prediction with selective cerebrospinal fluid cell-free DNA analysis to identify papillary craniopharyngioma (PCP) prior to surgery. [tpltrtarr]It prospectively evaluates short-course neoadjuvant BRAF and MEK inhibition in newly diagnosed PCP, addressing a clinically relevant gap in current management. [tpltrtarr]Standardized, multidimensional assessments are performed across the neoadjuvant, perioperative, and early postoperative periods, capturing radiographic, surgical, endocrine, visual, and cognitive outcomes. Limitation[tpltrtarr] The single-arm, open-label design without a surgical control group limits direct comparison with upfront surgery. [tpltrtarr]Despite the integrated prediction strategy, preoperative misclassification cannot be excluded entirely.

Cerebellum tissue invasion and dissemination are major drivers of recurrence and metastatic spread in medulloblastoma (MB), yet no invasion-inhibitory therapy is currently available. The serine/threonine kinase MAP4K4 is highly expressed in MB and promotes invasive behavior downstream of growth factor signaling, while its physiological postnatal downregulation suggests that disrupted developmental control may contribute to tumor pathogenesis. Here, we investigate pharmacological targeting of MAP4K4 using famlasertib, a CNS-penetrant and neuroprotective MAP4K inhibitor, as a strategy to suppress invasion in MB. Using 3D invasion assays, quantitative live-cell microscopy, and phospho-proteomics, we demonstrate that famlasertib markedly reduces invasive behavior and single-cell motility of MB cells. Zebrafish larval and tissue models further confirm anti-invasive efficacy without detectable developmental toxicity at effective concentrations. Mechanistically, MAP4K inhibition alters kinase signaling linked to cytoskeletal remodeling, leading to suppressed F-actin dynamics, increased cell clustering, and enhanced cortical accumulation of tight junction protein 1 (TJP1). Collectively, our findings confirm MAP4Ks as a therapeutic targetable regulators of MB invasion and establish famlasertib as a candidate migrastatic agent that restrains tumor cell dissemination while preserving developmental integrity.

Glioblastoma (GBM) develops within a complex tumor ecosystem whose temporal dynamics remain poorly understood. Here, we performed longitudinal single-cell RNA sequencing and spatial transcriptomics across multiple timepoints in two widely used murine GBM models - CT2A and GL261 - which differ markedly in aggressiveness and response to immune checkpoint blockade. Tumor cell transcriptomes revealed model-specific programs: CT2A cells progressively upregulated epithelial-mesenchymal transition (EMT), non-classical MHC Class I, and progressively, hypoxia response pathways, resembling the human mesenchymal GBM cell state, while GL261 cells exhibited MHC Class II expression and developmental signatures resembling oligodendrocyte progenitor and astrocytic states. Ligand-receptor interaction analyses identified thrombospondins (Thbs1, Thbs2) and osteopontin (Spp1) as CT2A-specific tumor ligands mediating tumorigenic interactions with immune cells, with downstream targets enriched for EMT and TGF-{beta} pathways. Conversely, the GL261 model presented a differential potential to engage neuronal and perivascular guidance networks, with Glutamate and L1 cell adhesion molecule (L1cam) as lead signaling partners. The CT2A immune compartment exhibited progressive microglia-to-macrophage phenotypic conversion, enhanced macrophage infiltration driven by Spp1, and elevated T cell exhaustion, while GL261 maintained a distinct adaptive immune communication hub via MHC class II-CD4 signaling. Elevated THBS1, THBS2, and SPP1 expression correlated with poor survival in human GBM datasets. Together, these findings reveal divergent tumor-immune ecosystems in CT2A and GL261 that recapitulate distinct aspects of human GBM, with implications for therapeutic targeting.

BackgroundGlioblastoma is an aggressive and incurable brain tumor. Clinical trials of immune checkpoint inhibitors showed no clinical benefit in glioblastoma when given after surgery. However, a clinical trial in which PD1 inhibition was given prior to second surgery did show pharmacodynamic evidence for activity. This suggests the possibility that immune checkpoint inhibitors may be more effective in a setting where large tumors are present. Here we have studied immune responses to large tumors in an autochthonous mouse model of glioblastoma. MethodsGlioblastoma was induced by transfection with oncogenic plasmids injected directly into the lateral ventricle of neonatal mice. Immune responses were assessed using a combination of spectral flow cytometry and immunohistochemistry. ResultsThere was a marked immune response to large tumors, with significant increases in CD4 T cells and dendritic cells. T cell changes occurred primarily at leptomeningeal/perivascular border sites. A large proportion of CD4 T cells expressed PD1 and half of these were regulatory T cells. NK cells were also increased in mice with large tumors, but were predominantly in immature states. The mouse model accurately recapitulates the formation of palisading necroses. These contain apoptotic cells and avidly recruit myeloid cells that are induced to express large amounts of TGF{beta}. ConclusionsLarge glioblastoma tumors generate a border site population of PD1 positive T cells that may explain the pharmacodynamic response in neoadjuvant trials, and a palisading necrosis-driven immunosuppressive mechanism that may explain why responses are insufficient to provide a significant clinical benefit. KEY POINTSThe SB mouse model accurately recapitulates immune features of human glioblastoma Large tumors induce a significant border site immune response Palisading necroses in large tumors counter this with a strong immunosuppressive response IMPORTANCE OF STUDYImmune checkpoint inhibitors have not shown efficacy in glioblastoma when used post-surgery, but do show pharmacodynamic activity when used in patients prior to second surgery (i.e. neoadjuvant). This suggest the possibility that immune checkpoint inhibition is more effective when large tumors are present. Using a clinically-relevant autochthonous mouse model, we show here that large tumors induce an immune response that is evident in leptomeningeal border sites. Large tumors in this mouse model also generate palisading necroses, a well-known diagnostic feature in glioblastoma tumors. These palisading necroses generate large amounts of TGF{beta}, providing a mechanism by which large tumors can suppress border site immune responses. This further supports the concept that palisading necroses are drivers of glioblastoma malignancy and suggests novel strategies to enhance responses to immune checkpoint inhibition in this cancer.

Background: Reirradiation (reRT) is increasingly offered following progression in diffuse intrinsic pontine glioma (DIPG) and diffuse midline glioma (DMG), though optimal patient selection remains a challenge. This study evaluated clinical outcomes after reRT in a contemporary cohort of patients with DIPG/DMG. Methods: Patients <26 years old with DMG/DIPG treated with radiation therapy between 2011-2025 were retrospectively reviewed. Primary endpoints included overall survival (OS2) and progression-free survival (PFS2), measured from first progression, and change in neurologic symptoms after reRT. Survival was estimated using Kaplan Meier methods, with Cox proportional hazards modeling for prognostic factors. Results: Fifty eight patients were included; 37 (63.8%) underwent reRT. Tumors were predominantly pontine (74.1%). ReRT was associated with improvement in motor function (51.4% vs. 9.5%, p=0.002), cranial nerve function (29.7% vs. 4.8%, p=0.044), and gait ataxia (35.1% vs. 9.5%, p=0.059). Median OS2 and PFS2 were improved with reRT (OS2: 9.67 vs. 2.57 months, p<0.001; PFS2: 5.63 vs. 1.57 months, p<0.001). OS2 was independently associated with reRT (HR 0.27, p<0.0001), pontine location (HR 2.94, p=0.004), and steroid use at progression (HR 4.12, p=0.001). PFS2 was independently associated with reRT (HR 0.23, p < .0001) and distant pattern of failure (HR 2.83, p=.037). Among reRT patients, non-pontine location was associated with improved OS2 (p=0.02), and local failure was associated with improved PFS2 (p=0.003). Conclusion: ReRT was associated with neurologic improvement and prolonged survival. Patients with non-pontine tumors or local-only failure might derive the greatest benefit. Prospective studies are warranted to define optimal dose/fractionation and refine patient selection.

In pediatric brain tumors medulloblastoma (MB) and diffuse midline glioma (DMG), tumor-associated myeloid cells (TAMs) support malignant progression by secreting paracrine growth factors and suppressing local immune function. We studied the potential for reversing this cancer-supportive phenotype by stimulating TAM pathogen receptors using ResiPOx, a brain-permeant, polyoxazoline nanoparticle formulation of the TLR7/8 agonist resiquimod. ResiPOx showed blood-brain barrier penetration and anti-tumor efficacy, extending progression-free survival (PFS) in mice with MB and DMG. Integrated cellular and molecular analysis including scRNA-seq showed that ResiPOx expanded TAM populations and reprogrammed TAMs toward anti-tumoral states, blocking paracrine IGF1 signaling and inducing local cytokine signaling and phagocytosis of tumor cells. In rhesus macaques, systemic ResiPOx was well tolerated and induced brain transcriptional patterns that resembled ResiPOx responses in DMG and MB mouse models, indicating effects in non-human primates that highlight translational potential. Our data show that ResiPOx reshapes the brain tumor microenvironment to inhibit tumor growth. As a systemically administered, brain penetrant immunomodulator, ResiPOx is able to reach multifocal and unresectable brain tumors, including MB and DMG.

To elucidate the early mechanisms underlying the long-term neuroprotective effect of FLASH-RT in the normal brain, spatial transcriptomics (Nanostring) were performed after whole-brain irradiation of C57BL/6J mice with either 1 or 3 fractions of 10 Gy at 5.6x106 Gy/s (1 pulse-FLASH) or at conventional dose-rate 0.1 Gy/s. FLASH -RT induced a distinct transcriptomic signature in the CA3 and DG neurons, with upregulation of genes encoding glutamate receptors, involved in calcium signaling, long-term potentiation and mitochondrial OXPHOS. Early transcriptional upregulation of Gria gene translated into increased AMPAR protein levels at 48h in the DG and CA3 region and sustained higher AMPAR expression at 2 and 4 weeks post-FLASH. These findings support a durable activation of AMPAR. We propose a mechanism to explain FLASH-induced neuroprotection initiated by early calcium influx and subsequent sustained expression of glutamate receptor AMPAR in neurons and/or neural progenitors of the CA3, potentially contributing to long-term cognitive sparing. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/725423v1_ufig1.gif" ALT="Figure 1"> View larger version (59K): org.highwire.dtl.DTLVardef@1ae125forg.highwire.dtl.DTLVardef@138357aorg.highwire.dtl.DTLVardef@13f128dorg.highwire.dtl.DTLVardef@1db1cf6_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIFLASH-RT induces a stronger transcriptional response in the hippocampus than the cortex. C_LIO_LIFLASH-RT induces calcium signaling, LTP and mitochondrial OXPHOS genes. C_LIO_LIEarly AMPAR upregulation leads to sustained protein expression. C_LIO_LIFLASH-RT induces a AMPAR-dependent signaling program in CA3 neurons. C_LI

Glioblastoma is a highly aggressive brain tumour with poor prognosis, whose aetiology, progression, and therapeutic resistance remain incompletely understood. While the microbiota-gut-brain axis has emerged as a key regulator of neurological disorders, its role in glioblastoma biology and treatment response is still largely unexplored. Using a clinically relevant immunocompetent murine model combining glioblastoma stem cell implantation, dextran sodium sulfate-induced gut inflammation, and a full Stupp-like therapeutic protocol, we investigated bidirectional gut-brain communication in glioblastoma. Tumour growth and recurrence were monitored by bioluminescence imaging, tumour transcriptomic profiles were analysed by RNA sequencing, and brain and colon tissues were subjected to histological and molecular analyses. Gut microbiota composition was assessed by 16S rRNA sequencing, while systemic metabolites and cytokines were quantified in plasma. Cross-compartment association bioinformatic analyses were performed to correlate multi-organ readouts. Gut inflammation enhanced glioblastoma growth and promoted tumour recurrence following therapy. Tumour progression was associated with increased infiltration of immunosuppressive macrophages, whereas recurrence correlated with elevated oxidative DNA damage. Remarkably, glioblastoma exerted systemic immunomodulatory effects, attenuating intestinal and systemic inflammatory responses, and induced profound remodelling of gut microbiota composition and predicted metabolic function, including enrichment of Akkermansia and depletion of Lactobacillus. Systemic metabolic profiling was investigated as a route of communication within the gut-brain axis and revealed adaptations in DSS-treated mice associated with tumour burden and therapeutic response. Multi-compartment correlation and multivariable association analyses identified specific bacterial genera and circulating metabolites associated with tumour volume, intestinal inflammation, and genomic instability. These findings uncover a dynamic, bidirectional microbiota-gut-brain axis in glioblastoma and identify intestinal inflammation as a critical determinant of tumour progression and therapeutic outcome. Targeting gut disturbances and microbiota-associated metabolic pathways may represent novel strategies to modulate glioblastoma aggressiveness and treatment response.

Glioblastoma (GBM) is an aggressive primary brain tumor associated with a median survival of approximately 15 months following diagnosis. Current standard-of-care treatment includes surgical resection followed by radiotherapy and chemotherapy with the DNA-alkylating agent temozolomide (TMZ). However, tumor recurrence in a therapy-resistant state remains a major driver of poor patient outcomes. To investigate the molecular mechanisms underlying TMZ resistance, we generated in vitro models of acquired resistance by exposing initially TMZ-sensitive GBM cells to escalating doses of TMZ. Transcriptomic and chromatin accessibility profiling revealed extensive remodeling of DNA damage response (DDR) and DNA repair pathways that favored protection against TMZ-induced genotoxic stress. Although upregulation of O-6-methylguanine-DNA methyltransferase (MGMT) emerged as a dominant determinant of resistance in our models, the data suggested that additional adaptive resistance mechanisms contribute to the resistant phenotype. To identify targetable epigenetic dependencies associated with TMZ resistance, we performed a chemical screen using an epigenetic probe library. This screen identified multiple histone deacetylase (HDAC) inhibitors that selectively impaired the viability of TMZ-resistant cells, either as monotherapy or in combination with TMZ. Among these, HDAC6-selective inhibitors, including Ricolinostat, were particularly effective at inducing cell death in TMZ-resistant GBM models. Mechanistically, HDAC6 inhibition reduced the expression of key DDR-associated genes, while MGMT responses varied depending on cellular context and treatment duration. Furthermore, pharmacological inhibition and loss-of-function studies demonstrated that targeting HDAC6 could restore TMZ sensitivity by altering the balance of DNA repair pathway activity, potentially acting as a compensatory mechanism for MGMT-mediated resistance. Collectively, our findings identify HDAC6 as an epigenetic vulnerability in acquired TMZ-resistant GBM and support the therapeutic potential of HDAC6 inhibition as a strategy to overcome TMZ resistance in glioblastoma patients.

Dexamethasone is widely used to control cerebral edema and inflammation in glioblastoma, but its benefits are limited by systemic toxicities and adverse prognostic associations. We evaluated local administration of dexamethasone via convection-enhanced delivery (CED) to maximize intratumoral anti-inflammatory effects by increasing local corticosteroid exposure while minimizing systemic exposure. In two glioma mouse models, continuous intraparenchymal infusion of dexamethasone was well tolerated with no adverse effects. Pharmacokinetic analyses supported preferential intratumoral distribution and reduced systemic exposure with CED compared with systemic dosing. Single-nucleus RNA sequencing (snRNA-seq) and immunohistochemistry showed attenuation of glioma-associated inflammation with downregulation of reactive microglial/macrophage programs and reduced tumor-infiltrating myeloid cells with a morphology consistent with a less activated state. Experiments in human induced pluripotent stem cell (iPSC)-derived microglia confirmed that dexamethasone directly suppresses inflammatory gene expression, indicating a conserved mechanism across species. This inflammatory suppression was recapitulated in both immortalized microglial (HMC3) and macrophage (THP1) cell lines. These findings suggest that localized dexamethasone delivered by CED reprograms the glioma immune microenvironment and achieves control of inflammation without the systemic adverse effects associated with standard systemic dexamethasone therapy. This clinically translatable strategy may improve symptom management and provide a platform for integrating local immunomodulation with future glioblastoma therapies.

Background. Meningiomas exhibit well-established hormonal biology, yet no study has examined whether myeloid immune infiltration interacts with estrogen-responsive transcription in this tumor type. Methods. We applied three-method consensus immune deconvolution (EPIC, MCPcounter, CIBERSORTx) to 968 harmonized meningioma RNA-seq transcriptomes from five public datasets, stratified by Thirimanne et al. (2024) transcriptomic subtypes. Competitive gene set enrichment compared macrophage-high versus macrophage-low tertiles with sex-adjusted, purity-adjusted, and method-independent sensitivity analyses. Survival modeling tested both total macrophage burden and a decomposed microglia-to-macrophage ratio validated against single-cell ground truth (pseudo-bulk r = 0.77). Results. Macrophage-high tumors showed significant suppression of estrogen response gene sets (FDR = 4.9 x 10-5) despite paradoxical ESR1 upregulation (log2FC = +0.40, FDR = 2.5 x 10-26) and PGR downregulation (log2FC = -0.34, FDR = 2.7 x 10-3), indicating post-receptor transcriptional disruption. This signal strengthened after sex adjustment (FDR = 1.9 x 10-6) and was confirmed across a multi-layer sensitivity battery (eleven analyses including reference-matrix-independent, purity-adjusted, rotation-based self-contained, and empirical-null tests; all FDR < 3 x 10-4 in the relevant convergent tests). Myeloid infiltration was strongly subtype-dependent (Kruskal-Wallis p = 7.4 x 10-16) but grade-independent (p = 0.399), with CSF1R enriched in the macrophage-dominant Cluster B. Neither total macrophage score (HR = 0.90, p = 0.53; N = 102) nor a decomposed microglia/macrophage ratio (HR = 0.92, p = 0.46; N = 101) predicted recurrence-free survival. Conclusions. The pre-registered primary endpoint - macrophage infiltration score predicting recurrence-free survival - was not supported; the estrogen-immune dissociation emerged from secondary exploratory gene-set analysis and requires independent validation. Macrophage-infiltrated meningiomas exhibit a previously unreported dissociation between maintained ESR1 expression and suppressed estrogen-responsive transcription, with implications for hormonal therapy stratification.

Background: Meningiomas are the most common primary intracranial tumors in adults, and volumetric assessment increasingly guides surveillance and treatment decisions. Automated segmentation could enable standardized volumetry but requires robust validation. Purpose: To develop a fully automated three-dimensional deep learning model for meningioma segmentation on multiparametric MRI, and to evaluate segmentation accuracy, external generalizability, failure modes, radiologist-rated clinical plausibility, and workflow feasibility. Methods: From 2024 to 2026, this retrospective study trained a custom 3D nnU-Net residual encoder model. Expert segmentations covered enhancing tumor (ET), tumor core (TC), and whole tumor (WT). Dice similarity coefficient (DSC) was the primary metric. External validation used an independent single-institution dataset (n = 310 intracranial cases) with incomplete MRI protocols. Failure modes, model equity, and inference time were assessed. A blinded multi-rater study (10 radiologists; 510 cases) rated TC segmentations using a 0-10 Likert scale, analyzed with linear mixed-effects models. Results: Model training used the BraTS Meningioma 2023 dataset (n = 1000; mean age 60.2 {+/-} 14.5; 705 female). In cross-validation, mean DSC was 0.939 for ET, 0.937 for TC, and 0.921 for WT. In external validation, mean DSC was 0.872 for TC and 0.842 for WT, despite heterogeneous protocols and incomplete sequences. Predicted TC volumes correlated strongly with reference volumes in cross-validation (r = 0.995) and external validation (r = 0.971). Most common failure modes were skull base and intraosseous tumors with performance equitable across demographic subgroups. Mean inference time was 1.2 seconds. In blinded evaluation (1120 ratings), model segmentations received higher scores than reference annotations (+0.32 BraTS; +1.38 external validation). Conclusion: A fully automated deep-learning model achieved high meningioma segmentation accuracy across multi-institutional training data and external clinical imaging. In a blinded study, model segmentation quality exceeded reference annotations, and 1.2-second inference supported workflow integration. Prospective evaluation is warranted before routine deployment.

Glioblastoma (GBM) is the most common and lethal primary malignant brain tumor in adults, with median survival remaining approximately 12-15 months despite aggressive multimodal therapy. Therapeutic resistance and tumor recurrence are driven in part by limited drug penetration across the blood-brain barrier (BBB) and the persistence of brain cancer stem cells (BCSCs), highlighting the need for brain-penetrant therapeutic platforms capable of achieving sustained intratumoral delivery. Here, we developed a dendrimer-based nanotherapeutic by conjugating metformin to a fourth-generation hydroxyl-terminated polyamidoamine dendrimer (P4-MET) to enhance intracranial bioavailability and therapeutic efficacy in GBM. P4-MET exhibited favorable pharmacokinetic properties, including prolonged retention within the tumor microenvironment, and demonstrated enhanced cytotoxicity against GBM cell lines relative to free metformin (f-MET). Mechanistical studies with transcriptomic profiling by RNA sequencing revealed distinct treatment-associated molecular signatures, identifying BOLA2B as the most significantly differentially expressed gene between treatment groups. Specifically, BOLA2B expression was markedly elevated in f-MET-treated cells but not so following P4-MET treatment. Given the established association of BOLA2B with mTORC1 signaling and GPX4-mediated ferroptosis resistance, these findings suggest that P4-MET may, at least in part, enhance therapeutic efficacy by modulating ferroptosis-associated pathways. In orthotopic GBM models, combination treatment with P4-MET and radiotherapy (RT) significantly prolonged overall survival and increased tumor cell death compared with either monotherapy alone, consistent with a synergistic radiosensitizing effect. Importantly, P4-MET demonstrated minimal systemic toxicity, supporting its favorable therapeutic index and translational potential. Collectively, these findings establish P4-MET as a brain-penetrant nanomedicine platform that improves metformin delivery, modulates ferroptosis-related signaling networks, and potentiates radiotherapeutic response in GBM. This study highlights the potential of dendrimer-enabled metabolic nanotherapies to overcome therapeutic resistance in malignant brain tumors.