Citations

Abstract High-grade gliomas represent the most common type of primary adult malignant brain tumor. IDH1/2 mutations are linked to lower-grade gliomas and better patient outcomes; however, molecular profiling has revealed additional alterations that drive aggression. CDKN2A/B loss in IDH-mutant astrocytoma is recognized as a key marker of grade 4 tumor biology, yet there remain no effective targeted therapies in aggressive gliomas. Here, we analyzed a cohort of patient-derived IDH-mutant astrocytoma with whole-exome and RNA sequencing data and identified several candidate genes and pathways concurrently regulated with CDKN2A/B loss, revealing an enhanced signature related to vascular processes. We sought to elucidate the angiogenic mechanisms and functional outcomes associated with high-grade behavior following CDKN2A/B loss in IDH-mutant astrocytoma to inform future therapeutic strategies. We used grade 4 IDH-mutant astrocytoma patient-derived xenograft (PDX) and established cell lines harboring homozygous CDKN2A/B deletion. We re-expressed the cell cycle regulators p14, p15, and p16 using a Tet-inducible lentiviral system and confirmed reduced proliferation compared to parental lines. Re-expression of p14, p15, or p16 also resulted in decreased glioma cell migration and invasion. Intriguingly, re-expressing these regulators reduced VEGF secretion. HUVEC cells cultured with conditioned media (CM) from the re-expression glioma lines decreased canonical activation of PI3K/Akt and Stat3 signaling and a diminished capacity to promote endothelial migration, invasion, and tube formation. Furthermore, in vivo Matrigel plug assays using CM from the re-expression lines showed a decreased ability to recruit endothelial cells, pericytes, and form vascular organized structures. We identified the WT1 transcription factor as an upstream regulator of angiogenesis. WT1 expression was inversely correlated with CDKN2A/B expression in patient data, and knockdown of WT1 in astrocytoma cells reduced VEGF secretion and impaired ability to promote endothelial migration. Taken together, our findings reveal a novel role for WT1 in VEGF-driven angiogenesis in IDH-mutant astrocytoma with CDKN2A/B homozygous deletion.

Abstract Immune checkpoint inhibitors (ICIs) have limited benefit in recurrent high-grade astrocytoma (rHGA), largely because the blood–brain barrier and a profoundly immunosuppressive tumor microenvironment prevent T cells from infiltrating. Laser interstitial thermal therapy (LITT) is a minimally invasive, cytoreductive procedure that can “heat up” these otherwise “cold” tumors and sensitize them to ICIs. In this tri-institutional Phase 1/randomized Phase 2 trial (NCT02311582), bevacizumab- and immunotherapy-naïve rHGA patients were initially randomized 1:1 to either LITT followed by pembrolizumab (LITT+PEM) or non-LITT surgery (biopsy or resection) followed by pembrolizumab (NLS+PEM). Phase 2 participants enrolled at a second recurrence—with several already at a third recurrence—underscoring the advanced disease stage of this cohort. After 21 patients, randomization was halted when contemporaneous evidence showed limited benefit from adjuvant ICIs alone, and the remaining 24 patients received only LITT+PEM. In the 21-patient intent-to-treat cohort, LITT+PEM extended median OS to 21.3 months with 54% alive at 18 months (OS18) versus 6.7 months with 12.5% OS18 with NLS+PEM (HR 0.29; 95% CI, 0.01–0.88; p=0.021). Median PFS was 7.8 versus 2.2 months (HR 0.3; 95% CI, 0.10–0.87; p=0.020). Among 39 per-protocol patients, LITT+PEM yielded a median OS of 11.8 months with 42% OS18 versus 5.2 months with 0% OS18 for NLS+PEM (HR 0.17; 95% CI, 0.06–0.49; p=0.0002), and a median PFS of 4.5 versus 1.6 months (HR 0.21; 95% CI, 0.08–0.56; p=0.0006). The combination was well tolerated. Immune profiling revealed that LITT triggers early activation of non-classical monocytes—a change associated with improved survival—while subsequent pembrolizumab unleashes robust CD8⁺ T cell proliferation and clonal expansion. Long-term LITT+PEM survivors developed coordinated memory T-cell responses, whereas shorter-surviving patients exhibited stagnant memory pools and exhausted phenotypes. Together, these results demonstrate that LITT plus pembrolizumab is safe, overcomes rHGA’s immunosuppressive barrier, and mobilizes robust anti-tumor immunity.

Abstract Glioblastomas (GBMs) are aggressive brain tumors that pose therapeutic challenges. Microperfusion (MP) probes offer a unique method for real-time sampling of extracellular biomarkers and drug responses within the tumor microenvironment. Compared to microdialysis probes, MP probes can sample large molecules without a molecular weight cut-off, making them particularly valuable for drug quantification and novel biomarker detection. In this study, MP was used to measure the GDF-15 (24.8 kDa) levels in TP53 wild-type, MDM2-amplified GBM treated with Brigimadlin, using orthotopic mouse models. Patient-derived xenograft (GBM108) was implanted intracranially in mice, and tumor growth was monitored by bioluminescent imaging or MRI. A single MP probe was placed in the tumor for the Brigimadlin group and compared with the vehicle group. MP samples were collected over four-hour daily sessions across a baseline day and three treatment days. Brigimadlin treatment led to an increase in GDF-15 within the tumor catheter during treatment days (mean: 225.3 pg), compared to stable levels in the vehicle control group (mean: 66.4 pg), consistent with activation of the p53 pathway. In a separate study of blood–brain barrier (BBB) permeability, FITC-Dextran analysis revealed a decline in BBB permeability from 0.4 μg/mL at 24 hours post-implantation to a stable 0.02 μg/mL by 72 hours, reflecting sustained but reduced permeability. MP enabled quantification of GDF-15 dynamics in vivo, highlighting its potential in clinical settings. An investigational device exemption has been secured for an upcoming clinical trial deploying intraoperative use of cerebral microperfusion catheters.

Abstract BACKGROUND Post-operative prognostication in glioma patients remains a clinical challenge, particularly given the heterogeneity in tumor biology and patient outcomes. We evaluated whether image-derived features from post-operative imaging improve survival modeling beyond established clinicopathologic factors. METHODS We analyzed a cohort of 71 post-surgical glioma patients treated at Princess Margaret Cancer Centre with known clinicopathologic features including age, histological classification, IDH mutation status, MGMT methylation status, extent of resection, and performance status. A baseline Cox proportional hazards model was fit to clinical variables. Radiomic features were extracted using PyRadiomics from post-operative CT and MRI across three regions of interest: whole brain, tumor bed, and peritumoral ring. Features underwent stepwise unsupervised reduction (variance filtering, exclusion of volume-correlated features, and removal of remaining collinear features), followed by dimensionality reduction via principal component analysis. Combined clinical and imaging models were evaluated in the overall cohort and stratified by IDH mutation status. RESULTS In the overall cohort, the clinical model was highly prognostic (C-index 0.74, p ~ 3.2×10⁻⁶). Adding imaging features improved performance (C-index 0.79) but was not significant (p ~ 0.31). Subset analysis revealed differential effects by IDH status. In IDH-mutant gliomas (n=24), neither clinical nor combined models were significant. In IDH wild-type glioblastoma (n=47), the clinical model achieved C-index 0.75 (p=0.04). The addition of imaging features significantly improved model performance (C-index 0.83, p=0.03), with selected imaging components contributing independent prognostic value after adjustment for clinical variables. Post-hoc analysis of radiomic feature importance (random forest ranking) revealed that top contributing features were drawn from both CT and MRI modalities, with most sourced from the whole brain region. CONCLUSIONS In post-surgical patients with IDH wild-type glioblastoma, image-derived features from post-operative imaging can significantly enhance prognostic modeling beyond known clinicopathologic factors. These preliminary findings support the potential role of radiomic biomarkers in refining risk stratification for this patient subgroup.

Abstract Glioblastoma (GBM) is the most common primary tumor in adults with a median survival of 15 months post-treatment. GBM incidence and progression depends on sex, with reports of 1.6x increased incidence and 6-month shorter overall survival in males, compared to females. Regardless of sex, the standard of care for GBM patients includes surgical resection, followed by chemotherapy and radiotherapy, and often dosing of the synthetic glucocorticoid Dexamethasone (DEX) to reduce brain edema post-treatment. Our lab recently found that DEX can suppress or promote GBM growth depending on the time of day the treatment is administered. Because glucocorticoid secretion depends on circadian time and sex, we tested whether endogenous glucocorticoids regulate sex differences in GBM growth. We transduced a murine chromosomal male or female GBM cell line (Nf1-/-DNp53 XX or XY) with a transcriptional luciferase reporter of the circadian clock gene Per2 (Nf1-/-DNp53-P2L). These cells were next treated with DEX at the daily peak or trough of Per2 expression and growth was measured 48 hours post-treatment. We found that administering DEX at peak Per2 suppresses growth in males, while administering DEX at trough Per2 promotes growth in both males and females. We then knocked-down the glucocorticoid receptor (GR) using an shRNA lentiviral construct in two GBM cell models (GL261 and LN229) and implanted WT or GR-KD cells into the basal ganglia of male and female mice. Loss of GR in GBM cells significantly suppressed GBM growth, especially in male mice, as evidenced by postmortem Ki67 staining. These results suggest that GBM growth in males may be more sensitive to endogenous glucocorticoids, and that sensitivity varies with time of day. This work will inform future personalized circadian interventions to improve GBM patient outcomes. Supported by NIH grant R01NS134885.

Abstract CIC-rearranged sarcoma (CRS) is a rare disease driven by a specific fusion protein involving the CIC gene. The occurrence in the brain is 3% in all CRS patients, and these tumors frequently metastasize to the brain. 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 show that CIC-DUX4/NUTM1 fusions activate JAK and its downstream effector STAT1/3. We hypothesize that JAK/STAT1/3 signaling cooperates with CIC-fusions to drive CIC-sarcomas by inducing ETV1/4/5 expression. Patient-derived CRS cell lines showed elevated levels of JAK1/STAT1/3 activation compared to fusion-negative sarcoma lines. Inhibition of JAK1 using Ruxolitinib and Solicitinib reduced STAT1/3 phosphorylation, downregulated ETV1/4/5 expression at both mRNA and protein levels, and diminished ETV5 promoter activity, cell proliferation, and tumorigenicity. Although the mechanism by which CIC-fusions activate oncogenic targets is still under investigation, histone acetylation appears to play a central role. STAT1/3 interacts with p300/CBP to enhance transcription, and STAT1 is necessary for p300 acetyltransferase activity. Ruxolitinib significantly reduced histone acetylation at ETV1/4/5 promoters in hMSC cells expressing CIC-DUX4/NUTM1, as well as in CRS cell lines. Unlike the p300 inhibitor C646, which causes global hypoacetylation, Ruxolitinib’s effects were promoter-specific, indicating its potential as a more targeted and less toxic therapeutic option. Importantly, we found that STAT1/3 binds to ETV1/4/5 promoters only in the presence of CIC-fusions. Luciferase assays confirmed that STAT1/3 alone cannot activate ETV5 transcription without CIC-fusions, revealing a novel cooperative mechanism. In vivo, Ruxolitinib treatment of CRS xenografts led to significant reductions in tumor volume, STAT1/3 activation, and ETV1/4/5 expression. These findings support JAK1/STAT1/3 inhibition as a promising therapeutic strategy for CRS and warrant further preclinical investigation.

Abstract Glioblastoma (GBM), the most aggressive primary brain tumor in adults, is marked by profound immune suppression. Tumor-derived extracellular vesicles (TEVs) are increasingly recognized as key mediators of this immunosuppressive environment. In this study, we examined the tumor-immune microenvironment using ultrasonic aspirate samples from GBM patients (n = 14). Several immune checkpoint molecules, including PDL1, B7-H3, and VISTA, were notably elevated. TIGIT, a receptor typically associated with T cells, was widely expressed across multiple myeloid subsets, including monocytic myeloid-derived suppressor cells (mMDSCs; 64.27 ± 7.99%) and non-classical monocytes (NCM; 39.8 ± 4.37%). Co-culture of healthy donor monocytes (n=10) with TEVs replicated similar effects (control 11.69±1.87 vs EV treated 23.32±2.0). We found CD155, the primary TIGIT ligand, to be heavily enriched in TEVs and co-expressed with TIGIT in co-culture, suggesting the TIGIT/CD155 axis may be involved in promoting immune suppression. Additionally, induced MDSCs significantly inhibit T cell proliferation (30.65±5.97% proliferation, v/s control 86.47±2.94, p=0.0001), concomitant with a surge in Th2 immune responses via TIGIT+ monocytes along with an increase in NLRP3 and IL-1β expressing cells. Interestingly, TIGIT knockdown did not affect NLRP3 expression but did restore T cell proliferation (64.13 ± 1.33%; p = 0.02) and pro-inflammatory cytokine production. However, the restoration of T cell proliferation was lost when NLRP3 was also silenced, indicating its essential role in mediating immune rescue. Overall, our findings highlight a crucial role of TIGIT in driving myeloid-mediated immune suppression in GBM. Furthermore, TIGIT inhibition may unmask NLRP3 function, potentially contributing to immune rescue.

Abstract Glioblastoma is a highly lethal malignancy with dismal overall survival and near universal recurrence despite maximal multimodal therapy. Patients with unmethylated O6-methylguanine methyltransferase (MGMT) promoters do not derive survival benefit from adjuvant temozolomide. Immunotherapies have revolutionized cancer care; however, this modality has yet to translate into survival benefits in glioblastoma in part due to both local and systemic immunosuppressive states. Here, we report the results of a phase 1 clinical trial (NCT04015700) evaluating the safety and feasibility of GNOS-PV01, a personalized DNA vaccination platform that safely immunized against up to 40 patient-specific neoantigens in a clinically relevant timescale following surgical resection and radiation for MGMT-unmethylated glioblastoma patients. Multisector tumor sampling at time of resection enabled personalized and spatially representative neoantigen identification through an established pipeline. In the nine participants receiving vaccines, there were no unexpected toxicities or serious adverse events with a median vaccine delivery time of 10 weeks post-radiation. The vaccination was strongly immunogenic and induced activation and expansion of both local infiltrating CD8+ and CD4+ T-cells and circulating peripheral T-cells. T-cell receptor sequencing revealed both expanded pre-existing populations as well as novel neoantigen-specific populations, suggesting that vaccination both reinvigorates pre-existing immunity and generates novel immune reactivity. We developed a new technology to profile T-cells at single-nuclei resolution from frozen tissue revealing that vaccination altered gene expression signatures involved in inflammatory response and lymphocyte activation in the tumor microenvironment. Exposure to dexamethasone greatly suppressed immune reactivity, while PD-1 blockade enhanced local immune responses. With respect to efficacy, one third of patients survived longer than 24 months with one long-term survivor living >40 months from time of diagnosis, exceeding survival of recently published trials. Thus, our study demonstrates the safety, feasibility, and preliminary clinical efficacy of a personalized multivalent neoantigen vaccination platform in a devastating cancer.

Abstract INTRODUCTION While TERT promoter mutation (TPM) has been established as a marker of clinically aggressive meningiomas, this alteration is rare and found in less than 5% of all cases. However, a larger subset of meningiomas may exhibit aberrant TERT expression in the absence of TPMs. This study investigated the effect of TERT gene expression on clinical outcome in meningioma patients. METHODS Clinical and molecular data were retrospectively collected on 1241 meningiomas, split into a Toronto discovery cohort and a multi-institutional validation cohort. Sanger sequencing and bulk RNA sequencing were used to determine TPM status and TERT gene expression. The effect of TERT expression on progression-free survival (PFS) was assessed using Kaplan-Meier and Cox regression analysis. RESULTS While meningiomas with TPM showed expectedly higher TERT gene expression compared to wildtype (TP-WT) cases (p<0.0001), TERT expression was still detected in 28.7% (157/547) of TP-WT meningiomas. Meningiomas with TERT expression showed significantly worse PFS compared to meningiomas without any TERT expression. In fact, WHO grade 1 meningiomas with TERT expression had PFS outcomes resembling WHO grade 2 meningiomas lacking TERT expression (p=0.59). In turn, WHO grade 2 meningiomas with TERT expression had clinical outcomes similar to WHO grade 3 meningiomas without TERT expression (p=0.42). Furthermore, the proportion of meningiomas expressing TERT as well as overall TERT expression levels increased with increasing WHO grade. Multivariable analysis showed that TERT expression was significantly associated with worse PFS even when controlling for other known predictors of clinical outcome including TPM, CDKN2A/B loss, 1p/22q status and WHO grade (HR 1.85 [95% CI 1.33-2.57], p=0.00024). CONCLUSION TERT expression is a novel independent biomarker of outcome for meningiomas identifiable in up to one-third of cases that may be utilized to reclassify tumours to a higher WHO grade.

Abstract BACKGROUND Posterior fossa group A ependymomas (PFAs) and diffuse midline gliomas (DMGs) are lethal pediatric brain tumors characterized by global loss of H3K27me3. This epigenetic disruption is caused by either EZHIP overexpression or H3.1/H3.3K27M mutations, which are mutually exclusive. EZHIP is aberrantly expressed in nearly all PFAs and approximately 10% of DMGs, while K27M mutations are found in ~80% of DMGs. In normal development, EZHIP expression is restricted to primordial germ cells during meiosis. We used human neural stem cells (NSCs), which give rise to ependymal and oligodendrocyte precursor lineages, to model EZHIP’s developmental effects. These cell types reflect the likely cells of origin for PFAs and DMGs, making them a biologically relevant platform to interrogate early tumorigenic mechanisms. METHODS AND RESULTS EZHIP was expressed in NSCs, astrocytes, and DMG lines. In NSCs, EZHIP induced strong repression of genome stability and mitotic fidelity genes, confirmed by gene set enrichment analysis (NES –2.91, p = 1e–10), and activated stem-like developmental programs. This repression was not observed in differentiated cells or tumor lines, indicating an NSC-specific vulnerability. The repressed targets were highly enriched for E2F-regulated genes (NES –3.61, p = 1e–10). EZHIP-expressing NSCs showed reduced DNA repair capacity, mitotic abnormalities, and continued proliferation. EZHIP is known to impair double-strand break repair by binding PALB2 and blocking BRCA2 recruitment, and to disrupt TopoIIα localization via H3K27me3 depletion, compounding mitotic stress in NSCs. CONCLUSIONS EZHIP disrupts genome maintenance and promotes transformation selectively in neural progenitors during a defined developmental window. Published data show that H3.3K27M induces profound transcriptional reprogramming in week 13 human NSCs, but these effects are diminished or absent by week 19, suggesting a shared, time-limited window of epigenetic vulnerability in both H3K27M- and EZHIP-driven tumors. Understanding this context-dependent repression has important implications for identifying stage-specific therapeutic vulnerabilities in pediatric gliomas.