Citations

Abstract Imaging-based monitoring of gliomas is hampered by treatment-related changes, as well as the insidious growth of gliomas harboring the isocitrate dehydrogenase (IDH) mutation. The IDH mutation results in elevated D-2-hydroxyglutarate (D-2-HG), which is detectable in cerebrospinal fluid (CSF) that can be accessed longitudinally from multiple compartments, including cranially via CSF access devices. As such, we evaluated the early utility of CSF D-2-HG as a serially accessible biomarker for IDH-mutant gliomas. A CLIA-approved gas chromatography mass spectrometry assay was developed for CSF D- and L-2-HG. Lumbar and cranial CSF samples were collected from patients with IDH-mutant gliomas or IDH-wild-type brain tumors and non-tumor pathologies via surgical field collection, lumbar punctures, Ommaya reservoirs, and ventriculoperitoneal shunts. First, to confirm the ability of CSF D-2-HG to detect IDH-mutant gliomas, concentrations were compared between IDH-mutant gliomas and wild-type lesions. Cranial, but not lumbar, CSF D-2-HG distinguished primary IDH-mutant gliomas from IDH-wild type lesions (cranial AUC= 0.89, 95% confidence interval (CI)= 0.80-0.97); lumbar AUC= 0.52, 95% CI=0.28-0.76). Indeed, CSF D-2-HG was significantly higher in cranial than lumbar samples from IDH-mutant glioma patients (median lumbar=0.20 μM, cranial = 1.72 μM; p<0.0001), confirming a significantly elevated abundance of CSF D-2-HG only in cranial CSF from IDH-mutant gliomas. Then, response to cytoreduction was evaluated, demonstrating that cranial CSF D-2-HG levels decreased to 0.54x of baseline with resection in seventeen patients (p=0.0129). Changes in tumor-to-CSF contact impacted the serial evaluation of CSF D-2-HG prior to versus after chemoradiation in some patients. Nevertheless, in patients with grade 4 IDH-mutant astrocytomas, serial cranial CSF D-2-HG increased with disease progression and differentiated stability from pseudoprogression when tumor-CSF contact was sufficient. In conclusion, serial cranial CSF D-2-HG shows promise as a monitoring biomarker in patients with IDH-mutant gliomas, although anatomic variables must be considered in parallel to CSF D-2-HG evaluation.

Abstract INTRODUCTION Recurrent IDH-mutant gliomas pose a significant therapeutic challenge, with limited treatment options following progression after standard therapy. Combining PARP inhibitors with immune checkpoint blockade has been proposed as a synergistic strategy in IDH-mutant high-grade gliomas, leveraging vulnerabilities in homologous recombination repair and increased PD-L1 expression following PARP inhibition. OBJECTIVE This phase II trial (NCT03991832) evaluated the combination of the PARP inhibitor olaparib and the PD-L1 inhibitor durvalumab in patients with recurrent IDH-mutant glioma. We also investigated the potential of the plasma tumor methylome as a non-invasive biomarker of treatment response. METHODS Twenty-nine patients (median age 40.5 years; 41% female) were enrolled between January 2020 and February 2023. All patients received olaparib (300 mg twice daily) and durvalumab (1,500 mg IV every four weeks) until radiographic or clinical progression. Plasma samples were collected at baseline and monthly, and cell-free methylated DNA immunoprecipitation sequencing (cfMeDIP-seq) was performed. RESULTS The objective response rate was 10%, and median overall survival was 9.3 months. Longitudinal cfMeDIP-seq profiling enabled development of a circulating methylome classifier that accurately distinguished responders from non-responders. Integration with matched tumor transcriptomic and methylation data revealed enrichment of immune and DNA repair pathways in responders. Whole-exome sequencing identified no consistent mutational correlates. Spatial transcriptomic analysis demonstrated a more interactive, immune-rich tumor microenvironment and reduced malignant cell state diversity in responders. CONCLUSION This study supports the safety of combined PARP and PD-L1 blockade in recurrent IDH-mutant glioma and highlights the plasma methylome as a promising non-invasive biomarker of therapeutic response.

Abstract Meningiomas are the most common primary intracranial tumors and exhibit clinical heterogeneity. Radiotherapy (RT) remains the only adjuvant therapy, but response is variable and biomarkers are limited. RTOG-0539 is the first prospective phase 2 trial to stratify meningioma patients for adjuvant RT based on clinical risk. Here, we apply modern molecular tools to this cohort and uncover correlates of RT response. To do so, tumor tissue from 100 RTOG-0539 patients was profiled using DNA methylation arrays, RNA sequencing, and whole-exome sequencing. Recurrence scores, Molecular Groups, gene expression, and copy number alterations were compared across clinical groups and between RT responders and non-responders. Using this approach, modern grading criteria, including brain invasion, TERT mutation, CDKN2A/B deletion and 1p/1q status, would reclassify 10% of tumors and alter treatment group assignment in 7%. Notably, non-responders to RT had more frequent 1p and 14q loss, and greater copy number burden. In addition, transcriptomic and epigenetic profiling revealed immune-related signatures in RT responders and upregulation of cell cycle–related pathways in RT non-responders, several of which overlapped with targets of vorinostat, a histone deacetylase inhibitor validated in aggressive meningioma models. Of particular importance, the Proliferative Molecular Group was an independent predictor of post-RT recurrence in multivariable analysis, outperforming WHO grade. In conclusion, multi-omic analysis of the RTOG-0539 cohort shows that updated WHO grading criteria, incorporating molecular and cytogenetic features, improve risk stratification. However, molecular classification, particularly the Proliferative group, remains an independent and stronger predictor of RT response. These findings support integrating molecular biomarkers alongside modern grading frameworks to guide treatment and trial design in meningioma.

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.