Pediatric Gliomas Research Articles

Pediatric high-grade gliomas with concomitant RB1 and SETD2 alterations and Li-Fraumeni syndrome

Pediatric high-grade gliomas with concomitant RB1 and SETD2 alterations and Li-Fraumeni syndrome

FDA Approval Summary: Tovorafenib for Relapsed or Refractory BRAF-altered Pediatric Low-Grade Glioma.

On April 23, 2024, FDA granted accelerated approval to tovorafenib, a type II RAF kinase inhibitor, for the treatment of patients 6 months of age and older with relapsed or refractory pediatric low-grade glioma (pLGG) harboring a BRAF fusion or rearrangement, or BRAF V600 mutation. Efficacy was evaluated in FIREFLY-1 (NCT04775485), a single-arm, open-label, multicenter trial that enrolled patients 6 months to 25 years of age with relapsed or refractory pLGG with an activating BRAF alteration who had received prior systemic therapy. The major efficacy outcome measure was radiologic overall response rate (ORR), defined as the proportion of patients with complete response, partial response, or minor response as determined by blinded independent central review using Response Assessment in Pediatric Neuro-Oncology (RAPNO) criteria. A key secondary endpoint was duration of response (DoR). In an efficacy population of 76 patients, the ORR was 51% (95% confidence interval (CI): 40, 63), and the median DoR was 13.8 months (95% CI: 11.3, not estimable). The required post-marketing clinical trial (FIREFLY-2) was well underway at the time of accelerated approval. This represents the first FDA approval of a systemic therapy for the treatment of patients with pLGG with BRAF fusions or rearrangements.

Multimodal deep learning improves recurrence risk prediction in pediatric low-grade gliomas.

Postoperative recurrence risk for pediatric low-grade gliomas (pLGGs) is challenging to predict by conventional clinical, radiographic, and genomic factors. We investigated if deep learning (DL) of magnetic resonance imaging (MRI) tumor features could improve postoperative pLGG risk stratification. We used a pretrained DL tool designed for pLGG segmentation to extract pLGG imaging features from preoperative T2-weighted MRI from patients who underwent surgery (DL-MRI features). Patients were pooled from 2 institutions: Dana Farber/Boston Children's Hospital (DF/BCH) and the Children's Brain Tumor Network (CBTN). We trained 3 DL logistic hazard models to predict postoperative event-free survival (EFS) probabilities with (1) clinical features, (2) DL-MRI features, and (3) multimodal (clinical and DL-MRI features). We evaluated the models with a time-dependent Concordance Index (Ctd) and risk group stratification with Kaplan-Meier plots and log-rank tests. We developed an automated pipeline integrating pLGG segmentation and EFS prediction with the best model. Of the 396 patients analyzed (median follow-up: 85 months, range: 1.5-329 months), 214 (54%) underwent gross total resection and 110 (28%) recurred. The multimodal model improved EFS prediction compared to the DL-MRI and clinical models (Ctd: 0.85 (95% CI: 0.81-0.93), 0.79 (95% CI: 0.70-0.88), and 0.72 (95% CI: 0.57-0.77), respectively). The multimodal model improved risk-group stratification (3-year EFS for predicted high-risk: 31% versus low-risk: 92%, P < .0001). DL extracts imaging features that can inform postoperative recurrence prediction for pLGG. Multimodal DL improves postoperative risk stratification for pLGG and may guide postoperative decision-making. Larger, multicenter training data may be needed to improve model generalizability.

Establishing a living biobank of pediatric high-grade glioma and ependymoma suitable for cancer pharmacology.

Brain tumors are the deadliest solid tumors in children and adolescents. Most of these tumors are glial in origin and exhibit strong heterogeneity, hampering the development of effective therapeutic strategies. In the past decades, patient-derived tumor organoids (PDT-O) have emerged as powerful tools for modeling tumoral cell diversity and dynamics, and they could then help defining new therapeutic options for pediatric brain tumors. Through an integrative approach based on our expertise and a careful review of the literature about glioblastoma 3D primary cultures, we set-up a standardized methodological pipeline for the establishment, characterization and biobanking of PDT-O through direct 3D in vitro culture of the deadliest pediatric glial brain tumors. To assess PDT-O fidelity and validate their pre-clinical relevance, we performed comprehensive histological, molecular and drug-response analyses. Our methodological pipeline allowed the rapid and efficient generation of PDT-O recapitulating their parental tumor features, including intra-tumoral heterogeneity, even after several passages and cryopreservation/revival as 3D cultures. Moreover, we successfully performed pre-clinical test responses on these PDT-O to standard-of-care therapies and new therapeutic options. Finally, we identified ONC201 as a selective drug for pediatric glial tumor types not restricted to H3K27M-mutant glioma, as well as combination strategies to increase the therapeutic response to ONC201. Hence, we describe a fast and robust process to biobank PDT-O for pediatric glial brain tumors. These PDT-O models have the potential for patient-specific modeling even after long-term expansion in vitro and we established the proof-of-concept of their usefulness to support powerful pre-clinical studies.

IDH-mutant gliomas in children and adolescents - from biology to clinical trials

Gliomas account for nearly 30% of all primary central nervous system (CNS) tumors in children and adolescents and young adults (AYA), contributing to significant morbidity and mortality. The updated molecular classification of gliomas defines molecularly diverse subtypes with a spectrum of tumors associated with age-distinct incidence. In adults, gliomas are characterized by the presence or absence of mutations in isocitrate dehydrogenase (IDH), with mutated IDH (mIDH) gliomas providing favorable outcomes and avenues for targeted therapy with the emergence of mIDH inhibitors. Despite their rarity, IDH mutations have been reported in 5-15% of pediatric glioma cases. Those with primary mismatch-repair deficient mIDH astrocytomas (PMMRDIA) have a particularly poor prognosis. Here, we describe the biology of mIDH gliomas and review the literature regarding the emergence of mIDH inhibitors, including clinical trials in adults. Given the paucity of clinical trial data from pediatric patients with mIDH glioma, we propose guidelines for the inclusion of pediatric and AYA patients with gliomas onto prospective trials and expanded access programs as well as the potential of combined mIDH inhibition and immunotherapy in the treatment of patients with PMMRDIA at high risk of progression.

Differentiation therapy targeting the stalled epigenetic developmental programs in pediatric high-grade gliomas

Differentiation therapy targeting the stalled epigenetic developmental programs in pediatric high-grade gliomas

Frequency and Impact of Constitutional Mismatch Repair Deficiency in Patients With High-Grade Glioma, a Retrospective Analysis of 7 Years in Pakistan: an IRRDC Study

PURPOSE Constitutional mismatch repair deficiency (CMMRD) is a genetic cancer predisposition syndrome among children and young adults. This study aimed to evaluate the frequency of CMMRD among patients with pediatric high-grade glioma (pHGG) in a single tertiary care center in Pakistan, a country with high consanguinity rates. PATIENTS AND METHODS We reviewed the data of patients age &lt;18 years with pHGG, anaplastic astrocytoma, and diffuse midline glioma (DMG) with CMMRD testing between 2016 and 2023. CMMRD testing was done using the Aronson et al criteria. A few patients were sent to Sick Kids, Toronto, to review the mismatch repair protein stains via multigene panels. RESULTS Forty-seven patients were identified, with a median age of 11 years (IQR, 8-16). Headache (89.4%) was the most common symptom. Thirty-seven patients had hemispheric tumors; 12.8% and 8.5% had posterior fossa and midline tumors, respectively. Histopathology revealed 70.2% glioblastoma, 23.4% anaplastic astrocytoma, and 6.4% DMG. CMMRD was positive in 15 of 47 patients (31.9%). Eight patients had loss of PMS2 . Three had loss of PMS2 and MLH1 ; two had loss of MSH6 , one had loss of MSH6 and MSH2 , and only one patient had loss of MSH2 . Consanguinity and family history of malignancy correlated with CMMRD ( P = .009, P = .031, respectively). Two-year overall survival of all patients was 23.4% (median follow-up, 0.59 years [95% CI, 0.000 to 1.171]). Two-year overall survival of mismatch repair deficiency–positive patients was 20% (median follow-up, 0.910 years [95 CI, 0.380 to 1.440]). CONCLUSION We found a high frequency of CMMRD among patients with pHGG, particularly with positive consanguinity. Our study highlights the significance of genetic testing and surveillance. It is essential to develop low and middle income country-tailored protocols due to limited access and financial constraints associated with using immune checkpoint inhibitors.

Pediatric diffuse intrinsic pontine gliomas- a prospective observational study from a tertiary care neurosurgical center.

Diffuse intrinsic pontine glioma (DIPG) in children comprises 80% of brainstem gliomas. In 2021, 5th edition of WHO CNS tumor classification defined H3K27M altered diffuse midline gliomas (DMGs) which replaced this entity. Lesion location precludes resection and the only current option available is radiotherapy. Patient age, duration of symptoms, histone subtype mutation etc. may helpl in prognostication but the disease remains incurable with a median overall survival of 9-12months. This is a prospective observational study from a tertiary health care center in a low to middle-income country. We included patients with DIPG (radiological and/or histopathological H3K27M altered) from June 2018 to April 2023. Clinical, radiological, histology, and molecular features were reviewed and prognostic factors for 3months, 6months, and overall survival was analysed for all patients. We included 92 pediatric patients. The median age of our study population was 8.5years. Median LPS was 80. Cranial nerve palsy was the most common presenting complaint. Hydrocephalus requiring CSF diversion was present in 38 patients (41.3%). Lesion biopsy was performed in 36 patients (39.1%) and exophytic component decompression was done in 11 patients (11.9%). Seven patients were lost to follow-up. Adjuvant therapy was received by 51 patients (51/85, 60%). Radiotherapy was the only significant prognostic indicator of 3months, 6months, and overall survival (HR: 0.39). The presence of necrosis on histopathology was also an indicator of poor prognosis (HR: 2.38). There were 7 long-term survivors in our study but we did not find any significant survival prognostic indicator amongst this group. Conventional adjuvant therapy has not proven of much benefit. With the advancement in molecular understanding of the entity, there is an upsurge in the development of targeted therapy but with no promising results so far. In this study, we have attempted to explore the prognostic factors and unique challenges we face in a resource-limited setting against this disease.

The role of brainstem biopsy and targeted therapies in pediatric diffuse midline glioma/diffuse intrinsic pontine glioma

Pediatric diffuse midline glioma (DMG), including diffuse intrinsic pontine glioma (DIPG), are aggressive brainstem tumors with a dire prognosis, traditionally diagnosed based on MRI characteristics. The recognition that molecular characteristics may determine prognosis and response to therapy has led to a reevaluation of biopsy necessity. This comprehensive review addresses the evolving role of brainstem biopsies in diagnosing and managing these tumors – both within the context of a clinical trial and in routine clinical care. We examine practice variability around brainstem biopsies for DMG/DIPG, revealing a global inconsistency in biopsy application and perceptions amongst providers. We show that safety profiles from contemporary studies demonstrate a high diagnostic success rate with minimal permanent morbidity, supporting the feasibility of biopsies in expert centers. Beyond the safety angle, we discuss the utility of biopsies in enabling personalized medicine, highlighting how molecular profiling has been used in multiple centers to guide targeted therapies. We present initial evidence from case studies and registry reports to address whether these molecularly targeted approaches are 1) clinically feasible, and 2) likely to extend survival. Furthermore, we present evidence to support the notion that biopsies facilitate the design of more refined clinical trials, shifting from a one-size-fits-all model to molecularly stratified studies. We discuss how this new paradigm for trial design is likely necessary in the context of DMG/DIPG given the lack of progress in this disease for the last several decades. Future directions discussed in the review include liquid biopsy techniques to complement or replace tissue sampling, aiming to enhance diagnostic precision and treatment monitoring.

Radiographic and visual response to the type II RAF inhibitor tovorafenib in children with relapsed/refractory optic pathway glioma in the FIREFLY-1 trial.

Due to their anatomical locations, optic pathway gliomas (OPGs) can rarely be cured by resection. Given the importance of preserving visual function, we analyzed radiological and visual acuity (VA) outcomes for the type II RAF inhibitor tovorafenib in the OPG subgroup of the phase 2 FIREFLY-1 trial. FIREFLY-1 investigated the efficacy (arm 1, n=77), safety, and tolerability (arms 1/2) of tovorafenib (420 mg/m2 once weekly; 600 mg maximum) in patients with BRAF-altered relapsed/refractory pediatric low-grade glioma (pLGG). In this post hoc analysis, anti-tumor activity and VA were analyzed in arm 1 patients with OPG. Anti-tumor activity was independently assessed per Response Assessment in Neuro-Oncology high-grade glioma (RANO-HGG), Response Assessment in Pediatric Neuro-Oncology-LGG (RAPNO) and RANO-LGG criteria. The data cutoff was June 5, 2023. Forty-two of 77 patients had OPGs; 35 of 42 had ≥2 VA assessments. The overall response rate in the OPG subgroup according to RANO-HGG, RAPNO and RANO-LGG criteria were 64%, 50%, and 55%, with clinical benefit rates 95%, 88%, and 90%, respectively. VA per patient was preserved for 80% of patients; 31% demonstrated improved VA; VA per eye was preserved in 87%, with 27% improving. The safety profile in the arm 1 OPG subgroup was similar to the overall FIREFLY-1 safety analysis set. Tovorafenib demonstrated anti-tumor activity in relapsed/refractory BRAF-altered OPG across radiological assessment criteria and was generally well tolerated. Importantly, vision remained stable or improved in most patients.

IL13RA2-integrated genetically engineered mouse model allows for CAR T cells targeting pediatric high-grade gliomas.

Pediatric high-grade gliomas (pHGG) and pediatric diffuse midline gliomas (pDMG) are devastating diseases without durable and curative options. Although targeted immunotherapy has shown promise, the field lacks immunocompetent animal models to study these processes in detail. To achieve this, we developed a fully immunocompetent, genetically engineered mouse model (GEMM) for pDMG and pHGG that incorporates the glioma-associated antigen, interleukin 13 receptor alpha 2 (IL13RA2). Utilizing the RCAS-Tva delivery system in Nestin-Tva mice, we induced gliomagenesis by overexpressing PDGFB and deleting p53 (p53 fl/fl ) or both p53 and PTEN (p53 fl/fl PTEN fl/fl ), with or without IL13RA2 in neonatal mice. De novo tumors developed in models with and without IL13RA2, showing no statistical difference in onset (n = 33, 38 days, p = 0.62). The p53 fl/fl PTEN fl/fl tumors displayed more aggressive characteristics (n = 12, 31 days). Tumors exhibited features typical of high-grade glioma, including infiltration, pseudopalisading necrosis, and microvascular proliferation. They also showed a high Ki-67 index, variable IL13RA2 expression, a high frequency of CD11b + macrophages, and a low proportion of CD3 + T cells. The model proved effective for evaluating IL13RA2-targeted immunotherapies, with a significant response to CAR T-cell treatment that extended survival (46 days vs. 28 days control; p < 0.0001) and achieved 25% long-term survival in mice. This model facilitates the preclinical assessment of IL13RA2-directed therapies and holds potential for clinical application.

DNA methylation-based analysis reveals accelerated epigenetic aging in giant cell-enriched adult-type glioblastoma

BackgroundGiant cell (gc)-enriched glioblastoma (gcGB) represents a distinct histological variant of isocitrate dehydrogenase wild-type adult-type glioblastoma with notable enlarged mono- or multinuclear tumor cells. While some studies suggest a survival advantage for gcGB patients, the underlying causes remain elusive. GcGBs are associated with TP53 mutations, and gcs were shown to accumulate DNA double-strand breaks and show deficient mitosis, potentially triggering cellular senescence programs. Epigenetic clocks have emerged as valuable tools for assessing tumor-induced age acceleration (DNAMethAgeAcc), which has lately proved itself as prognostic biomarker in glioblastoma. Our study aimed to comprehensively analyze the methylome and key metabolic proteins of gcGBs, hypothesizing that they undergo cellular aging programs compared to non-gcGBs.ResultsA total of 310 epigenetically classified GBs, including 26 gcGBs, and nine adults with malignant gliomas allocating to pediatric high-grade glioma molecular subclasses (summarized as “pediatric GB”) were included. DNAMethAgeAcc was computed by subtraction of chronological patient ages from DNA methylome-derived age estimations and its increase was associated with better survival within gcGB and non-gcGB. GcGBs were significantly more often allocated to the subgroup with increased DNAMethAgeAcc and demonstrated the highest DNAMethAgeAcc. Hypothetical senescence/aging-induced changes of the tumor microenvironment were addressed by tumor deconvolution, which was able to identify a cluster enriched for tumors with increased DNAMethAgeAcc. Key metabolic protein expression did not differ between gcGB and non-gcGB and tumor with versus without increased DNAMethAgeAcc but for elevated levels of one single mitochondrial marker, anti-mitochondrial protein MT-C02, in gcGBs.ConclusionsWith its sped-up epigenetic aging, gcGB presented as the epigenetic oldest GB variant in our cohort. Whereas the correlation between accelerated tumor-intrinsic epigenetic aging and cellular senescence in gcGB stays elusive, fostering epigenetic aging programs in GB might be of interest for future exploration of alternative treatment options in GB patients.

Emerging paradigm: Molecularly targeted therapy with Dabrafenib and Trametinib in recurring pediatric gliomas with BRAF mutations: A narrative review.

Gliomas are tumors arising in the central nervous system, frequently associated with Class I mutations and BRAF fusions. These mutations are adverse prognostic factors in juvenile gliomas, leading to high rates of recurrence and poor response to current treatments. The blood-brain barrier and the heterogeneity of gliomas complicate the development of a single treatment strategy for all cases. This review aims to evaluate the efficacy and safety of combination therapies, particularly Dabrafenib and Trametinib, in pediatric gliomas with BRAF V600 mutations and discusses their potential in improving clinical outcomes. A review of recent clinical trials was conducted to assess the impact of targeted therapies, especially the combination of Dabrafenib and Trametinib, on glioma treatment outcomes. Additional therapies are also explored. Combination therapy with Dabrafenib, a BRAF kinase inhibitor, and Trametinib, a MEK inhibitor, has shown significant improvement in overall survival and progression-free survival for pediatric patients with BRAF V600-mutant gliomas. Recent clinical data from 2023 demonstrated enhanced tumor control, reduced relapse rates, and improved safety profiles compared to conventional therapies. Dabrafenib and Trametinib offer a promising targeted therapy for juvenile gliomas with BRAF V600 mutations, with better survival outcomes and manageable safety profiles. However, challenges remain in managing side effects such as fever, headache, lethargy, and rash. Further research into resistance mechanisms and long-term effects is necessary to optimize treatment strategies. Other therapies, such as everolimus and Selumetinib, also show potential and warrant further investigation.

Current Trends in the Allocation of NIH Funding of Brain Tumor Research

Abstract Background The National Institute of Health (NIH) provides a sizable annual budget towards brain tumor research. However, funding allocation for specific pathologies remains poorly described. We aimed to characterize the current landscape of NIH funding towards brain tumors as a function of pathology. Methods NIHRePORTER was queried to identify studies focused on glioblastoma, pediatric glioma, oligodendroglioma, brain metastasis, meningioma, pituitary adenoma, and vestibular schwannoma, from 2000-2023. Studies with R, U and P funding mechanisms were included. Data was compiled and assessed according to pathology. Results Across these 7 tumors, 3,320 unique studies with R, U, or P funding mechanisms were identified from 2000-2023. These were conducted across 480 unique institutions. The sum of funds allocated to all studies was $1,607,662,631. Glioblastoma commanded the largest portion of funds, representing 54% of R mechanisms, 55% of R01-funded studies, 48% of U mechanisms, and 49% of P mechanisms, and accounted for 51% ($813,556,423) of total funding. Brain metastasis was the second most-funded tumor, representing 31% of all R mechanisms, 31% of all R01-funded studies, 26% of all U mechanisms, and 28% of all P mechanisms, and accounted for 29% ($472,715,745) of funding. The remaining 14% of R mechanisms, 26% of U mechanisms, and 23% of P mechanisms focused on the remaining pathologies, and accounted for 20% ($321,390,463) of funding. Conclusions The current landscape of NIH funding for brain tumor research indicates awarded mechanisms prioritize malignant intra-axial malignancies. Despite their prevalence, skull base neoplasia are far less represented in NIH funded studies.

The histone H3.3 K27M mutation suppresses Ser31phosphorylation and mitotic fidelity, which can directly drive gliomagenesis.

Serine 31 is a phospho-site unique to the histone H3.3 variant; mitotic phospho-Ser31 is restricted to pericentromeric heterochromatin, and disruption of phospho-Ser31 results in chromosome segregation defects and loss of p53-dependant G1 cell-cycle arrest.1,2,3,4 Ser31 is proximal to the H3.3 lysine 27-to-methionine (K27M) mutation that drives ∼80% of pediatric diffuse midline gliomas.5,6,7,8,9,10,11,12 Here, we show that expression of the H3.3 K27M mutant in normal, diploid cells results in increased chromosome missegregation and failure to arrest in the following G1. Expression of a non-phosphorylatable S31A mutant also drives chromosome missegregation, while the expression of a double K27M+ phosphomimetic S31E mutant restores mitotic fidelity and the p53 response to chromosome missegregation. We show that patient-derived H3.3 K27M tumor cells have decreased mitotic Ser31 phosphorylation and increased frequency of chromosome missegregation. CRISPR reversion of the K27M mutation to wild type (WT) restores phospho-Ser31 levels and results in a decrease in chromosome missegregation. However, inserting an S31A mutation by CRISPR into these revertant cells disrupts mitotic fidelity. Invitro and invivo analyses reveal that Chk1-the mitotic Ser31 kinase-is preferentially retained at pericentromeres in K27M-expressing tumor cells, compared with MLysine27-to-methionine mutation (M27K) isogenic revertants, correlating with both diminished phospho-Ser31 and mitotic defects. Interestingly, whereas M27K revertant cells do not form xenograft tumors in mice, H3.3 S31A cells do, similar to those formed by H3.3 K27M cells. Replication-competent avian leukosis virus splice-acceptor (RCAS)/cellular receptor for subgroup A avian sarcoma and leukosis virus (TVA) mice expressing S31A also form diffuse midline gliomas morphologically indistinguishable from K27M tumors. Together, our results reveal that the H3.3 K27M mutant alters H3.3 Ser31 phosphorylation, which, in turn, has profound impacts on chromosome segregation/cell-cycle regulation.

European standard clinical practice recommendations for paediatric high-grade gliomas

European standard clinical practice recommendations for paediatric high-grade gliomas

Real life data of ONC201 (dordaviprone) in pediatric and adult H3K27-altered recurrent diffuse midline glioma: Results of an international academia-driven compassionate use program.

H3K27-altered diffuse midline gliomas (DMG) have limited therapeutic options and a very poor prognosis. Encouraging responses were observed in early clinical trials with ONC201. As ONC201 was unavailable in Europe, a compassionate use program supported by the French Authorities was launched for patients at progression after standard of care radiotherapy. This program was developed by the French Society of Pediatric Oncology (SFCE) and Association des Neuro-Oncologues d'Expression Française in collaboration with the French National Agency For Medicines and Health Products Safety and Parents Associations. 174 patients (102 children, 72 adults) from 14 countries were treated from November 2021 to August 2023 at Gustave Roussy Institut (Villejuif, France). 37% received a second course of irradiation at the time of relapse. Median duration of treatment was 57 days or 1,9 months (mo) (range 1-456 days). Median OS since diagnosis for the whole cohort was 466 days or 15,5 mo (112-2612 days); 426 or 14,2 mo (112-2612 days) and 590 or 19,6 mo (range 160-1881) for children and adults, respectively (p=0.001). Median OS after ONC201 start was 143 days or 4,7 mo (1-711 days) for the whole cohort. Univariate and multivariable analysis identified site (thalamus) and age (older) as favorable prognostic factors. Reirradiation was associated with significantly longer survival after ONC201 start only in children. While the efficacy of ONC201 needs validation in a controlled randomized clinical trial, our real-life data support a better outcome for patients with thalamic tumors treated with ONC201. We demonstrated furthermore the feasibility of a successful academia-driven compassionate use program.

Human single cell RNA-sequencing reveals a targetable CD8+ exhausted T cell population that maintains mouse low-grade glioma growth

In solid cancers, T cells typically function as cytotoxic effectors to limit tumor growth, prompting therapies that capitalize upon this antineoplastic property (immune checkpoint inhibition; ICI). Unfortunately, ICI treatments have been largely ineffective for high-grade brain tumors (gliomas; HGGs). Leveraging several single-cell RNA sequencing datasets, we report greater CD8+ exhausted T cells in human pediatric low-grade gliomas (LGGs) relative to adult and pediatric HGGs. Using several preclinical mouse LGG models (Nf1-OPG mice), we show that these PD1+/TIGIT+ CD8+ exhausted T cells are restricted to the tumor tissue, where they express paracrine factors necessary for OPG growth. Importantly, ICI treatments with α-PD1 and α-TIGIT antibodies attenuate Nf1-OPG tumor proliferation through suppression of two cytokine (Ccl4 and TGFβ)-mediated mechanisms, rather than by T cell-mediated cytotoxicity, as well as suppress monocyte-controlled T cell chemotaxis. Collectively, these findings establish a previously unrecognized function for CD8+ exhausted T cells as specialized regulators of LGG maintenance.

REST-dependent glioma progression occurs independently of the repression of the long non-coding RNA HAR1A.

The long non-coding RNA (lncRNA), HAR1A is emerging as a putative tumour suppressor. In non-neoplastic brain cells, REST suppresses HAR1A expression. In gliomas REST acts as an oncogene and is a potential therapeutic target. It is therefore conceivable that REST promotes glioma progression by down-regulating HAR1A. To test this hypothesis, glioma clinical databases were analysed to study: (I) HAR1A/REST correlation; (II) HAR1A and REST prognostic role; (III) molecular pathways associated with these genes. HAR1A expression and subcellular localization were studied in glioblastoma and paediatric glioma cells. REST function was also studied in these cells, by observing the effects of gene silencing on: (I) HAR1A expression; (II) cancer cell proliferation, apoptosis, migration; (III) expression of neural differentiation genes. The same phenotypes (and cell morphology) were studied in HAR1A overexpressing cells. Our results show that REST and HAR1A are negatively correlated in gliomas. Higher REST expression predicts worse prognosis in low-grade gliomas (the opposite is true for HAR1A). REST-silencing induces HAR1A upregulation. HAR1A is primarily detected in the nucleus. REST-silencing dramatically reduces cell proliferation and induces apoptosis, but HAR1A overexpression has no major effect on investigated cell phenotypes. We also show that REST regulates the expression of neural differentiation genes and that its oncogenic function is primarily HAR1A-independent.

Neuroimmune-competent human brain organoid model of Diffuse Midline Glioma.

Pediatric high-grade gliomas, such as diffuse midline glioma (DMG), have a poor prognosis and lack curative treatments. Current research models of DMG primarily rely on human DMG cell lines cultured in vitro or xenografted into the brains of immunodeficient mice. However, these models are insufficient to recapitulate the complex cell-cell interactions between DMG and the tumor immune microenvironment (TIME), therefore fall short of accurately reflecting how efficacious therapeutic agents or combinations will be in the clinical setting. To address these challenges, we developed a neuroimmune-competent brain/tumor fusion organoid model system consisting entirely of human cells to investigate the interactions between DMG cells and the primary innate immune cells of the brain, microglia, in the TIME at both cellular and subcellular levels. We generated microglia-containing brain organoids (MiCBO) that carry morphologically mature, motile microglia and multiple subtypes of neurons to mimic the brain tumor microenvironment. These organoids were then fused with H3K27M mutant, TP53P27R/K132R DMG tumor spheroids to create the MiCBO-tumor fusion (MiCBO-TF) model. We utilized live imaging methods to simultaneously track the mobility of microglial cell bodies and the motility of their process, as well as the behavior of tumor cells within a human brain tissue environment. Our MiCBO-TF model faithfully recapitulated the diffuse infiltration pattern of DMG into brain tissue and revealed that microglial mobility and interactions with tumor cells are highly influenced by external factors and surrounding tissue environment. The MiCBO-TF model represents a powerful platform for both mechanistic investigations and the development of precision medicine approaches for DMG.