Histone H3 K27M Mutation Research Articles

CSIG-26. TARGETING EPIGENETIC DYSREGULATION AND ADAPTIVE RESISTANCE MECHANISMS IN DIPG/DMG

Abstract Diffuse intrinsic pontine gliomas (DIPG/DMG) are devastating pediatric brain tumors with very limited treatment options and a uniformly fatal prognosis. The recurrent histone H3K27M mutation in DIPG disrupts epigenetic regulation, leading to the hypothesis that this mutation-induced dysregulation creates a vulnerability to epigenetic targeting. We conducted a screening of compounds targeting epigenetic enzymes to identify potential inhibitors of patient-derived DIPG cell growth. High-throughput screening identified chaetocin, a fungal metabolite, as a potent inhibitor of DIPG cell growth. Chaetocin treatment selectively decreased proliferation and increased apoptosis in DIPG cells, significantly extending survival in DIPG xenograft models while restoring H3K27me3 levels. The loss of the H3K9 methyltransferase SUV39H1 also inhibited DIPG cell growth. Transcriptomic and epigenomic profiling showed that SUV39H1 loss or inhibition downregulated stemness and oncogenic networks, including growth factor receptor signaling. However, D2 dopamine receptor (DRD2) signaling adaptively upregulated, conferring resistance. Combining chaetocin with the DRD2 antagonist ONC201 or radiotherapy synergistically enhanced antitumor efficacy. This study reveals a therapeutic vulnerability in DIPG cells by targeting the SUV39H1-H3K9me3 pathway and compensatory signaling loops. Combining SUV39H1-targeting chaetocin with other agents, such as ONC201, may offer a new strategy for effective DIPG treatment. The findings suggest that chaetocin, by targeting and suppressing the H3K9me3 methyltransferase SUV39H1, inhibits DIPG tumor growth by downregulating stemness-related genes and growth factor signaling pathways. Overall, the study highlights a new therapeutic vulnerability in DIPG through the SUV39H1-H3K9me3 epigenetic pathway and compensatory signaling loops, suggesting an effective treatment strategy for DIPG.

Extracellular Histones Profiles of Pediatric H3K27-Altered Diffuse Midline Glioma.

Diffuse midline glioma, H3 K27-altered (DMG) is a fatal tumour that arises in the midline structures of the brain. When located in the pons, it is more commonly referred to as diffuse intrinsic pontine glioma (DIPG). DMG/DIPG is usually diagnosed when children are < 10 years, and it has a median overall survival of < 12 months after diagnosis. Radiological imaging is still the gold standard for DIPG diagnosis while the use of biopsy procedures led to our knowledge on its biology, such as with the identification of the canonical histone H3K27M mutation. However, the need to improve survival encourages the development of non-invasive, fast and inexpensive assays on biofluids for optimizing molecular diagnoses in DMG/DIPG. Here, we propose a rapid, new, imaging and epigenetics-based approach to diagnose DMG/DIPG in the plasma of paediatric patients. A total of 20 healthy children (mean age: 10.5 years) and 24 children diagnosed with DMG/DIPG (mean age: 8.5 years) were recruited. Individual histones (H2A, H2B, H3, H4, macroH2A1.1 and macroH2A1.2), histone dimers and nucleosomes were assayed in biofluids by means of a new advanced flow cytometry ImageStream(X)-adapted method. We report a significant increase in circulating histone dimers and tetramers (macroH2A1.1/H2B versus control: p value < 0.0001; macroH2A1.2/H2B versus control: p value < 0.0001; H2A/H2B versus control: p value < 0.0001; H3/H4 versus control: p value = 0.008; H2A/H2B/H3/H4 versus control: p value < 0.0001) and a significant downregulation of individual histones (H2B versus control: p value < 0.0001; H3 versus control: p value < 0.0001; H4 versus control: p value < 0.0001). Moreover, histones were also detectable in the cerebrospinal fluid (CSF) of patients with DMG/DIPG and in the supernatant of SF8628, OPBG-DIPG002 and OPBG-DIPG004 DMG/DIPG cell lines, with patterns mostly similar to each other, but distinct compared to blood plasma. In summary, we identified circulating histone signatures able to detect the presence of DMG/DIPG in biofluids of children, using a rapid and non-invasive ImageStream(X)-based imaging technology, which may improve diagnosis and benefit the patients.

DIPG-58. TARGETING DISORDERED DNA METHYLATION IN DIPG TO CONSTRAIN VARIABILITY AND INDUCE IMMUNE SIGNALING

Abstract BACKGROUND Diffuse Intrinsic Pontine Glioma (DIPG) is a universally fatal pediatric brain cancer characterized by the histone H3 K27M mutation. The known downstream consequences of this mutation include loss of repressive chromatin marks, global DNA hypomethylation, and altered gene expression. METHODS We sought to investigate the role of epigenetic variability as a basis of DIPG cellular heterogeneity and plasticity by using Whole Genome Bisulfite Sequencing (WGBS). Existing methods of analysis of WGBS are limited in that they average/smooth methylation data and fail to capture intrinsic variability. We performed (WGBS) on 23 primary patient samples of DIPG and applied an analysis that captures the variability of DNA methylation reads to characterize methylation stochasticity. We then sought to modulate the epigenome pharmacologically using a DNA methyltransferase inhibitor and assessed changes through RNA-Seq and immunopeptidomics. RESULTS We find that DIPG has a marked increase in methylation stochasticity (quantified as methylation entropy). Additionally, while DIPG is globally hypomethylated, it retains DNA methylation at specific regulatory regions, such as bivalent promoters, and key genes, such as FOXG1, CXCR4, and KLF4. We sought to reverse these changes using the DNA methyltransferase inhibitor, decitabine, in 4 DIPG neurosphere cell lines. Treatment with decitabine reversed the entropy seen in DIPG and induced innate immune signaling and interferon signaling in DIPG cells. Using RNA-seq, we found that decitabine treatment dramatically alters gene expression, including activation of endogenous retroviral elements, activation of interferon signaling, de-repression of hypermethylated targets, and expression of putative neoantigens, such as PRAME and DAZL. Immunopeptidomics profiling of MHC Class I bound canonical and non-canonical peptides of DIPG cell lines after decitabine treatment also revealed decitabine-induced differences. CONCLUSIONS Taken together, our study finds that the methylome of DIPG is highly disordered but is also highly responsive to pharmacologic modulation by hypomethylating agents. Furthermore, hypomethylating drugs can increase the immunogenicity of DIPG, thus offering the potential for future combination with immunotherapy.

DIPG-64. UNRAVELING H3K27M INTERACTIONS IN DIFFUSE MIDLINE GLIOMA

Abstract BACKGROUND Diffuse midline glioma (DMG) harboring the histone H3 K27M mutation, also known as diffuse intrinsic pontine glioma when it occurs in the pons, is a uniformly fatal pediatric brain tumor. We sought to better understand protein-protein interactions of the mutant histone in DMG. METHODS To address this, we carried out endogenous co-immunoprecipitation of histone H3 K27M from patient-derived DMG neurosphere cell lines, followed by LC-MS/MS identification of binding partners, and validation of binding by Western Blot. Moving beyond identification, we investigated the functional consequences of these interactions. RESULTS We identified putative novel interactors of H3 K27M with notable binding partners including histone chaperones and RNA helicases of the DDX family. We then explored the disruption of downstream effects resulting from this interaction by pharmacologically inhibiting DDX3 using the small molecule inhibitor RK-33, and assessed impact on viability and radiation sensitivity. CONCLUSIONS Understanding the protein interactome of the mutant histone can inform alternative ways for targeting DMG, thus enriching the therapeutic toolbox against this aggressive tumor. Functional characterization of binding partners holds the potential to identify novel therapeutic targets that cooperate with H3 K27M. The use of inhibitors targeting these partners could specifically destabilize oncohistone-dependent homeostasis and survival pathways and increase sensitivity to radiation and other therapies.

DIPG-90. NON-INVASIVE METABOLIC IMAGING OF DIFFUSE MIDLINE GLIOMAS AND THEIR RESPONSE TO THERAPY

Abstract BACKGROUND Diffuse midline gliomas (DMGs) harboring histone H3K27M mutations are devastating pediatric brain tumors. ONC201 is the first drug in decades to extend survival in DMG patients and is likely to be widely used for treatment of DMGs. However, magnetic resonance imaging (MRI), the gold standard for patient management, does not provide a reliable readout of response to therapy. The Warburg effect describes the propensity of tumor cells to increase glucose uptake and conversion to lactate. Deuterium metabolic imaging of the Warburg effect using [6,6’-2H]-glucose provides the unparalleled opportunity to obtain a biologically meaningful readout of treatment response. Therefore, the goal of this study was to assess the utility of [6,6’-2H]-glucose for DMG imaging. METHODS We performed expression profiling and deuterium metabolic imaging in patient-derived and syngeneic DMG models. RESULTS Our studies indicate that DMG cells upregulate key components of the Warburg effect, including SLC2A1, SLC2A3, HK2, PFKFB3, PGK1, and LDHA relative to normal astrocytes. Silencing the H3K27M mutation in DMG cells reduced glycolytic gene expression. Spatially resolved 2D chemical shift imaging at 3T showed that lactate produced from [6,6’-2H]-glucose was localized to tumor vs. normal brain in mice bearing intracranial tumors. ONC201 downregulated glycolytic gene expression in DMG cells, an effect that was accompanied by reduced lactate production from [6,6’-2H]-glucose. Importantly, lactate production from [6,6’-2H]-glucose was reduced following treatment with ONC201 in mice bearing intracranial tumors at 3T, at an early timepoint independent of MRI-detectable volumetric alterations and predictive of extended survival. CONCLUSIONS Our studies mechanistically link the H3K27M mutation with the Warburg effect. Importantly, they identify [6,6’-2H]-glucose as a novel contrast agent for visualizing the metabolic lesion and imaging early response to therapy in DMGs. Since [6,6’-2H]-glucose is a safe, orally administered agent, our studies have the potential to be rapidly translated to the clinic, where they will provide physicians with a much-needed tool to determine whether DMG patients are responding to therapy.

DNA methylation landscapes in DIPG reveal methylome variability that can be modified pharmacologically.

Diffuse intrinsic pontine glioma (DIPG) is a uniformly lethal brainstem tumor of childhood, driven by histone H3 K27M mutation and resultant epigenetic dysregulation. Epigenomic analyses of DIPG have shown global loss of repressive chromatin marks accompanied by DNA hypomethylation. However, studies providing a static view of the epigenome do not adequately capture the regulatory underpinnings of DIPG cellular heterogeneity and plasticity. To address this, we performed whole-genome bisulfite sequencing on a large panel of primary DIPG specimens and applied a novel framework for analysis of DNA methylation variability, permitting the derivation of comprehensive genome-wide DNA methylation potential energy landscapes that capture intrinsic epigenetic variation. We show that DIPG has a markedly disordered epigenome with increasingly stochastic DNA methylation at genes regulating pluripotency and developmental identity, potentially enabling cells to sample diverse transcriptional programs and differentiation states. The DIPG epigenetic landscape was responsive to treatment with the hypomethylating agent decitabine, which produced genome-wide demethylation and reduced the stochasticity of DNA methylation at active enhancers and bivalent promoters. Decitabine treatment elicited changes in gene expression, including upregulation of immune signaling such as the interferon response, STING, and MHC class I expression, and sensitized cells to the effects of histone deacetylase inhibition. This study provides a resource for understanding the epigenetic instability that underlies DIPG heterogeneity. It suggests the application of epigenetic therapies to constrain the range of epigenetic states available to DIPG cells, as well as the use of decitabine in priming for immune-based therapies.

Chaetocin-mediated SUV39H1 inhibition targets stemness and oncogenic networks of diffuse midline gliomas and synergizes with ONC201.

Diffuse intrinsic pontine gliomas (DIPG/DMG) are devastating pediatric brain tumors with extraordinarily limited treatment options and uniformly fatal prognosis. Histone H3K27M mutation is a common recurrent alteration in DIPG and disrupts epigenetic regulation. We hypothesize that genome-wide H3K27M-induced epigenetic dysregulation makes tumors vulnerable to epigenetic targeting. We performed a screen of compounds targeting epigenetic enzymes to identify potential inhibitors for the growth of patient-derived DIPG cells. We further carried out transcriptomic and genomic landscape profiling including RNA-seq and CUT&RUN-seq as well as shRNA-mediated knockdown to assess the effects of chaetocin and SUV39H1, a target of chaetocin, on DIPG growth. High-throughput small-molecule screening identified an epigenetic compound chaetocin as a potent blocker of DIPG cell growth. Chaetocin treatment selectively decreased proliferation and increased apoptosis of DIPG cells and significantly extended survival in DIPG xenograft models, while restoring H3K27me3 levels. Moreover, the loss of H3K9 methyltransferase SUV39H1 inhibited DIPG cell growth. Transcriptomic and epigenomic profiling indicated that SUV39H1 loss or inhibition led to the downregulation of stemness and oncogenic networks including growth factor receptor signaling and stemness-related programs; however, D2 dopamine receptor (DRD2) signaling adaptively underwent compensatory upregulation conferring resistance. Consistently, a combination of chaetocin treatment with a DRD2 antagonist ONC201 synergistically increased the antitumor efficacy. Our studies reveal a therapeutic vulnerability of DIPG cells through targeting the SUV39H1-H3K9me3 pathway and compensatory signaling loops for treating this devastating disease. Combining SUV39H1-targeting chaetocin with other agents such as ONC201 may offer a new strategy for effective DIPG treatment.

H3K27M mutant glioma: Disease definition and biological underpinnings.

High-grade glioma (HGG) is the most common cause of cancer death in children and the most common primary central nervous system tumor in adults. While pediatric HGG was once thought to be biologically similar to the adult form of disease, research has shown these malignancies to be significantly molecularly distinct, necessitating distinct approaches to their clinical management. However, emerging data have shown shared molecular events in pediatric and adult HGG including the histone H3K27M mutation. This somatic missense mutation occurs in genes encoding one of two isoforms of the Histone H3 protein, H3F3A (H3.3), or HIST1H3B (H3.1), and is detected in up to 80% of pediatric diffuse midline gliomas and in up to 60% of adult diffuse gliomas. Importantly, the H3K27M mutation is associated with poorer overall survival and response to therapy compared to patients with H3 wild-type tumors. Here, we review the clinical features and biological underpinnings of pediatric and adult H3K27M mutant glioma, offering a groundwork for understanding current research and clinical approaches for the care of patients suffering with this challenging disease.

Histone mutations in cancer.

Genes encoding histone proteins are recurrently mutated in tumor samples, and these mutations may impact nucleosome stability, histone post-translational modification, or chromatin dynamics. The prevalence of histone mutations across diverse cancer types suggest that normal chromatin structure is a barrier to tumorigenesis. Oncohistone mutations disrupt chromatin structure and gene regulatory mechanisms, resulting in aberrant gene expression and the development of cancer phenotypes. Examples of oncohistones include the histone H3 K27M mutation found in pediatric brain cancers that blocks post-translational modification of the H3 N-terminal tail and the histone H2B E76K mutation found in some solid tumors that disrupts nucleosome stability. Oncohistones may comprise a limited fraction of the total histone pool yet cause global effects on chromatin structure and drive cancer phenotypes. Here, we survey histone mutations in cancer and review their function and role in tumorigenesis.

Prognostic Indicators for H3K27M-Mutant Diffuse Midline Glioma: A Population-Based Retrospective Surveillance, Epidemiology, and End Results Database Analysis

Diffuse midline glioma with histone H3K27M mutation (H3K27M DMG) is a recently recognized World Health Organization grade IV glioma with a dismal prognosis. Despite maximal treatment, this high-grade glioma exhibits an estimated median survival of 9-12months. However, little is known with regards to prognostic risk factors for overall survival (OS) for patients with this malignant tumor. The aim of the present study is to characterize risk factors influencing survival in H3K27M DMG. This is a population-based retrospective study of survival in patients with H3K27M DMG. The Surveillance, Epidemiology, and End Results database was examined from the years 2018 to 2019 and data from 137 patients were collected. Basic demographics, tumor site, and treatments regimens were retrieved. Univariate and multivariable analyses were conducted to assess for factors associated with OS. Nomograms were built based on the results of the multivariable analyses. Median OS of the entire cohort was 13months. Patients with infratentorial H3K27M DMG exhibited worse OS compared to their supratentorial counterparts. Any form of radiation treatment resulted in a significantly improved OS. Most combination treatments significantly improved OS with the exception of the surgery plus chemotherapy group. The combination of surgery and radiation had the greatest impact on OS. Overall, the infratentorial location of H3K27M DMG portends a worse prognosis compared to their supratentorial counterparts. The combination of surgery and radiation had the greatest impact on OS. These data highlight the survival benefit in utilizing a multimodal treatment approach for H3K27M DMG.

DIPG-39. SIGNALING NETWORKS IN PEDIATRIC-TYPE DIFFUSE HIGH GRADE GLIOMAS

Abstract Pediatric-type diffuse high grade gliomas are aggressive brain cancers in children which to date lack effective treatment options and remain largely understudied. Even though genomic markers including histone H3 K27M and G34R mutations have been identified, their functional implications on signaling networks remain to be described. Phosphoproteomics might be able to uncover activated signaling pathways which could open up new paths for treatment. Here we analyzed formalin-fixed paraffin-embedded (FFPE) sections from K27M mutated, G34R mutated and histone H3 wild type patient tumors (n = 14) using phosphoproteomics. Our workflow not only enables the comprehensive characterization of phosphoserines and threonines but also of phosphotyrosines which, despite being rare modifications (0.1-1% of all phosphorylations), are known to play an important role in cancer. We found that signaling networks were distinct between the different tumor subtypes. For phosphotyrosines, tumor subtype accounted for the largest source of variation in the data (44% of variance) as determined by principle component analysis. The separation by subtype could also be seen from serine and threonine phosphoproteomics and proteomics, but was not as striking as for the phosphotyrosine data. Differential abundance analysis, partial least squares discriminant analysis and self-organizing maps revealed deregulated signaling networks between subtypes. The most downregulated pathway in K27M compared to wild type tumors was enriched for proteins involved in the epigenetic regulation of gene expression (FDR&amp;lt;5%), which is in accordance with the remodeling of the epigenome taking place in K27M mutated tumors. In addition, we could identify signaling networks (e.g. EGFR signaling) which were activated in a few individual patients independent of their subtype and might be targetable. Our study provides insights into the signaling landscape of pediatric-type diffuse high grade gliomas. Recognizing deregulated signaling networks across subtypes and in individual patients could offer new avenues for personalized therapy.

DIPG-43. CLINICAL AND MOLECULAR CHARACTERISTIC OF A NEW SUBTYPE OF DMG, H3K27-ALTERED WITH MAPK-ACTIVATING CO-DRIVER MUTATIONS

Abstract Diffuse midline gliomas (DMG) represent a big challenge in neuro-oncology. These tumors occur more frequently in children and are presently incurable. They are characterized by a K27M substitution in H3.1 or H3.3 histone tail or the overexpression of EZHIP (EZH Inhibitory Protein). These three alterations induce a global loss of trimethylation in H3K27 with a specific epigenic and transcriptomic remodeling. The additional oncogenic events and the clinical behavior are also distinct according to the driver event. Based on these differences, the H3K27-altered DMG is now classified in 4 subtypes by the latest edition of the WHO Classification of CNS tumors. Even with this new subclassification, the H3.3K27M subgroup still appears heterogenous. Recent publications reported that rare patients presenting a co-occurrence of H3.3K27M with BRAF or FGFR1 alterations tend to have a better prognosis. To better study the role of these co-driver alterations that activate the mitogen activated protein kinase (MAPK) signaling, we assembled a large pediatric and adult cohort of H3K27-altered DMG comprising 25 new DMG patients mutated in FGFR1 or BRAFV600E and 37 previous cases from the literature. We performed a comprehensive histological, radiological, genomic, transcriptomic and DNA methylome analysis on this extended cohort. Interestingly, the results show clear differences with other DMG subtypes, including: specific DNA methylation profile, senescence signature, better overall survival (median around 3 years), older age at diagnosis, specific histological and radiological presentations with calcifications or more circumscribed tumors. Additionally, in specific cases, we show that the MAPK-activating mutation occurred subsequently to the histone H3K27M mutation. In conclusion, DMG, H3K27-altered harboring MAPK activating mutations represent a new subtype of DMG also frequent in adults, and deserve further attention with respect to specific therapeutic challenges.

The Role of Histone H3-K27M Mutation in Preleukemic HSC Expansion

The Role of Histone H3-K27M Mutation in Preleukemic HSC Expansion

Conventional and Cross-Channel MR Radiomic Features do Not Predict Histone H3 Status in DIPG: Genomic and Clinical Evaluation of a Multi-Institutional Cohort

<h3>Purpose/Objective(s)</h3> Genomic profiling of diffuse pontine glioma (DIPG) has suggested distinct and clinically relevant molecular subgroups based on the presence and type of histone H3K27M mutation. Recent studies have demonstrated improved safety for biopsy, but sampling carries risks. We evaluated the impact of radiomic features on the molecular classification of 154 histologically confirmed and centrally reviewed DIPG. <h3>Materials/Methods</h3> Automatically segmented and manually reviewed tumor volumes were used to compute single & cross channel radiomic features from T1, T2, FLAIR, and T1+gadolinium MR sequences obtained from histone H3 WT (N=30) and H3K27M-mutant (N=124) DIPG. Radiomic feature stability was assessed when multiple pretreatment MRs were available using the concordance correlation coefficient. Random Forest, Logistic Regression, XGBoost, and Deep Learning classifiers were used to build predictive models of H3K27M status in a training dataset, after exclusion of correlated features. Model accuracy was assessed in the remaining validation dataset. <h3>Results</h3> Two hundred and twelve of 456 imaging features (46.4%) demonstrated stability (CCC, p<0.05) between pretreatment scans. Accuracy varied by method, but none surpassed the No Information Rate (82%). Model accuracy was not improved by efforts to remedy class imbalance (resampling and class weight adjustment). Several cross channel radiomic features were consistently selected by the models, indicating some predictive utility, although cross institutional scanning techniques were confounding. <h3>Conclusion</h3> While early efforts with single institutional data were encouraging, differences in MR technique and class imbalance seemed to limit the identification of stable radiomic features predictive of H3 status in this multi-institutional cohort. Biopsy remains key for determining trial eligibility and directing precision medicine.

HGG-03. PEDIATRIC BITHALAMIC GLIOMA H3K27M NEGATIVE AND EGFR POSITIVE: A DISTINCT ENTITY WITH POTENTIAL SENSIBILITY TO EGFR INHIBITORS

INTRODUCTION: Brain tumors are the most common solid tumors of childhood and optimal therapeutic strategies for many subtypes remain unknown. Bithalamic gliomas, in contrast with unilateral, have frequent mutations in the EGFR oncogene and only rare Histone H3 mutation. These EGFR mutations are small inframe insertions within exon 20 or missense mutations within exon 7 and occur in absence of gene amplification. CASE REPORT: A previously healthy 10-years-old boy with adequate neuropsychomotor development was admitted with a 5-day-long headache. A brain magnetic resonance imaging (MRI) showed an expansive midline lesion with thalamic extension. The tumor showed no diffusion restriction or contrast enhancement. An endoscopic septostomy and biopsy were performed.The histopahotology showed a diffused astrocytoma grade II. The immunohistochemistry was negative for IDH1 and 2, BRAF mutation, P53 and H3K27M. Next generation sequencing (NGS) ruled out histone H3K27M mutation and showed EGFR mutation in exon 7. The patient experimented clinical and radiological disease progression in a few weeks, confirming the high grade glioma despite the histopahological diagnosis.He received radiotherapy (Total dose 54Gy) and after radiation he started target therapy with Osimertinib, a third generation tirosin kinase inhibitor. As a toxiticy, he experienced neutropenia Grade 2. Disease evaluation performed after 2 cycles showed stable disease. DISCUSSION: Our case report represents a distintc molecular class of pediatric-type bithalamic glioma characterized by EGFR alteration and absence of H3K27M mutation. EGFR inhibition may represent a potential therapeutic strategy in these highly aggressive gliomas.

Diffuse Midline Gliomas With Histone H3 K27M Mutation in Adults and Children: A Retrospective Series of 164 Cases.

Diffuse midline glioma, H3 K27M-mutant (H3 K27M-mt DMG), is a rare and highly aggressive tumor that is more common in children than in adults. Few studies have compared the differences between pediatric and adult patients with this rare tumor. We here report our retrospective study of 94 adult and 70 pediatric cases of diffuse midline glioma. Surgical tumor samples were analyzed by routine histopathology and immunohistochemistry for H3 K27M, IDH1 R132H, ATRX, p53, OLIG2, glial fibrillary acidic protein, and Ki-67; Sanger sequencing for hot mutation spots in genes including H3F3A, HIST1H3B, IDH1, IDH2, TERT, and BRAF; and methylation-specific polymerase chain reaction for O 6 -methylguanine DNA methyltransferase promoter methylation. The most frequent anatomic locations in adult and pediatric patients were the thalamus and brainstem, respectively. Molecular profiling revealed higher frequencies of ATRX loss and H3.3 mutation in adult than in pediatric H3 K27M-mt DMGs. TERT promoter mutations and O 6 -methylguanine DNA methyltransferase promoter methylation were not detected in pediatric patients but were present in a few adult patients. During the follow-up period, 93/122 patients (70.1%) died from the disease, with a median survival time of 10.5 months (range: 1 to 104 mo). Kaplan-Meier analyses demonstrated that the prognosis was better for adult patients than the pediatric cohort (P=0.0003). Multivariate analyses indicated that patient age, primary tumor size, status of ATRX expression, and Ki-67 index were independent prognosticators. The present study showed that there were differences between adult and pediatric H3 K27M-mt DMGs in terms of the anatomic location of tumor, molecular changes, and prognosis.

Deploying Kinase Inhibitors to Study Pediatric Gliomas.

Pediatric midline gliomas are a uniformly fatal disease for which there is no cure. The location of these tumors makes surgical resection impossible, and so novel therapies are urgently needed to improve outcomes. The biology of these tumors is increasingly understood, with the histone H3K27M mutation playing a critical role in the pathogenesis of these tumors. Efforts to inhibit the growth of these tumors have also focused on inhibiting the Aurora kinase and Janus-associated kinase (JAK)/signal transducer and activator of transcription (STAT) pathway in order to disrupt tumor proliferation. A number of small molecule inhibitors of these kinases have shown promise in early studies. Screening and preclinical assessment of such inhibitors requires a functional assay to assess the degree of kinase inhibition. We detail here a luciferase-based reporter assay for STAT3 transcriptional activity that we have employed frequently in order to assess the efficacy of kinase inhibitors in pediatric gliomas. The assay we describe is specific to STAT3, but the overall methodology is generalizable to other downstream targets of the kinase of interest.

STMO-19 Impact of aggressive resection for glioblastoma of the thalamus with histone H3-K27M mutation

Glioblastoma of the thalamus occurs predominantly in childhood and young adulthood, and cases with histone mutations are thought to have a particularly poor prognosis. We studied tumor resection rate, age, type of adjuvant therapy, and histone gene mutations on progression-free survival (PFS) and overall survival (OS) in patients who underwent aggressive removal. Eight cases of thalamic glioblastoma were included in the study. The mean age at surgery was 36.1 years (10–74 years, 3 cases under 18 years). Tumor removal was performed from the parieto-occipital lobe to the thalamus via the lateral ventricles in all cases. In all cases, more than 90% of the contrast-enhancing lesions were removed. Postoperatively, one patient had sensory disturbance of the left upper limb, and the other had incomplete paralysis of the left upper and lower limbs, but both were able to walk with a cane. In the case of the patient with postoperative complications, the tumor was located in the vicinity of the internal capsule. All patients were treated with radiation therapy and temozolomide, and bevacizumab and Novo-TTF were used in cases after approval. All patients were able to return home and return to school or work after initial treatment. The mean progression-free survival (PFS) was 0.87 years, and overall survival (OS) was 1.95 years. Five patients had histone H3-K27M mutations, and three patients had no mutations. PFS and OS were 1.02 years and 0.62 years, respectively, and 2.53 years and 1.20 years, respectively, both of which were longer in patients with mutations (PFS; p=0.16, OS; p=0.23).Aggressive removal of glioblastoma of the thalamus may improve prognosis, especially in patients with histone H3-K27M mutations. In patients with tumors extending to the vicinity of the internal capsule, total removal may cause paralysis and sensory disturbance.

A multicenter analysis of the prognostic value of histone H3 K27M mutation in adult high-grade spinal glioma.

High-grade spinal glioma (HGSG) is a rare but aggressive tumor that occurs in both adults and children. Histone H3 K27M mutation correlates with poor prognosis in children with diffuse midline glioma. However, the role of H3 K27M mutation in the prognosis of adults with HGSG remains unclear owing to the rarity of this mutation, conflicting reports, and the absence of multicenter studies on this topic. The authors studied a cohort of 30 adult patients with diffuse HGSG who underwent histological confirmation of diagnosis, surgical intervention, and treatment between January 2000 and July 2020 at six tertiary academic centers. The primary outcome was the effect of H3 K27M mutation status on progression-free survival (PFS) and overall survival (OS). Thirty patients (18 males and 12 females) with a median (range) age of 50.5 (19-76) years were included in the analysis. Eighteen patients had H3 K27M mutation-positive tumors, and 12 had H3 K27M mutation-negative tumors. The median (interquartile range) PFS was 3 (10) months, and the median (interquartile range) OS was 9 (23) months. The factors associated with increased survival were treatment with concurrent chemotherapy/radiation (p = 0.006 for PFS, and p ≤ 0.001 for OS) and American Spinal Injury Association grade C or better at presentation (p = 0.043 for PFS, and p < 0.001 for OS). There were no significant differences in outcomes based on tumor location, extent of resection, sex, or H3 K27M mutation status. Analysis restricted to HGSG containing necrosis and/or microvascular proliferation (WHO grade IV histological features) revealed increased OS for patients with H3 K27M mutation-positive tumors (p = 0.017). Although H3 K27M mutant-positive HGSG was associated with poor outcomes in adult patients, the outcomes of patients with H3 K27M mutant-positive HGSG were somewhat more favorable compared with those of their H3 K27M mutant-negative HGSG counterparts. Further preclinical animal studies and larger clinical studies are needed to further understand the age-dependent effects of H3 K27M mutation.

Erratum. A multicenter analysis of the prognostic value of histone H3 K27M mutation in adult high-grade spinal glioma.

Erratum. A multicenter analysis of the prognostic value of histone H3 K27M mutation in adult high-grade spinal glioma.