Adult Gliomas Research Articles

Small extracellular vesicles as a novel liquid biopsy approach for glioblastoma.

2073 Background: Glioblastoma (GBM) remains the most common and aggressive primary malignant brain tumor, and afflicted patients have limited options and poor overall survival. Diagnosis, prognosis, and assessment of treatment effectiveness is hampered by the absence of readily available sensitive, tumor specific, non-invasive blood-based assays which could be followed serially. Small extracellular vesicles (sEV) are nano-sized (≤200 nm) membrane bound bodies secreted by all cells, encapsulating cargo reflective of their parent cells. sEV have emerged as promising molecular indicator of a disease condition. Here, we report the feasibility of isolating glioma specific sEV (sEVglioma) from the plasma and characterizing those for GBM specific molecular biomarkers. Methods: Plasma samples were collected from patients (n=31) diagnosed with adult gliomas (including grade 3 and 4 GBM, grade 2 and 3 astrocytoma) and healthy individuals (n=9). Total sEV (TE) population was isolated from plasma by a modified precipitation (ExoQuick) method. Next, sEVglioma were isolated from the TE by an immunoprecipitation approach employing specific surface markers targeting cellular origin of gliomas, including astrocyte (GLAST and EAAT2), oligodendrocyte precursor cell (OSP and MOG), and neural stem cell (CD133). sEVglioma were characterized for size and concentration by nanoparticle tracking analyses; surface expression of glioma specific biomarkers by nano-flow cytometry and confocal microscopy; and the expression of a panel of specific miRNAs by RT-PCR. Lastly, sEVglioma were assessed by digital PCR for IDH1 status (wild type or mutated). Results: The average size of isolated sEVglioma was less than 200nm. Importantly, compared to TE, sEVglioma showed significant enrichment for glioma specific biomarkers such as ephrin type-A receptor 2 (14.7-fold), tenascin C (22.7-fold), and glial fibrillary acidic protein (8.4-fold) by nano-flow cytometry. Similarly, sEVglioma, but not TE, demonstrated high expression of EGFRvIII (3.6-fold), a known biomarker for GBM. These results were confirmed by confocal microscopy. Interestingly, expression of specific miRNAs (miR-9a-5p, miR-16-5p, miR-21-5p) in sEVglioma was higher in glioma patients with shorter survival (<12 months) compared to patients with longer survival (>20 months). Lastly, we successfully detected the existence of wild type IDH1 and absence of mutated IDH1 R132H in sEVglioma from GBM patients. This approach was validated in sEV isolated from the conditioned media of IDH1-wild type GBM cell lines (A172 and T98G) and a IDH1-mutated cell line (BT54). Conclusions: We present a novel approach to isolate sEVglioma from blood that could serve as a liquid biopsy, offering valuable molecular and genetic information. This approach promises early detection, potential to distinguish pseudo-progression, and assessment of treatment effectiveness with remarkable precision.

NFKBIA deletions reshape the epigenome antithetical to the IDH mutation and indication of prognosis in diffuse gliomas.

2083 Background: Genetic alterations help predict the clinical behavior of diffuse gliomas, but some variability remains uncorrelated. The NFKBIA gene at 14q13.2 encodes IkBa, a protein that regulates the activity of NF-kB in the cytoplasm. Evidence that, in chromatin, nuclear NFKBIA dynamically interacts with histones H2A and H4 to regulate polycomb-dependent transcriptional repression and, thus, stem cell maturation and lineage specification and our characterization of NFKBIA as a tumor suppressor in glioblastoma prompted our investigation of the relationship of NFKBIA deletions to other genetic markers, alterations in the methylome, and the clinical course of gliomas. Methods: We analyzed the genetic profiles of 2,343 WHO grade 2 to 4 diffuse gliomas in multiple clinically well-characterized patient populations, including national randomized phase III consortium trial RTOG 9802, to determine whether incorporation of NFKBIA deletions could enhance the prognostic value of current molecular descriptions. Results: We demonstrate that haploinsufficient deletions of NFKBIA display distinct patterns of occurrence in relation to other genetic markers, including driver mutations IDH, TERT, ATRX, and PTEN, 1p19q codeletion, and CDKN2A/B deletion, and are disproportionally present at recurrence. NFKBIA haploinsufficiency is associated with unfavorable patient outcomes, independent of genetic and clinicopathologic predictors. NFKBIA deletions reshape the DNA and histone methylome antipodal to the IDH mutation. The methylome changes facilitated through NFKBIA deletions engender a transcriptome landscape partly reminiscent of H3K27M mutant pediatric gliomas and are highly enriched for neural stem cell and neurogenesis genes bearing repressive H3K27 marks. Our findings imply that the NFKBIA deletion in adult gliomas and the H3K27M mutation in pediatric diffuse midline gliomas define aggressive disease subtypes that may share an epigenetic state reflecting a common PRC2 loss-of-function phenotype antipodal to the quasi PRC2 gain-of-function phenotype of IDH mutant gliomas and their favorable clinical course. Lower-grade gliomas harboring NFKBIA deletions behave much like high-grade gliomas. In IDH mutant gliomas, NFKBIA deletions are common in tumors with a clinical course similar to that of IDH wildtype tumors. A sparse, easily interpretable, and externally validated nomogram model for estimating individual patient survival in IDH mutant gliomas, incorporating NFKBIA deletion and current best-established genetic and clinicopathologic factors, confirms that NFKBIA deletions predict comparatively brief survival. Conclusions: NFKBIA haploinsufficiency aligns with distinct epigenome changes, portends a poor prognosis, and should be incorporated into clinical models predicting the disease fate of diffuse gliomas.

Predicting therapeutic clinical trial enrollment for underrepresented patients in neuro-oncology using supervised machine learning.

1614 Background: Despite the unique ability of machine learning (ML) techniques to uncover complex interactive effects in datasets, studies exploring predictors of clinical trial enrollment have largely used standard statistical methods to discern associations. Furthermore, there have been limited applications of ML to close existing disparities in clinical trial enrollment of underrepresented patients in neuro-oncology. This study aims to use supervised machine learning to define and validate primary contributors of therapeutic clinical trial enrollment for a) all patients, b) women and c) NIH-designated minority patients with low- and high-grade glioma. Methods: Adult glioma patients who received care from the UCSF Brain Tumor Center between 1997- 2017 were identified in a prospective registry. Bootstrap forest (BF) and Recursive Partitioning (RP) models were created by randomly dividing patients in a 70/30 split into development (DEV) and validation (VAL) cohorts among all patients, women, and NIH-designated minority patients, separately. Model performance was assessed using the area under the curve (AUC) in the DEV and VAL cohorts. Results: Among 1042 patients, 350 patients (33.6%) enrolled in a therapeutic clinical trial. There were 445 women (42.7%), of which 144 (32.4%) enrolled, and 141 minority patients (13.5%), of which 39 (27.7%) enrolled. For all patients, in order of decreasing influence, the BF model selected median neighborhood household income, age, neighborhood poverty level, distance from hospital, tumor location, tumor volume, treatment with chemotherapy, occupation, KPS, insurance status, employment status, seizure at presentation, and volumetric extent of resection (EOR) to predict trial enrollment (DEV AUC: 0.984; VAL AUC: 0.746). For women, the BF model selected distance from hospital, age, household income, neighborhood poverty level, tumor location, treatment with chemotherapy, and KPS for trial prediction (DEV AUC: 0.972; VAL AUC: 0.746), whereas for minority patients, the BF model selected neighborhood poverty level, age, occupation, distance from hospital, tumor volume, insurance status, employment status, and EOR to predict trial enrollment (DEV AUC: 0.9830; VAL AUC: 0.769). The RP model for women designated those with non-White race as less likely to enroll (DEV AUC: 0.735; VAL AUC: 0.665) while the RP model for minority patients characterized those who preferred a non-English language or who were divorced or widowed as less likely to enroll (DEV AUC: 0.775; VAL AUC: 0.601). Conclusions: Supervised machine learning models achieved similar predictive performance among patient subgroups, while uncovering interactions between gender identity, minority status, and sociodemographic variables. These findings can guide targeted recruiting efforts to advance equitable trial enrollment for women and minorities.

Click-chemistry mediated synthesis of OTBN-1,2,3-Triazole derivatives exhibiting STK33 inhibition with diverse anti-cancer activities

There is a continuous and pressing need to establish new brain-penetrant bioactive compounds with anti-cancer properties. To this end, a new series of 4′-((4-substituted-4,5-dihydro-1H-1,2,3-triazol-1-yl)methyl)-[1,1′-biphenyl]-2-carbonitrile (OTBN-1,2,3-triazole) derivatives were synthesized by click chemistry. The series of bioactive compounds were designed and synthesized from diverse alkynes and N3-OTBN, using copper (II) acetate monohydrate in aqueous dimethylformamide at room temperature. Besides being highly cost-effective and significantly reducing synthesis, the reaction yielded 91–98 % of the target products without the need of any additional steps or chromatographic techniques. Two analogues exhibit promising anti-cancer biological activities. Analogue 4l shows highly specific cytostatic activity against lung cancer cells, while analogue 4k exhibits pan-cancer anti-growth activity. A kinase screen suggests compound 4k has single-digit micromolar activity against kinase STK33. High STK33 RNA expression correlates strongly with poorer patient outcomes in both adult and pediatric glioma. Compound 4k potently inhibits cell proliferation, invasion, and 3D neurosphere formation in primary patient-derived glioma cell lines. The observed anti-cancer activity is enhanced in combination with specific clinically relevant small molecule inhibitors. Herein we establish a novel biochemical kinase inhibitory function for click-chemistry-derived OTBN-1,2,3-triazole analogues and further report their anti-cancer activity in vitro for the first time.

P.102 Integration of Ultrasensitive electroluminescent immunoassay and cell-free DNA methylation analysis for the non-invasive discrimination of adult diffuse gliomas

Background: Gliomas are highly aggressive brain tumors with nearly universal recurrence rate. Despite this, the ability to accurately predict tumor recurrence relies solely on serial MRI imaging, highlighting the need for prognostic biomarkers. Due to the low accuracies of individual serum markers, we have proposed the use of an integrated, multi-platform approach to biomarker discovery. Methods: A cohort of 107 glioma plasma samples, including 30 pairs, underwent plasma proteomic, consisting of a panel of serum proteins (FABP4, GFAP, NFL, Tau and MMP3,4 &7) quantified through ultrasensitive electrochemiluminescence multiplexed immunoassays, and plasma DNA methylation analysis, captured through cell-free methylated DNA immunoprecipitation and high-throughput sequencing. Results: Unsupervised hierarchal clustering revealed robust separation of primary and recurrent tumors through plasma proteomics, associated with a distinct plasma methylation signature. NFL, Tau and MMP3 levels differed between primary and recurrent samples; pair-wise analysis revealed increased in NFL and Tau concentrations upon recurrence. Tau levels predicted outcome independent of WHO Grade and IDH status. A predictive model created through the integration of the proteomic and methylation signatures revealed an AUC of 0.83. Conclusions: The combination of DNA methylation and plasma proteomics showcases that an integrative approach may improve the ability of these techniques for the serial monitoring of gliomas patients.

Glioma.

Gliomas are primary brain tumours that are thought to develop from neural stem or progenitor cells that carry tumour-initiating genetic alterations. Based on microscopic appearance and molecular characteristics, they are classified according to the WHO classification of central nervous system (CNS) tumours and graded into CNS WHO grades 1-4 from alow to high grade of malignancy. Diffusely infiltrating gliomas in adults comprise three tumour types with distinct natural course of disease, response to treatment and outcome: isocitrate dehydrogenase (IDH)-mutant and 1p/19q-codeleted oligodendrogliomas with the best prognosis; IDH-mutant astrocytomas with intermediate outcome; and IDH-wild-type glioblastomas with poor prognosis. Pilocytic astrocytoma is the most common glioma in children and is characterized by circumscribed growth, frequent BRAF alterations and favourable prognosis. Diffuse gliomas in children are divided into clinically indolent low-grade tumours and high-grade tumours with aggressive behaviour, with histone 3 K27-altered diffuse midline glioma being the leading cause of glioma-related death in children. Ependymal tumours are subdivided into biologically and prognostically distinct types on the basis of histology, molecular biomarkers and location. Although surgery, radiotherapy and alkylating agent chemotherapy are the mainstay of glioma treatment, individually tailored strategies based on tumour-intrinsic dominant signalling pathways have improved outcome in subsets of patients.

Clinical characteristics and prognostic factors of adult brainstem gliomas: A retrospective analysis of histologically-proven 40 cases.

To illustrate the clinical characteristics and prognostic factors of adult patients pathologically confirmed with brainstem gliomas (BSGs). Clinical data of 40 adult patients pathologically diagnosed with BSGs admitted to Beijing Shijitan Hospital from 2009 to 2022 were recorded and retrospectively analyzed. The primary parameters included relevant symptoms, duration of symptoms, Karnofsky performance status (KPS), tumor location, type of surgical resection, diagnosis, treatment, and survival. Univariate and multivariate analyses were evaluated by Cox regression models. The gliomas were located in the midbrain of 9 patients, in the pons of 14 cases, in the medulla of 5 cases, in the midbrain and pons of 6 cases and invading the medulla and pons of 6 cases, respectively. The proportion of patients with low-grade BSGs was 42.5%. Relevant symptoms consisted of visual disturbance, facial paralysis, dizziness, extremity weakness, ataxia, paresthesia, headache, bucking, dysphagia, dysacousia, nausea, dysphasia, dysosmia, hypomnesia and nystagmus. 23 (57.5%) patients accepted stereotactic biopsy, 17 (42.5%) patients underwent surgical resection. 39 patients received radiotherapy and 34 cases were treated with temozolomide. The median overall survival (OS) of all patients was 26.2 months and 21.5 months for the median progression-free survival (PFS). Both duration of symptoms (P = .007) and tumor grading (P = .002) were the influencing factors for OS, and tumor grading was significantly associated with PFS (P = .001). Duration of symptoms for more than 2 months and low-grade are favorable prognostic factors for adult patients with BSGs.

The spectrum of microvascular patterns in adult diffuse glioma and their correlation with tumor grade.

Primary brain tumors constitute the leading cause of cancer-related mortality. Among them, adult diffuse gliomas are the most common type, affecting the cerebral hemispheres and displaying a diffuse infiltrative pattern of growth in the surrounding neuropil that accounts for about 80% of all primary intracranial tumors. The hallmark feature of gliomas is blood vessel proliferation, which plays an important role in tumor growth, tumor biological behavior, and disease outcome. High-grade gliomas exhibit increased vascularity, the worst prognosis, and lower survival rates. Several angiogenic receptors and factors are upregulated in glioblastomas and stimulate angiogenesis signaling pathways by means of activating oncogenes and/or down-regulating tumor-suppressor genes. Existing literature has emphasized that different microvascular patterns (MVPs) are displayed in different subtypes of adult diffuse gliomas. We examined the distribution and biological characteristics of different MVPs in 50 patients with adult diffuse gliomas. Haematoxylin and eosin staining results, along with periodic acid-Schiff and CD34 dual-stained sections, were examined to assess the vascular patterns and correlate with different grades of diffuse glioma. The present observational study on adult diffuse glioma evaluated tumor grade and MVPs. Microvascular sprouting was the most common pattern, while a bizarre pattern (type 2) was associated with the presence of a high-grade glioma. Vascular mimicry was observed in 6% of cases, all of which were grade 4 gliomas. This study supplements the role of neo-angiogenesis and aberrant vasculature patterns in the grading and progression of adult diffuse gliomas, which can be future targets for planning treatment strategies.

782: Treatment Dilemma of H3K27M Mutant Midline Glioma in Adults

782: Treatment Dilemma of H3K27M Mutant Midline Glioma in Adults

RNA splicing analysis deciphers developmental hierarchies and reveals therapeutic targets in adult glioma.

Widespread alterations in RNA alternative splicing (AS) have been identified in adult gliomas. However, their regulatory mechanism, biological significance, and therapeutic potential remain largely elusive. Here, using a computational approach with both bulk and single-cell RNA-Seq, we uncover a prognostic AS signature linked with neural developmental hierarchies. Using advanced iPSC glioma models driven by glioma driver mutations, we show that this AS signature could be enhanced by EGFRvIII and inhibited by in situ IDH1 mutation. Functional validations of 2 isoform switching events in CERS5 and MPZL1 show regulations of sphingolipid metabolism and SHP2 signaling, respectively. Analysis of upstream RNA binding proteins reveals PTBP1 as a key regulator of the AS signature where targeting of PTBP1 suppresses tumor growth and promotes the expression of a neuron marker TUJ1 in glioma stem-like cells. Overall, our data highlights the role of AS in affecting glioma malignancy and heterogeneity and its potential as a therapeutic vulnerability for treating adult gliomas.

Personalized prognosis stratification of newly diagnosed glioblastoma applying a statistical decision tree model

PurposeGlioblastoma (GBM) is the most frequent glioma in adults with a high treatment resistance resulting into limited survival. The individual prognosis varies depending on individual prognostic factors, that must be considered while counseling patients with newly diagnosed GBM. The aim of this study was to elaborate a risk stratification algorithm based on reliable prognostic factors to facilitate a personalized prognosis estimation early on after diagnosis.MethodsA consecutive patient cohort with confirmed GBM treated between 2010 and 2021 was retrospectively analyzed. Clinical, radiological, and molecular parameters were assessed and included in the analysis. Overall survival (OS) was the primary outcome parameter. After identifying the strongest prognostic factors, a risk stratification algorithm was elaborated with estimated odds of survival.ResultsA total of 462 GBM patients were analyzed. The strongest prognostic factors were Charlson Comorbidity Index (CCI), extent of tumor resection, and adjuvant treatment. Patients with CCI ≤ 1 receiving tumor resection had the highest survival odds (88% for 10 months). On the contrary, patients with CCI > 3 receiving no adjuvant treatment had the lowest survival odds (0% for 10 months). The 10-months survival rate in patients with CCI > 3 receiving adjuvant treatment was 56% for patients younger than 70 years and 22% for patients older than 70 years.ConclusionA risk stratification algorithm based on significant prognostic factors allowed a personalized early prognosis estimation at the time of GBM diagnosis, that can contribute to a more personalized patient counseling.

National trends in the treatment of adult diffuse midline gliomas: a rare clinical scenario.

Diffuse midline gliomas (DMG) include all midline gliomas with a point mutation to the histone H3 gene resulting in the substitution of a lysine with a methionine (K27M). These tumors are classified as World Health Organization grade 4 with a mean survival between 9- and 19-months following diagnosis. There is currently no standard of care for DMG, and palliative radiation therapy has been proven to only extend survival by months. Our current study aims to report current treatment trends and predictors of the overall survival of DMG. We searched the National Cancer Database for adult patients treated for DMG from 2016 to 2020. Patients were required to have been treated with primary radiation directed at the brain with or without concurrent chemotherapy. Univariable and multivariable Cox regressions were used to determine predictors of overall survival. Of the 131 patients meeting the inclusion criteria, 113 (86%) received radiation and chemotherapy. Based on multivariable Cox regression, significant predictors of survival were Charlson-Deyo comorbidity index and race. Patients with a Charlson-Deyo score of 1 had 2.72 times higher odds of mortality than those with a score of 0. Patients not identifying as White or Black had 2.67 times higher odds of mortality than those identifying as White. The median survival for all patients was 19 months. Despite being considered ineffective, chemotherapy is still administered in most adult patients diagnosed with DMG. Significant predictors of survival were Charlson-Deyo comorbidity index and race.

Latest Developments in Magnetic Resonance Imaging for Evaluating the Molecular Microenvironment of Gliomas.

The 2021 World Health Organization (WHO) Classification of Tumors of the Central Nervous System has brought a transformative shift in the categorization of adult gliomas. Departing from traditional histological subtypes, the new classification system is guided by molecular genotypes, particularly the Isocitrate Dehydrogenase (IDH) mutation. This alteration reflects a pivotal change in understanding tumor behavior, emphasizing the importance of molecular profiles over morphological characteristics. Gliomas are now categorized into IDH-mutant and IDH wildtype, with significant prognostic implications. For IDH-mutant gliomas, the concurrent presence of Alpha-Thalassemia/mental retardation syndrome X-linked (ATRX) gene expression and co-deletion of 1p19q genes further refine classification. In the absence of 1p19q co-deletion, further categorization depends on the phenotypic expression of CDKN2A/B. Notably, IDH wildtype gliomas exhibit a poorer prognosis, particularly when associated with TERT promoter mutations, EGFR amplification, and +7/-10 co-deletion. Although not part of the new guidelines, the methylation status of the MGMT gene is crucial for guiding alkylating agent treatment. The integration of structural and functional Magnetic Resonance Imaging (MRI) techniques may play a vital role in evaluating these genetic phenotypes, offering insights into tumor microenvironment changes. This multimodal approach may enhance diagnostic precision, aid in treatment planning, and facilitate effective prognosis evaluation of glioma patients.

Clinical Characteristics and Treatment Approaches for H3K27-altered Diffuse Midline Glioma in Adolescents and Young Adults (P4-5.024)

Clinical Characteristics and Treatment Approaches for H3K27-altered Diffuse Midline Glioma in Adolescents and Young Adults (P4-5.024)

Clinical Assessment of Magnetic Resonance Spectroscopy and Diffusion-Weighted Imaging in Diffuse Glioma: Insights Into Histological Grading and IDH Classification.

To assess the diagnostic utility of clinical magnetic resonance spectroscopy (MRS) and diffusion-weighted imaging (DWI) in distinguishing between histological grading and isocitrate dehydrogenase (IDH) classification in adult diffuse gliomas. A retrospective analysis was conducted on 247 patients diagnosed with adult diffuse glioma. Experienced radiologists evaluated DWI and MRS images. The Kruskal-Wallis test examined differences in DWI and MRS-related parameters across histological grades, while the Mann-Whitney U test assessed molecular classification. Receiver Operating Characteristic (ROC) curves evaluated parameter effectiveness. Survival curves, stratified by histological grade and IDH classification, were constructed using the Kaplan-Meier test. The cohort comprised 141 males and 106 females, with ages ranging from 19 to 85 years. The Kruskal-Wallis test revealed significant differences in ADC mean, Cho/NAA, and Cho/Cr concerning glioma histological grade (P < .01). Subsequent application of Dunn's test showed significant differences in ADC mean among each histological grade (P < .01). Notably, Cho/NAA exhibited a marked distinction between grade 2 and grade 3/4 gliomas (P < .01). The Mann-Whitney U test indicated that only ADC mean showed statistical significance for IDH molecular classification (P < .01). ROC curves were constructed to demonstrate the effectiveness of the specified parameters. Survival curves were also delineated to portray survival outcomes categorized by histological grade and IDH classification. Conclusions: Clinical MRS demonstrates efficacy in glioma histological grading but faces challenges in IDH classification. Clinical DWI's ADC mean parameter shows significant distinctions in both histological grade and IDH classification.

Abstract LB193: Enhanced single cell DNA methylation analysis using combinatorial indexing

Abstract The epigenetic landscape of the human brain undergoes a plethora of changes during malignant transformation. In recent years, DNA methylation-based epigenetic modifications have been widely studied using traditional techniques like bisulfite sequencing and enzymatic methyl sequencing (EM-seq). However, these methods analyze bulk cell populations and lack the granularity of single-cell analysis. Although advances in single-cell analysis have revolutionized our understanding of cellular heterogeneity and functional diversity within complex biological systems, they are still costly, low throughput, and laborious. To address these challenges, ScaleBio has pioneered combinatorial indexing technology, enabling a significant increase in cell throughput. This method utilizes the cell itself as a compartment to perform 2-3 rounds of sequential barcoding in a plate-based workflow, eliminating the need for complex instrumentation. This technology has been successfully adapted to assess DNA methylation at the single-cell level offering a robust, affordable, high-throughput protocol that enhances yield, diversity, and coverage. In this study we used ScaleBio's single-cell methylation kit to investigate DNA methylation patterns during oncogenesis using cancer cells with widespread DNA methylation changes, such as human isocitrate dehydrogenase (IDH) mutant glioma cells at the single-cell level. The IDH gene family, comprising of IDH1, IDH2, and IDH3, encodes enzymes involved in the tricarboxylic acid (TCA) cycle. IDH1/2 mutations are present in over 80% of low-grade gliomas while IDH-mutant gliomas constitute about 1/5th of all adult diffuse gliomas, thus making them one of the most common brain tumor subtypes. As such, IDH mutations have emerged as attractive therapeutic targets for glioma treatment. By uncovering DNA methylation patterns at the single cell level, we provide here an epigenetic map to better understand this complex disease and better inform clinical discoveries. We achieved high cell recovery and robust cytosine coverage throughout our analysis of single cell methylomes isolated from human glioma tumor tissue. Using this data we generated a ranked list of the top hypo- and hypermethylated genomic regions and identified cell type specific clusters seen in different pathological states by looking at Differentially Methylated Regions (DMR) uncovering unique single-cell methylation profiles that may be obscured by bulk or pseudo-bulk analysis. These data show that the ScaleBio single-cell methylation workflow offers increased sensitivity, specificity, and accuracy in identifying DNA methylation sites when compared to other techniques while offering a comprehensive view of methylomes and providing insights into cellular heterogeneity and trajectories. Citation Format: Sanika Khare, Dominic Skinner, Maggie Nakamoto, Hosu Sin, Ashley Woodfin, Eric Pu, Lin Lin, Jason Koth, Beth Walczak. Enhanced single cell DNA methylation analysis using combinatorial indexing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB193.

The new morphologic classification of the hand motor cortex with magnetic resonance imaging in glioma patients

PurposeThe hand motor cortex (HMC) is a reliable anatomical landmark for identifying the precentral gyrus. The current study aimed to investigate the morphology of HMC on axial MRI of glioma patients, propose a new morphological classification of HMC and analyze the effect of tumors on the morphology of HMC. MethodsA retrospective study of 276 adult right-handed glioma patients was conducted. The morphology of HMC was assessed using T2 axial images. Subsequently, the distribution of morphological subtypes was compared between the bilateral hemispheres and the tumor-affected and healthy hemispheres. Finally, the influence of tumor pathology on the morphology of HMC was investigated. ResultsA new morphological classification of HMC with four subtypes (Ω, ε, Ω-ε and ε-Ω) was proposed. No significant difference was identified in the distribution of morphological subtypes between the bilateral hemispheres (p = 0.0901, Chi-square test), or between the tumor-affected and healthy hemispheres (p = 0.3507, Chi-square test), and the morphology of HMC between the bilateral hemispheres were consistent (p < 0.0001, Kappa test). In addition, a significant difference was identified in the distribution of morphological subtypes between astrocytic and oligodendroglial tumors (p = 0.0135, Chi-square test). ConclusionIn the current study, we proposed a new morphological classification of HMC, and found that tumor could affect the morphology of HMC in glioma patients. The results can help our clinical practice, enabling us to further understand the spatial structure of the cerebral hemispheres.

Presurgical diagnosis of diffuse gliomas in adults: Post-WHO 2021 practical perspectives from radiologists in neuro-oncology units

The 2021 World Health Organization classification of CNS tumours was greeted with enthusiasm as well as an initial potential overwhelm. However, with time and experience, our understanding of its key aspects has notably improved. Using our collective expertise gained in neuro-oncology units in hospitals in different countries, we have compiled a practical guide for radiologists that clarifies the classification criteria for diffuse gliomas in adults. Its format is clear and concise to facilitate its incorporation into everyday clinical practice. The document includes a historical overview of the classifications and highlights the most important recent additions. It describes the main types in detail with an emphasis on their appearance on imaging. The authors also address the most debated issues in recent years. It will better prepare radiologists to conduct accurate presurgical diagnoses and collaborate effectively in clinical decision making, thus impacting decisions on treatment, prognosis, and overall patient care.

Abstract 3480: Alterations in the tumor microenvironment and key signaling pathways in naturally-occurring canine gliomas mirror those seen in human patients

Abstract Background: Malignant gliomas are the most common type of primary brain tumors, with patient outcomes that are generally dismal. Recently, pet dogs have been assessed as a valuable model in which to study gliomas. Gliomas in pet dogs occur at similar rates to those seen in humans, and a recent study comparing canine and human gliomas identified high similarity in terms of mutational rates, aneuploidy, the timing of mutations, and methylation patterns. Here, we further compare naturally-occurring canine and human gliomas, focusing on the tumor microenvironment (TME) and key pathways dysregulated in human gliomas. Methods: Spontaneously occurring gliomas from adult and pediatric human, and canine patients were utilized for this study. RNA, whole genome/whole exome, and bisulfite sequencing data from adult and canine samples were downloaded from the Genomic Data Commons and the National Cancer Institute’s Integrated Canine Data Commons, respectively. Pediatric tumor RNA-seq and genomic data were obtained from the Gabriella Miller Kids First database. Normal adult human and canine brain tissue served as control tissue. Only tumors with a clear diagnosis of astrocytoma, oligodendroglioma, or oligoastrocytoma were included in this study. Results: Overall, we found that key canonical pathways that are altered in human gliomas are also altered in canine gliomas. A comparison of high-grade gliomas in pet dogs to normal canine brain tissues showed significant abnormal gene expression in 3 canonical oncogenic pathways of human GBM: the TP53, RB1, and RTK/RAS/PI3K pathways. Similarities between species included increased expression of PDGF, and receptors PDGFRA and PDGFRB. Frequent copy number alterations and mutations were also observed in PDGFRA and EGFR. Differences between species include the mutation rate of TP53, which we found to be mutated frequently in adults but not in pediatric or canine gliomas, however, expression of TP53 as assessed by RNA-seq was significantly increased in both adult and canine gliomas. IDH1, which drives methylation, was significantly overexpressed in adults but underexpressed in canine. Correspondingly, each of the promotor regions of TERT, PD1 and MGMT was hypermethylated in adults, but hypomethylated in canine. Although an analysis of the TME from RNA-seq data revealed an influx of immune cells in adult, pediatric and canine gliomas, there was a concurrent influx of immunosuppressive cells. Gene expression profiles of astrocytomas and oligodendrogliomas show differences in alterations of immune-related and TME-specific pathways. Conclusion: We found that similar TME and pathway alterations were observed between human and canine gliomas, and that TME alterations were different between canine astrocytomas and oligodendrogliomas. The canine TME, like that in humans, appears to be immunosuppressive. Citation Format: Nadia A. Lanman, Sagar Utturkar, Harish Kothandaraman, Deepika Dhawan, Danni Liu, Min Zhang, Matthew Beyers, Deborah W. Knapp, R. Timothy Bentley. Alterations in the tumor microenvironment and key signaling pathways in naturally-occurring canine gliomas mirror those seen in human patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3480.

Abstract 5109: Novel acylfulvene LP184 shows single agent and combinatorial efficacy with PARP inhibitors in atypical teratoid rhabdoid tumors

Abstract Atypical Teratoid Rhabdoid Tumor (AT/RT) is an aggressive form of pediatric brain cancer that spreads quickly and leads to survival rates of less than 40%. Current treatments are insufficient at reducing this poor prognosis. A hallmark feature of ATRT is a SMARCB1 mutation. Illudins are a class of cytotoxic compounds with activity against pediatric solid tumors, including AT/RT. LP-184 is a novel synthetic illudin with improved brain penetration and activity against adult high-grade glioma orthotopic xenografts. We tested LP-184 against a battery of AT/RT cell lines including BT37, CHLA06, CHLA05, and CHLA266. LP-184 decreases viability at nanomolar concentrations with IC50s ranging from 9.91nM - 23.92nM. LP-184 decreased proliferation as measured by immunofluorescence and confirmed by western blots (BT37 p=0.0001, CHLA06 =0.0001, CHLA05=0.033). LP-184 also induced apoptosis as demonstrated in immunofluorescent images and western blots (BT37 p=0.0001, CHLA06 =0.0001, CHLA05=0.0015, CHLA266 p=0.002). Furthermore, LP-184 shows strong synergy with the PARP inhibitor Rucaparib, suggesting that inhibition of DNA repair potentiates LP-184 activity. LP-184 reduces viable cell count by as much as 50% and combination with Rucaparib further decreases viability by 75% (BT37=0.0001, CHLA06=0.0002, CHLA05=0.0077). The dual therapy also demonstrates cytostatic and cytotoxic effects as confirmed by immunofluorescence and western blots (BT37 BrdU = 0.0004, BT37 CC3 = 0.0002, CHLA06 BrdU = 0.0033, CHLA06 CC3 = 0.0117 compared to control). Further studies in vivo are being conducted to test single agent and combination therapies of LP-184 and Rucaparib in ATRT, as our data indicates that the two could provide a compelling treatment option for patients with this poor prognosis brain tumor. Citation Format: Abigail Tindall, Hyuk J. Kwon, Istabraq Musa, Tyler Findlay, Su Chan Lee, Charles Eberhart, Eric Raabe. Novel acylfulvene LP184 shows single agent and combinatorial efficacy with PARP inhibitors in atypical teratoid rhabdoid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5109.