bluuebunny/crossref_metadata_2025 huggingface dataset:
EPCO-35. IDENTIFICATION OF DIVERSE IMMUNE PHENOTYPES IN NF-1 GLIOMA BY SINGLE NUCLEI GENE EXPRESSION ANALYSIS
Authors: Garofano Luciano , Oh Young Taek , Najac Ryan D , Ceccarelli Michele , Sanson Marc , Lasorella Anna , Iavarone Antonio
Published: November 2023

Neurofibromatosis type 1 (NF-1) is the most common cancer predisposition syndrome in which 15-20% of affected individuals develop glioma. Large scale DNA and RNA bulk profiling showed the high molecular complexity of NF-1 glioma with the tumor cellular ecosystem constituted by multiple malignant clones and heterogenous immune microenvironment. However, the composition and function of infiltrating cells was mostly hidden in the bulk tumor mass, and the extended granularity of NF-1 glioma immune microenvironment remained still unexplored. Here, to address this challenge, we collected glioma samples from 53 NF-1 patients including 27 high-grade and 26 low-grade tumors, and we analyzed their gene expression at the highest resolution through single nuclei RNA sequencing. A total of 288,372 single cells have been classified by integrating multiple computational approaches (including genomic copy number inference, gene signature enrichment, pathway-based deconvolution and integrative non-negative matrix factorization). The non-tumor cell compartment (124,082 cells, 43%) has been dissected for the deep characterization of each cell type that populate the microenvironment of NF-1 glioma. We unraveled the complexity of the immune infiltration and identified different subpopulations exhibiting specific immune functions within myeloid and lymphoid components. Different glioma niches have been revealed by comparing the relative composition of the immune microenvironment across the tumors. Recruitment and activation of cytotoxic CD8+ T cells and natural killers by an active crosstalk with dendritic and pro-inflammatory myeloid cells defined an immune-supportive phenotype that can mediate a potential anti-tumor response in low-grade NF-1 glioma. Regulatory T cell infiltration and effector T cell exhaustion, instead, induced immune suppression in another tumor niche. Conversely, the complete absence of lymphocytes characterized a large set of cold tumors, mostly high-grade glioma. The elucidation of the complex immune interplay in the different tumor niches provides novel insights for the application of immunotherapies in NF-1 glioma patients.
EPCO-42. A SYSTEMS SCALE MODEL FOR PERSONALIZED PRECISION ONCOLOGY APPLICATIONS TO GBM
Authors: Turkarslan Serdar , He Yu , Hothi Parvinder , Murie Carl , Nicolas Abran , Kannan Kavya , Park James H , Pan Min , Patel Anoop , Cobbs Charles , Baliga Nitin S
Published: November 2023

Glioblastoma (GBM) is the most aggressive and lethal type of brain tumor, and its treatment remains challenging due to the complexity of the underlying molecular mechanisms. Here, we present gbmMINER, a causal and mechanistic transcriptional regulatory network model for GBM that integrates multi-omics and clinical data with a new network quantization approach using the MINER algorithm. gbmMINER accurately grouped 9,728 genes into 3,797 regulons and identified 179 transcriptional programs that stratify GBM into 23 disease states, associated with distinct clinical outcomes. We demonstrate that the activity profiles of regulons and programs in the quantized network model accurately predict overall survival, identifying patients with significantly longer OS of up to 42 months. Through extensive characterization using independent cohort datasets and genome-wide CRISPR screening data, we demonstrate the accuracy of gbmMINER in delineating causal and mechanistic insights into well-known and novel prognostic somatic mutations in GBM. Finally, through high-throughput drug screening, we demonstrate that the activity of regulons and programs accurately predicts the sensitivity of patient-derived glioma stem-like cells (PD-GSCs) to anticancer drugs. In theory, gbmMINER could be implemented to better stratify patients based on prognosis and potentially identify precision therapeutic strategies based on network activity.
EPCO-43. STING EPIGENETIC SILENCING IN GBM: IMPLICATIONS FOR INFLAMING THE IMMUNE MICROENVIRONMENT AND DESIGNING COMBINATION THERAPIES
Authors: Low Justin , Bowie Michelle , Wertman Virginia , Baker Eric , Mangoli Avani , Gibson Emiley , Gomar Rodrigo de La Vega , Stevenson Kevin , Fuller Rebecca , Hostettler Janell , Brown Michael , Waitkus Matthew , Reitman Zachary , Ashley David
Published: November 2023

Primary brain tumors including glioblastoma (GBM) are notoriously resistant to immunotherapy due in part to disrupted innate immunity. The stimulator of interferon genes (STING) pathway is a key component of innate immunity and senses pathogenic cytosolic DNA, stimulating the production of type I interferons (IFN) and pro-inflammatory cytokines. We have recently shown that STING signaling is silenced in the neoplastic compartment of the GBM tumor microenvironment, but remains intact in vascular and immune cells. Methylation analysis of bulk GBM tumor samples revealed a STING promoter region that is highly methylated and strongly correlates inversely with STING RNA expression, suggesting epigenetic control of STING expression. Methylation array analysis of patient specimens demonstrates that such promoter hypermethylation is unique amongst innate immune genes, and STING RNA expression correlates strongly with markers of immune inflammation. STING epigenetic silencing is also present in normal fetal and adult brains, suggesting that STING silencing occurs early in neural development and may provide an immunosuppressive environment conducive to tumorigenesis. Treatment with the blood brain barrier-penetrant DNA methyltransferase inhibitor Decitabine demethylates the STING promoter and activates interferon stimulated genes (ISG). STING knockout experiments and treatment with the DNMT1-selective inhibitor GSK-3685032 suggest that STING expression is necessary but not sufficient for ISG activation. These results suggest that innate immune silencing is a fundamental characteristic of GBM that underlies its intrinsic therapy resistance, yet may also represent a vulnerability that can be exploited by epigenetic therapies to inflame the GBM tumor microenvironment. However, epigenetic therapies that de-represses STING may need to be coupled with DNA damaging agents, immunotherapy, or STING agonists for optimal immune inflammation.
EPCO-46. CHARACTERIZING ATYPICAL TERATOID RHABDOID TUMOR SUBTYPE ENHANCER INTERACTION LANDSCAPE
Authors: Ho Ben , Fan Xiaolian , Xu Liming , Huang Annie
Published: November 2023

Atypical Teratoid Rhabdoid Tumor (ATRT) is one of the most aggressive pediatric tumors of the central nervous system (CNS). The majority of ATRTs are characterized by the recurrent bi-allelic loss of the SWI/SNF nucleosome remodeling complex core component gene, SMARCB1, or SMARCA4 in rare cases. Despite its bland genome, three ATRT subgroups “SHH”, “TYR”, and “MYC” were discovered with unique molecular profiles. Also, distinct activating histone mark H3K27ac profiles between molecular subgroups were identified, suggesting subgroup-specific regulatory networks through enhancers. However, comprehensive cis-regulatory network descriptions in ATRT are lacking. Here, we aim to elucidate ATRT subgroup pathogenesis through its dysregulated enhancer-promoter interactions. We have created a regulatory mutational profile of the three ATRT subgroups using whole-genome sequencing method of 60 ATRT tumors and matching genome-wide H3K27ac profiles on 16 tumors. To investigate mutation burden on cis-regulations, we have employed high-throughput Hi-C chromatin immunoprecipitation (HiChIP) technique to directly map enhancer sequences involved in DNA-looping with high specificity and sensitivity. Recent findings from our lab suggest that activating interaction PDGFRB confer to therapeutics venerability in the MYC subgroup. Here, our preliminary analysis shows a hub of interactions near PDGFRB reveals an extensive interaction hub with long-range enhancer interactions extending as far as 1500Kb, suggesting a much more complicated regulatory picture than previously expected. Interestingly, we have identified long-range DNA interactions between PDGFRB and H3K27ac marks upstream of its gene body and overstretching into other gene elements. This result suggests a potential alternative activation mechanism for MYC cell lines. Our next steps are to perform performing additional HiChIP assays on other ATRT cell lines from other subgroups to capture the full range of ATRT’s heterogeneity. Comprehensive mapping of the non-coding genome and enhancer regulatory network would help identify critical pathogenic elements underlying ATRT biology and provide insights into therapeutic targets.
EPCO-54. GENETIC PROFILE OF SKULL BASE CHONDROSARCOMAS AND RESPONSE TO TREATMENT IN PATIENTS WITH IDH1 MUTATED TUMORS
Authors: Eaton Jessica , Parada Carolina Da Silva , Parrish Oscar , Tucker Mallory , Zhao Tina , Delegard Jennifer , Lassiter Eric , Ruzevick Jacob , Cranmer Lee , Ferreira Manuel
Published: November 2023

Chondrosarcomas are uncommon tumors, with an incidence of 0.1-0.3 cases per 100,000 people. Current treatment consists of maximal safe surgical resection. The addition of adjuvant radiation reduces 5-year mortality by about 50%, but recurrence rates at 5 years are still over 30%. Targeted treatment options are needed to improve outcomes for patients with these tumors. IDH catalyzes the oxidative carboxylation of isocitrate to produce a-ketoglutarate. IDH1 mutations been identified across multiple cancers, included gliomas, AML, cholangiocarcinomas, and chondrosarcomas. These mutations are thought to impair cell differentiation and lead to tumorigenesis. OBJECTIVES: We present 2 cases of IDH1 mutant skull base chondrosarcomas that were treated with an IDH inhibitor. Both patients had radiographic involution of their tumors with no progression 2 years later. We describe the genetic profile of chondrosarcomas, elucidate associations between tumor mutations and clinical course, and investigate the mechanism of treatment response. METHODS: We performed a retrospective cohort analysis of 38 patients with skull base chondrosarcomas. Cox proportional hazards models were performed. Whole exome sequencing (WES) was performed on tumor samples, including multiple samples taken at various time points during the clinical course in 3 patients. RESULTS: A total of 38 patients with skullbase chondrosarcomas underwent surgery between 2000 and 2020. Mean follow-up time was 83.3 ± 107.7 months. Mean progression free survival time was 54.4 ± 71.5 months. Mortality was 15.8%. WES was available for 29 patients. Of these, 22 patients had IDH1 mutations (75.9%). Of these 22, the most common amino acid change was at the R132C position (45.5%). There was a trend towards increased mortality in patients that were IDH1 wildtype (42.8%) vs IDH1 mutant (13.6%). CONCLUSION: While IDH1 mutations are possible therapeutic targets with exciting preliminary responses, treatment response is likely complex and dependent on multiple mutations. Further analyses and validation studies are underway.
DISP-02. PATTERNS IN THE INCIDENCE OF BRAIN METASTASIS BY RACE AND ETHNICITY: A SYSTEMATIC REVIEW
Authors: Gomez David , Feng Jeffrey , Dicharry Holly , Cheok Stephanie , Musabelliu Erion , Zada Gabriel
Published: November 2023

INTRODUCTION

Despite advancements in cancer treatment, the incidence of brain metastases (BM) continues to rise which necessitates risk factor analyses. Although current literature indicates racial variance in BM incidence, there exists a major knowledge gap in understanding associations between race/ethnicity, BM incidence, and subtypes which emphasizes the need for a systematic review. We aimed to analyze the relationship between BM incidence, race/ethnicity, and primary cancer type.

METHODS

Using PRISMA guidelines, a systematic review of PubMed and Ovid databases from January 2000 to January 2023 for terms related to BM, ethnicity and race, in conjunction with incidence was conducted. Inclusion criteria comprised peer-reviewed journals with ages > 18, sample size > 100, primary malignancy diagnosis with evidence of BM, and descriptions of patient race or ethnicity.

RESULTS

Of 806 identified studies, 11 articles primarily utilizing US data were included for final analysis. Lung and bronchus cancers, revealed the highest incidence of BM in Asian patients, followed by Black, White, and American Indian/Alaska Natives (P< .001), despite overall increased incidence of primary cancer in Black patients. Breast cancer revealed highest BM incidence in American Indian/Alaska Natives (5.9%), followed by Black (5.0%), White (3.6%), and Asian/Pacific Islanders (3.5%) (P< .001). When compared to White and Hispanics only, Black patients had greater incidences of BM (OR: 2.26, 95% CI: 1.57–3.25). Lower incidence of BM for esophageal cancer was observed in Black patients compared to White patients (OR=0.38; 95% CI: (0.16–0.89); P= 0.026). No significant differences were observed in BM incidence for bladder, prostate, or non-small cell and small cell lung cancers.

CONCLUSIONS

Our review suggests that BM incidence does vary amongst racial/ethnic groups dependent on primary cancer type. Differences may be due to numerous factors, underscoring the need for more work with inclusive, diverse cohorts to tackle BM disparities.
DISP-05. UNDERSTANDING THE INDIVIDUAL CHALLENGES AND EXPERIENCES OF YOUNG ADULTS WITH A DIAGNOSIS OF GLIOBLASTOMA AND HIGH-GRADE ASTROCYTOMA
Authors: Devaraja Kaviya , Avery Jonathan , Daniels Maureen , Edelstein Kim , Gupta Abha , Tsang Derek
Published: November 2023

High-grade gliomas are highly aggressive and fatal primary malignant brain tumors in adults with ineffective existing treatment methods. Older adults are greatly impacted by high-grade gliomas as they are more common among this population. Young adults (individuals aged 18-39) are uniquely impacted by high-grade glioma. However, there are few resources and information available to address these unique needs. The purpose of this study is to explore the lived experience of this population to inform the development of resources to help address their specific needs. A qualitative descriptive design drawing on thematic analysis was chosen to conduct and analyze interviews with young adult high-grade glioma patients at the Princess Margaret Cancer Center. Interviews focused on patient experiences as a high-grade glioma patient at Princess Margaret Cancer Center, the challenges they face and changes they would like implemented. A coding framework was created to determine emerging themes using qualitative data analysis software NVivo 10. To date, 5 interviews (1 men; 4 women; age range 19-37) have been completed. Interviews described the challenges living with high-grade glioma as a young adult and the changes in resources and support services patients would like implemented. Experiences highlighted 1) difficulty accepting this change in life and disruptions brought upon life goals and plans at the young adult age; 2) an overall lack of young adult high-grade glioma specific education, advocacy and support resources 3) A call for more community building and connecting so patients do not feel alone through this diagnosis. These patient interviews highlight a connection between the young adult age and high-grade glioma diagnosis and the challenges experienced and the services required. These results will serve as the foundation to advocate for the creation of tools that cater to patient needs of young adult high-grade glioma patients.
DISP-11. PROMINENT FRONTAL BOSSING AND BLINDNESS FOLLOWING SUBTOTAL RESECTION OF LOW-GRADE MENINGIOMA: HIGHLIGHTING HEALTH DISPARITIES
Authors: White Jessica , Lim Sanghee , Neth Bryan , Carabenciov Ivan , Stitt Derek , Mustafa Rafid
Published: November 2023

Low-grade meningiomas with subtotal resection carry significantly shorter recurrence-free survival rates than those with gross total resection. We report the natural history of a case of low-grade meningioma after subtotal resection and review the literature. We aim to highlight known global health disparities in oncology treatment by describing a case of meningioma progression following subtotal resection. A 40-year-old Kenyan woman presented locally with headache, nausea, and vision loss over approximately a six month time period. A 5 cm olfactory groove meningioma was discovered, and she subsequently underwent subtotal resection that was likely limited due to hemorrhagic complications. Over the following two years, she developed progressive dizziness, nausea, gait instability, difficulty performing tasks, and visual loss prompting medical evaluation at our institution. Physical examination demonstrated blindness, bilateral proptosis with severe vertical gaze palsy, and prominent frontal bossing. MRI Brain revealed a 9 cm enhancing mass arising from the cribriform plate with elevation of an ununited overlying frontal craniotomy flap and apparent meningoceles extending through the presumed osteotomy bilaterally. She underwent successful resection with pathology demonstrating CNS WHO Grade 1 meningioma. Her postoperative neurologic exam showed subtle improvement, specifically in regards to orientation questions. In this patient, bone flap displacement from prior craniotomy allowed significant interval tumor growth while minimizing mass effect on brain parenchyma. This case highlights global health disparities in low-grade meningioma management related to appropriate healthcare access in underserved patients.
DISP-15. DISPARITIES IN THE AVAILABILITY OF NEURO-ONCOLOGY CLINICAL TRIAL SUPPORTING INFRASTRUCTURE IN THE UNITED STATES
Authors: Kim Yeonju , Armstrong Terri , Gilbert Mark , Celiku Orieta
Published: November 2023

BACKGROUND

Barriers to clinical trial access have significant implications for patient care and disproportionally impact rural and socioeconomically disadvantaged populations. Expanding on reported disparities in neuro-oncology trial availability, we assessed whether existing networks of clinical providers and collaboratives, including NCI’s National Clinical Trials Network (NCTN) and Community Oncology Research Program (NCORP), can effectively bridge these disparities.

METHODS

Locations of adult neuro-oncology trial sites, UCNS-certified neuro-oncologists, NCTN Main Members, NCORP Community Affiliates, and general oncologists reporting to Centers for Medicare/Medicaid Services were obtained, mapped to zip code tabulation areas (ZCTAs), and annotated with US Census population and geography data and the Neighborhood Atlas Area Deprivation Index (ADI). Regression and spatial analyses were conducted assessing the role of geography, socioeconomic disadvantage, and population on infrastructure accessibility.

RESULTS

We identified 1976 neuro-oncology trials, 586 NCTN institutions, 962 NCORP sites, 306 neuro-oncologists, and 863 general oncologists located in just 8% of all ZCTAs, inhabited by 19% of the US population. All trial-supporting infrastructure components were more likely to exist in more populated, geographically neighboring regions (OR >1, p< 0.00001). Trial sites, NCTN institutions, and neuro-oncologists served ZCTAs with less disadvantage (OR=0.99, p=0.03958; OR=0.99, p< 0.00001; OR=0.98, p< 0.00001), while NCORP served more disadvantaged areas (OR=1.01, p=0.00102) and general oncologists were distributed similarly across ADI (OR=1.00, p=0.94317). Investigating potentially underutilized infrastructure, 2 neuro-oncologists, 8 NCTN institutions, 10 NCORP sites, and 107 general oncologists were located more than 25 miles from utilized trial sites.

CONCLUSION

The identified disparities in neuro-oncologists and trial-supporting institutions reflect disparities in trial-site access and point to broader disparities in neuro-oncology care access. NCORP sites reach more socioeconomically disadvantaged populations, but the overall sparsity of trial-supporting networks indicates that the existing infrastructure cannot effectively bridge trial-access barriers and novel approaches including telehealth and decentralized trial designs may be necessary to promote equity.
DISP-16. RACIAL/ETHNIC DIFFERENCES OF PEDIATRIC BRAIN TUMORS IN PATIENT DERIVED ORTHOTOPIC XENOGRAFT (PDOX) MODEL DEVELOPMENT AND DRUG RESPONSES DETECTED BY HIGH-THROUGHPUT DRUG SCREENING
Authors: Abdallah Aalaa , Du Yuchen , Li Xiao-Nan , Qi Lin , Kogiso Mari , Braun Frank
Published: November 2023

Brain tumors are the leading cause of cancer-related death in children. While the last decade has ushered in significant advances in molecular subtyping of pediatric brain tumors, little is known about the biological differences among racial/ethnic populations. We previously completed high-throughput Screening (HTS) in 12 malignant glioma and 13 medulloblastoma models. For each model, cultured xenograft cells (primary or cell line) were maintained both as a classic monolayer and as 3D neurospheres then treated for 3-7 days with a library of ~8,000 drugs/investigational agents, each at 4 different doses (0.01~ 10 µM). The antitumor activities were evaluated by the level of suppressed cell proliferation that was determined by the area under the curve (AUC) for which our cutoff value was set at 0.75. In the current study, we performed a retrospective analysis to determine the race/ethnicity of these completed PDOX models. Our cohort of medulloblastoma models included 3 models from children who self-identified as Hispanic and 5 models from children who self-identified as, that allowed for a statistical analysis (t-test) to compare the differences between these two racial/ethnic groups. From the 8,000 drugs, we identified 11 drugs (mostly NSC compounds) that were equally active in both Hispanic and White children (i.e. commonly shared drugs), and 442 drugs that showed significantly different (P< 0.05) activities between the Hispanic and the White medulloblastomas grown as neurospheres and treated for 7 days. The difference of active drugs (AUC >0.75) was even more prominent. Compared with 38 active drugs in White children (i.e., privately active drugs, including Bortezomib, YM155, Carfilzomib, Daporinad, GMX-1778, Dalanzomib, Cucurbitacin, Bafilomycin, Vincristin and Mitoxantrone), the number was 0 for Hispanic children. Our data indicates a significant difference in drug response across different racial/ethnic groups and provides a strong rationale for additional examination of those differences with broader coverage of tumors.
IMMU-02. IS DUAL AGENT IMMUNOTHERAPY SHIFTING THE EPIDEMIOLOGY OF MELANOMA BRAIN METASTASES? A REAL-WORLD ANALYSIS AND SINGLE-INSTITUTION VALIDATION
Authors: Bhanja Debarati , Wilding Hannah , Moeckel Camille , Hong Jinpyo , Baroz Angel , Stahl Caleb , Ozair Ahmad , Dao Joseph , Sivik Jeff , Drabick Joseph , Pameijer Colette , Ahluwalia Manmeet , Mansouri Alireza
Published: November 2023

INTRODUCTION

Dual agent immunotherapy (dIT) has been paradigm changing in melanoma brain metastasis (MBM). Recent clinical trials have supported the role of dIT for upfront management of small, asymptomatic MBM. Yet, its potential role in extending brain metastasis free survival and decreasing MBM incidence overall has been inadequately explored. Objective: To compare new brain metastasis incidence, median overall survival (OS), and brain metastasis free survival (BMFS) in melanoma patients treated with dIT versus single immunotherapy (sIT).

METHODS

A real-world deidentified database collating clinical information from 92 organizations (TriNetX, Inc) was queried. Melanoma patients without brain metastases prior to immunotherapy were stratified by treatment (anti-CTLA4 [sIT] and combination anti-CTLA4/ anti-PD1 [dIT]) and propensity score matched. A complementary single-institution retrospective cohort study analyzed melanoma patients treated from 2012-2019. The incidence of new asynchronous MBMs after immunotherapy initiation was compared. Median OS and BMFS were compared via log-rank tests and Cox proportional-hazards model.

RESULTS

TriNetX identified 8,686 melanoma patients who received immunotherapy (4,585 dIT; 4,101 sIT). MBM prevalence was 9.6%, and 15.6%, for the dIT and sIT cohorts, respectively (p < 0.0001). DIT was associated with a lower likelihood of developing MBM compared to sIT (OR [95%CI], 0.64 [0.61-0.77]). After propensity score matching on demographics and significant comorbidities, OS was not statistically different between treatment groups. On single-institution analysis, 222 melanoma patients were included (89 dIT; 45 anti-CTLA4; 88 anti-PD1). Patients were predominantly stage III at diagnosis (43%) with PD-L1 expression (51%) and BRAF (43%), and NRAS wildtype (50%) mutational status. BMFS was significantly extended in the dIT cohort compared to the anti-CTLA4 or anti-PD1 alone cohorts (406, 217, 139 days, respectively; p< 0.0001). On Cox-proportional hazards model, no covariates significantly contributed to the BMFS difference.

CONCLUSION

These data highlight the impact of combination anti-CTL4/ anti-PD1 immunotherapy in decreasing BM incidence in melanoma.
IMMU-09. IDENTIFICATION OF A NEW THERAPEUTIC ANTIGEN FOR GLIOBLASTOMA USING A MONOCLONAL ANTIBODY LIBRARY FROM PATIENT-DERIVED TUMOR SPHERES
Authors: Kuroda Hideki , Kijima Noriyuki , Tachi Tetsuro , Murakami Koki , Hirayama Ryuichi , Okita Yoshiko , Kagawa Naoki , Hosen Naoki , Kishima Haruhiko
Published: November 2023

Glioblastoma (GBM) has a poor prognosis despite intensive treatment by surgery, radiation, and chemotherapy, thus new treatment strategies are urgently needed. Various innovative cancer therapies targeting cancer-specific cell surface antigens, such as chimeric antigen receptor T cell therapy, are developed and more cell surface antigens that is highly specific for GBM cells are needed. Although extensive transcriptome analyses or proteomic analysis of GBM cells were performed, few transcripts specific for GBM cells have been identified. However, GBM cell-specific antigen epitopes formed by post-translational modifications of proteins may have been missed by transcriptome or proteomic analysis, and could still be discovered by thoroughly searching for cancer-specific monoclonal antibodies. In this study, we aim to identify GBM-specific antigens using a monoclonal antibody library from patient-derived tumor spheres. Approximately 25,000 monoclonal antibody-producing hybridomas were establishment using Balb/c mice and patient derived tumor spheres. Among them, two antibodies that bind to glioblastomas and not to normal brain cells were selected and we identified the antigen by the expression cloning method. The antigen is a cell adhesion molecule and has been reported to be involved in the progression of solid tumors and is expected to be a tumor-specific antigen. These results indicate that the strategy shown in this study is useful for identifying antigens that are potentially useful as targets for GBM therapy.
IMMU-12. TUMOR EXPRESSION OF CD83 PROMOTES IMMUNE CLEARANCE OF GLIOMA
Authors: Curry Rachel , McDonald Malcolm , Lozzi Brittney , Cervantes Alexis , Lee Zhung-Fu , Harmanci Arif , Rosenbaum Anna , He Peihao , Mohila Carrie , Deneen Benjamin , Serin-Harmanci Akdes , Rao Ganesh
Published: November 2023

Glioblastoma (GBM) remains deadly with minimal therapeutic improvement over the past decades. A hallmark of GBM is an immunosuppressive microenvironment, which includes anergic and suppressive T-cells. Antigen presentation is a critical component to successful activation of anti-tumor T cell responses and are dysregulated in GBM. To better understand how GBM cells modulate antigen presenting processes, we examined expression of antigen presentation genes in our single cell RNA-sequencing (scRNA-seq) cohort consisting of 18 GBM samples from 12 different human patients. Unexpectedly, we found a rare population of tumor cells with high expression of CD83, a marker of activated antigen presenting cells (APCs) that stabilizes MHC-II and CD86 expression. In an immunocompetent GFP-labeled piggyBac in utero electroporation (pB-IUE) model of GBM, we validated the existence of dually labeled CD83+GFP+ tumor cells using FACS image streaming. In vivo overexpression of CD83 (CD83OE) in tumor cells prolonged survival compared to control and CD83 knockout (CD83KO) tumors. In vitro, tumor cell lines derived from CD83OE tumors increased expansion and activation of co-cultured CD8+ T-cells whereas CD83KO tumors had a large population of immunosuppressive CD8+ T-cells. ELISAs of media from tumor cell lines revealed that CD83OE tumor cells secrete higher levels of the T cell activating cytokine, IL-2 than controls and CD83KO. scRNA-seq of pB-IUE tumors confirmed that CD83OE have increased activating cytokines compared to CD83KO and control tumors, and that CD83KO tumors had greater expression of immunosuppressive T-regulatory profiles. Intriguingly, we found that despite equal proliferative capacity of tumor cells both in vitro and in vivo conditions, CD83OE tumors were smaller, suggesting that CD83 expression by tumor cells stabilizes CD8+ T-cells to promote immune clearance of tumors. Collectively, our data suggests that enhancing tumor cell expression of antigen presenting markers such as CD83 may encourage immune-mediated clearance of GBM.
IMMU-13. DEVELOPMENT OF ADAPTIVE IMMUNE RESISTANCE IN A MURINE GLIOMA MODEL TREATED WITH DENDRITIC CELL VACCINATION AND PD-1 CHECKPOINT BLOCKADE
Authors: Herrera Gilbert , Sun Lu , Sammarco Alessandro , Kennewick Kelly , Bensinger Steven , Prins Robert
Published: November 2023

Immunotherapies such as immune checkpoint inhibitors and active vaccination have shown great potential in unleashing antitumor immunity for cancer treatment. However, their effectiveness in treating glioblastoma (GBM) is limited. In a preclinical glioma model, administration of both autologous tumor lysate-pulsed dendritic cell vaccination (ATL-DC) and anti-PD-1 checkpoint blockade (aPD1) significantly increased survival and enhanced intratumoral T cell activation. We hypothesize that the combination of these two treatments will substantially increase the abundance and activity of tumor-reactive cytotoxic T cells. As such, we recently started a phase I trial administering ATL-DC and neoadjuvant aPD1 to recurrent GBM patients (NCT ID: NCT04201873). To understand the local antitumor immune response in greater depth, we performed single-cell RNA sequencing analysis of the CD45+ immune compartment of explanted gliomas from twelve mice, four of which were treated with ATL-DC and aPD1 while the other eight received no treatment. We found that the combination therapy increased tumor-infiltrating T cells, monocytes and DCs. We also observed the expansion and differentiation of CD8+ effector T cells under the effect of combination therapy. These T cells exhibited a differentiation trajectory from a Tcf7+Il2ra+ early activated phenotype to a terminally exhausted state marked by high expression of Pdcd1, Tox and Tigit. Interestingly, combination therapy specifically increased a macrophage subset that overexpressed Ch25h, an interferon-stimulated gene encoding for the oxysterol lipid 25-hydroxycholesterol (25-HC). Preliminary results from in vitro studies demonstrated that 25-HC restricted T cell proliferation and tumor cell cytolysis, suggesting its immunosuppressive function. In summary, our study reveals the impact of ATL-DC + aPD1 combination therapy on the immune microenvironment of GBM and a potential maladaptive mechanism mediated by 25-HC. Future studies will seek to exploit these targets therapeutically to develop more effective GBM treatment regimens.
IMMU-23. FRUCTOSE METABOLISM IN MICROGLIA PROMOTES GLIOBLASTOMA GROWTH
Authors: Billingham Leah , Wang Si , Zilinger Kaylee , Chia TzuYi , Katz Joshua , Cervantes Gustavo Ignacio Vazquez , Wan Hanxiou , Boland Lauren , Hou David , Lee-Chang Catalina , Miska Jason
Published: November 2023

Glioblastoma (GBM) is the most common brain malignancy in adults and has a dismal prognosis. Advances in standard-of-care treatments for GBM have not kept pace with those for other malignancies, in part due to the inefficacy of immunotherapies in treating GBM. The tumor microenvironment (TME) of GBM is heavily populated with pro-tumorigenic tumor-associated macrophages (TAMs) and lacks robust infiltration of T cells. Given that the number of TAMs in the TME correlates with poor prognosis, understanding the mechanisms by which they thrive is essential for discovering new therapies. Bulk RNASeq data from mouse tumors indicates that the fructose transporter, SLC2A5, is highly expressed on TAMs relative to peripheral myeloid cells. Furthermore, human glioblastoma single cell RNASeq (scRNASeq) data indicates that SLC2A5 is expressed specifically on microglia, the tissue resident macrophage of the brain. To assess the necessity of SLC2A5 in microglia, we orthotopically implanted CT2A or QPP4 glioblastoma cells into wild-type mice and mice lacking SLC2A5 (SLC2A5 KO mice). We observed a significant increase in median survival in SLC2A5 KO mice compared to wild-type mice. This indicates a necessity of fructose metabolism in microglia to promote tumorigenesis. Upon ex vivo analysis of the immune compartment of the TME, we observed that microglial cells from tumors in SLC2A5 KO mice have higher expression of MHC-II and PDL1 molecules on the cell surface compared to those from wild-type mice. Additionally, the CD4:CD8 T cell ratio in tumors from SLC2A5 KO mice was lower than that in tumors from wild-type mice. These data suggest that fructose metabolism in microglia facilitates an immunosuppressive phenotype that promotes GBM progression.
IMMU-24. SALVAGE IMMUNOTHERAPIES FOR REPLICATION REPAIR DEFICIENT (RRD) HIGH-GRADE GLIOMA FAILING ANTI-PD1 MONOTHERAPY: A REPORT FROM THE INTERNATIONAL RRD CONSORTIUM
Authors: Das Anirban , Fernandez Nicholas , Levine Adrian , Bianchi Vanessa , Stengs Lucie , Edwards Melissa , Nobre Liana , Tsang Derek , Ertl-Wagner Birgit , Morgenstern Daniel , Shlien Adam , Hawkins Cynthia , Bouffet Eric , Tabori Uri , Pugh Trevor
Published: November 2023

BACKGROUND

Initial response to immune checkpoint inhibition (ICI) for DNA replication-repair deficient high-grade glioma (RRD-HGG) is encouraging. However, clinical/biologic implications of immune-directed approaches after failing ICI-monotherapy remain unknown.

METHODS

We performed an international study of patients managed using central review/treatment recommendations (2015-2021). Salvage after anti-PD1 failure included re-irradiation where feasible, and addition of anti-CTLA4 (ipilimumab), or a MEK-inhibitor (MEKi). Outcomes included radiological response (iRANO), toxicity, second progression-free (PFS2) and overall survival (OS2). Companion biomarkers were performed centrally.

RESULTS

Twenty among 75 patients treated on anti-PD1 monotherapy are progression-free at a median follow-up of 44.6-months. For 55 patients with relapsed/progressive tumors, continuation of ICI (n=38) resulted in median OS2 of 11.6-months (51% alive) versus 1.2-months when ICI was discontinued (n=17; no survivors, p< 0.001). Addition of ipilimumab (n=24) resulted in response/stable disease in 75% with median OS2 of 12.1-months. High autoimmune toxicities (54%) were observed, particularly in constitutional mismatch-repair deficiency patients. The addition of MEKi led to response in 3/5 patients with prolonged survival. The addition of re-irradiation improved median OS2, especially in tumors with lower mutation burden (p=0.002), and those who received ipilimumab (median OS2=33-months). Several biological insights were gained. Increased CTLA4 expression explained responses to ipilimumab. Re-irradiation responses were attributed to the absence of radio-resistant indel signature (ID8). Early radiological ‘flare’ was observed in 33% on combined immunotherapy and re-radiation. MEKi responses were associated with reinvigoration of peripheral immune response. Finally, delayed, sustained responses were observed in ultra-hypermutant RRD-HGG exhibiting changes in somatic mutational spectra.

CONCLUSION

These data suggest that the continuous mutagenesis renders hypermutant RRD-HGG susceptible to checkpoint inhibitors beyond initial progression. The combination with re-irradiation and additional immune/targeted agents can maximize survival in these children and young adults. Future research should focus on biology-driven rational immunotherapy combinations that also result in lower toxicity to maximize patient benefit.
IMMU-25. ANALYSIS OF IMMUNOSUPPRESSIVE MYELOID CELLS IN THE GLIOBLASTOMA TUMOR MICROENVIRONMENT REVEALS THERAPEUTICALLY TARGETABLE IMMUNOMODULATORY SIGNALS ACROSS POPULATIONS
Authors: Asad Mohammad , Inocencio Julio , Crisman Celina , Himes Benjamin
Published: November 2023

Immunosuppression in glioblastoma (GBM) remains a critical and poorly understood barrier to the development of effective novel therapies. Increasing evidence points to the critical role of immunosuppressive myeloid cells in the immunosuppressive tumor microenvironment and an intriguing target for ameliorating tumor-mediated immune suppression. Efforts to characterize the myeloid milieu in the tumor microenvironment have revealed a highly heterogenous population of cells with the capacity to exert immunosuppressive effects. In order to maximize the efficacy of potential therapeutic targets, we sought to identify immune checkpoint markers expressed across a range of immunomodulatory myeloid cell populations in the tumor microenvironment of patients undergoing resection for GBM. Freshly collected ultrasonic aspirate obtained during the primary surgery for GBM resection (based on preoperative imaging and intraoperative frozen section, later confirmed on final pathology) was prepared for high dimensional flow cytometry to quantify the immune checkpoint marker expression profile of a number of described immunosuppressive myeloid cell populations, including both monocytic and granulocytic myeloid-derived suppressor cells (mMDSC and gMDSC), and CD16+ non-classical monocytes (NCM). mMDSCs expressed particularly high levels of TIGIT (53.9±19.27%), which was also highly expressed in the NCM population (25.03±5.44%). NCMs also demonstrated high levels of B7H3 expression (39.85±18.05%), which has recently been implicated as an important immune checkpoint protein in GBM. gMDSCs demonstrated a rather different expression profile, with significantly higher levels of VISTA expression than other immunomodulatory markers (p< 0.05). These findings underscore the diversity of immunomodulatory signaling in the tumor-associated myeloid cell compartment, emphasizing the challenges in developing single-target immune checkpoint inhibitor therapy in GBM. Nevertheless, this data points to some common patterns of expression across major immunomodulatory cell populations that remain understudied in GBM and could herald more promising avenues of immunotherapy development.
IMMU-28. TREM2 INHIBITION REPROGRAMS MYELOID CELLS TO STIMULATE ANTI-TUMOR IMMUNITY THROUGH BOTH DIRECT AND INDIRECT MECHANISMS
Authors: Sun Rui , Han Rowland , McCornack Colin , Tabor G Travis , Hou Jinchao , Cleary Ryan , Mao Diane , Liu Qin , Schoch Kathleen , Luo Jingqin , Petti Allegra , Miller Timothy , Ulrich Jason , Holtzman David , Kim Albert
Published: November 2023

The prevailing view is that myeloid cells—macrophages and microglia—in the tumor microenvironment (TME) are immunosuppressive and promote glioblastoma (GBM) progression. However, myeloid cells have the functional plasticity to restrict or support tumor cell growth. TREM2 plays important roles in brain microglial function in neurodegenerative diseases, but the functional role of TREM2 in the GBM TME and whether TREM2 represents a meaningful therapeutic target remain largely unknown. To address these questions, we investigated the immune and tumor cell consequences of TREM2 inhibition by multiple orthogonal approaches—transgenic mice, antisense oligonucleotides, and blocking antibodies—in immunocompetent preclinical models (SB28, NPA C54B) and human GBM samples through bulk and single cell RNA-sequencing, flow cytometry, biochemistry, and functional assays. We found TREM2 is highly expressed in myeloid subsets, including macrophages and microglia in human and mouse GBM tumors, and that high TREM2 expression correlates with poor prognosis in GBM patients. TREM2 loss of function in human macrophages and mouse myeloid cells increased IFNγ-induced immunoactivation and proinflammatory polarization. Conditioned media from TREM2 deficient human macrophages directly killed patient-derived GBM tumor cells, and biochemical analysis identified TNF and other putative tumoricidal proteins in this conditioned media. In mouse GBM models, mice with chronic and acute Trem2 loss of function demonstrated increased tumor cell death and increased animal survival. Trem2 inhibition reprogrammed myeloid cell phenotypes and increased PD-1+CD8+ T cells in the TME. Remarkably, Trem2 deficiency enhanced the effectiveness of anti-PD-1 treatment in vivo. Trem2 inhibition suppresses tumor cell growth through direct and indirect immune cell mechanisms--by reshaping myeloid subset and T cell functions. Thus, Trem2 inhibitory strategies, in combination with immune checkpoint blockade, may represent an attractive new approach for GBM therapy.
IMMU-34. SYSTEMIC IMMUNE SUPPRESSION IN GLIOBLASTOMA IS TARGETED BY CONCURRENT VEGF AND PD-1 INHIBITION IN A DOSE-DEPENDENT MANNER: TRANSCRIPTOMIC FINDINGS THROUGH CITE-SEQ FROM A RANDOMIZED CONTROLLED TRIAL
Authors: Ozair Ahmad , Alban Tyler , Grabowski Matthew , Otvos Balint , Bayik Defne , Bamashmos Anas , Rayman Pat , Diaz Marcella , Khosla Atulya , Bellur Shreyas , McDermott Michael , Reardon David , Wen Patrick , Mohammadi Alireza , Peereboom David , Lathia Justin , Ahluwalia Manmeet
Published: November 2023

INTRODUCTION

Anti-PD1 blockade has had poor efficacy in recurrent glioblastoma (rGBM) across three RCTs. VEGF, a proangiogenic factor that is upregulated in rGBM, contributes to tumor-associated immunosuppression and is widely targeted through bevacizumab. Preclinical data indicate a potential dose-dependent effect of anti-VEGF therapy on immunomodulation. Hence, a combination of anti-PD-1 and anti-VEGF agents is a promising approach for rGBM, for which an RCT was conducted. This work sought to utilize a multimodal approach capturing single-cell gene and protein expression by ‘cellular indexing of transcriptomes and epitopes by sequencing’ (CITE-Seq) to interrogate the systemic immunological changes in response to concurrent VEG and PD-1 inhibition.

METHODS

Patients with rGBM were administered nivolumab (240mg IV q2weeks) plus either standard-dose bevacizumab (10mg/kg) or low-dose bevacizumab (3mg/kg) IV q2weeks, with 1:1 randomization. Stratification factors were age, performance status, extent of resection, and MGMT methylation status. Primary endpoint was overall survival (OS) at 12 months. CITE-Seq was performed on 16 patients across trial arms, both pre- and on-therapy, yielding total 32 immunological profiles. For control, CITE-seq was done on three patients receiving anti-VEGF therapy alone.

RESULTS

90 patients were enrolled with median age of 60.6 years and 45 patients per arm. Both arms had similar OS at 12 months (P=0.14). Significantly higher OS was found in posthoc analysis for patients aged ≥60 years with standard dose. Distinct immune cell populations were identified, and differential changes in myeloid-derived suppressor cells (MDSCs) found across trial arms on-therapy. Network medicine approach identified VEGF as target to reduce MDSCs, with VEGF primarily expressed by responders’ MDSCs. Differential gene expression analysis identified increased pro-inflammatory signatures in standard-dose arm.

CONCLUSIONS

Standard dose bevacizumab was associated with increased inflammatory response and reduction of immunosuppressive MDSC. These mechanistic insights potentially explain survival benefit seen with concurrent VEGF and PD-1 inhibition in elderly rGBM patients.
IMMU-38. INTRATUMORAL CORRELATION OF MULTIPLEX IMMUNOFLUORESCENCE AND89ZR-CREFMIRLIMAB BERDOXAM IMMUNOPET IN RECURRENT GBM PATIENTS TREATED WITH NEOADJUVANT ANTI-PD-1 +/- ANTI-CTLA-4 THERAPY
Authors: Markus Lauren , Sun Lu , Hugo Willy , Van den Abbeele Annick D , Wen Patrick , Prins Robert
Published: November 2023

Glioblastoma (GBM) is a highly aggressive brain tumor that responds poorly to checkpoint blockade inhibitors (ICIs), such as anti-PD-1. We previously reported that neoadjuvant anti-PD-1 therapy activated and recruited T cells into recurrent GBM (rGBM) tumors, but also increased immune checkpoint interactions between T cells and myeloid cells. To overcome this resistance mechanism, we are currently conducting a phase 1B clinical trial of neoadjuvant anti-PD-1 (Nivolumab, BMS) +/- anti-CTLA-4 (Ipilimumab, BMS) combination therapy for rGBM patients (NCT04606316). To evaluate the systemic and local tumor microenvironment effects of these checkpoint inhibitors, we used immuno-positron emission tomography (CD8 immunoPET, 89Zr-crefmirlimab berdoxam, ImaginAb) to track CD8+ T cells in five rGBM patients before and after neoadjuvant anti-PD-1 or combination therapy with anti-CTLA-4, and used multiplex immunofluorescence (mIF) to analyze the intratumoral immune profile of patient-matched tumors. We found that CD8 ImmunoPET imaging could detect physiologic tracer uptake in the lymph node basins and tumor bed prior to and following checkpoint blockade, suggesting a systemic immunometabolic response within the tumor after therapy. Correlation with mIF found that combination therapy (n=1) increased the density of conventional type 1 and 2 dendritic cells (cDC1: CD3-CD141+XCR1+ and cDC2: CD3-CD1c+) in the tumors, especially cDC1, compared to anti-PD-1 monotherapy (n=4) or untreated patients (n=3) (the densities of cDC1 and cDC2 cells were 163 cells/mm2 and 13.3 cells/mm2 respectively). Moreover, combination ICI therapy was associated with enhanced infiltration of CD8+ and CD4+ T cells in the tumor (28.7 cells/mm2 and 73.8 cells/mm2, respectively) with a specific increase in CD4+ T cells compared to anti-PD-1 monotherapy. In summary, preliminary results of the correlation of the longitudinal brain immunoPET imaging with the intratumoral mIF analysis in these five rGBM patients suggests distinct effects of monotherapy vs. combination neoadjuvant anti-PD-1 and anti-CTLA-4 therapy on the intratumoral immunometabolic profile of rGBM patients.
IMMU-42. PP2A-INHIBITION INDUCES STING-TYPE I-MEDIATED IMMUNOLOGIC CELL DEATH IN GBM
Authors: Mondal Isha , Das Oishika , Lu Rongze Olivia , Ho Winson
Published: November 2023

Glioblastoma (GBM) is one of the most lethal forms of brain cancer, and is known to be an aggressive, immunologically cold tumor, resulting in a lack of T-cell infiltration and killing. Thus increasing immune-mediated killing of GBM is a promising therapeutic method. Our group has found that Protein Phosphatase 2A (PP2A), a ubiquitous serine/threonine phosphatase that has been shown to enhance tumor immunogenicity in glioblastoma, does so by inducing immunogenic cell death. We used LB-100, a small molecule inhibitor of the catalytic subunit of PP2A, as a promising drug-therapy. CRISPR-KO of PP2A was generated in murine glioma lines GL261 and SB28. Markers of immunologic cell death, such as calreticulin, gamma-H2AX, and HMGB1 were assessed. In vitro, western blotting of SB28 and GL261 showed significantly increased expression of gamma-H2AX in PP2A-KO compared to WT. Flow-cytometry staining of SB28 and GL261 revealed a dramatic increase in calreticulin expression in PP2A-KO compared to WT. An antibody-based fluorescence assay for HMGB1 also showed dramatic increase in PP2A-KO compared to WT. All experiments were repeated by treating LB-100 for 24 hour to SB28 and GL261 WT and PP2A-KO cells, and revealed a dose-dependent increase in expression of immunogenic cell death markers. In vivo, B6 mice were injected intracranially with SB28 WT or PP2A-deficient tumor and monitored till endpoint. At the endpoint, tumors were harvested, cryosectioned, and stained for calreticulin and gamma-H2AX. Mice injected with PP2A-KO tumor survived longer than WT, and had the highest expression of both calreticulin gamma-H2AX when compared to WT tissue. In conclusion, PP2A-deficiency and inhibition via LB-100 is demonstrated to induce immunogenic cell death in tumors, thus being a promising target for immunotherapy.