bluuebunny/crossref_metadata_2025_split huggingface dataset:
TMET-20. TARGETING LINKS BETWEEN METHIONINE METABOLISM AND DNA REPAIR TO IMPROVE GBM THERAPY
Authors: Korimerla Navyateja , Wilder-Romans Kari , Xu Jie , Haq Isra , Kalev Peter , Qi Nathan , Evans Charles , Kachman Maureen , Zhou Weihua , Scott Andrew J , Kothari Ayesha , Lin Angelica , O'Brien Alexandra , Palavalasa Sravya , Peterson Erik , Hyer Marc L , Marjon Katya , Lyssiotis Costas , Sleger Taryn , Wahl Daniel 
Published: November 2023

Abstract
Glioblastoma (GBM) is uniformly lethal due to intrinsic resistance to standard of care radiation (RT) and chemotherapy. Recent studies have identified altered cellular metabolism as a key mediator of GBM RT resistance. Methionine uptake is drastically elevated in GBMs compared to normal cells but whether this impacts treatment resistance is uncertain, as is the metabolic fates of methionine once it enters GBM cells. Here, we find that RT acutely increases the levels of methionine-related metabolites in a variety of RT-resistant GBM models. Stable isotope tracing studies further revealed that RT acutely activates methionine to S-adenosyl methionine (SAM) conversion through an active signaling event through DNA damage response. We developed in vivo 13C5 methionine stable isotope tracing techniques to confirm these findings in orthotopic models of GBM. Pharmacological and dietary strategies to block methionine to SAM conversion slowed the DNA damage repair and increased cell death following RT. These effects are selective to GBMs lacking the methionine salvage enzyme methylthioadenosine phosphorylase (MTAP). Pharmacologic and dietary strategies to inhibit SAM synthesis hindered tumor growth in flank and orthotopic in vivo GBM models when combined with RT. In short, these results highlight a new signaling link between DNA damage and SAM synthesis and define the metabolic fates of methionine in GBM in vivo. Inhibiting the RT-induced SAM synthesis slows the DNA damage repair and augments RT efficacy in GBM. This therapeutic strategy provides scope for combining MAT2A inhibitors with RT in GBMs with impaired methionine salvage and spares the adjacent normal brain.
TMIC-01. PERICYTES ORCHESTRATE A TUMOR-SUPPRESSIVE MICROENVIRONMENT BY IMPINGING ON THE CROSSTALK BETWEEN MACROPHAGES AND TUMOR-INITIATING CELLS IN GLIOBLASTOMA MULTIFORME
Authors: Braun Sebastian , Oudenaarden Clara , Bolivar Paulina , Sjölund Jonas , Cordero Eugenia , Rosberg Rebecca , Johansson Elinn , Pietras Alexander , Pietras Kristian 
Published: November 2023

Abstract
Glioblastoma multiforme (GBM) is characterized by fast progression, infiltrative growth pattern and a high rate of relapse. A defining feature of GBM is the existence of spatially and functionally distinct cellular niches, i.e. a hypoxic niche, a leading-edge niche, and a peri-vascular niche, in which malignant cells engage in paracrine crosstalk with cell types comprising the tumor microenvironment, including immune cells, astrocytes, and vascular cells. Here, by analysis of single-cell transcriptomic data of human GBM and transgenic mouse models of GBM, we unexpectedly identified pericytes intimately associated with the endothelium as the most active paracrine signaling hub within the tumor parenchyma. Exclusive signaling axes emanating from pericytes were received by endothelial cells, malignant cells, astrocytes, and immune cells. Depletion of pericytes through genetic engineering in several different transgenic and orthotopic mouse models of GBM demonstrated accelerated tumor progression, a disrupted blood-brain-barrier, and premature death of pericyte-poor mice. Mechanistic studies revealed that pericyte deficiency altered the cellular composition of GBM, remodeled the endothelium, and impacted on the immune cell landscape. Specifically, endothelial cells deprived of pericyte association upregulated Colony Stimulating Factor (CSF)-1, which in turn attracted peri-vascular tumor-associated macrophages polarized towards an immune-suppressive phenotype. In the absence of pericytes, the recruited macrophages expressed Hepatocyte Growth Factor (HGF), which reinforced activation of its receptor tyrosine kinase c-Met on a subset of GBM cells harboring an extreme mesenchymal-like state. Indeed, orthotopic implantation of isolated c-Met-expressing GBM cells corroborated their superior tumor-initiating capability and invasive phenotype, compared to cells negative for c-Met. Taken together, we infer that the pericyte represents a critical modulator of GBM development by orchestrating a tumor-suppressive microenvironment; our findings thus highlight the importance of pericyte preservation in the face of current and future GBM therapies.
TMIC-07. MUTANT IDH-MEDIATED SUPPRESSION OF THE TH17 LINEAGE IN GLIOMA; BIOLOGIC IMPACT AND THERAPEUTIC POTENTIAL
Authors: Reynolds Nathan , Soedel Ashleigh , Miller Emily , Ashley David , Waitkus Matthew , He Yiping , Pirozzi Christopher 
Published: November 2023

Abstract
Great excitement has surrounded the identification of tumor-specific hotspot mutations in IDH1 as they are the first therapeutic targets of low grade gliomas that have been identified in the last several decades. With a low number of viable therapeutic targets, mutations in IDH1 represent new hope in treating these tumors that are invariably recurrent and confer a dismal prognosis in their aggressive forms. Additionally, mutations in IDH1 are tumor-specific suggesting their effective targeting can reduce the collateral damage to the normal brain imparted by standard therapies. Furthermore, mutations in IDH1 lead to the overproduction of D-2-hydroxyglutarate (D-2HG), which mediates many of mutant IDH1’s effects. To gain an understanding of mutant IDH-mediated tumorigenesis, we generated genetically faithful mouse models that harbor the pathognomonic signature including the IDH1-R132H mutation and p53 deletion. This model generates tumors that overproduce D-2HG, are histologically diffuse, and confer a prolonged survival compared to their wildtype counterparts. Additionally, these models display the proneural subtype and are enriched for an oligodendrocyte precursor cell gene expression signature, both of which are typified by IDH mutations in human glioma. Exploring the impact of the IDH mutation on the tumor microenvironment, we identified several diminished immune cell subsets among the mutant IDH murine tumors, including NK cells, monocytes, and M2 macrophages. Further analysis showed a reduced Th17 gene expression profile that was corroborated through in vitro studies. The biological impact of Th17 cells appears to be cancer-context dependent with only a few studies being performed in gliomas. With the potential for Th17-mediated anti-tumor activity, as observed in cases of melanoma, the prospect for elucidating a new therapeutic avenue is exciting. As such, the biological significance of D-2HG-mediated Th17 suppression, the underlying mechanism, as well as the therapeutic potential of Th17 restoration are actively being investigated.
TMIC-19. TARGETING TUMOR-MYELOID CELL SYMBIOSIS IN GLIOBLASTOMA
Authors: Chen Peiwen 
Published: November 2023

Abstract
Heterotypic interactions across diverse cell types of the tumor microenvironment can enable tumor progression and offer points for potential therapeutic intervention. Employing glioblastoma (GBM), a lethal form of brain tumor in adults, as a model system, we sought to (i) understand the nature of specific oncogenic signals in glioma cells that affects myeloid cell biology; (ii) identify myeloid cell factors which may support glioma growth and survival, (iii) develop novel therapeutic strategies targeting the tumor-myeloid cell symbiosis; and (iv) investigate whether blockade of this symbiosis can overcome the primary resistance of immunotherapy. Specifically, the novel oncogenic signals (e.g., CLOCK and TFPI2) and myeloid cell components of microglia and myeloid-derived suppressor cells will be discussed and highlighted. The findings from our studies demonstrate that the newly identified context-dependent tumor-myeloid cell symbiotic interactions not only promote tumor progression but also induce immune checkpoint inhibitor (ICI) therapy resistance in GBM. Thus, our studies provide novel therapeutic targets and offer a great potential to overcome immunotherapy resistance in GBM.
TMIC-36. SPATIAL ARCHITECTURE OF HIGH-GRADE GLIOMA REVEALS TUMOR HETEROGENEITY WITHIN DISTINCT DOMAINS
Authors: Moffet Joel , Fatunla Oluwaseun , Whittle James , Jordan Jones , Roberts-Thomson Samuel , Pavenko Anna , Scoville David , Zhang Liang , Liang Yan , Morokoff Andrew , Freytag Saskia , Best Sarah 
Published: November 2023

Abstract
High-grade gliomas are aggressive primary brain cancers with poor response to standard regimens, driven by immense heterogeneity. In isocitrate dehydrogenase (IDH) wild-type high-grade glioma (glioblastoma, GBM), increased intra-tumoral heterogeneity is associated with more aggressive disease. Recently, spatial technologies have emerged to dissect this complex heterogeneity within the tumor ecosystem by preserving cellular organization in situ. Here, we construct a high-resolution molecular landscape of GBM and IDH-mutant high-grade glioma patient samples to investigate the cellular subtypes and spatial communities that compose high-grade glioma using digital spatial profiling and spatial molecular imaging. This uncovered striking diversity of the tumor and immune microenvironment, that is embodied by the heterogeneity of the inferred copy-number alterations in the tumor. Reconstructing the tumor architecture revealed two distinct niches, one composed of tumor cell states that most closely resemble normal glial cells, associated with microglia; and the other niche populated by monocytes and mesenchymal tumor cells. We further reveal that communication between tumor and immune cells is underpinned by tumor-specific ligands, such as TGFb signaling in astrocyte-like tumor cells. This primary study reveals high levels of intra-tumoral heterogeneity in high-grade gliomas, associated with a diverse immune landscape within spatially localized regions.
TMIC-54. RADIOTHERAPY-INDUCED REMODELING OF THE GLIOBLASTOMA MICROENVIRONMENT
Authors: Rosberg Rebecca , Johansson Elinn , Ceberg Crister , Pietras Alexander 
Published: November 2023

Abstract
Radiotherapy (RT) is included in the standard of care for glioblastoma (GBM), and while primary tumors generally respond to RT, GBMs invariably recur as incurable lesions. We have previously demonstrated that RT generates a net tumor-supportive tumor microenvironment (TME), in part by inducing remodeling of the extracellular matrix, suggesting that there are therapeutic opportunities in targeting the altered TME of recurrent GBM. Here, we have used highly multiplexed immunohistochemistry in combination with single cell RNA sequencing to characterize the cellular composition and molecular alterations to the GBM TME as tumors progress from primary to irradiated to recurrent tumors, using a genetically engineered GBM mouse model. RT resulted in a phenotypic shift suggestive of a proneural-to-mesenchymal switch of lineage-traced tumor cells immediately after treatment, but proportions of tumor cell phenotypes were largely restored at the time of recurrence. Recurrent tumors displayed an altered immune landscape, as demonstrated e.g. by an increase in the proportion of CD8+ lymphocytes coupled to a decrease in the proportion of CD4+ cells. Together, our data suggest that RT remodels the GBM TME as well as alters the phenotype of bona fide glioma cells. Ongoing studies are aimed at understanding heterotypic cell-cell interactions unique to the irradiated and recurrent GBM TME.
TMIC-64. CHARACTERIZATION OF THE TUMOR MICROENVIRONMENT IN DIFFUSE MIDLINE GLIOMAS (DMG) FOR 3D IN VITRO MODEL BUILDING
Authors: Kremer Sarah , John Rhea , Jin Peng , Michelhaugh Sharon , Cunningham Jessica , Howerton Samantha , Eze Augustine , Nazarian Javad , Munson Jennifer 
Published: November 2023

Abstract

BACKGROUND
Diffuse midline glioma (DMG) is an aggressive pediatric brain cancer. Few comprehensive tumor characterization studies have been conducted due to the relative scarcity of tissue samples. However, it is well known that the surrounding microenvironment, and particularly the cells of the normal brain, influence tumor outcomes. Here, we investigate the cell type distribution among patient autopsy samples, comparing the primary tumor, metastatic tumors, and normal brain tissue.

METHODS
Patient samples (n=10) were obtained at Children’s National through a postmortem autopsy program. All patients were diagnosed with DMG between the ages of four and thirteen. Brain sections were embedded in paraffin, sectioned into 5 μm thick slices, and stained using fluorescent immunohistochemistry. Targets included astrocytes (ALDH1L1), microglia (IBA1), neurons (NeuN), blood vessels (CD31), and tumor cells (H3K27M). Images were captured using the VS200 whole slide scanner. Automatic cell detection was conducted using QuPath, and statistical analysis was performed in GraphPad Prism.

RESULTS
From initial primary tumor IHC analysis, microglia appear to be present in slightly higher ratios than astrocytes (0.203 vs. 0.148, fraction of total cells, p=0.062). Furthermore, neurons appear in lower numbers compared to microglia and astrocytes (0.036 vs. 0.203 and 0.148, fraction of total cells, p&lt; 0.0001). There are relatively few blood vessels when adjusted for total area (0.084% of total area). In addition, within a single patient, we anticipate fewer microglia and astrocytes in normal tissue and metastatic tissue compared to the primary site. We also anticipate more neurons in normal tissue and metastatic tissue compared to the primary site.

FUTURE DIRECTIONS
Using this tumor composition data, we plan to create a 3D gel in vitro cell culture model of DMG. In collaboration with individuals at Children’s National and Columbia, we will use this model in conjunction with focused ultrasound and drug testing.
TMIC-65. PP2A/STRN4 NEGATIVELY REGULATES STING-TYPE I IFN SIGNALING IN GLIOMA ASSOCIATED MACROPHAGES THROUGH YAP/TAZ
Authors: Ho Winson , Mondal Isha , Xu Beisi , Das Oishika , Lu Rongze Olivia 
Published: November 2023

Abstract
Glioma associated Macrophages/microglia (GAMs) are the predominant immune cells in the tumor microenvironment and drive immunosuppression. Strategies depleting GAMs have not demonstrated efficacy in clinical trials for GBM. It is critical to identify the underlying mechanisms how GAMs mediate immunosuppression. STING agonist, which activates the Type I IFN signaling in myeloid cells, is a promising strategy but also have shown limited efficacy in clinical trials. Here, we report that protein phosphatase 2A (PP2A), with its specific B regulatory subunit Striatin 4 (STRN4), negatively regulated STING-Type I IFN in GAMs. Mice with macrophage PP2A deficiency exhibited improved glioma survival with radiation, which is known to activate STING. The glioma microenvironment showed decreased immunosuppressive and increased IFN-activated macrophages and CD8+ T cells. Mechanistically, we demonstrated that Hippo kinase MST1/2 was required for STING activation in macrophages. STING agonists induced dissociation of PP2A from MST1/2 in normal macrophages, but not in glioma conditioned macrophages. Furthermore, our data showed that STRN4 mediated PP2A binding to and dephosphorylation of Hippo kinase MST1/2, resulting in stabilization of YAP/TAZ to antagonize STING activation. We are also the first to demonstrate that in human GBM patients, YAP/TAZ signature was highly expressed in GAMs but not in non tumor macrophages. We also demonstrated that PP2A/STRN4 deficiency in macrophages reduced YAP/TAZ expression and sensitized glioma -conditioned macrophages to STING stimulation. In summary, we demonstrated that PP2A/STRN4- YAP/TAZ has, in our opinion, been an unappreciated mechanism that mediates immunosuppression in glioma-associated macrophages, and targeting the PP2A/STRN4-YAP/TAZ axis can sensitize glioma to immunotherapy.
TMIC-72. INVESTIGATING THE ROLES OF PGE2 IN MODULATING THE GBM-GAM MICROENVIRONMENT
Authors: Chen Pin-Yuan , Chuang Jian-Ying , Wu An-Chih , Yang Wen-Bin , Chang Wen-Chang , Lin Ai-Yun 
Published: November 2023

Abstract
Glioblastoma (GBM), the most aggressive and deadliest primary brain tumor, is characterized by being surrounded by up to approximately 40% macrophages, which promote tumor progression through interactions with tumor cells. The mechanisms underlying how GBM and its associated macrophages (GAM) communicate remain not fully understood. In this study, we investigated the essential roles of Prostaglandin E2 (PGE2), which affects multiple functions of immune cells, in modulating the GBM microenvironment, specifically the GAM. Massive PGE2 accumulated in the GBM-GAM co-culture microenvironment, and the expression of prostaglandin-endoperoxide synthase 2 (PTGS2) involved in PGE2 synthesis was markedly elevated in GAM. GAM expressed two PGE2 receptors, namely EP2 and EP4, and their expressions positively correlated with PTGS2 expression. Ingenuity pathway analysis (IPA) of differentially expressed (DE) genes obtained from GBM- (conditioned medium) CM-treated THP-1 macrophages revealed significant enrichment in biological functions associated with migration and proliferation. THP-1 macrophage migration promoted by GBM-CM was interrupted by blocking EP4 receptors using an antagonist. GBM-CM promoted THP-1 macrophages proliferation and increased proliferative enhancers, such as PI3KCD, AKT3, ETS1, and BHLHE41, while decreasing proliferative repressors, including MAF, MAFB, and CDKN1A. Cytokine array analysis indicated that GBM-CM shaped GAM into an immunosuppressive phenotype and elevated IL-6 secretion to promote GBM growth. In conclusion, our current results suggest that PGE2 accumulates in the GBM microenvironment, sustaining the macrophage population through increased recruitment and elevated local proliferation and shaping macrophages into an immunosuppressive type. Blockage of the PGE2 autocrine regulation, thus interrupting the supportive roles of GAM in GBM progression, may provide a novel therapeutic strategy for treating patients with GBM.
TMIC-79. LIPOCALIN-2 MEDIATES CELL-INTRINSIC FUNCTIONS IN GLIOBLASTOMA
Authors: Wang Sabrina , Silver Daniel , Deleyrolle Loic , Lathia Justin 
Published: November 2023

Abstract
Glioblastoma (GBM) is the most common primary brain tumor with a median survival of 17-20 months. Despite therapeutic treatments including surgery, radiation, chemotherapy, a population of GBM cells, termed cancer stem cells (CSCs) are radio-resistant and chemo-resistant, leading to mortality of the patient. CSCs also have altered metabolic profiles and have an enhanced capacity to scavenge nutrients from their microenvironment, including iron. Lipocalin-2 (LCN2) functions to sequester iron and is traditionally considered an inflammatory marker through its function of limiting iron for bacterial usage; it has also been described to have both a pro and anti-tumorigenic and has context-dependent functions depending on iron status. LCN2 has been shown to be important in brain metastasis, but its role in GBM is still largely unknown. To assess a cell-intrinsic function for LNC2, we added recombinant LCN2 to low LCN2-secreting mouse GBM cell models and observed that proliferation also increased. When we knocked down LCN2 in our higher LCN2 secreting cell lines, we observed that knockdown cells had decreased viability and growth, which was not mediated by apoptosis, but rather, ferroptosis. When these cells were subsequently engrafted into wild-type mice, we observed an increase in survival. This effect was also phenocopied when the cells were implanted into LCN2 knockout mice, suggesting the tumor-intrinsic effect overpowered the global knockout model. Lastly, to investigate how LCN2 plays a role in the GBM microenvironment, we orthotopically implanted syngeneic mouse GBM cells into male and female LCN2 knockout and wild-type mice. We observed no survival difference, further suggesting that LCN2 does not function in an extrinsic manner. Taken together, these data suggest that LCN2 affects proliferation and tumorigenesis, and is another avenue to understanding the complexity of GBM biology. Strategies to reduce LCN2 in GBM may provide a therapeutic target for GBM in the future.
MODL-08. A COMPENDIUM OF SYNGENEIC, TRANSPLANTABLE PEDIATRIC HIGH-GRADE GLIOMA MODELS REVEALS SUBTYPE-SPECIFIC THERAPEUTIC VULNERABILITIES
Authors: McNicholas Michael , De Cola Antonella , Bashardanesh Zahedeh , Foss Amelia , Lloyd Cameron , Hebert Steven , Faury Damien , Andrade Augusto Faria , Jabado Nada , Kleinman Claudia , Pathania Manav 
Published: November 2023

Abstract
Pediatric high-grade gliomas (pHGGs) are lethal, incurable brain tumors frequently driven by clonal mutations in histone genes. They often harbor a range of additional genetic alterations that correlate with different ages, anatomical locations, and tumor subtypes. We developed models representing 16 pHGG subtypes driven by different combinations of alterations targeted to specific brain regions. Tumors developed with varying latencies and cell lines derived from these models engrafted in syngeneic, immunocompetent mice with high penetrance. Targeted drug screening revealed unexpected selective vulnerabilities— H3.3G34R/PDGFRAC235Y to FGFR inhibition, H3.3K27M/PDGFRAWT to PDGFRA inhibition, and H3.3K27M/PDGFRAWT and H3.3K27M/PPM1DDC/PIK3CAE545K to combined inhibition of MEK and PIK3CA. Moreover, H3.3K27M tumors with PIK3CA, NF1 and FGFR1 mutations were more invasive and harbored distinct additional phenotypes, such as exophytic spread, cranial nerve invasion and spinal dissemination. Collectively, these models reveal that different partner alterations produce distinct effects on pHGG cellular composition, latency, invasiveness, and treatment sensitivity.
MODL-12. REGULATION OF OLIGODENDROGLIAL PROGENITOR CELL (OPC) CELL FATE IN DIFFUSE MIDLINE GLIOMA (DMG) BY THE HOMEOBOX TRANSCRIPTION FACTOR DLX2
Authors: Furst Liam , Roussel Enola , Leung Ryan , George Ankita , Firestein Ron , Faux Maree , Eisenstat David 
Published: November 2023

Abstract
Diffuse midline glioma, K27-altered (DMG) is a treatment resistant, uniformly fatal cancer that arises predominantly in children. 80% of patients with DMG harbor K27M mutations in canonical histone variants H3.3 and H3.1, leading to global epigenetic dysregulation and an oligodendroglial progenitor cell (OPC) transcriptional profile. DLX2 is a homeobox transcription factor that directly represses OPC cell fate and promotes a GABAergic interneuron cell fate during neurogenesis. Our lab has previously identified DLX2 transcription factor occupancy of genes required for OPC differentiation in vivo (Olig2, Nkx2.2, Myt1, Plp1), and shown that co-expression of DLX2 to target sequences reduced reporter gene expression in vitro. Likewise, increased expression of Olig2, Nkx2.2, and Plp-1 are observed in a Dlx1/Dlx2 double knockout (DKO) mouse model. Transient overexpression of a Dlx2-GFP construct into cells of a genetically engineered mouse model (GEMM) of DMG resulted in increased expression of Gad1/2 isoforms and decreased Olig2 and Nkx2.2, global restoration of H3K27me3, and a reduction in migration, invasion, and colony formation in vitro. Inverse expression of DLX2 and OLIG1/2 was observed in a bulk RNAseq database of 45 human DMG cell lines. We have established a pipeline to evaluate cell fate changes following changes in DLX2 expression levels. OLIG1/2high/DLX2low DMG expressing cell lines underwent stable transfection of a DLX2-mCherry overexpression construct. Successful alteration of DLX2 expression was confirmed by qPCR and immunoblot in knockout and overexpressing human DMG cell lines. Analysis of histone marks (H3K27me3, H3K27ac), K27M, and OPC signature genes will be presented with comparison of altered OPC genes from the DKO mouse as determined by RNA-seq. The manipulation of DLX2 expression in human DMG cells in vitro and in vivo provides a model system for assessing the contribution of a homeobox transcription factor required for neurogenesis to cell fate regulation and effects on tumorigenicity in DMG.