Aggressive Primary Brain Cancer Research Articles

Glioblastoma microenvironment-from biology to therapy.

Glioblastoma (GBM) is the most aggressive primary brain cancer. These tumors exhibit high intertumoral and intratumoral heterogeneity in neoplastic and nonneoplastic compartments, low lymphocyte infiltration, and high abundance of myeloid subsets that together create a highly protumorigenic immunosuppressive microenvironment. Moreover, heterogeneous GBM cells infiltrate adjacent brain tissue, remodeling the neural microenvironment to foster tumor electrochemical coupling with neurons and metabolic coupling with nonneoplastic astrocytes, thereby driving growth. Here, we review heterogeneity in the GBM microenvironment and its role in low-to-high-grade glioma transition, concluding with a discussion of the challenges of therapeutically targeting the tumor microenvironment and outlining future research opportunities.

Speeding up Glioblastoma Cancer Research: Highlighting the Zebrafish Xenograft Model

Glioblastoma multiforme (GBM) is a very aggressive and lethal primary brain cancer in adults. The multifaceted nature of GBM pathogenesis, rising from complex interactions between cells and the tumor microenvironment (TME), has posed great treatment challenges. Despite significant scientific efforts, the prognosis for GBM remains very poor, even after intensive treatment with surgery, radiation, and chemotherapy. Efficient GBM management still requires the invention of innovative treatment strategies. There is a strong necessity to complete cancer in vitro studies and in vivo studies to properly evaluate the mechanisms of tumor progression within the complex TME. In recent years, the animal models used to study GBM tumors have evolved, achieving highly invasive GBM models able to provide key information on the molecular mechanisms of GBM onset. At present, the most commonly used animal models in GBM research are represented by mammalian models, such as mouse and canine ones. However, the latter present several limitations, such as high cost and time-consuming management, making them inappropriate for large-scale anticancer drug evaluation. In recent years, the zebrafish (Danio rerio) model has emerged as a valuable tool for studying GBM. It has shown great promise in preclinical studies due to numerous advantages, such as its small size, its ability to generate a large cohort of genetically identical offspring, and its rapid development, permitting more time- and cost-effective management and high-throughput drug screening when compared to mammalian models. Moreover, due to its transparent nature in early developmental stages and genetic and anatomical similarities with humans, it allows for translatable brain cancer research and related genetic screening and drug discovery. For this reason, the aim of the present review is to highlight the potential of relevant transgenic and xenograft zebrafish models and to compare them to the traditionally used animal models in GBM research.

Cellular diversity through space and time: adding new dimensions to GBM therapeutic development.

The current median survival for glioblastoma (GBM) patients is only about 16 months, with many patients succumbing to the disease in just a matter of months, making it the most common and aggressive primary brain cancer in adults. This poor outcome is, in part, due to the lack of new treatment options with only one FDA-approved treatment in the last decade. Advances in sequencing techniques and transcriptomic analyses have revealed a vast degree of heterogeneity in GBM, from inter-patient diversity to intra-tumoral cellular variability. These cutting-edge approaches are providing new molecular insights highlighting a critical role for the tumor microenvironment (TME) as a driver of cellular plasticity and phenotypic heterogeneity. With this expanded molecular toolbox, the influence of TME factors, including endogenous (e.g., oxygen and nutrient availability and interactions with non-malignant cells) and iatrogenically induced (e.g., post-therapeutic intervention) stimuli, on tumor cell states can be explored to a greater depth. There exists a critical need for interrogating the temporal and spatial aspects of patient tumors at a high, cell-level resolution to identify therapeutically targetable states, interactions and mechanisms. In this review, we discuss advancements in our understanding of spatiotemporal diversity in GBM with an emphasis on the influence of hypoxia and immune cell interactions on tumor cell heterogeneity. Additionally, we describe specific high-resolution spatially resolved methodologies and their potential to expand the impact of pre-clinical GBM studies. Finally, we highlight clinical attempts at targeting hypoxia- and immune-related mechanisms of malignancy and the potential therapeutic opportunities afforded by single-cell and spatial exploration of GBM patient specimens.

Immunogenic cell death mediated TLR3/4-activated MSCs in U87 GBM cell line

Background and aimsGlioblastoma (GBM) is an aggressive primary brain cancer with no promising curative therapies. It has been indicated that MSCs can interact with the tumour microenvironment (TME) through the secretion of soluble mediators regulating intercellular signalling within the TME. TLRs are a multigene family of pattern recognition receptors with evolutionarily conserved regions and are widely expressed in immune and other body cells. MSCs by TLRs can recognize conserved molecular components (DAPMPs and PAPMPs) and activate signalling pathways, which regulate immune and inflammatory responses. MSCs may exert immunomodulatory functions through interaction with their expressed toll-like receptors (TLRs) and exert a protective effect against tumour antigens. As an emerging approach, we aimed to monitor the U87 cell line growth, migration and death markers following specific TLR3/4-primed-MSCs-CMs treatment. Methods and resultsWe investigated the phenotypic and functional outcomes of primed-CMs and glioma cell line co-culture following short-term, low-dose TLR3/4 priming. The gene expression profile of target genes, including apoptotic markers and related genes, was analyzed by qRT-PCR. MicroRNA-Seq examined the miRNA expression patterns, and flow cytometry evaluated the cell viability and cycle stages. The results showed significant changes in apoptosis and likely necroptosis-related markers following TLR3/4-primed-MSCs-CMs exposure in the glioma cell line. Notably, we observed a considerable induction of selective pro-apoptotic markers and both the early and late stages of apoptosis in treated U87 cell lines. Additionally, the migration rate of glioma cells significantly decreased following MSCs-CM treatment. ConclusionOur findings confirmed that the exposure of TLR3/4-activated-MSCs-CMs with glioma tumour cells possibly changes the immunogenicity of the tumour microenvironment and induces immunogenic programmed cell death. Our results can support the idea that TLR3/4-primed-MSCs can lead to innate immune-mediated cell death and modify tumour cell biology in invasive and metastatic cancers.

Abstract 2881: Comparing the effects of proton and photon therapy on promoting cancer aggressiveness in ovarian cancer and glioblastoma

Abstract Ovarian cancer is the 12th most common cancer among women in the United States and the 5th leading cause of cancer-related death for women. About 80% of the patients are diagnosed at stages III or IV, classified as High-Grade Serous Ovarian Cancer (HGSOC). HGSOC is highly aggressive, exhibiting an 80% recurrence rate within 24 months after cancer treatment. Brain and nervous system cancer ranks as the 10th leading cause of cancer-related death in the U.S., with Glioblastoma Multiforme (GBM) accounting for 47.7% of all brain cancer cases. GBM is the most aggressive primary brain cancer, with a 90% recurrence rate and a 4% 2-year survival rate. Patients with these cancers encounter limited treatment options, and the recurrence of cancer exacerbates these challenges. Therefore, a deeper understanding of the factors contributing to cancer treatment-induced aggressiveness is greatly needed. In our study, we first examined the treatment efficacy of proton and photon radiation by conducting apoptosis assays. Our findings demonstrate that proton radiation is significantly more effective at eliminating both HGSOC and GBM cells compared to photon radiation. Subsequently, we assessed the level of cancer aggressiveness in the surviving cells after radiation exposure by measuring stemness and epithelial-mesenchymal transition (EMT) levels. While proton radiation proved to be more effective in eliminating a greater number of cancer cells, we hypothesize that both proton and photon irradiation promote cancer aggressiveness in the surviving cells of HGSOC and GBM. To assess the stemness and EMT level of cancer cells following radiation, we integrated a SORE6-GFP reporter to identify the cancer stem cell population expressing SOX2/OCT4 and a 3’ UTR-ZEB1-GFP reporter to detect the cell population with mesenchymal traits. Cells transduced with the reporters were treated with 0, 1, 2, 4, and 8 Gy of 250 MeV proton and 6 MeV photon beams, and at 72 hours post-radiation, GFP levels were measured via flow cytometry. Our data demonstrated a dose-dependent increase in stemness and EMT levels in live cells after both types of radiation. Furthermore, cancer cells exposed to radiation were harvested at 72 hours and 240 hours post-radiation for RT-qPCR analysis. Our preliminary data indicate an upregulation of stemness genes including POU5F1 and SOX2, as well as EMT transcription factor genes ZEB1, SNAI1, and TWIST1 in response to both types of radiation in most cell lines. These findings indicate that both proton and photon radiation therapies promote cancer aggressiveness in the surviving cancer cells. Citation Format: Yeonkyu Jung, Ann Morcos, Aaron Keniston, Ashley Antonissen, Sharon Asariah, Antonella Bertucci, Marcelo Vazquez, Juli Unternaehrer. Comparing the effects of proton and photon therapy on promoting cancer aggressiveness in ovarian cancer and glioblastoma [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 2881.

Abstract 1257: CHD5 suppresses glioblastoma by inhibiting MYC

Abstract Fundamentally, cancer is a disease caused by genetic and epigenetic alterations that converge to reprogram gene expression networks, leading to unrestrained proliferation. Glioblastoma (GBM) is the most prevalent and aggressive primary brain cancer, median survival being approximately one year and the 5-year survival rate being only 5%. Despite decades of effort, this devastating picture has not appreciably improved and effective therapies have been elusive for GBM patients. A better understanding of GBM biology is essential for developing more effective therapies. Although several genetic alterations have been implicated in gliomagenesis, driving genetic factors responsible for GBM are still obscure, and the interplay between genetic alterations and epigenetic dysregulation is largely undocumented during the gliomagenic process. Here, we show that CHD5 — a gene mapping to the 1p36 chromosomal region that is notoriously deleted in many cancers, is recurrently deleted in over 20% of GBM cases and is further downregulated through epigenetic means. To delineate how CHD5 loss promotes gliomagenesis, we established a glioma-prone mouse model harboring conditional alleles of Pten, Trp53, and Chd5. We developed an engineered mouse neural stem cell (NSCs)-based strategy to elicit glioma formation, as NSCs are the major cell-of-origin for GBM. We show that Chd5 loss significantly impairs NSCs differentiation while promoting proliferation, transformation, and gliomagenesis in vivo. Mechanistically, Chd5 forms a Chd3-containing but Chd4-independent NuRD complex that directly binds the Myc promoter and super enhancers to govern Myc expression in normal NSCs, with the Snf2 domain of Chd5 playing the most critical chromatin regulating role in the context of GBM. Chd5 loss triggers the remodeling of chromatin, enhances accessibility, and augments Myc expression, leading to the formation of highly aggressive glioma. Furthermore, reactivating CHD5 in human GBM xenograft models significantly extends survival. This work demonstrates the tumor suppressive role of CHD5 in gliomagenesis, providing therapeutic insights for cancers with 1p36 deletions. In parallel, this work presents a powerful strategy for rapidly interrogating gene function during gliomagenesis using engineering NSCs, and the generation of novel mouse models with classic clinical features of GBM, offering new approaches for elucidating GBM biology that can inform on therapeutic opportunities for treating patients with GBM. Citation Format: Xueqin Sherine Sun, Alea Mills. CHD5 suppresses glioblastoma by inhibiting MYC [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 1257.

Abstract B014: CHD5 suppresses glioblastoma by inhibiting MYC

Abstract Fundamentally, cancer is a disease caused by genetic and epigenetic alterations that converge to reprogram gene expression networks, leading to unrestrained proliferation. Glioblastoma (GBM) is the most prevalent and aggressive primary brain cancer, median survival being approximately one year and the 5-year survival rate being only 5%. Despite decades of effort, this devastating picture has not appreciably improved and effective therapies have been elusive for GBM patients. A better understanding of GBM biology is essential for developing more effective therapies. Although several genetic alterations have been implicated in gliomagenesis, driving genetic factors responsible for GBM are still obscure, and the interplay between genetic alterations and epigenetic dysregulation is largely undocumented during the gliomagenic process. Here, we show that CHD5 — a gene mapping to the 1p36 chromosomal region that is notoriously deleted in many cancers, is recurrently deleted in over 20% of GBM cases and is further downregulated through epigenetic means. To delineate how CHD5 loss promotes gliomagenesis, we established a glioma-prone mouse model harboring conditional alleles of Pten, Trp53, and Chd5. We developed an engineered mouse neural stem cell (NSCs)-based strategy to elicit glioma formation, as NSCs are the major cell-of-origin for GBM. We show that Chd5 loss significantly impairs NSCs differentiation while promoting proliferation, transformation, and gliomagenesis in vivo. Mechanistically, Chd5 forms a Chd3-containing but Chd4-independent NuRD complex that directly binds the Myc promoter and super enhancers to govern Myc expression in normal NSCs, with the Snf2 domain of Chd5 playing the most critical chromatin regulating role in the context of GBM. Chd5 loss triggers the remodeling of chromatin, enhances accessibility, and augments Myc expression, leading to the formation of highly aggressive glioma. Furthermore, reactivating CHD5 in human GBM xenograft models significantly extends survival. This work demonstrates the tumor suppressive role of CHD5 in gliomagenesis, providing therapeutic insights for cancers with 1p36 deletions. In parallel, this work presents a powerful strategy for rapidly interrogating gene function during gliomagenesis using engineering NSCs and highlights the generation of novel mouse models with classic clinical features of GBM, offering new approaches for elucidating GBM biology that can inform on therapeutic opportunities for treating patients with GBM. Citation Format: Xueqin Sherine Sun, Alea Mills. CHD5 suppresses glioblastoma by inhibiting MYC [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr B014.

Global stability and parameter analysis reinforce therapeutic targets of PD-L1-PD-1 and MDSCs for glioblastoma

Glioblastoma (GBM) is an aggressive primary brain cancer that currently has minimally effective treatments. Like other cancers, immunosuppression by the PD-L1-PD-1 immune checkpoint complex is a prominent axis by which glioma cells evade the immune system. Myeloid-derived suppressor cells (MDSCs), which are recruited to the glioma microenviroment, also contribute to the immunosuppressed GBM microenvironment by suppressing T cell functions. In this paper, we propose a GBM-specific tumor-immune ordinary differential equations model of glioma cells, T cells, and MDSCs to provide theoretical insights into the interactions between these cells. Equilibrium and stability analysis indicates that there are unique tumorous and tumor-free equilibria which are locally stable under certain conditions. Further, the tumor-free equilibrium is globally stable when T cell activation and the tumor kill rate by T cells overcome tumor growth, T cell inhibition by PD-L1-PD-1 and MDSCs, and the T cell death rate. Bifurcation analysis suggests that a treatment plan that includes surgical resection and therapeutics targeting immune suppression caused by the PD-L1-PD1 complex and MDSCs results in the system tending to the tumor-free equilibrium. Using a set of preclinical experimental data, we implement the approximate Bayesian computation (ABC) rejection method to construct probability density distributions that estimate model parameters. These distributions inform an appropriate search curve for global sensitivity analysis using the extended fourier amplitude sensitivity test. Sensitivity results combined with the ABC method suggest that parameter interaction is occurring between the drivers of tumor burden, which are the tumor growth rate and carrying capacity as well as the tumor kill rate by T cells, and the two modeled forms of immunosuppression, PD-L1-PD-1 immune checkpoint and MDSC suppression of T cells. Thus, treatment with an immune checkpoint inhibitor in combination with a therapeutic targeting the inhibitory mechanisms of MDSCs should be explored.

NIMG-43. A 57-YEAR-OLD MALE WITH PRIMARY GLIOBLASTOMA TREATED WITH LASER INTERSTITIAL THERMAL THERAPY: IMAGING AND AUTOPSY FINDINGS

Abstract INTRODUCTION: Glioblastoma (GBM) is an aggressive primary brain cancer with significant resistance to the current therapeutic approach of chemotherapy and radiotherapy, jointly known as chemoradiation (CRT). Magnetic hyperthermia therapy (MHT) is a promising therapy for GBM that can be used to perform multiple sessions of non-invasive, localized hyperthermia by activating locally delivered magnetic iron oxide nanoparticles (MIONPs) with an external alternating magnetic field (AMF). In this study, MHT-mediated enhancement of CRT was evaluated in murine and human glioma cell lines both in cell culture and in rodents.

TMIC-36. SPATIAL ARCHITECTURE OF HIGH-GRADE GLIOMA REVEALS TUMOR HETEROGENEITY WITHIN DISTINCT DOMAINS

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.

BIOM-20. NEAT1 EXPRESSION IS ASSOCIATED WITH GLIOBLASTOMA PATIENT RESPONSE TO IMMUNE CHECKPOINT INHIBITORS

Abstract Glioblastoma (GBM) is the most common and aggressive primary brain cancer. Despite advances in therapeutic intervention, including maximal tumor resection, chemotherapy, and radiotherapy, GBM patient median survival remains approximately 20.9 months. A promising approach to overcome current therapeutic challenges is the use of inhibitors of immune checkpoints, such as PD-1/PD-L1, which have been demonstrated to be effective against many different solid cancers. Despite the strong interest in applying these strategies to GBM, clinical studies evaluating the efficacy of monoclonal antibodies against PD-1/PD-L1 have yielded disappointing results. However, an analysis of the data from these studies, considering clinical factors such as MGMT promoter methylation and the use of steroids, indicated that immune checkpoint inhibitor (ICI) therapy may benefit a subset of GBM patients. Moreover, additional clinical studies in GBM have demonstrated the importance of the timing of ICI treatment, although the markers associated with response remain unclear. Therefore, understanding the molecular basis of clinical response to PD-1/PD-L1 inhibitors is critical to identify GBM patients who can benefit from this type of therapy. By analyzing the transcriptomic profile of two different cohorts of GBM patients, we identify NEAT1 as a long noncoding RNA upregulated in GBM patients with longer survival upon anti-PD-1/PD-L1 treatment. Higher expression of NEAT1 was associated with upregulation of the interferon-gamma pathway and downregulation of cell-cycle-related genes. Single-cell RNA-sequencing analysis showed that higher NEAT1 expression in tumor cells correlated with the number of infiltrating macrophages and microglia. Among the GBM immune infiltrates, we found that macrophages and microglia had the highest NEAT1 median expression. Macrophage expression of NEAT1 was associated with enrichment in the TNF-alpha signaling pathway and the regulation of different inflammatory cytokines. Our findings suggest that NEAT1 is an important factor in shaping the tumor-immune microenvironment and a potential marker to predict GBM patient response to ICI.

EXTH-79. A NOVEL ANTI-GALECTIN-3 ANTIBODY THERAPEUTIC SYNERGIZES WITH TEMOZOLOMIDE IN PRECLINICAL MODELS TO DIMINISH TUMOR GROWTH, DECREASE MIGRATION, AND PROLONG SURVIVAL

Abstract Glioblastoma (GBM) is the most aggressive, invasive, and malignant primary brain cancer whose standard of care for nearly 20 years has been surgical resection followed by radiotherapy and temozolomide (TMZ) treatment, resulting in a median survival of 15 months following diagnosis. Heterogenous tumor cell populations that evade resection and develop chemoradiation resistance highlight the need for novel therapies that can target both the migratory and proliferative nature of GBM cells. Galectin-3, a carbohydrate-binding protein overexpressed in the GBM parenchyma and stromal astrocytes, is a potent modulator of cell proliferation, migration, angiogenesis, T-cell inhibition, and M2 macrophage polarization, and is seen to increase following TMZ and radiation treatment. Heightened Galectin-3 expression levels correlate to lower survival in glioma patients, thus greatly underscoring the need for targeting Galectin-3 in conjunction with initial standard-of-care treatment. Here, we characterize the therapeutic effects of a brain-penetrant monoclonal anti-Galectin-3 antibody (Gal3 Ab) we have developed for its ability to inhibit GBM growth and migration in several in vitro assays and in vivo heterotopic and orthotopic mouse models. Our Gal3 Ab significantly decreases cell viability, neurosphere migration, and cell invasion in vitro in the presence of full length or truncated Gal3, whose expression and secretion in GBM cells is enhanced following short and long-term TMZ stimulation. We find that Galectin-3 directly binds to EGFR, amplified in ~40% of GBM patients, as well as its most commonly mutated form, EGFRvIII, and our Gal3 Ab can block these bindings, decrease EGFR activation, and alter EGFR localization. In vivo, our Gal3 Ab decreases tumor burden and improves survival in combination with temozolomide, compared to standard-of-care treatment alone in multiple cell-line models. Our pre-clinical studies highlight the potential for our novel Gal3 antibody to further improve TMZ efficacy and benefit GBM patients by diminishing tumor cell migration and slowing tumor growth.

P02.04.B TARGETING METABOLIC VULNERABILITIES IN GLIOBLASTOMA

Abstract BACKGROUND Glioblastoma is the most common and aggressive primary brain cancer, with a median survival of 16 months. A subset of cells within these tumours, termed glioblastoma stem cells (GSCs), displays high tumourigenic capacity and resistance to conventional therapies, and are responsible for tumour recurrence. Glioblastomas have been initially shown to mainly rely on glycolysis as a source of energy. However, a growing body of literature reports that GSCs are less glycolytic than their differentiated progeny and can thrive on oxidative phosphorylation (OXPHOS) to survive, sustain stemness and fuel tumourigenic potential. Thus, targeting OXPHOS could be a promising strategy to halt energy production and starve GSCs to death. However, under metabolic stress, GSCs can also switch to a more glycolytic phenotype, suggesting a metabolic plasticity in GSCs, and thus adding a layer of complexity to target GSC metabolism. In the current study, we have investigated the impact of compound X (CX), recently shown to impair mitochondrial respiration, on the fate and tumourigenesis of GSCs. MATERIAL AND METHODS Multiple patient-derived and murine GSC models were used to test the impact of CX on GSCs in vitro. The effect of CX on glioblastoma tumors was evaluated using patient-derived xenografts and syngeneic mouse models. RESULTS We have established that CX inhibits GSC proliferation and impairs stemness-related pathways in vitro. CX delays glioblastoma tumourigenesis in vivo. While a drastic decrease in cell proliferation was observed, cell death assays revealed that CX does not induce cell death. This suggests that GSCs gain a slow-cycling phenotype to resist energy depletion. Mechanistically, we have established that CX targets complex I of the mitochondrial respiratory chain, leading to an impairment of OXPHOS. Interestingly, inhibition of OXPHOS by CX was associated with an extensive production of extracellular lactate, indicating that at least, a subset of GSCs gain metabolic adaptability by co-opting glycolysis to survive. Thus, to tackle this metabolic plasticity in GSCs, we adopted a new strategy that involves sequestration of the lactic acid intracellularly via disruption of lactate transporters. Treatment of GSCs with monocarboxylate transporter inhibitors, AZD3965 and syrosingopine, alone did not significantly impact GSC growth and viability. Strikingly, combined CX treatment with either AZD3965 or syrosingopine resulted in high intracellular lactate buildup, increased reactive oxygen species, and led to drastic cell lethality in multiple GSC models. CONCLUSION This study highlights that re-routing the OXPHOS-dependent GSCs to glycolysis offers a vulnerability to sensitize GSCs to cell death. Dual inhibition of OXPHOS and lactate export could be a promising therapeutic approach to deplete malignant GSCs and suppress glioblastoma tumourigenesis.

P02.12.B UNDERSTANDING THE ROLES OF EPHRIN A5 IN GLIOBLASTOMA AND ITS POTENTIAL AS A THERAPEUTIC TARGET

Abstract BACKGROUND Glioblastoma (GBM) is the most common and aggressive malignant primary brain cancer and is associated with very poor patient outcomes. GBM has been classified into three cell subtypes (proneural (PN), classical (CL), and mesenchymal (MES)), which have been further defined into four plastic cell states (neural-progenitor-like (NPC-like), oligodendrocyte-progenitor-like (OPC-like), astrocyte-like (AC-like), and mesenchymal-like (MES-like)). Existing treatment options have had limited success in improving overall survival, with the extreme heterogeneity present in GBM presenting a major barrier to effective therapy. Thus, there is an urgent need to develop more effective therapeutic strategies which better capture heterogeneity and delay tumour relapse. Several erythropoietin-producing human hepatocellular (Eph) receptors and ephrin ligands have been shown to be functionally overexpressed in cancer and have become attractive therapeutic targets. EphA3 has previously been shown to be a functional, tumour-specific target, frequently elevated in the MES subtype. We identified ephrin A5, the high-affinity ligand of EphA3, to be frequently co-expressed with EphA3 in GBM tumours. However, unlike EphA3, the mechanisms of ephrin A5 in GBM remain understudied. We therefore believe that ephrin A5 serves as an attractive synergistic target for the treatment of GBM. MATERIAL AND METHODS We examined the expression of ephrin A5 in a panel of GBM patient specimens. A panel of GBM tumours were also selected for immunohistochemical and spatial transcriptomics analysis. For in vitro functional studies, ephrin A5 was overexpressed in several GBM primary cell lines. Assays examining proliferation, stemness and differentiation were performed. RESULTS Expression of ephrin A5 was comparable to EphA3 in GBM. 64% of GBM tumours analysed showed higher levels of ephrin A5, relative to the highest normal brain specimen. Initial immunohistochemistry analysis suggests EphA3 and ephrin A5 to be expressed discretely on over 75% of the total tumour mass. Spatial transcriptomics analysis suggests ephrin A5 to be enriched in cells of the AC-like cell state. In vitro overexpression of ephrin A5 was shown to reduce neurosphere formation and induce differentiation of GBM cells. CONCLUSION EphA3 and ephrin A5 are overexpressed in a portion of GBM tumours. Critically, there was a strong mutually exclusive expression to different compartments of the GBM tumour, covering the vast majority of the total tumour mass. Our data suggests that ephrin A5 overexpression drives a less aggressive, more differentiated AC-like tumour phenotype. Thus, dual targeting of EphA3 and ephrin A5 in GBM could provide an opportunity to better capture tumour heterogeneity and achieve more durable therapeutic responses.

SYST-14 D2C7 CAR EFFECTIVELY AND SAFELY TREATS EGFRWT AND EGFRVIII-EXPRESSING TUMORS FOLLOWING INTRACRANIAL ADMINISTRATION

Abstract Glioblastoma (GBM) is the most aggressive primary brain cancer with a median survival of less than 16 months. Therefore, significant treatment advances are of critical need. Immunotherapies, such as chimeric antigen receptor (CAR) T cells, have achieved remarkable success in eliminating hematological cancers. Unfortunately, CARs have overall failed to control solid tumors. One major reason for this failure is tumor heterogeneity, a characteristic especially true of GBM. In GBM, EGFRvIII is a commonly targeted tumor antigen; however, only a subset of tumor cells will express EGFRvIII. Thus, EGFRvIII-negative cells easily escape EGFRvIII-targeting CAR therapies. A better approach would be to target multiple antigens or an antigen that is more homogeneously expressed throughout the tumor. More commonly than EGFRvIII expression, glioma cells overexpress the wildtype isoform of EGFR (EGFRwt). Simultaneously targeting EGFRvIII and EGFRwt, instead of targeting each independently, with a CAR will theoretically expand the amount of tumor that will be eliminated by the CAR. Here, we adapted the D2C7scFv that binds both EGFRwt and EGFRvIII into a third generation CAR. D2C7 CAR potently and specifically killed EGFRwt and EGFRvIII-expressing U87 glioma, but not U87 with EGFR knocked out. In xenograft models, intracranially administered D2C7 CAR significantly prolonged survival of mice bearing orthotopic U87vIII, U87 (EGFRwt), and heterogeneous U87/U87vIII tumors compared tocontrols. Additionally, D2C7 CAR was an effective treatment in an orthotopic EGFR-expressing medulloblastoma model. Furthermore, D2C7 CAR treatment led to a significant survival benefit in mice bearing intrancranial A431, an aggressive, EGFR-expressing carcinoma line, a model of metastasis to the brain. Importantly, D2C7 CAR did not show reactivity towards normal tissue with EGFR expression, suggesting a tumor-specific epitope of EGFR is being targeted. Together, these data provide evidence that D2C7 CAR can treat EGFR/EGFRvIII heterogeneous or homogeneous primary or metastatic brain tumors with potentially little-to-no off-tumor toxicity.

The Current Landscape of Glioblastoma Biomarkers in Body Fluids.

Glioblastoma (GBM) is a highly aggressive and lethal primary brain cancer that necessitates early detection and accurate diagnosis for effective treatment and improved patient outcomes. Traditional diagnostic methods, such as imaging techniques and tissue biopsies, have limitations in providing real-time information and distinguishing treatment-related changes from tumor progression. Liquid biopsies, used to analyze biomarkers in body fluids, offer a non-invasive and dynamic approach to detecting and monitoring GBM. This article provides an overview of GBM biomarkers in body fluids, including circulating tumor cells (CTCs), cell-free DNA (cfDNA), cell-free RNA (cfRNA), microRNA (miRNA), and extracellular vesicles. It explores the clinical utility of these biomarkers for GBM detection, monitoring, and prognosis. Challenges and limitations in implementing liquid biopsy strategies in clinical practice are also discussed. The article highlights the potential of liquid biopsies as valuable tools for personalized GBM management but underscores the need for standardized protocols and further research to optimize their clinical utility.

Perivascular invasion of primary human glioblastoma cells in organotypic human brain slices: human cells migrating in human brain.

Glioblastoma (GBM) is an aggressive primary brain cancer. Lack of effective therapy is related to its highly invasive nature. GBM invasion has been studied with reductionist systems that do not fully recapitulate the cytoarchitecture of the brain. We describe a human-derived brain organotypic model to study the migratory properties of GBMIDH-wild type ex vivo. Non-tumor brain samples were obtained from patients undergoing surgery (n = 7). Organotypic brain slices were prepared, and green fluorescent protein (GFP)-labeled primary human GBM IDH-wild type cells (GBM276, GBM612, GBM965) were placed on the organotypic slice. Migration was evaluated via microscopy and immunohistochemistry. After placement, cells migrated towards blood vessels; initially migrating with limited directionality, sending processes in different directions, and increasing their speed upon contact with the vessel. Once merged, migration speed decreased and continued to decrease with time (p < 0.001). After perivascular localization, migration is limited along the blood vessels in both directions. The percentage of cells that contact blood vessels and then continue to migrate along the vessel was 92.5% (-3.9/ + 2.9)% while the percentage of cells that migrate along the blood vessel and leave was 7.5% (-2.9/ + 3.9) (95% CI, Clopper-Pearson (exact); n = 256 cells from six organotypic cultures); these percentages are significantly different from the random (50%) null hypothesis (z = 13.6; p < 10-7). Further, cells increase their speed in response to a decrease in oxygen tension from atmospheric normoxia (20% O2) to anoxia (1% O2) (p = 0.033). Human organotypic models can accurately study cell migrationex vivo. GBM IDH-wild type cells migrate toward the perivascular space in blood vessels and their migratory parameters change once they contact vascular structures and under hypoxic conditions. This model allows the evaluation of GBM invasion, considering the human brain microenvironment when cells are removed from their native niche after surgery.

O019 Studying telomere biology and genomic instability in gliomas

Abstract Introduction Glioblastoma (GBM) is the most aggressive primary brain cancer. Identifying novel markers which stratify patients and predict response to targeted therapies is a priority. Telomeres are caps on chromosome ends protecting them from aberrant DNA damage response. Telomere length (TL) alterations and fusions are key markers for genomic instability and high-resolution telomere analysis provides powerful prognostic and predictive information in several tumour types. We therefore studied telomeric profiles and fusions in GBM patients and related this to clinical outcome. Methods Tumours from 151 adults with isocitrate dehydrogenase-wildtype GBMs were analysed for TL using the precision High-Throughput Single Telomere Length Analysis technique. 67 patients underwent further multiplex long-range polymerase chain reaction to identify fusions via Southern hybridisation using telomere-adjacent 33P radioisotope-labelled probes. Telomere fusions from 10 tumours that exhibited the highest frequency of fusions were characterised with long-read Nanopore sequencing. Results GBMs display short telomeres with a median length of 4.0kb. Shorter TLs in patients with unmethylated O6-methylguanine DNA methyltransferase status (commonest current biomarker) conferred worse survival (HR 2.13, p = 0.002). 66/67 (98.5%) patients analysed revealed telomeric fusions. Nanopore sequencing validated these events, while confirming the presence of microhomology and telomeric deletion. This mutational spectrum is consistent with utilisation of specific DNA repair pathways in mediating telomere fusion. Conclusion This study provides the first mechanistic evidence of dysfunctional telomeres in adult GBMs and suggests TL analysis may provide independent prognostic information. The presence of telomere fusions indicates significant genomic instability and may favour targeted therapies for patients exhibiting this signature.

Abstract 106: Intratumoral heterogeneity of glioblastoma is attributed to precancerous cells derived from neural stem cells

Abstract Glioblastoma (GBM) is the most common and aggressive primary brain cancer in adults. We and other groups have identified mutation-harboring neural stem cells (NSCs) in the subventricular zone (SVZ) as cells-of-origin carrying driver mutations (Lee et al, Nature 2018). However, little is known about the evolutional process by which mutation-harboring NSCs in the SVZ transform into distant cancer cells with a high degree of molecular heterogeneity. Here, using a spontaneous, somatic mouse model that recapitulates human GBM arising from NSCs that carry driver mutations, we show that mutation-harboring NSCs transform into precancerous cells through oligodendrocyte progenitor cell (OPC) lineage specification during tumor evolution. These precancerous cells show dysregulated translation and/or modification of extracellular matrix (ECM) prior to tumor formation. They subsequently give rise to GBMs with intratumoral heterogeneity exhibiting multiple developmental cell states as in human GBM, and also show activation of additional transcriptional programs, including immune evasion, ECM remodeling, epithelial-mesenchymal transition, and proliferation. Importantly, we further identified precancerous cell populations carrying driver mutations, namely gain of chromosome 7 and loss of chromosome 10 in tumor-free SVZ tissues from GBM patients with intratumoral heterogeneity. These human precancerous cells indeed exhibited OPC and neural progenitor cell-like expression patterns similar to those in our spontaneous GBM mouse model. Thus, our results demonstrate that cell-type specification of precancerous cells with oncogenic transcriptional programs underlie evolution of GBM from mutation-harboring NSCs and intratumoral heterogeneity. Citation Format: Jeong Ho Lee, Hyun Jung Kim, Seok-Gu Kang. Intratumoral heterogeneity of glioblastoma is attributed to precancerous cells derived from neural stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 106.

Mechanical nanosurgery of chemoresistant glioblastoma using magnetically controlled carbon nanotubes.

Glioblastoma (GBM) is the most common and aggressive primary brain cancer. Despite multimodal treatment including surgery, radiotherapy, and chemotherapy, median patient survival has remained at ~15 months for decades. This situation demands an outside-the-box treatment approach. Using magnetic carbon nanotubes (mCNTs) and precision magnetic field control, we report a mechanical approach to treat chemoresistant GBM. We show that GBM cells internalize mCNTs, the mobilization of which by rotating magnetic field results in cell death. Spatiotemporally controlled mobilization of intratumorally delivered mCNTs suppresses GBM growth in vivo. Functionalization of mCNTs with anti-CD44 antibody, which recognizes GBM cell surface-enriched antigen CD44, increases mCNT recognition of cancer cells, prolongs mCNT enrichment within the tumor, and enhances therapeutic efficacy. Using mouse models of GBM with upfront or therapy-induced resistance to temozolomide, we show that mCNT treatment is effective in treating chemoresistant GBM. Together, we establish mCNT-based mechanical nanosurgery as a treatment option for GBM.