Glioblastoma Tumor Microenvironment Research Articles

Hypoxia coordinates the spatial landscape of myeloid cells within glioblastoma to affect survival.

Myeloid cells are highly prevalent in glioblastoma (GBM), existing in a spectrum of phenotypic and activation states. We now have limited knowledge of the tumor microenvironment (TME) determinants that influence the localization and the functions of the diverse myeloid cell populations in GBM. Here, we have utilized orthogonal imaging mass cytometry with single-cell and spatial transcriptomic approaches to identify and map the various myeloid populations in the human GBM tumor microenvironment (TME). Our results show that different myeloid populations have distinct and reproducible compartmentalization patterns in the GBM TME that is driven by tissue hypoxia, regional chemokine signaling, and varied homotypic and heterotypic cellular interactions. We subsequently identified specific tumor subregions in GBM, based on composition of identified myeloid cell populations, that were linked to patient survival. Our results provide insight into the spatial organization of myeloid cell subpopulations in GBM, and how this is predictive of clinical outcome.

Non-Tumor Cells within the Tumor Microenvironment-The "Eminence Grise" of the Glioblastoma Pathogenesis and Potential Targets for Therapy.

Glioblastoma (GBM) is the most common malignancy of the central nervous system in adults. GBM has high levels of therapy failure and its prognosis is usually dismal. The phenotypic heterogeneity of the tumor cells, dynamic complexity of non-tumor cell populations within the GBM tumor microenvironment (TME), and their bi-directional cross-talk contribute to the challenges of current therapeutic approaches. Herein, we discuss the etiology of GBM, and describe several major types of non-tumor cells within its TME, their impact on GBM pathogenesis, and molecular mechanisms of such an impact. We also discuss their value as potential therapeutic targets or prognostic biomarkers, with reference to the most recent works on this subject. We conclude that unless all "key player" populations of non-tumor cells within the TME are considered, no breakthrough in developing treatment for GBM can be achieved.

Autophagy in glioblastoma: A mechanistic perspective.

Glioblastoma (GBM) is one of the most lethal malignancies in humans. Even after surgical resection and aggressive radio- or chemotherapies, patients with GBM can survive for less than 14 months. Extreme inter-tumor and intra-tumor heterogeneity of GBM poses a challenge for resolving recalcitrant GBM pathophysiology. GBM tumor microenvironment (TME) exhibits diverse heterogeneity in cellular composition and processes contributing to tumor progression and therapeutic resistance. Autophagy is such a cellular process; that demonstrates a cell-specific and TME context-dependent role in GBM progression, leading to either the promotion or suppression of GBM progression. Autophagy can regulate GBM cell function directly via regulation of survival, migration, and invasion, or indirectly by affecting GBM TME composition such as immune cell population, tumor metabolism, and glioma stem cells. This review comprehensively investigates the role of autophagy in GBM pathophysiology.

T cell-mediated tumor killing based signature to predict the prognosis and immunotherapy for glioblastoma

Despite the significant advancements in cancer treatment brought by immune checkpoint inhibitors (ICIs), their effectiveness in treating glioblastoma (GBM) remains highly dissatisfactory. Immunotherapy relies on the fundamental concept of T cell-mediated tumor killing (TTK). Nevertheless, additional investigation is required to explore its potential in prognostic prediction and regulation of tumor microenvironment (TME) in GBM. TTK sensitivity related genes (referred to as GSTTKs) were obtained from the TISIDB. The training cohort was available from the TCGA-GBM, while the independent validation group was gathered from GEO database. Firstly, we examined differentially expressed GSTTKs (DEGs) with limma package. Afterward, the prognostic DEGs were identified and the TTK signature was established with univariate and LASSO Cox analyses. Next, we examined the correlation between the TTK signature and outcome of GBM as well as immune phenotypes of TME. Furthermore, the evaluation of TTK signature in predicting the effectiveness of immunotherapy has also been conducted. We successfully developed a TTK signature with an independent predictive value. Patients who had a high score experienced a worse prognosis compared to patients with low scores. The TTK signature showed a strong positive association with the infiltration degree of immunocyte and the presence of various immune checkpoints. Moreover, individuals with a lower score exhibited increased responsiveness to ICIs and experienced improved prognosis. In conclusions, we successfully developed and verified a TTK signature that has the ability to predict the outcome and immune characteristics of GBM. Furthermore, the TTK signature has the potential to direct the personalized immunotherapy for GBM.

Biosensor-Enhanced Organ-on-a-Chip Models for Investigating Glioblastoma Tumor Microenvironment Dynamics.

Glioblastoma, an aggressive primary brain tumor, poses a significant challenge owing to its dynamic and intricate tumor microenvironment. This review investigates the innovative integration of biosensor-enhanced organ-on-a-chip (OOC) models as a novel strategy for an in-depth exploration of glioblastoma tumor microenvironment dynamics. In recent years, the transformative approach of incorporating biosensors into OOC platforms has enabled real-time monitoring and analysis of cellular behaviors within a controlled microenvironment. Conventional in vitro and in vivo models exhibit inherent limitations in accurately replicating the complex nature of glioblastoma progression. This review addresses the existing research gap by pioneering the integration of biosensor-enhanced OOC models, providing a comprehensive platform for investigating glioblastoma tumor microenvironment dynamics. The applications of this combined approach in studying glioblastoma dynamics are critically scrutinized, emphasizing its potential to bridge the gap between simplistic models and the intricate in vivo conditions. Furthermore, the article discusses the implications of biosensor-enhanced OOC models in elucidating the dynamic features of the tumor microenvironment, encompassing cell migration, proliferation, and interactions. By furnishing real-time insights, these models significantly contribute to unraveling the complex biology of glioblastoma, thereby influencing the development of more accurate diagnostic and therapeutic strategies.

Pentraxin 3: A Main Driver of Inflammation and Immune System Dysfunction in the Tumor Microenvironment of Glioblastoma.

Brain tumors are a heterogeneous group of brain neoplasms that are highly prevalent in individuals of all ages worldwide. Within this pathological framework, the most prevalent and aggressive type of primary brain tumor is glioblastoma (GB), a subtype of glioma that falls within the IV-grade astrocytoma group. The death rate for patients with GB remains high, occurring within a few months after diagnosis, even with the gold-standard therapies now available, such as surgery, radiation, or a pharmaceutical approach with Temozolomide. For this reason, it is crucial to continue looking for cutting-edge therapeutic options to raise patients' survival chances. Pentraxin 3 (PTX3) is a multifunctional protein that has a variety of regulatory roles in inflammatory processes related to extracellular matrix (ECM). An increase in PTX3 blood levels is considered a trustworthy factor associated with the beginning of inflammation. Moreover, scientific evidence suggested that PTX3 is a sensitive and earlier inflammation-related marker compared to the short pentraxin C-reactive protein (CRP). In several tumoral subtypes, via regulating complement-dependent and macrophage-associated tumor-promoting inflammation, it has been demonstrated that PTX3 may function as a promoter of cancer metastasis, invasion, and stemness. Our review aims to deeply evaluate the function of PTX3 in the pathological context of GB, considering its pivotal biological activities and its possible role as a molecular target for future therapies.

The antitumor action of endocannabinoids in the tumor microenvironment of glioblastoma.

Approximately 80% of all malignant brain tumors are gliomas, which are primary brain tumors. The most prevalent subtype of glioma, glioblastoma multiforme (GBM), is also the most deadly. Chemotherapy, immunotherapy, surgery, and conventional pharmacotherapy are currently available therapeutic options for GBM; unfortunately, these approaches only prolong the patient's life by 5years at most. Despite numerous intensive therapeutic options, GBM is considered incurable. Accumulating preclinical data indicate that overt antitumoral effects can be induced by pharmacologically activating endocannabinoid receptors on glioma cells by modifying important intracellular signaling cascades. The complex mechanism underlying the endocannabinoid receptor-evoked antitumoral activity in experimental models of glioma may inhibit the ability of cancer cells to invade, proliferate, and exhibit stem cell-like characteristics, along with altering other aspects of the complex tumor microenvironment. The exact biological function of the endocannabinoid system in the development and spread of gliomas, however, is remains unclear and appears to rely heavily on context. Previous studies have revealed that endocannabinoid receptors are present in the tumor microenvironment, suggesting that these receptors could be novel targets for the treatment of GBM. Additionally, endocannabinoids have demonstrated anticancer effects through signaling pathways linked to the classic features of cancer. Thus, the pharmacology of endocannabinoids in the glioblastoma microenvironment is the main topic of this review, which may promote the development of future GBM therapies.

Co-expression of immune checkpoints in glioblastoma revealed by single-nucleus RNA sequencing and spatial transcriptomics

Glioblastoma (GBM) is one of the most malignant tumors of the central nervous system. The pattern of immune checkpoint expression in GBM remains largely unknown. We performed snRNA-Seq and spatial transcriptomic (ST) analyses on untreated GBM samples. 8 major cell types were found in both tumor and adjacent normal tissues, with variations in infiltration grade. Neoplastic cells_6 was identified in malignant cells with high expression of invasion and proliferator-related genes, and analyzed its interactions with microglia, MDM cells and T cells. Significant alterations in ligand-receptor interactions were observed, particularly between Neoplastic cells_6 and microglia, and found prominent expression of VISTA/VSIG3, suggesting a potential mechanism for evading immune system attacks. High expression of TIM-3, VISTA, PSGL-1 and VSIG-3 with similar expression patterns in GBM, may have potential as therapeutic targets. The prognostic value of VISTA expression was cross-validated in 180 glioma patients, and it was observed that patients with high VISTA expression had a poorer prognosis. In addition, multimodal cross analysis integrated SnRNA-seq and ST, revealing complex intracellular communication and mapping the GBM tumor microenvironment. This study reveals novel molecular characteristics of GBM, co-expression of immune checkpoints, and potential therapeutic targets, contributing to improving the understanding and treatment of GBM.

Abstract LB444: Identification of a novel and selective Transglutaminase 2 (TGM2) inhibitors modulate tumor microenvironment in Glioblastoma

Abstract Background: TGM (Transglutaminase) family enzymes are Ca2+ dependent and engaged in specific posttranslational modifications by cross-linking extracellular matrix (ECM) proteins. ECM protein complex is more stable and resistant to enzymatic degradation. These enzymes modify proteins by cross-linking epsilon-(gamma-glutamyl), lysine, or (gamma-glutamyl) polyamine bonds. TGM2 (Transglutaminase 2) is a ubiquitous enzyme, and its expression is identified in the cytoplasm, plasma membrane, and the nucleus of various cells. The membrane-bound form of TGM2 binds GTP and functions as a G protein. TGM2 regulates cell survival, proliferation, migration, and modulation through ECM organization. We explored the role of TGM2 in Glioblastoma cells and its role in modulating the tumor microenvironment, cell proliferation, and survival. In addition to TGM2's role in GBM tumors, its expression has been linked to resistance to certain therapies in glioblastoma was investigated. Targeted modulation of macrophages with TGM2 inhibitors impacts the immune response against GBM, potentially enhancing the efficacy. Understanding the intricate interplay between TGM2, and GBM-associated macrophages is a key component of the tumor microenvironment (TME) and crucial for the development of targeted TGM2 inhibitors. Materials and Methods: Human Transglutaminase 2 (hTGM2) activity of inhibitors was assayed using the fluorescent transamination assay incorporating dansylcadaverine into glutamine-donor substrate N, N-dimethyl casein, and DCC. Cellular efficacies of selected TGM2 inhibitors evaluated in U138 and U87 glioblastoma cells in CellTiter-Glo Luminescent cell viability assay. Results: We have identified a series of novel small molecule TGM2 inhibitors based on our initial lead fragment hits with an IC50s 6-29 uM from our in-house MolecuLern fragment library. Fragments2Lead (F2L) optimizations strategies, synthesis, and SAR studies provided a lead SLX-9029 and SLX-9031 inhibitors with IC50s of 1.2, 1.5 uM in inhibiting TGM2 activity in our established cell-free fluorescent transamination assay. The initial TMG2 inhibitor leads further screening for TGM2-expressed U138 and U87 glioblastoma cells demonstrating promising cellular efficacies as singles agents. Additional GBM cell profiling, combination studies along with safety secondary pharmacology, cellular toxicities, and PK results will be discussed. Conclusion: In summary, we identified promising lead TGM2 inhibitors that show activity in both cell-free and cell-based TGM2-expressed GMB cells. The TGM family members, selectivity, additional GBM cellular profiling, ADME, cellular toxicity, and in vivo PK studies are underway, and these results will be presented. Citation Format: Hariprasad Vankayalapati, Chenyu Lin, Zhaoang li, Kyle Medley, David J. Bearss. Identification of a novel and selective Transglutaminase 2 (TGM2) inhibitors modulate tumor microenvironment in Glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB444.

Resveratrol ameliorates glioblastoma inflammatory response by reducing NLRP3 inflammasome activation through inhibition of the JAK2/STAT3 pathway

ObjectivesThe aim of this study was to investigate the anti-tumor effect of resveratrol (RSV) on glioblastoma (GBM) and its specific mechanism in improving the inflammatory response of the tumor microenvironment. The tumor microenvironment of GBM is highly neuroinflammatory, inducing tumor immunosuppression. Therefore, ameliorating the inflammatory response is an important focus for anti-tumor research.MethodsThe anti-tumor effect of RSV on GBM was demonstrated through in vitro cellular assays, including CCK-8, EdU, PI staining, Transwell, wound healing assay, and flow cytometry. Potential mechanisms of RSV's anti-GBM effects were identified through network pharmacological analysis. In addition, the relationship of RSV with the JAK2/STAT3 signaling pathway and the inflammasome NLRP3 was verified using Western blot.ResultsRSV significantly inhibited cell viability in GBM cell lines LN-229 and U87-MG. Furthermore, it inhibited the proliferation and invasive migration ability of GBM cells, while promoting apoptosis. Network pharmacological analysis revealed a close association between the anti-GBM effects of RSV and the JAK/STAT signaling pathway, as well as inflammatory responses. Western blot analysis confirmed that RSV inhibited the over-activation of the inflammasome NLRP3 through the JAK2/STAT3 signaling pathway. Partial reversal of RSV's inhibition of inflammasome NLRP3 was observed with the addition of the JAK/STAT agonist RO8191.ConclusionsIn vitro, RSV can exert anti-tumor effects on GBM and improve the inflammatory response in the GBM microenvironment by inhibiting the activation of the JAK2/STAT3 signaling pathway. These findings provide new insights into potential therapeutic targets for GBM.

Real-time glioblastoma tumor microenvironment assessment by SpiderMass for improved patient management

Glioblastoma is a highly heterogeneous and infiltrative form of brain cancer associated with a poor outcome and limited therapeutic effectiveness. The extent of the surgery is related to survival. Reaching an accurate diagnosis and prognosis assessment by the time of the initial surgery is therefore paramount in the management of glioblastoma. To this end, we are studying the performance of SpiderMass, an ambient ionization mass spectrometry technology that can be used invivo without invasiveness, coupled to our recently established artificial intelligence pipeline. We demonstrate that we can both stratify isocitrate dehydrogenase (IDH)-wild-type glioblastoma patients into molecular sub-groups and achieve an accurate diagnosis with over 90% accuracy after cross-validation. Interestingly, the developed method offers the same accuracy for prognosis. In addition, we are testing the potential of an immunoscoring strategy based on SpiderMass fingerprints, showing the association between prognosis and immune cell infiltration, to predict patient outcome.

WTAP regulates the production of reactive oxygen species, promotes malignant progression, and is closely related to the tumor microenvironment in glioblastoma.

RNA modifications have been substantiated to regulate the majority of physiological activities in the organism, including the metabolism of reactive oxygen species (ROS), which plays an important role in cells. As for the effect of RNA modification genes on ROS metabolism in glioblastoma (GBM), it has not been studied yet. Therefore, this study aims to screen the RNA modification genes that are most related to ROS metabolism and explore their effects on the biological behavior of GBM in vitro. Here, an association between WTAP and ROS metabolism was identified by bioinformatics analysis, and WTAP was highly expressed in GBM tissue compared with normal brain tissue, which was confirmed by western blotting and immunohistochemical staining. When using a ROS inducer to stimulate GBM cells in the WTAP overexpression group, the ROS level increased more significantly and the expression levels of superoxide dismutase 1 (SOD1) and catalase (CAT) also increased. Next, colony formation assay, wound healing assay, and transwell assay were performed to investigate the proliferation, migration, and invasion of GBM cells. The results showed that WTAP, as an oncogene, promoted the malignant progression of GBM cells. Functional enrichment analysis predicted that WTAP was involved in the regulation of tumor/immune-related functional pathways. Western blotting was used to identify that WTAP had a regulatory effect on the phosphorylation of PI3K/Akt signaling. Finally, based on functional enrichment analysis, we further performed immune-related analysis on WTAP. In conclusion, this study analyzed WTAP from three aspects, which provided new ideas for the treatment of GBM.

Chronic hypoxia remodels the tumor microenvironment to support glioma stem cell growth

Cerebral organoids co-cultured with patient derived glioma stem cells (GLICOs) are an experimentally tractable research tool useful for investigating the role of the human brain tumor microenvironment in glioblastoma. Here we describe long-term GLICOs, a novel model in which COs are grown from embryonic stem cell cultures containing low levels of GSCs and tumor development is monitored over extended durations (ltGLICOs). Single-cell profiling of ltGLICOs revealed an unexpectedly long latency period prior to GSC expansion, and that normal organoid development was unimpaired by the presence of low numbers of GSCs. However, as organoids age they experience chronic hypoxia and oxidative stress which remodels the tumor microenvironment to promote GSC expansion. Receptor-ligand modelling identified astrocytes, which secreted various pro-tumorigenic ligands including FGF1, as the primary cell type for GSC crosstalk and single-cell multi-omic analysis revealed these astrocytes were under the control of ischemic regulatory networks. Functional validation confirmed hypoxia as a driver of pro-tumorigenic astrocytic ligand secretion and that GSC expansion was accelerated by pharmacological induction of oxidative stress. When controlled for genotype, the close association between glioma aggressiveness and patient age has very few proposed biological explanations. Our findings indicate that age-associated increases in cerebral vascular insufficiency and associated regional chronic cerebral hypoxia may contribute to this phenomenon.

Abstract 2777: A unique sub-population of PDGFRB+ glioma-associated mesenchymal stem cells constitute the perivascular niche in murine glioblastoma

Abstract Microvascular proliferation (MVP) and spatial heterogeneity are defining histological features of glioblastoma (GBM). Using ex vivo culture method to analyze human GBMs we have previously identified mesenchymal stem cell (MSC)-like cells, called glioma-associated-MSCs (GA-MSCs) in the heterogenous tumor-microenvironment (TME) of GBMs. Like pericytes, fibroblastic cells and smooth muscle cells (SMCs), these GA-MSCs reside in the perivascular niche (PVN) within GBM, and their presence correlates with MVP, decrease in immune cell counts, and poor prognosis. However, the impact of GA-MSCs on the TME remains correlative, and to date, a causative role of GA-MSCs in MVP and immune evasion has not been established in vivo. We hypothesize that recruited GA-MSCs promote MVP and enhance immune evasion in the GBM-TME. To begin to address this hypothesis, we first identified and characterized GA-MSCs at single-cell resolution in an immunocompetent murine GBM model. We sorted tumor, immune, and non-tumor-non-immune (NTNI) cells from GFP-labelled GSC005 tumors in C57Bl/6 mice and performed scRNA-seq. Tumor cells (GFP+ cells) clustered together into 13 distinct cell states. Of the immune cells (CD45+), the most abundant cell types were microglia (33.9%), macrophages (31.9%), T cells (10.3%), dendritic cells (7.5%) and B cells (1.4%), mimicking human GBM. In the NTNI compartment, we identified 17 clusters, which mapped to endothelial cells, oligodendrocytes, astrocytes and other cell types. Interestingly, there were 4 distinct cell clusters that exclusively expressed platelet-derived growth factor receptor beta (PDGFRB). Three of these clusters mapped to pericytes, SMCs and fibroblastic cells. The fourth cluster expressed both adipose tissue and bone marrow MSC markers, identifying for the first time, GA-MSCs in murine GBM. Next, to define the spatial organization of GA-MSCs and their relationship to immune cells in the GBM TME, we conducted spatial proteomics. GA-MSC counts were significantly higher in the PVN compared with the avascular niche (AN) (p= 0.009) and GA-MSCs were absent in contralateral non-tumor regions. Interestingly, GA-MSCs co-localized with SMCs, fibroblastic cells and pericytes as well as pro-tumorigenic macrophages/microglia (Iba1+/CD163+) in the PVN indicating potential interactions between these cell populations. In conclusion, we have identified for the first time, MSC-like cells in the PVN of murine GBM. Our results suggest that these GA-MSCs are recruited to the TME where they may promote MVP, a hallmark of GBM, and interact with immunosuppressive immune cells. Building on these observations, future experiments will investigate the extent to which GA-MSCs drive MVP formation and immune evasion in GBM. Citation Format: Mohammad F. Zaman, Sanjay K. Singh, Anwar Hossain, Lynette M. Phillips, Joy Gumin, Daniel Ledbetter, Bojana Milutinovic. A unique sub-population of PDGFRB+ glioma-associated mesenchymal stem cells constitute the perivascular niche in murine 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 2777.

Abstract 5372: KITENIN leads immunosuppression in the glioblastoma microenvironment via CCL20

Abstract Background: Glioblastoma (GBM) is characterized by an immunosuppressive tumor microenvironment (TME), limiting the effectiveness of existing treatments. The author investigated the role of KAI1 COOH-terminal interacting tetraspanin (KITENIN) in mediating this immunosuppression, focusing on its effect on cytokine secretion and tumor-infiltrating lymphocyte (TIL) profiles in the TME. Materials and Methods: Using cytokine array and Luminex multiplex assays, the author evaluated cytokine secretion in KITENIN-modulated GL261 cells. The author further isolated TILs from an orthotopic mouse model implanted with these cells and induced in vitro differentiation of myeloid cells. The effect of neutralizing antibody for target cytokine, was assessed in vivo, and clinical relevance was investigated using GBM patient data from our cohort and TCGA. Results: Employing cytokine array and Luminex multiplex assays, we found increased level of CC chemokine ligand 20 (CCL20) within KITENIN-overexpressed (KIT-HA) GL261 cell supernatants. Immunohistochemical analyses using GBM samples confirmed that both KITENIN and CCL20 expressions co-directionally increased and this was associated with decreased survival by TCGA analysis. Myeloid-derived suppressor cells (MDSCs), macrophages, and CD4+Foxp3+ regulatory T cells (Tregs) were observed to be higher in brain tumor implanted with KIT-HA GL261. Furthermore, KIT-HA GL261 conditioned medium expanded CD45+CD11b+Gr1-Ly6c+ monocytic MDSCs (M-MDSCs), an effect that was abrogated by CCL20 downregulation. In vivo neutralization of CCL20 resulted in reduced tumor volume, prolonged survival, and decreased M-MDSCs, thus affirming the role of CCL20 in mediating immunosuppression. Conclusion: These findings underscore the KITENIN-CCL20 axis as a promising target for alleviating the immunosuppressive TME in GBM, potentially unlocking new avenues for GBM immunotherapy. Citation Format: Eun-Jeong Ahn, Nah Ihm Kim, Sung Sun Kim, Jae-Hyuk Lee, Joon Haeng Rhee, Kyung-Keun Kim, Hangun Kim, Kyung-Hwa Lee, Kyung-Sub Moon. KITENIN leads immunosuppression in the glioblastoma microenvironment via CCL20 [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 5372.

Abstract 1325: CD19 CAR-expressing iPSC-derived NK cells effectively enhance migration and cytotoxicity into glioblastoma by targeting to the pericytes in tumor microenvironment

Abstract In cancer immunotherapy, targeting specific antigens with chimeric antigen receptors (CARs) has emerged as a potent tool for cell-based therapy. After being accessed by CARs, the selective anticancer lysis by CAR-natural killer (NK) cells through ‘missing-self’ and ‘induced-self’ mechanisms can mitigate off-tumor toxicity, a contrast to CAR-T cells. This specificity can be advantageous in the heterogeneous milieu of solid tumors. In the tumor microenvironment of glioblastoma (GBM), pericytes not only support tumor growth but also contribute to immune evasion, underscoring their potential as therapeutic targets in GBM treatment. Indeed, we examined and observed the presence of CD19-positive pericytes derived from GBM in patient samples, particularly within the perivascular niche, highlighting CD19 as a possible therapeutic target. Given this context, our study aimed to target the GBM tumor microenvironment, with a special focus on pericytes expressing CD19, to evaluate the potential effectiveness of CD19 CAR-iNK cells against GBM. In this study, we generated induced pluripotent stem cell-derived NK (iNK) cells with CD19 CAR. To determine whether CD19 CAR targets the tumor microenvironment pericytes in GBM, we developed GBM-blood vessel assembloids (GBVA) by fusing GBM spheroids with blood vessel organoids. When co-cultured with GBVA, CD19 CAR-iNK cells migrated towards the pericytes surrounding the GBM, inducing tumor lysis through NKp44 upregulation. Using a microfluidic chip, we observed that post-infused CD19 CAR-iNK cells targeted pericytes in a perfusion-like setting, facilitating an examination of CD19 CAR-driven migration and their tumor-specific cytotoxicity on the GBM. Therefore, we conclude that CD19 CAR-iNK cells may effectively target the pericytes in the GBM tumor microenvironment, suggesting their potential therapeutic value for GBM treatment. Citation Format: Dasom Kong, Daekee Kwon, Bokyung Moon, Da-Hyun Kim, Kyung-Sun Kang. CD19 CAR-expressing iPSC-derived NK cells effectively enhance migration and cytotoxicity into glioblastoma by targeting to the pericytes in tumor microenvironment [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 1325.

Abstract 1450: Novel whole slide imaging modes for imaging mass cytometry reveal cellular and structural composition of mouse glioblastoma

Abstract Mouse tumors have become widely used models in translational research of brain malignancies, helping to address the difficulties related to studying the human brain. Mouse brain can be regarded as a miniaturized model of the human brain, permitting visualization of the whole tissue to provide spatial cellular context. Imaging Mass Cytometry™ (IMC™) is a highly relevant tool capable of quantitative evaluation of the multiparametric protein composition in brain tumor microenvironment (TME) without the complications of autofluorescence, tissue degradation, and spectral overlap. The Hyperion XTi™ Imaging System (Standard BioTools™) utilizes IMC technology to simultaneously assess more than 40 individual structural and functional markers in tissue, providing insight into the organization and function of the TME. We demonstrate the whole slide imaging (WSI) application using a 40-marker panel composed of the Maxpar OnDemand™ Mouse Immuno-Oncology IMC Panel Kit and the Maxpar® Neuro Phenotyping IMC Panel Kit on mouse normal and glioblastoma (GBM) brain tissue. The panel was composed of mouse-specific antibodies, which highlight tumor and immune components of the mouse TME. We performed imaging using two new features of Hyperion™ XTi. Ultrafast preview mode (PM) was applied to rapidly screen entire brain sections for marker expression signatures associated with various immuno-oncology processes. This enabled biomarker-guided selection of areas in tumor tissue that were imaged using region of interest-based IMC and analyzed using single-cell analysis (SCA). In parallel, a high-throughput tissue mode (TM) was applied to perform a detailed whole-slide scan of normal and GBM mouse brain tissues that were quantified using pixel-based analysis (PBA) to unravel the composition of the TME. Using TM, we were able to successfully visualize the entire coronal and sagittal sections of normal mouse brain as well as mouse GBM tissue. PBA on TM data provided quantitative spatial expression patterns of structural and immune markers across the whole tissue. In normal tissue, we visualized the highly organized structure of the normal brain and detected neurons, oligodendrocytes, vascular-adjacent astrocytes, and axonal tracks. In GBM tissue, necrotic cores, areas with high immune infiltration, extracellular matrix deposits, and activated tumor cells were detected. SCA of GBM tissue demonstrated expansive vascularization, replicating Olig2+ cells, activation of Ras signaling, and high abundance of infiltrating immune cells. Overall, we demonstrate the successful application of two novel WSI modes and highlight the power of IMC technology to simultaneously explore dozens of relevant biological outputs to better understand the TME of GBM and other tumors. For research use only. Not for use in diagnostic procedures. Citation Format: Qanber Raza, Nick Zabinyakov, Thomas D. Pfister, Nikesh Parsotam, David Howell, Liang Lim, Christina Loh. Novel whole slide imaging modes for imaging mass cytometry reveal cellular and structural composition of mouse 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 1450.

Abstract 4989: Targeting IL-1β mitigates radiation induced MDSC expansion & improves survival in glioblastoma

Abstract Background: Our previous research demonstrated that radiation therapy (RT) for glioblastoma (GBM) induces aberrant myelopoiesis, increasing production of myeloid derived suppressor cells (MDSCs) and exacerbating T-cell suppression. However, the precise biological mechanisms underlying this phenomenon remain unclear. This study aims to elucidate the role of the pro-inflammatory cytokine interleukin-1beta (IL-1β) in RT-induced myelopoiesis and its correlation with poor prognosis in GBM patients. Methods: We conducted an extensive analysis of circulatory immune cells and pro-inflammatory cytokines in GBM patients treated with chemoradiotherapy. Using an orthotopic mouse model of GBM, we investigated the impact of IL-1β on myelopoiesis and survival. Functional assays were employed to examine MDSC expansion. Multi-color flow cytometry was used for immune profiling. Results: We found that RT elevated the plasma IL-1β concentration in both GBM patients and GBM-bearing mice, which also corresponded with an increase of MDSC in blood. In the murine GBM model, RT appeared to promote hematopoietic stem (HSPC) differentiation towards myelopoiesis. This led to increased MDSC precursor cells in the bone marrow, elevated circulating MDSCs in blood, and more infiltration of MDSCs in the tumor microenvironment (TME). Similar effects were observed in GBM-bearing mice following the administration of exogenous IL-1β. In contrast, inhibition of IL-1β using anti-IL-1β antibody during RT led to reduced myelopoiesis. When anti-IL-1β antibody was combined with functional inhibition of MDSCs using phosphodiesterase-5 inhibitor-tadalafil during RT, we observed decreased MDSC infiltration and increased CD8+ T cell infiltration in the TME. The combination approach also extended the survival of GBM-bearing mice after RT longer than either drug alone. Conclusions: Irradiation of GBM appears to induce IL-1β to promote aberrant myelopoiesis and MDSC expansion. A multi-pronged approach to inhibit MDSC production using IL-1β inhibitor and MDSC function using tadalafil during RT may be a promising approach to overcome the immune-suppressive TME of GBM. Citation Format: Subhajit Ghosh, Jiayi Huang, David DeNardo, Dennis Hallahan, Jerry Jaboin, Dinesh Thotala. Targeting IL-1β mitigates radiation induced MDSC expansion & improves survival in 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 4989.

Abstract 1161: Deep spatial proteomics: A new approach for obtaining insight into the glioblastoma microenvironment

Abstract Glioblastoma is the most frequent and malignant brain tumor, with a median survival of approximately 14 months. The tumor microenvironment is composed of different cell types and is known to support the glioblastoma cells and contribute to poor patient prognosis. Since accumulating studies report discordance between mRNA and protein abundances both on population and single-cell levels, and since proteins are the effector molecules of the cells and the actual target molecules of most drugs, our aim is to dissect the tumor microenvironment by spatial LC-MS based proteomics. Glioblastoma formalin-fixed paraffin-embedded (FFPE) tissue was sectioned and placed on membrane glass slides suitable for laser capture microdissection (LCM), followed by precise isolation of single cells from the heterogeneous tumor microenvironment. We used the Zeiss Palm MicroBeam laser microdissection instrument, combined with an Orbitrap Eclipse Tribrid Mass Spectrometer running our in-house sensitivity tailored Data Independent Acquisition method (WISH-DIA) to analyze and quantify the proteomes. We obtained up to 3000 proteins out of only 100 cells and were able to demonstrate the feasibility of collecting and analyzing various cell types at the single-cell level. The proteins identified belonged to many different classes/families of proteins and were able to distinguish the different cell types. In conclusion, this on-going study demonstrates our ability to isolate single cells from the highly heterogeneous tumor microenvironment of glioblastoma with ultra-high sensitivity, thereby allowing the characterization of the proteome of the glioblastoma microenvironment followed by identification of potential therapeutic and/or diagnostic targets. Citation Format: Kartikey Saxena, Rune Daucke, Vilde Pedersen, Pia Helene Klausen, Erwin Schoof, Bjarne Winther Kristensen. Deep spatial proteomics: A new approach for obtaining insight into the glioblastoma microenvironment [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 1161.

Abstract 6770: Acquired temozolomide resistance instructs patterns of glioblastoma cell motility and proteome expression within gelatin hydrogels

Abstract Acquired drug resistance in glioblastoma (GBM) presents a major clinical challenge and is one of the key factors contributing to the abysmal prognosis with less than 15 months median overall survival. The aggressive chemotherapy with the frontline therapeutic, temozolomide (TMZ), ultimately fails to kill residual, highly invasive tumor cells after surgical resection and radiotherapy. Here, we present a robust three-dimensional (3D) in vitro hydrogel model of acquired temozolomide (TMZ) resistance using isogenically-matched glioblastoma (GBM) cell lines. We demonstrate distinct drug response patterns between TMZ-sensitive and TMZ-resistant GBM cells, emphasizing our model's promise for future pre-clinical investigations aimed at developing novel therapies targeting drug-resistant GBM. Importantly, our model detects apoptosis-related protein changes in response to TMZ, validating its ability to study drug-induced molecular changes. Furthermore, our study delves into the migratory potential of GBM cells within the 3D extracellular matrix environment. Additionally, we uncover significant alterations in cytokine expression associated with matrix remodeling and angiogenesis, providing new avenues for therapeutic investigation. Although our findings are derived from a specific set of isogenically-matched cell lines, this model highlights the potential to explore personalized treatment strategies. Ongoing research in our lab is dedicated to gaining a more profound understanding of matrix remodeling and the migratory potential of TMZ-resistant GBM cells. Moreover, our future work will aim to expand our study to include a wider range of cell lines and patient-derived xenografts within our advanced microphysiological systems that include key elements of GBM tumor microenvironment such as perivascular niche. This endeavor seeks to establish connections between observed therapeutic behaviors and clinical outcomes, ultimately contributing to the development of more effective treatments for GBM patients. Citation Format: Viktoriia Kriuchkovskaia, Ela Eames, Rebecca Riggins, Brendan Harley. Acquired temozolomide resistance instructs patterns of glioblastoma cell motility and proteome expression within gelatin hydrogels [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 6770.