bluuebunny/crossref_metadata_2025 huggingface dataset:
TMIC-59. IL-2 SECRETING ENGINEERED MYELOID CELLS POTENTIATE CYTOTOXIC EFFECTOR CELL ACTIVATION TO DELAY MALIGNANT PROGRESSION IN A PRECLINICAL MODEL OF GLIOMA
Authors: Canella Alessandro , Nazzaro Matthew , Haffey Abigail , Schmitt Claire , Behbehani Gregory , Rajappa Prajwal
Published: November 2023

INTRODUCTION

Gliomas are the most prevalent brain tumor in the adolescent and young adult population (AYA) and one of the leading causes of cancer-related death. In fact, two-thirds of glioma AYA patients are affected by low-grade gliomas (LGGs). Moreover, there are no therapies to prevent glioma LGG malignant progression. Malignant progression is associated with a significant reduction of tumor infiltrating cytotoxic effector immune cells, primarily due to the immunosuppressive tumor microenvironment (TME) mediated by regulatory T lymphocytes, tumor associated macrophages (TAMs), and myeloid-derived suppressor cells (MDSCs). To that end, immunotherapies have had limited efficacy in improving outcomes for primary and secondary HGGs.

HYPOTHESIS

We hypothesize that engineered myeloid cells that release IL-2 will enhance the trafficking of activated effector T cells and potentiate a pro-inflammatory cascade in the low-grade glioma TME, delaying malignant progression.

METHODS

Immunocompetent RCAS n/tv-a LGG bearing animals were retro-orbitally treated at day 21 with a single dose of bone-marrow derived myeloid cells, engineered for the release of Interlekin-2 (GEMys-IL2). The inflammatory status of the TME along with the composition and functional status of tumor infiltrating immune cells were investigated in vivo by cytokine array, mass cytometry, and bulk RNA sequencing.

RESULTS

Our complementary dataset demonstrated that GEMys-IL2 infiltrated the glioma microenvironment and triggered a pro-inflammatory cascade involving the upregulation and release of IL2, IFNy, CXCL9, Tim1, CD26 and other pro-inflammatory cytokines associated with the activation and recruitment of innate and adaptive immune cells within the TME. In addition, we observed a downregulation of immunosuppressive signaling pathways such as IL10, PPAR, LXR/RXR, CTLA4 and PD-1. Also, a single dose of GEMys-IL2 systemically injected in RCAS/t-va immunocompetent LGG bearing mice potentiated pro-inflammatory remodeling of the TME and significantly improved overall survival.

CONCLUSIONS

These preclinical studies highlight a novel approach in developing next-generation innate immunotherapies.
TMIC-60. CROSS-SPECIES ANALYSIS OF HUMAN AND NEW MOUSE MODELS OF GBM SUBTYPES IDENTIFIES VISTA AS A PROMISING IMMUNOTHERAPY TARGET
Authors: Madonado Jose , Wang Caiyi , Leu Jia-Shiun , Wong Thomas , Abdelfattah Nourhan , Gallup Thomas , Paik Jihye , Squatrito Massimo , Yun Kyuson
Published: November 2023

Immunotherapy is a promising treatment modality for GBM; however, clinical trials thus far have failed to provide significant clinical benefit to most patients. GBM is one of the “immune cold” tumors characterized by poor infiltration of T cells and the abundance of immune-suppressive myeloid cells that block T cell infiltration and/or activation. A major bottleneck to developing more effective immunotherapies is the paucity of faithful preclinical models to discover and validate new treatments. Here, we report multi-dimensional analyses of six different transplantable mouse glioma models in the C57BL6/J background that represent the three human GBM molecular subtypes. We performed whole exome sequencing, STR fingerprinting, immune phenotyping, and single-cell RNA-sequencing of each model and confirmed that the new models exhibit highly heterogeneous and immune suppressive TME, similar to human GBM. In addition, we performed cross-species comparisons of glioma and immune cell subtypes between human and mouse GBMs at the single-cell level and demonstrate strong concordances in molecular phenotypes and cellular heterogeneity. These result in qualitative and quantitative differences in the cell: cell communication among different stromal cells and glioma cells in each model, and we propose that these interactions shape the local niche and immune suppressive neighborhoods. Notably, in both human tissues and mouse models, PD1/PDL1 expression is low or sporadic, and, unlike the GL261 model, the new mouse models are resistant to anti-PD1 and CTLA4 treatment in vivo. Finally, we discovered that VISTA is a widely expressed immune checkpoint in both human and mouse GBM and demonstrate the efficacy of anti-VISTA and anti-PD1 combination therapy in the most immune-suppressive mouse model. In summary, we demonstrate the utility of these immune-competent mouse models and nominate anti-VISTA+PD1 treatment as a promising novel combination therapy for GBM.
TMIC-61. INVESTIGATING REPROGRAMING OF THE GBM’S TUMOR MICROENVIRONMENT AS A RESULT OF CO-TRANSFER OF HEMATOPOIETIC STEM CELLS (HSCS) WITH ADOPTIVE CELLULAR THERAPY
Authors: Reid Alexandra , Jin Dan , Dean Bayli DiVita , Font Laura Falceto , Francis Connor , Figg John , Flores Catherine
Published: November 2023

Glioblastoma (GBM) is an incredibly aggressive and prevalent primary CNS tumor with dismal survival outcomes. GBM’s intra-tumor heterogeneity and the powerful regulatory mechanisms within the tumor microenvironment (TME) that hamper immune activation have proved to be formidable challenges to the development of effective therapies. Fortunately, immunotherapy has emerged as a potentially powerful approach to achieve of immune activation within the TME through adoptive immunotherapy and checkpoint inhibition Our previous work has demonstrated that the survival benefit of adoptive cellular therapy (ACT) is significantly enhanced by concomitant transfer of bone marrow derived hematopoietic stem cells (HSC) with tumor-reactive T cells in preclinical models. Using a novel organotypic brain slice culture (BSC) model study using glioma-bearing C57BL/6J mice, we interrogate tumor microenvironment and directly demonstrate that the presence of HSC-derived cells in the microenvironment increases T cell migration to tumor, and increased tumor cell death. In addition, we can investigate reprogramming of the TME as a result of treatment with this ACT+HSC platform. These studies are unique in that through this model system, we are capable of studying the cell-cell interactions occurring within the tumor microenvironment TME longitudinally while accounting for the complexity and the spatial orientation of the components within the TME that promote immunosuppression and tumor escape.
TMIC-62. COMPLEMENT FACTOR H IS A NOVEL LIGAND FOR THE INDUCIBLE T CELL CO-STIMULATOR AND PROMOTES SURVIVAL OF REGULATORY T CELLS IN THE GLIOMA MICROENVIRONMENT
Authors: Smolag Karolina , Olszowka Jakub , Rosberg Rebecca , Johansson Elinn , Marinko Elisabet , Leandersson Karin , O′Connell David , Governa Valeria , Tüysüz Emre Can , Belting Mattias , Myriam Martin , Pietras Alexander , Blom Anna
Published: November 2023

The survival rates of glioma patients have not shown significant improvement in recent years despite aggressive treatment and advancements in immunotherapy. This lack of response to treatment can be attributed in part to the immunosuppressive microenvironment commonly found in gliomas, where regulatory T cells (Tregs) play a critical role in immunologic tolerance. In this study, we aimed to investigate the influence of complement factor H (FH) on Tregs within the glioma microenvironment. Our findings revealed that FH acts as a novel ligand for the inducible T cell costimulator (ICOS). This interaction between FH and ICOS promotes the survival of Tregs. Furthermore, FH enhances the functional capabilities of Tregs that are crucial for modulating the tumor microenvironment. These include the secretion of transforming growth factor beta and interleukin 10, as well as the suppression of effector T cell proliferation. Immunostaining of human and mouse gliomas demonstrated that cancer cells directly produce FH. Additionally, database analysis revealed an association between upregulated FH expression, the presence of Tregs, and poor prognosis in glioma patients. We validated these findings in a glioma mouse model, where knockdown of FH expression showed a clear tendency to prolong survival. Given that the accumulation of Tregs is indicative of a poor prognosis and represents a promising target for therapy, it is crucial to consider FH expression when evaluating the effectiveness of immunotherapies against glioma.
TMIC-69. TARGETING TUMOR-ASSOCIATED MACROPHAGES IN THE IMMUNE-MICROENVIRONMENT OF MENINGIOMAS
Authors: Lotsch Catharina , Warta Rolf , Trong Philip Dao , Unterberg Andreas , Herold-Mende Christel
Published: November 2023

Meningiomas represent the most common primary brain malignancies in adults with a subset of tumors exhibiting aggressive clinical behavior. Immunotherapy might present a new treatment strategy but is highly dependent on the immunological composition of the tumor microenvironment. Our previous data have shown that tumor-associated macrophages (TAMs) make up the main immune cell population in meningiomas with a significant negative impact on patient outcome. In this study, we investigated whether TAMs from meningioma tissue could be reprogrammed to an immunologically active and tumoricidal phenotype. For this purpose, CD11b+ sorted macrophages derived from > 40 patients were treated with small molecule inhibitors targeting the colony-stimulating factor-1 receptor (CSF-1R). In a first analysis, the direct treatment response of CD11b+ patient-derived macrophages was investigated by various techniques including flow cytometry and bulk RNA-sequencing of treated TAMs and further analysis of the macrophage-conditioned media after treatment. In addition, we studied the influence of CSF-1R-targeted macrophage treatment on the phenotype and functional activity of T cells to assess a potential indirect treatment response in the tumor microenvironment. Our data revealed that CSF-1R-targeted treatment of CD11b+ TAMs induced significant changes in the protein and gene expression of macrophage polarization markers towards a more immunologically active state and a significantly higher metabolic nitric oxide production as another sign of immunological activation. Subsequent analysis of indirect effects on T cells showed not only a significantly increased expression of the T cell activation marker CD69+, but also a significantly increased tumor cell killing by autologous T cells after macrophage-targeted treatment. Together these data suggest both a direct and indirect CSF-1R-targeted macrophage treatment response in the local tumor microenvironment and give first promising results on the efficacy of macrophage-targeted immunotherapy in human meningiomas.
TMIC-75. SPATIALLY-RESOLVED TRANSCRIPTOME ANALYSIS OF BRAIN METASTATIC BREAST CANCER REVEAL KEY MEDIATORS OF BRAIN-TROPIC METASTATIC POTENTIAL
Authors: Umeh-Garcia Maxine , Godfrey Bryanna , Perez Pablo Nunez , Varma Sushama , Ahmadian Saman , Toland Angus , Granucci Monica , Averbukh Inna , Tian Lu , West Robert , Angelo Michael , Plevritis Sylvia , Gephart Melanie Hayden
Published: November 2023

BACKGROUND

In women with metastatic breast cancer, 30% (HER2+) to 50% (triple negative) develop brain metastases. Breast-to-brain metastasis carries a poor median survival of only 10 months and is accompanied by severe neurologic decline. Halting the progression of breast cancer brain metastases requires modulation of the tumor microenvironment (TME), yet little is known about how the primary breast TME affects brain tropism, or how, once there, metastatic cancer cells interact with normal brain cells (e.g., neurons, astrocytes, microglia).

METHODS

We constructed a large (n = 253 cores), diverse, clinically-annotated tissue microarray (TMA) of breast cancer brain metastases with surrounding brain (n = 127), associated primary breast tumors (n = 67, with 30 matched), normal brain (n = 23), and staining control (n = 18) tissue samples, from patients (n = 140) treated at Stanford Hospital between 2008 – 2018. We then leveraged a combination of genome-wide transcriptome analysis and high resolution spatial imaging (using GeoMx Digital Spatial Profiling) to interrogate the distinct, spatially-driven gene signatures of tumor, immune, and normal brain cells within the breast cancer brain metastasis TME.

RESULTS

We revealed novel gene regulatory programs that are associated with metastatic potential from the primary breast to the brain. We also identified not only diverging features of the breast and brain TMEs, but equivalent features which may contribute to preferential honing and outgrowth of metastatic breast cells in the brain microniche. Additionally, we uncovered significant cellular crosstalk between tumor, immune, and brain cell populations, including putative cell-cell interactions and intercellular signaling pathways.

CONCLUSION

These results served as a starting point for identifying key tumor-immune-brain interactions responsible for priming immune and brain tolerance of malignant cells, allowing outgrowth and progression of breast cancer brain metastases. Further investigation focused on tumor-brain crosstalk, specifically tumor-microglia interactions, will provide promising targets for therapeutic advancements.
TMIC-76. GLIOBLASTOMA VESSEL CO-OPTION OCCURS AS A RESISTANCE MECHANISM TO CHEMORADIATION VIA INDUCTION OF A NOVEL CELL STATE
Authors: Pettiwala Aafrin M , Pichol-Thievend Cathy , Anezo Oceane , Bourmeau Guillaume , Montagne Remi , Lyne Anne-Marie , Guichet Pierre-Olivier Guichet , Deshors Pauline , Ballestin Alberto , Blanchard Benjamin , Ravi Vidhya M , Joseph Kevin , Heiland Dieter Henrik , Julien Boris , Leboucher Sophie , Besse Laetitia , Legoix Patricia , Furumaya Charita , Marcos Laura Kovandzic , Masliantsev Konstantin , Daubon Thomas , Schnell Oliver , Beck Jürgen , Servant Nicolas , Karayan-Tapon Lucie , Cavalli Florence , Seano Giorgio
Published: November 2023

Glioblastoma (GB) is one of the deadliest types of human cancer. Despite a very aggressive treatment regime-including resection, chemo-radiation, its recurrence rate is more than 90%. Recurrence is mostly caused by highly resistant and invasive cells that spread from tumor bulk and are not removed by resection. To develop an effective therapeutic approach, we need to better understand underlying molecular and cellular mechanism driving therapy resistance and invasion in GB. To dynamically track the changes post-therapy and chemoradiation-resistant cells, we employed multiple bulk and single cell transcriptomics, phosphoproteome, in vitro and in vivo real time imaging, organotypic cultures, functional analysis, digital pathology and spatial transcriptomics on patient material and preclinical models of GB. We demonstrated that the chemoradiation and brain vasculature induce a transition to invasive functional cell state, which we rename as VC-Resist. Better cell survival, G2M arrest, senescence/stemness pathway induction, makes this GB state much more resistant. Notably, these GB cells are highly vessel co-opting allowing homing to perivascular niche, which in turn increases their transition to this cell state. Molecularly, the transition to VC-Resist cell state takes place through FGF-FGFR1 signaling that leads to activation of DNA damage repair, YAP and Rho pathways. These findings demonstrate that the perivascular niche and GB cell plasticity jointly generates a vicious loop that leads to resistance and brain infiltration during GB recurrence.
TMIC-77. UNVEILING THE DEPTHS: EXPLORING DIFFUSE MIDLINE GLIOMA, TUMORIGENESIS, AND RADIATION RESISTANCE
Authors: Patel Palak , Kukreja Bharti , Kalish Brian , Pajovic Sanja , Hawkins Cynthia
Published: November 2023

Diffuse Midline Glioma (DMG) is a highly aggressive form of brainstem cancer that primarily affects children, leading to a grim prognosis and limited treatment options. Despite extensive research efforts, many crucial aspects of DMG development and progression remain poorly understood. One significant knowledge gap lies in comprehending the invasive nature of DMG cells, which enables their escape from the primary tumor site and dissemination to other regions of the brain. Additionally, understanding the molecular basis that drives this invasive behavior is essential but remains largely unexplored, necessitating further investigation. To address these critical knowledge gaps, we have generated one of the largest single-cell multi-omic datasets ( >300,000 cells) specifically focusing on pons development in humans and its relation to DMG. This dataset provides a valuable resource for investigating the intricacies of tumorigenesis and the development of resistance to radiation therapy. Comprehensive analyses of this dataset shed light on the molecular events driving DMG progression and radiation resistance, ultimately paving the way for the discovery of novel therapeutic targets and the development of innovative strategies to combat this devastating pediatric cancer. In summary, our study aims to deepen our understanding of DMG by elucidating the mechanisms associated with histone mutations, unraveling the invasive behavior of DMG cells, and exploring the factors contributing to radiation resistance. Through these endeavors, we hope to make significant advancements in the field and improve the outcomes for patients affected by DMG.
TMIC-81. DECODING THE ROLE OF MICROENVIRONMENT ON DISTINCT FAILURE PATTERNS OF MALIGNANT GLIOMAS
Authors: Choi Seung-Won , Rabadan Raul
Published: November 2023

Most malignant gliomas experience recurrence with distinct failure patterns. The spatial relationship between the primary and recurrent tumors usually represents the genomic distanc; however, the molecular backgrounds of these failure patterns have not been evaluated yet. Our aim was to investigate the molecular profiles underlying the distinct failure patterns of malignant gliomas. This study involved 272 malignant glioma patients, with transcriptomic data available for 166 of these cases. The failure pattern was defined according to the spatial relationship between the primary and recurrent pairs including local recurrence, remote recurrence, and leptomeningeal seeding. When the recurrent tumor exhibits more than one failure pattern simultaneously, we define this as a combined failure pattern. Local recurrence was the most frequent pattern, followed by combined failure pattern (62.9% & 22.8%, respectively). Multi-variate cox analysis showed that combined failure pattern was a significant prognostic factor (odds ratio= 3.34, p-value < 0.001). We defined a genomic signature for malignant gliomas with a combined failure pattern (comb-GS) and validated its worse prognostic impact in other cohorts (GLASS, TCGA). Using public scRNA-seq data with regional annotation, we found that two distinct non-tumor components, immune and neuronal components, contributed to the development of the combined failure pattern. This finding was well correlated with the variability of comb-GS in different anatomic regions in IVY-gap dataset. In summary, this study demonstrated that both immune and neuronal components are involved in the progression of malignant gliomas. These two microenvironmental elements exhibit a shared negative clinical outcome, despite presenting distinct phenotype. To decipher the exact biological role of each component, experimental validation is necessary.
TMIC-84. A DEEP LEARNING-BASED METHOD FOR RAPID, PATIENT-SPECIFIC ASSAY OF MACROPHAGE INFILTRATION IN HIGH-GRADE GLIOMA USING LABEL-FREE STIMULATED RAMAN HISTOLOGY
Authors: Alber Daniel , Lock Emily , Sangwon Karl , Smith Andrew , Movahed-Ezazi Misha , Oermann Eric , Hollon Todd , Orringer Daniel
Published: November 2023

BACKGROUND

5-Aminolevulinic acid (5-ALA), the most widely used fluorophore in image-guided glioma surgery, identifies tumor-associated macrophages (TAM) in high-grade glioma (HGG) tissue. Infiltrating macrophages, the predominant immune cells in glioma, are highly implicated in tumor progression, recurrence, and treatment response – particularly in immunotherapy. Using a unique, paired dataset of label-free stimulated Raman histology (SRH) and two-photon microscopy (TPEF) images sharing one-to-one spatial resolution, we developed a deep-learning approach to automatically quantify TAM infiltration from intraoperatively acquired SRH images.

METHODS

We compiled a dataset of 906 paired whole-slide SRH/TPEF images from 79 patients with HGG. We first trained a pix2pix generative adversarial network to convert raw, label-free SRH into synthetic TPEF with identifiable macrophages. Next, we trained a MaskR-CNN model to locate and segment TAMs. The pix2pix network was trained using 5,531 hand-picked 300-by-300-pixel fields-of-view (FOV) best exemplifying TAMs. We used a human-in-the-loop approach to train the segmentation network on 1,000 hand-labeled FOVs.

RESULTS

Macrophage segmentation from purely histologic data was near-identical to the fluorescence-based ground truth, with a mean dice score of 90.3%. Predicted TAM density was highly correlated with r=0.735. Subgroup analyses of TAM density in 346,836 non-overlapping FOVs revealed significantly lower TAM density in IDH-mutant (p< 0.01) and MGMT-hypermethylated (p=0.03) tumors. Our end-to-end algorithm uses fresh, unlabeled tissue specimens in the operating room and takes just three minutes to analyze whole-slide SRH images.

CONCLUSION

We demonstrate how deep neural networks can be used to rapidly and quantitatively evaluate macrophage infiltration in HGG in the operating room. Our software enables analysis of glioma patients’ tumor immune environment without immunohistochemistry or fluorescent labels, and may be leveraged to study the effects of immune-modulating therapies in the tumor microenvironment. Future work will focus on evaluating macrophage density and distribution as biomarkers for response to immunotherapies showing efficacy in glioma patients.
MODL-01. INTRACRANIAL TUMORS HIJACK THE MENINGEAL VENOLYMPHATIC NETWORK THROUGH VEGFR-2 SIGNALING
Authors: McGavern D , Ampie Leonel
Published: November 2023

INTRODUCTION

Glioblastoma and other intracranial neoplasms have been associated with breakdown of the blood brain barrier. Other protective CNS barriers have sparsely been studied in brain tumors. Here, we identify the ability of intracranial neoplasms to hijack the meningeal venolymphatic network, which is driven through VEGFR-2/VEGF-A signaling.

METHODS

C57BL/6J mice were stereotactically injected with syngeneic SB28 (glioblastoma) cell lines. Mice were treated with either isotype control or a VEGFR-2 inhibitor. Two-photon microscopy was used to visualize vascular cytoarchitecture and dynamics in vivo. Meningeal whole mounts, brains and spleens were also collected and analyzed by confocal microscopy and high parameter flow cytometry. Similar experiments were conducted with a PECAM-1 inhibitor to assess the role of endothelial cell crosstalk in venolymphatic expansion. Human dura mater from glioblastoma patients underwent multiplex immunohistochemistry to confirm the translatability of our findings.

RESULTS

Our imaging studies revealed that glioblastomas can generate an extensive de novo network of meningeal blood vessels and lymphatics both in mice and humans. Lymphatic vessels were often observed developing in parallel to the newly formed vasculature. Intravital two-photon microscopy further revealed that the peritumoral vascular bed in the meninges of mice was leaky, dysfunctional, and generated a hypoxic microenvironment. Importantly, inhibition of VEGFR signaling impeded formation of this faulty venolymphatic network, which slowed tumor growth, reduced peritumoral hypoxia, enhanced immune infiltration, and increased survival. PECAM-1 (CD31) inhibition had a similar effect on the tumor microenvironment, suggesting that endothelial cell crosstalk is required for glioblastomas to optimally invade the meninges.

CONCLUSION

Our results demonstrate that glioblastomas can invade the meninges and hijack the venolymphatic network through VEGFR-2 and PECAM-1 signaling. While VEGFR-2 is associated with angiogenesis, our data suggest that it may also have an important role in regulating the simultaneous development of de novo meningeal venous and lymphatic drainage during glioblastoma.
MODL-03. AN EX VIVO PLATFORM BASED ON ORGANOTYPIC BRAIN SLICE CULTURE FOR INFORMING PERSONALIZED BRAIN CANCER THERAPY
Authors: Zhang Xiaopei , Mann Breanna , Bell Noah , Adefolaju Adebimpe , Thang Morrent , Dasari Rajaneekar , Kanchi Krishna , Valdivia Alain , Yang Yang , Buckley Andrew , Lettry Vivien , Quinsey Carolyn , Rauf Yasmeen , Kram David , Cassidy Noah , Vaziri Cyrus , Corcoran David L , Rego Stephen , Jiang Yuchao , Graves Lee M , Dunn Denise , Floyd Scott , Baldwin Albert , Hingtgen Shawn , Satterlee Andrew B
Published: November 2023

While the improved classification of CNS tumors is already enhancing the scientific rigor of clinical brain cancer treatment guidelines, the impact of these integrated diagnoses based on histopathological features or molecular insight on precision oncology medicine has yet to demonstrate widespread clinical benefit. Patient tumor-derived cancer models, including patient tumor-derived cell lines, organoids, and explants, have provided practical models based on a patient’s individual tumor for effective therapeutic drugs. Importantly, patient tumor-derived organoids have shown potential to guide personalized care and optimize clinical outcomes by functionally predicting patient response to antitumor drugs prior to in vivo treatment. Our team has built an organotypic brain slice culture (OBSC)-based platform and multi-parametric algorithm that allows for the ex vivo engraftment, rapid treatment, and systemic analysis of resected patient brain tumor tissue. This OBSC platform has successfully supported engraftment of each patient tumor tested to this point, including high- and low-grade adult and pediatric tumor tissue. The established patient tumor-derived organoids show the ability to activate the endogenous astrocytes within OBSCs, which have been reported in brain tumor. Whole exome sequencing analysis showed that patient tumor tissue engrafted onto OBSCs maintained a significant genetic resemblance to their parent tumor, while tumor tissue expanded in vitro displayed a distinctly different DNA profile. Additionally, our algorithm calculates dose-response relationships of both tumor kill and normal brain tissue toxicity, generating summarized drug sensitivity scores based on therapeutic window and allowing us to normalize response profiles across a panel of FDA-approved and exploratory agents. Summarized patient tumor scores after OBSC treatment revealed positive associations to clinical outcomes, suggesting the OBSC platform can provide rapid, accurate, functional testing to ultimately guide patient care.
MODL-06. THE GUT MICROBIOTA OF BRAIN TUMOR PATIENTS CAN IMPACT IMMUNOTHERAPY EFFICACY IN A PRECLINICAL MODEL OF GLIOMA
Authors: Kim Donggeon , Sarvesh Sujith , Valbak Olivia , Backan Olivia , Chen Dongquan , Morrow Casey , Benvensite Etty , Nabors Burt , Bekal Mahesh , Dono Antonio , Esquenazi Yoshua , Forsyth Peter , Yu Hsiang-Hsuan Michael , Khushalani Nikhil , Egan Kathleen , McFarand Braden
Published: November 2023

Combination immune checkpoint inhibitors (ICI) can affect durable response in melanoma brain metastases (MBM) but have largely been ineffective for the treatment of glioblastoma (GBM), a primary brain tumor. Recent studies in animal models and humans have suggested that the microbe composition of the gut can influence the effectiveness of ICI in melanoma and other cancers. Our central hypothesis is that the gut microbiome can influence immunotherapy responsiveness for GBM patients. We obtained microbiome (stool) samples from GBM and MBM patients prior to beginning any treatment or surgical interventions. We then transplanted these microbiome samples into gnotobiotic mice to create humanized microbiome mice. We transplanted two GBM patients and two MBM patients microbiome samples to create 4 unique patient-derived humanized microbiome mouse lines (GBM1, GBM2, MBM1, and MBM2). Using 16s ribosomal RNA microbiome sequencing, we found that each patient-derived microbiome mouse line had a unique microbiome composition as measured by relative abundance and diversity of species. Mice from each line were then intracranially injected with GL261 murine glioma cells and treated with the ICI anti-PD-1 or isotype control. We found that MBM1 and GBM2 mice were resistant to anti-PD-1 and did not display prolonged survival with anti-PD-1 treatment. However, GBM1 and MBM2 mice were positive responders to anti-PD-1 and displayed significantly prolonged survival compared to isotype control. Additional microbiome sequencing analyses are ongoing that will reveal positive microbiome profiles among these patient-derived lines, and additional GBM and MBM patient-derived microbiome lines are being created and tested for immunotherapy efficacy. Ultimately, understanding how certain microbial communities can enhance the effectiveness of immunotherapy may lead to the development of new approaches that include modification or transplantation of microbe communities in GBM patients for increased therapeutic impact.
MODL-16. GLIOBLASTOMA GROWTH IS SHAPED BY INVASION ROUTE-SPECIFIC FUNCTIONAL SIGNATURES
Authors: Krona Cecilia , Rosén Emil , Kundu Soumi , Olausson Karl Holmberg , Larsson Ida , Elfineh Ludmila , Doroszko Milena , Elgendy Ramy , Wickström Johan , Jörnsten Rebecka , Nelander Sven
Published: November 2023

One of the defining features of glioblastomas (GBMs) is the capacity for invasive growth along multiple anatomical pathways in the brain. GBM is well-studied on a genetic and molecular level, but clinically relevant and experimentally tractable models of invasive growth are largely lacking. Here, we report an integrated study of patient-matched information, genomic- and molecular profiles with growth in mouse brains to expose treatments and biomarkers associated with glioblastoma invasion and recurrence. In total, 64 patient-derived cell lines (PDCLs) were injected into the striatum of n ≥ 4 mice each. The 45 tumor-forming PDCLs were each scored for 10 distinct growth characteristics (n = 182 mice). The repertoire of phenotypes was highly divergent, and our material included clear cases of perivascular route invasion, white matter route invasion, perineuronal satellitosis, and gliosarcoma. We explored if cellular pathways, monitored by RNA-sequencing, could account for these differences. GSEA highlighted a positive enrichment for highly proliferative proneural tumors characterized by Notch activation, neuronal signaling, and epigenetic gene regulatory programs in the tumor-initiating lines. Transcriptional signatures were also strongly predictive of route-specific invasion. Diffuse invasion was predominantly seen in classical-subtype PDCLs with astrocytic or outer radial glia-like signatures. Proneural PDCLs, in turn, grew as solid tumors with an invasive peripheral region around vasculature, and mesenchymal tumors were more demarcated. To explore the therapeutic implications of our findings, we used our data-driven method (TargetTranslator, Nat Comm 2020) to predict the drug vulnerabilities of different types of invasive glioblastoma. Defined GBM tumors with perivascular invasion are characterized by increased IGFR1, MAPK/ERK, PI3K/AKT/mTOR, and JAK2 signaling. Diffusively growing GBM tumors, on the other hand, depend more on Wnt/β-catenin signaling, neuronal signaling, and active inflammatory response. Using a sphere invasion assay, we confirm that targeting both PI3K- and Wnt signaling selectively reduces glioblastoma invasion, highlighting their therapeutic potential.
MODL-19. DEVELOPMENT OF A RECURRENT GLIOBLASTOMA MURINE MODEL FOLLOWING SURGICAL RESECTION: INVESTIGATING THE TUMOR-IMMUNE MICROENVIRONMENT TO EVALUATE NOVEL PERIOPERATIVE THERAPIES
Authors: Das Arabinda , Stephens Heather R , Mark Joe , Garrison Jeff , Sekerak Penny , Baraso Randy , McDonald Daniel G , Yazdani Milad , Welsh Cynthia A , Infinger Libby Kosnik , Eskandari Ramin , Vandergrift III William A , Varma Abhay K , Patel Sunil J , Cachia David , Zukas Alicia M , Lindhorst Scott M
Published: November 2023

BACKGROUND

Most glioblastoma (GBM) patients experience tumor recurrence following standard-of-care treatment which includes tumor resection, radiation, and chemotherapy with concomitant and adjuvant temozolomide. Currently, no murine surgical GBM resection models to evaluate novel therapies exist and understanding of postsurgical tumor microenvironment (TME) has yet to be fully elucidated in pre-clinical GBM models.

METHODS

GL261 GBM cells were orthotopically implanted in C57BL/6 mice on day 1. On day 14, tumor resection was performed using the NICO Murine Neuroscience System, an automated, intraoperative, pre-clinical surgical resection system designed to minimize damage to surrounding tissue thus preventing the need for animal sacrifice. Standard T2-MRI and Terason uSmart 3200T ultrasound system were used to analyze tumor size following resection and recurrent growth. Immunological and biochemical assays were performed to explore local TME.

RESULTS

We observed that surgically resected GL261 GBM mice survived 55 + 8 days whereas mice with unresected GBM survived 35 + 7 days following tumor implantation. This new preclinical surgical resection recurrent immunocompetent GBM (Sur-rGBM) model was used for analyzing TME. Our results demonstrated significant changes in TME, such as an increase in astrocytic activation (GFAP+), increased microglia/macrophage (CD11b+, and IBA-1+) infiltration to surrounding tissue, increase in M2 macrophage (TGM2+ and CCL22+) and NK regulatory cells (CDC 26 +), and increased angiogenesis (VEGF) in Sur-rGBM as compared to unresected GBM. We also observed increased proliferation (Ki-67) and upregulation of stem cell markers CD133, Nestin, and Olig2 at the protein level.

CONCLUSION

Our data demonstrated the upregulation of tumor-promoting activation factors in Sur-rGBM as compared to unresected GBM. Currently, the Sur-rGBM model does not fully resemble the entire treatment regimen offered to GBM patients. Thus, our future aim is to further refine this resection model and assess adjuvant therapies at different time points along disease progression without needing to sacrifice the animal for analysis of tissue.
MODL-20. PRECLINICAL MODELING OF LASER INTERSTITIAL THERMAL THERAPY IN MURINE BRAIN TUMORS FOR TRANSLATIONAL IMMUNO-ONCOLOGY
Authors: Haskell-Mendoza Aden , Wachsmuth Lucas , Tyc Richard , Fecci Peter
Published: November 2023

INTRODUCTION

Cytoreductive surgery is a cornerstone of management for intracranial tumors. However, resection may remove an important source of neoantigen. In the case of laser interstitial thermal therapy (LITT), ablated tumor remans in situ, allowing for an anti-tumor immune response. To characterize these phenomena, we developed a murine model of LITT for use with syngeneic brain tumor cell lines.

RESULTS

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METHODS

To establish anatomical boundaries for our ablation, we characterized our CT-2A glioma model on T2 MRI, selecting 10 days post-implantation for LITT based on lesion size. We simultaneously implanted a 400 μm laser fiber and thermocouple probe into the center and edge of the target volume, respectively, for simultaneous ablation and temperature monitoring. Using a clinical 1064 nm Nd:YAG laser, we first performed a dose titration of laser power/time in normal mouse brains, finding that doses above 1.5 W for 60s produced cavitary lesions with charring that resulted in death at 24h post-LITT. We therefore selected 1 W for 60s as a safe laser power dose in our tumor model. Ablations at this setting rapidly heated the lesion edge to a peak temperature of mean 43.79 ± 2.993 °C, sparing the surrounding brain. MRI imaging at 1, 3, and 7 days post-LITT revealed expansile T2 hyperintense lesions that resolved over time, with hemorrhage and necrosis on H&E. LITT increased survival to 28 from 25.5 days (vs sham, P = 0.0172).

CONCLUSIONS

Our model successfully recapitulates the essential clinical features of LITT: a cytoreductive survival benefit; lesion expansion on MRI; and focal necrosis with hemorrhagic vasculature on H&E. This model is well suited for study of LITT-adjunctive interventions and characterization of the immunobiology of hyperthermia.
MODL-21. INVESTIGATING THE PATHOGENIC MECHANISMS OF FOXR2-MUTATED PEDIATRIC BRAIN TUMOR USING A HUMAN-EMBRYONIC STEM CELL-BASED MODEL
Authors: Royston Hitomi , Emerson Miriam , Hampton Autumn , Funato Kosuke
Published: November 2023

FOXR2-activated CNS neuroblastoma is a recently identified subtype of brain tumor characterized by genomic rearrangements at the FOXR2 locus and elevated expression of the transcription factor FOXR2. However, the precise mechanisms underlying the tumorigenesis of this specific subtype, including the cell type of origin, are not fully understood. In this study, we established a new tumor model using human embryonic stem cells (hESCs) to determine the cell type of origin and the underlying pathogenic mechanisms. Expression profile analysis of patient tumors revealed increased expression of interneuronal marker genes, such as DLX1, NKX2.1, and SST (Somatostatin). Given that NKX2.1 and SST are markers for interneuronal cells originating from the Medial Ganglionic Eminence (MGE) in the ventral forebrain, we hypothesized that MGE-derived interneuronal progenitors are the cell type of origin. To test this hypothesis, we differentiated hESCs into MGE-type interneuronal progenitors using a chemically defined protocol, while using cortical excitatory neural progenitors as a control cell type. Subsequently, we overexpressed FOXR2 in these cell populations and analyzed the cellular phenotype. Our data showed that, in low density culture, FOXR2 overexpression in the MGE-type interneuronal progenitors led to a significantly greater increase in proliferation compared to the cortical progenitor cells, indicating a cell-type-specific effect of FOXR2. Our novel model holds great promise for elucidating the molecular mechanisms underlying the formation of FOXR2-activated CNS neuroblastoma and paving the way for the discovery of therapeutic targets and effective treatments for patients suffering from this devastating disease.
MODL-23. PAIRED GLIOBLASTOMA CELL CULTURES OF THE FLUORESCENT BULK TUMOR AND NON-FLUORESCENT TUMOR MARGIN DISPLAY DIFFERENTIAL PHENOTYPES AND CELL STATES ACROSS PATIENTS
Authors: Neves Inês , Maturi Nagaprathyusha , Dang Yonglong , Lu Xi , Latini Francesco , Yildirim Irem , Sundström Anders , Jokinen Veera , Bergström Tobias , Xing Pengwei , Jarvius Malin , Larsson Rolf , Fryknäs Mårten , Ryttlefors Mats , Chen Xingqi , Swartling Fredrik , Uhrbom Lene
Published: November 2023

Glioblastoma is a devastating disease with a median survival of 8 months after diagnosis. Over 90% of patients have a recurrence that is in contact with the resection cavity. To understand the potential relapse-causing cells of the local infiltrative tumor margin, which have rarely been studied, we have established and analyzed paired cell cultures from the fluorescent bulk tumor and non-fluorescent tumor margin. Tumor samples were resected using 5-ALA fluorescence-guided surgery and employing stringent procedures to separate margin samples from bulk tumor cells. All margin samples were resected at least 1cm beyond the fluorescent border in non eloquent areas as determined intraoperatively. Bulk and margin samples from 13 glioblastoma patients were explanted and 7 paired cultures that could be maintained to at least passage 7 were established. Analysis of self-renewal and orthotopic tumor formation of both acutely dissociated cells and established cultures showed that bulk tumor cells in all cases had a higher capacity than their paired margin cells. Conversely, margin cells always displayed a higher invasive capacity than their paired bulk tumor cells. Combined single nucleus RNA- and ATAC-sequencing was performed on three paired cultures. Analysis of snRNA-seq data showed that the margin cell phenotype was connected with transitions towards more differentiated (AC- and MES-like) cell states compared to paired bulk tumor cells that showed a higher rate of cells in progenitor cell-like states (NPC- and OPC-like). snATAC analysis uncovered that the margin cell phenotype was connected with transcription factor (TF) motifs known to be involved in cell invasion and differentiation, while paired bulk tumor cells were enriched for TF motifs involved in neural development and proliferation. We present a unique collection of margin cell cultures that we believe are more relevant models of the relapse-causing glioblastoma cells than those established from the bulk tumor.
MODL-25. INTERNAL CAROTID INJECTION MODEL OF BRAIN METASTASIS DESCRIBES LEPTOMENINGEAL DISEASE
Authors: Chernikova Sophia , Tsau Sheila , Wang Yuelong , Hartmann Griffin , Polyak Dina , Bhambhvani Hriday , Kolluru Sai Saroja , Trinh Thy , Casey Kerriann , Johnson Eli , Connolly Ian , Recht Lawrence , Ahn G-One , Nagpal Seema , Quake Stephen , Brown J Martin , Gephart Melanie Hayden
Published: November 2023

Leptomeningeal disease (LMD), the most aggressive form of central nervous system (CNS) metastasis in which cancer cells infiltrate leptomeninges, is universally and rapidly fatal due to poor detection and no effective treatment. Treatment of LMD is challenged by the diffuse nature of the disease, low specificity of detection, poor drug penetration into CNS and high neurotoxicity. LMD is a heterogeneous disease: co-existence of leptomeningeal spread and parenchymal brain metastases in not uncommon, and LMD tumors vary in size and may be found at various locations throughout entire neuroaxis. Radiographic detection (i.e., MRI) works well for big “bulky” metastases but may produce normal results in patients with active disease identified by cerebrospinal fluid (CSF) tap. This spatial and morphological heterogeneity of LMD may ultimately be responsible for a varied and limited therapy response. Mechanistic and translational studies of LMD are hampered by the lack of adequate in vivo models that recapitulate the consecutive steps of LMD progression separate from systemic disease. In this study, we show that the internal carotid (ICA) injection of tumor cells, which is widely used to model brain metastasis, produces leptomeningeal spread. The ICA injection of various tumor cell lines faithfully recapitulated the stages, heterogeneity, and spatial distribution of human LMD. While some cell lines demonstrated clear preference for growth in brain parenchyma, they still had a measurable population of cells within the leptomeninges. Most bulky LMD metastases formed and grew near fenestrated endothelium, where the direct access to blood might support tumor growth and survival. A population not associated with the fenestrated endothelium consisted mostly of single non-dividing non-hypoxic cells. This diffuse cancer spread limited the efficacy of standard whole-brain radiation therapy. Thus, leptomeningeal spread should be taken into account when interpreting the data from the ICA model that is widely used to study brain metastasis.
MODL-26. A PROTOCOL TO ADAPT GLIOBLASTOMA IN VITRO CULTURE SYSTEMS INTO ORGANOID MODELS USING NEUROCULT™ NS-A PROLIFERATION MEDIUM
Authors: McCormack Kasandra , Mak Carmen , Eaves Allen , Louis Sharon , Knock Erin
Published: November 2023

Glioblastoma (GBM) is a malignant and aggressive brain tumor that is difficult to treat due to its heterogeneity. Traditional in vitro models (i.e. monolayers and tumorspheres) do not recapitulate this heterogeneity, leading to difficulty assessing new therapeutic strategies. Culturing GBM cells as organoids may provide a better method to retain the phenotype of the parent tumor. Here, we present a protocol for generating GBM organoids using NeuroCult™ NS-A Proliferation Medium, a medium commonly used for tumorsphere cultures. Two methods were assessed for the initial stage of formation, each suitable depending on throughput and cell source. In the first method, tumorspheres were dissociated and single cells were mixed with Growth Factor Reduced Matrigel® at a 1:4 ratio to form 15 μL droplets with 1000 cells per droplet. In the second method, 9000 cells from dissociated tumorspheres were seeded per well in a 96-well U-bottom plate and cultured for 5 days to form aggregates. On day 6, the aggregates were embedded in 15 μL Matrigel® droplets. In both methods, polymerized droplets were then cultured in suspension in stationary 6-well plates for 3 days, then maintained on an orbital shaker with full-medium changes every 2 - 3 days. Organoids were cryosectioned and processed for immunofluorescence at 5 - 6 weeks. In vivo, GBM tumors display an architecture containing regions of high and low nutrient and oxygen availability around a necrotic core. GBM organoids generated using this protocol exhibited distinct areas of proliferation near the organoid rim (Ki67+) and hypoxia (CA9+) near the core, mimicking this in vivo architecture (n = 3 GBM cell lines). Organoids grew to 2 - 4 mm in diameter and expressed glioma markers including TUJ1, Nestin, SOX2, OLIG2, and GFAP. These data show that NeuroCult™ NS-A Proliferation Medium can be used to adapt traditional GBM culture systems into organoids.
MODL-27. INTEGRATING OVERALL SURVIVAL AND TUMOR CONTROL PROBABILITY MODELS TO PREDICT LOCAL PROGRESSION AFTER BRAIN METASTASIS RADIOSURGERY
Authors: Quezada Jeffrey , Harris Jeremy , Healy Erin , Seyedin Steven , Chen Allen , Kuo Jeffrey , Simon Aaron
Published: November 2023

PURPOSE

Stereotactic radiosurgery (SRS) for brain metastases has competing goals of maximizing local control and minimizing toxicity. Tumor control probability (TCP) models predict decreasing risk of local progression (LP) with dose escalation. However, many patients die from extracranial disease prior to local progression and may not require maximally aggressive treatment, which increases risk of toxicity. Better tools to assess patients’ risk of LP after SRS could help practitioners personalize SRS treatment to maximize therapeutic ratio. Here we assess whether simultaneous modeling of TCP and overall survival (OS) can improve prediction of LP after SRS.

METHODS

Records of patients undergoing SRS at a single institution were reviewed retrospectively. Using established OS and TCP models, the probability of one-year survival [p(OS)] and probability of one-year LP [p(LP)]) were calculated for each patient and each metastasis, respectively. Joint-probability was used to combine the models [p(LP,OS)=p(LP)*p(OS)]. Analyses were conducted at the individual-metastasis and whole-patient levels. Fine-Gray regression was used to model the effect of p(LP) or p(LP, OS) on risk of local progression after SRS, with death as a competing risk.

RESULTS

Ninety-two patients and 391 lesions were identified. At the patient level, one-year LP was 0.08 (95%CI, 0.03-0.15), median p(LP,OS) was 0.13 (95%, CI 0.07-0.2), and median p(LP) was 0.29 (95% CI, 0.22-0.38). At the metastasis level, one-year LP was 0.02 (95%CI, 0.01-0.04), median p(LP,OS) was 0.05 (95%, CI 0.02-0.07), and median p(LP) was 0.10 (95% CI, 0.07-0.13). p(LP,OS) was significantly associated with the risk of local progression at the patient level (p=0.048) and metastasis level (p=0.007); however, p(LP) was not (p=0.16 and p=0.28, respectively).

CONCLUSION

This study suggests simultaneous OS and TCP modeling more accurately predicts LP than TCP modeling alone. Better understanding which patients are at risk of LP after SRS may help personalize treatment to minimize risk without sacrificing efficacy.