bluuebunny/crossref_metadata_2025_split huggingface dataset:
TAMI-58. A NOVEL ROLE FOR REST IN THE CONTROL OF THE MEDULLOBLASTOMA MICROENVIRONMENT
Authors: Shaik Shavali , Maegawa Shinji , Sharma Ajay , Haltom Amanda , Dobson Tara , Yang Yanwen , Schadler Keri , Gopalakrishnan Vidya 
Published: December 2020

Abstract
The REI Silensing Transcription Factor (REST) is a transcriptional repressor and a canonical regulator of neurogenesis. Its expression is elevated in human sonic hedgehog (SHH) subgroup of medulloblastomas (MBs), where functional studies shown its elevated expression to promote proliferation and block neuronal specification. A role for REST in the control of the MB tumor microenvironment (TME) has not been described previously. Here, we demonstrate that REST also controls the MB-TME, and specifically vascular remodeling. Using our unique RESTTG mouse model, we show that conditional expression of human REST transgene in cerebellar granule neuron progenitors (CGNPs), the cell of origin of a subset of SHH MBs, promoted increased vascular growth. In the context of constitutive activation of SHH signaling, a key driver of SHH-MB development, REST elevation drove tumor progression by altering the tumor vasculature. These findings were validated in mouse orthotopic models of human MB cell lines and through analyses of publicly available transcriptomic database of human MB samples. A strong positive correlation between REST and that of endothelial genes CD31/VEGFR1/ETS1 was seen in samples from patients with SHH-MBs subtypes that are associated with the worst prognosis. Proteomic analyses identified increased secretion of a number of pro-angiogenic factors in the context of upregulated REST expression in MB cells. Unexpectedly, in vitro and in vivo studies showed that MB cells expressed these endothelial markers and co-localized with endothelial cells suggesting that REST elevation may have altered the fate of cells that were destined to become neurons. Finally, ETS1 knockdown in MB cell lines not only downregulated VEGFR1 levels in these cells, and blocked tube formation in vitro, but also caused a reduction in tumor cell co-localization with endothelial cells. Collectively, these data suggest that REST elevation remodels MB vasculature through cell-intrinsic and cell-extrinsic mechanisms.
TAMI-60. EXPLORING METABOLIC DIFFERENCES IN VARYING GRADES OF MENINGIOMAS THROUGH NONTARGETED MASS SPECTROMETRY
Authors: Rabow Zach , Morningstar Taryn , Lechpammer Mirna , Fiehn Oliver 
Published: December 2020

Abstract
Emerging molecular data demonstrates the importance of genomic and epigenetic factors in pathogenesis of meningioma. Understanding the metabolic landscape using mass spectrometry is needed to overcome significant uncertainty in predicting tumor behavior and the risk of recurrence. Current technologies lack sensitivity and selectivity, which hinders the discovery of potential novel diagnostic and prognostic features. Here, we present a nontargeted metabolomics approach applied to meningiomas for biomarker discovery and identification of potential therapeutic targets. Fresh frozen tissue from 36 patients (57% women, 43% men; mean age: 48) who underwent surgical resection for newly diagnosed meningiomas and 9 patient samples with non-neoplastic dura were used for case/control comparison. Additionally, 16 patient-derived meningioma cell lines (Grade I-III), 2 immortalized human cell lines (IOMM-Lee and Ch157MN) and immortalized arachnoid cells were used to further explore metabolic changes in meningiomas. Metabolites were extracted from tissue and cells for GC-TOF (primary metabolism), RPLC ESI (±) (lipidomics) and HILIC ESI (±) (biogenic amines) coupled to high-resolution mass spectrometry for analysis. Metabolites were identified using authentic standards, retention time, and MS2 fragmentation. Over one thousand known metabolites were identified and annotated as well as over 300 unknown metabolites. Metabolites were grouped into one of fifteen classes based on chemical ontology and function. Bis(monoacylglycero)phosphates were over 2-fold increase in atypical (Grade II) meningiomas versus Grade I, indicating lysosomal activation. One carbon metabolism pathway showed significant upregulation in neoplastic tissue vs. tumor involved dura, as well as neoplastic cells compared to arachnoid cells, indicating folate-dependent pathways as a potential therapeutic target. Using novel combined untargeted metabolomics, we found multiple classes of metabolites that were either enriched or suppressed in neoplastic tissue and cells compared to non-neoplastic cells. Further studies are warranted for a better understanding of possible oncogenic signaling pathways and to detect potential biomarkers useful for diagnosis and treatment.
TAMI-63. GLIOBLASTOMA ASSOCIATED MESENCHYMAL STEM LIKE CELLS (G-MSC) WHICH INFILTRATE TUMORS IN HUMAN AND MOUSE ARE STRONGLY ASSOCIATED WITH IMMUNOSUPPRESSION
Authors: Dharma Sanam , Figel Sheila , Barone Tara , Ciesielski Michael , Fenstermaker Robert 
Published: December 2020

Abstract
Glioblastoma (GBM) is the most aggressive form of brain cancer with an overall survival (OS) less than 16 months. Glioblastoma associated mesenchymal stem like cells (G-MSC) were identified in human patient samples, and higher presence of these cells in patient samples co-relates with lower overall survival. Our lab and others have also identified these cells in orthotopic GL261 glioblastoma murine models. We hypothesize that infiltration of G-MSC plays a key role in creating the highly immunosuppressive environment seen in GBMs. In order to investigate this, we utilized data from the TCGA database to stratify patients into two groups, showing higher or lower expression of the G-MSC markers (CD73, CD90, CD105). Patients expressing higher levels of G-MSC markers showed higher expression of CD4+ cells, as compared to patients with lower G-MSC marker expression. Further, patients with higher G-MSC markers showed high levels of PTGS2, the gene encoding cyclooxygenase 2 (COX2), a known tumor growth promoting and immunosuppressive molecule. We further investigated CD4+ T cell infiltration using GL261 orthotopic implants and observed that CD4+ T cells positively corelated with levels of G-MSC in these tumors. Our studies indicate that levels of G-MSC co-relate with immune cell infiltration and the expression of immunosuppressive factors such as COX2, underlining the importance of these cells in immunosuppression-driven resistance to therapy. These studies will be later utilized to develop rationale combination therapies to improve the overall survival in GBM.
TMOD-04. INHIBITION OF MELANOMA BRAIN METASTASIS BY TARGETING miR146a
Authors: Wang Jiwei , Lunavat Taral , Zhou Wenjing , Feng Zichao , Hoang Tuyen , Thorsen Frits 
Published: December 2020

Abstract

INTRODUCTION
It is well known that cancer patients with brain metastasis (BM) have a poor prognosis and current treatments are not effective. It has been shown that BM development is caused by molecular interactions between the tumor cells and the normal brain, constituting the so-called brain metastatic niche. In this respect, miRNAs delivered by exosomes released by the primary tumor cells seem to be an important factor in BM niche establishment yet the mechanisms behind this process is poorly understood.

AIM
The aim of this project was to determine miRNAs released by exosomes from melanomas that may be important in establishing the BM niche, and to validate these findings in vitro and in vivo.

METHODS
We performed a miRNA profiling on exosomes collected from 3 human melanoma BM cell lines and from human astrocytes and melanocytes, to determine the most important differently expressed miRNAs. Functional in vitro validation was performed by cell growth and migration assays, cytokine arrays, qPCR and Western blots. Functional in vivo studies were performed after miR-knockdown in BM cell lines, in an experimental animal/tumor model.

RESULTS AND DISCUSSION
The miRNA profiling showed that miR-146a was by far the most differentially upregulated miRNA in exosomes from melanoma BM cell lines, compared to exosomes from normal cells. Mir-146a mimics activated human astrocytes, shown by increased proliferation and migration, elevated expression of GFAP in vitro and in mouse brain tumor samples, and increased cytokine production. These effects were reversed by adding anti-miR-146a to the experiments. In animal studies, knockdown of miR-146 in melanoma BM cells injected intracardially into nod/scid mice resulted in a significant reduction in BM burden, compared to wild type cells, and increased animal survival.

CONCLUSIONS
Inhibition of miR-146a reduces activation of the BM niche, leading to inhibition of BM development.
TMOD-07. HUMAN DIFFUSE MIDLINE GLIOMA AVATARS AS A PLATFORM TO SEARCH FOR NOVEL THERAPEUTIC TARGETS
Authors: Koga Tomoyuki , Miki Shunichiro , Skinner Kasey R , Venneti Sriram , Malicki Denise , Wechsler-Reya Robert , Gruener Robert , Huang R Stephanie , Chen Clark , Miller C Ryan , Furnari Frank 
Published: December 2020

Abstract
Diffuse midline glioma is the leading cause of brain tumor death among the pediatric population. Drugs that show notable promise in preclinical models inevitably fail to demonstrate efficacy in clinical trials, likely due to the inadequacy of preclinical models. We have recently proposed glioblastoma models derived from human induced pluripotent stem cells (hiPSCs) genetically engineered with different combinations of glioblastoma-associated genetic alterations as a platform to search for therapeutic targets. These glioblastoma avatars authentically recapitulated the different pathobiology of glioblastoma subtypes, depending on what genetic alterations to be introduced. To investigate the biology and to develop novel therapeutics for diffuse midline glioma with H3K27M mutation, we have established a novel model by introducing H3.3 K27M mutation together with one of the most common concurrent genetic alterations, TP53 R248Q mutation, into hiPSCs through CRISPR/Cas9 genome engineering. Orthotopic engraftment of the neural progenitor cells derived from these edited hiPSCs formed diffusely invasive brainstem tumors with histological features of the diffuse midline glioma. These tumor avatars presented a global reduction in H3K27me3 accompanied by the expression of H3K27M. Transcriptome analyses of these models revealed that these avatars with H3K27M cluster apart from the pediatric glioma samples without this particular mutation, and that they present signatures of oligodendroglial progenitor differentiation as discovered in patient samples with this mutation. Using these models faithfully recapitulating histology and pathobiology of the patient tumors, we have performed drug screening and confirmed that their sensitivity to known drugs, including an EZH2 inhibitor and histone deacetylase inhibitors. On these faithful human avatars of diffuse midline glioma with H3K27M, we have applied bioinformatics algorithms of drug sensitivity prediction aiming at developing novel therapeutics for this devastating pediatric glioma.
TMOD-08. PRIMARY AND RECURRENT GLIOMA PATIENT-DERIVED ORTHOTOPIC XENOGRAFTS (PDOX) REPRESENT RELEVANT PATIENT AVATARS FOR PRECISION MEDICINE
Authors: Golebiewska Anna , Hau Ann-Christin , Oudin Anais , Stieber Daniel , Yabo Yahaya A , Kwon Yong-Jun , Klink Barbara , Skupin Alexander , Hertel Frank , Bjerkvig Rolf , Niclou Simone P 
Published: December 2020

Abstract
Patient-derived cancer models are essential tools for studying tumor biology and for preclinical interventions. Although numerous clinical cancer trials are being conducted, many fail due to inappropriate selection of compounds at the preclinical stage. Therefore, better preclinical models are crucial for predicting successful clinical impact. Orthotropic patient-derived xenograft (PDOX) models are of particular importance for brain cancers, as they allow to better recapitulate the brain tumor environment and the blood brain barrier. We created a large collection of PDOXs from primary and recurrent gliomas with and without mutations in IDH1. PDOX models were based on 3D organoids, derived from mechanically minced patient material. Organoids were implanted in the brain of immunodeficient mice and further propagated by serial intracranial transplantations. High grade glioma PDOX models, starting with viable patient-derived organoids, have generally a high tumor take rate, a reproducible phenotype and tumor development time. PDOXs retain histopathological, genetic, epigenetic and transcriptomic features of patient tumors with no mouse-specific clonal evolution. Longitudinal PDOX models confirmed limited evolution of gliomas upon treatment observed in patient tumors. PDOX-derived standardized tumor organoid cultures enabled assessment of drug responses, which were validated in mice. PDOXs showed clinically relevant responses to Temozolomide and to targeted treatments such as EGFR and CDK4/6 inhibitors in (epi)genetically defined groups, according to MGMT promoter and EGFR/CDK status respectively. These data indicate that glioma PDOXs represent clinically relevant avatars for personalized treatment. The use of these models should lead to a more realistic evaluation of the efficacy of novel drugs, thereby increasing the success of clinical studies.
TMOD-10. EFFECT OF BRAIN TUMORIGENESIS ON CEREBRAL CORTICAL FUNCTIONAL CONNECTIVITY IN THE MOUSE
Authors: Cramer Samuel , Popa Laurentiu , Haley Samuel , Dhawan Sanjay , Carter Russell , Ning Jianfang , Aronson Justin , Kodandaramaiah Suhasa , Ebner Timothy , Chen Clark 
Published: December 2020

Abstract

INTRODUCTION
Neuro-cognitive decline is near universal in glioblastoma patients and negatively impacts the quality of life for afflicted patients. Yet, there is little information on longitudinal effects of brain tumor growth on cerebral cortical function and network connectivity.

OBJECTIVE
To address this knowledge gap, we examined in vivo Ca2+ imaging in a transgenic murine glioblastoma model.

METHODS
Mesoscopic Ca2+ imaging was performed after implant of GL261 glioblastoma cells into a transgenic mice strain (Thy1-GCaMP6f) that expresses the fast calcium indicator GCaMP6f in Layer II/III and Layer V pyramidal neurons. Independent component analysis (ICA), correlation matrix and graph theory approaches were used to assess changes in network connectivity.

RESULTS
ICA defined canonical cerebral network consisting of nodal convergence and connectivity between nodes. The overall network structure remained unaltered after tumor implant. A decrease in the strength of connectivity was observed immediately following tumor implant. This temporary suppression was followed by progressive, global increase in the strength of nodal connectivity (p &lt; 0.0001). By two weeks post-tumor implant, 50% of the nodes exhibited increased connectivity compared to baseline. Progressive activation of select nodes was also observed in the weeks following tumor implant (p &lt; 0.01). In aggregate, these results suggest that activation of select network nodes as well as enhanced connectivity as means to compensate for the deleterious effects of glioblastoma growth.

CONCLUSIONS
Our results indicate that focal brain tumor growth induces a reorganization of both local and remote cortical activity. The finding bears pertinence to the pathogenesis of neuro-cognitive decline and tumor-associated epilepsy.
TMOD-18. TARGETING THE PI3K/AKT PATHWAY IN MYCN AMPLIFIED HIGH GRADE GLIOMAS
Authors: Halligan Katharine , Stanton Ann-Catherine , Halbert Matthew , Golbourn Brian , Mack Stephen , Pollack Ian , Agnihotri Sameer 
Published: December 2020

Abstract
Pediatric glioblastoma (pGBM) are incurable brain tumors with overall poor prognosis and response to treatments due to molecular and epigenetic heterogeneity. In particular, the MYCN subtype of pGBM are a highly aggressive form of GBM with a dismal median survival of only 14 months. Furthermore, this subtype is enriched with loss of the tumor suppressor genes TP53 and PTEN, leading to aberrantly active PI3K-AKT signaling pathway and DNA-checkpoint abnormalities. Here, we report the generation of a novel syngeneic mouse model that recapitulates the features of the MYCN subtype of pGBM. We isolated Sox2-Cre neural stem cells from C57BL/6 mice and transduced inverted retroviral-cassettes of the murine Mycn oncogene simultaneously with shRNA targeting tumor suppressor genes p53 and Pten. Retroviral-cassettes are flanked by tandem LoxP sites arranged so that Cre recombinase expression inverts the cassettes in frame allowing for MYCN protein expression and loss of the P53/PTEN proteins. Transgene activation is accompanied with selectable cell surface markers and fluorescent tags enabling for fluorescent activated cell sorting (FACS) of the desired cell populations. Neural stem cells with MYCN protein expression and concurrent silencing of P53 and PTEN protein (NPP cells) result in significantly increased proliferation and activation of PI3K-AKT pathway as compared to control neural stem cells and have. Injection of NPP cells into the forebrain of immune competent C57BL/6 mice result in the formation of invasive high-grade gliomas with a lethal phenotype at ~50 days post injection. Using several next generation brain penetrant small molecule inhibitors of the PI3K-AKT pathway, we show inhibition of tumorigenesis in vitro. Moreover, we have identified several novel mechanisms of PI3KAKT treatment resistance and are currently identifying therapies that may overcome this resistance through RNA seq analysis. In summary, well defined genetic drivers of GBM can lead to informed mouse model generation to test promising therapies.
TMOD-20. A SWINE MODEL OF GLIOBLASTOMA INDUCED BY SOMATIC GENE MODIFICATION
Authors: Tschida Barbara , Duerre Dylan , Taisto Mandy , Watson Adrienne 
Published: December 2020

Abstract
Glioblastoma (GBM) is the most common and malignant primary brain tumor. Novel therapeutic development for GBM is needed since the standard of care universally fails to cure patients and the five-year survival rate remains below 10%. GBM therapeutic development is hampered by the lack of relevant large animal models for preclinical studies. To mitigate this problem, we are developing a model of GBM in outbred, immune-proficient swine which have comparable brain size and anatomy to humans. We developed methods for introducing genome engineering tools to minipig brain cells in vivo by direct injection of gene delivery reagents to the lateral ventricle. Using this technique, we have delivered a combination of expression vectors for oncogenes and targeted nucleases to disrupt tumor suppressor genes commonly altered in human GBM to alter six major human GBM-associated signaling pathways in a cohort of minipigs (Ras, Pi3k, p53, Rb/E2F, Pdgf, and the alternative lengthening of telomeres (ALT) pathways). These minipigs are being monitored for tumorigenesis using a secreted reporter, detectable through a simple luminescence-based blood test. Resulting tumors will be examined molecularly to detect the pathway-associated alterations in tumor tissue and determine the resemblance to human GBM. We hypothesize that this somatic cell gene-modification platform we have developed in the minipig will facilitate the efficient production of brain tumors that histologically and genetically resemble human GBM. It will allow the production of tumors that are genetically heterogeneous, of specified molecular subclasses, containing therapeutic targets of interest, and in the context of genetic backgrounds of interest. This minipig model of GBM will be applied towards preclinical therapeutic studies, imaging studies using human clinical grade equipment, and surgical technique development, to improve clinical trial success rates and patient outcomes. Funding for this study is provided by the National Institutes of Health through SBIR grant # 1R43CA235837-01A1.
TMOD-22. AKALUC BIOLUMINESCENCE OFFERS SUPERIOR SENSITIVITY TO TRACK IN VIVO GBM EXPANSION
Authors: Bozec Dominique , Sattiraju Anirudh , Bouras Alexandros , Raj Joe Gerald Jesu , Rivera Daniel , Huang Yong , Alves Chrystian Junqueira , Tejero Rut , Zou Hongyan , Hadjipanayis Constantinos , Friedel Roland H 
Published: December 2020

Abstract
Longitudinal tracking of tumor growth using non-invasive bioluminescence imaging (BLI) is a key approach for in vivo cancer studies, but the current method of firefly luciferase (Fluc) BLI has quantitative limitations, as it is only suited for detection of tumors of considerable sizes at advanced stage, typically in the order of &gt;105 cells. Recently, Akaluciferase (Akaluc) has been developed as an alternative BLI system that offers higher signal strength and better light penetration of tissue due to its red-shifted emission. Here, we established Akaluc BLI as a new sensitive method for in vivo tracking of glioblastoma (GBM) expansion in intracranial transplant models. In multiple GBM cell lines, including the frequently used U87MG and GL261, as well as patient-derived glioma stem cells (GSC), we demonstrate that Akaluc-expressing GBM cells produced more than 50-times brighter BLI signals in vitro and up to 100-fold higher signal intensities in vivo over Fluc-expressing counterparts. The higher sensitivity of Akaluc BLI permits early in vivo detection of intracranial GBM transplants starting as early as 4 hours after implantation and with as little as 5,000 transplanted GSC. We also reveal a prolonged engraftment period in intracranial GSC transplants before wide dissemination into host brain parenchyma. Akaluc BLI is also advantageous for longitudinal monitoring of therapeutic effects of chemoradiation for GBM and detection of early phase of tumor relapse. Thus, Akaluc BLI offers an important addition to the tool box for cancer research. SIGNIFICANCE: The high sensitivity of Akaluc bioluminescence is a significant improvement for the non-invasive tracking of tumors in preclinical cancer studies, including detection of small incipient tumors and micro-metastasis.