bluuebunny/crossref_metadata_2025_split huggingface dataset:
TMOD-11. APPLICATION OF A NOVEL TRANSGENIC AND SYNGENEIC MOUSE MODELS OF HUMAN CLASSICAL GLIOBLASTOMA FOR DRUG SCREENING AND PRE-CLINICAL TRIALS
Authors: Singh Olivia , Voisin Mathew , Li Mira , Karimi Shirin , Walia Kanwalpreet , Ali Hafsah , Nassiri Farshad , Suppiah Suganth , Aldape Kenneth , Wei Qingxia , Zadeh Gelareh 
Published: December 2020

Abstract
Glioblastoma multiforme (GBM) is the most common malignant brain tumor in adults with 1 year median survival. The classical subtype of GBM occurs in about 10% of GBM cases and has the worst clinical outcome. The most frequent genetic alteration associated with classical GBM is amplification in the epidermal growth factor receptor (EGFR) and homozygous deletion in CDKN2A (Cyclin Dependent Kinase Inhibitor 2A). We generated a transgenic mouse harboring EGFRvIII, a constitutively active mutant of EGFR, knock in and homozygous deletion in p19 ARF, an alternative spliced form of the CDKN2a gene, restricted to glial cells. Transgenic mice develop tumors as early as 1 month and 73% of mice die by 6 months of age. MRIs reveal that mice develop infiltrative tumor cells throughout the brain and craniospinal junction with some infiltration within the leptomeninges that can result in hydrocephalus. Histology shows that 72% of tumors are high grade gliomas and some tumors demonstrate classical histological features of human GBM such as pseudopallisading necrosis, hyper vascularity and cellular atypia. We generated primary cell lines from transgenic mice that retained EGFRVIII expression and P19 ARF deletion and formed allografts in syngeneic mouse brains. Epigenetic modifications are considered a key mechanism in GBM development. We have therefore evaluated the efficacy of a panel of 42 compounds that target various epigenetic proteins including the readers, writers, and editors of several histone marks available from the Structural Genomics Consortium in primary cell lines derived from our mouse model. The primary cell lines were exposed to epigenetic drugs showing different responses to the same epigenetic modifiers. Key candidate drugs will further be tested pre-clinically in our syngeneic mouse model. In summary, we developed a novel transgenic and syngeneic mouse model for human classical GBM that can be used for drug screening and pre-clinical trials.
TMOD-15. EFFICACY OF THE MDM2 INHIBITOR KRT-232 IN GLIOBLASTOMA PATIENT-DERIVED XENOGRAFT MODELS
Authors: Vaubel Rachael , Mladek Ann , Zhao Yu , Gupta Shiv K , Kim Minjee , Mohammad Afroz S , Bakken Katrina , He Lihong , Hu Zeng , Burgenske Danielle M , Carlson Brett L , Elmquist William F , Sarkaria Jann 
Published: December 2020

Abstract
Non-genotoxic reactivation of p53 by MDM2 inhibitors represents a promising therapeutic strategy for tumors with wild-type TP53, particularly tumors harboring MDM2 amplification. MDM2 controls p53 levels by targeting it for degradation, while disruption of the MDM2-p53 interaction causes rapid accumulation of p53 and activation of the p53 pathway. We examined the efficacy of the small molecule MDM2 inhibitor KRT-232, alone and in combination with radiation therapy (RT), in MDM2-amplified and/or p53 wildtype patient-derived xenograft (PDX) models of glioblastoma in vitro and in vivo. In vitro, glioblastoma PDX explant cultures showed sensitivity to KRT-232, both tumors with MDM2 amplification (GBM108 and G148) and non-amplified but TP53-wildtype lines (GBM10, GBM14, and GBM39), with IC50s ranging from 300-800 nM in FBS culture conditions. A TP53 p.F270C mutant PDX (GBM43) was inherently resistant, with IC50 &gt;3000 nM. In the MDM2-amplified GBM108 line, KRT-232 led to a robust (5-6 fold) induction of p53-target genes p21, PUMA, and NOXA, with initiation of both apoptosis and senescence. Expression of p21 and PUMA was greater with KRT-232 in combination with RT (25-35 fold induction), while stable knock-down of p53 in GBM108 led to complete resistance to KRT-232. In contrast, GBM10 showed lower induction of p21 and PUMA (2-3 fold) and was more resistant to KRT-232. In an orthotopic GBM108 xenograft model, treatment with KRT-232 +/- RT for one week extended survival from 22 days (placebo) to 46 days (KRT-232 alone); combination KRT-232 + RT further extended survival (77 days) over RT alone (31 days). KRT-232 is an effective treatment in a subset of glioblastoma pre-clinical models alone and in combination with RT. Further studies are underway to understand the mechanisms conferring innate sensitivity or resistance to KRT-232.
TMOD-16. A NOVEL ADENOVIRAL-PERMISSIVE, IMMUNOCOMPETENT HAMSTER GLIOMA MODEL TO EVALUATE ONCOLYTIC ADENOVIRAL THERAPY
Authors: Phillips Lynette , Gumin Joy , Li Shoudong , Daou Marc , Ledbetter Daniel , Hossain Anwar , Kerrigan Brittany Parker , Gomez-Manzano Candelaria , Fueyo Juan , Lang Frederick 
Published: December 2020

Abstract
Oncolytic adenoviruses, including Delta-24-RGD, target tumors by direct tumor cell oncolysis and by activation of an anti-tumor immune response. Due to the species selectivity of oncolytic adenoviruses, there is currently no single preclinical animal model of glioma that supports viral replication, tumor oncolysis, and virus-mediated immune responses. To address this gap, we took advantage of the Syrian hamster to develop the first glioma model that is both adenovirus replication-permissive and immunocompetent. Hamster glioma stem-like cells (GSCs), transformed by forced expression of hTERT, SV40 large T antigen, and h-RasV12, reproducibly form intracranial tumors in hamsters. In vitro, electron microscopy and cytopathic effect assays demonstrated that hamster GSCs supported viral replication and were susceptible to Delta-24-RGD-mediated cell death. In vivo, hamster GSCs consistently developed into highly proliferative tumors resembling high-grade gliomas. Following intratumoral delivery of Delta-24-RGD, immunohistochemistry for viral proteins demonstrated viral infectivity and replication in hamster gliomas. Flow cytometry revealed increased T cell infiltration in Delta-24-RGD-infected tumors. Delta-24-RGD treatment of tumor-bearing hamsters led to significantly increased survival compared with hamsters treated with PBS. Using this model, we evaluated the effects of corticosteroid-mediated immunosuppression on Delta-24-RGD efficacy. Dexamethasone treatment significantly decreased peripheral blood lymphocytes, decreased tumor-infiltrating lymphocytes, and suppressed the levels of serum anti-adenovirus antibodies. Dexamethasone reduced the number of long-term survivors and decreased the median survival (50 days for Delta-24-RGD + dexamethasone vs undetermined for Delta-24-RGD alone). In summary, we have developed the first adenovirus-permissive, immunocompetent hamster glioma model, addressing a critical need for a model in which to study the role of direct oncolysis in driving immune mediated viral clearance versus driving an antiglioma immune response. Understanding these mechanisms is critical to optimizing the success of oncolytic adenoviral therapy in the clinic.
TMOD-17. ONCOLYTIC POLIOVIRUS AS A PROBE FOR MECHANISMS OF IMMUNE RESISTANCE IN GLIOBLASTOMA
Authors: Yang Yuanfan , Brown Michael , Gromeier Matthias , Bigner Darell 
Published: December 2020

Abstract
Glioblastoma is an immunologically cold tumor that employs multiple resistance mechanisms to escape activation of both innate and adaptive immunity. Transient immune activation and responses induced by immunotherapies in glioblastoma are almost always suppressed by potent intrinsic and extrinsic resistance mechanisms, limiting therapeutic efficacy. PVSRIPO is a recombinant poliovirus/rhinovirus chimera that elicits robust innate immune activation through infecting and lysing glioblastoma cells expressing the human poliovirus receptor (CD155), and through sublethal infection of tumor associated macrophages, setting the stage for lingering viral replication. We have constructed a pathological model using murine CT2ACD155 intracranial tumors stereotactically infused with a single dose of PVSRIPO (5×107 pfu) or mock control to study the response of glioblastoma in an immune competent in vivo tumor microenvironment. Tumor bearing brains were harvested before therapy and on days 2, 4, 6, 9, 12 post therapy for histology. On day 4 post therapy, histopathology showed &gt; 90% shrinkage of intracranial tumor diameter (n= 6/6). Residual tumor is surrounded by a necrotic rim on histology with profound infiltration of F4/80+ macrophages and substantially reduced expression of Ki-67 on IHC compared to controls. Other markers including CD3, CD8 and Cleaved-Caspase 3 showed no difference in tumors of both groups. Interestingly, most residual tumor progressed on day 6 post therapy and caught up with the size of control tumor by day 9. Long-term remission of tumor occurred in only 10% of mice. This model is valuable in studying the mechanisms of intrinsic resistance and the timeline of resistance to develop in order to obtain more durable immunotherapy responses in glioblastoma. Future steps are to track inflammation induced by viral infection by RNAseq, and to find potential therapeutic interventions (including blocking PD1:PD-L1 axis) to mitigate therapy resistance in this preclinical model.
TMOD-25. IN VIVO MODEL OF TREATMENT-RESISTANT GLIOBLASTOMA HIGHLIGHTS SEX DIFFERENCES IN SURVIVAL
Authors: Al-Gizawiy Mona , Wujek Robert , Prah Melissa , Molino Salvatore , Chitambar Christopher , Schmainda Kathleen 
Published: December 2020

Abstract

BACKGROUND
Sex differences independent from acute hormone action are evident in the incidence and tumorigenesis of several cancers, including glioblastoma (GBM). Malignant brain tumors with mesenchymal, proneural, and neural GBM subtypes occur twice as frequently in males than in females, implying a molecular basis for the sex disparities observed. Accordingly, response to therapy and overall survival, may also differ between male and female GBM patients. Further elucidation of these differences would benefit from a robust preclinical testing system, such as the one described here.

METHODS
Adult (U87-MG) GBM cells were exposed to a total radiation dose of 10 Gy, effecting an epithelial to mesenchymal transition. The resultant irradiated U87-10Gy cells were tested for cell viability and allowed to reach confluence prior to stereotactic implantation into the right striatum of male and female athymic rats. In vivo advanced MR imaging at 9.4T was carried out weekly starting two weeks after implantation. Advanced MRI parameters were processed for enhancing tumor ROIs in OsiriX 8.5.1 (lite) with Imaging Biometrics™ Software (IQ-AI, Ltd.).

RESULTS
Tumor take was 90% in males and 60% in females, indicating an ‘incidence’ ratio of 1.5. Overall survival was significantly higher in females (median = 48, range = 40-72 days) than in males (median = 28, range = 27-30 days) (p = 0.024). Immunohistochemical and imaging analyses are pending and will be discussed.

CONCLUSION
The outcomes noted in this pilot study mirror incidence and survival outcomes noted in GBM patients undergoing standard care. Our model of treatment-resistant glioma provides a robust testing system to study underlying sex differences in GBM biology and treatment response in parallel analyses of male and female data.
TMOD-28. NEW APPROACHES FOR ELUCIDATING MEDULLOBLASTOMA DEVELOPMENT VIA HINDBRAIN BLASTOCYST COMPLEMENTATION
Authors: Schmidt Christin , Carlson Annika , Weiss William , Schwer Bjoern 
Published: December 2020

Abstract
Understanding the etiology of brain cancers requires elucidation of developmental origins, genetic drivers, and the tumor microenvironment. This requires reliable in vivo approaches, which are currently lacking. Current in vivo models for pediatric brain tumors rely on generation of xenografts or allografts in immunodeficient mice or generation of transgenic mice. These approaches have severe limitations, including lack of a functional immune system, a restricted developmental time window defined by the cell of origin, or time-consuming workflows for the generation of transgenic mice. We recently developed neural blastocyst complementation (NBC), an organogenesis approach for the forebrain. NBC involves injection of donor mouse embryonic stem cells (ESC) into genetically-engineered blastocysts that are programmed to ablate dorsal telencephalic progenitors. This results in the formation of a donor-cell derived, intact forebrain. Based on this general approach, we are developing an in vivo platform for studies of brain cancer. We will report on our efforts and progress toward the generation of an organogenesis approach for the hindbrain and related studies that aim to define developmental origins and drivers of medulloblastoma.
TMOD-33. THE ROLE OF BAFF-R SIGNALING IN THE GROWTH OF PRIMARY CENTRAL NERVOUS SYSTEM LYMPHOMA
Authors: Mulazzani Matthias , Zhou Xíaolan , Zhang Wenlong , Straube Andreas , von Baumgarten Louisa 
Published: December 2020

Abstract
Primary CNS lymphoma (PCNSL) is an aggressive brain tumor. Despite improvements in therapeutic algorithms, long-term survival remains rare, illustrating an urgent need for novel therapeutic targets. BAFF-R is a pro-survival receptor expressed on most malignant B cells, including PCNSL. To date, its role in PCNSL growth remains elusive. Here, we created a BAFF-R knockout lymphoma cell line (BAFF-R-KO) using CRISPR-Cas9. In serum-starved conditions, BAFF-R-KO cells exhibit decreased viability in vitro compared to BAFF-R+ cells. Combining an orthotopic mouse model of PCNSL with chronic cranial windows and intravital microscopy, we demonstrate a significant delay in tumor growth in mice inoculated with BAFF-R-KO cells compared to BAFF-R+ PCNSL. Additionally, median survival of BAFF-R-KO mice was significantly prolonged. Altogether, our results indicate a potential of BAFF-R as a novel treatment target for PCNSL.
ATRT-16. MODELLING ATRT THROUGH SWI/SNF COMPLEX DEFICIENCY IN GENETICALLY-ENGINEERED MOUSE MODELS
Authors: Bondoc Andrew , Golbourn Brian , Smith Christian , Huang Annie , Rutka James 
Published: December 2020

Abstract
Atypical Teratoid/Rhabdoid Tumours (ATRT) are highly malignant neoplasms arising primarily in the CNS of children. They are defined by loss of function mutations in smarcb1, a gene serving a vital role in neurogenesis and differentiation. In order to recapitulate ATRT in the mouse, we used a Cre-Lox recombination system to conditionally knockout smarcb1 in specific cell compartments. Loss of smarcb1 in BLBP-expressing cells of the developing brain led to severe neurologic defects. Mice exhibited seizures, ataxia, and median 12-day survival. Histological analysis revealed severe thinning of the cerebral cortex and cerebellum. Temporally-targeted smarcb1 loss in BLBP/Nestin-expressing embryonic compartments did not result in tumour formation. Similarly, BLBP-expressing, smarcb1-deficient neural stem/progenitor cells (NSC/NPCs) were isolated and allografted but did not form tumours. These cells demonstrated decreased proliferation, higher apoptosis, and upregulation of p53, CDKN1A, and CDKN2A. In contrast, ubiquitous smarcb1 loss at the earlier embryonic day 6.5 produced widespread tumorigenicity in the forebrain, hindbrain, skullbase, and spine; each with unique phenotypes, survival, and morphology. We employed a clinically-relevant Nanostring gene-panel screen to stratify tumours into genetically distinct subgroups. Our findings indicate that smarcb1 plays an important role in CNS development. Loss of smarcb1 in NSC/NPCs is lethal, and its developmental context influences cell fate. Targeted smarcb1 loss likely plays a tumorigenic role at an earlier developmental stage than previously determined, in a diverse array of primitive stem cells. These data support the generation of a murine ATRT model capable of producing distinct tumour entities that recapitulate the human disease.
ATRT-17. TARGETING GLUTAMINE METABOLISM LOWERS METHYLATION POTENCIALS IN AT/RT AND SYNERGIZE WITH TAZEMETOSTAT
Authors: Nakata Satoshi , Wang Sabrina , Alt Jesse , Slusher Barbara , Eberhart Charles , Raabe Eric , Rubens Jeffrey 
Published: December 2020

Abstract
Atypical teratoid/rhabdoid tumors (AT/RT) have a single recurring genetic mutation in SMARCB1. This deletion leads to an abnormal SWI/SNF chromatin remodeling complex and the constitutive activation of EZH2. S-adenosyl-L-methionine (SAM) donates a methyl group to EZH2 which then methylates DNA and histones leading to the abnormal gene expression responsible for AT/RT’s aggressive phenotype. We have previously shown that glutamine metabolic inhibition with 6-diazo-5-oxo-L-norleucine (DON) confers a survival advantage in AT/RT. In this study, we identified with ultra-high performance liquid chromatography mass spectrometry that DON treatment lowered the methylation potential in AT/RT (Decreased SAM:SAH ratio, t-test in 5 AT/RT human-derived cell models comparing DON treatment to DMSO control, p&lt;0.05). AT/RT cell lines grown in glutamine deplete media compared to normal growth conditions also had a reduced methylation potential (decreased SAM:SAH, t-test, p&lt;0.05). DON treatment over 5 days decreased histone methylation (as determined by western blot for H3K27me3). Tazemetostat is a small molecule inhibitor that blocks the SAM methyl donor site on EZH2. We find that DON combines synergistically with Tazemetostat to slow AT/RT cell growth (MTS assay, p&lt;0.01 t-test; MUSE viability assay, p&lt;0.01 ANOVA) and enhances cytotoxicity (MUSE Annexin-V, p&lt;0.01 by ANOVA). Synergies were especially pronounced at low concentrations of Tazemetostat which is significant given that Tazemetostat’s efficacy in AT/RT has been limited by poor CNS penetration. These studies identify a novel treatment strategy that has potential to improve survival in AT/RT.
ATRT-19. EPIGENETIC REPROGRAMMING LEADS TO INNATE IMMUNE PATHWAY ACTIVATION IN AT/RT
Authors: Hariharan Seethalakshmi , Kilic Cem , Bowie Michelle , Reitman Zachary , Ashley David 
Published: December 2020

Abstract

BACKGROUND
Atypical teratoid/rhabdoid tumors (AT/RT) are highly aggressive brain tumors affecting early childhood and are characterized by bi-allelic inactivation of the SMARCB1 gene. Though patients benefit from multimodal therapy, there is no improvement in overall survival necessitating exploration of alternative approaches including innate-based immune therapy and epigenetic therapy, which have shown promise in treating adult brain tumors and other cancers. Though reconstitution of SMARCB1 in SMARCB1-deficient cells leads to activation of interferon-stimulated genes, the role of innate immune signaling has not been investigated in AT/RTs.

METHODS
Our data from a panel of AT/RT cell lines indicates loss of expression of key innate signaling components, like RIG-I, MDA-5, cGAS and STING that are required for sensing extracellular dsRNA and dsDNA. These cell lines also do not respond to dsDNA-based or dsRNA-based innate agonists. However, co-treatment of the BT-16 cell line with two epigenetic drugs, panobinostat and 5-azacytidine leads to re-expression of STING and RIG-I. Panobinostat/5-azacytidine co-treatment followed by either genomic DNA (dsDNA agonist) or poly(I:C) (dsRNA agonist) treatment results in induction of innate responses, measured by STAT1 phosphorylation and production of ISG-15 and IFIT-1.

CONCLUSION
Our data suggests that AT/RT cell lines are unresponsive to innate agonists possibly due to the loss of expression of key innate immune components. However, these pathways can be reactivated by epigenetic drugs and further potentiated by dsDNA/dsRNA-based innate agonists. Combined epigenetic reprogramming and innate pathway stimulation may serve as a potential therapy option for treating AT/RT.
ATRT-22. HIGH-THROUGHPUT DRUG SCREENING OF FDA-APPROVED CANCER DRUGS REVEALS POTENTIAL THERAPEUTIC APPROACHES FOR ATYPICAL TERATOID RHABDOID TUMOUR
Authors: Chong Wai Chin , Zhukova Nataliya , Wood Paul , Downie Peter A , Cain Jason E 
Published: December 2020

Abstract
Atypical teratoid/rhabdoid tumors (ATRT), are the most common brain tumor in children under the age of 1 year with an overall survival of ~17%. Like extracranial rhabdoid tumors, ATRT is exclusively characterized by bi-allelic loss of SMARCB1, a critical subunit of the SWI/SNF chromatin remodeling complex, implicating epigenetic deregulation in the pathogenesis of disease. We have previously shown the ability of the histone deacetylase inhibitor, panobinostat, to mimic SMARCB1-mediated SWI/SNF functions in extracranial rhabdoid tumors to inhibit tumor growth by driving multi-lineage differentiation in vitro and in vivo. Whether this also applies to ATRT is unknown. Using a panel of human-derived ATRT cell lines, representing defined molecular subgroups, we have shown that prolonged treatment with panobinostat at nanomolar concentrations results in markedly reduced clonogenicity, and increased senescence, preceded by increased H3K27 acetylation, decreased H3K27 trimethylation and EZH2 expression. To determine potentially synergistic therapies, we performed high-throughput drug screening of 622 compounds already in advanced clinical trials or FDA-approved for other indications, across our panel of ATRT models and identified 30 common compounds, which decrease cell viability by &gt;50%, with no effect on neural stem cell controls and 12 compounds which demonstrated subgroup specificity, highlighting the necessity to consider therapies in the molecular context. In addition to HDACi, consistent with our panobinostat in vitro findings, inhibitors of CDK, survivin and PI3K were the top hits. In vitro and in vivo validation of these compounds alone, and in combination with panobinostat is ongoing.
ATRT-26. META-ANALYSIS OF TREATMENT MODALITIES IN METASTATIC ATYPICAL TERATOID/RHABDOID TUMORS IN CHILDREN
Authors: Underiner Reena M , Eltobgy Mostafa , Stanek Joseph R , Finlay Jonathan L , AbdelBaki Mohamed S 
Published: December 2020

Abstract

BACKGROUND
Metastatic atypical teratoid/rhabdoid tumors (AT/RT) are aggressive central nervous system tumors that present during infancy and are associated with dismal outcomes. Patients receive multimodal treatment including surgical resection, systemic chemotherapy and one or more of intrathecal chemotherapy (IT), marrow-ablative chemotherapy with autologous hematopoietic cell rescue (AuHCR) and radiation therapy (XRT). While data regarding treatment modalities for AT/RT patients exist, no comprehensive data have been published regarding the metastatic patient population.

METHODS
We performed a meta-analysis of 1,578 articles published through September 2018, including 44 studies with a total of 123 subjects. Additionally, seven patients were incorporated through chart review of patients treated at Nationwide Children’s Hospital.

RESULTS
Analysis of 130 patients revealed a 3-year overall survival (OS) of 25%. Age at diagnosis had a significant impact on survival (p=0.0355); 3-year OS for infants &lt; 18 months was 21%; 18–36 months was 26%; and &gt; 36 months was 36%. Location of the primary tumor, metastatic stage and extent of surgical resection did not have significant impact on OS. On univariate analysis, XRT (p&lt;0.0001), IT (p=0.01) and AuHCR (p&lt;0.0001) were found to significantly improve survival. The most substantial effect was noted in patients who received AuHCR (3-year OS of 60% versus 9% in those who did not). On multivariable analysis XRT (p=0.0006), IT (p=0.0124) and AuHCR (p&lt;0.0001) were independently associated with reduced risk of death.