bluuebunny/crossref_metadata_2025 huggingface dataset:
EPCO-14. DECIPHERING DIFFERENTIATION HIERARCHIES, HERITABILITY AND PLASTICITY IN HUMAN GLIOMAS VIA SINGLE-CELL MULTI-OMICS
Authors: Gaiti Federico , Chaligne Ronan , Silverbush Dana , Schiffman Joshua , Weisman Hannah , Kluegel lloyd , Gritsch Simon , Deochand Sunil , Richman Alyssa , Klughammer Johanna , Biancalani Tommaso , Muus Christoph , Sheridan Caroline , Alonso Alicia , Izzo Franco , Rozenblatt-Rosen Orit , Regev Aviv , Suva Mario , Landau Dan
Published: December 2020

Human diffuse gliomas are incurable malignancies, where cellular state diversity fuels tumor progression and resistance to therapy. Single-cell RNA-sequencing (scRNAseq) studies recently charted the cellular states of the two major categories of human gliomas, IDH-mutant gliomas (IDH-MUT) and IDH-wildtype glioblastoma (GBM), showing that malignant cells partly recapitulate neurodevelopmental trajectories. This raises the central questions of how cell states are encoded epigenetically and whether unidirectional hierarchies or more plastic state transitions govern glioma cellular architectures. To address these questions, we generated multi-omics single-cell profiling, integrating DNA methylation (DNAme), transcriptome and genotyping of 1,728 cells from 11 GBM and IDH-MUT primary patient samples. Direct comparison of the methylomes of distinct glioma cell states revealed Polycomb repressive complex 2 (PRC2) targets DNAme as a key switch in the differentiation of malignant GBM cells. In contrast, dissecting aberrant circuits of hyper-methylation and gene expression in IDH-MUT gliomas, we observed a decoupling of the promoter methylation-expression relationship, with disruption of CTCF insulation and enhancer vulnerability which increases with cellular differentiation. To define cell state transition dynamics directly in patient samples, we generated high-resolution lineage histories of glioma cells using heritable DNAme changes, and projected the scRNAseq-derived cell states onto the lineage trees. This analysis demonstrated that cell states are heritable across malignant gliomas and, while in IDH-MUT differentiation far outpaces de-differentiation, GBM harbors a higher degree of cell state plasticity allowing reversion of GBM cells from a differentiated to a stem-like state. Overall, our work provides detailed insights into gliomagenesis, dissecting the epigenetic encoding, regulatory programs, and dynamics of the cellular states that drive human gliomas. Importantly, it also carries significant translational implication, as the high degree of de-differentiation in GBM challenges the paradigm of therapeutically targeting glioma stem-like cells to deprive tumors of their ability to regenerate.
EPCO-26. PROJECT HOPE: “PEDIATRIC AND AYA HIGH-GRADE GLIOMA OMICS PROJECT”- A LONGITUDINAL MOLECULAR LANDSCAPE OF HIGH-GRADE GLIOMAS RESOLVED AT SINGLE-CELL LEVEL
Authors: Jiang Li , Hack Olivia , Babikir Husam , Shamardani Karin , Liu Ilon , Shaw McKenzie , Cunliffe-Koehler Kennedy , Resnick Adam , Prados Michael , Monje Michelle , Diaz Aaron , Filbin Mariella
Published: December 2020

High-grade gliomas (HGG) are among the most prevalent and fatal cancers in pediatric, adolescent, and young adult (AYA) patients. Especially understudied are older children and young adults, aged 16–39 years. Previously, we profiled primary pediatric HGGs through single-cell transcriptomics and identified the genetic, epigenetic and developmental programs that drive their malignant progression. However, the questions of how these programs compare to those in older HGG patients, what the mechanisms are by which these tumors ultimately evolve to drive recurrence and treatment resistance, and how distinct tumor cell subpopulations bidirectionally communicate with their microenvironment remain to be elucidated. In order to investigate these questions, we use single-nucleus RNA sequencing to compare 11 paired, matched high-grade gliomas at diagnosis and recurrence and 15 additional H3K27M primary and recurrent DMG samples in pediatric and AYA patients. In all tumors, we find both undifferentiated and differentiated tumor cells recapitulating distinct glial lineages, as well as diverse microenvironmental cell populations. When longitudinally comparing this tumor architecture within matched pairs, we find substantial differences in transcriptional program expressions. In particular, recurrent samples showed a higher proportion of cells expressing heat- shock proteins (HSPs) and a novel cancer cell program characterized by synaptic formation and neurotransmitter secretory processes, suggesting tumor progression- and treatment-related shifts. Ongoing sequencing and analysis will allow for unprecedented insight into the evolutionary dynamics of pediatric and AYA high-grade gliomas as well as delineate differences in the biology of DMGs occurring in different age groups. This multi-institutional project was funded by the National Institute of Health.
EPCO-29. EPIGENOMICS OF THE GLIOMA LONGITUDINAL ANALYSIS (GLASS) CONSORTIUM
Authors: Sabedot Thais , Wells Michael , Datta Indrani , Malta Tathiane , Castro Ana Valeria ,   GLASS Consortium, Poisson Laila M , Verhaak Roel , Iavarone Antonio , Noushmehr Houtan
Published: December 2020

Adult diffuse gliomas are central nervous system (CNS) tumors that arise from the malignant transformation of glial cells. Nearly all gliomas will recur despite standard treatment however, current histopathological grading fails to predict which of them will relapse and/or progress. The Glioma Longitudinal AnalySiS (GLASS) consortium is a large-scale collaboration that aims to investigate the molecular profiling of matched primary and recurrent glioma samples from multiple institutions in order to better understand the dynamic evolution of these tumors. At this time, the cohort comprises 946 samples across 11 institutions and among those, 864 have DNA methylation data available. The current molecular classification based on 7 subtypes published by TCGA in 2016 was applied to the dataset. Among the IDH wildtype tumors, 33% (16/49) of the patients showed a change of subtype upon recurrence, whereas most of them (9/16) were Classic-like at the primary stage but changed to either Mesenchymal-like or PA-like at the recurrent level. Among the IDH mutant tumors, 15% (22/142) showed a change of subtype at recurrent stage, in which 16 out of 22 progressed from G-CIMP-high to G-CIMP-low. Although some tumors progressed to a different subtype upon recurrence, an unsupervised analysis showed that the samples tend to cluster by patient instead of by subtype. By estimating the copy number alterations of these tumors using DNA methylation, the overall copy number profile of the recurrent samples remains similar to their primary counterpart. From this initial analysis using epigenomic data, we were able to characterize some aspects of glioma evolution and how the DNA methylation is associated with the progression of these tumors to different subtypes. These findings corroborate the importance of epigenetics in gliomas and can potentially lead to the identification of new biomarkers that can reflect tumor burden and predict its development.
EPCO-31. EPIGENOMIC INTRATUMORAL HETEROGENEITY OF GLIOBLASTOMA IN THREE-DIMENSIONAL SPACE
Authors: Mathur Radhika , Iyyanki Sriranga , Hilz Stephanie , Hong Chibo , Phillips Joanna , Chang Susan , Yue Feng , Costello Joseph
Published: December 2020

Treatment failure in glioblastoma is often attributed to intratumoral heterogeneity (ITH), which fosters tumor evolution and generation of therapy-resistant clones. While ITH in glioblastoma has been well-characterized at the genomic and transcriptomic levels, the extent of ITH at the epigenomic level and its biological and clinical significance are not well understood. In collaboration with neurosurgeons, neuropathologists, and biomedical imaging experts, we have established a novel topographical approach towards characterizing epigenomic ITH in three-dimensional (3-D) space. We utilize pre-operative MRI scans to define tumor volume and then utilize 3-D surgical neuro-navigation to intra-operatively acquire 10+ samples representing maximal anatomical diversity. The precise spatial location of each sample is mapped by 3-D coordinates, enabling tumors to be visualized in 360-degrees and providing unprecedented insight into their spatial organization and patterning. For each sample, we conduct assay for transposase-accessible chromatin using sequencing (ATAC-Seq), which provides information on the genomic locations of open chromatin, DNA-binding proteins, and individual nucleosomes at nucleotide resolution. We additionally conduct whole-exome sequencing and RNA sequencing for each spatially mapped sample. Integrative analysis of these datasets reveals distinct patterns of chromatin accessibility within glioblastoma tumors, as well as their associations with genetically defined clonal expansions. Our analysis further reveals how differences in chromatin accessibility within tumors reflect underlying transcription factor activity at gene regulatory elements, including both promoters and enhancers, and drive expression of particular gene expression sets, including neuronal and immune programs. Collectively, this work provides the most comprehensive characterization of epigenomic ITH to date, establishing its importance for driving tumor evolution and therapy resistance in glioblastoma. As a resource for further investigation, we have provided our datasets on an interactive data sharing platform – The 3D Glioma Atlas – that enables 360-degree visualization of both genomic and epigenomic ITH.
EPCO-32. AN EPIGENETIC SINGLE-CELL ATLAS OF IDH-MUTANT GLIOMA REVEALS THE ROLE OF ATRX IN SHAPING TUMOR COMPOSITION
Authors: Babikir Husam , Wang Lin , Shamardani Karin , Sudhir Sweta , Kohanbash Gary , Aghi Manish , Philips Joanna , Diaz Aaron
Published: December 2020

Recent single-cell RNA-sequencing studies have identified a hierarchy of cell types that is common to all isocitrate dehydrogenase (IDH) -mutant gliomas. This finding is somewhat paradoxical since the genetic differences between IDH-mutant astrocytomas and IDH-mutant oligodendrogliomas are prognostic, predictive of therapeutic response, and correlated with differences in immune infiltrates. To integrate these disparate findings, we constructed a single-cell atlas of 28 human IDH-mutant primary untreated grade-II/III gliomas. All specimens were profiled by single-cell assay for transposase-accessible chromatin, with additional cohorts profiled via single-cell RNA-sequencing and single-cell spatial proteomics. We determined the cell-type specific differences between IDH-mutant gliomas in transcription-factor utilization, associated targeting and cis-regulatory grammars. To elucidate the role of the chromatin remodeler ATRX (inactivated in over 86% of IDH-mutant astrocytomas) in shaping observed differences in open chromatin, we knocked out ATRX in an immunocompetent model of IDH-mutant glioma and subjected murine tumors to single-cell profiling. We found: 1. ATRX-deficient, IDH-mutant human and murine gliomas both upregulate an astrocytic regulatory program driven by Nuclear Factor I genes and downregulate an oligodendrocytic program driven by basic helix-loop-helix transcription factors. 2. Both human and mouse ATRX-deficient, IDH-mutant gliomas up-regulate genes that promote myeloid-cell chemotaxis and both have significantly higher percentages of myeloid-derived immune-suppressive cells than controls; 3. A transcription-factor program is conserved between human and murine ATRX-deficient tumors that shapes glial identity and promotes local immunosuppression. These studies elucidate how IDH-mutant gliomas from different subtypes can have distinct cellular morphologies and tumor micronenvironments despite a common lineage hierarchy.
EPCO-33. MULTI-OMICS ANALYSIS REVEALS SUBTYPE-SPECIFIC ENHANCER-TARGET NETWORKS AND TUMOR CELL OF ORIGIN IN GROUPS 3 AND 4 MEDULLOBLASTOMA
Authors: You Zhen , Huang L Frank
Published: December 2020

Medulloblastoma (MB), one of the most common malignant childhood brain cancer, consists of heterogeneous subgroup of cerebellar tumors. Four molecular subgroups are classified, of which Groups3 and 4 are poorly characterized. Additionally, MB subtype tumorigenesis and cellular composition remain elusive. Here, we combined multi-omics data, including bulk ChIP-Seq, RNA-Seq data, and scRNA-Seq from medulloblastoma patients with primary tumors, and integrated with whole-genome sequencing data, to address the tumors development and cellular heterogeneity in MB subgroups. First, we identified subgroup-specific enhancers and their targets based on the differential accessibility of H3K27ac signatures and further acquired subgroup-enriched transcription factors. Three distinct transcriptional signatures were extracted from RNA-seq of groups 3 and 4 MB respectively using non-negative matrix factorization and consensus clustering. To illustrate the subtype-specific expressed genes in those subtypes, we applied the Shannon entropy approach to discover genes and lncRNAs that are exclusively active or quiescent in a certain subtype. Single-cell transcriptome analysis demonstrated that SHH subgroup mostly consisted of mature and proliferating GNPs; Group3 tumors contained divergent cells, e.g. GNPs, UBCs, and excitatory CN; while Group4 subgroup derived mainly from UBCs and GluCN. Moreover, deconvolution of bulk RNA-Seq revealed that Group3 subtype1 mostly resembled mitosis and mature GNPs; and subtype2 resembled mitosis GNPs, excitatory CN, and OPCs; while subtype3 resembled UBCs, mitosis and mature GNPs, indicating the cellular origin difference within Group3 tumorigenesis. Genes and lncRNAs specifically expressed in subtype and cell type linked to the subtype MB tumor development and intertumoral cellularity. Taken together, these data enabled us to constructed novel enhancers-target networks that give rise to MB subtyping and cellular heterogeneity and permits the discovery of novel driver genes and pathways in medulloblastoma.
EPCO-38. PRIMARY CNS DIFFUSE LARGE B-CELL LYMPHOMA WITH CIC-REARRANGEMENT IDENTIFYING FROM PAN-CANCER PATIENTS EXCLUDING SARCOMAS
Authors: Cai Linbo , Shan Changguo , Hong Weiping , Wang Hui , Ai Ruyu , Song Chao , Qin Huijuan , Zhang Xing , Sun Jiaxing , Ji Yuhang , Yang Xueyu , Ren Yong
Published: December 2020

BACKGROUND

CIC-rearrangements most commonly occur in patients with Ewing-like sarcomas, an emerging class of round cell sarcomas. CIC sarcoma has considered being a new entity in CNS tumors by cIMPACT-NOW conform classification of tumors of soft tissue and bone. However, not all patients harbor CIC fusion are sarcoma cases. Herein, we firstly report a case of primary CNS diffuse large B-cell lymphoma (DLBCL) harboring CIC-rearrangement with a novel partner.

METHODS

CIC fusions were screened in the tumor tissue or peripheral blood from 3,961 cases with different types of cancer excluded patients with sarcomas. Comprehensive genomic profiling with a 539 cancer-related genes panel was administrated based on next generation sequencing (NGS) which is adept in finding novel fusion mutations. The pathology diagnosis of every case was confirmed via hematoxylin and eosin (H&E) stained.

RESULTS

Among the whole 3,961 cases, 3 CIC-rearrangements were observed. One case has been reported yet, one was a patient with lung adenocarcinoma, the last one was a patient harboring POU2F2 (Exon5) -CIC (Exon 11) with CNS arisen tumor, primary DLBCL. Literature review revealed only CIC-LEUTX was reported not only in sarcomas, but also in anaplastic ganglioglioma and CNS embryonal tumors. The partners of CIC sarcomas included DUX4, NUTM1, NUTM2A, FOXO4 and LEUTX, and whether specific partner affected biology of CIC-rearrangement tumors.

CONCLUSIONS

CIC-rearrangement arises in another type of brain cancer besides glioma and embryonal tumor, primary CNS DLBCL. Observation of novel partner provides new basis for further study of biology function of them in CIC fusions. Our study also indicates the presence of a specific tumor type with distinct histopathology driven by CIC fusions can be classified via CIC molecular pathology.
EPID-03. SINGLE INSTITUTIONAL CLINICAL AND GENETIC ANALYSIS OF METASTATIC PROSTATE CANCER WITH AND WITHOUT BRAIN METASTASES
Authors: Jaeger Ellen , Jang Albert , Xie John , Barata Pedro , Ledet Elisa , Trevino Christopher
Published: December 2020

BACKGROUND

Brain metastases (BMs) from metastatic prostate cancer (mPCa) are rare so little is known about clinical, genetic, and anatomic risk factors (RFs) for developing BMs. This single-center review of mPCa patients evaluates RFs for BM development.

METHODS

We reviewed records of mPCa patients at Tulane from 1991 – 2020 to evaluate disease, treatment, cell free DNA, and germline mutations between men with mPCa without confirmed BMs (smPCa) and men with mPCa and confirmed BMs (mPCaBMs).

RESULTS

We reviewed 580 patients with mPCa, of whom 11 had BMs (1.9%). Median age of stage 4 disease was 60.9 and 67.6 for men with mPCaBMs and smPCa respectively. Most mPCaBMs patients had Gleason 8 disease (81.8%) and higher median initial PSA (32 ng/mL) compared to 52.5% and 22.5 ng/mL for patients with smPCa. The development of castrate resistant disease (p=0.30) and overall survival (p=0.53) did not differ between the two populations. There were no differences in frequency of pathogenic mutations for the 68.9% (mPCaBMs) and 72.7% (smPCa) of patients with available genetic testing. Among the 11 mPCaBMs patients, 81.8% had supratentorial and 45.5% had infratentorial involvement (36.4% both). Forty-five percent had adjacent bony metastasis. Median time from SMs to BMs was 65 months (5.28 – 163.63 months), and median survival after diagnosis of BMs was 6.23 (0.49 – 70.82) months after treatment with WBRT, SRS, or GK.

CONCLUSIONS

The higher incidence of BMs likely reflects Tulane’s aggressive mPCa population. Interestingly 45% of BMs occurred from direct bony extension. Although 45% had infratentorial disease reflecting posterior fossa predilection, 82% of patients with BMs had supratentorial metastases. Our data suggest that men with mPCaBMs have aggressive disease and younger age at diagnosis. Due to sample size, no clinical or genetic statistically significant RFs for BMs were identified.
EPID-05. COMPARATIVE EFFICACY OF FIRST-LINE ALK-INHIBITORS IN ALK+ LUNG CANCER BRAIN METASTASES: A NETWORK META-ANALYSIS
Authors: Haddad Philip , Hammoud Dalia , Gallagher Kevin
Published: December 2020

BACKGROUND

Lung cancer has been the leading cause of cancer death for both men and women worldwide. Non-small-cell lung cancer (NSCLC) displays an array of molecular abnormalities most commonly involving ALK and EGFR pathways. NSCLC with ALK rearrangements comprises close to 5% of cases. Several ALK inhibitors (ALKI) have been approved with activity in brain metastases. However, there have been limited comparative studies exploring their relative efficacies. This meta-analysis was conducted to compare the relative efficacy of ALKIs against ALKI-naïve ALK+ lung cancer brain metastases.

METHODS

A review of the medical literature was conducted using online databases. Inclusion criteria consisted of English language; diagnosis of ALKI-naïve ALK+ lung cancer trials with brain metastases; treatment with Crizotinib (CRZ), Alectinib (ALC), Brigatinib (BRG), and Ceritinib (CER); and comparative studies reporting brain metastases specific responses/events. A Bayesian and a frequentists network meta-analysis were conducted using netmeta package and the random-effects model.

RESULTS

Eight studies comprising a total of 665 participants with ALKI-naive ALK+ lung cancer brain metastases were included. When compared pair-wise to CRZ, ALC (RR=0.49;95%CI:0.36–0.66), BRG (RR=0.39;95%CI:0.24–0.64), and CER (RR=0.36;95%CI:0.19–0.68) demonstrated significantly superior response rates in patients with untreated or previously treated lung cancer brain metastases. When the efficacy of each ALKI was compared to each other, BRG and CER were ranked the highest, followed by ALC and CRZ in decreasing order.

CONCLUSIONS

This network meta-analysis is the first to compare and rank approved ALKIs used in treating metastatic ALK+ lung cancer. It indicates that BRG, CER, and ALC are better therapeutic options for patients with ALK-naive ALK+ lung cancer brain metastases when compared to CRZ.
EPID-09. QUANTIFYING SOCIAL DETERMINANTS OF HEALTH AMONG GLIOMA PATIENTS
Authors: Hutchinson Angelica , Marshall Alexandria , Hsu Fang-Chi , Weaver Kathryn , DeTroye Alisha , Houston Kristin Strickland , Carter Annette , Chan Michael , Cramer Christina , Laxton Adrian , Tatter Stephen , Lesser Glenn , Canzona Mollie , Strowd Roy
Published: December 2020

BACKGROUND

Social determinants of health (SDH) are modifiable factors that contribute to health outcomes. Despite studies linking SDHs with cervical, ovarian, and prostate cancer outcomes, few studies have explored SDHs in glioma patients. We conducted a cross-sectional survey to characterize and contextualize SDHs in glioma patients by community income, rural/urban residence, and treatment status.

METHODS

Two validated instruments: PRAPARE (Protocol for responding to and assessing patents’ assets risks and experiences) and AHC (accountable health communities instrument) quantified SDHs; along with study-specific supplemental questions. Risk scores were calculated and combined into an overall and domain-specific (economic, education, neighborhood environment, social context, and healthcare) SDH risk, with a higher score being indicative of higher SDH risk. Scores were compared between low-income (LIC) vs high-income (HIC) communities (defined by median household income), urban vs rural (defined by zip code), and active treatment vs surveillance (determined by patient medical record) using Wilcoxon rank-sum test.

RESULTS

100 glioma patients were enrolled: mean age 53 years (range: 22–78); 49% male; 18% oligodendroglioma, 34% diffuse astrocytoma, 38% glioblastoma, 10% other glioma; 68% resided in LICs, 27% in rural zip codes, and 51% were on active treatment. Overall, SDH risk scores were low (mean= 4.43-out-of-38). Scores in the healthcare domain were the highest. Compared to patients from LICs, patients from HICs had higher healthcare risk scores (p< 0.05). Surveillance patients had higher overall SDH risk on the AHC than patients in active treatment (p< 0.05), with age being a confounder. In multivariable analysis, younger age, and astrocytoma histology were associated with higher social health risk.

CONCLUSION

Glioma patients report relatively few SDH risk factors on standardized instruments designed for general clinic populations. The higher health risk observed in patients in HICs and higher AHC risk for those in surveillance will be further explored in planned qualitative analysis.
EPID-23. A SYSTEMIC REVIEW OF CENTRAL NERVOUS SYSTEM TUMORS IN AFRICA FROM 1960 – 2017 AND THE NEED FOR A CENTRAL BRAIN TUMOR REGISTRY IN AFRICA
Authors: Mbi Feh Marilyn , Brahmaroutu Ankita , Lyon Kristopher , Fonkem Ekokobe
Published: December 2020

PURPOSE

Central Nervous System (CNS) tumors pose a substantial health problem. Although data on specific time periods and regions of Africa has been previously reported, no study has yet to provide a systemic review on the frequency of CNS tumors for the entire continent of Africa. This study aims to analyze the frequency of CNS tumors in Africa from 1960 to 2017.

METHODS

A comprehensive literature search on CNS tumors in Africa was performed using multiple online scientific databases. The following keywords were queried in combination with the phrase “CNS tumors in Africa”: incidence, frequency, epidemiology, prevalence, brain, and cancer. A total of 26 articles met the inclusion criteria. Each selected article reported incidence and mortality rates from different regions of Africa between 1960 to 2017. SPSS21 statistical software was used to analyze the data.

RESULTS

Nigeria, Egypt, and Uganda were found to have the highest incidence of CNS tumors in Africa. Total incidence was 5902, the majority were males, 3190 with mean rate 122.67 (95% CI: 29.27, 216.07) compared to females, 2501 with a mean rate of 96.19 (95% CI: 26.24, 166.15). The most common CNS tumors found were astrocytoma (24.70%), meningioma (22.22%), pituitary adenoma (8.4%), medulloblastoma (4.26%), craniopharyngioma (4.07%), and other not specified (25.17%).

CONCLUSION

Given the large population of Africa, the reported total incidence may be underestimated when compared to other continents due to the lack of a central brain tumor registry in Africa. Comprehensive knowledge of CNS tumors in Africa is critical to research and the entire healthcare system.
EPID-33. PRACTICE VARIATION OF STEROID DOSING AND TAPERING SCHEDULES AMONG THE NEURO-ONCOLOGY COMMUNITY
Authors: Jessurun Charissa , Hulsbergen Alexander , Tewarie Rishi Nandoe , Smith Timothy , Broekman Marike
Published: December 2020

INTRODUCTION

Steroids are commonly used for treatment of peritumoral edema and increased intracranial pressure in brain tumor patients. However, despite the widespread use of steroids, relatively little evidence is available about the optimal dosing scheme in brain tumor patients.

PURPOSE

The aim of this study is to increase insight in the practice variation of steroid dosing and tapering schedules among the neuro-oncology community.

METHODS

An electronic survey consisting of 27 questions regarding dosing and tapering schedules and adverse events of steroids was conducted among neurosurgeons internationally between 6 December 2019 and 1 June 2020. The survey was distributed by the electronic mailing lists of the Europeans Association of Neurosurgical Societies and via social media platforms. Collected data was assessed for quantitative and qualitative analysis using the Kruskal-Wallis test.

RESULTS

The survey obtained 175 responses. 87% of respondents answered all questions. Steroids are prescribed routinely perioperatively by 80% of respondents. Prescribed doses range from 2 to 64 mg/day in dosing schedule ranging from one to four times a day. The most prescribed steroid is dexamethasone in a dose of 16 mg/day. No significant association is seen between the prescribed dose and frequency of adverse events, years of experience, country, type of institution or having an institutional guideline.

CONCLUSION

Steroids are routinely prescribed perioperatively in brain tumor patients. However, there is a great practice variation in steroid dosing and tapering schedules among neurosurgeons. Future investigation is needed to identify an optimal dosing scheme and implement (inter)national guidelines for the dosing of steroids.
EPID-35. CLINICAL TRIAL ENROLLMENT RATE AMONG ADOLESCENT AND YOUNG ADULTS WITH CENTRAL NERVOUS SYSTEM TUMOR AT DANA-FARBER CANCER INSTITUTE (DFCI)
Authors: Sarvode Supriya , Warren Katherine , Reardon David , Yeo Kee Kiat
Published: December 2020

BACKGROUND

Adolescents and young adults (AYAs; 15–39 yrs.) are a population recognized as facing significant challenges in cancer care and research, characterized by historically poor participation in clinical trials. The clinical trial enrollment rate among AYAs with CNS tumor is unclear. We report the findings from our study evaluating the clinical trial enrollment rate of AYAs with CNS glioma at DFCI, comparing the rates between its affiliated adult and children’s hospitals.

METHODS

We performed a retrospective cohort study of patients with primary CNS glioma treated at our center between 2008–18. Eligible patients were identified using institutional databases at Boston Children’s Hospital and Brigham and Women’s Hospital. Manual chart review and data abstraction from the electronic medical record were performed to obtain key variables. Clinical trial enrollment rates were reported, followed by univariate and multivariate logistic regression models to identify factors affecting clinical trial enrollment.

RESULTS

In the adult setting, a total of 608 AYA patients with glioma were identified to meet our inclusion criteria and presented with a median age of 32 years (range:15–39). 92 out of 608 (15%) patients enrolled in a clinical trial during their treatment course. Within this cohort, tumor type was significantly associated with clinical trial enrollment, with higher-grade tumors associated with better enrollment rates (p< 0.001). On the contrary in the pediatric setting, a total of 52 AYA patients were identified from the children’s hospital, with a median age of 17.2 years (range:15–25.4) of whom, 19 out of 52 (36.5%) patients were enrolled on a clinical trial.

CONCLUSION

Clinical trial enrollment rate remains poor among AYAs with CNS tumors, with tumor type/histology grade associated with enrollment rate. Higher enrollment rates were seen among early AYAs treated at the children’s hospital.
EXTH-01. INHIBITION OF DNA-PKcs BY M3814 POTENTIATES EFFICACY OF IONIZING RADIATION IN PATIENT-DERIVED XENOGRAFTS OF MELANOMA BRAIN METASTASES
Authors: Ji Jianxiong , Smith Emily , Sarkaria Paige , Mladek Ann , Talele Surabhi , Swanson Katelyn , Mohammad Afroz S , Zhang Wenjuan , He Lihong , Hu Zeng , Zhao Yu , Chen Jiajia , Connors Margaret A , Porath Kendra A , Bakken Katrina K , Dragojevic Sonja , Carlson Brett L , Gupta Shiv K , Burgenske Danielle M , Kitange Gaspar J , Elmquist William F , Sarkaria Jann
Published: December 2020

Radio-resistance mechanisms limit the benefit of radiation therapy (RT) for melanoma brain metastases. A key pathway for radiation-induced DNA double-strand break repair is non-homologous end joining, which is critically mediated by DNA-dependent protein kinase (DNA-PKcs). Here we evaluated radio-sensitizing effects of M3814, a selective oral inhibitor of DNA-PKcs, in patient-derived xenografts (PDXs) of melanoma brain metastases. In a clonogenic survival assay, M3841 augmented RT-induced killing of M12 cells at concentrations of ≥300 nM, and a minimum of 16 h exposure with ~300 nM M3814 was required for effective sensitization. M3814 inhibited RT-induced (5 Gy) auto-phosphorylation of serine-2056 of DNA-PKcs in primary cultures of M12, M15 and M27 PDX lines. Interestingly, inhibition of RT-induced DNA-PKcs by M3814 coincided with increased KAP1 phosphorylation, a DNA damage signaling regulated via ATM. Persistent γH2AX foci were observed in 28% M12 cells at 24 hours after co-treatment with M3814 and RT as compared to 12% cells following RT alone. In vivo pharmacokinetic analysis after single oral dose of 20 mg/kg M3814, showed reasonably short half-life (~2.44 hours) and poor brain distribution in wild-type FBV mice (Kpuu, 0.027). Consistent with an efflux liability, brain distribution of M3814 in triple knockout mice for BCRP/MDR1A/B was ~11 fold higher (Kpuu, 0.215). Compared to normal brain, much higher M3814 concentrations were detected in intracranially implanted M12 tumors (~23 fold and ~20 fold) 2 and 6 hours after a single oral dose of 50mg/kg respectively. The relative exclusion of M3814 from normal brain as compared to brain metastases suggests that this drug may have a favorable toxicity profile when combined with radiation for treatment of melanoma brain metastases, and this hypothesis is being tested in ongoing efficacy studies.
EXTH-05. NON-CYTOTOXIC RADIATION ENHANCES DELIVERY OF ANTISENSE OLIGONUCLEOTIDES AND IMPROVES CHEMO-RADIATION EFFICACY IN BRAIN TUMOR XENOGRAFTS
Authors: Wu Jeffrey , Holland Samantha , Muldoon Leslie , Neuwelt Edward , Ambady Prakash
Published: December 2020

Overexpression of O6-methylguanine DNA methyltransferase (MGMT) contributes to brain tumor chemo-resistance. Previously we found that non-cytotoxic radiation improved anti-MGMT Morpholino Oligonucleotides (AMONs) delivery to reduce MGMT levels in subcutaneous tumor xenografts. Here we evaluated if radiation enhanced the delivery of intravenous (IV) AMONs to rat brain and improved chemo-radiation therapy (CRT) efficacy using rat models of human brain tumors. Athymic nude rats bearing orthotopic cerebellar D283 medulloblastoma or intracerebral H460 non-small cell lung carcinoma (NSCLC) brain metastasis xenografts were used. The impact of cranial radiation on delivery of IV 3’-carboxyfluorescein labeled oligonucleotides across the neurovascular unit was evaluated using confocal microscopy. We found that high brain parencymal fluorescence in radiated compared to non-radiated rats. MGMT protein silencing was assessed by immunoblot in tumor-bearing rats 3 d after 2 Gy cranial radiation alone or followed in 1 d by IV AMONs (10.5 mg/kg). Radiation followed by AMONs reduced MGMT expression by 50% in both xenograft models. To evaluate efficacy, tumor-bearing rats received one dose of 2 Gy radiation plus oral temozolomide (20 mg/kg x 4d) with or without IV AMONs. AMONs concurrent with CRT reduced tumor volumes in the medulloblastoma model (p=0.012), and a similar trend was found in the NSCLC brain metastasis model. In conclusion, we demonstrate the use of a single clinically relevant radiation dose fraction to guide and enhance the delivery of oligonucleotides into brain tumor xenograft models to reduce MGMT levels and improve CRT efficacy.
EXTH-10. COMBINATION OF EPIGENETIC ENZYME INHIBITORS, GSK-J4 AND BELINOSTAT, REVEALS HIGH EFFICACY IN IDH1 MUTANT GLIOMAS
Authors: Kayabolen Alisan , Sahin Gizem Nur , Seker Fidan , Cingoz Ahmet , Isik Bekir , Acar Simge , Wakimoto Hiroaki , Cahill Daniel , Solaroglu Ihsan , Cribbs Adam , Oppermann Udo , Bagci-Onder Tugba
Published: December 2020

Mutations in IDH1 and IDH2 genes are common in low grade gliomas and secondary GBM and are known to cause a distinct epigenetic landscape in these tumors. To interrogate the epigenetic vulnerabilities of IDH-mutant gliomas, we performed a chemical screen with inhibitors of chromatin modifiers and identified 5-azacytidine, Chaetocin, GSK-J4 and Belinostat as potent agents against primary IDH1-mutant cell lines. Testing the combinatorial efficacy of these agents, we demonstrated GSK-J4 and Belinostat combination as a very effective treatment for the IDH1-mutant glioma cells. Engineering established cell lines to ectopically express IDH1R132H, we showed that IDH1R132H cells adopted a different transcriptome with changes in stress-related pathways that were reversible with the mutant IDH1 inhibitor, GSK864. The combination of GSK-J4 and Belinostat was highly effective on IDH1R132H cells, but not on wt glioma cells or nonmalignant fibroblasts and astrocytes. The cell death induced by GSK-J4 and Belinostat combination involved the induction of cell cycle arrest and apoptosis. RNA sequencing analyses revealed activation of inflammatory and unfolded protein response pathways in IDH1-mutant cells upon treatment with GSK-J4 and Belinostat conferring increased stress to glioma cells. Specifically, GSK-J4 induced ATF4-mediated integrated stress response and Belinostat induced cell cycle arrest in primary IDH1-mutant glioma cells; which were accompanied by DDIT3/CHOP-dependent upregulation of apoptosis. Moreover, to dissect out the responsible target histone demethylase, we undertook genetic approach and demonstrated that CRISPR/Cas9 mediated ablation of both KDM6A and KDM6B genes phenocopied the effects of GSK-J4 in IDH1-mutant cells. Finally, GSK-J4 and Belinostat combination significantly decreased tumor growth and increased survival in an orthotopic model in mice. Together, these results suggest a potential combination epigenetic therapy against IDH1-mutant gliomas.
EXTH-21. INTRAINFUSION CATHETER MOVEMENT FACILITATES INCREASED INFUSATE VOLUME DISPERSED IN AGAROSE GEL
Authors: Mehta Jason , McRoberts Gabrielle , Rylander Christopher
Published: December 2020

Glioblastoma has a 5 year survival of only 5.5% and a median patient survival of 12 to 15 months even with gold standard treatment. One potential method of improving treatment of glioblastoma is the use of convection-enhanced delivery (CED) which utilizes local delivery of therapeutics to the brain. However, clinical trials have shown an inability of standard catheters to deliver therapeutics to the entire target area. In this study, we explore the potential of controlled catheter movement to increase the volume dispersed (Vd) of indigo carmine dye in agarose gel brain tissue phantoms. We use four catheter control protocols: stationary, continuous retraction, continuous insertion, and intermittent insertion using a single port stepped catheter. The continuous retraction group resulted in consistent catheter clogging caused by the continued insertion of the catheter and therefore was removed from further analysis. Vd and backflow distance was quantified for all other catheter movement protocols using optical images captured throughout the infusion. Catheter retraction resulted in an increase in Vd of 51% while intermittent insertion resulted in a Vd increase of 24% compared to the stationary catheter. Additionally, a 37% reduction in backflow distance was seen with the retracting catheter when compared to the stationary catheter. These results are further supported by a simplified computational model that we have created. The computational model simulates the infusion of indigo carmine dye through an agarose gel brain tissue phantom and shows an increase in Vd of over 100% with catheter retraction. The increased Vd and decreased backflow distance afforded by the retracting catheter, suggests that the use of catheter movement may be a useful technique in increasing drug dispersal in tumorous tissue. Additional work in live and excised tissue should be conducted to confirm these results and an exploration of optimal needle movement protocols is necessary.
EXTH-23. MULTIVALENT TARGETED CYTOLYTIC AGENTS FOR GLIOBLASTOMA TREATMENT
Authors: Sharma Puja , Herpai Denise , Roberts Callie , Fokt Izabela , Priebe Waldemar , Tatter Stephen , Rossmeisl John , Debinski Waldemar
Published: December 2020

Glioblastoma (GBM) complexity and heterogeneity requires treatment that addresses those pathobiological features. We have been developing selective cytotoxic agents able to target at the same time several GBM-associated factors. The chosen targets are responsible for the disease progression and/or recurrence as well as for resistance to the existing therapies. As a proof of concept, a Phase I clinical trial of a cytotoxic cocktail targeting IL-13RA2 and EphA2 receptors demonstrated dramatic anti-tumor responses in dogs with spontaneous gliomas that represent the closest translational model to human disease. To this end, we have developed multivalent agents that target four receptors specific to GBM: IL-13RA2, EphA2, EphA3, and EphB2, the combined expression of which covers virtually the whole tumor microenvironment. We have designed a multivalent protein termed QUAD 3.0 that contains an IgG1 scaffold, ephrinA5, which is a ligand for the EphA2, EphA3, and EphB2 receptors, and IL-13.E13K, a mutated version of interleukin 13 (IL-13), which binds preferentially to IL-13RA2. In QUAD 3.0, there is a cysteine at the C-terminal end of the protein to allow site-specific conjugation to cytotoxic cargo. QUAD 3.0 bound effectively to the four receptors in vitro and in vivo. QUAD 3.0 was conjugated to a modified form of Pseudomonas Exotoxin A (PE38QQR) and highly potent DNA binding agents based on modified doxorubicin (WP936, WP1737 and WP1244). All conjugates were highly cytotoxic to established and primary GBM cells with IC50s < 50 nM. We also treated the first dogs with QUAD 3.0-PE38QQR and QUAD 3.0-WP936 at a dose of 1.6 mg/ml using real-time monitored convection-enhanced delivery and observed up to 60% of tumor shrinkage and long-term survival. Thus, multivalent targeted agents demonstrate highly promising anti-tumor activity as single pharmaceutical, off-the-shelf agents. We also expect that our targeted drug candidates produce immune responses against tumors amplifying their cytolytic anti-tumor effect
EXTH-24. INCREASING THERAPEUTIC INDUCED NEURAL STEM CELL PERSISTENCE IN THE GLIOBLASTOMA TUMOR RESECTION CAVITY
Authors: Bomba Hunter , Sheets Kevin , Carey-Ewend Abigial , Goetz Morgan , Findlay Ingrid , Bago Juli , Hingtgen Shawn
Published: December 2020

BACKGROUND

Induced neural stem cells (iNSCs) have emerged as a promising therapeutic platform for glioblastoma (GBM). iNSCs have the innate ability to home to tumor foci, making them ideal carriers for anti-tumor payloads. However, iNSC persist for only two weeks in the murine GBM tumor resection cavity. We hypothesized that, by encapsulating iNSCs in a scaffold matrix, we could increase both the persistence of the cells the therapeutic durability.

METHODS

iNSCs expressing TRAIL were encapsulated in a gelatin-thrombin matrix; fibrinogen was used to polymerize the matrix. SEM was used to explore interactions between iNSCs and the scaffold matrix. To evaluate persistence, iNSCs encapsulated in the matrix were implanted into mock resection cavities of athymic nude mice and followed via BLI. To study the impacts of encapsulation on iNSC efficacy, athymic nude mice were implanted with U87 or GBM8 tumors. Tumors were then resected, and iNSCs encapsulated in the matrix were implanted; tumor volume was monitored via BLI.

RESULTS

SEM images showed homogeneous distribution of iNSCs throughout the matrix; iNSCs were completed encased in the fibrin clot component of the matrix and did not adhere to gelatin. In vivo, encapsulated iNSCs persisted for nearly 100 days whereas iNSCs directly injected into the brain parenchyma persisted < 20 days. Using mice bearing GBM8 tumors, animals treated with a high dose of therapeutic encapsulated iNSCs survived ~60 days longer than animals treated with non-therapeutic cells. A similar trend was observed in animals inoculated with U87 tumors. While not statistically significant, 25% of mice treated with iNSCs encapsulated in the gelatin-thrombin matrix survived longer than those treated with iNSCs encapsulated in a fibrin-only matrix, suggesting additional benefit due to the gelatin component.

FUTURE DIRECTIONS

Prospective experiments will explore the impact of the scaffold on iNSC phenotype, including proliferation, differentiation, and migration markers.
EXTH-30. EXPANDING THE UTILITY OF PRE-CLINICAL CONTRAST ENHANCED CT (CE-CT) FOR TUMOR DETECTION IN ORTHOTOPIC GBM MODELS USING RADIOMICS
Authors: Connor Kate , Conroy Emer , White Kieron , Shiels Liam , Gallagher William , Keek Simon , Ibrahim Abdalla , Clerkin James , O’Brien David , Lambin Philippe , Woodruff Henry , Byrne Annette
Published: December 2020

Despite magnetic resonance imaging (MRI) being the gold-standard imaging modality in the glioblastoma (GBM) setting, the availability of rodent MRI scanners is relatively limited. CT is a clinically relevant alternative which is more widely available in the pre-clinic. To study the utility of contrast-enhanced (CE)-CT in GBM xenograft modelling, we optimized CT protocols on two instruments (IVIS-SPECTRUM-CT;TRIUMPH-PET/CT) with/without delivery of contrast. As radiomics analysis may facilitate earlier detection of tumors by CT alone, allowing for deeper analyses of tumor characteristics, we established a radiomic pipeline for extraction and selection of tumor specific CT-derived radiomic features (inc. first order statistics/texture features). U87R-Luc2 GBM cells were implanted orthotopically into NOD/SCID mice (n=25) and tumor growth monitored via weekly BLI. Concurrently mice underwent four rounds of CE-CT (IV iomeprol/iopamidol; 50kV-scan). N=45 CE-CT images were semi-automatically delineated and radiomic features were extracted (Pyradiomics 2.2.0) at each imaging timepoint. Differences between normal and tumor tissue were analyzed using recursive selection. Using either CT instrument/contrast, tumors > 0.4cm3 were not detectable until week-9 post-implantation. Radiomic analysis identified three features (waveletHHH_firstorder_Median, original_glcm_Correlation and waveletLHL_firstorder_Median) at week-3 and -6 which may be early indicators of tumor presence. These features are now being assessed in CE-CT scans collected pre- and post-temozolomide treatment in a syngeneic model of mesenchymal GBM. Nevertheless, BLI is significantly more sensitive than CE-CT (either visually or using radiomic-enhanced CT feature extraction) with luciferase-positive tumors detectable at week-1. In conclusion, U87R-Luc2 tumors > 0.4cm3 are only detectable by Week-8 using CE-CT and either CT instrument studied. Nevertheless, radiomic analysis has defined features which may allow for earlier tumor detection at Week-3, thus expanding the utility of CT in the preclinical setting. Overall, this work supports the discovery of putative prognostic pre-clinical CT-derived radiomic signatures which may ultimately be assessed as early disease markers in patient datasets.
EXTH-32. TARGETED STAT3 INHIBITION IMPAIRS MDSC MOBILIZATION AND RECRUITMENT IN GLIOBLASTOMA
Authors: von Roemeling Christina , Li Chenglong , Mitchell Duane
Published: December 2020

BACKGROUND

Glioblastoma tumors (GBM) are comprised upwards of 30 percent by glioma-associated myeloid cells (GAMs). A large fraction of GAMs are myeloid-derived suppressor cells (MDSC) thought to traffic in from peripheral circulation. MDSCs foster a hospitable environment for cancer cells by regulating immune suppression and driving resistance to immunotherapy. While signal transducer and activator of transcription 3 (STAT3) is considered to be a specific marker for MDSCs and is a known player in their phenotypic polarization in cancer, we sought to closely examine its specific role in MDSC trafficking and tumor recruitment.

HYPOTHESIS

Targeted inhibition of STAT3 blocks MDSC from the bone marrow, mitigating their accumulation within GBM tumors.

METHODS

Human and murine GBM samples were analyzed for immune-specific STAT3 phosphorylation (P-STAT3). Immune cell characterization and quantification in peripheral and GBM tissue from syngeneic murine models treated with a novel STAT3 inhibitor (LLL12B) was done. Therapeutic responses to LLL12B alone and in combination with immune checkpoint blockade were evaluated.

RESULTS

We found P-STAT3 to be predominantly expressed by tumor-associated immune cells in both human and murine GBM, particularly MDSCs. Circulating numbers of MDSCs dramatically increase in response to tumor burden. P-STAT3 is elevated in these cells, indicating that its activation occurs prior to tumor infiltration. LLL12B blockade of STAT3 significantly reduced the number of circulating and tumor-infiltrating MDSCs. As a single agent LLL12B reduced tumor volume and extended the survival of murine GBM models. When combined with anti-PD-1 checkpoint blockade, we observed durable survival in a significant fraction of treated mice.

CONCLUSIONS

These findings advocate a critically important role for STAT3 in regulating MDSC mobilization and trafficking to GBM tumors. It additionally reveals a new therapeutic mechanism of action for LLL12B that may be relevant for other direct inhibitors of STAT3, influencing their clinical applicability to treat GBM.