bluuebunny/crossref_metadata_2025 huggingface dataset:
A case of Paget’s disease of bone associated with hypomyopathic dermatomyositis
Authors: Soenjoyo Karina Ruth , Chua Marvin Wei Jie
Published: November 2021

Dermatomyositis is associated with malignancies and is known to have systemic involvement. However, associations with bone diseases have not been well described in the current literature. This article describes the second reported case of the co-existence of dermatomyositis and Paget’s disease of bone (PDB), but this is the first report to describe such co-existence in a specific subtype of dermatomyositis—hypomyopathic dermatomyositis. Our patient was a 51 year old woman who presented with prolonged fever, myalgia, morning stiffness, and rashes pathognomonic of dermatomyositis. There was no muscle weakness clinically, although muscle enzymes were increased and electromyogram revealed myopathic changes. Further imaging showed the incidental finding of a T11 vertebral bone lesion, of which biopsy confirmed the diagnosis of PDB. Our report illustrates the diagnostic approach to bone lesions in patients with dermatomyositis and takes a closer look at the pathophysiology and management implications of the co-occurrence of these two rare diseases.
Database resources of the national center for biotechnology information
Authors: Sayers Eric W , Bolton Evan E , Brister J Rodney , Canese Kathi , Chan Jessica , Comeau Donald C , Connor Ryan , Funk Kathryn , Kelly Chris , Kim Sunghwan , Madej Tom , Marchler-Bauer Aron , Lanczycki Christopher , Lathrop Stacy , Lu Zhiyong , Thibaud-Nissen Francoise , Murphy Terence , Phan Lon , Skripchenko Yuri , Tse Tony , Wang Jiyao , Williams Rebecca , Trawick Barton W , Pruitt Kim D , Sherry Stephen T
Published: November 2021

The National Center for Biotechnology Information (NCBI) produces a variety of online information resources for biology, including the GenBank® nucleic acid sequence database and the PubMed® database of citations and abstracts published in life science journals. NCBI provides search and retrieval operations for most of these data from 35 distinct databases. The E-utilities serve as the programming interface for the most of these databases. Resources receiving significant updates in the past year include PubMed, PMC, Bookshelf, RefSeq, SRA, Virus, dbSNP, dbVar, ClinicalTrials.gov, MMDB, iCn3D and PubChem. These resources can be accessed through the NCBI home page at https://www.ncbi.nlm.nih.gov.
NAD+ bioavailability mediates PARG inhibition-induced replication arrest, intra S-phase checkpoint and apoptosis in glioma stem cells
Authors: Li Jianfeng , M. Saville Kate , Ibrahim Md , Zeng Xuemei , McClellan Steve , Angajala Anusha , Beiser Alison , Andrews Joel F , Sun Mai , Koczor Christopher A , Clark Jennifer , Hayat Faisal , Makarov Mikhail V , Wilk Anna , Yates Nathan A , Migaud Marie E , Sobol Robert W
Published: November 2021

Elevated expression of the DNA damage response proteins PARP1 and poly(ADP-ribose) glycohydrolase (PARG) in glioma stem cells (GSCs) suggests that glioma may be a unique target for PARG inhibitors (PARGi). While PARGi-induced cell death is achieved when combined with ionizing radiation, as a single agent PARG inhibitors appear to be mostly cytostatic. Supplementation with the NAD+ precursor dihydronicotinamide riboside (NRH) rapidly increased NAD+ levels in GSCs and glioma cells, inducing PARP1 activation and mild suppression of replication fork progression. Administration of NRH+PARGi triggers hyperaccumulation of poly(ADP-ribose) (PAR), intra S-phase arrest and apoptosis in GSCs but minimal PAR induction or cytotoxicity in normal astrocytes. PAR accumulation is regulated by select PARP1- and PAR-interacting proteins. The involvement of XRCC1 highlights the base excision repair pathway in responding to replication stress while enhanced interaction of PARP1 with PCNA, RPA and ORC2 upon PAR accumulation implicates replication associated PARP1 activation and assembly with pre-replication complex proteins upon initiation of replication arrest, the intra S-phase checkpoint and the onset of apoptosis.
A robust confidence–accuracy dissociation via criterion attraction
Authors: Rahnev Dobromir
Published: November 2021

Many studies have shown that confidence and accuracy can be dissociated in a variety of tasks. However, most of these dissociations involve small effect sizes, occur only in a subset of participants, and include a reaction time (RT) confound. Here, I develop a new method for inducing confidence–accuracy dissociations that overcomes these limitations. The method uses an external noise manipulation and relies on the phenomenon of criterion attraction where criteria for different tasks become attracted to each other. Subjects judged the identity of stimuli generated with either low or high external noise. The results showed that the two conditions were matched on accuracy and RT but produced a large difference in confidence (effect appeared for 25 of 26 participants, effect size: Cohen’s d = 1.9). Computational modeling confirmed that these results are consistent with a mechanism of criterion attraction. These findings establish a new method for creating conditions with large differences in confidence without differences in accuracy or RT. Unlike many previous studies, however, the current method does not lead to differences in subjective experience and instead produces robust confidence–accuracy dissociations by exploiting limitations in post-perceptual, cognitive processes.
EPCO-04. RADIOTHERAPY IS ASSOCIATED WITH GLOBAL METHYLATION ALTERATIONS IN PATIENT DERIVED GLIOBLASTOMA CELL LINES
Authors: Modrek Aram , Byun David , Ezhilarasan Ravesanker , Snuderl Matija , Sulman Erik
Published: November 2021

PURPOSE/OBJECTIVE(S)

In glioblastoma, DNA methylation states are the most predictive marker of overall survival and response to therapy. Our understanding of how epigenetic states, such as DNA methylation, are “mis-repaired” after DNA damage repair is scant, hampering our ability to understand how treatment associated DNA methylation alterations may drive tumor resistance and growth.

MATERIALS AND METHODS

Three different patient derived IDH wild-type glioma stem cell (GSC) lines, in duplicates, were treated with radiation (20 Gray in 10 fractions vs. sham control) and allowed to recover prior to DNA methylation analysis with 850K methylation arrays. To analyze the methylation array data via bioinformatic methods we used RnBeads (version 2.4.0) and R (version 3.6.1) packages. We further focused our analysis to specific genomic regions, including CpG islands, promoters, gene bodies and CTCF motifs to understand how methylation alterations may differ between these and other genomic contexts following radiation.

RESULTS

There were widespread differential methylation (pre-treatment vs. radiation treatment) changes among the genomic regions examined. Interestingly, we found differential methylation changes at CTCF motifs, which play important DNA-methylation dependent roles in gene expression and chromatin architecture regulation. Hierarchical clustering, PCA and MDS analysis of DNA methylation status amongst CpG islands, promoters, gene bodies and CTCF domains revealed strong intra-sample differences, but not inter-sample differences (between GSC lines), suggesting radiation associated methylation alterations maybe loci and context dependent.

CONCLUSION

Radiation treatment is associated with wide-spread alterations of DNA methylation states in this patient derived glioblastoma model. Such alterations may drive gene expression changes or genomic architecture alterations that lead to treatment resistance, warranting further mechanistic investigation of the interplay between radiation induced DNA damage and local epigenetic state restoration following DNA damage repair.
EPCO-12. STING IS SILENCED IN GBM BY PROMOTER METHYLATION THAT IS ESTABLISHED BY TISSUE OF ORIGIN
Authors: Low Justin , Chandramohan Vidyalakshmi , Bowie Michelle , Brown Michael , Waitkus Matthew , Briley Aaron , Stevenson Kevin , Fuller Rebecca , Reitman Zachary , Muscat Andrea , hariharan Seethalakshmi , Hostettler Janell , Wong Nicholas , Gromeier Matthias , Ashley David M
Published: November 2021

STING (Stimulator of interferon genes) is an initiator of endogenous antitumor immunity. Loss of STING expression has been observed in various cancer types. Here we describe a mechanism of STING suppression that is common to brain tumors, occurring through regional promoter hypermethylation (RPH) near its transcriptional start site. The RPH-mediated suppression of STING expression is selective to normal brain and neuroectoderm-derived tumors, but not present in most other tumor types and cells in the brain tumor microenvironment. A pan-cancer comparison revealed that STING RPH levels in tumors correlate with the respective tissue of origin, including tumors metastasizing to the brain. We demonstrate that STING RPH suppression in glioma cells may be reversed by treatment with decitabine, a DNA methyltransferase inhibitor that is used in the treatment of hematologic malignancies. Collectively, our results suggest that the epigenetic silencing of STING occurs early in brain development and may provide an immunosuppressive context for the genesis of brain tumors. Furthermore, our findings that STING suppression in brain tumor cells can be reversed by epigenetic modulation have significant therapeutic implications for the treatment of glioblastoma and potentially other STING-silenced, immunologically-cold cancers.
EPCO-19. SYSTEMS BIOLOGY APPROACH ON MGMT-METHYLATED, IDH WILD-TYPE SHORT-TERM SURVIVORS REVEALS MUTATIONS IN THE BRCA1-MEDIATED DNA REPAIR SIGNALING PATHWAY
Authors: Noorbakhsh Cameron , Liu Yang , Lang Frederick , DeGroot John , Akdemir Kadir , Alfaro-Munoz Kristin , Parker-Kerrigan Brittany , Jaffray David , Huse Jason , Bhat Krishna , Puduvalli Vinay , Kannan Kasthuri
Published: November 2021

Numerous multi-omic studies have revealed the vast molecular complexity of glioblastoma; however, these studies have failed to identify actionable drivers for definitive therapy. Unlike conventional relational data analysis methods used to examine such data, systems biology approaches using graph databases have emerged as powerful tools with flexibility and scalability needed to reveal specific vulnerabilities. Here we demonstrate the utility of a patient-centric graph database in identifying novel factors associated with poor outcome (survival < 8 months) in patients with MGMT promoter methylated glioblastoma. Using a cohort of 112 patients from the TCGA database, we integrated high-impact mutations with MGMT methylation status. Network analysis revealed three subnetworks, consisting of (a) methylated patients, the M-network, (b) methylated and unmethylated patients, the MU-network, and (c) unmethylated patients, the U-network. In addition, querying the genes in the M-network revealed three key molecules in the DNA repair pathway, namely, FANC-A, FANC-E, and MYUTH, mutated in five patients (q-value < 2.3E-02). Moreover, we observed that BRCA1 mediates other critical signaling molecules in the MU-network. Interestingly, in intermediate (8-24 months) or long-term ( >24 months) survivors networks, this pathway is not implicated. In light of recent studies implicating BRCA1 modulating temozolomide resistance in GBM sphere-forming cells and BRCA1’s protein expression predicting survival in patients, this result suggests that mutations in BRCA1-mediated DNA repair pathways hinder response to chemotherapy despite methylated MGMT, reducing the survival in patients. Besides this novel result explaining low survival in MGMT methylated patients through a synthesis of epigenetic and genetic data, our framework provides a novel and compelling paradigm for data integration at various scales from molecular events in a single patient’s tumor to integrating the molecular profile (or genotype) with phenotypic characteristics at the population level. We will present additional insights derived from this analysis at the SNO annual meeting.
EPCO-26. INTEGRATIVE MULTI-OMICS IDENTIFIES CONVERGING DEVELOPMENTAL ORIGINS OF DISTINCT MEDULLOBLASTOMA SUBGROUPS
Authors: Smith Kyle , Bihannic Laure , Gudenas Brian , Gao Qingsong , Haldipur Parthiv , Hovestadt Volker , Iskusnykh Igor , Chizhikov Viktor , Deng Mei , Glass Ian , Robinson Giles , Orr Brent , Patay Zoltan , Aldinger Kimberly , Millen Kathleen , Northcott Paul
Published: November 2021

Understanding the interplay between normal development and tumorigenesis, including the identification and characterization of lineage-specific origins of MB, is a fundamental challenge in the field. Recent studies have highlighted novel associations between biologically distinct MB subgroups and diverse murine cerebellar lineages via cross-species single-cell transcriptomics. Specifically, Group 4-MB correlated with the unipolar brush cell lineage and Group 3-MB resembled Nestin+ stem cells of the early cerebellum. However, these analyses were hampered by low resolution due to the sparsity of pertinent cerebellar cell types and the cross-species nature of the approach. Herein, we profoundly expand the depth of these rare developmental populations in the murine cerebellum using a combination of lineage tracing and integrative multi-omics. Isolation and enrichment of spatially and temporally unique developmental trajectories of key rhombic lip-derived glutamatergic lineages provided an enhanced reference for mapping MB subgroups based on molecular overlap, especially for poorly defined Group 3- and Group 4-MB. Further comparisons to a novel single-cell atlas of the human fetal cerebellum, companioned with laser-capture microdissected transcriptional and epigenetic datasets, reinforced developmental insights extracted from the mouse. Characterization of compartment-specific transcriptional programs and co-expression networks identified in the human upper rhombic lip implicated convergent cellular correlates of Group 3- and Group 4-MB, suggestive of a common developmental link. Together, our results strongly implicate developmental lineages of the upper rhombic lip as the probable origins of poorly defined Group 3- and Group 4-MB. These important findings will shape future efforts to accurately model the biological heterogeneity underlying these subgroups and provide unprecedented opportunities to explore their cellular and mechanistic basis.
BIOM-22. RELEVANCE OF TUMOR MUTATION BURDEN (TMB) IN HIGH-GRADE GLIOMAS
Authors: Ligumsky Hagai , Blumenthal Deborah , Bokstein Felix
Published: November 2021

BACKGROUND

Efforts have been directed toward searching for molecular biomarkers predicting response to immunotherapy in glial tumors. Recently, FDA granted accelerated approval of pembrolizumab for treatment patients with solid tumors with high mutational burden (TMB-H; ≥ 10 mut/Mb). There are conflicting results regarding the use of this parameter in glial tumors.

OBJECTIVE

to review NGS examinations of patients with glial tumors and high TMB and to analyze their response to immunotherapy.

METHODS

we retrospectively reviewed NGS examinations from patients with glial tumors treated in Tel-Aviv Medical Center from 2016-2021. Cases with TMB-H were retrieved and analyzed.

RESULTS

We identified nine high-grade glioma patients with TMB-H. The median age was 38 (19-65). There were 4 patients with glioblastoma; three with anaplastic oligodendroglioma; and two with anaplastic astrocytoma. All but one received radiation prior to the biopsy used for NGS examination, and all were treated with temozolomide. The median TMB was 54 (19-252). Only one glioblastoma patient with a family history of Lynch syndrome had microsatellite instability (MSI)-high; all other patients were MSI stable (MSS). Nevertheless, in all cases, mutated mismatch repair (MMR) genes were detected (MSH6 in 3 patients, MSH2 in one patient, MLH1 in one patient, PMS 2 in one patient, and both MSH2 and 6 in one patient). Six patients received immunotherapy. Only one patient with recurrent glioblastoma and the highest TMB in the group (252) demonstrated a near complete response to pembrolizumab and remains on treatment more than three years. All other patients did not respond to immunotherapy.

CONCLUSION

TMB-H in primary glioma is associated with mutations of MMR genes. It is typically associated with MSS in these patients (MSI-high was seen in only one syndromic patient). In contrast to systemic neoplasms with TMB-H, the majority of our patients did not respond to immunotherapy.
BIOM-27. INTEGRATED PREDICTION OF VENOUS THROMBOEMBOLISM IN GLIOMA PATIENTS
Authors: Unruh Dusten , Drumm Michael , Lamano Jonathan , Schwartz Margaret , Tran Anh , Javier Rodrigo , McCortney Kathleen , Amidei Christina , Burdett Kirsten , Scholtens Denise , Horbinski Craig
Published: November 2021

BACKGROUND

Venous thromboembolism (VTE) is a debilitating and life-threating condition that is common in patients with cancer, especially glioma. There are no widely-accepted guidelines for antithrombotic prophylaxis in glioma patients, in part because of the risk of iatrogenic intracerebral hemorrhage. Effective VTE prediction models exist for patients with other cancers, but not glioma. Our prior publications suggested a protective role of IDH mutation (IDHmut) against VTE, as well as a positive association between elevated circulating Tissue Factor (TF), a procoagulant secreted by cancers, and VTE in glioma patients. Others have recently found a correlation between podoplanin, a platelet activator, and cancer-associated VTE, but this has not yet been proven in gliomas. Our objective was to develop a multidimensional VTE prediction tool to improve glioma patient care, incorporating clinical, blood-based, histologic, and molecular markers.

METHODS

The Northwestern University Nervous System Tumor Bank provided preoperative arterial blood, tumor tissue, and clinical-pathologic data from 254 grade II-IV glioma patients over a 4-year interval. Molecular profiling was done by GlioSeq NGS.

RESULTS

Forty-six out of 254 grade II-IV glioma patients (18%) experienced VTE during their disease course. VTE was associated with worse median overall survival (18 vs. 54 months, P< 0.001). Positive risk factors for VTE included advanced patient age, high body mass index, high glioma grade, prior history of VTE, coronary artery disease, hyperlipidemia, hypertension, and elevated circulating TF activity, among other variables. While tumor expression of podoplanin positively correlated with VTE, circulating podoplanin did not. Among molecular markers, the strongest was IDHmut, being associated with greatly reduced VTE risk (OR=0.28; 95% CI=0.12-0.64, P=0.001).

CONCLUSIONS

This study identified multiple risk factors for glioma-associated VTE. Using these data, we have developed a web-based multivariable integrated prediction calculator to identify glioma patients who would benefit the most from prophylactic anticoagulation.
BIOM-39. METHYLATION AND MUTATION PROFILES IN MENINGIOMA CELL-DERIVED EXTRACELLULAR VESICLE DNA REFLECT EPIGENETIC AND GENOMIC ALTERATIONS IN ORIGINAL TUMORS
Authors: Ricklefs Franz , Maire Cecile , Wollmann Kathrin , Dührsen Lasse , Fita Krystian , Sahm Felix , Herold-Mende Christel , von Deimling Andreas , Fuh Marceline , Schlüter Harmut , Glatzel Markus , Westphal Manfred , Lamszus Katrin
Published: November 2021

The majority of meningiomas are benign but approximately 20% of display an aggressive behavior, resulting in significant patient morbidity and mortality. Standard monitoring after meningioma resection relies on serial MRI examinations, which are time-consuming, expensive and provide no information on molecular alterations that may indicate progression towards a more aggressive tumor. Extracellular vesicles (EVs) are released by tumor cells and contain high molecular weight DNA, rendering circulating EVs a potential biomarker source for non-invasive disease monitoring and for obtaining information on genetic and epigenetic alterations. We quantified EVs in plasma of 46 meningioma patients (n = 29 M1, 12 M2, 5 M3) by nanoparticle tracking analysis and detected significantly higher levels compared to age-matched healthy donors (n = 18). EV concentrations correlated with malignancy grade (p = 0.0049) and with the extent of peritumoral edema (p = 0.0031). Comparisons between paired pre- and postoperative samples revealed that EV levels counts dropped significantly the day after tumor resection and were reduced to normal levels after about one week. Completely resected patients (Simpson grade I) displayed a greater reduction of postoperative EV concentrations than incompletely resected patients. DNA methylation profiling was performed on EVs secreted by cultured meningioma cells, as well as matched cells and original tumors using 850k arrays (n = 7 M1, 5 M2, 3 M3). All EV samples were correctly identified as meningiomas by the Heidelberg classifier, and methylation subclasses were also correctly assigned in almost all cases. t-SNE analysis showed that EVs mapped in close proximity to their corresponding parental cells and tumor tissue. Tumor specific mutations and copy number variations were detected in EV-DNA with high accuracy. Differential quantitative proteomic analysis of EVs, cells and tumors identified shared proteins that could potentially be useful for enriching tumor-derived circulating EVs from biofluids.
STEM-10. UPSTREAM REGULATORS OF THE GLIOMA STEM CELL PHENOTYPE
Authors: Calinescu Alexandra , Sultan Zain , Kauss McKenzie , Al-Holou Wajd , Heth Jason
Published: November 2021

Glioblastoma (GBM) is the most common and deadly primary brain tumor in adults. Recurrence of the disease is attributed in part to the presence of Glioma Stem Cells (GSC), which are resistant to chemo- and radiotherapy and can initiate tumor formation. Molecularly, GSCs resemble the mesenchymal subtype that is associated with worse prognosis. GSCs share many characteristics with Neural Stem Cells (NSCs) including proliferative potential, migratory capacity, telomerase activity, diverse progeny and similar gene signature, however differ fundamentally from NSCs in their tumor forming ability. RNA-Seq analysis of GSCs and NSCs illustrates significant enrichment in GSCs of transcription factors (TFs) known to be dysregulated in cancer, chief among them being SIX1, a developmental TF with documented roles in progression of multiple cancers. Overexpression of SIX1 in A172 GBM cells enhances proliferation, promotes resistance to radiotherapy and alters expression of a core set of 4 developmental TFs (POU3F2, SALL2, OLIG2 and SOX2) capable to reprogram differentiated GBM cells into GSCs (Suva et al., 2014). Analysis of SIX1 in surgical samples from glioma patients illustrates that high expression of SIX1 correlates with tumor grade, finding corroborated in the TCGA and CGGA data sets. Surprisingly, primary NSCs, after extended time in culture, increase their proliferation rate, acquire a mesenchymal transcriptional signature akin to GSCs, including high expression of SIX1, and form deadly tumors when implanted into the brains of mice. Comparing the epigenetic landscape of transformed and normal NSCs we identify a significant enrichment of accessible chromatin at promoter and enhancer loci in transformed NSCs, including at regulatory regions of SIX1 and of genes that define mesenchymal GBM. These data suggest that SIX1 may represent an upstream regulator of the GSC phenotype and may drive malignant transformation of NSCs. Genetic and epigenetic loss of function analyses are ongoing to test this hypothesis.
STEM-18. STROMAL EXTRACELLULAR VESICLES DRIVE GLIOMA STEM CELL REPROGRAMMING
Authors: Adnani Lata , Meehan Brian , Kassouf Jordan , Spinelli Cristiana , Tawil Nadim , Rak Janusz
Published: November 2021

Glioblastoma multiforme (GBM) represents the most frequent and lethal form of brain tumors originating from glioma stem cells (GSCs). GBM remains lethal because the rate limiting patho-mechanisms remain poorly understood. In this regard, few limitations involve the diversity 'between' cellular states and the molecular/cellular complexity 'within' the tumour mass. Using cell based- and mouse- models, we explored extracellular vesicle (EV) mediated interactions between cancer and stromal cells impacting phenotypes of GSCs as a function of their molecular subtype. EVs are spherical membrane structures that cells release to expel different molecular cargo (lipids, proteins, RNA, DNA), which can be transported across a distance in the brain and taken up by various ‘recipient’ cells resulting in reprogramming of the recipient cell's content and function. In vivo, GSCs altered their pattern of NOTCH signalling and molecular phenotype as a function of proximity to non-transformed host cells in the brain. In vitro stromal EVs altered GSC sphere forming capacity, proteome and expression of mesenchymal markers. Thus, EV mediated tumour-stromal interactions could represent a biological switch and a novel targeting point in the biology of GBM.
CBIO-04. G-QUADRUPLEX STABILIZATION ENHANCES REPLICATION STRESS AND DNA DAMAGE IN ATRX-DEFICIENT HIGH-GRADE GLIOMA
Authors: Dharmaiah Sharvari , Tadimeti Vasudev , Malgulwar Prit Benny , Alvarez Christian , Farooqi Ahsan , Huse Jason
Published: November 2021

Loss of function mutations in α-thalassaemia/mental retardation X-linked (ATRX) are a critical molecular hallmark for invariably fatal high-grade glioma (HGG). Mutational inactivation of histone chaperone ATRX leads to accumulations of abnormal DNA secondary structures known as G-quadruplexes (G4s), thereby inducing replication stress and DNA damage. As G4s arise at GC-rich regions (i.e., pericentromeric and telomeric regions), ATRX-deficiency alters genome-wide accessibility of chromatin, leads to transcriptional dysregulation, and induces alternative lengthening of telomeres (ALT). Our goal is to target ATRX deficiency through G4 stabilizers, which represent a class of novel small molecule compounds that selectively bind to and stabilize G4 structures. However, the genomic consequences and efficacy of this therapy for ATRX-deficient HGG are poorly understood. We therefore sought to evaluate the molecular mechanisms that drive selective lethality in patient-derived ATRX-deficient glioma stem cells (GSCs), following G4 stabilization. We found that ATRX-deficient GSCs demonstrate dose-dependent enhanced sensitivity to G4 stabilization, compared to ATRX-intact controls. Cell viability assays confirmed the specificity of our G4 stabilizer in comparison to other commonly used G4 stabilizers. Interestingly, G4 stabilization activated p53-independent apoptosis in ATRX-deficient GSCs. Furthermore, ATRX-deficient GSCs exhibit upregulated expression of both ATR and ATM pathways upon G4 stabilization, indicating enhanced replication stress and DNA damage via double-stranded breaks, respectively. Our preliminary findings suggest that ATR and ATM activation leads to the inhibition of transcription factor NF-κB, which in turn drives apoptosis. Lastly, our data indicate that G4 stabilization perturbs the ALT phenotype in ATRX-deficient GSCs, likely contributing to telomeric dysfunction. Taken together, these findings suggest that G4 stabilizers could synergize with ionizing radiation, the standard of care, as they are both DNA-damaging therapies. Our work defines mechanisms of action and efficacy of a novel therapeutic strategy for ATRX-deficient HGG, with strong implications for other ATRX-deficient cancers.
CBIO-26. A NEW MODEL OF THE GABP-TERT REGULATORY AXIS IN MAINTAINING IMMORTALITY OF TERT PROMOTER MUTANT TUMOR CELLS
Authors: Stevers Nicholas , Barger Carter , Lenzo Olivia , Hong Chibo , McKinney Andrew , Costello Joseph
Published: November 2021

Tumor cell immortality is a fundamental hallmark of human cancers. Normally silenced during somatic cell differentiation, 90% of human tumors reactivate Telomerase Reverse Transcriptase (TERT) expression to achieve cellular immortality. TERT, the catalytic subunit of telomerase, complexes with the RNA template molecule TERC to maintain telomeres. Mutations in the TERT promoter (TERTp) are the most common non-coding mutation across all cancer types and the most frequent mutation within many cancers, such as IDH wildtype glioblastoma (GBM), Melanoma, and Bladder Cancer. TERTp mutations generate de novo E26 Transformation Specific (ETS) binding motifs that are spaced full helical turns from TERTp native ETS sites. Together the de novo and native ETS motifs specifically recruit the GABP tetrameric complex but not the GABP dimer. CRISPR-cas9 mediated insertion/deletion mutagenesis of the unique exon of GABP tetramer forming subunit, GABPB1L (B1L), reduces TERT transcriptional activity in a TERT promoter-mutation dependent manner. Here we show that GABPB1S (B1S), the GABP dimer restricted alternative isoform of GABPB1, is consistently and significantly increased following B1L reduction, a process we have determined to be driven by a conserved homeostatic mechanism whereby the GABP tetramer suppresses expression of one of its own components, GABPB1. In contrast to the native setting, in the absence of B1L the elevated B1S expression leads to dimer binding to the mutant TERTp and maintenance of TERT expression. Indeed, co-targeting B1L and B1S together, but not B1L alone, via CRISPR-cas9 knockout resulted in a near complete elimination of GABP recruitment to the TERTp and TERT expression, and lead to tumor cell death and eventual senescence in a telomere length dependent manner. Together, this data suggests a new model of the TERT-GABP axis involving the tetramer and dimer and highlights a new and potentially more potent therapeutic strategy to eliminate TERT expression and reverse tumor cell immortality.
CSIG-08. ABT-414 RESISTANT GBM TUMORS HARBOR THE TEK S466I MUTATION AND EXHIBIT INCREASED STEMNESS
Authors: Blomquist Mylan , Noviello Teresa , D'Angelo Fulvio , Sereduk Christopher , Rabichow Benjamin , Miller Aunay , Marin Bianca-Maria , White Forest , Sarkaria Jann , Lasorella Anna , Iavarone Antonio , Ceccarelli Michele , Tran Nhan
Published: November 2021

Glioblastoma (GBM), the most common primary brain tumor in adults, remains uniformly fatal due to the lack of effective targeted therapies for this aggressive malignancy. Genomic amplification of epidermal growth factor receptor (EGFR) occurs in 40-60% of primary GBM. Half of all EGFR-amplified cases of GBM also harbor EGFRvIII, a constitutively active, truncated variant of EGFR. The incidence of EGFR alterations in GBM makes inhibition of EGFR/EGFRvIII an attractive therapeutic approach. Depatuxizumab mafodotin (ABT-414) is an antibody-drug conjugate comprised of ABT-806, a mAB against EGFR, and a cytotoxic payload (monomethyl auristatin F). ABT-414 therapy initially showed promising results as an EGFRvIII therapy in vivo and in vitro; however, ABT414 failed to provide a survival benefit in phase I/II clinical trials, potentially due to therapeutic resistance. In this study, we seek to investigate the mechanisms of resistance to ABT-414 by performing whole exome, transcriptome and single cell RNA seq on ABT-414 resistant GBM PDX tumors. Our data showed an enrichment of mutations unique to the ABT-414 resistant tumors, including a point mutation (S466I) in TEK/TIE2 transmembrane angiopoietin receptor. In vitro expression of TEK S466I in GBM cells showed an increase in activation of ERK and STAT3 and increased TEK/TIE2 immunoprecipitation with EGFR compared to the wild-type TEK receptor. Furthermore, gene ontology analysis reveals that ABT-414-treated flank tumors exhibit increased activation of extracellular matrix organization and CNS developmental processes compared to flank tumors in the control treatment groups. ABT-414-treated tumors also demonstrate increased expression of inhibitor of differentiation (ID)1 and ID3, associated with stem-like phenotype in glioblastoma. Taken together, our data indicate that resistance to ABT-414 is mediated by both de novo mutations not detected in the parent tumor and adaptive dysregulation of pathways which may lead to dedifferentiation and therapeutic resistance.
CSIG-10. PLATELET-DERIVED GROWTH FACTOR RECEPTOR ALPHA ONCOGENE DEPENDENCY IN GLIOBLASTOMA
Authors: Berezovsky Artem , Datta Indrani , She Ruicong , Transou Andrea , Irtenkauf Susan , Hasselbach Laura , Poisson Laila , deCarvalho Ana
Published: November 2021

PDGFRA is the second most frequently amplified gene encoding receptor tyrosine kinase in adult glioblastoma (GBM), oftentimes as extrachromosomal elements (ecDNA). Our overall objective is to elucidate mechanisms underlying PDGFRα dependency in GBM tumor maintenance. We have isolated distinct subpopulations from a GBM model (HF3253), harboring two alterations in PDGFRA: constitutively active genomic rearrangement and extrachromosomal amplification, that differ in the frequency of PDGFRA ecDNA. HF3253 tumor growth rate correlates with the initial proportion of ecDNA+ population implanted. Furthermore, slower tumor growth is due to selection for initially low-frequency PDGFRA ecDNA amplified clones based on histology and TaqMan Copy Number assay. Further exploiting intra-tumoral heterogeneity, we have isolated single cell clones from bulk cells. Compared to bulk cells, single cell clones do not express PDGFRα, PDGFRA mRNA and exhibit diploid PDGFRA copy number. Tumor growth was reduced in 4 ecDNA(-) clones compared to parental ecDNA(+) (log-rank test p= 0.00772, 0.00379, 0.00076, 0.00379). In contrast to parental HF3253, ecDNA(-) tumors demonstrated diffuse tumor morphology and weak PDGFRα activation. HF3253 ecDNA(-) PDX tumors lack detectable PDGFRα. Correspondingly, HF3253 ecDNA(-) cell populations do not exhibit de novo PDGFRA copy number gains post-implant. We conducted paired, whole RNA-sequencing on 20 HF3253 populations (ecDNA+/-: 6 clones from 3 biological replicates PDXs and 4 clones from 4 in vitro technical replicates). Employing a false discovery rate of 0.05, we identified 785 differentially expressed genes. Platelet-derived growth factor binding (GO:0048407) and central carbon metabolism were down-regulated in ecDNA(-) while genes significantly associated with astrocytic processes were upregulated. We demonstrated the dependency on PDGFRα signaling in a patient-derived GBM model carrying ecDNA PDGFRA amplification. Our data validates PDGFRɑ as a therapeutic target in a subset of GBM patients and demonstrates that detection of ecDNA-amplified PDGFRA has the potential to be a predictive biomarker of future PDGFRɑ targeted therapies.
RADT-05. PROSPECTIVE LONG-TERM EVALUATION OF MRI- AND CLINICAL CHANGES FOLLOWING STEREOTACTIC RADIOSURGERY FOR BRAIN METASTASES – IS REPEAT SRS A CONSEQUENCE, OR ALSO A CAUSE OF LONG-TERM SURVIVAL?
Authors: Skeie Bente , Enger Per Øyvind , Skeie Geir Olve , Heggdal Jan Ingemann
Published: November 2021

The use of stereotactic radiosurgery (SRS) for brain metastases are increasing. Response assessment is challenging and the clinical significance of radiological response and retreatments are poorly defined. Ninety-seven patients with a total of 406 brain metastases were followed prospectively for 10 years or until death. Volume changes over time and clinical outcome in response to first time SRS and SRS retreatments were analyzed. Tumors grew significantly before (p = 0.004), but shrunk at 1 and 3 months (p = 0.001) following SRS. Four response-patterns of were observed; tumors either continuously reduced in size (A, 62%), pseudo-progressed (PP, B, 13%), temporarily reduced in size (C, 24%), or grew continuously (D, 2%); corresponding to 75% local control (LC) at initial SRS. Predictors for LC were primary cancer site (p = 0.001), tumor volume (p = 0.002) and target cover ratio (p = 0.005). Subsequent SRS for new lesions resulted in 94% LC (87% A) and repeat-SRS for local failures in 80% LC (57% B), predicted by higher prescribed dose, p = 0.001 and p = 0.042, respectively. Overall survival was only 4.5 months if A-response for all lesions, 13.3 months if at least one B-response, 17.1 months if retreated C- or D-response (p < 0.001), (7.5 and 4.7 months if untreated). Quality of life (p = 0.003), steroid use (p = 0.019) and prior whole brain radiotherapy (p = 0.026) were predictors for survival. There are 4 response patterns to SRS predicted by tumor size, primary cancer site, target cover ratio and prescribed dose. Long-term survivors experienced a higher incidence of PP and were more often retreated for new lesions and local failures. The immune response induced by PP seems beneficial but further studies are needed.
RADT-16. CLINICAL CHARACTERISTICS AND PROGNOSIS OF ADULT BRAIN STEM GLIOMA: A SINGLE-CENTER 10-YEAR RETROSPECTIVE STUDY OF 81 PATIENTS
Authors: Zhou Jiangfen , Lai Mingyao , Cai Linbo
Published: November 2021

OBJECTIVE

Adult brain stem glioma (ABSG) is a subset of brain tumor with a low incidence rate. This study reviewed the clinical characteristics and the risk factors affecting the prognosis of ABSG in a single center and explored the proper therapeutic mode for ABSG.

METHODS

The clinical data of adult patients (age over 18 years old) with brain stem gliomas from January 2010 to January 2021 of Guangdong Sanjiu brain hospital were retrospectively analyzed. Overall survival (OS) were determined by the Kaplan-Meier method, and Log-rank test was used for univariate analysis, COX proportion hazards regression was used for multivariate analysis. P < 0.05 was considered to be statistically significant.

RESULTS

Eighty-one ABSGs, including 46 males and 35 females, were analyzed. The median age of patients was 37 years (range, 19 to 67), and the median follow-up time was 17 months (range, 3 to 108) . The median OS of 81 patients was 18 months, and the OS for 1, 2, 3, and 5 years was 87.4%, 75.8%, 61.0%, and 36.5%, respectively. Univariate analysis demonstrated that the lesions enhancement on MRI, the WHO classifications, the expression status of H3K27M, radiotherapy status, and the status of adjuvant chemotherapy were related to prognosis. Multivariate Cox regression analysis revealed that age, the WHO classifications, radiotherapy status, and the maintenance chemotherapy followed radiotherapy were independent predictors for OS.

CONCLUSIONS

Radiotherapy is still the main treatment of ABSGs, and patients can be benefit from maintenance chemotherapy followed radiotherapy. The age > 40 years and WHO IV grade were two independent unfavorable prognostic factors. Research with expanded patient volume would help to further explore the influence of H3K27M expression on ABSG prognosis.
RADT-22. CONCURRENT TTFIELDS (200 KHZ) WITH CHEMORADIATION FOR PATIENTS WITH NEWLY DIAGNOSED GLIOBLASTOMA MAY INCREASE THE RATE OF PSEUDOPROGRESSION: ANALYSIS OF A PILOT CLINICAL TRIAL
Authors: Niazi Muneeb , Taylor James , Miller Ryan , Ali Ayesha S , Bar-Ad Voichita , Martinez Nina, L , Glass Jon , Alnahhas Iyad , Andrews David , Judy Kevin , Evans James , Farrell Christopher , Liu Haisong , Shi Wenyin
Published: November 2021

OBJECTIVE

The standard of care for the adjuvant treatment of glioblastoma is concurrent chemoradiation, maintenance temozolomide, and Tumor Treating Fields (TTFields). TTFields may reversibly impact the blood-brain barrier, most significantly at 100 kHz. We hypothesized that this may increase the rate of pseudoprogression (PsP) in patients who receive concurrent chemoradiation with TTFields (200 kHz).

METHODS

This is a single arm pilot study (clinicaltrials.gov Identifier: NCT03477110). Patients with newly diagnosed glioblastoma, age ≥ 18 years, and KPS ≥ 60 were eligible. They received concurrent temozolomide (75 mg/m2), scalp-sparing radiation (60 Gy in 30 fractions), and TTFields (200 kHz). Radiation was delivered through the TTFields arrays. PsP was defined as radiographic progression of enhancing lesions without clinical decline that improved or remained stable upon subsequent imaging. The rate of PsP was determined by an evaluation of the 2nd MRI at our multidisciplinary tumor board after the completion of trimodality treatment. These findings were confirmed with official radiology reports.

RESULTS

30 patients were enrolled. Of these, 29 had imaging available for evaluation. Male-to-female ratio was 20:10. Median follow-up was 11.6 months (1.6-22.4 months), median age was 58 years (19-77 years), and median KPS was 90 (70-100). 20 (66.7%) patients had unmethylated and 10 (33.3%) had methylated MGMT promotor. Median time from surgery to initiation of radiation was 34 days (26-49 days). Median time from completion of trimodality treatment to 2nd follow-up MRI was 90 days (29-109 days). 15/29 (51.7%) patients had PsP. Patients with methylated and unmethylated MGMT promotor had 50.0% (5/10) and 52.6% (10/19) rates of progression respectively.

CONCLUSIONS

51.7% of the patients who received concurrent chemoradiation with TTFields demonstrated PsP. The incidence is greater than historical reports. However, these findings should be explored in larger cohorts as this study was limited by a small sample size.
RADT-24. SYNTHETIC TREATMENT OF CENTRAL NERVOUS SYSTEM EWING/PRIMITIVE NEUROECTODERMAL TUMOR (EWING/PNET): A CASE REPORT
Authors: Yang yanying , Shan Changguo , Hong Weiping , Cai Linbo
Published: November 2021

Ewing/PNET is a rare tumor of the central nervous system. After the standard treatment, there’re still 86.7% of patients had recurrence and no standard treatment after recurrence. Here we report a case of Ewing/PNET with a good survival after synthetic treatment to provide evidence for future clinical strategies. A 23-year-old male underwent resection of the left frontal tumor on April 28, 2017, the pathological diagnosis was Ewing/PNET. He received whole brain radiotherapy 36Gy in 18 fractions, and tumor bed boost to 56Gy in 28 fractions, with 3 courses of Nedaplatin adjuvant chemotherapy. The tumor recured 23 months after the surgery. The patient underwent the second resection, followed by 4 courses of ADM+VCR+CTX/IE chemotherapy. However, 27 months after the first surgery, the tumor evaluation progressive resection of recurrent tumors in the anterior cranial base-ethmoid sinus. During the chemotherapy, MRI showed that tumor still increased. There was a mass in the root of the forehead and nose. After the third recurrence, the patient received re-radiotherapy (50Gy in 25 fractions) 29 months later after the first RT. The tumor was significantly reduced after radiotherapy. Physical examination showed that the sense of smell continued to weaken, the visual acuity was the same as before. 8 courses of VIT (Irinotecan, vincristine, temozolomide) were followed by second RT, tumor was assessed every 2 courses. 44 months after the first surgery, he suffered a third recurrence in spina cord. And then he received rescue RT (20Gy in 10 fractions) in the recurrent tumor. The tumor was reduced after local radiotherapy. He was undergoing follow-up till May 2021, And the OS is 49 months. In conclusion, the incidence of this disease is low, especially in adults. However, the prognosis is poor. Early detection, early operation, combined with radiotherapy and chemotherapy are promising to improve the efficacy of Ewing/PNET.
RADT-34. OLFACTORY PERCEPTION DURING PROTON RADIATION AND DIFFERENCES IN FREQUENCY OF OLFACTORY PERCEPTIONS BASED ON PROTON CRANIOSPINAL IRRADIATION TECHNIQUE FOR PEDIATRIC BRAIN TUMOR PATIENTS
Authors: Ioakeim-Ioannidou Myrsini , Erfani Parsa , Urell Tobias , Daartz Juliane , Berv julia , leahy Shannon , Fullerton Barbara , Bolton Rachel , Yock Torunn , Tarbell Nancy , Yeap Beow , MacDonald Shannon
Published: November 2021

BACKGROUND

Unusual olfactory perception has been reported during brain radiation treatments but is infrequent and does not typically interfere with the ability to deliver treatment or cause notable distress.

METHODS

We performed a retrospective review of 127 pediatric patients treated with proton radiation therapy (PRT) for primary brain tumors in a single institution between 2016-2021. Patients received PRT to the brain as part of craniospinal irradiation (CSI) followed by a boost to the brain. Proton CSI was delivered with 3D-CRT protons (n=53) or pencil beam scanning technique (PBS) (n=74). Within the PBS group, treatment delivery to the CSI utilized a single PA field (n=24) or two posterior oblique fields (n=50). We collected data on abnormal olfactory sensations, nausea/vomiting, and the use of medical intervention for those symptoms.

RESULTS

Our cohort included 80 males and 47 females. The median age of patients was 10 years old (range, 3 – 21). Seventy-one patients received concurrent chemotherapy. Prior to PRT, 31 patients were nauseous. During the radiation course, 104 patients developed worsening nausea while 63 patients reported episodes of emesis. Four patients vomited while receiving radiation. Seventeen patients reported olfactory perceptions during CSI. We found a higher rate of olfactory perception in patients treated with PBS (n=16, 22%) than 3D-CRT (n=1, 2%) (p=0.001) and, within the PBS group, patients treated with a single PA field (n=11, 46%) than two oblique fields (n=5, 10%) (p=0.002). Seventy-eight patients required intervention including addition of anti-emetic or anti-anxiety medication. Two patients required sedation due to the malodorous smell during CSI. We did not find any significant difference in nausea/vomiting based on treatment technique.

CONCLUSIONS

PBS and PBS technique influence olfactory perceptions but not the occurrence of the rate of nausea/vomiting. Further studies should be performed to validate these findings and determine techniques to minimize unpleasant olfactory perceptions.
CTIM-23. EVIDENCE OF T CELL ACTIVATION AND INTRATUMORAL NIVOLUMAB-PRESENCE IN GLIOBLASTOMA PATIENTS TREATED WITH NIVOLUMAB AND BEVACIZUMAB
Authors: Skadborg Signe , Maarup Simone , Draghi Arianna , Borch Annie , Svane Inge Marie , Hasselbalch Benedikte , Poulsen Hans , Lassen Ulrik , Hadrup Sine
Published: November 2021

Glioblastoma (GBM) is an aggressive brain tumor with a dismal prognosis. Salvage neurosurgical resection is performed if possible and GBM patients are hereafter treated with Stupp’s regime as standard treatment in the primary setting. However, after relapse, treatment in the recurrent setting shows very limited effect. We are monitoring the immune system of patients participating in a phase II clinical trial, where patients with recurrent GBM receive Nivolumab and Bevacizumab, treatments blocking PD1 and VEGF, respectively. The clinical trial consists of two arms. Arm A includes patients where surgical removal of the tumor is possible, and arm B includes patients who are only able to receive medical treatment. Arm A has received Nivolumab 7 days prior to surgery. Single cells suspension was produced from the resected tumors and blood samples was collected from patients through the course of treatment, wherefrom PBMCs (peripheral blood mononuclear cells) were purified. All samples were immunophenotyped using multi-color flow cytometry, to identify and follow the distribution of various immune cell types, and determine their expression of activating and inhibitory molecules over the course of treatment, in the periphery and in the tumor. An activated subset of T cells was characterized by CD103 (tissue residence), CD39 (antigen exposure) and CD69 (cytotoxicity). Such T cell populations were significantly enriched in the tumor. Importantly, we could demonstrate the presence of Nivolumab in the tumor, using an anti-IgG4 antibody to detect Nivolumab binding to T cells. We observed IgG4 positive T cell in the tumor digest, suggesting T cells binding Nivolumab are present in the tumor. Additional data analysis will be performed prior to the conference. With this we hope to gain further knowledge of the immune system’s role in tumor clearance in the brain and the impact of immunotherapy hereupon.