bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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 &lt; 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

Abstract

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 &lt; 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 &gt; 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

Abstract

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.