bluuebunny/crossref_metadata_2025_split huggingface dataset:
CSIG-06. PLATELET DERIVED GROWTH FACTOR RECEPTOR ALPHA AS AN ONCOGENIC DRIVER IN GLIOBLASTOMA
Authors: Berezovsky Artem , Irtenkauf Susan , Transou Andrea , Hasselbach Laura , Mikkelsen Tom , de Carvalho Ana 
Published: December 2020

Abstract
Activated platelet derived growth factor receptor alpha (PDGFRα) is essential for the maintenance of oligodendrocyte progenitors. Differential signaling results from phosphorylation of specific tyrosine residues in the kinase insert (KI) domain present in most RTKs in variable length. Our goal is to identify the molecular contexts in which PDGFRA activation is an essential driver for maintenance of the malignant phenotype in glioblastoma. RNA sequencing was conducted on 13 glioblastoma mouse orthotopic PDXs (n=3/line). PDGFRA mRNA overexpression was observed for 3 glioblastomas: one carrying PDGFRA extrachromosomal (ecDNA) amplification (HF3253) and two non-amplified (Tukey p=0.41, 0.19). Corresponding PDGFRα KI activation (pY754) was observed only for HF3253. To assess activation as an adaptation to microenvironmental pressures, pY754 was quantified by reverse phase protein array on 4 growth conditions (normal, -growth factors, two serum concentrations) for 8 neurospheres. PDGFRɑ activation was highest in growth factor-depleted conditions in the absence of exogenous ligand (Tukey p=0.02). Taking advantage of genomic heterogeneity in HF3253, we isolated cellular lineages with divergent frequencies of PDGFRA ecDNA. PDGFRA copy number (TaqMan) decreased longitudinally. PDX tumors from higher passage had slower tumor growth due to strong selection for initial low frequency PDGFRA ecDNA-amplified clones. IHC showed that the tumors had comparably high total and activated PDGFRα to low passage tumors. Further exploiting intra-tumoral heterogeneity, we have isolated single cell clones. Tumor growth was reduced in 2 ecDNA(-) tumors compared to parental ecDNA(+) (log-rank test p= 3e-3, 1e-3). In contrast to parental, ecDNA(-) tumors demonstrated diffuse tumor morphology and weak PDGFRα activation. The staining index (mean intensity x area) for the ecDNA(-) clones was significantly lower than the ecDNA(+) (1-wayANOVA p=2e-16). We established dependency on PDGFRα signaling in a patient-derived glioblastoma model. Our data demonstrates that detection of ecDNA-amplified PDGFRA has the potential to be a predictive biomarker of future PDGFRɑ-targeted therapies.
CSIG-13. TRPM7 INDUCES TUMORIGENESIS AND STEMNESS THROUGH NOTCH ACTIVATION IN GLIOMA
Authors: Wan Jingwei , Guo Alyssa , Liu Mingli 
Published: December 2020

Abstract
Our group found that the inhibitory effect of TRPM7 on proliferation and invasion of human glioma cell is mediated by multiple mechanisms. TRPM7 regulates miR-28-5p expression, which suppresses cell proliferation and invasion in glioma cells by targeting Ras-related protein Rap1b. In particular, our group found that TRPM7 channels regulate glioma stem cell (GSC) growth/proliferation through STAT3 and Notch signaling. However, which Notch component(s) is crucial for its activity regulated by TRPM7, and its relationship with other GSC markers, such as CD133 and ALDH1, remain unclear. In the current project, we elucidate the mechanisms of TRMP7’s regulation of Notch signaling pathway that contribute to the development and progression of glioma and maintenance of self-renewal and tumorigenicity of GSC using multiple glioma cell lines (GC) with different molecular subtypes and GSCs derived from the GC lines. 1) We first analyzed TRPM7 expression using the Oncomine database (https://www.oncomine.org) and found that the TRPM7 mRNA expression is significantly increased in anaplastic astrocytoma, diffuse astrocytoma, and GBM patients compared to that in normal brain tissue controls. 2) TRPM7 is expressed in GBM, and its channel activity is correlated with Notch1 activation. Inhibition of TRPM7 downregulates Notch1 signaling, while upregulation of TRPM7 upregulates Notch1 signaling. 3) GSC markers, CD133 and ALDH1, are correlated with TRPM7 in GBM. 4) Targeting TRPM7 suppresses the growth and proliferation of glioma cells through G1/S arrests and apoptosis of glioma cells. 5) Targeting Notch1 suppresses the TRPM7-induced growth and proliferation of glioma cells, as well as the expression of GSC markers CD133 and ALDH1. In summary, TRPM7 is responsible for sustained Notch signaling activation, enhanced expression of GSC markers, and regulation of glioma stemness, which contribute to malignant glioma cell growth and invasion. Notch1 and ligand DII4 are key components that contribute GSC stemness.
CSIG-16. SEXUAL DIMPORHISM IN IRON ACQUISITION IN GLIOBLASTOMA
Authors: Pandya Bhavyata , Slagle-Webb Becky , Nesterova Darya , Zacharia Brad , Lathia Justin , Rubin Joshua , Berens Michael , Barnholtz-Sloan Jill S , Connor James 
Published: December 2020

Abstract
Glioblastoma (GBM) is the most aggressive brain cancer. Sex differences in incidence and clinical outcomes have been reported, however, our knowledge of contributing mechanisms is limited. Iron acquisition is key to robust tumor growth. Upregulation of Transferrin (Tf, iron transport protein)/Transferrin receptor (TfR) is found in multiple different cancers. We have identified H-ferritin (FTH1) as involved in iron transport and explore its uptake in GBM in this study. We interrogated iron uptake in a syngeneic orthotopic mouse model (GL261 cells) using male and female mice. After the tumors were established, radioactive 125I labeled Tf and FTH1 proteins were injected retro-orbitally in the mice. After 24 hours, tumors were removed, homogenized and analyzed for Tf and FTH1 uptake. There was a significant difference in Tf uptake into the tumor versus matched non-tumor tissue in both males and females and the uptake in the tumors was 1.5-fold higher in males than females. There was no significant difference in FTH1 uptake between male and female tumors nor between tumor and matched non-tumor brain tissue. Binding analyses were performed on homogenized samples of human male and female GBM tissue samples using 125I labeled Tf and FTH1. Tumors from males had increased binding of both proteins compared to tumors from females. We next queried the TCGA database and found in females, high TfR expression was associated with poor survival but not in males. TCGA database revealed a robust expression of Tim1, a putative receptor for FTH1, but its expression did not relate to survival. In summary, this study demonstrates FTH1 binding to GBMs and sexual dimorphism in iron acquisition via Tf and survival.
CSIG-18. CALCIUM COMMUNICATION IN GLIOMA: CRUCIAL PACEMAKER CELLS GOVERN TUMOR PROGRESSION
Authors: Hausmann David , Jung Erik , Azorin Daniel , Ratliff Miriam , Osswald Matthias , Wick Wolfgang , Winkler Frank 
Published: December 2020

Abstract

BACKGROUND
Gliomas form therapy-resistant multicellular networks, using neurite-like protrusions (called Tumor Microtubes [TMs]), and display intercellular calcium transients, that drive brain tumor malignancy.

METHODS
A refined in vitro model was established to study calcium communication and its molecular toolkit in patient-derived glioma cells. In vitro results were then validated with longitudinal in vivo two-photon calcium imaging in awake mice.

RESULTS
Here we first describe the discovery of a small subpopulation of glioma cells that display intrinsically active calcium oscillations and behave like pacemakers. Accordingly, these pacemaker-like glioma cells trigger synchronized calcium activity in tumor cells that are connected with them via TMs. The application of network theory shows that glioma cell networks follow a scale-free and small-world topology, governed by a subpopulation of highly connected hub cells. Interestingly, the pacemaker cells most often act as these hubs, hence communicating with many other network members. Graph theory predicts that such network design displays a high degree of robustness, making it resistant to random damage as seen after radio- and chemotherapy – but extremely vulnerable to selective damage to key hubs. In line with this theory, laser ablation of the pacemaker-like hub cells splintered the malignant tumor network into small isolated cell clusters and led to increased cell death, whereas laser ablation of random tumor cells showed no effect. Among others, KCNN4 channels, which are upregulated in gliomas, were identified as drivers of the pacemaker-like hub cells. Suppressing their pacemaking-abilities by KCNN4 inhibition strongly reduced calcium communication and tumor growth.

CONCLUSION
In summary, coordinated calcium communication in glioma drives brain tumor malignancy. A specific tumor cell subpopulation was identified that acts as hubs of the multicellular network and initiates global calcium activity. The network’s vulnerability to loosing these pacemaker-like hub cells suggests a novel targeted approach against the resistant networks of gliomas.
CSIG-19. THE DEUBIQUITINASE BRCC3 LINKS ALT TELOMERES TO SUPPRESSION OF INNATE IMMUNITY IN IDH1-MUTANT GLIOMA
Authors: Mukherjee Joydeep , Tang Yongjian , Johanessen Tor-Christian , Pandita Ajay , Ohba Shigeo , Cahill Daniel , Pieper Russell 
Published: December 2020

Abstract
Approximately 10% of tumors including all IDH1-mutant lower-grade glioma resolve telomeric shortening using Alternative Lengthening of Telomere (ALT) mechanism. Although the ALT process lengthens telomeres, it also generates small bits of extrachromosomal, telomere-containing DNA (ECTRs). These ECTRs can bind and activate cyclic GMP-AMP synthase (cGAS), the major cytosolic sensor of double-stranded DNA, which in turn can activate expression of stimulator of IFN genes (STING) and the interferon-based innate immune response. To limit the immune response, ALT cells inactivate the cGAS-STING pathway, although the mechanism by which this occurs is unknown. Here we show that the deubiquitinase BRCC3 links ALT telomeres to suppression of the cGAS-STING pathway and the innate immune response. Astrocytoma cells dependent on the ALT-mechanism (IDH1-mutant and ATRX-deficient genetically-modified human astrocytes and MGG119 PDX) contained ECTR and had reduced expression of the cGAS and the downstream components of the cGAS-STING pathway (STING, and IFN-β) relative to matched non-ALT (isogenic ATRX WT astrocytes and MGG152 PDX) cells lacking ECTRs. Decreased levels of cGAS in ALT cells were in turn associated with deubiquitiantion and destabilization of cGAS. The telomere-derived ECTR in ALT-dependent cells lacked two proteins normally found in ALT telomeres (TRF2 or PARP), but retained two other proteins, Mre11 and its binding partner, normally nuclear deubiquitinase BRCC3. Furthermore, either pharmacologic inhibition or genetic suppression of BRCC3 levels had no effect on ECTR levels but stabilized cGAS and activated the cGAS-STING pathway. This cGAS-mediated activation could be blocked by exogenous expression of WT BRCC3, but not by expression of a mutant BRCC3 incapable of deubiquitination. These results show that BRCC3 translocated along with ECTRs to the cytoplasm degrades cGAS and protects ALT-dependent cells from activating the innate immune response. The BRCC3-controlled cGAS-STING pathway may therefore represent a therapeutically targetable means to enhance the immune response in IDH1-mutant lower grade glioma.
CSIG-22. CANCER-ASSOCIATED MISSENSE SINGLE NUCLEOTIDE VARIANTS REGULATE THE STABILITY AND SUBCELLULAR LOCALIZATION OF NF2/MERLIN
Authors: Eaton Charlotte , Bisignano Paola , Raleigh David 
Published: December 2020

Abstract

BACKGROUND
Alterations in the NF2 tumor suppressor gene lead to meningiomas and schwannomas, but the tumor suppressor functions of the NF2 gene product, Merlin, are incompletely understood. To address this problem, we performed a structure-function analysis of Merlin by expressing cancer-associated missense single-nucleotide variants (mSNVs) in primary cancer cells for biochemical and cell biology experiments.

METHODS
All NF2 mSNVs were assembled from cBioPortal and COSMIC, and modelled on the FERM, a-helical, and C-terminal domains of Merlin (PDB 4ZRJ) using comparative structure prediction on the Robetta server and visually inspected using Pymol. mSNV hotspots were defined from sliding windows with at least 10 mutations within 5 residues in either direction. mSNVs from hotspots in meningiomas, schwannomas, or both, were selected for in vitro mechanistic analyses using immunofluorescence and immunoblotting of whole cell, plasma membrane, cytoskeletal, cytoplasmic, nuclear, and chromatin subcellular fractions from M10G meningioma cells and HEI-193 schwannoma cells.

RESULTS
We identified the following cancer-associated hotspot mSNVs in NF2, which were over-expressed for mechanistic studies: L46R, S156N, W191R, A211D, V219M, R418C and R462K. Endogenous Merlin was detected in all subcellular compartments, but was enriched in the nucleus. L46R and A211D mapped to hydrophobic pockets in the FERM domain, destabilized Merlin, and excluded Merlin from all subcellular compartments except the cytoskeleton. S156N, W191R and V219M also mapped to the FERM domain, but did not affect Merlin stability, and V219M attenuated chromatin localization, suggesting this motif may be involved in binding events that regulate subcellular localization. R418C and R463K mapped to the a-helical domain, but only R418C destabilized Merlin.

CONCLUSION
Our results suggest that cancer-associated mSNVs inactive the tumor suppressor functions of NF2 by altering the stability, subcellular localization, or binding partners of Merlin. Further work is required to identify and understand the impact of binding partners and subcellular localization on Merlin function.
CTIM-12. RANDOMIZED PHASE 2 STUDY OF NIVOLUMAB (NIVO) PLUS EITHER STANDARD OR REDUCED DOSE BEVACIZUMAB (BEV) IN RECURRENT GLIOBLASTOMA (rGBM)
Authors: Ahluwalia Manmeet , Peereboom David , Rauf Yasmeen , Lathia Justin , Alban Tyler , Schilero Cathy , Ciolfi Marci , LaForest-Roys Corey , Nayak Lakshmi , Lee Eudocia , Wen Patrick , Reardon David 
Published: December 2020

Abstract

BACKGROUND
Trials with anti-PD1 in rGBM have shown limited efficacy. VEGF is highly upregulated proangiogenic growth factor in GBM contributing to tumor-associated immunosuppression. Preclinical data suggests a potential dose effect of anti-VEGF therapy on immunomodulation. Hence, a combination of anti-PD1 and anti-VEGF may be a promising approach in rGBM.

METHODS
90 patients with first-recurrent GBM were randomized (1:1) to nivolumab (240 mg IV Q2 weeks) and bevacizumab at standard (10 mg/kg; Arm A) or low dose (3 mg/kg; Arm B) IV Q2 weeks. Eligibility also required KPS≥ 70% and dexamethasone ≤ 4 mg/day. Stratification included extent of resection, age, performance status and MGMT methylation status. Single cell RNA sequencing with CITE-seq was used to analyze blood samples from pre- and 8 weeks post-treatment among 8 responders and 8 non-responders.

RESULTS
90 patients were enrolled (May 2018- Jan 2020) and median follow-up is 7.5 months. Characteristics in 2 arms were comparable. Median age was 60.5 years (range 27–86), median KPS was 80. 35 patients were MGMT methylated, 53 unmethylated and 2 indeterminate. Estimated progression free survival (PFS) and median overall survival (OS) in arm A are 6.13 and 10.85 months and 4.59 and 9.61 months in Arm B, respectively. Single cell RNA sequencing with CITE-seq was used to analyze blood samples from 16 patients, baseline and 8 weeks post treatment. Standard dose bevacizumab treated patients had decreased myeloid derived suppressor cells and an inflammatory response gene signature at 8 weeks. Most frequent toxicities included fatigue (52.8%), headache (32.6%), diarrhea (31.5%), proteinuria (25.8) and hypertension (23.6%). Toxicity was comparable between 2 arms, except hypertension was more common in arm A.

CONCLUSIONS
PFS and OS rates appear similar for nivolumab with either standard or low-dose bevacizumab compared to historical benchmarks of bevacizumab monotherapy. Ongoing response evaluation and immunocorrelative data will be presented.
CTIM-24. AUTOLOGOUS CD34+ ENRICHED HEMATOPOIETIC PROGENITOR CELLS GENETICALLY MODIFIED FOR HUMAN INTERFERON-α2, ARE WELL TOLERATED & RAPIDLY ENGRAFT IN PATIENTS WITH GLIOBLASTOMA MULTIFORME (TEM-GBM_001 STUDY)
Authors: Finocchiaro Gaetano , Gentner Bernhard , Eoli Marica , Francesca Farina , Anghileri Elena , Girlanda Stefania , Carrabba Matteo , Cuccarini Valeria , DiMeco Francesco , Legnani Federico , Pollo Bianca , Bruzzone Maria Grazia , Saini Marco , Ferroli Paolo , Capotondo Alessia , Paterra Rosina , Garramone Mariagrazia , Mazzoleni Stefania , Zambanini Andrew , Russo Carlo , Naldini Luigi , Ciceri Fabio 
Published: December 2020

Abstract
GBM with an unmethylated MGMT gene promoter is associated with very poor prognosis. A subset of tumor associated macrophages expressing the angiopoietin receptor Tie2 (TEMs) can be genetically modified for local & tumor restricted release of interferon-α2 (IFN). IFN has antitumor effects, inhibits angiogenesis & modulates the immune system. Temferon consists of autologous HSPCs transduced ex-vivo with an LVV encoding an IFN gene & expression control sequences for TEMs. TEM-GBM is an open-label, Phase I/IIa study (Part A: 3x3x3 dose escalation; Part B: n=12), & Temferon (single dose) is given to patients with first diagnosis of GBM & unmethylated MGMT promoter. Part A 3rd cohort is ongoing & completes dosing in September 2020. Eight patients completed screening; one patient died (disease progression) before Temferon was administered. Six patients received Temferon (3 women, 3 men, mean age 52.3 years). Cohort 1 received Temferon 0.5x106 cells/kg & Cohort 2, 1x106 cells/kg. Neutropenia & thrombocytopenia occurred as expected following conditioning & hematologic recovery (HR) occurred median D+13. Transduced PBMCs were identified by vector copy number (VCN) on myeloid cells at HR & at later timepoints. In general, a dose-ordered increase in VCN was observed (mean VCN D+30 CD14+ Cohort 1: 0.094, cohort 2: 0.125); 1 patient in each cohort had low VCNs. VCN remained detectable up to recent follow up visits (≤ D+180). No dose-limiting toxicities have been reported. Four SAEs occurred in 3 patients who received Temferon (pneumonia, pulmonary embolism, febrile neutropenia, fatigue) but these events were not attributed to Temferon, resolved, & may have been related to the conditioning regimen (carmustine & thiotepa). Disease progression has been confirmed in 3 patients who received Temferon. These preliminary results indicate feasibility of engrafting a pre-determined fraction of Temferon cells in the bone marrow of GBM patients without, so far, causing dose-limiting toxicity.
CTIM-31. USE OF A SINGLE PEPTIDE CHECKPOINT INHIBITOR FOR TREATMENT OF CENTRAL NERVOUS SYSTEM TUMORS
Authors: Moertel Christopher , Xiong Zhengming , Zellmer David , Pluhar Elizabeth , Neil Elizabeth , Greengard Emely , Olin Michael 
Published: December 2020

Abstract
Cancer immunotherapy has revolutionized clinical management of malignancies by generating long-term, durable control of tumors. Unfortunately, these therapies often cause serious immune-related adverse events. In addition, only a small percentage of solid tumors respond to these therapies and there is little efficacy in CNS tumors. Our research is focused on the CD200 immune checkpoint, which modulates the immune system through the inhibitory receptor (CD200R1) and activation receptors (CD200AR). We demonstrated that targeting the CD200AR with a checkpoint peptide ligand (CD200AR-L) activates the immune system and renders it impervious to the inhibitory effects of CD200. In a pre-clinical canine spontaneous high-grade glioma trial, CD200AR-L, with autologous tumor lysate vaccination, resulted in a 20% two-year progression-free survival; no toxicities or adverse effects were observed. We suggest this result was due to the ability of the CD200AR-L to modulate multiple immune checkpoints. During the characterization of the CD200AR-L, we discovered signaling molecules are shared by the CD200 and PD-1/PD-L1 checkpoint pathways, suggesting these immune checkpoints are connected. Our preliminary studies demonstrated that the inhibitory CD200R1 and PD-1 mediate immune checkpoint signaling activities through the SHIP1/2. Moreover, CD200AR-L overpowers the suppressive effects of CD200 and PD-L1, which are both shed by tumors, by downregulating the inhibitory CD200R1 and PD-1 on both antigen-presenting cells (APC) and T-cells. In addition, CD200AR-L downregulates PD-1 on APCs and inhibits the upregulation of PD-L1 and CTLA4. These studies led to the discovery that the novel peptide modulates the CD200, PD-1/PD-L1 and CTLA-4 pathways, providing the basis for the translatable development of a CD200-directed peptide for clinical use against multiple tumors including gliomas. These studies led to FDA approval of this peptide for the first in human phase I single center, open-label, dose-escalation clinical trial in adult and pediatric trial for children with recurrent malignant brain tumors.
CTNI-04. ACTIVITY OF LAROTRECTINIB IN TROPOMYOSIN RECEPTOR KINASE (TRK) FUSION CANCER PATIENTS WITH CENTRAL NERVOUS SYSTEM (CNS) METASTASES
Authors: Patel Jyoti D , Farago Anna F , Hong David S , Lassen Ulrik N , Leyvraz Serge , Park Keunchil , Sohal Davendra P S , Solomon Benjamin , Reeves John A , Dima Laura , Brega Nicoletta , Drilon Alexander 
Published: December 2020

Abstract

BACKGROUND
NTRK gene fusions occur in a range of tumor types, including those with CNS metastases. Larotrectinib, a highly selective FDA- and EMA- approved TRK inhibitor, demonstrated an objective response rate (ORR) of 79% across various cancers (Hong et al. Lancet Oncol. 2020). We report data on patients with TRK fusion cancer with CNS metastases treated with larotrectinib.

METHODS
Patients with solid tumors with CNS metastases at baseline harboring an NTRK gene fusion enrolled in two clinical trials (NCT02122913 and NCT02576431) were identified. Response was assessed by the investigator per RECIST v1.1.

RESULTS
As of July 15, 2019, 14 patients with CNS-metastases were enrolled: lung cancer (n=7), thyroid cancer (n=4), melanoma (n=2), and non-secretory breast cancer (n=1). Median age was 53 years (range 25–76). Including all sites of disease, the ORR was 71% (95% CI 42–92%): ten patients had a partial response (PR), two had stable disease (SD), and two had progressive disease (lung and melanoma). Of the three patients with measurable intracranial disease at baseline, the best intracranial response was 1 complete response, 1 PR, and 1 SD. Median duration of response for all patients was 14.8 months (range 1.9+ to 17.4+), median progression-free survival was 9.9 months (range 1.4 to 19.3+), and median overall survival was 27.8 months (range 1.4+ to 27.8). Treatment duration ranged from 1.4 to 25.0 months; six patients continued treatment beyond progression (lasting between 0.1+ and 8.5 months). Treatment-emergent adverse events (TEAEs) were mainly Grade 1 and 2; Grade 3 TEAEs occurred in seven patients (50%), with one (myalgia) attributed to larotrectinib (7%). There were no Grade 4 TEAEs.

CONCLUSIONS
Larotrectinib was highly active and well tolerated in TRK fusion cancer patients with CNS metastases. These results support testing for NTRK gene fusions across all cancers, including in patients with CNS metastases.