bluuebunny/crossref_metadata_2025 huggingface dataset:
SCIDOT-50. A RAT MODEL FOR LASER INTERSTITIAL THERMAL THERAPY FOR GLIOBLASTOMA: EFFECTS ON PERI-ABLATION BLOOD-BRAIN BARRIER AND IMPLICATIONS FOR POST-ABLATION CHEMOTHERAPY
Authors: Nagaraja Tavarekere , Ewing James , Farmer Katelynn , Valadie Grahm , Brown Stephen , Knight Robert , Cabral Glauber , Panda Swayamprava , Lee Ian
Published: November 2019

Laser interstitial thermal therapy (LITT) is a minimally invasive tumor cytoreductive treatment for recurrent gliomas, brain tumors in eloquent regions or otherwise inaccessible to traditional open surgery. LITT offers quicker recovery and shorter hospital stays as additional advantages. A laser fiberoptic catheter is positioned in the body of the tumor under magnetic resonance imaging (MRI) guidance via a twist drill hole in the skull. Using MR thermometry, the tumor is ablated by laser heating to lethal temperatures. The peri-ablation zones get heated to sub-lethal temperatures and subsequently recover. It has been reported in humans that opening of the blood-brain barrier (BBB) occurs, lasting several weeks after ablation. We have adapted Visualase®, a clinically available LITT system, for use in a rat glioblastoma model. Athymic female rats (n=7) were implanted with U251 tumor cells in one brain hemisphere. Tumor growth was monitored using MRI. When tumors reached about 4 mm in diameter, they were ablated under supervision of MR diffusion-weighted MRI, sparing the surrounding normal brain tissue. Contrast-enhanced MRI data were obtained before LITT, immediately after and at post-LITT 24 h. The brains were processed for histopathology and stained with hematoxylin and eosin (H&E) for visualizing the extent of the tumor and for major histocompatibility complex (MHC) to identify the human-derived U251 cells. All rats survived the LITT procedure. A ring of contrast enhancement around ablation perimeter was observed immediately after, and also at 24 h. H&E data showed near-complete ablation of the tumors. However, MHC staining showed U251 cells still remaining in the ablation vicinity. These data suggest this model is useful for examining the temporal and spatial development of peri-ablation BBB opening following LITT. Concurrent timing of post-ablation chemotherapy to the development and presence of post-LITT BBB opening may aid in efficient targeting of remaining tumor cells.
EXTH-49. THERAPEUTIC EFFICACY OF ENGINEERED, HYDROGEL ENCAPSULATED BIMODAL MSC IN GLIOBLASTOMA STRATIFIED ON CELL SURFACE RECEPTOR EXPRESSION
Authors: Bhere Deepak , Hugh Choi Sung , van de Donk Pim , Khalsa Jasneet , Hope David , Gortzak Kiki , Kunnummal Amina , Reinshagen Clemens , Ling Huan , Vasdev Neil , Ibn Essayed Walid , Golby Alexandra , Bi Wenya , Lowe Alarice , Wakimoto Hiroaki , Revai Lechtich Esther , Shah Khalid
Published: November 2019

Engineered stem cell therapeutics present a promising therapeutic strategy for glioblastoma (GBM). However, their clinical translation in GBM patients is limited due to lack of mouse models that mimic clinical GBM scenario, dearth of stratification techniques for target cohorts and safety concerns. In this study, we have validated the potential of stratifying therapy responders based on a circulating tumor cell screen and developed a unique “off-the-shelf” cell surface receptor targeted engineered bi-functional mesenchymal stem cell (MSC) for resected GBMs. We created a dual promoter self-inactivating lentiviral vector plasmid encoding death receptor (DR4/5) ligand (DRL), the tumor specific therapeutic agent and the prodrug-converting enzyme, herpes simplex virus-thymidine kinase (HSV-TK) and engineered clinical grade human bone marrow derived MSC to express the bi-modal therapeutic. We show that hyaluronic acid (HA) hydrogel encapsulated bimodal MSC are retained in the tumor resection cavity and have significant therapeutic efficacy in vitro and in vivo in mice bearing patient derived GBM tumors following DR4/5 stratification by circulating tumor cells in the blood and GBM surgical resection. We also show that fate of engineered MSC can be tracked by PET imaging and activation of pro-drug, HSV-TK enhances the therapeutic efficacy of MSC and results in their elimination post-tumor treatment. Our study reveals that local delivery of hydrogel encapsulated engineered MSC has therapeutic benefits; circumvents concerns of bio-distribution, increases on-site retention and permits tumor-selective migration. Based on this data, we are preparing for a first-in-human study of a hydrogel encapsulated engineered allogeneic MSC product, in primary GBM patients.
ANGI-08. AN ANNEXIN A2-REGULATED PHENOTYPIC SHIFT IN GLIOMA
Authors: Matsumoto Yuji , Ichikawa Tomotsugu , Kurozumi Kazuhiko , Otani Yoshihiro , Fujimura Atsushi , Fujii Kentaro , Shimazu Yosuke , Tomita Yusuke , Hattori Yasuhiko , Uneda Atsuhito , Tsuboi Nobushige , Kaneda Keisuke , Makino Keigo , Date Isao
Published: November 2019

BACKGROUND

Malignant glioma has a poor prognosis and is characterized by excessive proliferation, invasion, and angiogenesis. Previously, we established subclones of glioma cell lines with different invasive phenotypes to investigate the mechanisms of invasion in this malignancy. That study revealed annexin A2 (ANXA2) as an activator of angiogenesis and perivascular invasion. Here, we investigated the molecular mechanism of the phenotypic shift in glioma that is induced by ANXA2.

METHODS

We identified ANXA2 target genes using microarray analyses of our four established cell lines and RNA-seq data from the IVY Glioblastoma Atlas Project. Co-expression was then confirmed in human glioma cells. Additionally, qRT-PCR, immunoblotting, invasion assays, proliferation assays, and tube formation assays were performed to uncover the specific roles of these angiogenic invasion-related genes. Furthermore, we examined survival times and phenotypic shifts in vivo.

RESULTS

We identified oncostatin M receptor (OSMR) as an ANXA2-target gene using microarray and RNA-seq, and confirmed its expression correlated with ANXA2 in glioma cells. ANXA2-overexpressing glioma cells showed enhanced OSMR expression and STAT3 phosphorylation, while STAT3 knockdown reduced OSMR expression. When ANXA2 was overexpressed in glioma cells, invasion, angiogenesis, proliferation, and epithelial-mesenchymal transition were promoted; however, silencing OSMR attenuated the ANXA2-induced phenotypic shift. In vivo, ANXA2-overexpressing glioma cells shortened the survival time of tumor-bearing mice, whereas OSMR knockdown increased survival times.

CONCLUSIONS

We analyzed genes whose expression was regulated by ANXA2 in glioma using invasive glioma models. Through this analysis, we identified that ANXA2 and OSMR regulate a phenotypic shift, suggesting that OSMR could be a promising target to treat and prevent glioma invasion.
RARE-49. SEX-SPECIFIC SURVIVAL ANALYSIS IDENTIFIES DIFFERENTIAL CLUSTERS OF PROGNOSTIC RELEVANCE IN PATIENTS WITH PRIMARY CNS LYMPHOMA
Authors: Roetzer Thomas , Nenning Karl-Heinz , Furtner Julia , Seebrecht Lukas , Gesperger Johanna , Woehrer Adelheid
Published: November 2019

Sex-specific differences are increasingly recognized in various diseases but have not yet been investigated for patients with primary CNS lymphoma (PCNSL). We collected clinical information and MR-images from 130 patients with PCNSL (66 f/ 64 m). We segmented MR-images into contrast-enhanced tumor, necrosis and edema for volumetric analysis and additionally quantified anti-PCNSL immune response using anti-CD3 staining in 67 cases. Median overall survival was 10 months for females and 8 months for males (p=0.979). Sex-specific Cox-regression analyses implicated age, performance and immunodeficiency as significant prognostic markers in females, whereas only age remained as significant marker in males. We then performed cluster analyses for females (fC) and males (mC) with complete sets of clinical, imaging, and tissue phenotypes (n=55). In females, two main clusters emerged that were mainly driven by clinical performance with fC1 (n=14) featuring patients with better performance (most of whom received MTX) compared to fC2 (n=18; mOS 21 vs 3 months, p< 0.01). fC2 resolved into two subclusters with better outcome for fC2a based on larger enhancing tumor volume and high immune response (mOS 12 vs. 1 months, p< 0.01). In males, two major clusters emerged (16 vs 7 patients, mOS 5 vs 23 months, p=0.414).), which differed mainly according to treatment approach with higher prevalence of MTX-chemotherapy in mC1. Each cluster could be subdivided into 2 subclusters based on differences in clinical performance in mC1, or according to treatment strategy, i.e., combined chemo-radiotherapy vs radiotherapy-only or best supportive care (mOS 49 vs 2 months, p=0.12) in mC2. In summary, we find prognostically relevant sex-specific clusters in patients with PCNSL that implicate differential roles of tumor-related contrast enhancement and immune response in female versus treatment modality in male patients. Initial differences in cluster-defining factors need further validation in independent cohorts but might have implications for differential patient management.
CBMT-08. IN VIVO EVALUATION OF PENTOSE PHOSPHATE PATHWAY ACTIVITY IN ORTHOTOPIC GLIOMA USING HYPERPOLARIZED δ-[1-13C]GLUCONOLACTONE
Authors: Batsios Georgios , Viswanath Pavithra , Cao Peng , Taglang Celine , Subramani Elavarasan , Flavell Robert , Larson Peder , Ronen Sabrina
Published: November 2019

The pentose phosphate pathway (PPP) generates NADPH and ribose 5-phosphate, which are involved in the scavenging of reactive oxygen species and the synthesis of nucleotides. As such, the PPP is typically upregulated in cancer cells to address the metabolic needs of rapid cell proliferation. Imaging PPP upregulation could therefore be useful in tumor assessment. One intermediate of the pathway is 6-phospho-δ-gluconolactone (6P-δ-GL), which is produced by phosphorylation of δ-gluconolactone. 6P-δ-GL is further metabolized to 6-phospho-gluconate (6PG). The goal of our study was to evaluate, for the first time, whether hyperpolarized (HP) δ-[1-13C]gluconolactone can be used to assess PPP flux and detect the presence of tumor in an orthotopic glioma rat model. Athymic nude rats bearing orthotropic U87 tumors or age-matched tumor-free controls were investigated. HP studies were performed following intravenous injection of HP δ-[1-13C]gluconolactone and metabolic images using a flyback spectral-spatial echo-planar spectroscopic imaging pulse were acquired. The data were processed using in-house Matlab code. 6P-δ-GL and 6-phospho-γ-[1-13C]gluconolactone were observed in all rats ~10 seconds after HP δ-[1-13C]gluconolactone injection, followed ~5 seconds later by production of 6PG observed at 179.3ppm. These data indicate that HP δ-[1-13C]gluconolactone likely crosses the blood-brain barrier, consistent with its transport via glucose transporters, and is rapidly metabolized. Importantly, 6PG was significantly higher in tumor voxels. The ratio of 6PG-to-6P-δ-GL was comparable in normal brain and in normal-appearing contralateral brain of tumor-bearing rats at 0.43±0.09 and 0.45±0.06 respectively (p=0.85), but significant higher in the tumor regions at 0.70±0.11 (p=0.04 and p=0.02 respectively), consistent with the elevated PPP flux that typically occurs in tumor cells. Our results indicate, to our knowledge for the first time, that metabolism of HP δ-[1-13C]gluconolactone can be assessed in the brain and that elevated 6PG production in glioma provides a potential metabolic imaging approach to probe tumor development, recurrence and response to therapy.
CBMT-09. THERAPEUTIC EFFECT OF INDUCTION OF POLYGLUTAMYLATION IN HIGH-DOSE METHOTREXATE THERAPY TO PRIMARY CENTRAL NERVOUS SYSTEM LYMPHOMA
Authors: Fujimoto Kenji , Shinojima Naoki , Makino Keishi , Ichimura Koichi , Mukasa Akitake
Published: November 2019

BACKGROUND

Polyglutamylation is a reversible protein modification with a high occurrence rate in tumor cells. Methotrexate (MTX) incorporated into cells is polyglutamylated and strongly binds to dihydrofolate reductase without competitive inhibition by leucovorin (LV). Tumor cells with high polyglutamylation levels are selectively killed, whereas normal cells with lower polyglutamylation are rescued by LV. In this study, we investigated the therapeutic response of PCNSL to HD-MTX therapy with LV rescue based on polyglutamylation status and evaluated the combined effect of MTX and the drugs which upregulated polyglutamylation of MTX.

METHODS

Among 113 consecutive PCNSL patients who underwent HD-MTX therapy in our department between 2001 and 2014, polyglutamylation was evaluated by immunostaining in 82 cases, with relationships between polyglutamylation and therapeutic response retrospectively examined. Human malignant lymphoma cell lines were used for in vitro and in vivo experiments. The association of polyglutamylation and the response to MTX with LV rescue was assessed in these cell lines. Histone-deacetylase inhibitor (HDACI) has been reported to induce polyglutamylation by elevating folpolyglutamate synthetase (FPGS) expression, so the effects of HDACIs on polyglutamylation were evaluated. Combined effects of MTX and HDACI were evaluated by cell viability assay and xenograft mouse models.

RESULTS

The complete response rate was significantly higher in the group with polyglutamylation than in the non-polyglutamylation group [58.1% (25/43) and 33.3% (13/39), respectively] (p < 0.05), and progression-free survival was also significantly increased in the group with polyglutamylation (p < 0.01). The combined effect of MTX and HDACI was significantly enhanced in cell viability assay in vitro (p< 0.05), in subcutaneous (p< 0.001) and intracranial tumor xenografts (p< 0.001).

CONCLUSION

These findings suggested that polyglutamylation could be a predictor of therapeutic response to HD-MTX therapy with LV rescue in PCNSL. Combined therapy with HD-MTX and HDACIs might represent a promising treatment for HD-MTX resistant intractable PCNSL.
CBMT-10. MUTANT ISOCITRATE DEHYDROGENASE 1 INHIBITION INDUCES A UNIQUE MRS-DETECTABLE METABOLIC SIGNATURE IN LOW-GRADE GLIOMAS
Authors: Molloy Abigail , Lakhani Aliya , Najac Chloé , Subramani Elavarasan , Marie Gillespie Anne , Pieper Russell O , Viswanath Pavithra , Ronen Sabrina
Published: November 2019

Mutations in isocitrate dehydrogenase 1/2 (IDHmut) are reported in 70–90% of low-grade gliomas and secondary glioblastomas. IDHmut catalyzes the reduction of a-ketoglutarate (a-KG) to 2-hydroxyglutarate (2-HG), an oncometabolite that drives tumorigenesis. Inhibition of IDHmut is therefore a rapidly emerging therapeutic approach and IDHmut inhibitors such as AG-120 and AG-881 have shown promising results in phase 1 and 2 clinical studies. The goal of this study was to identify early non-invasive metabolic biomarkers of IDHmut inhibition that can serve to moniter response to these therapies. We used 1H and 13C magnetic resonance spectroscopy (MRS) to investigate the response of two genetically-engineered IDHmut cell lines (U87-based and normal human astrocyte-based) to AG-120 and AG-881 treatment. As expected, in both cell lines, our 1H-MRS data indicated that AG-120 and AG-881 induced a significant decrease in 2-HG. Interestingly however, we also observed a significant increase in phosphocholine and glutamate, pointing to broader changes in the metabolism of treated cells and a unique MRS signature. To further investigate the increase in glutamate induced by AG-120 and AG-881 in our models, we used 13C-MRS and quantified the flux of [1-13C] glucose and [3-13C] glutamine to 13C-labeled glutamate. Our results indicate that both AG-120 and AG-881 significantly increase the flux of 13C-labeled glutamine to 13C glutamate, while the flux of 13C-labeled glucose to 13C glutamate remained unchanged. Further studies are currently underway to explore the utility of using hyperpolarized [1-13C]-glutamine and hyperpolarized [1-13C]-a-KG for monitoring flux to glutamate and 2-HG, and to validate these probes as additional biomarkers of response to IDHmut inhibition. Taken together, our studies indicate that IDHmut inhibition induces a unique MRS-detectable metabolic profile that can potentially be exploited for early non-invasive, clinically translatable detection of response to emerging IDHmut inhibitors.
CBMT-15. MET INHIBITION DRIVES PGC1A DEPENDENT METABOLIC REPROGRAMMING AND ELICITS UNIQUE METABOLIC VULNERABILITIES IN GLIOBLASTOMA
Authors: Zhang Yiru , Nguyen Trang , Zhao Junfei , Shang Enyuan , Torrini Consuelo , Canoll Peter D , Karpel-Massler Georg , Siegelin Markus
Published: November 2019

The receptor kinase, c-MET, has emerged as a target for glioblastoma therapy. However, treatment resistance evolves inevitably. By performing a global metabolite screen with metabolite set enrichment coupled with transcriptome and gene set enrichment analysis and proteomic screening, we have identified substantial reprogramming of tumor metabolism, involving oxidative phosphorylation and fatty acid oxidation (FAO) with a substantial accumulation of acyl-carnitines accompanied by an increase of PGC1a in response to genetic (shRNA and CRISPR/Cas9) and pharmacological (crizotinib) inhibition of c-MET. Extracellular flux and carbon tracing analyses (U-13C-Glucose and U-13C-Glutamine) demonstrated enhanced oxidative metabolism, which was driven by FAO and supported by increased anaplerosis of glucose carbons. These findings were observed in concert with increased number and fusion of mitochondria and production of reactive oxygen species (ROS). Genetic interference with PGC1a rescued this oxidative phenotype driven by c-MET inhibition. Silencing and chromatin immunoprecipitation experiments demonstrated that CREB regulates the expression of PGC1a in the context of c-MET inhibition. Interference with both oxidative phosphorylation (metformin, oligomycin) and beta-oxidation of fatty acids (etomoxir) enhanced the anti-tumor efficacy of c-MET inhibition. Moreover, based on a high-throughput drug screen, we show that gamitrinib along with c-MET inhibition results in synergistic cell death. Finally, utilizing patient-derived xenograft models, we provide evidence that the combination treatments (crizotinib+etomoxir and crizotinib+gamitrinib) were significantly more efficacious than single treatment without induction of toxicity. Collectively, we have unraveled the mechanistic underpinnings of c-MET inhibitor treatment and identified novel combination therapies that may enhance the therapeutic efficacy of c-MET inhibition.
CBMT-17. DEFECTIVE QKI-DEPENDENT LIPID METABOLISM INDUCES GENOMIC INSTABILITY AND SENSITIZES GLIOBLASTOMA TO IMMUNOTHERAPY
Authors: Shingu Takashi , Hu Jian
Published: November 2019

Despite transformative effects on the therapy of cancers such as melanoma and lung adenocarcinoma, blockade of the T cell immune checkpoints has generated limited impact on glioblastoma. Identifying genetic/genomic alterations that could potentially sensitize the patients to immunotherapy will significantly improve the efficacy of immunotherapy on glioblastoma patients. As part of our effort to identify novel glioma suppressors that affect the interaction of GSCs with their microenvironment, we discovered that the RNA-binding protein Quaking (QKI) is a key regulator of cellular endocytosis. QKI is mutated or deleted in ~34% of human glioblastomas. Supporting QKI’s tumor suppresser function, 92% of the Nestin-CreERT2;QkiL/L;PtenL/L;p53L/L mice developed glioblastoma with a median survival of 105 days, however, the Nestin-CreERT2;PtenL/L;p53L/L mice did not develop any glioma up to a year. Mechanistically, QKI regulates the RNA stability and alternative splicing of numerous protein and lipid components of endolysosomes, particularly the unsaturated fatty acids (UFAs). Functionally, deletion of Qki and inhibition of UFA biosynthesis both decrease endolysosome-mediated receptor degradation, thereby enriching receptors on the cytoplasmic membrane (e.g., Frizzled and Notch1) that are essential for maintaining stemness. This enrichment of receptor signaling enables GSCs to cope with the low ligand levels during their invasion. On the other hand, lower lysosomal activity induced by Qki deletion and UFA loss led to defective mitophagy. We also found that insufficient UFAs in mitochondrial membrane significantly compromised mitochondrial membrane integrity and function. These two mechanisms concomitantly led to accumulation of damaged mitochondria and higher levels of reactive oxygen species (ROS), and consequently genomic instability. Lastly, we found that the higher level of genomic instability induced by Qki loss rendered cells more sensitive to anti-CTLA4 and anti-PD1 antibodies. Taken together, our data suggest that Qki/UFA loss-induced endolysosomal and mitochondrial defects promote gliomagenesis yet render cells vulnerabilities that could be harnessed for therapeutic purposes.
CBMT-24. CHARACTERIZATION OF PRIMARY CILIUM IN RECURRENT GLIOBLASTOMA: IMPLICATIONS FOR NEW THERAPEUTIC TARGETS
Authors: Stumpo Vittorio , Marappian Aruljothi , Giorgio D’Alessandris Quintino , Pacioni Simone , Di Bonaventura Rina , Ebbert Lara , Giordano Martina , Caccavella Valerio , Olivi Alessandro , Laura Falchetti Maria , Ricci-Vitiani Lucia , Pallini Roberto , Gopalakrishnan Jay
Published: November 2019

INTRODUCTION

Primary cilium is a highly conserved, dynamic cellular organelle which plays several roles in embryonic development, intracellular signaling, and cell cycle. Structural alterations of primary cilium have been described in human gliomas including glioblastoma (GBM), however, its actual role in pathogenesis and treatment resistance of these tumors is largely unknown.

METHODS

We investigated cilium morphology and expression of cilium-related genes in human glioma of various WHO grade and in couples of patient-derived glioma stem-like cells (GSCs) that were established from the very same GBM at first diagnosis and at recurrence. Immunohistochemistry with anti-Arl13b antibody was used to assess cilium morphology. The expression levels of genes involved in ciliary disassembly complex (CDC) were analyzed by quantitative real-time PCR, using neural progenitor cells (NPCs) as control. Lastly, we assessed 3 GSC cultures that were treated with a drug inhibiting cilia disassembly (CCB-Cil).

RESULTS

Anaplastic oligodendroglioma and proneural GBM showed the highest percentage of ciliated cells. In GBM, we found the highest percentage of fragmented cilia. GSCs derived from newly diagnosed GBMs displayed lower percentages of ciliated cells than those derived from recurrent GBMs (20% vs 70%). Morphological analysis indicated that GSCs from recurrent GBM show cilia with extremely various morphology compared with GSCs from newly diagnosed GBM and NPCs. Gene analysis showed reduced expression of CDC-related genes in GSCs from newly diagnosed GBM with respect to those from recurrent GBMs. CCB-Cil treatment determined a global reduction of CDC-related genes, increased expression of differentiation markers (GFAP), and reduction of stemness markers (SOX2).

CONCLUSIONS

The increased percentage of ciliated cells in GSCs from recurrent GBM may be related to a compensatory response of CDC and to an accelerated ciliary turnover. Blocking cilia disassembly reduces stemness features and induces differentiation in GSCs, suggesting that this approach could represent a promising strategy for targeting GBM.
CBMT-27. ABERRANT AMINO ACID METABOLISM EXPOSE NOVEL FUNCTIONAL VULNERABILITIES IN GLIOBLASTOMA
Authors: Prabhu Antony , Guastella Anthony , Kant Shiva , Kesarwani Pravin , Nakano Ichiro , Chinnaiyan Prakash
Published: November 2019

Despite advances in molecularly characterizing glioblastoma, metabolic alterations driving its aggressive phenotype are only beginning to be recognized. Integrative cross-platform analyses coupling global metabolomic and gene expression profiling identified aberrant amino acid (AA) metabolism as a central node in glioblastoma. This metabolic phenotype was recapitulated in preclinical models and through a series of investigations designed to determine the biologic consequence of individual AA, we identified branched chain AA (BCAA) and glutamine as the only indispensable AA in glioblastoma, serving as the sole source of nucleotide pools and glutathione, respectively. Although molecularly and/or chemically perturbing these pathways resulted in cytotoxicity in glioblastoma, normal astrocytes demonstrated a similar response, suggesting therapeutic limitations in targeting these core metabolic pathways in cancer. As the glioblastoma microenvironment typically represents a nutrient-deprived state, we went on to determine the capacity of these cells to adapt to AA restricted conditions by only providing these cells with the above-identified indispensable AA. Intriguingly, glioblastoma cells had the unique ability to revert a state of metabolic dormancy. In addition to triggering a reversible proliferative arrest, this dormant phenotype displayed a near-complete shutdown of glycolysis that allowed these cells to adapt and maintain survival in glucose-deprived conditions and elicited profound resistance to ionizing radiation. Studies designed to systemically understand molecular underpinnings driving this unique metabolically dormant state uncovered a functional reliance upon mTOR/p21 signaling to maintain proliferative arrest in nutrient unfavorable conditions. Consistent with these findings, p21 expression was differentially expressed in the perinecrotic core of glioblastoma when compared to the peripheral edge in patient samples. Targeting this novel functional vulnerability through p21 inhibition, thereby, ‘forcing’ proliferation of these cells in nutrient unfavorable conditions, led to robust cytotoxicity specific to dormant cells and enhanced radiation response. Targeting functional vulnerabilities in otherwise therapeutically resistant cells represents a promising clinical strategy in glioblastoma.
CBMT-31. HDAC INHIBITION DIMINISHES THE GROWTH OF ENDOGENOUS IDH MUTANT GLIOMAS
Authors: Elahi Lubayna , Garrett Matthew , Guo Lea , Condro Michael , Kawaguchi Riki , Mehta Shwetal , Lai Albert , Pope Whitney , Kornblum Harley
Published: November 2019

Histone deacetylase inhibitors (HDACi’s) have emerged as a promising class of drugs for treatment of malignancies such as glioblastoma (GBM). Several studies have demonstrated the anti-tumor property of HDACi’s against GBM in both in vitro and in vivo experiments. Nonetheless, in clinical trials, HDACi only marginally increased overall survival of patients with GBM. The mixed results of trials with HDACi’s in glioma have prompted us to hypothesize that improved selection of patients by tumor characteristics could enhance the efficacy of therapy. We specifically tested the effects of valproic acid (VPA), a HDACi and an antiepileptic drug against IDH mutant gliomas. We have previously demonstrated that our IDH mutant glioma cell lines have gene expression and methylation patterns highly similar to IDH mutant tumors in situ. Mutant IDH1 alters the epigenetic landscape of gliomas leading to the hypermethylation phenotype and transcriptional repression of genes. This repression of genes may contribute to tumorigenesis and progression of IDH mutant gliomas. We found that VPA inhibits the growth of patient-derived IDH1 mutant glioma lines. In addition, RNA sequencing analysis of vehicle and VPA-treated IDH1 mutant glioma cells showed de-repression of several genes previously shown to be downregulated in IDH1 mutant glioma cell lines. We also treated cells with another HDACi LBH589 and found that both VPA and LBH589 upregulates similar gene sets suggesting that HDAC inhibition promotes de-repression of previously repressed genes. Ongoing studies are aimed at determining the molecular mechanism by which VPA regulates the growth of IDH1 mutant tumors.
CBMT-41. IMAGING A HALLMARK OF CANCER: HYPERPOLARIZED 13C-MAGNETIC RESONANCE SPECTROSCOPY CAN NON-INVASIVELY MONITOR TERT EXPRESSION IN LOW-GRADE GLIOMAS IN VIVO
Authors: Viswanath Pavithra , Batsios Georgios , Marie Gillespie Anne , Pieper Russell O , Ronen Sabrina
Published: November 2019

Telomerase reverse transcriptase (TERT) expression is a hallmark of cancer, including in primary glioblastomas and low-grade oligodendrogliomas. Since TERT is essential for glioma proliferation and is an attractive therapeutic target, metabolic imaging of TERT status can inform on tumor progression and response to therapy. To that end, the goal of this study was to identify non-invasive, translational, hyperpolarized 13C-magnetic resonance spectroscopy-detectable metabolic imaging biomarkers of TERT in low-grade oligodendrogliomas. Unbiased metabolomic analysis of immortalized normal human astrocytes without (NHAcontrol) and with TERT (NHAtert) indicated that TERT induced unique metabolic reprogramming. Notably, TERT increased NADPH and NADH levels. Glucose flux through the pentose phosphate pathway (PPP) is a major producer of NADPH. Non-invasive imaging of PPP flux using hyperpolarized [U-13C,U-2H]-glucose indicated that production of the PPP metabolite 6-phosphogluconate (6-PG) was elevated in NHAtert cells relative to NHAcontrol. Importantly, hyperpolarized [U-13C,U-2H]-glucose flux to 6-PG clearly differentiated tumor from normal brain in orthotopic NHAtert tumor xenografts. Next, we exploited the observation that TERT expression increased NADH, which is essential for the metabolism of hyperpolarized [1-13C]-alanine to lactate. Lactate production from hyperpolarized [1-13C]-alanine was higher in NHAtert cells relative to NHAcontrol. Importantly, hyperpolarized [1-13C]-alanine imaging in orthotopic NHAtert tumors revealed pronounced differences in lactate production between tumor tissue and normal brain. Mechanistically, TERT increased expression of glucose-6-phosphate dehydrogenase (G6PDH), the rate-limiting enzyme for 6-PG and NADPH production, and of nicotinamide phosphoribosyltransferase (NAMPT), a rate-limiting enzyme for NADH biosynthesis. Silencing TERT reversed G6PDH and NAMPT expression and normalized hyperpolarized [U-13C,U-2H]-glucose and [1-13C]-alanine metabolism, validating our imaging biomarkers. Finally, hyperpolarized [U-13C,U-2H]-glucose and [1-13C]-alanine could monitor TERT status in the clinically relevant, patient-derived BT54 oligodendroglioma model. In summary, we demonstrate, for the first time, non-invasive in vivo imaging of TERT status in gliomas that can enable longitudinal analysis of tumor burden and treatment response in the clinic.
CBMT-46. MICRORNA-206 ATTENUATES GLIOMA CELL PROLIFERATION, MIGRATION, AND INVASION BY BLOCKING THE WNT/β-CATENIN PATHWAY VIA DIRECT TARGETING OF FRIZZLED 7
Authors: Wang Yingyi , Zhou Fengqi , Zhao Chunsheng
Published: November 2019

Glioma is one of the most frequent primary malignant brain tumours in adults and accumulating evidence has shown that microRNAs (miRNAs) are associated with various types of tumours, including glioma. It is essential to acquire a better understanding of the roles and mechanisms of miRNAs in WNT-driven glioblastoma (GBM). Here, we report that miR-206 inhibited the WNT/β-catenin pathway by directly targeting Frizzled 7 (FZD7) and functioned as a tumour-suppressor in glioma. The expression of miR-206 in human samples and glioma cells was assessed by real-time quantitative PCR (RT-qPCR), fluorescence in situ hybridization (FISH), and histological analysis. Cell Counting Kit-8 (CCK-8), colony formation, EdU, flow cytometry, wound healing, transwell invasion, and three-dimensional migration were performed to observe cellular proliferation, migration, and invasion in vitro. The effects of miR-206 in vivo were investigated using a xenograft nude mouse model. miR-206 expression was significantly downregulated in glioma specimens. FZD7 was confirmed as a direct target of miR-206. GBM cell proliferation, migration, and invasion were blocked by restoring the expression of miR-206. Moreover, intracranial glioma models demonstrated an inhibitory effect of miR-206 on intracranial glioma tumour growth. Our results suggested that miR-206 plays a key role in blocking the WNT/β-catenin signalling pathway by suppressing FZD7 and provides a prospective therapeutic strategy for the treatment of malignant glioma and other WNT-driven tumours.
CBMT-47. MODULATION OF NAD PATHWAYS AS A THERAPEUTIC STRATEGY FOR TARGETING IDH MUTANT GLIOMA
Authors: Miller Julie , Nagashima Hiroaki , Fink Alexandria , Tateishi Kensuke , Wakimoto Hiroaki , Banagis Jack , Cahill Daniel
Published: November 2019

BACKGROUND

IDH mutant tumors exhibit an altered metabolic state which may be exploited for use as a novel therapeutic approach. Our previous work has shown the IDH mutant cancer survival is dependent on the biosynthetic enzyme, nicotinamide phosphoribosyltransferase (NAMPT), for the production of nicotinamide adenine (NAD). Inhibition of NAMPT activity (NAMPTi) efficiently targets IDH mutant cells. NAD steady-state is also influenced by consumptive processes that utilize NAD as a coenzyme, including Sirtuin (SIRT) signaling. To avoid concerns surrounding NAMPT inhibitor toxicity at high doses, we sought to investigate whether modulation of SIRT activity can effectively target IDH mutant cells.

METHODS

IDH1 mutant cancer cells and patient-derived glioma lines were engineered for loss of SIRT gene expression using CRISPR/Cas9 gene editing or SIRT1 overexpression using a tetracycline-inducible expression system. The effect of silenced or enhanced SIRT1 activity was then assessed in IDH1 mutant cells alone or in combination with NAMPT inhibitors.

RESULTS

Loss of SIRT1 expression, but not other SIRT family members, confers resistance to NAMPT inhibition in IDH1 mutant cells. Consistent with the hypothesis that SIRT1 is a major consumer of NAD, we observed a significantly smaller decline in NAD when SIRT1 is deleted. In agreement with these findings, when SIRT1 activity is enhanced from baseline by tetracycline-mediated induction of SIRT1 expression, IDH mutant cell growth is slowed. Further, overexpression of SIRT1 leads to decreased cell viability and enhanced NAD depletion when induced in combination with NAMPTi.

CONCLUSIONS

IDH mutant tumors are vulnerable to NAD depletion. Our results show that this metabolic liability can be targeted by a combination of enhanced NAD consumption via SIRT1 activation and inhibition of NAD synthesis. Importantly, compounds to enhance SIRT1 activity are relatively non-toxic and in development for aging and neurologic disease, allowing potential for rapid translation to an IDH mutant-directed treatment.
CSIG-03. STAT3-BASED PATIENT STRATIFICATION IN PRECISION NEURO-ONCOLOGY
Authors: Tan Melanie , Sandanaraj Edwin , Chong Yuk-Kien , Lim See-Wee , Koh Lynnette , Ng Wai-Hoe , Tan Nguan-Soon , Tan Patrick , Ang Beng-Ti , Tang Carol
Published: November 2019

Glioblastoma (GBM) displays both spatial and temporal heterogeneity, whereupon mesenchymal tumors fare more poorly than the proneural molecular subtype. STAT3 was selected because its activation preceeds the proneural-mesenchymal transition. We first defined a STAT3 gene signature that stratified GBM patients into STAT3-high and -low cohorts. STAT3 inhibitor treatment selectively mitigated STAT3-high cell viability and tumorigenicity in orthotopic mouse xenograft models. In addition, we elucidated the mechanism underlying resistance in STAT3-low cells by combining STAT3 signature analysis with kinome screen data on STAT3 inhibitor-treated cells, allowing us to draw connections between kinases affected by STAT3 inhibitors, their associated transcription factors and target genes. As such, we show that dual inhibition of IGF-1R and STAT3 sensitized STAT3-low cells and improved survival in mice. Our study emphasizes the clinical implications of molecular subtype switching and demonstrates the importance of serially profiling GBM tumors upon recurrence so as to facilitate effective therapy.
CSIG-24. GABP LINKS AMPK SIGNALING TO TERT REGULATION IN A TERT PROMOTER MUTATION DEPENDENT MANNER
Authors: McKinney Andrew , Amen Alexandra , Stevers Nicholas , Costello Joseph
Published: November 2019

Over 90% of human tumors achieve immortality by reactivating telomerase reverse transcriptase (TERT), the catalytic subunit of telomerase. Two mutually exclusive, heterozygous mutations that activate the TERT promoter (TERTp) occur in a wide range of cancers including ~80% of glioblastomas (GBM). The mutations and TERTp activation enable cells to avoid replicative senescence and continue to divide beyond the normal limits on cellular lifespan, thus becoming immortal. Our lab has demonstrated that each mutation creates a novel E26-transformation specific binding site that allows the tetrameric form of the GA-binding protein GABP to bind and aberrantly activate the mutant TERTp. We further showed that reducing a tetramer-forming subunit of GABP, the GABPB1L transactivating subunit, reverses cellular immortality in vitro and reduces tumor growth in vivo. Beyond GABP, little is known about pathways that contribute to immortality via activation of the mutant TERTp. The heterotrimeric 5’ AMP-activated protein kinase (AMPK) complex is activated in human GBM compared to normal brain, and was previously implicated in regulating GABP expression. Here, we have determined that AMPK inhibition decreases transcription of both subunits of the tetrameric GABP complex (GABPA and GABPB1L) in GBM cells, and is sufficient to reduce TERT expression and telomerase activity in a TERT promoter mutation dependent manner. Together, these data suggest a novel and targetable connection between the AMPK signaling axis, telomerase activity and potentially tumor cell immortality.
CSIG-30. miR-146a INHIBITS TUMORIGENESIS AND INDUCES TEMOZOLOMIDE SENSITIVITY VIA AFFECTING CANCER STEM CELL PROPERTIES IN GBM
Authors: Cui Tiantian , Hlavin Bell Erica , McElroy Joseph , Liu Kevin , Manchanda Gulati Pooja , Johnson Benjamin , Sebastian Ebin , Paixao Becker Aline , Geurts Marjolein , Gray Ashley , Meng Wei , Fleming Jessica , Beyer Sasha , Wang Qi-en , Venere Monica , Jaharul Haque S , Robe Pierre , Chakravarti Arnab
Published: November 2019

BACKGROUND

Glioblastomas (GBMs) are the most aggressive primary brain tumors, with an average survival time of less than 15 months. miRNAs are emerging as promising and novel biomarkers in GBM. The aims of this study are: 1) to investigate novel miRNAs biomarkers that affect tumorigenesis and therapeutic sensitivity, and 2) to study the underlying molecular mechanisms in GBM.

METHODS

Nanostring v3 was performed followed by univariable (UVA) and multivariable (MVA) analyses. Functional studies were conducted to define the role of miR-146a in GBM tumorigenesis and therapeutic response and the molecular mechanisms were investigated.

RESULTS

UVA analyses demonstrated that miR-146a is one of the top miRNAs that correlated with better prognosis in GBM patients (p=9.21E-05), which was independent of MGMT promoter methylation by MVA analyses (p< 0.001). miR-146a expression was significantly downregulated in recurrent GBM tumors compared with the paired primary GBM tumors (p=0.003). Overexpression of miR-146a significantly inhibited tumor cell growth and sensitized patient-derived primary GBM cells to temozolomide (TMZ) treatment in vitro, and showed statistically significant smaller tumor size (p< 0.01) and prolonged survival (p=0.001) in vivo. In addition, miR-146a is downregulated in glioma cancer stem cells, and overexpression of miR-146a significantly affected glioma cancer stem cell self-renewal. We also found that overexpression of miR-146a significantly inhibited the NF-κB, AKT, and ERK pathways.

CONCLUSION

Our data suggest, for the first time, that miR-146a predicts favorable prognosis for GBM patients and sensitizes primary GBM cells to TMZ treatment in vitro and in vivo through regulating glioma stem cells. Importantly, miR-146a may prove to be a master switch shutting off AKT, NF-κB, as well as other pathways and may overcome redundancies among these pathways leading to resistance. FUNDING: Bohnenn Fund (to PR), R01CA108633, R01CA169368, U10CA180850-01(NCI), Brain Tumor Funders Collaborative Grant, and The Ohio State University CCC (all to AC).
CMET-10. INTRACRANIAL SOLITARY PITUITARY METASTASIS: THE IMPLICATIONS FROM FIVE CASES
Authors: Shan Changguo , Hong Weiping , Lai Mingyao , Wang Hui , Cai Linbo
Published: November 2019

BACKGROUND

Pituitary gland metastasis is a rare disease which represents only 1% of pituitary gland lesions. Intracranial solitary pituitary metastasis tends to be misdiagnosed as pituitary adenoma, resulting in a delayed anti-tumor treatment.

METHODS

Five cases of patients with pituitary gland metastasis recorded between 2014 and 2018 in our hospital were investigated with reference to patient demographics, symptoms at presentation, radiological and histological findings, management and outcomes.

RESULTS

Five patients (4 male and 1 female) were included and the median age was 48 years (range: 21 to 66). In those five cases, central nervous system related symptoms were the first sign of malignancy, including visual loss (5 in 5 patients), visual field defects (5 in 5 patients), apituitarism (5 in 5 patients), headache (4 in 5 patients), hypothroidism (4 in 5 patients) and diabetes insipidus (2 in 5 patients). All patients received total or partial hypophysectomy and pathologically revealed metastatic adenocarcinoma in 4 patients and metastatic squamous carcinoma in 1 patient. Further examinations by Computed Tomography (CT) or Positron Emission Computed Tomography (PET) indicated lung as primary site in five cases. EGFR mutation and ROS1 fusion were found in 3 and 1 adenocarcinoma patient, respectively, through gene detection of tissue. Postoperative radiotherapy (5 patients), target therapy (4 patients) and chemotherapy (1 patient) were given as subsequent treatment. During the follow-up, four patients died and the overall survival was 2, 8, 28 and 30 months, respectively.

CONCLUSION

We found that pituitary symptoms usually presented as the first sign of malignancy in intracranial solitary pituitary metastasis. Lung is the most frequently primary site, particularly in adenocarcinoma with driver gene mutation. Patients may benefit from multidiscipline treatment, including resection of pituitary metastasis combined with radiotherapy and targeted therapy.
CMET-36. IMMUNOTHERAPY VERSUS STANDARD OF CARE IN MELANOMA BRAIN METASTASES WITH KNOWN BRAF STATUS
Authors: Barnett Addison , Sagar Soumya , Lauko Adam , (Auston) Wei Wei , Chao Samuel , Peereboom David , Stevens Glen , Angelov Lilyana , Yu Jennifer , Murphy Erin , Mohammadi Alireza , Suh John , Barnett Gene , Ahluwalia Manmeet
Published: November 2019

INTRO/OBJECTIVE

A mutation of the BRAF protein is seen in approximately 50% of melanoma patients. Immune checkpoint inhibitors (ICI) are standard therapy in melanoma patients independent of a patient’s BRAF status. The primary objective of this study is to investigate the impact of BRAF status in patients treated with ICI compared to non-ICI systemic therapy on overall survival (OS) in patients with melanoma brain metastasis (MBM).

METHODS

We reviewed 351 patients with MBM treated at our tertiary care center between 2000 and 2018. Of these, 144 had known BRAF status, 71 of which were BRAF mutant and 73 were BRAF wild-type. OS was calculated from the date of diagnosis of MBM to compare the efficacy of ICI to other systemic therapies. Many of these patients received multiple lines of treatment including targeted therapies at some point during their care. The log-rank test and Cox proportional hazard model was utilized to determine differences in OS.

RESULTS

Eighty-four percent of patients received local therapy that included either surgery, stereotactic radiosurgery, or whole brain radiation therapy. In BRAF wild-type patients, 40 received ICI and 33 underwent non-ICI systemic therapy with a median survival (5.6 vs 7.1 months) and 2-year survival (28% vs 32%), respectively (p=0.64). Of the BRAF mutant patients, 33 received ICI and 38 did not with a median survival (17.1 vs 9.0 months) and 2-year survival (36% and 19%), respectively (p=0.014). When controlling for age, KPS, ECM, and number of lesions, BRAF mutant MBM patients treated with ICI compared to non-ICI had an OS hazard ratio, HR=0.4 (95% CI=0.21 – 0.78, p=0.0069).

CONCLUSION

ICI therapy in BRAF mutant MBM patients results in improved OS compared to those with non-ICI systemic therapy. No such difference was observed in the BRAF wild-type cohort.
CMET-38. PREVALENCE AND SURVIVAL OUTCOMES OF UROTHELIAL CARCINOMA BRAIN METASTASES
Authors: Kavouridis Vasileios , Harary Maya , Smith Timothy , Braun David , Iorgulescu Bryan
Published: November 2019

BACKGROUND

Urothelial carcinoma is a common malignancy with ~79,000 new cases diagnosed annually. However, urothelial brain metastases (UBM) are encountered uncommonly. Herein we evaluate their national prevalence, predictors, and treatment outcomes in the contemporary era.

METHODS

The characteristics, management, and overall survival (OS) of UBM patients (2010–2015) were evaluated using the National Cancer Database, which comprises >70% of all newly diagnosed cancers in the U.S. OS was analyzed with Kaplan-Meier methods and log-rank tests. National outcomes were compared to our institutional cohort of UBMs.

RESULTS

Out of 208,600 patients diagnosed with urothelial carcinoma, 8.4% presented with stage IV disease--of these only 216 (1.2%) had BMs at the time of diagnosis. Patients presenting with bone, liver, or lung metastases were more likely to present with synchronous BMs. Brain involvement demonstrated significantly worse median OS (3.9mos, 95%CI: 3.1–4.9) than non-BM stage IV disease (10.9mos, 95%CI: 10.6–11.2, p< 0.001). Compared to non-BM stage IV disease, UBMs were more likely to have surgery for metastatic disease and receive radiotherapy (p< 0.001); but were less likely to have primary resection or chemotherapy. In multivariable analysis of stage IV urothelial cancer, BMs demonstrated significantly worse OS (HR 1.43, 95%CI: 1.20–1.72, p< 0.001). In our institutional data, 10 urothelial cancer patients developed BMs; of which 7 were male, median age and KPS at diagnosis were 64.9yo (IQR 56.4–72.0) and 85 (IQR 75–100). Four patients had synchronous metastases; the median number of BM lesions was 2 (IQR 1–2), with a median size of 2.6cm (IQR 1.6–3.3). All 10 underwent GTR, 3 also with SRS and 7 with WBRT, associated with a median OS of 16.5mos.

CONCLUSIONS

Our results confirm the rarity of UBMs and suggest that BM screening may only be indicated in stage IV patients with neurological symptoms. Systemic therapies demonstrate improved OS in these patients.