Osteopontin drives neuroinflammation and cell loss in MAPT-N279K frontotemporal dementia patient neurons

Frontotemporal dementia (FTD) is an incurable group of early-onset dementias that can be caused by the deposition of hyperphosphorylated tau in patient brains. However, the mechanisms leading to neurodegeneration remain largely unknown. Here, we combined single-cell analyses of FTD patient brains with a stem cell culture and transplantation model of FTD. We identified disease phenotypes in FTD neurons carrying the MAPT-N279K mutation, which were related to oxidative stress, oxidative phosphorylation, and neuroinflammation with an upregulation of the inflammation-associated protein osteopontin (OPN). Human FTD neurons survived less and elicited an increased microglial response after transplantation into the mouse forebrain, which we further characterized by single nucleus RNA sequencing of microdissected grafts. Notably, downregulation of OPN in engrafted FTD neurons resulted in improved engraftment and reduced microglial infiltration, indicating an immune-modulatory role of OPN in patient neurons, which may represent a potential therapeutic target in FTD.

Single-cell analysis of 5-aminolevulinic acid intraoperative labeling specificity for glioblastoma

OBJECTIVE

Glioblastoma (GBM) is the most common and aggressive malignant primary brain tumor, and resection is a key part of the standard of care. In fluorescence-guided surgery (FGS), fluorophores differentiate tumor tissue from surrounding normal brain. The heme synthesis pathway converts 5-aminolevulinic acid (5-ALA), a fluorogenic substrate used for FGS, to fluorescent protoporphyrin IX (PpIX). The resulting fluorescence is believed to be specific to neoplastic glioma cells, but this specificity has not been examined at a single-cell level. The objective of this study was to determine the specificity with which 5-ALA labels the diversity of cell types in GBM.

METHODS

The authors performed single-cell optical phenotyping and expression sequencing-version 2 (SCOPE-seq2), a paired single-cell imaging and RNA sequencing method, of individual cells on human GBM surgical specimens with macroscopically visible PpIX fluorescence from patients who received 5-ALA prior to surgery. SCOPE-seq2 allowed the authors to simultaneously image PpIX fluorescence and unambiguously identify neoplastic cells from single-cell RNA sequencing. Experiments were also conducted in cell culture and co-culture models of glioma and in acute slice cultures from a mouse glioma model to investigate cell- and tissue-specific uptake and secretion of 5-ALA and PpIX.

RESULTS

SCOPE-seq2 analysis of human GBM surgical specimens revealed that 5-ALA treatment resulted in labeling that was not specific to neoplastic glioma cells. The cell culture further demonstrated that nonneoplastic cells could be labeled by 5-ALA directly or by PpIX secreted from surrounding neoplastic cells. Acute slice cultures from mouse glioma models showed that 5-ALA preferentially labeled GBM tumor tissue over nonneoplastic brain tissue with significant labeling in the tumor margins, and that this contrast was not due to blood-brain barrier disruption.

CONCLUSIONS

Together, these findings support the use of 5-ALA as an indicator of GBM tissue but question the main advantage of 5-ALA for specific intracellular labeling of neoplastic glioma cells in FGS. Further studies are needed to systematically compare the performance of 5-ALA to that of potential alternatives for FGS.

A pharmacological toolkit for human microglia identifies Topoisomerase I inhibitors as immunomodulators for Alzheimer's disease

While efforts to identify microglial subtypes have recently accelerated, the relation of transcriptomically defined states to function has been largely limited to in silico annotations. Here, we characterize a set of pharmacological compounds that have been proposed to polarize human microglia towards two distinct states - one enriched for AD and MS genes and another characterized by increased expression of antigen presentation genes. Using different model systems including HMC3 cells, iPSC-derived microglia and cerebral organoids, we characterize the effect of these compounds in mimicking human microglial subtypes in vitro. We show that the Topoisomerase I inhibitor Camptothecin induces a CD74high/MHChigh microglial subtype which is specialized in amyloid beta phagocytosis. Camptothecin suppressed amyloid toxicity and restored microglia back to their homeostatic state in a zebrafish amyloid model. Our work provides avenues to recapitulate human microglial subtypes in vitro, enabling functional characterization and providing a foundation for modulating human microglia in vivo.

EZH2 Inhibition Sensitizes IDH1R132H-Mutant Gliomas to Histone Deacetylase Inhibitor

Isocitrate Dehydrogenase-1 (IDH1) is commonly mutated in lower-grade diffuse gliomas. The IDH1R132H mutation is an important diagnostic tool for tumor diagnosis and prognosis; however, its role in glioma development, and its impact on response to therapy, is not fully understood. We developed a murine model of proneural IDH1R132H-mutated glioma that shows elevated production of 2-hydroxyglutarate (2-HG) and increased trimethylation of lysine residue K27 on histone H3 (H3K27me3) compared to IDH1 wild-type tumors. We found that using Tazemetostat to inhibit the methyltransferase for H3K27, Enhancer of Zeste 2 (EZH2), reduced H3K27me3 levels and increased acetylation on H3K27. We also found that, although the histone deacetylase inhibitor (HDACi) Panobinostat was less cytotoxic in IDH1R132H-mutated cells (either isolated from murine glioma or oligodendrocyte progenitor cells infected in vitro with a retrovirus expressing IDH1R132H) compared to IDH1-wild-type cells, combination treatment with Tazemetostat is synergistic in both mutant and wild-type models. These findings indicate a novel therapeutic strategy for IDH1-mutated gliomas that targets the specific epigenetic alteration in these tumors.

Glioma-Induced Alterations in Excitatory Neurons are Reversed by mTOR Inhibition

Gliomas are highly aggressive brain tumors characterized by poor prognosis and composed of diffusely infiltrating tumor cells that intermingle with non-neoplastic cells in the tumor microenvironment, including neurons. Neurons are increasingly appreciated as important reactive components of the glioma microenvironment, due to their role in causing hallmark glioma symptoms, such as cognitive deficits and seizures, as well as their potential ability to drive glioma progression. Separately, mTOR signaling has been shown to have pleiotropic effects in the brain tumor microenvironment, including regulation of neuronal hyperexcitability. However, the local cellular-level effects of mTOR inhibition on glioma-induced neuronal alterations are not well understood. Here we employed neuron-specific profiling of ribosome-bound mRNA via 'RiboTag,' morphometric analysis of dendritic spines, and in vivo calcium imaging, along with pharmacological mTOR inhibition to investigate the impact of glioma burden and mTOR inhibition on these neuronal alterations. The RiboTag analysis of tumor-associated excitatory neurons showed a downregulation of transcripts encoding excitatory and inhibitory postsynaptic proteins and dendritic spine development, and an upregulation of transcripts encoding cytoskeletal proteins involved in dendritic spine turnover. Light and electron microscopy of tumor-associated excitatory neurons demonstrated marked decreases in dendritic spine density. In vivo two-photon calcium imaging in tumor-associated excitatory neurons revealed progressive alterations in neuronal activity, both at the population and single-neuron level, throughout tumor growth. This in vivo calcium imaging also revealed altered stimulus-evoked somatic calcium events, with changes in event rate, size, and temporal alignment to stimulus, which was most pronounced in neurons with high-tumor burden. A single acute dose of AZD8055, a combined mTORC1/2 inhibitor, reversed the glioma-induced alterations on the excitatory neurons, including the alterations in ribosome-bound transcripts, dendritic spine density, and stimulus evoked responses seen by calcium imaging. These results point to mTOR-driven pathological plasticity in neurons at the infiltrative margin of glioma - manifested by alterations in ribosome-bound mRNA, dendritic spine density, and stimulus-evoked neuronal activity. Collectively, our work identifies the pathological changes that tumor-associated excitatory neurons experience as both hyperlocal and reversible under the influence of mTOR inhibition, providing a foundation for developing therapies targeting neuronal signaling in glioma.

Dietary restriction of cysteine and methionine sensitizes gliomas to ferroptosis and induces alterations in energetic metabolism

Ferroptosis is mediated by lipid peroxidation of phospholipids containing polyunsaturated fatty acyl moieties. Glutathione, the key cellular antioxidant capable of inhibiting lipid peroxidation via the activity of the enzyme glutathione peroxidase 4 (GPX-4), is generated directly from the sulfur-containing amino acid cysteine, and indirectly from methionine via the transsulfuration pathway. Herein we show that cysteine and methionine deprivation (CMD) can synergize with the GPX4 inhibitor RSL3 to increase ferroptotic cell death and lipid peroxidation in both murine and human glioma cell lines and in ex vivo organotypic slice cultures. We also show that a cysteine-depleted, methionine-restricted diet can improve therapeutic response to RSL3 and prolong survival in a syngeneic orthotopic murine glioma model. Finally, this CMD diet leads to profound in vivo metabolomic, proteomic and lipidomic alterations, highlighting the potential for improving the efficacy of ferroptotic therapies in glioma treatment with a non-invasive dietary modification.

Lactate is an epigenetic metabolite that drives survival in model systems of glioblastoma

Lactate accumulates to a significant amount in glioblastomas (GBMs), the most common primary malignant brain tumor with an unfavorable prognosis. However, it remains unclear whether lactate is metabolized by GBMs. Here, we demonstrated that lactate rescued patient-derived xenograft (PDX) GBM cells from nutrient-deprivation-mediated cell death. Transcriptome analysis, ATAC-seq, and ChIP-seq showed that lactate entertained a signature of oxidative energy metabolism. LC/MS analysis demonstrated that U-13C-lactate elicited substantial labeling of TCA-cycle metabolites, acetyl-CoA, and histone protein acetyl-residues in GBM cells. Lactate enhanced chromatin accessibility and histone acetylation in a manner dependent on oxidative energy metabolism and the ATP-citrate lyase (ACLY). Utilizing orthotopic PDX models of GBM, a combined tracer experiment unraveled that lactate carbons were substantially labeling the TCA-cycle metabolites. Finally, pharmacological blockage of oxidative energy metabolism extended overall survival in two orthotopic PDX models in mice. These results establish lactate metabolism as a novel druggable pathway for GBM.

Targeting S100A9-ALDH1A1-retinoic acid signaling to suppress brain relapse in EGFR-mutant lung cancer

The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) osimertinib has significantly prolonged progression-free survival (PFS) in EGFR-mutant lung cancer patients, including those with brain metastases. However, despite striking initial responses, osimertinib-treated patients eventually develop lethal metastatic relapse, often to the brain. Although osimertinib-refractory brain relapse is a major clinical challenge, its underlying mechanisms remain poorly understood. Using metastatic models of EGFR-mutant lung cancer, we show that cancer cells expressing high intracellular S100A9 escape osimertinib and initiate brain relapses. Mechanistically, S100A9 upregulates ALDH1A1 expression and activates the retinoic acid (RA) signaling pathway in osimertinib-refractory cancer cells. We demonstrate that the genetic repression of S100A9, ALDH1A1, or RA receptors (RAR) in cancer cells, or treatment with a pan-RAR antagonist, dramatically reduces brain metastasis. Importantly, S100A9 expression in cancer cells correlates with poor PFS in osimertinib-treated patients. Our study therefore identifies a novel, therapeutically targetable S100A9-ALDH1A1-RA axis that drives brain relapse.

Canonical NF-κB Promotes Lung Epithelial Cell Tumour Growth by Downregulating the Metastasis Suppressor CD82 and Enhancing Epithelial-to-Mesenchymal Cell Transition

Simple Summary

Canonical NF-κB signalling pathway acts as a tumour promoter in several types of cancer including non-small cell lung cancer (NSCLC), but the mechanism(s) by which it contributes to NSCLC is still under investigation. We show here that NF-κB RelA/p65 is required for the tumour growth of human NSCLC cells grown in vivo as xenografts in immune-compromised mice. RNA-seq transcriptome profile analysis identified the metastasis suppressor CD82/KAI1/TSPAN27 as a canonical NF-κB target. Loss of CD82 correlated with malignancy. RelA/p65 stimulates cell migration and epithelial-to-mesenchymal cell transition (EMT), mediated, in part, by CD82/KAI1, through integrin-mediated signalling, thus, identifying a mechanism mediating NF-κB RelA/p65 lung tumour promoting function.

Abstract

Background: The development of non-small cell lung cancer (NSCLC) involves the progressive accumulation of genetic and epigenetic changes. These include somatic oncogenic KRAS and EGFR mutations and inactivating TP53 tumour suppressor mutations, leading to activation of canonical NF-κB. However, the mechanism(s) by which canonical NF-κB contributes to NSCLC is still under investigation. Methods: Human NSCLC cells were used to knock-down RelA/p65 (RelA/p65^KD) and investigate its impact on cell growth, and its mechanism of action by employing RNA-seq analysis, qPCR, immunoblotting, immunohistochemistry, immunofluorescence and functional assays. Results: RelA/p65^KD reduced the proliferation and tumour growth of human NSCLC cells grown in vivo as xenografts in immune-compromised mice. RNA-seq analysis identified canonical NF-κB targets mediating its tumour promoting function. RelA/p65^KD resulted in the upregulation of the metastasis suppressor CD82/KAI1/TSPAN27 and downregulation of the proto-oncogene ROS1, and LGR6 involved in Wnt/β-catenin signalling. Immunohistochemical and bioinformatics analysis of human NSCLC samples showed that CD82 loss correlated with malignancy. RelA/p65^KD suppressed cell migration and epithelial-to-mesenchymal cell transition (EMT), mediated, in part, by CD82/KAI1, through integrin-mediated signalling involving the mitogenic ERK, Akt1 and Rac1 proteins. Conclusions: Canonical NF-κB signalling promotes NSCLC, in part, by downregulating the metastasis suppressor CD82/KAI1 which inhibits cell migration, EMT and tumour growth.

Vascular-derived SPARC and SerpinE1 regulate interneuron tangential migration and accelerate functional maturation of human stem cell-derived interneurons

Cortical interneurons establish inhibitory microcircuits throughout the neocortex and their dysfunction has been implicated in epilepsy and neuropsychiatric diseases. Developmentally, interneurons migrate from a distal progenitor domain in order to populate the neocortex - a process that occurs at a slower rate in humans than in mice. In this study, we sought to identify factors that regulate the rate of interneuron maturation across the two species. Using embryonic mouse development as a model system, we found that the process of initiating interneuron migration is regulated by blood vessels of the medial ganglionic eminence (MGE), an interneuron progenitor domain. We identified two endothelial cell-derived paracrine factors, SPARC and SerpinE1, that enhance interneuron migration in mouse MGE explants and organotypic cultures. Moreover, pre-treatment of human stem cell-derived interneurons (hSC-interneurons) with SPARC and SerpinE1 prior to transplantation into neonatal mouse cortex enhanced their migration and morphological elaboration in the host cortex. Further, SPARC and SerpinE1-treated hSC-interneurons also exhibited more mature electrophysiological characteristics compared to controls. Overall, our studies suggest a critical role for CNS vasculature in regulating interneuron developmental maturation in both mice and humans.

ETMM-05. LACTIC ACID FACILITATES GLIOBLASTOMA GROWTH THROUGH MODULATION OF THE EPIGENOME

Glioblastoma (GBM) is the most common primary malignant brain tumor with an unfavorable prognosis. While GBMs utilize glucose, there are other carbon sources at their disposal. Lactate accumulates to a significant amount in the infiltrative margin of GBMs. In the current study, we demonstrated that lactate rescued patient-derived xenograft (PDX) GBM cells from nutrient deprivation mediated cell death and inhibition of growth. Transcriptome analysis, ATAC-seq and CHIP-seq. showed that lactic acid exposure entertained a signature of cell cycle progression and oxidative phosphorylation (OXPHOS) /tricarboxylic acid (TCA)-cycle. LC/MS analysis demonstrated that U-13C-Lactate elicited substantial labeling of TCA-cycle metabolites, acetyl-CoA and histone protein acetyl-residues in PDX derived GBM cells. Given that acetyl-CoA is pivotal for histone acetylation we observed a dose-dependent elevation of histone marks (e.g. H3K27ac), which was rescued by genetic and pharmacological inhibition of lactic acid-uptake, ATP-citrate lyase, p300 histone-acetyl-transferase and OXPHOS, resulting in reversal of lactate mediated protection from cell death. CHIP-seq. analysis demonstrated that lactic acid facilitated enhanced binding of H3K27ac to gene promoters and cis-regulatory elements. Consistently, ATAC-seq. analysis highlighted enhanced accessibility of the chromatin by lactic acid. In a combined tracer experiment (U-13C-glucose and 3-C13-lactate), we made the fundamental observation that lactic acid carbons were predominantly labeling the TCA cycle metabolites over glucose, implying a critical role of lactic acid in GBMs. Finally, pharmacological blockage of the TCA-cycle, using a clinically validated drug, extended overall survival in an orthotopic PDX model in mice without induction of toxicity, implying a critical role of lactic acid in GBMs and establishing lactic acid metabolism as a novel drug target for GBM.

ETMM-04. AURKA INHIBITION REPROGRAMS METABOLISM AND IS SYNTHETICALLY LETHAL WITH FATTY ACID OXIDATION INHIBITION IN GLIOBLASTOMA MODEL SYSTEMS

Aurora kinase A (AURKA) has emerged as a viable drug target for glioblastoma (GBM), the most common malignant primary brain tumor in adults with a life expectancy of 12–15 months. However, resistance to therapy remains a critical issue, which partially may be driven by reprogramming of metabolism. By integration of transcriptome, chromatin immunoprecipitation with sequencing (CHIP-seq.), assay for transposase-accessible chromatin with sequencing (ATAC-seq.), proteomic and metabolite screening followed by carbon tracing (U-¹³C-Glucose, U-¹³C-Glutamine and U-¹³C-Palmitic acid) and extracellular flux analysis we provided evidence that genetic (shRNA and CRISPR/Cas9) and pharmacological (Alisertib) AURKA inhibition elicited substantial metabolic reprogramming supported in part by inhibition of MYC targets and concomitant activation of PPARA signaling. While glycolysis was suppressed by AURKA inhibition, we noted a compensatory increase in oxygen consumption rate fueled by enhanced fatty acid oxidation (FAO). Whereas interference with AURKA elicited a suppression of c-Myc, we detected an upregulation of PGC1A, a master regulator of oxidative metabolism. Silencing of PGC1A reversed AURKAi mediated metabolic reprogramming and sensitized GBM cells to AURKAi driven reduction of cellular viability. Chromatin immunoprecipitation experiments showed binding of c-Myc to the promoter region of PGC1A, which is abrogated by AURKA inhibition and in turn unleashed PGC1A expression. Consistently, ATAC-seq. confirmed higher accessibility of a MYC binding region within the PGC1A promoter, suggesting that MYC acts as a repressor of PGC1A. Combining alisertib with inhibitors of FAO or the electron transport chain exerted substantial synergistic growth inhibition in PDX lines in vitro and extension of overall survival in orthotopic GBM PDX models without induction of toxicity in normal tissue. In summary, these findings support that simultaneous targeting of oxidative energy metabolism and AURKAi might be a potential novel therapy against GBM.

Focused Ultrasound-Mediated Blood-Brain Barrier Opening Increases Delivery and Efficacy of Etoposide for Glioblastoma Treatment

PURPOSE

Glioblastoma (GBM) is a devastating disease. With the current treatment of surgery followed by chemoradiation, outcomes remain poor, with median survival of only 15 months and a 5-year survival rate of 6.8%. A challenge in treating GBM is the heterogeneous integrity of the blood-brain barrier (BBB), which limits the bioavailability of systemic therapies to the brain. There is a growing interest in enhancing drug delivery by opening the BBB with the use of focused ultrasound (FUS). We hypothesize that an FUS-mediated BBB opening can enhance the delivery of etoposide for a therapeutic benefit in GBM.

METHODS AND MATERIALS

A murine glioma cell line (Pdgf⁺, Pten^-/-, P53^-/-) was orthotopically injected into B6(Cg)-Tyrc-2J/J mice to establish the syngeneic GBM model for this study. Animals were treated with FUS and microbubbles to open the BBB to enhance the delivery of systemic etoposide. Magnetic resonance (MR) imaging was used to evaluate the BBB opening and tumor progression. Liquid chromatography tandem mass spectrometry was used to measure etoposide concentrations in the intracranial tumors.

RESULTS

The murine glioma cell line is sensitive to etoposide in vitro. MR imaging and passive cavitation detection demonstrate the safe and successful BBB opening with FUS. The combined treatment of an FUS-mediated BBB opening and etoposide decreased tumor growth by 45% and prolonged median overall survival by 6 days: an approximately 30% increase. The FUS-mediated BBB opening increased the brain tumor-to-serum ratio of etoposide by 3.5-fold and increased the etoposide concentration in brain tumor tissue by 8-fold compared with treatment without ultrasound.

CONCLUSIONS

The current study demonstrates that BBB opening with FUS increases intratumoral delivery of etoposide in the brain, resulting in local control and overall survival benefits.

EPCO-16. LACTIC ACID IS AN EPIGENETIC METABOLITE THAT DRIVES GLIOBLASTOMA SURVIVAL AND GROWTH

Glioblastoma (GBM) is the most common primary malignant brain tumor with an unfavorable prognosis and a reprogrammed metabolism. While tumors utilize glucose, there are other carbon sources at their disposal. Originally considered as a waste product of glucose catabolism, lactate accumulates to a significant amount in tumor tissue. We launched our studies with the central hypothesis that lactate is metabolized by GBM cells to promote their survival via modulation of the epigenome. We showed that lactate rescued patient-derived xenograft (PDX) GBM cells from nutrient deprivation mediated cell death and inhibition of growth. Transcriptome analysis, Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq), and CHIP-seq. showed that lactic acid exposure entertained a signature of cell cycle progression, oxidative phosphorylation (OXPHOS) and MYC target expression. LC/MS analysis demonstrated that U-13C-Lactate elicited substantial labeling of TCA-cycle metabolites, acetyl-CoA and histone protein acetyl-residues in PDX derived GBM cells. Given that acetyl-CoA is pivotal for histone acetylation we observed a dose-dependent elevation of histone marks (e.g. H3K27ac), which was rescued by genetic and pharmacological inhibition of lactic acid-uptake, ATP-citrate lyase, p300 histone-acetyl-transferase and OXPHOS, resulting in reversal of lactate mediated protection from cell death or facilitation of GBM growth. CHIP-seq. analysis demonstrated that lactic acid facilitated enhanced binding of H3K27ac to gene promoters and cis-regulatory elements (e.g. super-enhancers). Consistently, ATAC-seq. analysis highlighted enhanced accessibility of the chromatin by lactic acid. Finally, we assessed whether lactic acid is actively metabolized in vivo, utilizing an orthotopic PDX model of GBM. In a combined tracer experiment (U-13C-glucose and 3-C13-lactate), we made the fundamental observation that lactic acid carbons were predominantly labeling the TCA cycle metabolites over glucose, implying a critical role of lactic acid in GBMs and establishing lactic acid metabolism as a novel drug target for GBM that may be targeted with epigenetic drugs.

TAMI-33. AURKA INHIBITION REPROGRAMS METABOLISM AND IS SYNTHETICALLY LETHAL WITH FATTY ACID OXIDATION INHIBITION IN GLIOBLASTOMA

Aurora kinase A (AURKA) has emerged as a viable drug target for glioblastoma (GBM), the most common malignant primary brain tumor in adults with a life expectancy of 12-15 months. However, resistance to therapy remains a critical issue, which partially may be driven by reprogramming of metabolism. By integration of transcriptome, chromatin immunoprecipitation with sequencing (CHIP-seq.), assay for transposase-accessible chromatin with sequencing (ATAC-seq.), proteomic and metabolite screening followed by carbon tracing (U-13C-Glucose, U-13C-Glutamine and U-13C-Palmitic acid) and extracellular flux analysis we provided evidence that genetic (shRNA and CRISPR/Cas9) and pharmacological (Alisertib) AURKA inhibition elicited substantial metabolic reprogramming mediated in part by inhibition of MYC targets and concomitant activation of PPARA (e.g. PGC1A) signaling. While glycolysis was suppressed by AURKA inhibition, we noted a compensatory increase in oxygen consumption rate (OCR) fueled by fatty acid oxidation (FAO). Whereas interference with AURKA elicited a suppression of c-Myc, we detected an upregulation of PGC1A, a master regulator of oxidative metabolism, upon AURKA inhibition. Silencing of PGC1A reversed the increase in OCR and sensitized GBM cells to AURKA inhibition mediated reduction in cellular viability. CHIP experiments confirmed binding of c-Myc to the promoter region of PGC1A, which is abrogated by AURKA inhibition and in turn unleashed PGC1A expression. ATAC-seq. confirmed higher accessibility of the MYC binding region within the PGC1A promoter. Forced expression of c-Myc blocked AURKA inhibition mediated increase of PGC1A, suggesting that c-Myc acted as a repressor. To interfere with this oxidative metabolic reprogramming, we combined AURKA inhibitors with blockers of FAO (etomoxir), which elicited substantial synergistic growth inhibition and extension of overall survival in orthotopic patient derived xenografts of GBM in mice without induction of toxicity in normal tissue. Taken together, these data support that simultaneous targeting of oxidative metabolism and AURKA inhibition might be a potential novel therapy against GBM.

HDAC inhibitors elicit metabolic reprogramming by targeting super-enhancers in glioblastoma models

The Warburg effect is a tumor-related phenomenon that could potentially be targeted therapeutically. Here, we showed that glioblastoma (GBM) cultures and patients' tumors harbored super-enhancers in several genes related to the Warburg effect. By conducting a transcriptome analysis followed by ChIP-Seq coupled with a comprehensive metabolite analysis in GBM models, we found that FDA-approved global (panobinostat, vorinostat) and selective (romidepsin) histone deacetylase (HDAC) inhibitors elicited metabolic reprogramming in concert with disruption of several Warburg effect-related super-enhancers. Extracellular flux and carbon-tracing analyses revealed that HDAC inhibitors blunted glycolysis in a c-Myc-dependent manner and lowered ATP levels. This resulted in the engagement of oxidative phosphorylation (OXPHOS) driven by elevated fatty acid oxidation (FAO), rendering GBM cells dependent on these pathways. Mechanistically, interference with HDAC1/-2 elicited a suppression of c-Myc protein levels and a concomitant increase in 2 transcriptional drivers of oxidative metabolism, PGC1α and PPARD, suggesting an inverse relationship. Rescue and ChIP experiments indicated that c-Myc bound to the promoter regions of PGC1α and PPARD to counteract their upregulation driven by HDAC1/-2 inhibition. Finally, we demonstrated that combination treatment with HDAC and FAO inhibitors extended animal survival in patient-derived xenograft model systems in vivo more potently than single treatments in the absence of toxicity.

CD8+ T-cell-Mediated Immunoediting Influences Genomic Evolution and Immune Evasion in Murine Gliomas

PURPOSE

Cancer immunoediting shapes tumor progression by the selection of tumor cell variants that can evade immune recognition. Given the immune evasion and intratumor heterogeneity characteristic of gliomas, we hypothesized that CD8⁺ T cells mediate immunoediting in these tumors.

EXPERIMENTAL DESIGN

We developed retrovirus-induced PDGF⁺ Pten ^-/- murine gliomas and evaluated glioma progression and tumor immunogenicity in the absence of CD8⁺ T cells by depleting this immune cell population. Furthermore, we characterized the genomic alterations present in gliomas that developed in the presence and absence of CD8⁺ T cells.

RESULTS

Upon transplantation, gliomas that developed in the absence of CD8⁺ T cells engrafted poorly in recipients with intact immunity but engrafted well in those with CD8⁺ T-cell depletion. In contrast, gliomas that developed under pressure from CD8⁺ T cells were able to fully engraft in both CD8⁺ T-cell-depleted mice and immunocompetent mice. Remarkably, gliomas developed in the absence of CD8⁺ T cells exhibited increased aneuploidy, MAPK pathway signaling, gene fusions, and macrophage/microglial infiltration, and showed a proinflammatory phenotype. MAPK activation correlated with macrophage/microglia recruitment in this model and in the human disease.

CONCLUSIONS

Our studies indicate that, in these tumor models, CD8⁺ T cells influence glioma oncogenic pathways, tumor genotype, and immunogenicity. This suggests immunoediting of immunogenic tumor clones through their negative selection by CD8⁺ T cells during glioma formation.

Glioma-Induced Alterations in Neuronal Activity and Neurovascular Coupling during Disease Progression

Diffusely infiltrating gliomas are known to cause alterations in cortical function, vascular disruption, and seizures. These neurological complications present major clinical challenges, yet their underlying mechanisms and causal relationships to disease progression are poorly characterized. Here, we follow glioma progression in awake Thy1-GCaMP6f mice using in vivo wide-field optical mapping to monitor alterations in both neuronal activity and functional hemodynamics. The bilateral synchrony of spontaneous neuronal activity gradually decreases in glioma-infiltrated cortical regions, while neurovascular coupling becomes progressively disrupted compared to uninvolved cortex. Over time, mice develop diverse patterns of high amplitude discharges and eventually generalized seizures that appear to originate at the tumors' infiltrative margins. Interictal and seizure events exhibit positive neurovascular coupling in uninfiltrated cortex; however, glioma-infiltrated regions exhibit disrupted hemodynamic responses driving seizure-evoked hypoxia. These results reveal a landscape of complex physiological interactions occurring during glioma progression and present new opportunities for exploring novel biomarkers and therapeutic targets.

CBMT-03. EVALUATION OF PET TRACERS TO DIFFERENTIATE IDH1 MUTANT GBM

OBJECTIVE

PET/CT offers the unique potential to noninvasively evaluate biomarker expression and aberrant metabolism. 18F-FDG has driven PET/CT to the forefront of cancer imaging, as altered glucose metabolism is a hallmark of oncogenesis. However, 18F-FDG is suboptimal for GBM due to high physiologic uptake in normal brain. The development of alternative tracers has reignited the field of PET/CT in GBM and offers hope for diagnosis and molecular staging in GBM. We hypothesize that fundamental differences in metabolism and oncogene expression present in IDH1 mutatant gliomas can be shown using PET imaging, as has been suggested in some correlative clinical studies. Our objective was therefore to establish a causal link between IDH1 mutation in GBM and uptake of targeted PET tracers in a unique proneural GBM transgenic model characterized by p53, IDH1 mutations and PDGF expression.

METHODS

We examined the uptake of 3 blood-brain-barrier (BBB) penetrant tracers that have been used in GBM: (a) 18F-FDG, a surrogate for increased glycolysis; (b) 18F-Fluciclovine, an amino acid derivative transported into cells through the energy-independent L-type amino acid transporter (LAT) system and is approved by the FDA for prostate cancer; and (c) 11C-ER176, a tracer that binds the TSPO receptor that is generally expressed on activated microglia as well as GBM.

RESULTS

We did not observe significant differences in 18F-FDG uptake between wt and IDH mutant GBM cells. However, we found that IDH mutant GBM cells demonstrated significantly increased 18F-Fluciclovine (47%) and 11C-ER176 (53%) versus IDH wt cells.

CONCLUSION

We have established a causal link between IDH mutation status and uptake of (a) 18F-Fluciclovine, a promising FDA approved PET tracer and (b) 11C-ER176, a second generation TSPO ligand. Thus, we are performing further studies in orthotopic syngeneic GBM models to determine if PET imaging can non-invasively demonstrate molecular characterization and therapeutic stratification in glioma.

IMMU-42. CD8+ T-CELLS MEDIATE IMMUNOEDITING, AND INFLUENCE GENOTYPE, TUMOR ONCOGENIC PATHWAYS AND MICROENVIRONMENT DURING PROGRESSION OF MURINE GLIOMAS

Cancer immunoediting shapes tumor progression by the immunological selection of tumor cell variants that can evade immune recognition. Given the immune evasive cellular diversity of glioblastoma, we hypothesized that CD8+ T-cells mediate immunoediting in this tumor. We evaluated tumor progression in the absence of CD8+ T-cells by depleting this immune cell population in a transgenic murine glioma model. Tumors generated in the absence of CD8+ T-cells developed poorly in recipients with intact immunity, implying a more immunogenic profile. These tumors demonstrated increased chromosomal instability, gene fusions, MAPK signaling, and macrophage infiltration. These observations were stochastic, suggesting variability in the mode of tumor evolution in the absence of this immune effector. MAPK activation was correlated with macrophage recruitment in two transgenic murine models and the human disease. Our results indicate that CD8+ T-cells mediate a strong immunoediting selection in glioblastoma that protect against the hallmarks of cancer and drive immune evasion.

MET Inhibition Elicits PGC1α-Dependent Metabolic Reprogramming in Glioblastoma

The receptor kinase c-MET has emerged as a target for glioblastoma therapy. However, treatment resistance emerges inevitably. Here, we performed global metabolite screening with metabolite set enrichment coupled with transcriptome and gene set enrichment analysis and proteomic screening, and identified substantial reprogramming of tumor metabolism involving oxidative phosphorylation and fatty acid oxidation (FAO) with substantial accumulation of acyl-carnitines accompanied by an increase of PGC1α in response to genetic (shRNA and CRISPR/Cas9) and pharmacologic (crizotinib) inhibition of c-MET. Extracellular flux and carbon tracing analyses (U-¹³C-glucose, U-¹³C-glutamine, and U-¹³C-palmitic acid) 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. Genetic interference with PGC1α rescued this oxidative phenotype driven by c-MET inhibition. Silencing and chromatin immunoprecipitation experiments demonstrated that cAMP response elements binding protein regulates the expression of PGC1α in the context of c-MET inhibition. Interference with both oxidative phosphorylation (metformin, oligomycin) and β-oxidation of fatty acids (etomoxir) enhanced the antitumor efficacy of c-MET inhibition. Synergistic cell death was observed with c-MET inhibition and gamitrinib treatment. In patient-derived xenograft models, combination treatments of crizotinib and etomoxir, and crizotinib and gamitrinib were significantly more efficacious than single treatments and did not induce toxicity. Collectively, we have unraveled the mechanistic underpinnings of c-MET inhibition and identified novel combination therapies that may enhance its therapeutic efficacy. SIGNIFICANCE: c-MET inhibition causes profound metabolic reprogramming that can be targeted by drug combination therapies.

PRMT5-mediated regulation of developmental myelination

Oligodendrocytes (OLs) are the myelin-forming cells of the central nervous system. They are derived from differentiation of oligodendrocyte progenitors through a process requiring cell cycle exit and histone modifications. Here we identify the histone arginine methyl-transferase PRMT5, a molecule catalyzing symmetric methylation of histone H4R3, as critical for developmental myelination. PRMT5 pharmacological inhibition, CRISPR/cas9 targeting, or genetic ablation decrease p53-dependent survival and impair differentiation without affecting proliferation. Conditional ablation of Prmt5 in progenitors results in hypomyelination, reduced survival and differentiation. Decreased histone H4R3 symmetric methylation is followed by increased nuclear acetylation of H4K5, and is rescued by pharmacological inhibition of histone acetyltransferases. Data obtained using purified histones further validate the results obtained in mice and in cultured oligodendrocyte progenitors. Together, these results identify PRMT5 as critical for oligodendrocyte differentiation and developmental myelination by modulating the cross-talk between histone arginine methylation and lysine acetylation.

Myelin-forming cells derive from oligodendrocyte progenitors. Here the authors identify histone arginine methyl-transferase PRMT5 as critical for developmental myelination by modulating the cross-talk between histone arginine methylation and lysine acetylation, to favor differentiation.

Quantitative assessment of protein activity in orphan tissues and single cells using the metaVIPER algorithm

We and others have shown that transition and maintenance of biological states is controlled by master regulator proteins, which can be inferred by interrogating tissue-specific regulatory models (interactomes) with transcriptional signatures, using the VIPER algorithm. Yet, some tissues may lack molecular profiles necessary for interactome inference (orphan tissues), or, as for single cells isolated from heterogeneous samples, their tissue context may be undetermined. To address this problem, we introduce metaVIPER, an algorithm designed to assess protein activity in tissue-independent fashion by integrative analysis of multiple, non-tissue-matched interactomes. This assumes that transcriptional targets of each protein will be recapitulated by one or more available interactomes. We confirm the algorithm's value in assessing protein dysregulation induced by somatic mutations, as well as in assessing protein activity in orphan tissues and, most critically, in single cells, thus allowing transformation of noisy and potentially biased RNA-Seq signatures into reproducible protein-activity signatures.

Abstract 1841: Characterization of neuronal alterations in a new mouse model of low grade glioma

Diffusely infiltrating gliomas are the most common type of primary brain tumor seen in adults. Patients with low grade glioma (LGG) can survive for many years, but often suffer from seizures and cognitive impairment, and these symptoms are associated with an unfavorable prognosis. Glioma cells diffusely infiltrate cortical tissue, where tumor cells aggregate around neuronal cell bodies, a growth pattern referred to as perineuronal satellitosis, however the effects of tumor cells on neurons has not been well defined. To address this important issue we generated a mouse model that recapitulates the genetic and histological features of diffusely infiltrating LGG. In our model tumor growth is driven by PDGFA overexpression and p53 deletion in a RiboTag-Camk2a-Cre transgenic mouse. The RiboTag system allows for the isolation and sequencing of ribosome-bound transcripts from Camk2a neurons to obtain a measure of transcription and translation. Our analysis in non-tumor bearing brains identified neuron-specific genes that are highly regulated at the level of translation. mTOR signaling regulates cell growth, proliferation, and translation in response to diverse stimuli. To characterize mTOR signaling in our model we used immunohistochemical staining of pS6 as a marker of mTOR activity and found that neurons within the glioma infiltrated cortex have lower levels of pS6 staining compared to neurons in the surrounding cortex. To further assess these results we are using the RiboTag system to identify alterations in neuronal transcription and translation that occur in our model during glioma formation and in response to mTOR targeted treatments. These studies will provide new insights into the neuronal alterations contributing to seizures and cognitive impairment in glioma and enable the identification of potential molecular targets for novel therapies to treat the devastating consequences of cortical dysfunctions associated with glioma.

Citation Format: Daniela Torres, Angeliki Mela, Sohani Das Sharma, Nicholas Hornstein, Peter Sims, Peter Canoll. Characterization of neuronal alterations in a new mouse model of low grade glioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1841. doi:10.1158/1538-7445.AM2017-1841

Delayed spinal epidural hematoma following spinal anesthesia, far from needle puncture site

STUDY DESIGN

Case report.

OBJECTIVES

We report a case of spinal epidural hematoma (SEH) that appeared on the third postoperative day after lumbar spinal anesthesia, far from the needle puncture site. Possible mechanisms and etiological relation to patient's risk factors as well as diagnosis and management of SEH are briefly discussed.

SETTING

Asklepieion General Hospital of Voula, Athens, Greece.

METHODS AND RESULTS

A 64-year-old woman underwent an uneventful total knee arthroplasty operation under a spinal anesthetic. A lumbar puncture was performed in the L2-L3 interspace, that was atraumatic and successful on the first attempt. The operation was uneventful. On the third postoperative day, the patient developed a SEH that expanded from C2 to T3 levels. She was presented with bilateral shoulder pain, muscle weakness of the upper extremities with normal sensation, followed by paraparesis. The magnetic resonance imaging (MRI) revealed a large vascular malformation, partially ruptured forming a hematoma compressing the spinal cord toward the vertebral bodies The patient was treated conservatively and full recovery was achieved.

CONCLUSION

The possibility of SEH must be considered whenever neurological symptoms occur in the postoperative period, especially after a neuraxial blockade. The causes are multiple, a not-known lesion predisposing to bleeding and hematoma formation may preexist and the anesthetic technique can be directly or indirectly connected to this complication. MRI is the preferred diagnostic method.

Neonatal and adult O4(+) oligodendrocyte lineage cells display different growth factor responses and different gene expression patterns

Oligodendrocytes are the myelinating cells of the central nervous system. Although the CNS possesses the ability to repair demyelinating insults, in certain cases, such as the chronic lesions found in multiple sclerosis, remyelination fails. Cycling cells capable of becoming oligodendrocytes have been identified in both the developing and the adult mammalian forebrain. Many studies have focused on differences in gene expression profiles as oligodendrocyte progenitors differentiate into myelinating oligodendrocytes by isolating cells at different developmental stages from animals at a single age. However, few have studied the differences that exist between the progenitors of the neonatal CNS and those of the adult CNS. This study examined the response of neonatal and adult O4(+) cells to platelet-derived growth factor-AA, basic fibroblast growth factor, and insulin-like growth factor-1 and revealed marked differences. Whereas adult cells readily differentiated in vitro, the majority of neonatal progenitors remained immature. Microarray analysis was used to examine differences between acutely isolated neonatal and adult progenitors further. Gene expression profiles showed that the adult O4(+) cells are more developmentally mature than neonatal cells. Neonatal cells expressed higher levels of genes involved in proliferation. Adult O4(+) cells expressed higher levels of transcripts for genes involved in cell death and survival. Therefore, O4(+) cells from the adult differ greatly from those of the neonate, and the developmental stage of the animal models utilized must be taken into consideration when applying principles from neonatal systems to the adult.

Wiser (tsl): a recessive X-linked temperature-sensitive lethal mutation that affects the wings and the eyes in Drosophila melanogaster

In this study, we characterize a recessive X-linked temperature-sensitive mutation of the gene CG32711. The mutation, named wiser ( tsl ) (wings scalloped-eyes rough), was isolated from a dysgenic cross and is due to a natural P element insertion within the 5' regulatory region of the gene. Mutant (wiser ( tsl )) individuals exhibit wing notching, rough eyes, tarsal malformations and reduced life-span. At 29 degrees C they die at larval and late pharate stages or during eclosion. The CG32711 (wiser) gene is mainly expressed in the ventral midline cells, the peripheral neural system, the hemocytes and the tracheal system of embryos. It is also expressed in nurse cells of adult female ovaries. Our results show that the wiser gene is alternatively spliced generating two mRNAs, which share the same open reading frame, while western analysis identified two protein isoforms. Their expression pattern depends on the stage of development and the culture temperature. wiser ( tsl ) and wild-type individuals display different expression patterns of the two isoforms and this difference most probably accounts for the mutant phenotype. Our results indicate that wiser is a vital gene for the development of Drosophila melanogaster which has no orthologs outside the Drosophilidae.