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The multifaceted roles of metabolism in invasion have been investigated across many cancers. The brain tumor glioblastoma (GBM) is a highly invasive and metabolically plastic tumor with an inevitable recurrence. The neuronal glucose transporter 3 (GLUT3) was previously reported to correlate with poor glioma patient survival and be upregulated in GBM cells to promote therapeutic resistance and survival under restricted glucose conditions. It has been suggested that the increased glucose uptake mediated by GLUT3 elevation promotes survival of circulating tumor cells to facilitate metastasis. Here we suggest a more direct role for GLUT3 in promoting invasion that is not dependent upon changes in cell survival or metabolism. Analysis of glioma datasets demonstrated that GLUT3, but not GLUT1, expression was elevated in invasive disease. In human xenograft derived GBM cells, GLUT3, but not GLUT1, elevation significantly increased invasion in transwell assays, but not growth or migration. Further, there were no changes in glycolytic metabolism that correlated with invasive phenotypes. We identified the GLUT3 C-terminus as mediating invasion: substituting the C-terminus of GLUT1 for that of GLUT3 reduced invasion. RNA-seq analysis indicated changes in extracellular matrix organization in GLUT3 overexpressing cells, including upregulation of osteopontin. Together, our data suggest a role for GLUT3 in increasing tumor cell invasion that is not recapitulated by GLUT1, is separate from its role in metabolism and survival as a glucose transporter, and is likely broadly applicable since GLUT3 expression correlates with metastasis in many solid tumors.

Tumor microenvironments are the result of cellular alterations in cancer that support unrestricted growth and proliferation and result in further modifications in cell behavior, which are critical for tumor progression. Angiogenesis and therapeutic resistance are known to be modulated by hypoxia and other tumor microenvironments, such as acidic stress, both of which are core features of the glioblastoma microenvironment. Hypoxia has also been shown to promote a stem-like state in both non-neoplastic and tumor cells. In glial tumors, glioma stem cells (GSCs) are central in tumor growth, angiogenesis, and therapeutic resistance, and further investigation of the interplay between tumor microenvironments and GSCs is critical to the search for better treatment options for glioblastoma. Accordingly, we summarize the impact of hypoxia and acidic stress on GSC signaling and biologic phenotypes, and potential methods to inhibit these pathways.

We postulate that meningiomas undergo distinct metabolic reprogramming in tumorigenesis and unraveling their metabolic phenotypes provide new therapeutic insights. Glutamine catabolism is key to the growth and proliferation of tumors. Here, we investigated the metabolomics of freshly resected meningiomas and glutamine metabolism in patient-derived meningioma cells.1H NMR spectroscopy of tumor tissues from meningioma patients was used to differentiate the metabolite profiles of grade-I and grade-II meningiomas. Glutamine metabolism was examined using 13C/15N glutamine tracer, in 5 patient-derived meningioma cells.Alanine, lactate, glutamate, glutamine, and glycine were predominantly elevated only in grade-II meningiomas by 74%, 76%, 35%, 75%, and 33%, respectively, with alanine and glutamine levels being statistically significant (P ≤ .02). 13C/15N glutamine tracer experiments revealed that both grade-I and -II meningiomas actively metabolize glutamine to generate various key carbon intermediates including alanine and proline that are necessary for the tumor growth. Also, it is shown that glutaminase (GLS1) inhibitor, CB-839 is highly effective in downregulating glutamine metabolism and decreasing proliferation in meningioma cells.Alanine and glutamine/glutamate are mainly elevated in grade-II meningiomas. Grade-I meningiomas possess relatively higher glutamine metabolism providing carbon/nitrogen for the biosynthesis of key nonessential amino acids. GLS1 inhibitor (CB-839) is very effective in downregulating glutamine metabolic pathways in grade-I meningiomas leading to decreased cellular proliferation.

Mutations in isocitrate dehydrogenases 1 and 2 (IDHmut) are present in a variety of cancers, including glioma, acute myeloid leukemia (AML), melanoma, and cholangiocarcinoma. These mutations promote hypermethylation, yet it is only a favorable prognostic marker in glioma, for reasons that are unclear. We hypothesized that the patterns of DNA methylation, and transcriptome profiles, would vary among IDHmut cancers, especially gliomas. Using Illumina 450K and RNA-Seq data from The Cancer Genome Atlas, we show that of 365,092 analyzed CpG sites, 70,591 (19%) were hypermethylated in IDHmut gliomas compared to wild-type (IDHwt) gliomas, and only 3%, 2%, and 4% of CpG sites were hypermethylated in IDHmut AML, melanoma, and cholangiocarcinoma, relative to each of their IDHwt counterparts. Transcriptome differences showed pro-malignant genes that appear to be unique to IDHmut gliomas. However, genes involved in differentiation and immune response were suppressed in all IDHmut cancers. Additionally, IDHmut caused a greater degree of hypermethylation in undifferentiated neural progenitor cells than in mature astrocytes. These data suggest that the extent and targets of IDHmut-induced genomic hypermethylation vary greatly according to the cellular context and may help explain why IDHmut is only a favorable prognostic marker in gliomas.

Tumorigenic and non-neoplastic tissue injury occurs via the ischemic microenvironment defined by low oxygen, pH, and nutrients due to blood supply malfunction. Ischemic conditions exist within regions of pseudopalisading necrosis, a pathological hallmark of glioblastoma (GBM), the most common primary malignant brain tumor in adults. To recapitulate the physiologic microenvironment found in GBM tumors and tissue injury, we developed an in vitro ischemic model and identified chromodomain helicase DNA-binding protein 7 (CHD7) as a novel ischemia-regulated gene. Point mutations in the CHD7 gene are causal in CHARGE syndrome (a developmental disorder causing coloboma, heart defects, atresia choanae, retardation of growth, and genital and ear anomalies) and interrupt the epigenetic functions of CHD7 in regulating neural stem cell maintenance and development. Using our ischemic system, we observed microenvironment-mediated decreases in CHD7 expression in brain tumor-initiating cells and neural stem cells. Validating our approach, CHD7 was suppressed in the perinecrotic niche of GBM patient and xenograft sections, and an interrogation of patient gene expression datasets determined correlations of low CHD7 with increasing glioma grade and worse patient outcomes. Segregation of GBM by molecular subtype revealed a novel observation that CHD7 expression is elevated in proneural versus mesenchymal GBM. Genetic targeting of CHD7 and subsequent gene ontology analysis of RNA sequencing data indicated angiogenesis as a primary biological function affected by CHD7 expression changes. We validated this finding in tube-formation assays and vessel formation in orthotopic GBM models. Together, our data provide further understanding of molecular responses to ischemia and a novel function of CHD7 in regulating angiogenesis in both neoplastic and non-neoplastic systems. Stem Cells 2019;37:453–462

Meningioma is the most common primary brain tumor with nearly thirty thousand new cases in the US every year. While most meningiomas are categorized as benign, they can still impact brain structures and result in disability or lethality. Currently, there is no widely accepted chemotherapy, and our understanding of the disease’s molecular characteristics is very limited. In this study, we aimed to identify druggable molecular targets for repurposing of chemotherapies against meningiomas. We analyzed previously published dataset of 493 meningioma patients by Felix Sahm et al (Lancet Oncology, 2017) for association with progression-free survival (PFS) and searched for candidate drugs targeting the pathways linked to poor patient prognosis. Our analyses indicated 981 genes for which methylation of mapped CpG sites was found to be consistently associated with shorter or longer PFS at FDR-adjusted p < 0.05. Using Cytoscape/Reactome FI software, we cross-referenced current cancer drugs that target these and identified docetaxel and raloxifene hydrochloride as potential candidates. In our vitro study, docetaxel caused apoptotic cell death in established and primary patient meningioma lines of various grades. IC50s of docetaxel in the seventeen meningioma cell lines tested ranged from 0.8nM to 4.4mM, which partially corresponded to the growth rates of these cells. As monotherapy, the effects of docetaxel on meningioma were attenuated by multidrug resistance protein 1 (ABCB1) and Cytochrome P450 1B1 (CYP1B1). Docetaxel at 2µM augment double-stranded DNA damage caused by irradiation in vitro, leading to increased cell death. In animal model, low doses of docetaxel and radiation therapy had synergistic effects, increasing survival of mice intracranially implanted with human meningioma cells. Our study will advance our understanding of molecular pathways driving meningioma and identify potential targeted therapies to bridge the current gap in treatment of the disease.

Meningioma is the most common primary brain tumor with nearly thirty thousand new cases in the US every year. While most meningiomas grow slowly, hence categorized as benign, they can still impact brain structures and result in disability or lethality. Currently, there is no widely accepted chemotherapy for meningioma, and our understanding of the disease’s molecular characteristics is very limited. In this study, we aimed to identify druggable molecular targets for repurposing of chemotherapies against meningiomas. We analyzed previously published dataset of 493 meningioma patients by Felix Sahm et al (Lancet Oncology, 2017) for association with progression-free survival (PFS) and identified associations of methylation at individual CpG sites as detected by the Illumina 450k platform with PFS. Subsequently, we searched for candidate drugs targeting the pathways linked to poor patient prognosis. Our analyses indicated 981 genes for which methylation of mapped CpG sites was found to be consistently associated with shorter PFS (positive hazard ratios (HRs)) and with longer PFS (negative HRs) at FDR-adjusted p < 0.05. Using Cytoscape/Reactome FI app, we cross-referenced current cancer drugs that target these and identified docetaxel and raloxifene hydrochloride as potential candidates. In our vitro study, docetaxel caused apoptotic cell death in established and primary patient meningioma lines of various grades. IC50s of docetaxel in the sixteen meningioma cell lines tested ranged from 0.8nM to 4.4mM, which partially corresponded to the growth rates of these cells. Our study will advance our understanding of molecular pathways driving meningioma and identify potential targeted therapies to bridge the current gap in treatment of the disease.

De-regulated cellular energetics is an emerging hallmark of cancer with alterations to glycolysis, oxidative phosphorylation, the pentose phosphate pathway, lipid oxidation and synthesis and amino acid metabolism. Understanding and targeting of metabolic reprogramming in cancers may yield new treatment options, but metabolic heterogeneity and plasticity complicate this strategy. One highly heterogeneous cancer for which current treatments ultimately fail is the deadly brain tumor glioblastoma. Therapeutic resistance, within glioblastoma and other solid tumors, is thought to be linked to subsets of tumor initiating cells, also known as cancer stem cells. Recent profiling of glioblastoma and brain tumor initiating cells reveals changes in metabolism, as compiled here, that may be more broadly applicable. We will summarize the profound role for metabolism in tumor progression and therapeutic resistance and discuss current approaches to target glioma metabolism to improve standard of care.

BACKGROUND Venous thromboembolism (VTE) is a debilitating and life-threating condition that is common in patients with cancer, especially glioma. There are no widely-accepted guidelines for antithrombotic prophylaxis in glioma patients, in part because of the risk of iatrogenic intracerebral hemorrhage. Effective VTE prediction models exist for patients with other cancers, but not glioma. Our prior publications suggested a protective role of IDH mutation (IDHmut) against VTE, as well as a positive association between elevated circulating Tissue Factor (TF), a procoagulant secreted by cancers, and VTE in glioma patients. Others have recently found a correlation between podoplanin, a platelet activator, and cancer-associated VTE, but this has not yet been proven in gliomas. Our objective was to develop a multidimensional VTE prediction tool to improve glioma patient care, incorporating clinical, blood-based, histologic, and molecular markers. METHODS The Northwestern University Nervous System Tumor Bank provided preoperative arterial blood, tumor tissue, and clinical-pathologic data from 254 grade II-IV glioma patients over a 4-year interval. Molecular profiling was done by GlioSeq NGS. RESULTS Forty-six out of 254 grade II-IV glioma patients (18%) experienced VTE during their disease course. VTE was associated with worse median overall survival (18 vs. 54 months, P< 0.001). Positive risk factors for VTE included advanced patient age, high body mass index, high glioma grade, prior history of VTE, coronary artery disease, hyperlipidemia, hypertension, and elevated circulating TF activity, among other variables. While tumor expression of podoplanin positively correlated with VTE, circulating podoplanin did not. Among molecular markers, the strongest was IDHmut, being associated with greatly reduced VTE risk (OR=0.28; 95% CI=0.12-0.64, P=0.001). CONCLUSIONS This study identified multiple risk factors for glioma-associated VTE. Using these data, we have developed a web-based multivariable integrated prediction calculator to identify glioma patients who would benefit the most from prophylactic anticoagulation.

BACKGROUND: Mesenchymal stemlike cells (MSLCs) have been detected in many types of cancer including brain tumors and have received attention as stromal cells in the tumor microenvironment. However, the cellular mechanisms underlying their participation in cancer progression remain largely unexplored. The aim of this study was to determine whether MSLCs have a tumorigenic role in brain tumors. METHODS: To figure out molecular and cellular mechanisms in glioma invasion, we have cultured glioma with MSLCs in a co-culture system. RESULTS: Here, we show that MSLCs in human glioblastoma (GBM) secrete complement component C5a, which is known for its role as a complement factor. MSLC-secreted C5a increases expression of zinc finger E-box-binding homeobox 1 (ZEB1) via activation of p38 mitogen-activated protein kinase (MAPK) in GBM cells, thereby enhancing the invasion of GBM cells into parenchymal brain tissue. CONCLUSION: Our results reveal a mechanism by which MSLCs undergo crosstalk with GBM cells through the C5a/p38 MAPK/ZEB1 signaling loop and act as a booster in GBM progression. KEY POINTS: 1. MSLCs activate p38 MAPK-ZEB1 signaling in GBM cells through C5a in a paracrine manner, thereby boosting the invasiveness of GBM cells in the tumor microenvironment. 2. Neutralizing of C5a could be a potential therapeutic target for GBM by inhibition of mesenchymal phenotype.

Despite available treatments including surgical resection, radiation and chemotherapy, glioblastoma (GBM) is incurable with rapid recurrence and low median survival rate of just fourteen months. Development of more effective treatments is difficult due to the highly heterogeneous nature of GBM. One aspect of that heterogeneity involves brain tumor initiating cells (BTICs) that have a stem cell-like ability to self-renew. BTICs can readily alter their metabolism and survive in low nutrient environments due in part to increased GLUT3 expression. We believe that the higher expression of GLUT3 in cancer cells compared to non-tumor cells makes it a therapeutic target, although the potential for toxicity must be considered. In recently accepted studies by Libby et al., we reported on two novel GLUT inhibitors identified by structure based virtual screening (SBVS) using a GLUT3 homology model. We are creating a structure-activity relationship profile and seek to increase the potency, selectivity and stability of the GLUT inhibitors. In this study we have tested a number of novel analogs and identified three that have maintained efficacy against BTICs in vitro. Importantly, these compounds display minimal toxicity against human astrocytes. The novel derivatives have increased stability compared to the lead compounds and are efficacious in the nanomolar range. In the future, we intend to utilize our anti-GLUT compounds alone and in combination with radio- and chemotherapy with the hope of clinical translation.

BACKGROUND: The Human Protein Atlas (HPA) is a comprehensive resource for exploration of human proteome which contains a vast amount of proteomics and transcriptomics data generated from antibody-based tissue micro-array profiling and RNA deep-sequencing. Data from the HPA are freely available via proteinatlas.org, allowing scientists to access and incorporate the data into their research. Previously, the R package hpar has been created for fast and easy programmatic access of HPA data. Here, we introduce HPAanalyze, an R package aims to simplify exploratory data analysis from those data, as well as provide other complementary functionality to hpar. RESULTS: HPAanalyze is an R package for retrieving and performing exploratory data analysis from HPA. It provides functionality for importing data tables and xml files from HPA, exporting and visualizing data, as well as download all staining images of interest. The package is free, open source, and available via Github. CONCLUSIONS: HPAanalyze intergrates into the R workflow via the tidyverse philosophy and data structures, and can be used in combination with Bioconductor packages for easy analysis of HPA data.

Background The Human Protein Atlas (HPA) aims to map human proteins via multiple technologies including imaging, proteomics and transcriptomics. Access of the HPA data is mainly via web-based interface allowing views of individual proteins, which may not be optimal for data analysis of a gene set, or automatic retrieval of original images. Results HPAanalyze is an R package for retrieving and performing exploratory analysis of data from HPA. HPAanalyze provides functionality for importing data tables and xml files from HPA, exporting and visualizing data, as well as downloading all staining images of interest. The package is free, open source, and available via Bioconductor and GitHub. We provide examples of the use of HPAanalyze to investigate proteins altered in the deadly brain tumor glioblastoma. For example, we confirm Epidermal Growth Factor Receptor elevation and Phosphatase and Tensin Homolog loss and suggest the importance of the GTP Cyclohydrolase I/Tetrahydrobiopterin pathway. Additionally, we provide an interactive website for non-programmers to explore and visualize data without the use of R. Conclusions HPAanalyze integrates into the R workflow with the tidyverse framework, and it can be used in combination with Bioconductor packages for easy analysis of HPA data.

Tumor heterogeneity has hampered the development of novel effective therapeutic options for aggressive cancers, including the deadly primary adult brain tumor glioblastoma (GBM). Intratumoral heterogeneity is partially attributed to the tumor initiating cell (TIC) subset that contains highly tumorigenic, stem-like cells. TICs display metabolic plasticity but can have a reliance on aerobic glycolysis. Elevated expression of GLUT1 and GLUT3 is present in many cancer types, with GLUT3 being preferentially expressed in brain TICs (BTICs) to increase survival in low nutrient tumor microenvironments, leading to tumor maintenance. Through structure-based virtual screening (SBVS), we identified potential novel GLUT inhibitors. The screening of 13 compounds identified two that preferentially inhibit the growth of GBM cells with minimal toxicity to non-neoplastic astrocytes and neurons. These compounds, SRI-37683 and SRI-37684, also inhibit glucose uptake and decrease the glycolytic capacity and glycolytic reserve capacity of GBM patient-derived xenograft (PDX) cells in glycolytic stress test assays. Our results suggest a potential new therapeutic avenue to target metabolic reprogramming for the treatment of GBM, as well as other tumor types, and the identified novel inhibitors provide an excellent starting point for further lead development.

Background Depending on the level, differentiation state, and tumor stage, reactive nitrogen and oxygen species inhibit or increase cancer growth and tumor initiating cell maintenance. The rate-limiting enzyme in a pathway that can regulate reactive species production but has not been thoroughly investigated in glioblastoma (GBM; grade IV astrocytoma) is guanosine triphosphate (GTP) cyclohydrolase 1 (GCH1). We sought to define the role of GCH1 in the regulation of GBM growth and brain tumor initiating cell (BTIC) maintenance. Methods We examined GCH1 mRNA and protein expression in patient-derived xenografts, clinical samples, and glioma gene expression datasets. GCH1 levels were modulated using lentiviral expression systems, and effects on cell growth, self-renewal, reactive species production, and survival in orthotopic patient-derived xenograft models were determined. Results GCH1 was expressed in GBMs with elevated but not exclusive RNA and protein levels in BTICs in comparison to non-BTICs. Overexpression of GCH1 in GBM cells increased cell growth in vitro and decreased survival in an intracranial GBM mouse model. In converse experiments, GCH1 knockdown with short hairpin RNA led to GBM cell growth inhibition and reduced self-renewal in association with decreased CD44 expression. GCH1 was critical for controlling reactive species balance, including suppressing reactive oxygen species production, which mediated GCH1 cell growth effects. In silico analyses demonstrated that higher GCH1 levels in glioma patients correlate with higher glioma grade, recurrence, and worse survival. Conclusions GCH1 expression in established GBMs is pro-tumorigenic, causing increased growth due, in part, to promotion of BTIC maintenance and suppression of reactive oxygen species.

Glioblastoma (GBM) is an aggressive form of brain cancer with few treatment options, characterized by over-activation of receptor tyrosine kinases (RTKs). Brain tumor-initiating cells (BTICs) is a subpopulation of cells in GBM which have the unique capacity to self-renew, facilitating recurrence. Tissue Factor (TF), normally involved in blood coagulation, is elevated in GBM and strongly correlates with more aggressive behavior. We hypothesize that TF promotes malignant behavior in glioblastoma by activating protease-activated receptor 2 (PAR2), leading to RTK stimulation and the maintenance of brain tumor-initiating cells. Therefore, our approaches are to determine: the mechanisms by which TF-PAR2 stimulates RTK signaling in GBM; the role of RTKs in mediating TF-induced BTIC maintenance in GBM, and the effect of blocking TF signaling on RTK-based therapies against GBM. Our data indicate that TF can activate multiple classes of tumor-promoting RTKs, and sustains cell proliferation through its main receptor, PAR2, even in the presence of an RTK inhibitor. We also found that TF suppression impairs the BTIC phenotype in high TF-expressing, RTK-driven GBM. This project will advance our understanding of how TF promotes malignant behavior, identify a powerful means by which cancers can resist RTK inhibitors currently in clinical use, and demonstrate the therapeutic potential of blocking TF-PAR2 signaling in cancer.

Glioblastoma (GBM), or grade IV astrocytoma, is a deadly disease due in part to the high degree of intratumoral heterogeneity that contributes to treatment failures. One cellular subset enriched for the capacity to propagate tumor growth and promote therapeutic resistance is brain tumor initiating cells (BTICs). The aim of the study was to define the roles of GTP cyclohydrolase 1 (GCH1) in regulation of BTIC phenotypes via reactive species. We examined GCH1 mRNA and protein expression in patient-derived xenografts, clinical samples and glioma gene expression datasets. GCH1 levels were modulated using lentiviral expression systems, and effects on cell growth, self-renewal, reactive species production and in vitro animal survival were determined. We found that GCH1 RNA and protein expression were increased in BTICs in comparison to non-BTICs, but that GCH1 was not exclusive to the BTIC fraction. Indeed, GCH1 was elevated in GBM in comparison to normal brain. Overexpression of GCH1 in GBM cells increased cell growth in vitro and decreased survival in an intracranial GBM mouse model. In contrast, GCH1 knockdown with short hairpin RNA in GBM cells led to growth inhibition in vitro as well as increased survival in animal models. Mechanistically, GCH1 increased CD44 expression and was critical for controlling reactive species balance, including suppressing reactive oxygen species production. In silico analyses demonstrated that higher GCH1 levels in glioma patients correlate with higher glioma grade, recurrence and worse survival. Together, our data suggest that upregulation of GCH1 in BTICs promotes tumor maintenance and is a key regulator of reactive oxygen species in GBM.

Gliomas are central nervous system tumors that primarily occur in the brain and arise from glial cells. Gliomas include the most common malignant brain tumor in adults known as grade IV astrocytoma, or glioblastoma (GBM). GBM is a deadly disease for which the most significant advances in treatment offer an improvement in survival of only ∼2 months.To develop novel treatments and improve patient outcomes, we and others have sought to determine the role of molecular signals in gliomas. Recent Advances: One signaling molecule that mediates important biologies in glioma is the free radical nitric oxide (NO). In glioma cells and the tumor microenvironment, NO is produced by three isoforms of nitric oxide synthase (NOS), NOS1, NOS2, and NOS3. NO and NOS affect glioma growth, invasion, angiogenesis, immunosuppression, differentiation state, and therapeutic resistance.These multifaceted effects of NO and NOS on gliomas both in vitro and in vivo suggest the potential of modulating the pathway for antiglioma patient therapies. Antioxid. Redox Signal. 26, 986-999.

Tumor microenvironments can promote stem cell maintenance, tumor growth, and therapeutic resistance, findings linked by the tumor-initiating cell hypothesis. Standard of care for glioblastoma (GBM) includes temozolomide chemotherapy, which is not curative, due, in part, to residual therapy-resistant brain tumor-initiating cells (BTICs). Temozolomide efficacy may be increased by targeting carbonic anhydrase 9 (CA9), a hypoxia-responsive gene important for maintaining the altered pH gradient of tumor cells. Using patient-derived GBM xenograft cells, we explored whether CA9 and CA12 inhibitor SLC-0111 could decrease GBM growth in combination with temozolomide or influence percentages of BTICs after chemotherapy. In multiple GBMs, SLC-0111 used concurrently with temozolomide reduced cell growth and induced cell cycle arrest via DNA damage in vitro. In addition, this treatment shifted tumor metabolism to a suppressed bioenergetic state in vivo. SLC-0111 also inhibited the enrichment of BTICs after temozolomide treatment determined via CD133 expression and neurosphere formation capacity. GBM xenografts treated with SLC-0111 in combination with temozolomide regressed significantly, and this effect was greater than that of temozolomide or SLC-0111 alone. We determined that SLC-0111 improves the efficacy of temozolomide to extend survival of GBM-bearing mice and should be explored as a treatment strategy in combination with current standard of care.

Development of effective novel anti-tumor treatments will require improved in vitro models that incorporate physiologic microenvironments and maintain intratumoral heterogeneity, including tumor initiating cells. Brain tumor initiating cells (BTIC) are a target for cancer therapy, because BTICs are highly tumorigenic and contribute to tumor angiogenesis, invasion, and therapeutic resistance. Current leading studies rely on BTIC isolation from patient-derived xenografts followed by propagation as neurospheres. As this process is expensive and time-consuming, we determined whether three-dimensional microtumors were an alternative in vitro method for modeling tumor growth via BITC maintenance and/or enrichment. Brain tumor cells were grown as neurospheres or as microtumors produced using the human-derived biomatrix HuBiogel™ and maintained with physiologically relevant microenvironments. BITC percentages were determined using cell surface marker expression, label retention, and neurosphere formation capacity. Our data demonstrate that expansion of brain tumor cells as hypoxic and nutrient-restricted microtumors significantly increased the percentage of both CD133+ and CFSEhigh cells. We further demonstrate that BTIC-marker positive cells isolated from microtumors maintained neurosphere formation capacity in the in vitro limiting dilution assay and tumorigenic potential in vivo. These data demonstrate that microtumors can be a useful three-dimensional biological model for the study of BTIC maintenance and targeting.

Patient prognosis for individuals diagnosed with GBM remains incredibly poor with a median survival of only 15 months despite aggressive treatment with surgical tumor resection, chemotherapy, and radiation therapy. Therapeutic development to prolong survival has been hampered by a high degree of inter- and intra-tumoral heterogeneity. Contributing to tumor heterogeneity is a subset of highly tumorigenic cells, termed brain tumor initiating cells (BTICs), that can self-renew and have been shown to be highly invasive and resistant to therapy. BTICs can survive under nutrient poor conditions due to their increased expression of glucose transporter 3 (GLUT3). In a recently accepted study, we utilized structure based virtual screening (SBVS) using a GLUT3 homology model to identify two novel GLUT inhibitors. We are now generating a structure-activity relationship profile based on a highly efficacious compound (IC(50)= ~300 nM) with the same backbone structure identified in the initial screen and seek to improve the potency, selectivity and drug-like properties of the GLUT inhibitors. We have tested several novel analogs and identified four that have maintained efficacy against BTICs in vitro (IC(50)= 300–600 nM). Importantly, these analogs have displayed less toxicity to astrocytes than lead compounds in addition to improved stability in mouse liver microsomes. As proof of concept, we have begun to test the GLUT inhibitors alone and in combination with chemotherapy in vivo. Thus far, our work has demonstrated that targeting glucose transport is a promising therapeutic avenue to explore.

BACKGROUND Meningioma is the most common primary intracranial tumor, with nearly 30,000 new cases in the US every year. Many meningiomas invade the brain, recur, and become radioresistant, causing severe disability and lethality. Prior work by Sahm et al. showed that meningiomas have consistent patterns of global CpG methylation, and that those patterns are better at prognostic stratification than traditional WHO grading (Lancet Oncol. 2017 May;18(5):682–694). In this study, we hypothesized that specific methylation events could provide further insights as to the signaling pathways driving more aggressive behavior, and identify druggable targets. METHODS We analyzed the Illumina 450k CpG methylation profiles of 493 meningiomas that were published in Lancet Oncology, searching for associations between methylation at individual CpG sites and progression-free survival (PFS). Pathway enrichment analyses were performed using gProfiler and Reactome for genes closest to significant CpG sites, followed by screening for candidate drugs targeting the pathways that were linked with malignant behavior using the ReactomeFIViz Cytoscape Plugin. RESULTS Our analyses revealed 981 genes in which methylation of mapped CpG sites was consistently associated with either shorter PFS (positive hazard ratios (HRs)) or longer PFS (negative HRs) at FDR-adjusted p< 0.05. Methylation of genes encoding proteins involved in G-protein coupled receptor (GPCR) signaling pathways, especially G-alpha (s) and olfactory signaling pathways, showed pronounced association with PFS. We identified 134 anticancer drugs that target the GPCR pathway, including docetaxel and raloxifene hydrochloride, which specifically target G alpha (s) subcomponents. Both are FDA-approved, but no published data exist on their use in meningiomas. CONCLUSIONS This project is advancing our understanding of the molecular pathways driving aggressive behavior in meningioma, and is identifying existing drugs that can be repurposed to treat this tumor.

Glioblastoma multiform (GBM) is the most common primary malignant adult brain tumor and one of the deadliest cancers. Patients with GBM typically undergo surgical resection, radiation and chemotherapy with temozolomide. Complete tumor resection is virtually impossible due to tumor location and the highly infiltrative nature of GBM, which leads to disease recurrence near the original tumor site. As such, these patients have a dramatically decreased life expectancy. Therapeutic development to prolong survival has been hampered by a high degree of inter- and intra-tumoral heterogeneity. Contributing to tumor heterogeneity is a subset of highly tumorigenic cells, termed brain tumor initiating cells (BTICs), that are able to self-renew and can be highly invasive and therapy resistant. BTICs are often enriched in perinecrotic regions, a GBM hallmark, where they can survive under nutrient restriction via increased glucose transporter 3 expression (GLUT3). GLUT3 has a 5-fold greater capacity for glucose transport than the other major glucose transporter isoform in the brain, GLUT1, and is typically restricted to neurons, testis, preimplantation embryos, and stem cells. GLUT3 expression is elevated in many solid tumor types, including GBM, and correlates with poor patient prognosis. Previously, we have shown that knockdown of GLUT3 in BTICs significantly inhibits their growth both in vitro and in vivo, indicating GLUT3 is a possible target for therapeutic intervention. Using structure based virtual screening, we have identified novel GLUT inhibitors that preferentially decrease the growth and glucose uptake of BTICs with minimal toxicity to non-malignant cells in vitro. Preliminary in vivo assessment of these compounds has not indicated toxicity. Our goal is to identify a potential new therapeutic option targeting metabolic reprogramming for the treatment of glioblastoma, as well as other tumor types. Citation Format: Catherine J. Libby, Sixue Zhang, Gloria A. Benavides, Yanjie Li, Matthew Redmann, Anh N. Tran, Arphaxad Otamias, Victor Darley-Usmar, Marek Napierala, Jianhua Zhang, Wei Zhang, Anita Hjelmeland. Novel glucose transporter inhibitors decrease glioblastoma growth and glucose uptake [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1666.

Glioblastoma (GBM), or grade IV astrocytoma, is a deadly disease due in part to the high degree of intratumoral heterogeneity that contributes to treatment failures. Previous studies have shown the importance of reactive species balances, partially controlled by the coupling of nitric oxide synthases (NOS) with their cofactor, in maintenance of glioma stem cell (GSC) phenotype as well as survival of cancer cells in general. In this study, we investigated the roles of GTP cyclohydrolase 1 (GCH1), which is the first and rate-limiting enzyme of the pathway producing of NOS cofactor producing pathway, in GBM stem cell phenotypes via redox balances. We found that GCH1 RNA and protein expression were increased in GSCs in comparison to non-GSCs, but that GCH1 was not exclusive to the GSC fraction. Indeed, GCH1 was elevated in GBM in comparison to normal brain. Overexpression of GCH1 in GBM cells increased cell growth in vitro and neurosphere-forming capability and decreased survival in an intracranial GBM mouse model. In contrast, GCH1 knockdown with short hairpin RNA in GBM cells led to growth inhibition in vitro as well as increased survival in animal models. GCH1 increased CD44 expression and was upregulated in the detrimental mesenchymal GBM subtype in which CD44 served as a marker. Mechanistically, we found that the expression of GCH1 increased BH4 production, as well as augmented multiple antioxidant pathways, including the expression of PARK7, was critical for controlling reactive species balance, including suppressing reactive oxygen species production. In silico analyses demonstrated that higher GCH1 levels in glioma patients correlate with higher glioma grade, recurrence and worse survival. Together, our data suggest that upregulation of GCH1 in GSCs promotes tumor maintenance and is a key regulator of reactive oxygen species in GBM, and GCH1 pathway is a potential target for therapy. Citation Format: Anh N. Tran, Kiera Walker, David G. Harrison, Wei Chen, James Mobley, Lauren Hocevar, James R. Hackney, Randee Sedaka, Jennifer Pollock, Matthew S. Goldberg, Dolores Hambardzumyan, Sara J. Cooper, G Yancey Gillespie, Anita B. Hjelmeland. Glioblastoma, cancer stem cells, and reactive species balances: A case for GTP cyclohydrolase 1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 163.

Glioblastoma (GBM), or grade IV astrocytoma, is a deadly disease due in part to the high degree of intratumoral heterogeneity that contributes to treatment failures. One cellular subset enriched for the capacity to propagate tumor growth and promote therapeutic resistance is brain tumor initiating cells (BTICs). The aim of the study was to define the roles of GTP cyclohydrolase 1 (GCH1) in regulation of BTIC phenotypes via reactive species. We examined GCH1 mRNA and protein expression in patient-derived xenografts, clinical samples and glioma gene expression datasets. GCH1 levels were modulated using lentiviral expression systems, and effects on cell growth, self-renewal, reactive species production and in vitro animal survival were determined. We found that GCH1 RNA and protein expression were increased in BTICs in comparison to non-BTICs, but that GCH1 was not exclusive to the BTIC fraction. Indeed, GCH1 was elevated in GBM in comparison to normal brain. Overexpression of GCH1 in GBM cells increased cell growth in vitro and decreased survival in an intracranial GBM mouse model. In contrast, GCH1 knockdown with short hairpin RNA in GBM cells led to growth inhibition in vitro as well as increased survival in animal models. Mechanistically, GCH1 increased CD44 expression and was critical for controlling reactive species balance, including suppressing reactive oxygen species production. In silico analyses demonstrated that higher GCH1 levels in glioma patients correlate with higher glioma grade, recurrence and worse survival. Together, our data suggest that upregulation of GCH1 in BTICs promotes tumor maintenance and is a key regulator of reactive oxygen species in GBM.

Development of effective novel anti-tumor treatments will require improved in vitro models that incorporate physiologic microenvironments and maintain intratumoral heterogeneity including tumor initiating cells. Brain tumor initiating cells (BTIC) are a target for cancer therapy because they are highly tumorigenic and contribute to tumor angiogenesis, invasion, and therapeutic resistance. Current leading studies rely on BTIC isolation from patient-derived xenografts followed by propagation as neurospheres. As this process is expensive and time-consuming, we determined whether three-dimensional microtumors were an alternative in vitro method for modeling tumor growth via BITC maintenance and/or enrichment. Brain tumor cells were grown as neurospheres or as microtumors produced using a human-derived biomatrix HuBiogelTM and maintained with physiologically relevant microenvironments. Percentages of BITCs were determined based on cell surface marker expression (CD133), label retention (carboxyfluorescein succinimidyl ester; CFSE), and tumorsphere formation capacity. Our data demonstrate that expansion of brain tumor cells as hypoxic and nutrient restricted microtumors significantly increased the percentage of both CD133+ and CFSE+ cells. We further demonstrate that BTIC-marker positive cells isolated from microtumors maintain neurosphere formation capacity in the in vitro limiting dilution assay and tumorigenic potential in vivo. These data demonstrate that microtumors can be a useful three-dimensional biological model for the study of BTIC maintenance and targeting. Citation Format: Ashley Gilbert, Kiera Walker, Anh Tran, Yancey Gillespie, Raj Singh, Anita B. Hjelmeland. Modeling physiologic microenvironments in three-dimensional microtumors facilitates brain tumor initiating cell maintenance [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 1925. doi:10.1158/1538-7445.AM2017-1925

Glioblastomas (GBMs) are the most common primary brain tumors in adults and one of the most aggressive cancers with high rates of recurrence and therapeutic resistance. In GBMs, subpopulations of highly tumorigenic cells called brain tumor initiating cells (BTICs) have been characterized by their unique capacity to promote tumor maintenance, therapeutic resistance, and angiogenesis. BTIC maintenance is known to be regulated by reactive oxygen and nitrogen species. GTP cyclohydrolase, or GCH1, is a critical molecule regulating reactive species levels. We found that expression of GCH1 RNA and protein were upregulated in BTICs in comparison to non-BTICs. Overexpression of GCH1 in glioma cells increased cell growth in vitro and increased tumor formation and decreased survival in an intracranial GBM mouse model. In contrast, GCH1 depletion with short hairpin RNA in GBM cells led to growth inhibition in vitro as well as increased survival in animal orthotopic models. Furthermore, genetic modulation of GCH1 led to altered ROS levels in GBM xenolines. In silico analyses demonstrate that higher GCH1 levels in glioma patients correlate with higher glioma grade, recurrence and worse survival. Together, our data suggest that upregulation of GCH1 in BTICs promotes tumor maintenance and is a key regulator of reactive oxygen species in glioblastoma. Citation Format: Anh N. Tran, Kiera Walker, David Harisson, Wei Chen, James Mobley, Lauren Hocevar, James R. Hackney, Randee S. Sedaka, Jennifer S. Pollock, Sara J. Cooper, George Y. Gillespie, Anita B. Hjelmeland. GTP cyclohydrolase in brain tumor stem cells is implicated in glioblastoma growth [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 5462. doi:10.1158/1538-7445.AM2017-5462