REST REGULATORY CIRCUIT CONTROLS DISTINCT ONCOGENIC PROPERTIES OF GLIOBLASTOMA STEM CELLS THROUGH SPECIFIC MICRORNAs

Glioblastoma Multiforme (GBM) is the most common and aggressive primary malignant brain tumor in adults. With an average survival of only 12-16 months the prognosis for GBM patients remains dismal, with less than 5% of patients surviving 5 years. New mechanism-based approaches are necessary for the management of patients with GBM. Many GBM tumors are believed to be caused by self-renewing, glioblastoma-derived stem-like cells (GSCs). These GSCs are resistant to chemo- and radiation therapies, and are believed to be responsible for tumor recurrence. In a recent paper from our lab we have shown that REST, RE1-silencing transcription factor, regulates oncogenic properties such as proliferation, invasion, and apoptosis in GSCs. However, the mechanism by which REST regulates oncogenic properties of GSCs is not clearly understood. Thus, the overall aim of this project is to delineate the mechanism by which REST mediates oncogenic properties of GSCs. Using genome-wide expression analysis followed by biochemical validations, we show that REST targets two microRNAs, miR-124 and miR-203 in High REST GSCs (HR-GSCs). Independent studies were carried out to determine the role of these microRNAs in HR-GSC derived brain tumors. Gain of function of either miR-124 or miR-203 in HR-GSCs leads to increased survival when tumor cells are transplanted into mice. Importantly, the increased survival of tumor-bearing mice caused by knockdown of Rest in HR-GSCs can be reversed by double knockdown of Rest and miR-124 or miR-203, indicating that the REST-miR-124/miR-203 axis controls tumorigenesis. We further show that the REST-miR-124 axis regulates proliferation, invasion and apoptosis of GSCs both in vitro and in vivo, while the REST-miR-203 axis specifically regulates invasion and not proliferation or apoptosis. Our results indicate that invasion is a major hallmark of HR-GSC tumors and that the REST-miR-124/203 axis is critical in this process. These results also suggest that the REST-miR-124/203 axis could potentially be targeted in therapeutic approaches to block invasion in REST-stratified GBM tumors

Microglia promote glioblastoma via mTOR-mediated immunosuppression of the tumour microenvironment

Tumour-associated microglia/macrophages (TAM) are the most numerous non-neoplastic populations in the tumour microenvironment in glioblastoma multiforme (GBM), the most common malignant brain tumour in adulthood. The mTOR pathway, an important regulator of cell survival/proliferation, is upregulated in GBM, but little is known about the potential role of this pathway in TAM. Here, we show that GBM-initiating cells induce mTOR signalling in the microglia but not bone marrow-derived macrophages in both in vitro and in vivo GBM mouse models. mTOR-dependent regulation of STAT3 and NF-κB activity promotes an immunosuppressive microglial phenotype. This hinders effector T-cell infiltration, proliferation and immune reactivity, thereby contributing to tumour immune evasion and promoting tumour growth in mouse models. The translational value of our results is demonstrated in whole transcriptome datasets of human GBM and in a novel in vitro model, whereby expanded-potential stem cells (EPSC)-derived microglia-like cells are conditioned by syngeneic patient-derived GBM-initiating cells. These results raise the possibility that microglia could be the primary target of mTOR inhibition, rather than the intrinsic tumour cells in GBM

Central nervous system immune interactome is a function of cancer lineage, tumor microenvironment, and STAT3 expression.

BACKGROUNDImmune cell profiling of primary and metastatic CNS tumors has been focused on the tumor, not the tumor microenvironment (TME), or has been analyzed via biopsies.METHODSEn bloc resections of gliomas (n = 10) and lung metastases (n = 10) were analyzed via tissue segmentation and high-dimension Opal 7-color multiplex imaging. Single-cell RNA analyses were used to infer immune cell functionality.RESULTSWithin gliomas, T cells were localized in the infiltrating edge and perivascular space of tumors, while residing mostly in the stroma of metastatic tumors. CD163+ macrophages were evident throughout the TME of metastatic tumors, whereas in gliomas, CD68+, CD11c+CD68+, and CD11c+CD68+CD163+ cell subtypes were commonly observed. In lung metastases, T cells interacted with CD163+ macrophages as dyads and clusters at the brain-tumor interface and within the tumor itself and as clusters within the necrotic core. In contrast, gliomas typically lacked dyad and cluster interactions, except for T cell CD68+ cell dyads within the tumor. Analysis of transcriptomic data in glioblastomas revealed that innate immune cells expressed both proinflammatory and immunosuppressive gene signatures.CONCLUSIONOur results show that immunosuppressive macrophages are abundant within the TME and that the immune cell interactome between cancer lineages is distinct. Further, these data provide information for evaluating the role of different immune cell populations in brain tumor growth and therapeutic responses.FUNDINGThis study was supported by the NIH (NS120547), a Developmental research project award (P50CA221747), ReMission Alliance, institutional funding from Northwestern University and the Lurie Comprehensive Cancer Center, and gifts from the Mosky family and Perry McKay. Performed in the Flow Cytometry & Cellular Imaging Core Facility at MD Anderson Cancer Center, this study received support in part from the NIH (CA016672) and the National Cancer Institute (NCI) Research Specialist award 1 (R50 CA243707). Additional support was provided by CCSG Bioinformatics Shared Resource 5 (P30 CA046592), a gift from Agilent Technologies, a Research Scholar Grant from the American Cancer Society (RSG-16-005-01), a Precision Health Investigator Award from University of Michigan (U-M) Precision Health, the NCI (R37-CA214955), startup institutional research funds from U-M, and a Biomedical Informatics & Data Science Training Grant (T32GM141746)

REST–miR-21–SOX2 axis maintains pluripotency in E14Tg2a.4 embryonic stem cells

Our previous studies have shown that the regulatory network that maintains pluripotency in mouse embryonic stem cells (mESCs) is regulated in a context-dependent manner and can be modulated, at least in part, by re-calibration of an intracellular network of pluripotency factors as well as cues arising from the extracellular matrix. The transcriptional repressor REST represses miR-21 and, thus, regulates self-renewal in E14Tg2a.4 mESCs cultured in the absence of mouse embryonic fibroblast feeder cell effects. However, how miR-21 connects to the nuclear regulatory network has not been clear. Here, we show that miR-21, a direct target of REST-mediated repression, directly targets Sox2. Exogenously added miR-21 to mESCs decreases the expression of Sox2, decreasing mESC self-renewal, and this effect of miR-21 on mESC self-renewal can be blocked by expression of exogenous Sox2. Conversely, destabilization of Sox2 by miR-21 can be blocked by anti-miR-21. Thus, the REST–miR-21–Sox2 axis connects REST to the core nuclear pluripotency regulators in E14Tg2a.4 mESCs cultured in the absence of feeder cells

Opening of the Blood–Brain Barrier Using Low-Intensity Pulsed Ultrasound Enhances Responses to Immunotherapy in Preclinical Glioma Models

International audiencePurpose: The blood-brain barrier (BBB) inhibits adequate dosing/penetration of therapeutic agents to malignancies in the brain. Low-intensity pulsed ultrasound (LIPU) is a safe therapeutic method of temporary BBB disruption (BBBD) to enhance chemotherapeutic delivery to the tumor and surrounding brain parenchyma for treatment of glioblastoma.Experimental design: We investigated if LIPU could enhance therapeutic efficacy of anti-PD-1 in C57BL/6 mice bearing intracranial GL261 gliomas, epidermal growth factor receptor variant III (EGFRvIII) chimeric antigen receptor (CAR) T cells in NSG mice with EGFRvIII-U87 gliomas, and a genetically engineered antigen-presenting cell (APC)-based therapy producing the T-cell attracting chemokine CXCL10 in the GL261-bearing mice.Results: Mice treated with anti-PD-1 and LIPU-induced BBBD had a median survival duration of 58 days compared with 39 days for mice treated with anti-PD-1, and long-term survivors all remained alive after contralateral hemisphere rechallenge. CAR T-cell administration with LIPU-induced BBBD resulted in significant increases in CAR T-cell delivery to the CNS after 24 (P < 0.005) and 72 (P < 0.001) hours and increased median survival by greater than 129%, in comparison with CAR T cells alone. Local deposition of CXCL10-secreting APCs in the glioma microenvironment with LIPU enhanced T-cell glioma infiltration during the therapeutic window (P = 0.004) and markedly enhanced survival (P < 0.05).Conclusions: LIPU increases immune therapeutic delivery to the tumor microenvironment with an associated increase in survival and is an emerging technique for enhancing novel therapies in the brain

Osteopontin mediates glioblastoma-associated macrophage infiltration and is a potential therapeutic target.

Glioblastoma is highly enriched with macrophages, and osteopontin (OPN) expression levels correlate with glioma grade and the degree of macrophage infiltration; thus, we studied whether OPN plays a crucial role in immune modulation. Quantitative PCR, immunoblotting, and ELISA were used to determine OPN expression. Knockdown of OPN was achieved using complementary siRNA, shRNA, and CRISPR/Cas9 techniques, followed by a series of in vitro functional migration and immunological assays. OPN gene-deficient mice were used to examine the roles of non-tumor-derived OPN on survival of mice harboring intracranial gliomas. Patients with mesenchymal glioblastoma multiforme (GBM) show high OPN expression, a negative survival prognosticator. OPN is a potent chemokine for macrophages, and its blockade significantly impaired the ability of glioma cells to recruit macrophages. Integrin αvβ5 (ITGαvβ5) is highly expressed on glioblastoma-infiltrating macrophages and constitutes a major OPN receptor. OPN maintains the M2 macrophage gene signature and phenotype. Both tumor-derived and host-derived OPN were critical for glioma development. OPN deficiency in either innate immune or glioma cells resulted in a marked reduction in M2 macrophages and elevated T cell effector activity infiltrating the glioma. Furthermore, OPN deficiency in the glioma cells sensitized them to direct CD8+ T cell cytotoxicity. Systemic administration in mice of 4-1BB-OPN bispecific aptamers was efficacious, increasing median survival time by 68% (P \u3c 0.05). OPN is thus an important chemokine for recruiting macrophages to glioblastoma, mediates crosstalk between tumor cells and the innate immune system, and has the potential to be exploited as a therapeutic target

Profiling of patients with glioma reveals the dominant immunosuppressive axis is refractory to immune function restoration

In order to prioritize available immune therapeutics, immune profiling across glioma grades was conducted, followed by preclinical determinations of therapeutic effect in immune-competent mice harboring gliomas. T cells and myeloid cells were isolated from the blood of healthy donors and the blood and tumors from patients with glioma and profiled for the expression of immunomodulatory targets with an available therapeutic. Murine glioma models were used to assess therapeutic efficacy of agents targeting the most frequently expressed immune targets. In patients with glioma, the A2aR/CD73/CD39 pathway was most frequently expressed, followed by the PD-1 pathway. CD73 expression was upregulated on immune cells by 2-hydroxyglutarate in IDH1 mutant glioma patients. In murine glioma models, adenosine receptor inhibitors demonstrated a modest therapeutic response; however, the addition of other inhibitors of the adenosine pathway did not further enhance this therapeutic effect. Although adenosine receptor inhibitors could recover immunological effector functions in T cells, immune recovery was impaired in the presence of gliomas, indicating that irreversible immune exhaustion limits the effectiveness of adenosine pathway inhibitors in patients with glioma. This study illustrates vetting steps that should be considered before clinical trial implementation for immunotherapy-resistant cancers, including testing an agent’s ability to restore immunological function in the context of intended use