Publications by authors named "Martina Ott"

31 Publications

The Role and Therapeutic Targeting of JAK/STAT Signaling in Glioblastoma.

Cancers (Basel) 2021 Jan 24;13(3). Epub 2021 Jan 24.

Department of Neurosurgery, University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA.

Glioblastoma remains one of the deadliest and treatment-refractory human malignancies in large part due to its diffusely infiltrative nature, molecular heterogeneity, and capacity for immune escape. The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway contributes substantively to a wide variety of protumorigenic functions, including proliferation, anti-apoptosis, angiogenesis, stem cell maintenance, and immune suppression. We review the current state of knowledge regarding the biological role of JAK/STAT signaling in glioblastoma, therapeutic strategies, and future directions for the field.
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http://dx.doi.org/10.3390/cancers13030437DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7865703PMC
January 2021

MiR-181 Family Modulates Osteopontin in Glioblastoma Multiforme.

Cancers (Basel) 2020 Dec 17;12(12). Epub 2020 Dec 17.

Department of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.

MiRNAs can silence a wide range of genes, which may be an advantage for targeting heterogenous tumors like glioblastoma. Osteopontin (OPN) plays both an oncogenic role in a variety of cancers and can immune modulate macrophages. We conducted a genome wide profiling and bioinformatic analysis to identify miR-181a/b/c/d as potential miRNAs that target OPN. Luciferase assays confirmed the binding potential of miRNAs to OPN. Expression levels of miR-181a/b/c/d and OPN were evaluated by using quantitative real-time PCR and enzyme-linked immunosorbent assay in mouse and human glioblastomas and macrophages that showed these miRNAs were downregulated in Glioblastoma associated CD11b+ cells compared to their matched blood CD14b+ cells. miRNA mimicking and overexpression using lentiviruses showed that MiR-181a overexpression in glioblastoma cells led to decreased OPN production and proliferation and increased apoptosis in vitro. MiR-181a treatment of immune competent mice bearing intracranial glioblastoma demonstrated a 22% increase in median survival duration relative to that of control mice.
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http://dx.doi.org/10.3390/cancers12123813DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7765845PMC
December 2020

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

JCI Insight 2020 09 3;5(17). Epub 2020 Sep 3.

Department of Neurosurgery.

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.
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http://dx.doi.org/10.1172/jci.insight.134386DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7526457PMC
September 2020

Radiation with STAT3 Blockade Triggers Dendritic Cell-T cell Interactions in the Glioma Microenvironment and Therapeutic Efficacy.

Clin Cancer Res 2020 Sep 30;26(18):4983-4994. Epub 2020 Jun 30.

Department of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, Texas.

Purpose: Patients with central nervous system (CNS) tumors are typically treated with radiotherapy, but this is not curative and results in the upregulation of phosphorylated STAT3 (p-STAT3), which drives invasion, angiogenesis, and immune suppression. Therefore, we investigated the combined effect of an inhibitor of STAT3 and whole-brain radiotherapy (WBRT) in a murine model of glioma.

Experimental Design: C57BL/6 mice underwent intracerebral implantation of GL261 glioma cells, WBRT, and treatment with WP1066, a blood-brain barrier-penetrant inhibitor of the STAT3 pathway, or the two in combination. The role of the immune system was evaluated using tumor rechallenge strategies, immune-incompetent backgrounds, immunofluorescence, immune phenotyping of tumor-infiltrating immune cells (via flow cytometry), and NanoString gene expression analysis of 770 immune-related genes from immune cells, including those directly isolated from the tumor microenvironment.

Results: The combination of WP1066 and WBRT resulted in long-term survivors and enhanced median survival time relative to monotherapy in the GL261 glioma model (combination vs. control < 0.0001). Immunologic memory appeared to be induced, because mice were protected during subsequent tumor rechallenge. The therapeutic effect of the combination was completely lost in immune-incompetent animals. NanoString analysis and immunofluorescence revealed immunologic reprograming in the CNS tumor microenvironment specifically affecting dendritic cell antigen presentation and T-cell effector functions.

Conclusions: This study indicates that the combination of STAT3 inhibition and WBRT enhances the therapeutic effect against gliomas in the CNS by inducing dendritic cell and T-cell interactions in the CNS tumor.
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http://dx.doi.org/10.1158/1078-0432.CCR-19-4092DOI Listing
September 2020

Anti-PD-1 Induces M1 Polarization in the Glioma Microenvironment and Exerts Therapeutic Efficacy in the Absence of CD8 Cytotoxic T Cells.

Clin Cancer Res 2020 Sep 18;26(17):4699-4712. Epub 2020 Jun 18.

Department of Neurosurgery, Baylor College of Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas.

Purpose: Anti-programmed cell death protein 1 (PD-1) therapy has demonstrated inconsistent therapeutic results in patients with glioblastoma (GBM) including those with profound impairments in CD8 T-cell effector responses.

Experimental Design: We ablated the gene in BL6 mice and intercrossed them with Ntv-a mice to determine how CD8 T cells affect malignant progression in forming endogenous gliomas. Tumor-bearing mice were treated with PD-1 to determine the efficacy of this treatment in the absence of T cells. The tumor microenvironment of treated and control mice was analyzed by IHC and FACS.

Results: We observed a survival benefit in immunocompetent mice with endogenously arising intracranial glioblastomas after intravenous administration of anti-PD-1. The therapeutic effect of PD-1 administration persisted in mice even after genetic ablation of the CD8 gene (CD8). CD11b and Iba1 monocytes and macrophages were enriched in the glioma microenvironment of the CD8 mice. The macrophages and microglia assumed a proinflammatory M1 response signature in the setting of anti-PD-1 blockade through the elimination of PD-1-expressing macrophages and microglia in the tumor microenvironment. Anti-PD-1 can inhibit the proliferation of and induce apoptosis of microglia through antibody-dependent cellular cytotoxicity, as fluorescently labeled anti-PD-1 was shown to gain direct access to the glioma microenvironment.

Conclusions: Our results show that the therapeutic effect of anti-PD-1 blockade in GBM may be mediated by the innate immune system, rather than by CD8 T cells. Anti-PD-1 immunologically modulates innate immunity in the glioma microenvironment-likely a key mode of activity.
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http://dx.doi.org/10.1158/1078-0432.CCR-19-4110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7483850PMC
September 2020

Pre-treatment with the viral Toll-like receptor 3 agonist poly(I:C) modulates innate immunity and protects neutropenic mice infected intracerebrally with Escherichia coli.

J Neuroinflammation 2020 Jan 17;17(1):24. Epub 2020 Jan 17.

Institute of Neuropathology, University Medical Center Göttingen, Robert-Koch-Strasse 40, 37075, Göttingen, Germany.

Background: Individuals with impaired immunity are more susceptible to infections than immunocompetent subjects. No vaccines are currently available to induce protection against E. coli meningoencephalitis. This study evaluated the potential of poly(I:C) pre-treatment to induce trained immunity. Poly(I:C) was administered as a non-specific stimulus of innate immune responses to protect immunocompetent and neutropenic wild-type mice from a subsequent challenge by the intracranial injection of E. coli K1.

Methods: Three days prior to infection, mice received an intraperitoneal injection of poly(I:C) or vehicle. Kaplan-Meier survival curves were analyzed. In short-term experiments, bacterial titers and the inflammatory response were characterized in the blood, cerebellum, and spleen homogenates. NK cell subpopulations in the brain and spleen were analyzed by flow cytometry. Numbers of microglia and activation scores were evaluated by histopathology.

Results: Pre-treatment with 200 μg poly(I:C) increased survival time, reduced mortality, and enhanced bacterial clearance in the blood, cerebellum, and spleen at early infection in neutropenic mice. Poly(I:C)-mediated protection correlated with an augmented number of NK cells (CD45NK1.1CD3) and Iba-1 microglial cells and a higher production of IFN-γ in the brain. In the spleen, levels of CCL5/RANTES and IFN-γ were increased and sustained in surviving poly(I:C)-treated animals for 14 days after infection. In immunocompetent animals, survival time was not significantly prolonged in poly(I:C)-treated animals although poly(I:C) priming reduced brain bacterial concentrations compared with vehicle-injected animals at early infection.

Conclusions: Pre-treatment with the viral TLR3 agonist poly(I:C) modulated innate immune responses and strengthened the resistance of neutropenic mice against E. coli K1 meningoencephalitis.
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http://dx.doi.org/10.1186/s12974-020-1700-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6969464PMC
January 2020

Immune profiling of human tumors identifies CD73 as a combinatorial target in glioblastoma.

Nat Med 2020 01 23;26(1):39-46. Epub 2019 Dec 23.

Department of Genitourinary Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.

Immune checkpoint therapy with anti-CTLA-4 and anti-PD-1/PD-L1 has revolutionized the treatment of many solid tumors. However, the clinical efficacy of immune checkpoint therapy is limited to a subset of patients with specific tumor types. Multiple clinical trials with combinatorial immune checkpoint strategies are ongoing; however, the mechanistic rationale for tumor-specific targeting of immune checkpoints is elusive. To garner an insight into tumor-specific immunomodulatory targets, we analyzed 94 patients representing five different cancer types, including those that respond relatively well to immune checkpoint therapy and those that do not, such as glioblastoma multiforme, prostate cancer and colorectal cancer. Through mass cytometry and single-cell RNA sequencing, we identified a unique population of CD73 macrophages in glioblastoma multiforme that persists after anti-PD-1 treatment. To test if targeting CD73 would be important for a successful combination strategy in glioblastoma multiforme, we performed reverse translational studies using CD73 mice. We found that the absence of CD73 improved survival in a murine model of glioblastoma multiforme treated with anti-CTLA-4 and anti-PD-1. Our data identified CD73 as a specific immunotherapeutic target to improve antitumor immune responses to immune checkpoint therapy in glioblastoma multiforme and demonstrate that comprehensive human and reverse translational studies can be used for rational design of combinatorial immune checkpoint strategies.
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http://dx.doi.org/10.1038/s41591-019-0694-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7182038PMC
January 2020

Immune biology of glioma-associated macrophages and microglia: functional and therapeutic implications.

Neuro Oncol 2020 02;22(2):180-194

Departments of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, Texas.

CNS immune defenses are marshaled and dominated by brain resident macrophages and microglia, which are the innate immune sentinels and frontline host immune barriers against various pathogenic insults. These myeloid lineage cells are the predominant immune population in gliomas and can constitute up to 30-50% of the total cellular composition. Parenchymal microglial cells and recruited monocyte-derived macrophages from the periphery exhibit disease-specific phenotypic characteristics with spatial and temporal distinctions and are heterogeneous subpopulations based on their molecular signatures. A preponderance of myeloid over lymphoid lineage cells during CNS inflammation, including gliomas, is a contrasting feature of brain immunity relative to peripheral immunity. Herein we discuss glioma-associated macrophage and microglia immune biology in the context of their identity, molecular drivers of recruitment, nomenclature and functional paradoxes, therapeutic reprogramming and polarization strategies, relevant challenges, and our perspectives on therapeutic modulation.
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http://dx.doi.org/10.1093/neuonc/noz212DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7442334PMC
February 2020

Laquinimod, a prototypic quinoline-3-carboxamide and aryl hydrocarbon receptor agonist, utilizes a CD155-mediated natural killer/dendritic cell interaction to suppress CNS autoimmunity.

J Neuroinflammation 2019 Feb 26;16(1):49. Epub 2019 Feb 26.

Institute of Neuropathology, University Medical Center Göttingen, Göttingen, Germany.

Background: Quinoline-3-carboxamides, such as laquinimod, ameliorate CNS autoimmunity in patients and reduce tumor cell metastasis experimentally. Previous studies have focused on the immunomodulatory effect of laquinimod on myeloid cells. The data contained herein suggest that quinoline-3-carboxamides improve the immunomodulatory and anti-tumor effects of NK cells by upregulating the adhesion molecule DNAX accessory molecule-1 (DNAM-1).

Methods: We explored how NK cell activation by laquinimod inhibits CNS autoimmunity in experimental autoimmune encephalomyelitis (EAE), the most utilized model of MS, and improves immunosurveillance of experimental lung melanoma metastasis. Functional manipulations included in vivo NK and DC depletion experiments and in vitro assays of NK cell function. Clinical, histological, and flow cytometric read-outs were assessed.

Results: We demonstrate that laquinimod activates natural killer (NK) cells via the aryl hydrocarbon receptor and increases their DNAM-1 cell surface expression. This activation improves the cytotoxicity of NK cells against B16F10 melanoma cells and augments their immunoregulatory functions in EAE by interacting with CD155 dendritic cells (DC). Noteworthy, the immunosuppressive effect of laquinimod-activated NK cells was due to decreasing MHC class II antigen presentation by DC and not by increasing DC killing.

Conclusions: This study clarifies how DNAM-1 modifies the bidirectional crosstalk of NK cells with CD155 DC, which can be exploited to suppress CNS autoimmunity and strengthen tumor surveillance.
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http://dx.doi.org/10.1186/s12974-019-1437-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6390632PMC
February 2019

Author Correction: FGL2 promotes tumor progression in the CNS by suppressing CD103 dendritic cell differentiation.

Nat Commun 2019 02 15;10(1):862. Epub 2019 Feb 15.

Department of Pediatrics-Research, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.

The original version of this Article contained errors in the author affiliations. Qingnan Zhao, Xueqing Xia, Longfei Huo and Shulin Li were incorrectly associated with Beijing Institute for Brain Disorders, 100069, Beijing, China.This has now been corrected in both the PDF and HTML versions of the Article.
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http://dx.doi.org/10.1038/s41467-019-08770-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6377651PMC
February 2019

FGL2 promotes tumor progression in the CNS by suppressing CD103 dendritic cell differentiation.

Nat Commun 2019 01 25;10(1):448. Epub 2019 Jan 25.

Department of Pediatrics-Research, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.

Few studies implicate immunoregulatory gene expression in tumor cells in arbitrating brain tumor progression. Here we show that fibrinogen-like protein 2 (FGL2) is highly expressed in glioma stem cells and primary glioblastoma (GBM) cells. FGL2 knockout in tumor cells did not affect tumor-cell proliferation in vitro or tumor progression in immunodeficient mice but completely impaired GBM progression in immune-competent mice. This impairment was reversed in mice with a defect in dendritic cells (DCs) or CD103 DC differentiation in the brain and in tumor-draining lymph nodes. The presence of FGL2 in tumor cells inhibited granulocyte-macrophage colony-stimulating factor (GM-CSF)-induced CD103 DC differentiation by suppressing NF-κB, STAT1/5, and p38 activation. These findings are relevant to GBM patients because a low level of FGL2 expression with concurrent high GM-CSF expression is associated with higher CD8B expression and longer survival. These data provide a rationale for therapeutic inhibition of FGL2 in brain tumors.
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http://dx.doi.org/10.1038/s41467-018-08271-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6347641PMC
January 2019

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

J Clin Invest 2019 01 19;129(1):137-149. Epub 2018 Nov 19.

Department of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.

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 < 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.
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http://dx.doi.org/10.1172/JCI121266DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6307970PMC
January 2019

Author Correction: Fourier Transform Infrared Microscopy Enables Guidance of Automated Mass Spectrometry Imaging to Predefined Tissue Morphologies.

Sci Rep 2018 Apr 18;8(1):6361. Epub 2018 Apr 18.

Center for Applied Research in Applied Biomedical Mass Spectrometry (ABIMAS), Mannheim University of Applied Sciences, Paul-Wittsack Str. 10, 68163, Mannheim, Germany.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.
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http://dx.doi.org/10.1038/s41598-018-24807-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5906574PMC
April 2018

Glioblastoma stem cell-derived exosomes induce M2 macrophages and PD-L1 expression on human monocytes.

Oncoimmunology 2018;7(4):e1412909. Epub 2018 Jan 16.

Departments of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.

Exosomes can mediate a dynamic method of communication between malignancies, including those sequestered in the central nervous system and the immune system. We sought to determine whether exosomes from glioblastoma (GBM)-derived stem cells (GSCs) can induce immunosuppression. We report that GSC-derived exosomes (GDEs) have a predilection for monocytes, the precursor to macrophages. The GDEs traverse the monocyte cytoplasm, cause a reorganization of the actin cytoskeleton, and skew monocytes toward the immune suppresive M2 phenotype, including programmed death-ligand 1 (PD-L1) expression. Mass spectrometry analysis demonstrated that the GDEs contain a variety of components, including members of the signal transducer and activator of transcription 3 (STAT3) pathway that functionally mediate this immune suppressive switch. Western blot analysis revealed that upregulation of PD-L1 in GSC exosome-treated monocytes and GBM-patient-infiltrating CD14 cells predominantly correlates with increased phosphorylation of STAT3, and in some cases, with phosphorylated p70S6 kinase and Erk1/2. Cumulatively, these data indicate that GDEs are secreted GBM-released factors that are potent modulators of the GBM-associated immunosuppressive microenvironment.
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http://dx.doi.org/10.1080/2162402X.2017.1412909DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5889290PMC
January 2018

Translating Immunopeptidomics to Immunotherapy-Decision-Making for Patient and Personalized Target Selection.

Proteomics 2018 06 10;18(12):e1700284. Epub 2018 Apr 10.

Immatics Biotechnologies, Tübingen, Germany.

Immunotherapy is revolutionizing cancer treatment and has shown success in particular for tumors with a high mutational load. These effects have been linked to neoantigens derived from patient-specific mutations. To expand efficacious immunotherapy approaches to the vast majority of tumor types and patient populations carrying only a few mutations and maybe not a single presented neoepitope, it is necessary to expand the target space to non-mutated cancer-associated antigens. Mass spectrometry enables the direct and unbiased discovery and selection of tumor-specific human leukocyte antigen (HLA) peptides that can be used to define targets for immunotherapy. Combining these targets into a warehouse allows for multi-target therapy and accelerated clinical application. For precise personalization aimed at optimally ensuring treatment efficacy and safety, it is necessary to assess the presence of the target on each individual patient's tumor. Here we show how LC-MS paired with gene expression data was used to define mRNA biomarkers currently being used as diagnostic test IMADETECT™ for patient inclusion and personalized target selection within two clinical trials (NCT02876510, NCT03247309). Thus, we present a way how to translate HLA peptide presentation into gene expression thresholds for companion diagnostics in immunotherapy considering the peptide-specific correlation to its encoding mRNA.
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http://dx.doi.org/10.1002/pmic.201700284DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6032917PMC
June 2018

Fourier Transform Infrared Microscopy Enables Guidance of Automated Mass Spectrometry Imaging to Predefined Tissue Morphologies.

Sci Rep 2018 01 10;8(1):313. Epub 2018 Jan 10.

Center for Applied Research in Applied Biomedical Mass Spectrometry (ABIMAS), Mannheim University of Applied Sciences, Paul-Wittsack Str. 10, 68163, Mannheim, Germany.

Multimodal imaging combines complementary platforms for spatially resolved tissue analysis that are poised for application in life science and personalized medicine. Unlike established clinical in vivo multimodality imaging, automated workflows for in-depth multimodal molecular ex vivo tissue analysis that combine the speed and ease of spectroscopic imaging with molecular details provided by mass spectrometry imaging (MSI) are lagging behind. Here, we present an integrated approach that utilizes non-destructive Fourier transform infrared (FTIR) microscopy and matrix assisted laser desorption/ionization (MALDI) MSI for analysing single-slide tissue specimen. We show that FTIR microscopy can automatically guide high-resolution MSI data acquisition and interpretation without requiring prior histopathological tissue annotation, thus circumventing potential human-annotation-bias while achieving >90% reductions of data load and acquisition time. We apply FTIR imaging as an upstream modality to improve accuracy of tissue-morphology detection and to retrieve diagnostic molecular signatures in an automated, unbiased and spatially aware manner. We show the general applicability of multimodal FTIR-guided MALDI-MSI by demonstrating precise tumor localization in mouse brain bearing glioma xenografts and in human primary gastrointestinal stromal tumors. Finally, the presented multimodal tissue analysis method allows for morphology-sensitive lipid signature retrieval from brains of mice suffering from lipidosis caused by Niemann-Pick type C disease.
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http://dx.doi.org/10.1038/s41598-017-18477-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5762902PMC
January 2018

K27M-mutant histone-3 as a novel target for glioma immunotherapy.

Oncoimmunology 2017;6(7):e1328340. Epub 2017 May 12.

Department of Neurology, University Hospital Heidelberg, Heidelberg, Germany.

Mutation-specific vaccines have become increasingly important in glioma immunotherapy; however, shared neoepitopes are rare. For diffuse gliomas, a driver mutation in the gene for isocitrate dehydrogenase type-1 has been shown to produce an immunogenic epitope currently targeted in clinical trials. For highly aggressive midline gliomas, a recurrent point mutation in the histone-3 gene () causes an amino acid change from lysine to methionine at position 27 (K27M). Here, we demonstrate that a peptide vaccine against K27M-mutant histone-3 is capable of inducing effective, mutation-specific, cytotoxic T-cell- and T-helper-1-cell-mediated immune responses in a major histocompatibility complex (MHC)-humanized mouse model. By proving an immunologically effective presentation of the driver mutation H3K27M on MHC class II in human H3K27M-mutant gliomas, our data provide a basis for the further clinical development of vaccine-based or cell-based immunotherapeutic approaches targeting H3K27M.
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http://dx.doi.org/10.1080/2162402X.2017.1328340DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5543817PMC
May 2017

Mutational burden, immune checkpoint expression, and mismatch repair in glioma: implications for immune checkpoint immunotherapy.

Neuro Oncol 2017 Aug;19(8):1047-1057

Department of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, Texas; Caris Life Sciences, Phoenix, Arizona; Departments of Biostatistics, Neuro-Pathology, Neuro-Oncology, Pediatrics, and Melanoma Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.

Background: Despite a multiplicity of clinical trials testing immune checkpoint inhibitors, the frequency of expression of potential predictive biomarkers is unknown in glioma.

Methods: In this study, we profiled the frequency of shared biomarker phenotypes. To clarify the relationships among tumor mutational load (TML), mismatch repair (MMR), and immune checkpoint expression, we profiled patients with glioma (n = 327), including glioblastoma (GBM) (n = 198), whose samples had been submitted for analysis from 2009 to 2016. The calculation algorithm for TML included nonsynonymous mutation counts per tumor, with germline mutations filtered out. Immunohistochemical analysis and next-generation sequencing were used to determine tumor-infiltrating lymphocyte expression positive for programmed cell death protein 1 (PD-1), PD ligand 1 (PD-L1) expression on tumor cells, MMR (MLH1, MSH2, MSH6, and PMS2) protein expression and mutations, and DNA polymerase epsilon (POLE) mutations.

Results: High TML was only found in 3.5% of GBM patients (7 of 198) and was associated with the absence of protein expression of mutL homolog 1 (MLH1) (P = .0345), mutS homolog 2 (MSH2) (P = .0099), MSH6 (P = .0022), and postmeiotic segregation increased 2 (PMS2) (P = .0345) and the presence of DNA MMR mutations. High and moderate TML GBMs did not have an enriched influx of CD8+ T cells, PD-1+ T cells, or tumor-expressed PD-L1. IDH1 mutant gliomas were not enriched for high TML, PD-1+ T cells, or PD-L1 expression.

Conclusions: To clarify the relationships among TML, MMR, and immune checkpoint expression, we profiled the frequency of shared biomarker phenotypes. On the basis of a variety of potential biomarkers of response to immune checkpoints, only small subsets of glioma patients are likely to benefit from monotherapy immune checkpoint inhibition.
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http://dx.doi.org/10.1093/neuonc/nox026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5570198PMC
August 2017

Mechanisms of efficacy in cancer immunotherapy: 14th Annual Meeting of the Association for Cancer Immunotherapy (CIMT), Mainz, Germany, May 10-12, 2016.

Cancer Immunol Immunother 2017 05 1;66(5):673-681. Epub 2017 Mar 1.

BioNTech AG, Kupferbergterrasse 17-19, 55131, Mainz, Germany.

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http://dx.doi.org/10.1007/s00262-017-1974-2DOI Listing
May 2017

Pan-mutant IDH1 inhibitor BAY 1436032 for effective treatment of IDH1 mutant astrocytoma in vivo.

Acta Neuropathol 2017 04 25;133(4):629-644. Epub 2017 Jan 25.

German Consortium of Translational Cancer Research (DKTK), Clinical Cooperation Unit Neuropathology, German Cancer Research Center (DKFZ), Heidelberg, Germany.

Mutations in codon 132 of isocitrate dehydrogenase (IDH) 1 are frequent in diffuse glioma, acute myeloid leukemia, chondrosarcoma and intrahepatic cholangiocarcinoma. These mutations result in a neomorphic enzyme specificity which leads to a dramatic increase of intracellular D-2-hydroxyglutarate (2-HG) in tumor cells. Therefore, mutant IDH1 protein is a highly attractive target for inhibitory drugs. Here, we describe the development and properties of BAY 1436032, a pan-inhibitor of IDH1 protein with different codon 132 mutations. BAY 1436032 strongly reduces 2-HG levels in cells carrying IDH1-R132H, -R132C, -R132G, -R132S and -R132L mutations. Cells not carrying IDH mutations were unaffected. BAY 1436032 did not exhibit toxicity in vitro or in vivo. The pharmacokinetic properties of BAY 1436032 allow for oral administration. In two independent experiments, BAY 1436032 has been shown to significantly prolong survival of mice intracerebrally transplanted with human astrocytoma carrying the IDH1R132H mutation. In conclusion, we developed a pan-inhibitor targeting tumors with different IDH1R132 mutations.
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http://dx.doi.org/10.1007/s00401-017-1677-yDOI Listing
April 2017

The stress kinase GCN2 does not mediate suppression of antitumor T cell responses by tryptophan catabolism in experimental melanomas.

Oncoimmunology 2016;5(12):e1240858. Epub 2016 Nov 15.

DKTK CCU Neuroimmunology and Brain Tumor Immunology, DKFZ, Heidelberg, Germany; Department of Neurology and National Center of Tumor Diseases, University Hospital Heidelberg, Heidelberg, Germany; Department of Neurology, University Medical Center Mannheim, Heidelberg University, Mannheim, Germany.

Tryptophan metabolism is a key process that shapes the immunosuppressive tumor microenvironment. The two rate-limiting enzymes that mediate tryptophan depletion, indoleamine-2,3-dioxygenase (IDO) and tryptophan-2,3-dioxygenase (TDO), have moved into the focus of research and inhibitors targeting IDO and TDO have entered clinical trials. Local tryptophan depletion is generally viewed as the crucial immunosuppressive mechanism. In T cells, the kinase general control non-derepressible 2 (GCN2) has been identified as a molecular sensor of tryptophan deprivation. GCN2 activation by tryptophan depletion induces apoptosis and mitigates T cell proliferation. Here, we investigated whether GCN2 attenuates tumor rejection in experimental B16 melanoma using T cell-specific knockout mice. Our data demonstrate that GCN2 in T cells did not affect immunity to B16 tumors even when animals were treated with antibodies targeting cytotoxic T lymphocyte antigen-4 (CTLA4). GCN2-deficient gp100 TCR-transgenic T cells were equally effective as wild-type pmel T cells against gp100-expressing B16 melanomas after adoptive transfer and gp100 peptide vaccination. Even augmentation of tumoral tryptophan metabolism in B16 tumors by lentiviral overexpression of did not differentially affect GCN2-proficient vs. GCN2-deficient T cells . Importantly, GCN2 target genes were not upregulated in tumor-infiltrating T cells. MALDI-TOF MS imaging of B16 melanomas demonstrated maintenance of intratumoral tryptophan levels despite high tryptophan turnover, which prohibits a drop in tryptophan sufficient to activate GCN2 in tumor-infiltrating T cells. In conclusion, our results do not suggest that suppression of antitumor immune responses by tryptophan metabolism is driven by local tryptophan depletion and subsequent GCN2-mediated T cell anergy.
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http://dx.doi.org/10.1080/2162402X.2016.1240858DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5214097PMC
November 2016

Slowing down glioblastoma progression in mice by running or the anti-malarial drug dihydroartemisinin? Induction of oxidative stress in murine glioblastoma therapy.

Oncotarget 2016 Aug;7(35):56713-56725

German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), Heidelberg, Germany.

Influencing cancer metabolism by lifestyle changes is an attractive strategy as - if effective - exercise-induced problems may be less severe than those induced by classical anti-cancer therapies. Pursuing this idea, clinical trials evaluated the benefit of e.g. different diets such as the ketogenic diet, intermittent caloric restriction and physical exercise (PE) in the primary and secondary prevention of different cancer types. PE proved to be beneficial in the context of breast and colon cancer.Glioblastoma has a dismal prognosis, with an average overall survival of about one year despite maximal safe resection, concomitant radiochemotherapy with temozolomide followed by adjuvant temozolomide therapy. Here, we focused on the influence of PE as an isolated and adjuvant treatment in murine GB therapy.PE did not reduce toxic side effects of chemotherapy in mice administered in a dose escalating scheme as shown before for starvation. Although regular treadmill training on its own had no obvious beneficial effects, its combination with temozolomide was beneficial in the treatment of glioblastoma-bearing mice. As PE might partly act through the induction of reactive oxygen species, dihydroartemisinin - an approved anti-malarial drug which induces oxidative stress in glioma cells - was further evaluated in vitro and in vivo. Dihydroartemisinin showed anti-glioma activity by promoting autophagy, reduced the clonogenic survival and proliferation capacity of glioma cells, and prolonged the survival of tumor bearing mice. Using the reactive oxygen species scavenger n-acetyl-cysteine these effects were in part reversible, suggesting that dihydroartemisinin partly acts through the generation of reactive oxygen species.
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http://dx.doi.org/10.18632/oncotarget.10723DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5302947PMC
August 2016

Correlated magnetic resonance imaging and ultramicroscopy (MR-UM) is a tool kit to assess the dynamics of glioma angiogenesis.

Elife 2016 Feb 2;5:e11712. Epub 2016 Feb 2.

Schaller Research Group, University of Heidelberg and German Cancer Research Center, Heidelberg, Germany.

Neoangiogenesis is a pivotal therapeutic target in glioblastoma. Tumor monitoring requires imaging methods to assess treatment effects and disease progression. Until now mapping of the tumor vasculature has been difficult. We have developed a combined magnetic resonance and optical toolkit to study neoangiogenesis in glioma models. We use in vivo magnetic resonance imaging (MRI) and correlative ultramicroscopy (UM) of ex vivo cleared whole brains to track neovascularization. T2* imaging allows the identification of single vessels in glioma development and the quantification of neovessels over time. Pharmacological VEGF inhibition leads to partial vascular normalization with decreased vessel caliber, density, and permeability. To further resolve the tumor microvasculature, we performed correlated UM of fluorescently labeled microvessels in cleared brains. UM resolved typical features of neoangiogenesis and tumor cell invasion with a spatial resolution of ~5 µm. MR-UM can be used as a platform for three-dimensional mapping and high-resolution quantification of tumor angiogenesis.
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http://dx.doi.org/10.7554/eLife.11712DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4755755PMC
February 2016

Tryptophan-2,3-dioxygenase is regulated by prostaglandin E2 in malignant glioma via a positive signaling loop involving prostaglandin E receptor-4.

J Neurochem 2016 Mar 22;136(6):1142-1154. Epub 2016 Jan 22.

Department of Neurology, University Hospital Heidelberg and National Center for Tumor Diseases, Heidelberg, Germany.

Malignant gliomas and other types of tumors generate a local immunosuppressive microenvironment, which prohibits an effective anti-tumor immune response and promotes tumor growth. Along with others, we have recently demonstrated that catabolism of the essential amino acid tryptophan via tryptophan-2,3-dioxygenase (TDO) is an important mechanism mediating tumor-associated immunosuppression particularly in gliomas. The pathways regulating TDO in tumors, however, are poorly understood. Here, we show that prostaglandins enhance TDO expression and enzymatic activity in malignant gliomas via activation of prostaglandin E receptor-4 (EP4). Stimulation with prostaglandin E (PGE ) up-regulated TDO-mediated kynurenine release in human glioma cell lines, whereas knockdown of the PGE receptor EP4 inhibited TDO expression and activity. In human malignant glioma tissue expression of the PGE -producing enzyme cyclooxygenase-2 (COX2) and its receptor EP4 were associated with TDO expression both on transcript and protein level. High expression of EP4 correlated with poor survival in malignant glioma patients WHO III-IV. Importantly, treatment of glioma cells with an EP4 inhibitor decreased TDO expression and activity. Moreover, TDO-over-expressing murine gliomas showed increased COX2 and EP4 expression suggesting a positive feedback mechanism in vivo. In summary, targeting EP4 may inhibit - in addition to immunosuppressive COX2 signaling - tryptophan degradation as another important immunosuppressive pathway and thus, could provide a dual clinically relevant immunotherapeutic avenue for the treatment of malignant gliomas. We proposed that in malignant gliomas prostaglandin E (PGE ) produced by cyclooxygenases (COX) up-regulates tryptophan-2,3-dioxygenase (TDO) expression and enzyme activity through binding to its Gs-coupled receptor EP4 and therefore may mediate tumor immune escape in part through aryl hydrocarbon receptor (AHR) activation. Moreover, TDO activity itself seems to induce intratumoral PGE metabolism suggesting an immunosuppressive loop involving COX/EP4/TDO.
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http://dx.doi.org/10.1111/jnc.13503DOI Listing
March 2016

Suppression of TDO-mediated tryptophan catabolism in glioblastoma cells by a steroid-responsive FKBP52-dependent pathway.

Glia 2015 Jan 5;63(1):78-90. Epub 2014 Aug 5.

German Cancer Consortium (DKTK) Clinical Cooperation Unit Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Department of Neurooncology, University Hospital Heidelberg and National Center for Tumor Diseases, Heidelberg, Germany.

Tryptophan catabolism is increasingly recognized as a key and druggable molecular mechanism active in cancer, immune, and glioneural cells and involved in the modulation of antitumor immunity, autoimmunity and glioneural function. In addition to the pivotal rate limiting enzyme indoleamine-2,3-dioxygenase, expression of tryptophan-2,3-dioxygenase (TDO) has recently been described as an alternative pathway responsible for constitutive tryptophan degradation in malignant gliomas and other types of cancer. In addition, TDO has been implicated as a key regulator of neurotoxicity involved in neurodegenerative diseases and ageing. The pathways regulating TDO expression, however, are largely unknown. Here, a siRNA-based transcription factor profiling in human glioblastoma cells revealed that the expression of human TDO is suppressed by endogenous glucocorticoid signaling. Similarly, treatment of glioblastoma cells with the synthetic glucocorticoid dexamethasone led to a reduction of TDO expression and activity in vitro and in vivo. TDO inhibition was dependent on the immunophilin FKBP52, whose FK1 domain physically interacted with the glucocorticoid receptor as demonstrated by bimolecular fluorescence complementation and in situ proximity ligation assays. Accordingly, gene expression profile analyses revealed negative correlation of FKBP52 and TDO in glial and neural tumors and in normal brain. Knockdown of FKBP52 and treatment with the FK-binding immunosuppressant FK506 enhanced TDO expression and activity in glioblastoma cells. In summary, we identify a novel steroid-responsive FKBP52-dependent pathway suppressing the expression and activity of TDO, a central and rate-limiting enzyme in tryptophan metabolism, in human gliomas.
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http://dx.doi.org/10.1002/glia.22734DOI Listing
January 2015

A vaccine targeting mutant IDH1 induces antitumour immunity.

Nature 2014 Aug 25;512(7514):324-7. Epub 2014 Jun 25.

1] Department of Neurooncology, University Hospital Heidelberg and National Center for Tumor Diseases, 69120 Heidelberg, Germany [2] German Cancer Consortium (DKTK) Clinical Cooperation Unit Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany.

Monoallelic point mutations of isocitrate dehydrogenase type 1 (IDH1) are an early and defining event in the development of a subgroup of gliomas and other types of tumour. They almost uniformly occur in the critical arginine residue (Arg 132) in the catalytic pocket, resulting in a neomorphic enzymatic function, production of the oncometabolite 2-hydroxyglutarate (2-HG), genomic hypermethylation, genetic instability and malignant transformation. More than 70% of diffuse grade II and grade III gliomas carry the most frequent mutation, IDH1(R132H) (ref. 3). From an immunological perspective, IDH1(R132H) represents a potential target for immunotherapy as it is a tumour-specific potential neoantigen with high uniformity and penetrance expressed in all tumour cells. Here we demonstrate that IDH1(R132H) contains an immunogenic epitope suitable for mutation-specific vaccination. Peptides encompassing the mutated region are presented on major histocompatibility complexes (MHC) class II and induce mutation-specific CD4(+) T-helper-1 (TH1) responses. CD4(+) TH1 cells and antibodies spontaneously occurring in patients with IDH1(R132H)-mutated gliomas specifically recognize IDH1(R132H). Peptide vaccination of mice devoid of mouse MHC and transgenic for human MHC class I and II with IDH1(R132H) p123-142 results in an effective MHC class II-restricted mutation-specific antitumour immune response and control of pre-established syngeneic IDH1(R132H)-expressing tumours in a CD4(+) T-cell-dependent manner. As IDH1(R132H) is present in all tumour cells of these slow-growing gliomas, a mutation-specific anti-IDH1(R132H) vaccine may represent a viable novel therapeutic strategy for IDH1(R132H)-mutated tumours.
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http://dx.doi.org/10.1038/nature13387DOI Listing
August 2014

Constitutive IDO expression in human cancer is sustained by an autocrine signaling loop involving IL-6, STAT3 and the AHR.

Oncotarget 2014 Feb;5(4):1038-51

Department of Neurooncology, Neurology Clinic and National Center for Tumor Diseases University Hospital of Heidelberg, Heidelberg, Germany.

Indoleamine-2,3-dioxygenase (IDO) inhibitors have entered clinical trials based on their ability to restore anti-tumor immunity in preclinical studies. However, the mechanisms leading to constitutive expression of IDO in human tumors are largely unknown. Here we analyzed the pathways mediating constitutive IDO expression in human cancer. IDO-positive tumor cells and tissues showed basal phosphorylation and acetylation of STAT3 as evidenced by western blotting and immunoprecipitation. Inhibition of IL-6 or STAT3 using siRNA and/or pharmacological inhibitors reduced IDO mRNA and protein expression as well as kynurenine formation. In turn, IDO enzymatic activity activated the AHR as shown by the induction of AHR target genes. IDO-mediated AHR activation induced IL-6 expression, while inhibition or knockdown of the AHR reduced IL-6 expression. IDO activity thus sustains its own expression via an autocrine AHR-IL-6-STAT3 signaling loop. Inhibition of the AHR-IL-6-STAT3 signaling loop restored T-cell proliferation in mixed leukocyte reactions performed in the presence of IDO-expressing human cancer cells. Identification of the IDO-AHR-IL-6-STAT3 signaling loop maintaining IDO expression in human cancers reveals novel therapeutic targets for the inhibition of this core pathway promoting immunosuppression of human cancers. The relevance of the IDO-AHR-IL-6-STAT3 transcriptional circuit is underscored by the finding that high expression of its members IDO, STAT3 and the AHR target gene CYP1B1 is associated with reduced relapse-free survival in lung cancer patients.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4011581PMC
http://dx.doi.org/10.18632/oncotarget.1637DOI Listing
February 2014

Intraperitoneal prophylaxis with CpG oligodeoxynucleotides protects neutropenic mice against intracerebral Escherichia coli K1 infection.

J Neuroinflammation 2014 Jan 23;11:14. Epub 2014 Jan 23.

Institute of Neuropathology, University Medical Center Göttingen, Göttingen, Germany.

Background: Prophylaxis with unmethylated cytosine phosphate guanidine (CpG) oligodeoxynucleotides (ODN) protects against several systemic experimental infections. Escherichia coli is a major cause of Gram-negative neonatal bacterial meningitis and also causes meningitis and meningoencephalitis in older and immunocompromised patients.

Methods: Wild-type (wt) and Toll-like receptor 9 (TLR9)-deficient mice were rendered neutropenic by intraperitoneal administration of the anti-Ly-6G monoclonal antibody. Immunocompetent and neutropenic mice received intraperitoneal CpG ODN or vehicle 72 h prior to induction of E. coli K1 meningoencephalitis.

Results: Pre-treatment with CpG ODN significantly increased survival of neutropenic wt mice from 33% to 75% (P = 0.0003) but did not protect neutropenic TLR9-/- mice. The protective effect of CpG ODN was associated with an enhanced production of interleukin (IL)-12/IL-23p40 with sustained increased levels in serum and spleen at least for 17 days after conditioning compared to buffer-treated animals. CpG-treated neutropenic wt mice showed reduced bacterial concentrations and increased recruitment of Ly6ChighCCR2+ monocytes in brain and spleen 42 h after infection. The levels of macrophage inflammatory protein 1α (MIP-1α) and interferon gamma (IFN-γ) in spleen were higher 42 h after infection in CpG-treated compared to buffer-treated neutropenic animals. In immunocompetent mice, prophylaxis with CpG ODN did not significantly increase survival compared to the buffer group (60% vs. 45%, P = 0.2).

Conclusions: These findings suggest that systemic administration of CpG ODN may help to prevent bacterial CNS infections in immunocompromised individuals.
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http://dx.doi.org/10.1186/1742-2094-11-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3906862PMC
January 2014

Protein kinase Cβ as a therapeutic target stabilizing blood-brain barrier disruption in experimental autoimmune encephalomyelitis.

Proc Natl Acad Sci U S A 2013 Sep 19;110(36):14735-40. Epub 2013 Aug 19.

German Cancer Consortium (DKTK) Clinical Cooperation Units Neuroimmunology and Brain Tumor Immunology, Neurooncology, and Neuropathology, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany.

Disruption of the blood-brain barrier (BBB) is a hallmark of acute inflammatory lesions in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis. This disruption may precede and facilitate the infiltration of encephalitogenic T cells. The signaling events that lead to this BBB disruption are incompletely understood but appear to involve dysregulation of tight-junction proteins such as claudins. Pharmacological interventions aiming at stabilizing the BBB in MS might have therapeutic potential. Here, we show that the orally available small molecule LY-317615, a synthetic bisindolylmaleimide and inhibitor of protein kinase Cβ, which is clinically under investigation for the treatment of cancer, suppresses the transmigration of activated T cells through an inflamed endothelial cell barrier, where it leads to the induction of the tight-junction molecules zona occludens-1, claudin 3, and claudin 5 and other pathways critically involved in transendothelial leukocyte migration. Treatment of mice with ongoing experimental autoimmune encephalomyelitis with LY-317615 ameliorates inflammation, demyelination, axonal damage, and clinical symptoms. Although LY-317615 dose-dependently suppresses T-cell proliferation and cytokine production independent of antigen specificity, its therapeutic effect is abrogated in a mouse model requiring pertussis toxin. This abrogation indicates that the anti-inflammatory and clinical efficacy is mainly mediated by stabilization of the BBB, thus suppressing the transmigration of encephalitogenic T cells. Collectively, our data suggest the involvement of endothelial protein kinase Cβ in stabilizing the BBB in autoimmune neuroinflammation and imply a therapeutic potential of BBB-targeting agents such as LY-317615 as therapeutic approaches for MS.
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http://dx.doi.org/10.1073/pnas.1302569110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3767524PMC
September 2013

Promotion of glioblastoma cell motility by enhancer of zeste homolog 2 (EZH2) is mediated by AXL receptor kinase.

PLoS One 2012 15;7(10):e47663. Epub 2012 Oct 15.

Department of Neurooncology, University Hospital Heidelberg, Heidelberg, Germany.

Enhancer of zeste homolog 2 (EZH2) is the catalytic subunit of the Polycomb-repressive complex 2 (PRC2) that epigenetically silences gene transcription through histone H3 lysine trimethylation (H3K27me3). EZH2 has been implicated in stem cell maintenance and is overexpressed in hematological and solid malignancie`s including malignant glioma. EZH2 is thought to promote tumor progression by silencing tumor suppressor genes. Hence pharmacological disruption of the PRC2 is an attractive therapeutic strategy for cancer treatment. Here we show that EZH2 is expressed in human glioma and correlates with malignancy. Silencing of EZH2 reduced glioma cell proliferation and invasiveness. While we did not observe induction of cell cycle-associated tumor suppressor genes by silencing or pharmacological inhibition of EZH2, microarray analyses demonstrated a strong transcriptional reduction of the AXL receptor kinase. Neither histone nor DNA methylation appeared to be involved in the positive regulation of AXL by EZH2. Silencing AXL mimicked the antiinvasive effects of EZH2 knockdown. Finally, AXL expression is found in human gliomas with high EZH2 expression. Collectively these data suggest that EZH2 drives glioma invasiveness via transcriptional control of AXL independent of histone or DNA methylation.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0047663PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3471855PMC
April 2013