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  • 11
  • 12
    Abstract: BACKGROUND: Colorectal cancers (CRCs) that lack DNA mismatch repair function exhibit the microsatellite unstable (MSI) phenotype and are characterized by the accumulation of frameshift mutations at short repetitive DNA sequences (microsatellites). These tumors recurrently show inactivating frameshift mutations in the tumor suppressor Transforming Growth Factor Beta Receptor Type 2 (TGFBR2) thereby abrogating downstream signaling. How altered TGFBR2 signaling affects exosome-mediated communication between MSI tumor cells and their environment has not been resolved. Here, we report on molecular alterations of exosomes shed by MSI cells and the biological response evoked in recipient cells. METHODS: Exosomes were isolated and characterized by electron microscopy, nanoparticle tracking, and western blot analysis. TGFBR2-dependent effects on the cargo and functions of exosomes were studied in a MSI CRC model cell line enabling reconstituted and inducible TGFBR2 expression and signaling. Microsatellite frameshift mutations in exosomal and cellular DNA were examined by PCR-based DNA fragment analysis and exosomal protein profiles were identified by mass spectrometry. Uptake of fluorescent-labeled exosomes by hepatoma recipient cells was monitored by confocal microscopy. TGFBR2-dependent exosomal effects on secreted cytokine levels of recipient cells were analyzed by Luminex technology and ELISA. RESULTS: Frameshift mutation patterns in microsatellite stretches of TGFBR2 and other MSI target genes were found to be reflected in the cargo of MSI CRC-derived exosomes. At the proteome level, reconstituted TGFBR2 expression and signaling uncovered two protein subsets exclusively occurring in exosomes derived from TGFBR2-deficient (14 proteins) or TGFBR2-proficient (five proteins) MSI donor cells. Uptake of these exosomes by recipient cells caused increased secretion (2-6 fold) of specific cytokines (Interleukin-4, Stem Cell Factor, Platelet-derived Growth Factor-B), depending on the TGFBR2 expression status of the tumor cell. CONCLUSION: Our results indicate that the coding MSI phenotype of DNA mismatch repair-deficient CRC cells is maintained in their exosomal DNA. Moreover, we uncovered that a recurrent MSI tumor driver mutation like TGFBR2 can reprogram the protein content of MSI cell-derived exosomes and in turn modulate the cytokine secretion profile of recipient cells. Apart from its diagnostic potential, these TGFBR2-dependent exosomal molecular and proteomic signatures might help to understand the signaling routes used by MSI tumors. Fricke et al. uncovered coding microsatellite instability-associated mutations of colorectal tumor driver genes like TGFBR2 in MSI tumor cellderived exosomes. Depending on the TGFBR2 expression status of their donor cells, shed exosomes show distinct proteomic signatures and promote altered cytokine secretion profiles in recipient cells.
    Type of Publication: Journal article published
    PubMed ID: 28376875
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  • 13
    Abstract: Activin receptor type II (ACVR2) is a member of the transforming growth factor type II receptor (TGFBR2) family and controls cell growth and differentiation thereby acting as a tumor suppressor. ACVR2 inactivation is known to drive colorectal tumorigenesis. We used an ACVR2-deficient microsatellite unstable colon cancer cell line (HCT116) to set up a novel experimental design for comprehensive analysis of proteomic changes associated with such functional loss of a tumor suppressor. To this end we combined two existing technologies. First, the ACVR2 gene was reconstituted in an ACVR2-deficient colorectal cancer cell line by Recombinase Mediated Cassette Exchange (RMCE), resulting in the generation of an inducible expression system, which allows the regulation of ACVR2 gene expression in a doxycycline-dependent manner. Functional expression in the induced cells was explicitly proven. Second, we used the methionine analogue azidohomoalanine for metabolic labeling of newly synthesized proteins in our cell line model. Labeled proteins were tagged with biotin by a Click-it chemistry approach enabling specific extraction of labeled proteins by streptavidin-coated beads. Tryptic on-bead digestion of captured proteins and subsequent UPLC-coupled LTQ Orbitrap XL mass spectrometry identified 513 proteins, 25 of them being differentially expressed between ACVR2-deficient and -proficient cells. Among these, several candidates that have already been linked to colorectal cancer (CRC) or play a key role in cell growth or apoptosis control were identified thereby proving the utility of the presented experimental approach. In principle, this strategy can be adapted to analyze any gene of interest and its effect on the cellular de novo proteome.
    Type of Publication: Journal article published
    PubMed ID: 25225355
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  • 14
    Keywords: CANCER ; EXPRESSION ; INHIBITOR ; tumor ; carcinoma ; CELL ; Germany ; CLASSIFICATION ; DIAGNOSIS ; RISK ; PROTEIN ; SAMPLES ; PATIENT ; BIOLOGY ; ASSOCIATION ; FIELD ; ALPHA ; STAGE ; IDENTIFICATION ; IN-SITU ; immunohistochemistry ; genetics ; ABERRATIONS ; MASS-SPECTROMETRY ; ONCOGENE ; HUMAN-PAPILLOMAVIRUS ; SQUAMOUS-CELL CARCINOMA ; HEAD ; NECK ; RISK ASSESSMENT ; heredity ; BIOPSY ; protein expression ; PROTEOMICS ; PROTEOMIC ANALYSIS ; NECK-CANCER ; CELL CARCINOMA ; ONCOLOGY ; TUMORIGENESIS ; ARRAY ; HNSCC ; LYMPH-NODE METASTASIS ; development ; analysis ; PROFILES ; EVENTS ; protein biomarkers ; HISTOLOGY ; FRAGMENT ; SELDI-TOF-MS ; BIOPSIES ; CLINICAL-IMPLICATIONS ; aberration ; comparison ; acyl-CoA-binding protein ; CANCERIZATION ; field cancerization ; GENETICALLY ALTERED FIELDS ; HUMAN NEUTROPHIL PEPTIDE-1 ; TUMOR-DISTANT EPITHELIA
    Abstract: Development of head and necksquamous cell carcinoma (HNSCC) is a multistep process and in many cases involves a phenomenon coined 'field cancerization'. In order to identify changes in protein expression occurring at different stages of tumorigenesis and field cancerization, we analysed 113 HNSCCs and 73 healthy, 99 tumor-distant and 18 tumor-adjacent squamous mucosae by SELDI-TOF-MS on IMAC30 ProteinChip Arrays. Forty-eight protein peaks were differentially expressed between healthy mucosa and HNSCC. Calgizarrin (S100A11), the Cystein proteinase inhibitor Cystatin A, Acyl-CoA-binding protein, Stratifin (14-3-3 sigma), Histone H4, alpha- and beta-Hemoglobin, a C-terminal fragment of beta-hemoglobin and the alpha-defensins 1-3 were identified by mass spectrometry. The alpha-defensins showed various alterations in expression as validated by immunohistochemistry (IHC). Supervised prediction analysis revealed excellent classification of healthy mucosa (94.5% correctly classified) and tumor samples (92.9% correctly classified). Application of this classifier to the tumor-adjacent and tumor-distant mucosa samples disclosed dramatic changes: only 59.6% of the tumor-distant biopsies were classified as normal, 27.3% were predicted as aberrant or HNSCC. Strikingly, 72% of the tumor-adjacent mucosae were predicted as aberrant. These data provide evidence for the existence of genetically altered fields with inconspicuous histology. Comparison of the protein profiles in the tumor-distant-samples with clinical outcome of 32 patients revealed a significant association between aberrant profiles with tumor relapse events (P = 0.018; Fisher's exact test, two-tailed). We conclude that proteomic pro. ling in conjunction with protein identification greatly outperforms histopathological diagnosis and may have significant predictive power for clinical outcome and personalized risk assessment
    Type of Publication: Journal article published
    PubMed ID: 16819514
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  • 15
    Keywords: brain ; RECEPTOR ; CELLS ; Germany ; NETWORKS ; SYSTEM ; TOOL ; DISTINCT ; PROTEIN ; PROTEINS ; TRANSDUCTION ; COMPLEX ; MESSENGER-RNA ; RAT ; signal transduction ; MEMBRANE ; SIGNAL-TRANSDUCTION ; mass spectrometry ; MASS-SPECTROMETRY ; CHROMATOGRAPHY ; PROTEOMIC ANALYSIS ; glutathione-S-transferase ; BINDING PROTEIN ; signaling ; molecular ; NEURONS ; analysis ; cilia ; ENGLAND ; XENOBIOTIC-METABOLIZING ENZYMES ; affinity chromatography ; calcium-calmodulin ; CHEMOSENSORY CILIA ; NUCLEOTIDE-GATED CHANNEL ; olfaction ; olfactory receptor neurons ; PHOSPHOLIPID-BINDING ; SENSORY NEURONS
    Abstract: The olfactory neuroepithelium represents a unique interface between the brain and the external environment. Olfactory function comprises a distinct set of molecular tasks: sensory signal transduction, cytoprotection and adult neurogenesis. A multitude of biochemical studies has revealed the central role of Ca2+ signaling in the function of olfactory receptor neurons (ORNs). We set out to establish Ca2+-dependent signaling networks in ORN cilia by proteomic analysis. We subjected a ciliary membrane preparation to Ca2+/calmodulin-affinity chromatography using mild detergent conditions in order to maintain functional protein complexes involved in olfactory Ca2+ signaling. Thus, calmodulin serves as a valuable tool to gain access to novel Ca2+-regulated protein complexes. Tandem mass spectrometry (nanoscale liquid-chromatography-electrospray injection) identified 123 distinct proteins. Ninety-seven proteins (79%) could be assigned to specific olfactory functions, including 32 to sensory signal transduction and 40 to cytoprotection. We point out novel perspectives for research on the Ca2+-signaling networks in the olfactory system of the rat. (C) 2007 IBRO. Published by Elsevier Ltd. All rights reserved
    Type of Publication: Journal article published
    PubMed ID: 18155848
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  • 16
    Keywords: MICE ; COMPLEX ; SUPERFAMILY ; TNF ; KAPPA-B ACTIVATION ; RHEUMATOID-ARTHRITIS ; STRUCTURAL BASIS ; CHAINS ; CHRONIC PROLIFERATIVE DERMATITIS ; K11-LINKED POLYUBIQUITINATION ; MEDIATED REGULATION ; NEMO
    Abstract: Members of the tumour necrosis factor (TNF) receptor superfamily have important functions in immunity and inflammation. Recently linear ubiquitin chains assembled by a complex containing HOIL-1 and HOIP (also known as RBCK1 and RNF31, respectively) were implicated in TNF signalling, yet their relevance in vivo remained uncertain. Here we identify SHARPIN as a third component of the linear ubiquitin chain assembly complex, recruited to the CD40 and TNF receptor signalling complexes together with its other constituents, HOIL-1 and HOIP. Mass spectrometry of TNF signalling complexes revealed RIP1 (also known as RIPK1) and NEMO (also known as IKK gamma or IKBKG) to be linearly ubiquitinated. Mutation of the Sharpin gene (Sharpin(cpdm/cpdm)) causes chronic proliferative dermatitis (cpdm) characterized by inflammatory skin lesions and defective lymphoid organogenesis. Gene induction by TNF, CD40 ligand and interleukin-1 beta was attenuated in cpdm-derived cells which were rendered sensitive to TNF-induced death. Importantly, Tnf gene deficiency prevented skin lesions in cpdm mice. We conclude that by enabling linear ubiquitination in the TNF receptor signalling complex, SHARPIN interferes with TNF-induced cell death and, thereby, prevents inflammation. Our results provide evidence for the relevance of linear ubiquitination in vivo in preventing inflammation and regulating immune signalling
    Type of Publication: Journal article published
    PubMed ID: 21455173
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  • 17
    Keywords: RECEPTOR ; APOPTOSIS ; EXPRESSION ; IN-VITRO ; THERAPY ; GENE ; LINES ; RECOGNITION ; PROSTATE-CANCER ; GLIOMA ; GLIOMA-CELLS ; T-CELL-ACTIVATION ; TGF-BETA ; TUMOR-CELL ; cancer research ; GLIOBLASTOMA ; B7-H3 ; FURIN-LIKE PROTEASES
    Abstract: PURPOSE: Recent work points out a role of B7H3, a member of the B7-family of costimulatory proteins, in conveying immunosuppression and enforced invasiveness in a variety of tumor entities. Glioblastoma is armed with effective immunosuppressive properties resulting in an impaired recognition and ineffective attack of tumor cells by the immune system. In addition, extensive and diffuse invasion of tumor cells into the surrounding brain tissue limits the efficacy of local therapies. Here, 4IgB7H3 is assessed as diagnostic and therapeutic target for glioblastoma. EXPERIMENTAL DESIGN: To characterize B7H3 in glioblastoma, we conduct analyses not only in glioma cell lines and glioma-initiating cells but also in human glioma tissue specimens. RESULTS: B7H3 expression by tumor and endothelial cells correlates with the grade of malignancy in gliomas and with poor survival. Both soluble 4IgB7H3 in the supernatant of glioma cells and cell-bound 4IgB7H3 are functional and suppress natural killer cell-mediated tumor cell lysis. Gene silencing showed that membrane and soluble 4IgB7H3 convey a proinvasive phenotype in glioma cells and glioma-initiating cells in vitro. These proinvasive and immunosuppressive properties were confirmed in vivo by xenografted 4IgB7H3 gene silenced glioma-initiating cells, which invaded significantly less into the surrounding brain tissue in an orthotopic model and by subcutaneously injected LN-229 cells, which were more susceptible to natural killer cell-mediated cytotoxicity than unsilenced control cells. CONCLUSIONS: Because of its immunosuppressive and proinvasive function, 4IgB7H3 may serve as a therapeutic target in the treatment of glioblastoma.
    Type of Publication: Journal article published
    PubMed ID: 22080438
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  • 18
    Keywords: CELL ; PROTEINS ; EVOLUTION ; WALL ; VENOM ; BIOLOGICAL ROLES ; CNIDARIAN NEMATOCYST ; DISCHARGE ; MINI-COLLAGENS ; MINICOLLAGENS ; RICH PROTEIN
    Abstract: Stinging cells or nematocytes of jellyfish and other cnidarians represent one of the most poisonous and sophisticated cellular inventions in animal evolution. This ancient cell type is unique in containing a giant secretory vesicle derived from the Golgi apparatus. The organelle structure within the vesicle comprises an elastically stretched capsule (nematocyst) to which a long tubule is attached. During exocytosis, the barbed part of the tubule is accelerated with 〉5 million g in 〈700 ns, enabling a harpoon-like discharge (Nuchter, T., Benoit, M., Engel, U., Ozbek, S., and Holstein, T. W. (2006) Curr. Biol. 16, R316-R318). Hitherto, the molecular components responsible for the organelle's biomechanical properties were largely unknown. Here, we describe the proteome of nematocysts from the freshwater polyp Hydra magnipapillata. Our analysis revealed an unexpectedly complex secretome of 410 proteins with venomous and lytic but also adhesive or fibrous properties. In particular, the insoluble fraction of the nematocyst represents a functional extracellular matrix structure of collagenous and elastic nature. This finding suggests an evolutionary scenario in which exocytic vesicles harboring a venomous secretome assembled a sophisticated predatory structure from extracellular matrix motif proteins.
    Type of Publication: Journal article published
    PubMed ID: 22291027
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  • 19
    Keywords: MECHANISM ; CELL-DEATH ; MUTATIONS ; CRYSTAL-STRUCTURE ; CD95-induced apoptosis ; IMMUNE-SYSTEM ; ABSOLUTE QUANTIFICATION ; CASPASE-8 GENE ; PROCASPASE-8 ACTIVATION ; EXTRINSIC APOPTOSIS
    Abstract: The CD95 (Fas/APO-1) death-inducing signaling complex (DISC) is essential for the initiation of CD95-mediated apoptotic and nonapoptotic responses. The CD95 DISC comprises CD95, FADD, procaspase-8, procaspase-10, and c-FLIP proteins. Procaspase-8 and procaspase-10 are activated at the DISC, leading to the formation of active caspases and apoptosis initiation. In this study we analyzed the stoichiometry of the CD95 DISC. Using quantitative western blots, mass spectrometry, and mathematical modeling, we reveal that the amount of DED proteins procaspase-8/procaspase-10 and c-FLIP at the DISC exceeds that of FADD by several-fold. Furthermore, our findings imply that procaspase-8, procaspase-10, and c-FLIP could form DED chains at the DISC, enabling the formation of dimers and efficient activation of caspase-8. Taken together, our findings provide an enhanced understanding of caspase-8 activation and initiation of apoptosis at the DISC.
    Type of Publication: Journal article published
    PubMed ID: 22683265
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  • 20
    Keywords: EXPRESSION ; GENE ; MEMBER ; COLON-CANCER ; microsatellite instability ; MUTATIONS ; CYTOKINE ; SMAD PROTEINS ; TGF-BETA SUPERFAMILY ; MIC-1
    Abstract: Although inactivating frameshift mutations in the Transforming growth factor beta receptor type 2 (TGFBR2) gene are considered as drivers of microsatellite unstable (MSI) colorectal tumorigenesis, consequential alterations of the downstream target proteome are not resolved completely. Applying a click-it chemistry protein labeling approach combined with mass spectrometry in a MSI colorectal cancer model cell line, we identified 21 de novo synthesized proteins differentially expressed upon reconstituted TGFBR2 expression. One candidate gene, the TGF-ss family member Growth differentiation factor-15 (GDF-15), exhibited TGFBR2-dependent transcriptional upregulation causing increased intracellular and extracellular protein levels. As a new TGFBR2 target gene it may provide a link between the TGF-ss branch and the BMP/GDF branch of SMAD-mediated signaling.
    Type of Publication: Journal article published
    PubMed ID: 26114631
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