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  • 1
    Abstract: Chronic lymphocytic leukemia is a malignancy of mature B cells that strongly depend on microenvironmental factors and their deprivation has been identified as promising treatment approach for this incurable disease. Cytokine array screening of 247 chronic lymphocytic leukemia serum samples revealed elevated levels of TNF receptor-1 which were associated with poor clinical outcome. We detected a microenvironment-induced expression of TNF receptor-1 in chronic lymphocytic leukemia cells in vitro and aberrantly high expression of this receptor in proliferation centers of patients' lymph nodes. Stimulation of TNF receptor-1 with TNF-alpha enhanced NFkappaB activity and viability of chronic lymphocytic leukemia cells which was inhibited by wogonin. Therapeutic effects of wogonin were analyzed in mice after adoptive transfer of Em-TCL1 leukemic cells. Wogonin treatment prevented leukemia development when given early after transplantation. Treatment of full-blown leukemia resulted in loss of TNF receptor-1 on chronic lymphocytic leukemia cells and their mobilization to blood. Targeting TNF receptor-1 signaling is therefore proposed for treatment of chronic lymphocytic leukemia.
    Type of Publication: Journal article epub ahead of print
    PubMed ID: 29326123
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  • 2
    Abstract: To understand the function of the individual oncogenes of HPV16 in modulating the cellular response to apoptogenic signals, we used human keratinocytes immortalized with either E6, E7 or E6/E7 oncoproteins as model system. Applying CD95 antibodies or recombinant CD95 ligand, only the E7-immortalized cells underwent extensive apoptosis. In contrast, E6- and E6/E7-expressing keratinocytes were resistant. Dominance of E6 correlated with significant down-regulation of p53, c-Myc, p21 and Bcl-2. CD95 was found to be reduced in resistant HPV-positive cells, while there were no quantitative differences in expression levels of FADD, FLICE/caspase-8 or caspase-3. Notably, in contrast to primary human keratinocytes, all immortalized cells showed a general reduction of c-FLIP, an inhibitory protein which normally prevents unscheduled CD95-induced apoptosis. E6- and E6/E7-positive keratinocytes, however, can be sensitized to CD95 apoptosis by blocking proteasome-mediated proteolysis. CD95-resistant HPV-positive cells underwent apoptosis within 3-5 h upon co-incubation with MG132 and agonistic antibodies or CD95 ligand, which was preceded by a strong re-expression of p53 and c-Myc, but not of other half-life controlled proteins such as Bax or IkappaBalpha. Blockage of proteasomal activity alone did not result in apoptosis, although the same set of pro-apoptotic proteins was up-regulated. Performing similar experiments with cervical carcinoma cells expressing mutated p53 (C33a) or with p53-'null' lung carcinoma cells (H1299), no CD95 cell killing occurred even though c-Myc was strongly induced. These data indicate that the reduced bioavailability of p53 is a key-regulatory event in perturbation of CD95 signaling in HPV16 immortalized keratinocytes.
    Type of Publication: Journal article published
    PubMed ID: 11803460
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  • 3
    Keywords: RECEPTOR ; APOPTOSIS ; PATHWAYS ; DEATH ; NF-KAPPA-B ; DENDRITIC CELLS ; signal transduction ; LYMPHOCYTES ; FAS-LIGAND ; CD95 ; T-CELL ACTIVATION ; COSTIMULATION ; IMMUNE-SYSTEM ; INTERNALIZATION ; co-stimulation
    Abstract: CD95 is a dual-function receptor that exerts pro- or antiapoptotic effects depending on the cellular context, the state of activation, the signal threshold and the mode of ligation. In this study, we report that CD95 engagement modulates TCR/CD3-driven signaling pathways in resting T lymphocytes in a dose-dependent manner. While high doses of immobilized CD95 agonists silence T cells, lower concentrations augment activation and proliferation. We analyzed the co-stimulatory capacity of CD95 in detail in resting human CD4(+) T cells, and demonstrate that low-dose ligand-induced co-internalization of CD95 and TCR/CD3 complexes enables non-apoptotic caspase activation, the prolonged activation of MAP kinases, the upregulation of antiapoptotic proteins associated with apoptosis resistance, and the activation of transcription factors and cell-cycle regulators for the induction of proliferation and cytokine production. We propose that the levels of CD95L on antigen-presenting cells (APCs), neighboring T cells or epithelial cells regulate inhibitory or co-stimulatory CD95 signaling, which in turn is crucial for fine-tuning of primary T-cell activation.
    Type of Publication: Journal article published
    PubMed ID: 21052094
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  • 4
    Keywords: CELLS ; IN-VITRO ; proliferation ; tumor ; TUMOR-CELLS ; BLOOD ; Germany ; VITRO ; GENE ; INDUCTION ; SKIN ; BETA ; FLOW-CYTOMETRY ; LEUKEMIA-CELLS ; FOXP3 EXPRESSION ; CD25 EXPRESSION ; CD4(+)CD25(-) T-CELLS ; CUTANEOUS-LYMPHOMAS ; LEUKEMIA/LYMPHOMA CELLS ; PERIPHERAL-BLOOD INVOLVEMENT
    Abstract: Cutaneous T-cell lymphoma (CTCL) has been suggested by in vitro experiments to represent a malignant CD4+ T-cell proliferation with a regulatory T-cell (Treg) phenotype (CD4+CD25+FOXP3+). We investigated percentages of FOXP3+ and CD25+ cells in the blood of 15 Sezary, 14 mycosis fungoides (MF), and 10 psoriasis (Pso) patients and 20 normal healthy donors (NHDs). We found similar numbers of FOXP3+ cells in MF (10.4% of blood CD4+ cells) and Pso (11.1%) patients and NHDs (9.8%). In 8 of 15 (53%) Sezary patients, significantly reduced percentages of FOXP3+ cells were seen in blood (2.9%) and skin (10.4%). Interestingly, 6 of 15 (40%) Sezary patients showed significantly increased percentages of FOXP3+ cells (39.7% (blood), 20.3% (skin)); however, these cells did not express CD25. In these latter patients, clone-specific TCR-Vbeta-chain antibodies were used to demonstrate that these FOXP3+CD25- cells were monoclonal CTCL tumor cells. FOXP3+CD25- CTCL tumor cells showed a highly demethylated status of the foxp3 gene locus similar to Treg cells, and they were functionally able to suppress IL-2 mRNA induction in TCR-stimulated conventional T cells. Thus, FOXP3+CD25- CTCL tumor cells with functional features of Treg cells define a subgroup of Sezary patients who might carry a different prognosis and might require differential treatment.
    Type of Publication: Journal article published
    PubMed ID: 19626037
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  • 5
    Keywords: RECEPTOR ; proliferation ; ACTIVATION ; DENDRITIC CELLS ; TOLERANCE ; CYTOKINE ; REGULATORY T-CELLS ; SKIN-LESIONS ; TNF FAMILY-MEMBER ; TRANCE
    Abstract: Recently, it was discovered that the receptor activator of nuclear factor kappa B (RANK)/RANK ligand (RANKL) is part of an important signal transduction pathway for tissue homoeostasis. Therefore, we were interested in investigating RANKL expression in the epidermis of skin lesions from patients with different subtypes of cutaneous lupus erythematosus (CLE) and psoriasis as well as normal healthy donors. Using the tissue microarray technique, skin biopsy specimens were evaluated by immunohistochemistry. RANKL showed a significantly increased expression in the epidermis of skin biopsy specimens from patients with psoriasis (median: 4, range: 0-5) compared to patients with CLE (median: 0, range: 0-4) (P 〈 0.001). No significant differences in epidermal RANKL expression between the CLE subtypes were detected. These data show a different expression of RANKL in the epidermis of skin lesions from patients with CLE compared to those with psoriasis suggesting that RANKL might play an important role in the pathogenesis of the disease.
    Type of Publication: Journal article published
    PubMed ID: 21692859
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  • 6
    Keywords: DISEASE ; FREQUENCY ; PATHOGENESIS ; MULTIPLE-SCLEROSIS ; LUPUS-ERYTHEMATOSUS ; LOCALIZED SCLERODERMA ; DEFECTIVE SUPPRESSOR FUNCTION ; BOSENTAN ; ENDOTHELIN-RECEPTOR ANTAGONIST ; PULMONARY ARTERIAL-HYPERTENSION
    Abstract: OBJECTIVE: To determine the frequency and suppressive capacity of regulatory T cells (T(reg)) and their association with clinical parameters in patients with systemic scleroderma (SSc). METHODS: Peripheral blood from 25 patients with SSc, 15 patients with localised scleroderma (LS) and 29 healthy controls (HC) was studied. Analysis of CD4(+) forkhead box P3 (Foxp3)(+) and CD4(+)CD25(++)Foxp3(+) Treg subpopulations was carried out by flow cytometry and cell proliferation was quantified by (3)H-thymidine incorporation. Quantitative analysis of T(reg) was further performed in skin biopsies from 17 patients with SSc and 21 patients with LS using anti-CD4 and anti-Foxp3 monoclonal antibodies for immunohistochemistry. RESULTS: The frequency of CD4(+)Foxp3(+) and CD4(+)CD25(++)Foxp3(+) Treg in peripheral blood from patients with SSc was not significantly different from that of patients with LS or HC. The suppressive capacity of CD4(+)CD25(++) Treg in SSc was also found to be similar to that of HC. Phenotypic and functional data revealed no significant difference between the limited or diffuse form of SSc. Moreover, therapy with bosentan showed no significant effect on the frequency of T(reg) during the course of the disease. However, the frequency of T(reg) in skin lesions from patients with SSc or LS, determined as the percentage of CD4(+) cells expressing Foxp3 in the inflammatory infiltrate, was significantly reduced compared with other inflammatory skin diseases. CONCLUSION: These results indicate that although the authors found no defect in the frequency or function of peripheral T(reg) subpopulations, the reduction of CD4(+)Foxp3(+) T(reg) in the skin of patients with SSc may be important in the pathogenesis of the disease.
    Type of Publication: Journal article published
    PubMed ID: 21097800
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  • 7
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    Keywords: APOPTOSIS ; PATHWAYS ; NF-KAPPA-B ; STIMULATION ; CELL-DEATH ; INDUCED APOPTOSIS ; DISC ; CD95 ; CASPASE-8 ACTIVATION ; CD95-induced apoptosis ; CASPASE-8 ; MEDIATED APOPTOSIS ; C-FLIP ; FLICE-INHIBITORY PROTEINS ; RECEPTOR SIGNALS ; LONG FORM ; PROCASPASE-8 ACTIVATION
    Abstract: CD95 (APO-1/Fas) is a member of the death receptor (DR) family. Stimulation of CD95 leads to induction of apoptotic and non-apoptotic signaling pathways. The formation of the CD95 death-inducing signaling complex (DISC) is the initial step of CD95 signaling. Activation of procaspase-8 at the DISC leads to the induction of DR-mediated apoptosis. The activation of procaspase-8 is blocked by cellular FLICE-inhibitory proteins (c-FLIP). This review is focused on the role in the CD95-mediated signaling of the death effector domain-containing proteins procaspase-8 and c-FLIP. We discuss how dynamic cross-talk between procaspase-8 and c-FLIP at the DISC regulates life/death decisions at CD95.
    Type of Publication: Journal article published
    PubMed ID: 22075988
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  • 8
    Keywords: RECEPTOR ; APOPTOSIS ; CANCER ; EXPRESSION ; IN-VITRO ; TUMOR-CELLS ; carcinoma ; Germany ; PATHWAY ; THERAPY ; DEATH ; GENE ; GENE-EXPRESSION ; TUMORS ; LINES ; NF-KAPPA-B ; LIGAND ; breast cancer ; BREAST-CANCER ; TARGET ; p53 ; MEDIATED APOPTOSIS ; ENDOPLASMIC-RETICULUM STRESS ; T-cell leukemia
    Abstract: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent that kills various tumor cells without damaging normal tissues. However, many cancers remain resistant to TRAIL. To overcome TRAIL resistance, combination therapies using sensitizers of the TRAIL pathway would be an efficacious approach. To investigate potential sensitizers of TRAIL-induced apoptosis, we used TRAIL-resistant human T cell leukemia virus type 1 (HTLV-1)-associated adult T cell leukemia/lymphoma (ATL) cells as a model system. So far, HTLV-1-associated ATL is incurable by presently known therapies. Here, we show that wogonin and the structurally related natural flavones apigenin and chrysin break TRAIL resistance in HTLV-1-associated ATL by transcriptional down-regulation of c-FLIP, a key inhibitor of death receptor signaling, and by up-regulation of TRAIL receptor 2 (TRAIL-R2). This effect is mediated through transcriptional inhibition of the p53 antagonist murine double minute 2 (Mdm2), leading to an increase in p53 levels and, consequently, to up-regulation of the p53 target gene TRAIL-R2. We also show that these flavones can sensitize to TNFalpha- and CD95-mediated cell death. Furthermore, we show that wogonin, apigenin, and chrysin also enhance TRAIL-mediated apoptosis in other human cancer cell lines including breast cancer cell line MDA-MB-231, colon cancer cell line HT-29, hepatocellular carcinoma cell line HepG2, melanoma cell line SK-MEL-37, and pancreatic carcinoma cell line Capan-1 by the same mechanism. Thus, our study suggests the potential use of these flavones as an adjuvant for TRAIL-mediated anticancer therapy.
    Type of Publication: Journal article published
    PubMed ID: 22086925
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  • 9
    Keywords: RECEPTOR ; APOPTOSIS ; GROWTH-FACTOR ; DISEASE ; LINES ; REED-STERNBERG CELLS ; PATHOGENESIS ; B-CELLS ; Stat3 ; INTERLEUKIN-13
    Abstract: Hodgkin/Reed-Sternberg lymphoma (HL) is a clonal B-cell-related malignancy. Although many patients with HL can be cured by the current regimen of high-dose multi-agent chemotherapy, the treatment causes high risks of later pathologies including secondary malignancies. This fact highlights the demand to develop rational treatment for HL. Survival and growth of HL cells are largely dependent on their microenvironment. In this study, using the HL cell lines L1236 and KM-H2 as model systems, we investigated the role of IL-4/IL-13 signaling in regulation of drug sensitivity and resistance in HL. We show that specific blocking of IL-4 and IL-13-mediated STAT6 activation by either an IL-4-binding fusion protein APG598 or an IL-4R antagonist APG201 (R121D/Y124D) renders HL cells more prone to apoptotic killing by chemotherapeutic drugs such as Mitomycin C, 5-Fluorouracil, Etopside, Doxorubicin and Paclitaxel. This effect is due to inhibition of STAT6-mediated elevation of expression of the anti-apoptotic Bcl-2 family protein Bcl-xL. Employing ChIP analysis in combination with APG201 or STAT6-specific siRNA we identified a defined STAT6-binding site in the Bcl-xL promoter region from -1967 to -1957 of the transcription start site. Our data demonstrate that the IL-4/IL-13-STAT6-Bcl-xL axis may be an important target for HL treatment. This study also suggests that combination of classical chemotherapeutic drugs with the IL-4/IL-13 antagonists may enhance efficacy and reduce risks of toxicity from high dose of drugs in HL treatment.
    Type of Publication: Journal article published
    PubMed ID: 23553437
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  • 10
    Keywords: NF-KAPPA-B ; SYSTEMIC-LUPUS-ERYTHEMATOSUS ; EXPERIMENTAL AUTOIMMUNE ENCEPHALOMYELITIS ; KINASE-C-THETA ; OXYGEN SPECIES PRODUCTION ; MANGANESE SUPEROXIDE-DISMUTASE ; ADP-DEPENDENT GLUCOKINASE ; COMPLEX-I DEFICIENCY ; ALVEOLAR EPITHELIAL-CELLS ; HYDROGEN-PEROXIDE UPTAKE
    Abstract: Early scientific reports limited the cell biological role of reactive oxygen species (ROS) to the cause of pathological damage. However, extensive research performed over the last decade led to a wide recognition of intracellular oxidative/redox signaling as a crucial mechanism of homeostatic regulation. Amongst different cellular processes known to be influenced by redox signaling, T-cell activation is one of the most established. Numerous studies reported an indispensible role for ROS as modulators of T-cell receptor-induced transcription. Nevertheless, mechanistic details regarding signaling pathways triggered by ROS are far from being delineated. The nature and interplay between enzymatic sources involved in the generation of "oxidative signals" are also a matter of ongoing research. In particular, active participation of the mitochondrial respiratory chain as ROS producer constitutes an intriguing issue with various implications for bioenergetics of activated T cells as well as for T-cell-mediated pathologies. The aim of the current review is to address these interesting concepts.
    Type of Publication: Journal article published
    PubMed ID: 23749029
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