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T Brunner

Publications and source records attributed to T Brunner.

At least 37 records · Page 2Linked to original sources
PubMed1999

Transforming growth factor beta1 inhibits Fas ligand expression and subsequent activation-induced cell death in T cells via downregulation of c-Myc.

Activation-induced cell death (AICD) is a process that regulates the size and the duration of the primary immune T cell response. In this report, we investigated the mechanisms involved in the regulation of AICD by transforming growth factor beta1 (TGF-beta1). We found that TGF-beta1 decreased apoptosis of human T cells or T cell hybridomas after activation by anti-CD3. This decrease was associated with inhibition of Fas (Apo-1/CD95) ligand (FasL) expression, whereas Fas signaling was not affected by TGF-beta1. In parallel, TGF-beta1 inhibited c-Myc expression in T cell hybridomas, and ectopic expression of a chimeric molecule composed of c-Myc and the steroid binding domain of the estrogen receptor (Myc-ER) blocked both the inhibition of FasL and the decrease of AICD induced by TGF-beta1, providing that 4-hydroxytamoxifen was present. These results identify one mechanism by which TGF-beta1 blocks AICD to allow the clonal expansion of effector T cells and the generation of memory T cells during immune responses.

Animals↗
PubMed1999

[Multiplanar spiral CT in the diagnosis of pancreatic tumors].

PURPOSE: Investigation of the capabilities of MSCT and its value for the staging of pancreatic carcinomas. METHODS: 50 Patients with suspected pancreatic carcinoma were examined with a biphasic multislice-spiral-CT protocol: slice collimation 4 x 1 mm, Pitch 3.5-4 mm. After administration of 120 ml contrast medium and 50 ml NaCl with a flow rate of 3.0 ml/s the examination was started with a delay of 40 s (pancreatic phase) and 80 s (portal venous phase). RESULTS: Multislice spiral CT allows the examination of the whole upper abdomen with nearly isotropic data sets. This is the premise for the optimal assessment of the tumor extent in all planes, excellent demarcation of the tumor against the adjacent vessels and organs and the demarcation of small peripancreatic lymph nodes. CONCLUSIONS: Multislice spiral CT and the use of interactive multiplanar reconstructions improve the staging of pancreatic cancer.

Administration, Oral↗
PubMed1999

Characterization of Apt- cell lines exhibiting cross-resistance to glucocorticoid- and Fas-mediated apoptosis.

Apoptosis induction by staurosporine, ceramide, and Fas stimulation was investigated in the mouse thymoma cell line W7.2 and a panel of dexamethasone (dex)-resistant W7.2 mutant cell lines, Apt3.8, Apt4.8 and Apt5.8, and a Bcl-2 transfected W7.2 cell line (Wbcl2). While W7. 2 cells were found to be sensitive to these apoptosis inducers, the Apt- mutants and Wbcl2 cells were shown to be resistant to some or all of the treatments. Specifically, all three Apt- mutants and Wbcl2 cells were found to be resistant to ceramide and Fas-mediated apoptosis, whereas, Apt4.8 and Apt5.8 were sensitive to staurosporine-induced apoptosis under conditions in which Apt3.8 and Wbcl2 cells were resistant. Measurements of caspase activity and cytochrome c release in cytosolic extracts of dex and staurosporine-treated cells indicated that the recessive Apt- mutations effect steps upstream of mitochondrial dysfunction. Steady-state RNA levels of apoptosis-associated gene transcripts showed that the observed differential resistance of the Apt- cell lines could not be explained by altered expression of numerous Bcl-2 or Fas related genes. Transient transfection of human Fas gene coding sequences into the Apt- mutants and Wbcl2 cells did not induce apoptosis, even though these same cell lines were sensitive to ectopic expression of the FADD and caspase 8 genes. Taken together, these data provide genetic evidence for the existence of shared components in the dex- and Fas-mediated apoptotic pathways in W7.2 cells.

Animals↗
PubMed1999

Death receptor-mediated suicide: a novel target of autoimmune disease treatment.

In the thymus, based on the reactivity of their T-cell receptor with self-MHC and antigenic peptides, developing immature T-cells undergo positive and negative selection. Cells recognising self-peptides and MHC with high affinity are considered autoreactive, and thus potentially harmful, and are eliminated by induction of apoptotic cell death. Thymic negative selection is, however, only incomplete and autoreactive T-cells escape into the periphery. It is not the presence of autoreactive mature T- and B-lymphocytes as the underlying cause of tissue destruction and development of autoimmune diseases, but their uncontrolled and excessive clonal expansion upon activation by self-antigen. Thus, potent regulatory mechanisms must keep these autoreactive cells under control to avoid their inappropriate activation. Recent evidence indicates that death receptors of the tumour necrosis factor receptor family play a central role in mediating antigen receptor-induced suicide of autoreactive T-lymphocytes. Defects in these apoptosis-inducing regulatory mechanisms may result in the development of autoimmune diseases. Therefore, enhancing the cell's own suicide program, offers a most attractive therapeutic target for the treatment of autoimmune diseases.

Journal Article↗
PubMed1998

Fungal metabolite FR901228 inhibits c-Myc and Fas ligand expression.

Activation of T lymphocytes often leads to cellular activation, production of cytokines, entry into cell cycle, and expression of Fas (CD95) and Fas ligand (FasL). Although it is well established that the interaction of Fas and FasL results in apoptosis, mechanisms for regulated expression of Fas and FasL are unclear. Our previous work with antisense oligodeoxynucleotides suggested that the protooncogene c-myc is obligatory for activation-induced apoptosis. To study the relationship between c-myc and the Fas/FasL expression, we employed the antisense method and a newly identified fungal metabolite, FR901228, which has been shown to specifically inhibit expression of c-myc in fibroblasts. We found that FR901228 could effectively block activation-induced apoptosis in T cell hybridomas and this was correlated with its specific inhibition of c-myc expression. Both FR901228 and antisense oligodeoxynucleotide to c-myc had similar effect in inhibiting FasL expression. These treatments did not affect activation-induced production of IL-2, nor the expression of Fas. In addition, FR901228 inhibited the expression of FasL in 3T3 fibroblasts, but not these transfected with c-myc, supporting a specific role of c-myc in this process. Thus, c-Myc plays a fundamental role in the regulation of the expression of FasL, but not Fas and IL-2. Our data further defined the requirement of c-Myc in activation-induced apoptosis in T cells.

3T3 Cells↗
PubMed1998

Fas ligand is present in human erythroid colony-forming cells and interacts with Fas induced by interferon gamma to produce erythroid cell apoptosis.

Interferon gamma (IFNgamma) inhibits the growth and differentiation of highly purified human erythroid colony-forming cells (ECFCs) and induces erythroblast apoptosis. These effects are dose- and time-dependent. Because the cell surface receptor known as Fas (APO-1; CD95) triggers programmed cell death after activation by its ligand and because incubation of human ECFCs with IFNgamma produces apoptosis, we have investigated the expression and function of Fas and Fas ligand (FasL) in highly purified human ECFCs before and after incubation with IFNgamma in vitro. Only a small percentage of normal human ECFCs express Fas and this is present at a low level as detected by Northern blotting for the Fas mRNA and flow cytometric analysis of Fas protein using a specific mouse monoclonal antibody. The addition of IFNgamma markedly increased the percentage of cells expressing Fas on the surface of the ECFCs as well as the intensity of Fas expression. Fas mRNA was increased by 6 hours, whereas Fas antigen on the cell surface increased by 24 hours, with a plateau at 72 hours. This increase correlated with the inhibitory effect of IFNgamma on ECFC proliferation. CH-11 anti-Fas antibody, which mimics the action of the natural FasL, greatly enhanced IFNgamma-mediated suppression of cell growth and production of apoptosis, indicating that Fas is functional. Expression of FasL was also demonstrated in normal ECFCs by reverse transcriptase-polymerase chain reaction and flow cytometric analysis with specific monoclonal antibody. FasL was constitutively expressed among erythroid progenitors as they matured from day 5 to day 8 and IFNgamma treatment did not change this expression. Apoptosis induced by IFNgamma was greatly reduced by the NOK-2 antihuman FasL antibody and an engineered soluble FasL receptor, Fas-Fc, suggesting that Fas-FasL interactions among the ECFCs produce the erythroid inhibitory effects and apoptosis initiated by IFNgamma.

Animals↗
PubMed1998

Fas ligand- mediated killing by intestinal intraepithelial lymphocytes. Participation in intestinal graft-versus-host disease.

In vitro studies have demonstrated that intestinal intraepithelial lymphocytes (IEL) are constitutively cytotoxic; however, the mechanism and target of their cytotoxicity are unknown. Apoptosis of intestinal epithelial cells (IEC) and an increase in IEL numbers are classical signs of intestinal graft-versus-host disease (GVHD), although whether IEL can mediate IEC apoptosis directly in GVHD is unclear. Recent evidence suggests that target epithelial organ injury observed in GVHD is predominantly Fas-mediated; therefore, we investigated the possibility that IEL induce apoptosis of IEC through a Fas-mediated mechanism. Here, we demonstrate that the IEL isolated from normal mice readily display potent Fas ligand (FasL)-mediated killing activity after CD3 stimulation, and that IEC express Fas, suggesting that IEC are potential targets for FasL-mediated killing by IEL. In vitro, IEL isolated from GVHD mice have markedly increased FasL-mediated killing potential and are spontaneously cytolytic toward host-derived tumor cells predominantly through a Fas-mediated pathway. In vivo transfer of IEL isolated from GVHD mice induced significantly more IEC apoptosis in F1 wild-type mice than in Fas-defective F1lpr mice. Thus, these results demonstrate that FasL-mediated death of IEC by IEL is a major mechanism of IEC apoptosis seen in GVHD.

Animals↗
PubMed1998

Nodal CT density and total tumor volume as prognostic factors after radiation therapy of stage III/IV head and neck cancer.

PURPOSE: To determine whether the immunohistochemical expression of proliferation-associated antigens (proliferating cell nuclear antigen, MIB1) and the nuclear p53 reactivity in addition to total tumor volume, nodal CT density and T and N category are predictive for overall survival and locoregional tumor control in patients with squamous cell carcinoma of the head and neck region. MATERIALS AND METHODS: Between October 1989 and September 1993, 87 patients with biopsy proven head and neck cancer were randomly allocated to receive radiation alone or simultaneous radiation and chemotherapy as part of a multicenter trial with a total of 298 randomized patients. There were only inoperable lesions in UICC (1992) stage III (8%) and IV (92%). Radiotherapy was delivered with 180 cGy twice daily up to a total dose of 7020 cGy in 51 days. Three cycles of 2340 cGy each were separated by a rest period of 11 days. Chemotherapy consisted of cis-DDP, 5-fluorouracil and leucovorin and was repeated on days 22 and 44. Routinely-processed paraffin-embedded sections were stained using monoclonal antibodies for detection of proliferation-associated antigens (MIB1 and PCNA) and p53 oncoprotein to determine the labeling index (LI). In addition, the total tumor volume and the percentage of necrosis were measured using CT data. The median follow-up was 3.9 years (range 1.9-5.0 years). RESULTS: The overall survival and locoregional control for all 87 patients were 34 and 39% at 3 years, respectively. The addition of chemotherapy resulted in a better overall survival (27 versus 47%, P = 0.03) but did not influence locoregional control (31 versus 47%, P = 0.08). In univariate analysis, nodal CT density (P < 0.0001), total tumor volume (P < 0.0001), age (P = 0.001) and the MIB1-LI (P = 0.04) had a significant impact on overall survival. However, in the final Cox model only the nodal CT density (P = 0.0003) and age (P = 0.05) were independent prognostic factors for survival and only the nodal CT density (P = 0.0006) was an independent prognostic factor for locoregional control. The expression of the p53 oncoprotein was not found to have a clear predictive value. CONCLUSION: Nodal CT density, total tumor volume and age will remain the relevant prognostic factors in stage III/IV head and neck cancer.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1998

Inducible nonlymphoid expression of Fas ligand is responsible for superantigen-induced peripheral deletion of T cells.

Fas (CD95) and Fas ligand (FasL) play major roles in staphylococcal enterotoxin B (SEB)-induced peripheral deletion of Vbeta8+ T cells. We found that peripheral deletion was defective in radiation chimeras with non-functional tissue FasL, regardless of the FasL status of the bone marrow-derived cells. SEB induced a dramatic upregulation of FasL expression and function in nonlymphoid cells of liver and small intestine. This effect was resistant to inhibition by cyclosporin A, which also failed to inhibit peripheral deletion. In SCID animals nonlymphoid tissues did not express FasL in response to SEB unless transplanted lymphocytes were present. Thus, some immune responses induce FasL in nonlymphoid tissues, which in turn kills activated lymphocytes, leading to peripheral T cell deletion.

Animals↗
PubMed1998

DNA damaging agents induce expression of Fas ligand and subsequent apoptosis in T lymphocytes via the activation of NF-kappa B and AP-1.

Apoptosis induced by DNA damage and other stresses can proceed via expression of Fas ligand (FasL) and ligation of its receptor, Fas (CD95). We report that activation of the two transcription factors NF-kappa B and AP-1 is crucially involved in FasL expression induced by etoposide, teniposide, and UV irradiation. A nondegradable mutant of I kappa B blocked both FasL expression and apoptosis induced by DNA damage but not Fas ligation. These stimuli also induced the stress-activated kinase pathway (SAPK/JNK), which was required for the maximal induction of apoptosis. A 1.2 kb FasL promoter responded to DNA damage, as well as coexpression with p65 Rel or Fos/Jun. Mutations in the relevant NF-kappa B and AP-1 binding sites eliminated these responses. Thus, activation of NF-kappa B and AP-1 contributes to stress-induced apoptosis via the expression of FasL.

Antigens, Surface↗
PubMed1998

Sensitivity of S49.1 cells to anti-CD95 (Fas/Apo-1)-induced apoptosis: effects of CD95, Bcl-2 or Bcl-x transduction.

T lymphocytes have variable sensitivity to anti-CD95 which does not correlate closely with the level of CD95 expressed. To investigate this phenomenon, we screened murine T lymphocyte cultures for their sensitivity to anti-CD95. Subclones of the S49.1 cells showed widely variable sensitivity to anti-CD95 but similar levels of CD95. The resistant clones became sensitive after treatment with actinomycin D suggesting that they expressed resistance protein(s) with a high turnover relative to the CD95 apoptosis induction machinery. Our data suggest that the resistance protein(s) are not Bcl-2, Bcl-x, Fap-1 or Bag-1. Forced, increased expression of CD95 made most of the resistant cells more sensitive, but some remained resistant suggesting that the expression of the resistant protein(s) is heterogeneous and that increased CD95 levels does not always overcome the resistance.

Animals↗
PubMed1997

HIV-induced apoptosis of activated primary CD4+ T lymphocytes is not mediated by Fas-Fas ligand.

OBJECTIVE: To investigate the role of the Fas-Fas ligand (FasL) interaction in HIV-1-induced apoptosis of primary CD4+ T lymphocytes. DESIGN: Activated CD4+ T lymphocytes are the main target of HIV, and T-cell activation leads to the expression of Fas-FasL and enhances HIV-mediated apoptosis. Phytohemagglutinin-activated primary CD4+ T cells were infected with HIV; the process of cell death was examined, and whether the dying and dead cells were the productively infected cells. The modulation of Fas and FasL expression and its role in HIV-induced cell death was also investigated. METHODS: The number of viable and dead cells was determined by trypan blue exclusion. Apoptosis was quantified using an enzyme-linked immunosorbent assay measuring the release of cytoplasmic histone-associated DNA fragments. The percentage of HIV-infected cells was determined by FACS analysis, and viral production was assessed by a p24 core antigen assay. The following three markers, HIV-gp-120, annexin-V and 7-AAD, were used to monitor the apoptotic process in HIV-negative and positive cells. Fas and FasL expression was analyzed at the RNA level by reverse transcription polymerase chain reaction and at the protein level by flow cytometry. The contribution of Fas-FasL interactions to apoptosis was examined by blocking experiments using the antagonist ZB4 anti-Fas antibody. RESULTS: HIV-induced apoptosis in activated purified CD4+ T lymphocytes required infectious virus and was dose-dependent. Apoptosis in HIV-infected cultures was mostly confined to productively infected cells. The expression of Fas and FasL was not significantly modulated by infection and blocking Fas-FasL interactions did not reduce the extent of apoptosis. CONCLUSIONS: HIV-induced apoptosis of activated CD4+ T cells in vitro is confined to productively infected cells and is not mediated by a Fas-FasL interaction.

Apoptosis↗
PubMed1997

Unequal death in T helper cell (Th)1 and Th2 effectors: Th1, but not Th2, effectors undergo rapid Fas/FasL-mediated apoptosis.

T helper cell (Th) 1, but not Th2, effectors undergo rapid Fas/Fas ligand (FasL)-mediated, activation-induced cell death upon restimulation with antigen. Unequal apoptosis is also observed without restimulation, after a longer lag period. Both effectors undergo delayed apoptosis induced by a non-Fas-mediated pathway. When Th1 and Th2 effectors are co-cultured, Th2 effectors survive preferentially, suggesting the responsible factor(s) is intrinsic to each population. Both Th1 and Th2 effectors express Fas and FasL, but only Th2 effectors express high levels of FAP-1, a Fas-associated phosphatase that may act to inhibit Fas signaling. The rapid death of Th1 effectors leading to selective Th2 survival provides a novel mechanism for differential regulation of the two subsets.

Animals↗
PubMed1997

Human lung carcinomas express Fas ligand.

To reach a clinically detectable size, neoplasms must be able to suppress or evade a host immune response. Activated T cells may enter apoptosis in the presence of Fas ligand (FasL) (1), and tissue expression of FasL has been shown to contribute to immune privilege in the eye and testis (2, 3). We have demonstrated that all human lung carcinoma cell lines tested (16 of 16) express a Mr 38,000 protein consistent with FasL by immunoblotting, whereas the majority of resected tumors (23 of 28) show positive staining for FasL by immunohistochemistry. DNA sequencing of reverse transcription-PCR products from lung cancer cells and resected lung tumors confirms the presence of human FasL mRNA in these neoplastic tissues. Furthermore, lung carcinoma cells are capable of killing a Fas-sensitive human T cell line (Jurkat) in coculture experiments; this killing was inhibited by a recombinant form of the soluble portion of the Fas receptor (FasFc). FasL expression by neoplastic cells represents a potential mechanism for peripheral deletion of tumor-reactive T-cell clones.

DNA, Neoplasm↗
PubMed1996

Activation-induced cell death in murine T cell hybridomas. Differential regulation of Fas (CD95) versus Fas ligand expression by cyclosporin A and FK506.

We have previously reported that activation of murine T cell hybridomas leads to expression of Fas (CD95) and its ligand (FasL) which subsequently interact, even on the same cell, leading to apoptotic cell death. Since the immunosuppressive drugs cyclosporin A (CsA) and FK506 block activation-induced apoptosis in T cell hybridomas, we examined whether such compounds affect cell death by interfering with expression of Fas, FasL or both, or whether they block Fas signal transduction. We have found that CsA- and FK506-treated cells did not exhibit transcription of FasL mRNA after activation and were lacking functional FasL protein on their surface as determined by staining and the ability to induce apoptosis in Fas+ target cells. In contrast, no inhibition of the elevated Fas mRNA expression was observed in cells activated in the presence of CsA or FK506. Surprisingly, however, cell surface Fas levels were consistently lower on cells activated in the presence of immunosuppressive drugs than on activated cells, suggesting Fas expression is regulated at several levels. Nevertheless, cells activated in the presence of CsA or FK506 underwent apoptosis upon treatment with anti-Fas antibody, while unactivated cells did not. Furthermore, CsA and FK506 do not interfere with Fas signaling since anti-Fas induced apoptosis in Fas+ target cells was unaffected by these drugs. We therefore conclude that CsA and FK506 block activation-induced apoptosis in T cell hybridomas predominantly by interfering with activation signals leading to FasL expression and, further, that the regulation of the expression of Fas and FasL on activated T cells is differentially controlled.

Animals↗