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J Tschopp

Publications and source records attributed to J Tschopp.

At least 37 records · Page 2Linked to original sources
PubMed2001

Expression of Fas (APO-1/CD95) and Fas ligand (FasL) in human neuroblastoma.

BACKGROUND AND PROCEDURE: To determine the possible role of Fas/FasL system in the particularly heterogeneous behaviour of neuroblastoma (NB), we have measured the functional expression of Fas and its ligand, FasL, in primary neuroblastoma samples and cell lines by immunohistochemistry and flow cytometry. RESULTS: Our results reveal that while Fas expression is associated with low stage and more mature tumors, heterogeneous FasL expression was mostly detected in high stage tumors, with our apparent correlation to MYCN amplification. Flow cytometric analysis of cell lines demonstrated a high expression of Fas in epithelial-type, HLA class I positive cell lines, which was lost upon activation with phorbol esters. In contrast, Fas ligand was detected in only a small subset of cell lines. CONCLUSIONS: In some cell lines, cytotoxic assays revealed the ability of NB-associated Fas receptor to transduce an apoptotic signal upon triggering. The pattern of functional Fas/FasL expression in tumours and cell lines suggests that this system may be involved in the evasion of highly malignant neuroblastoma cells to host immune response.

Apoptosis↗
PubMed2001

IgG subclass switch capacity is low in switched and in IgM-only, but high in IgD+IgM+, post-germinal center (CD27+) human B cells.

Recent studies have shown that in humans the germinal center reactions produce three types of V(D)J mutated B cells in similar proportions, i.e. Ig-switched, IgD-IgM+ (IgM-only) and IgD+IgM+ cells, and that together they form the CD27+ compartment of recirculating B cells. We investigated the Ig isotype switch capacity of these cells. Peripheral blood B subsets were sorted and IgG subclass secretion in presence or absence of IL-4 was compared in B cell assays which lead to Ig secretion in all (coculture with EL-4 thymoma cells) or only in CD27+ (CD40L stimulation) B cells. Already switched IgG+ B cells showed no significant sequential switch and IgM-only cells also had a low switch capacity, but IgD+CD27+ switched as much as IgD+CD27- B cells to all IgG subclasses. Thus, in switched B cells some alterations compromising further switch options occur frequently; IgM-only cells may result from aborted switch. However, IgD+CD27+ human B cells, extensively V(D)J mutated and "naive" regarding switch, build up a repertoire of B cells combining (1) novel cross-reactive specificities, (2) increased differentiation capacity (including after T-independent stimulation by Staphylococcus aureus Cowan I) and (3) the capacity to produce appropriate isotypes when they respond to novel pathogens.

B-Lymphocyte Subsets↗
PubMed2001

Regulation of lymphocyte proliferation and death by FLIP.

Lymphocyte homeostasis is a balance between lymphocyte proliferation and lymphocyte death. Tight control of apoptosis is essential for immune function, because its altered regulation can result in cancer and autoimmunity. Signals from members of the tumour-necrosis-factor receptor (TNF-R) family, such as Fas and TNF-R1, activate the caspase cascade and result in lymphocyte death by apoptosis. Anti-apoptotic proteins, such as FLIP (also known as FLICE/caspase-8 inhibitory protein) have recently been identified. FLIP expression is tightly regulated in T cells and might be involved in the control of both T-cell activation and death. Abnormal expression of FLIP might have a role not only in autoimmune diseases, but also in tumour development and cardiovascular disorders.

Animals↗
PubMed2001

APRIL, a new member of the tumor necrosis factor family, modulates death ligand-induced apoptosis.

APRIL (a proliferation-inducing ligand) is a newly identified member of the tumor necrosis factor (TNF) family. Tumor growth-promoting as well as apoptosis-inducing effects of APRIL have been described. Here, we report that five of 12 human malignant glioma cell lines express APRIL. APRIL gene transfer experiments revealed that malignant glioma cells are refractory to growth-promoting activity of APRIL in vitro and in vivo. Interestingly, ectopic expression of APRIL confers minor protection from apoptotic cell death induced by the death ligands, CD95 ligand (CD95L) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)/Apo2 ligand (Apo2L). This antiapoptotic activity is specific for death ligand/receptor-mediated apoptosis since APRIL does not protect glioma cells from the cytotoxicity of the drugs, teniposide, vincristine, lomustine or cisplatin. Ectopic expression of APRIL is associated with the upregulation of X-linked inhibitor of apoptosis protein (XIAP), providing a possible explanation for the antiapoptotic activity observed here. In contrast, APRIL does not regulate the expression levels of the antiapoptotic proteins FLICE-inhibitory protein (FLIP), Bcl-2 or Bcl-X(L). These findings suggest that APRIL is involved in the regulation of death ligand-induced apoptotic signaling in malignant glioma cells.

Animals↗
PubMed2001

Selective expression of FLIP in malignant melanocytic skin lesions.

FLIP (FLICE Inhibitory Protein) is a recently identified intracellular inhibitor of caspase-8 activation that potently inhibits cell death mediated by all death receptors including Fas and TRAIL. FLIP has recently been shown to favor tumor growth and immune escape in mouse tumor models. We analyzed FLIP expression by immunohistochemistry in a panel of 61 benign and malignant human melanocytic skin lesions. FLIP expression was undetectable in all but one benign melanocytic lesion (31/32, 97%). In contrast, FLIP was strongly expressed in most melanomas (24/29 = 83%). Overexpression of FLIP by transfection in a Fas- and TRAIL-sensitive human melanoma cell line rendered this cell line more resistant to death mediated by both TRAIL and FasL. Selective expression of FLIP by human melanomas may confer in vivo resistance to FasL and TRAIL, thus representing an additional mechanism by which melanoma cells escape immune destruction.

Antibody Specificity↗
PubMed2001

NF-kappaB signals induce the expression of c-FLIP.

Activation of the transcription factor NF-kappaB is a major effector of the inducible resistance to death receptor-mediated apoptosis. Previous evidence indicates that the combined transcriptional activation of TRAF-1, TRAF-2, IAP-1, and IAP-2 is required to suppress cell death by tumor necrosis factor (TNF). Here we show that NF-kappaB activation upregulates the caspase 8 inhibitor FLIP, resulting in increased resistance to Fas ligand (FasL) or TNF. Restoration of either the full-length 55-kDa long form of FLIP or an alternatively spliced short form of FLIP in NF-kappaB null cells inhibits TNF- and FasL-induced cell death efficiently, whereas the expression of IAP or TRAF family members only partially rescues cells from death. Resistance to either FasL- or TNF-induced apoptosis is overcome when cells are incubated in the presence of the protein synthesis inhibitor cycloheximide. This treatment leads to the rapid downregulation of FLIP but not to that of TRAF2. Our findings suggest that FLIP is an important mediator of NF-kappaB-controlled antiapoptotic signals.

Apoptosis↗
PubMed2000

Fas engagement induces the maturation of dendritic cells (DCs), the release of interleukin (IL)-1beta, and the production of interferon gamma in the absence of IL-12 during DC-T cell cognate interaction: a new role for Fas ligand in inflammatory responses.

Ligation of the Fas (CD95) receptor leads to an apoptotic death signal in T cells, B cells, and macrophages. However, human CD34(+)-derived dendritic cells (DCs) and mouse DCs, regardless of their maturation state, are not susceptible to Fas-induced cell death. This resistance correlates with the constitutive expression of the Fas-associated death domain-like IL-1beta-converting enzyme (FLICE)-inhibitory protein (FLIP) ligand. We demonstrate a new role of Fas in DC physiology. Engagement of Fas on immature DCs by Fas ligand (FasL) or by anti-Fas antibodies induces the phenotypical and functional maturation of primary DCs. Fas-activated DCs upregulate the expression of the major histocompatibility complex class II, B7, and DC-lysosome-associated membrane protein (DC-LAMP) molecules and secrete proinflammatory cytokines, in particular interleukin (IL)-1beta and tumor necrosis factor alpha. Mature DCs, if exposed to FasL, produce even higher amounts of IL-1beta. Importantly, it is possible to reduce the production of IL-1beta and interferon (IFN)-gamma during DC-T cell interaction by blocking the coupling of Fas-FasL with a Fas competitor. Finally, during cognate DC-T cell recognition, IL-12 (p70) could not be detected at early or late time points, indicating that Fas-induced, IFN-gamma secretion is independent of IL-12.

Apoptosis↗
PubMed2000

A soluble form of B cell maturation antigen, a receptor for the tumor necrosis factor family member APRIL, inhibits tumor cell growth.

A proliferation-inducing ligand (APRIL) is a ligand of the tumor necrosis factor (TNF) family that stimulates tumor cell growth in vitro and in vivo. Expression of APRIL is highly upregulated in many tumors including colon and prostate carcinomas. Here we identify B cell maturation antigen (BCMA) and transmembrane activator and calcium modulator and cyclophilin ligand (CAML) interactor (TACI), two predicted members of the TNF receptor family, as receptors for APRIL. APRIL binds BCMA with higher affinity than TACI. A soluble form of BCMA, which inhibits the proliferative activity of APRIL in vitro, decreases tumor cell proliferation in nude mice. Growth of HT29 colon carcinoma cells is blocked when mice are treated once per week with the soluble receptor. These results suggest an important role for APRIL in tumorigenesis and point towards a novel anticancer strategy.

3T3 Cells↗
PubMed2000

Studies on the interaction between TWEAK and the death receptor WSL-1/TRAMP (DR3).

WSL-1/TRAMP (DR3) is a member of the tumour necrosis factor (TNF) receptor superfamily which exhibits effects on NF-kappaB activation and apoptosis. TWEAK, a novel TNF-related molecule, has been proposed as the ligand for this receptor. Utilising both human and murine TWEAK ligand, it is shown that TWEAK and WSL-1/TRAMP do not interact in an in vitro binding assay and that TWEAK binds strongly to cells that do not express WSL-1/TRAMP on the cell surface. Biological activity of TWEAK is also observed in these cells. Finally, cells isolated from WSL-1/TRAMP knockout mice are shown to retain their ability to interact with TWEAK. These results suggest that WSL-1/TRAMP is not the major receptor for TWEAK

Animals↗
PubMed2000

BAFF mediates survival of peripheral immature B lymphocytes.

B cell maturation is a very selective process that requires finely tuned differentiation and survival signals. B cell activation factor from the TNF family (BAFF) is a TNF family member that binds to B cells and potentiates B cell receptor (BCR)-mediated proliferation. A role for BAFF in B cell survival was suggested by the observation of reduced peripheral B cell numbers in mice treated with reagents blocking BAFF, and high Bcl-2 levels detected in B cells from BAFF transgenic (Tg) mice. We tested in vitro the survival effect of BAFF on lymphocytes derived from primary and secondary lymphoid organs. BAFF induced survival of a subset of splenic immature B cells, referred to as transitional type 2 (T2) B cells. BAFF treatment allowed T2 B cells to survive and differentiate into mature B cells in response to signals through the BCR. The T2 and the marginal zone (MZ) B cell compartments were particularly enlarged in BAFF Tg mice. Immature transitional B cells are targets for negative selection, a feature thought to promote self-tolerance. These findings support a model in which excessive BAFF-mediated survival of peripheral immature B cells contributes to the emergence and maturation of autoreactive B cells, skewed towards the MZ compartment. This work provides new clues on mechanisms regulating B cell maturation and tolerance.

Animals↗
PubMed2000

Fas-mediated cell death in toxic epidermal necrolysis and graft-versus-host disease: potential for therapeutic inhibition.

Death receptors are a growing family of transmembrane proteins which can detect the presence of specific extracellular death signals and rapidly trigger cellular destruction by apoptosis. The best studied to date is Fas (CD95). Expression and signalling by Fas and its ligand (FasL, CD95L) is a tightly regulated process essential for key physiological functions in a variety of organs, including the maintenance of immune homoeostasis. Recently, strong evidence has shown that dysregulation of Fas expression and/or signalling contributes to the pathogenesis of toxic epidermal necrolysis and acute graft-versus-host disease. With these new developments, strategies for modulating the function of Fas signalling have emerged and opened up novel therapeutic possibilities. Specific blockade of Fas, for example with intravenous immunoglobulin preparations containing specific anti-Fas antibodies, has shown great promise in the treatment of toxic epidermal necrolysis and may also be useful in the treatment of acute graft-versus-host disease. Further developments in this field may have important clinical implications for the treatment of such diseases.

Acute Disease↗
PubMed2000

Three adenovirus E3 proteins cooperate to evade apoptosis by tumor necrosis factor-related apoptosis-inducing ligand receptor-1 and -2.

Adenovirus encodes multiple gene products that regulate proapoptotic cellular responses to viral infection mediated by both the innate and adaptive immune systems. The E3-10.4K and 14.5K gene products are known to modulate the death receptor Fas. In this study, we demonstrate that an additional viral E3 protein, 6.7K, functions in the specific modulation of the two death receptors for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). The 6.7K protein is expressed on the cell surface and forms a complex with the 10.4K and 14.5K proteins, and this complex is sufficient to induce down-modulation of TRAIL receptor-1 and -2 from the cell surface and reverse the sensitivity of infected cells to TRAIL-mediated apoptosis. Down-modulation of TRAIL-R2 by the E3 complex is dependent on the cytoplasmic tail of the receptor, but the death domain alone is not sufficient. These results identify a mechanism for viral modulation of TRAIL receptor-mediated apoptosis and suggest the E3 protein complex has evolved to regulate the signaling of selected cytokine receptors.

Adenoviridae↗
PubMed2000

FIST/HIPK3: a Fas/FADD-interacting serine/threonine kinase that induces FADD phosphorylation and inhibits fas-mediated Jun NH(2)-terminal kinase activation.

Fas is a cell surface death receptor that signals apoptosis. Several proteins have been identified that bind to the cytoplasmic death domain of Fas. Fas-associated death domain (FADD), which couples Fas to procaspase-8, and Daxx, which couples Fas to the Jun NH(2)-terminal kinase pathway, bind independently to the Fas death domain. We have identified a 130-kD kinase designated Fas-interacting serine/threonine kinase/homeodomain-interacting protein kinase (FIST/HIPK3) as a novel Fas-interacting protein. Binding to Fas is mediated by a conserved sequence in the COOH terminus of the protein. FIST/HIPK3 is widely expressed in mammalian tissues and is localized both in the nucleus and in the cytoplasm. In transfected cell lines, FIST/HIPK3 causes FADD phosphorylation, thereby promoting FIST/HIPK3-FADD-Fas interaction. Although Fas ligand-induced activation of Jun NH(2)-terminal kinase is impaired by overexpressed active FIST/HIPK3, cell death is not affected. These results suggest that Fas-associated FIST/HIPK3 modulates one of the two major signaling pathways of Fas.

Adaptor Proteins, Signal Transducing↗
PubMed2000

The tumor necrosis factor-related apoptosis-inducing ligand receptors TRAIL-R1 and TRAIL-R2 have distinct cross-linking requirements for initiation of apoptosis and are non-redundant in JNK activation.

Overexpression of the tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) receptors, TRAIL-R1 and TRAIL-R2, induces apoptosis and activation of NF-kappaB in cultured cells. In this study, we have demonstrated differential signaling capacities by both receptors using either epitope-tagged soluble TRAIL (sTRAIL) or sTRAIL that was cross-linked with a monoclonal antibody. Interestingly, sTRAIL was sufficient for induction of apoptosis only in cell lines that were killed by agonistic TRAIL-R1- and TRAIL-R2-specific IgG preparations. Moreover, in these cell lines interleukin-6 secretion and NF-kappaB activation were induced by cross-linked or non-cross-linked anti-TRAIL, as well as by both receptor-specific IgGs. However, cross-linking of sTRAIL was required for induction of apoptosis in cell lines that only responded to the agonistic anti-TRAIL-R2-IgG. Interestingly, activation of c-Jun N-terminal kinase (JNK) was only observed in response to either cross-linked sTRAIL or anti-TRAIL-R2-IgG even in cell lines where both receptors were capable of signaling apoptosis and NF-kappaB activation. Taken together, our data suggest that TRAIL-R1 responds to either cross-linked or non-cross-linked sTRAIL which signals NF-kappaB activation and apoptosis, whereas TRAIL-R2 signals NF-kappaB activation, apoptosis, and JNK activation only in response to cross-linked TRAIL.

Antibodies, Monoclonal↗
PubMed2000

Loss of caspase-8 expression in highly malignant human neuroblastoma cells correlates with resistance to tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis.

Human neuroblastoma (NB) is a highly heterogeneous childhood cancer that is aggressively malignant or can undergo spontaneous regression that may involve apoptosis. NB-derived cell lines were tested for their sensitivity to apoptosis induced by the tumor-selective ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Noninvasive S-type cell lines (NB cell lines of substrate adherent phenotype) are highly sensitive to TRAIL, whereas invasive N-type cell lines (NB cell lines of neuronal phenotype) are resistant. Whereas both S- and N-type cell lines express TRAIL-R2, FADD, and caspase-3 and -10, only S-type cells express caspase-8. Reduced levels of caspase-8 protein were also observed in a malignant stage IV NB tumor when compared with a benign ganglioneuroma. The caspase-8 gene is not deleted in either N-type NB cell lines or high-stage NB tumors. Caspase-8 expression can be induced by demethylation with 5-aza-2'deoxycytidine, which enhances sensitivity to TRAIL. Therefore, caspase-8 expression is silenced in malignant NB, which correlates to tumor severity and resistance to TRAIL-induced apoptosis.

Animals↗
PubMed2000

Fas ligand-induced c-Jun kinase activation in lymphoid cells requires extensive receptor aggregation but is independent of DAXX, and Fas-mediated cell death does not involve DAXX, RIP, or RAIDD.

Jun kinase signaling can be elicited by death receptor activation, but the mechanism and significance of this event are still unclear. It has been reported that cross-linking Abs to Fas trigger c-Jun N-terminal kinase (JNK) signaling via caspase-mediated activation of MEKK1 (JNK kinase kinase), elevation of ceramide levels or by recruitment of death domain associated protein (DAXX) to Fas. The effect of physiological ligand for Fas on JNK signaling was never investigated, although evidence is accumulating that Fas ligand is able to induce cellular responses distinct from those evoked by Ab-mediated cross-linking of Fas. Therefore, we investigated the effect of Fas ligand on JNK signaling. Like its ability to induce cell death, Fas ligand reliably activated JNK only upon extensive aggregation of the receptor. Although this was partially dependent on caspase activation, DAXX was not required. DAXX and other death receptor-associated proteins, which have been reported to bind directly or indirectly to Fas, such as receptor interacting protein (RIP) and RIP-associated ICH-1/CED-3-homologous protein with a death domain (RAIDD), were shown to be dispensable for Fas ligand-induced apoptosis.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Cysteine 230 is essential for the structure and activity of the cytotoxic ligand TRAIL.

Unlike other tumor necrosis factor family members, the cytotoxic ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)/Apo-2L contains an unpaired cysteine residue (Cys(230)) in its receptor-binding domain. Here we show that the biological activity of both soluble recombinant TRAIL and cell-associated, full-length TRAIL is critically dependent on the presence of Cys(230). Mutation of Cys(230) to alanine or serine strongly affected its ability to kill target cells. Binding to its receptors was decreased by at least 200-fold, and the stability of its trimeric structure was reduced. In recombinant TRAIL, Cys(230) was found engaged either in interchain disulfide bridge formation, resulting in poorly active TRAIL, or in the chelation of one zinc atom per TRAIL trimer in the active, pro-apoptotic form of TRAIL.

Amino Acid Sequence↗