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S Chouaib

Publications and source records attributed to S Chouaib.

At least 91 records · Page 5Linked to original sources
PubMed1992

Heterogeneity among human nasopharyngeal carcinoma cell lines for inflammatory cytokines mRNA expression levels.

Using polymerase chain reaction (PCR), we confirmed the expression of interleukin-1 alpha (IL-1 alpha) by the human nasopharyngeal carcinoma (NPC) cell line C15 without contribution of either human IL-1 beta or mouse IL-1 alpha in the biological activity previously found in C15. However we showed that IL-1 alpha was not expressed in all NPCs. IL-1 beta and/or tumor necrosis factor (TNF)-alpha genes could also be activated, independently from the number of Epstein Barr Virus (EBV) copies harbored by the cells. Interestingly, the primary tumor C15 showed a profile of TNF-sensitive tumor while C17, C18 and C19 which were derived from metastasis have a typical profile of TNF-resistant cells. Furthermore, the inflammatory cytokines whose genes are classically induced by IL-1 and TNF were found expressed only in C17 and C19 suggesting another level of heterogeneity among NPCs.

Animals↗
PubMed1992

Tumor necrosis factor-mediated cell lysis in vitro: relationship to cAMP accumulation and guanine nucleotide-binding proteins.

We have investigated the modulation of tumor necrosis factor (TNF)-mediated tumor cell lysis by cAMP. Among a panel of human breast tumor cell lines, MCF7 and MDA MB 231 were shown to be, respectively, sensitive and resistant to TNF-mediated cell lysis in vitro. 125I-labeled TNF-binding experiments demonstrated that both cell lines bind TNF, indicating that the differential sensitivity to TNF was not related to TNF receptor expression. To study the relationship between TNF-mediated cell lysis and cAMP accumulation, cAMP measurement was performed following TNF treatment. Our data show that TNF alone did not induce an enhancement of intracellular cAMP accumulation either in the TNF-sensitive or in the TNF-resistant cell line. Experiments in which cells were exposed to forskolin revealed that this cAMP elevating drug was efficient in enhancing the sensitivity to TNF of MCF7 cell line. This potentiating effect of forskolin was maximal for suboptimal concentrations of TNF (10 ng/ml), reaching up to 100% when forskolin was added at 100 microM. However, co-stimulating with forskolin of either MDA MB 231 or a TNF-resistant MCF7 clone (MCF7-R-A1) did not induce any reversal of resistance to TNF. We further assessed the interaction of TNF with transmembrane signalling and the possible involvement of guanine nucleotide-binding proteins (G-proteins). Bacterial toxin-catalyzed ADP ribosylation of MCF7 and MDA MB 231 membranes was, therefore, performed. Using cholera toxin, we demonstrate that TNF treatment did not quantitatively alter the activity of stimulatory G-proteins either in MCF7 or MDA MB 231 cell line. In contrast, pertussis toxin-catalyzed ADP ribosylation experiments suggest a functional coupling of TNF receptors to a 40-kDa pertussis toxin-sensitive G-protein in the TNF-sensitive MCF78 cell line but not in the TNF-resistant MDA MB 231 cell line. Taken together, these data indicate that cAMP might play a role in TNF-mediated cell lysis and are in support of the involvement of a pertussis toxin-sensitive G-protein in TNF-mediated MCF7 cells lysis.

Adenosine Diphosphate Ribose↗
PubMed1992

Interleukin-4 differentially regulates interleukin-2-mediated and CD2-mediated induction of human lymphokine-activated killer effectors.

Natural killer (NK) cells can be differentiated into lymphokine-activated killer (LAK) effectors following stimulation with interleukin (IL)-2. This induction can be negatively regulated by IL-4. In this study, we demonstrate that the stimulation of NK cells through the CD2 pathway with (9-1 + 9.6) monoclonal antibodies can also induce these cells to secrete tumor necrosis factor-alpha (TNF-alpha) and to differentiate into LAK effectors. More importantly, our data indicate that, in contrast to the IL-2-induced LAK generation, the anti-CD2-triggered LAK activity was not regulated by IL-4. IL-4 was found to enhance the LAK activity as well as NK cell proliferation following activation with anti-CD2 by a mechanism involving, at least in part, an increased TNF-alpha production. Using immobilized monoclonal antibodies against the Fc receptor (Fc gamma RIII or CD16) for NK stimulation, we also observed that the anti-CD16-induced LAK activity was not inhibited by IL-4. These data further point to a pivotal role of TNF-alpha as a regulatory cytokine in anti-CD2-induced LAK generation, and suggest that IL-4 could serve as a discriminatory factor between two distinct pathways involved in the activation of non-MHC-restricted cytotoxicity.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1992

Serum levels and receptor expression of tumor necrosis factor-alpha following human allogeneic and autologous bone marrow transplantation.

We have investigated tumor necrosis factor-alpha levels in serum samples of patients before and after allogenic (16 patients) or autologous (8 patients) bone marrow transplantation. A sensitive immunoradiometric assay for monitoring levels of endogenous tumor necrosis factor-alpha was used. The serum levels of tumor necrosis factor-alpha were found to be relatively low (ranging from less than 15 to 77 pg/ml). Among 13 patients having graft-versus-host disease following allogeneic bone marrow transplantation 8 patients did not have detectable tumor necrosis factor-alpha (less than 15 pg/ml) while 4 out of 8 patients undergoing autologous bone marrow transplantation had detectable tumor necrosis factor-alpha levels (15 pg/ml), indicating a lack of correlation between tumor necrosis factor-alpha serum levels and the occurrence of graft-versus-host disease. Because the tumor necrosis factor-alpha levels detected in patient sera could be regulated by TNF-receptor expression, the presence of TNF-receptor on patients' peripheral blood mononuclear cells was also studied using fluorescent liposome-conjugated tumor necrosis factor-alpha and immunofluorescence analysis. Our data indicate that peripheral blood mononuclear cells of some patients receiving either autologous or allogeneic bone marrow transplantation expressed significant levels of TNF-receptors, suggesting a lack of correlation between TNF-receptor expression and graft-versus-host disease development.

Bone Marrow Transplantation↗
PubMed1992

[Tumor necrosis factor: pleiotropic cytokine].

Originally described for its capacity to induce hemorrhagic necrosis of transplantable tumors in mice, TNF-alpha also exerts cytotoxic effects against some tumor cell lines in vitro. It is now known that TNF is an essential mediator of cellular immunity and a wide variety of biological activities of TNF in vitro and in vivo has been reported. TNF is an important mediator of inflammation and is involved during the pathogenesis of several auto-immune, infectious or cancer diseases. While some immunomodulatory properties of TNF have at least been partially elucidated, the biochemical basis of TNF cytotoxic action remains largely unknown. Furthermore, the molecular mechanisms of TNF susceptibility have yet to be clarified. Clinical studies with recombinant TNF as an anticancer agent are encouraging. Multiple phase I and phase II trials have been carried out without major therapeutic effect. In fact, TNF resistance and TNF-induced systemic toxicity are two major limitations for the use of TNF as an antineoplastic agent. The clinical application of human TNF remains an area of active research and innovative approaches such as gene therapy need to be elaborated. The elucidation of the process of lysis and the modulation of TNF resistance are crucial to the future development of TNF and its use in antitumor therapy.

Cytokines↗
PubMed1991

More insights into the complex physiology of TNF.

Tumor necrosis factor (TNF), a multifactorial cytokine involved in a plethora of cell regulatory and differentiative processes, was the subject of a recent conference. It is perhaps best known as a major player in the pathophysiology of numerous diseases but TNF clearly has many beneficial effects and is considered to be a promising therapeutic agent.

Animals↗
PubMed1991

Evidence that residual host cells surviving the conditioning regimen to allogeneic bone marrow transplantation inhibit donor hematopoiesis in vitro--the role of TNF-alpha.

Blood cells were obtained from patients selected for allogeneic bone marrow transplantation who had undergone a conditioning regimen (CR) with high-dose chemotherapy and total body irradiation. The majority of residual cells bore CD3 antigen (range: 68-98%), and the CD4/CD8 ratio was normal. The effect of these residual/radioresistant cells on donor bone marrow hematopoiesis was investigated in eleven cases. Growth of donor CFU-GM and BFU-E was inhibited by 22-65% and 29-77%, respectively, when donor marrow was cocultured with residual cells at various ratios. In contrast, blood cells obtained from two patients prior to CR had no inhibitory effect. Supernatants obtained following incubation of residual cells from 9 patients were able to inhibit the growth of CFU-GM and BFU-E from normal unrelated subjects, whereas supernatants obtained before CR and from cultured normal marrow had no inhibitory effect. In addition, in blocking experiments, an anti-TNF-alpha MoAb was able to prevent this inhibition. Thus, TBI might be able to select and/or activate cells responsible for hematopoietic growth inhibition by a mechanism involving, at least in part, TNF-alpha.

Adult↗
PubMed1991

[TNF: antitumoral agent at the border lines of immunity and inflammation].

Tumor Necrosis Factor-alpha (TNF) is mainly produced by activated monocytes and exerts pleiotropic biological effects on a wide variety of both normal and transformed cells. Originally described for its capacity to induce hemorrhagic necrosis of transplantable tumors in vivo and cytolysis of some tumor cells in vitro, TNF has also been shown to play an essential role during the inflammatory response, exerting dual, both beneficial and deleterious, effects. TNF, via a local production appears to be a key cytokine involved in antiviral, antibacterial and antiparasitic host defense mechanisms. Contreversely, deregulation of the inflammatory and immune reactions can be associated with a systemic TNF production, leading to toxic secondary effects. Recent cloning of the TNF receptors has provided additional insights in the complex physiology of TNF. It is now clearly established that both type I and type II TNF receptors can be cleaved and released as TNF binding proteins. The soluble fragments of TNF receptors can inhibit TNF-mediated tumor cell lysis in vitro and might therefore serve as regulators of TNF action. The antitumor potency of TNF also reflects the pleiotropic aspect of TNF. TNF-induced tumor regression, observed in various preclinical studies, appears to result from at least three distinct biological effects: mainly hemorrhagic necrosis via TNF action on tumor endothelium, TNF immunomodulatory activity on immune effector cells, and presumably a direct TNF-mediated cytotoxic effect against tumor cells. From the clinical trials performed with distinct recombinant materials a consensus has emerged about the disappopinting anticancer efficacy of TNF used in systemic administration. Further studies, aimed at better understanding the complex action of TNF, are required to possibly enhance its therapeutic index and subsequently to assess whether TNF still remains a promising therapeutic agent.

Animals↗
PubMed1991

Role of calcium on interleukin-1 production by monocytes: its relevance during T cell proliferation.

T cell proliferation, in the presence of monocytes, triggered either by an anti-CD3 monoclonal antibody (mAb) or by a mitogenic pair of anti-CD2 mAbs was inhibited either by the calcium chelator EGTA or the calcium channel blocker nifedipin. Antibodies against interleukin-1 (IL-1) inhibited T cell proliferation in both mitogenic systems. However inhibition achieved by anti-IL-1 beta Ab was greater than by anti-IL-1 alpha Ab while the combination of both anti-rIL-1 alpha Ab + anti-rIL-1 beta could completely inhibit the CD3-triggered T cell proliferation. On the other hand, IL-1 production by LPS-stimulated monocytes was strongly decreased both by EGTA and nifedipin. Northern blot analysis showed that this inhibition paralleled a decrease of IL-1 alpha and beta messenger RNA (mRNA) expression only in the presence of EGTA but not in the presence of nifedipin. These results indicate that EGTA acted at the transcriptional level while nifedipin acted at a yet undefined posttranscriptional level. Thus, it is suggested that the impairment of T cell proliferation by calcium inhibitors could result not only from an effect on Ca2+ influx in T cells but also from interfering with the function of accessory cells, such as the production of IL-1.

Antibodies, Monoclonal↗
PubMed1991

Tumor necrosis factor alpha: a costimulator for cytotoxic cell differentiation.

Large granular lymphocytes (LGL) can be activated by interleukin-2 (IL-2) into lymphokine-activated killers (LAK). Tumor Necrosis factor alpha was found to act synergistically with very low concentrations of IL-2 which were ineffective by themselves in inducing LAK activity. We demonstrate that the failure of low doses of IL-2 to induce LAK generation was related to their incapacity to induce TNF production by LGL. When specific antibodies against TNF were added to the culture, the differentiation of LGL into LAK effectors by optimal concentrations of IL-2 in our system was partially inhibited suggesting that TNF may be a physiologic mediator in the sequential activation stages of LGL into LAK effectors. We have also investigated the functional interaction between IL-2 and TNF on the generation of alloreactive CTL. Using primary mixed cultures of lymphocytes from a MHC-recombinant sibling identical for MHC class II antigens and displaying MHC class I disparity, our data indicate that addition of exogenous TNF at the sensitizing phase of the primary mixed lymphocyte reaction did not result in CTL activation. However, when simultaneously added with IL-2, TNF could promote an optimal induction of cytotoxic T cell generation. The TNF property to potentiate the cytotoxic function appears to involve an enhancement of IL-2 induced serine esterase activity suggesting that TNF may affect some components of the cellular lytic machinery. In conclusion the data presented here are most consistent with the suggestion that TNF could increase the IL-2 signaling efficiency or potentiate activation signaling involved in the acquisition of lytic competence by cytotoxic T cells.

Cell Differentiation↗
PubMed1990

Potentiation of TNF-mediated cell killing by VP-16: relationship to DNA single-strand break formation.

Interaction between tumor necrosis factor (TNF) and the DNA topoisomerase II inhibitor, etoposide VP-16, in cell killing has been studied. To accurately investigate the nature of DNA damage during the cell killing process, experiments were assessed using the highly TNF-sensitive WEHI164.13 murine fibrosarcoma clone and DNA filter elution methodology. Concomitant treatment of cells with combination of TNF/VP-16 resulted in marked enhancement of cell lysis. Using the alkaline elution technique, we show that TNF fails to induce DNA single-strand breaks as compared to those generated by VP-16. In addition, the potentiating effect of VP-16 on TNF-mediated WEHI164.13 cell killing was not associated with an increase in its intrinsic activity with respect to DNA single-strand break formation. While the 2 phospholipase A2 inhibitors, quinacrine and dexamethasone, were efficient in inhibiting TNF-mediated cell lysis, only quinacrine was efficient in selectively abrogating the TNF/VP-16 cell killing pathway. The inhibitory effect of quinacrine on VP-16/TNF-mediated cell lysis was accompanied by a marked decrease in VP-16-mediated DNA single-strand break generation. Taken together, our findings suggest that TNF and TNF/VP-16 treatments may involve different events during cell killing and support the hypothesis that 2 signals are required for optimal induction of cell lysis by the combination of VP-16/TNF: one signal provided by VP-16 resulting in topoisomerase II inhibition and subsequent DNA single-strand break generation, and a second signal involving TNF.

Animals↗
PubMed1990

Evidence for tumor necrosis factor-alpha involvement in the optimal induction of class I allospecific cytotoxic T cells.

We have investigated the functional interaction between IL-2 and TNF on the generation of alloreactive CTL. The study was performed by using primary mixed cultures of lymphocytes from a MHC-recombinant sibling identical for MHC class II Ag (DR, DP, DQ) and displaying MHC class I disparity. Our data show that MHC class I disparity can trigger the induction of TNF receptor without promoting significant TNF production. Addition of exogenous TNF at the sensitizing phase of the primary mixed lymphocyte reaction did not result in CTL activation. However, when simultaneously added with IL-2, TNF could promote an optimal induction of cytotoxic T cell generation. The enhanced lytic ability of MHC class-I primed CTL by TNF was associated with a selective up-regulation of Tac Ag and subsequent amplification of cell proliferation. Furthermore, TNF was also found to induce a considerable increase in IL-2-induced intracellular benzyloxycarbonyl-L-lysine thiobenzylester-esterase activity by MHC class I-primed cells. TNF did not affect the expression of LFA1, CD2, CD4, and CD8, molecules that are associated with CTL-target interactions, on responder cells. These results extend our earlier observations on the role of class I MHC molecules that may function to transduce activation signals and suggest that TNF may be a potent mediator involved in the IL-2-induced acquisition of optimal lytic competence by precursor cytotoxic T cells.

Antigens, CD↗
PubMed1990

Correlation between clinical response to interleukin 2 therapy and sustained production of tumor necrosis factor.

Twenty-five previously untreated patients with metastatic renal cell carcinoma were treated with 5-day cycles of continuous infusion of interleukin 2 (IL2) and lymphokine-activated killer cell reinfusion. Five achieved a partial response. Three patients were found to have detectable tumor necrosis factor (TNF) in serum before initiation of therapy. On the fifth day of therapy, 24 patients had circulating TNF with immunoradiometric assay whereas 13 had detectable biological activity. Two days after the end of IL2 therapy, TNF concentration (immunoradiometric assay) decreased in most cases but was still detectable in 17 patients. Thirteen patients had still circulating TNF bioactivity. Although there was no significant difference between TNF levels observed on the fifth day of therapy in the responder and nonresponder groups, 48 h after the end of IL2 infusion, both the TNF concentration and the biological activity were significantly higher in the group of responder patients. This result suggests that the clinical response to IL2 therapy in patients with metastatic renal cell carcinoma is correlated to a sustained production of TNF after the end of IL2 infusion.

Animals↗
PubMed1990

Functional interactions between interleukin-4, interleukin-2, and tumor necrosis factor-alpha for lymphokine-activated killer cell generation.

The purpose of the present study was to explore the interaction between interleukin-2 (IL-2), interleukin-4 (IL-4), and tumor necrosis factor-alpha (TNF) on the differentiation of human large granular lymphocytes (LGL) into lymphokine-activated killer cells (LAK). The data show that recombinant human IL-4 (100-1,000/ml) was able to induce the differentiation of human LGL into LAK effectors. The levels of the IL-4-induced cytotoxicity are significantly lower than those observed after stimulation of LGL by optimal doses of IL-2. This LAK activity generation by IL-4 was not associated with LGL proliferation. When TNF was added in LGL culture in the presence of suboptimal concentrations of IL-4, the lytic capacity of the activated killer cells was significantly enhanced, suggesting an apparent synergy between these two factors. Most interestingly, our data indicate that exogenous TNF can partially overcome the known inhibitory effect of IL-4 on IL-2-induced LGL differentiation into LAK effectors. These findings suggest a role for TNF in the process of LAK induction.

Cell Differentiation↗
PubMed1990

[Involvement of tumor necrosis factor in the generation of LAK killer cells].

The effect of Tumor Necrosis Factor (TNF) alpha on LAK generation was investigated. TNF was found to act synergistically with low concentrations of IL-2 (15 pM), which were ineffective by themselves to promote the differentiation of Large granular lymphocytes (LGL) into LAK effectors. The IL-2/TNF driven generation of LAK activity involves the induction of high affinity IL-2 receptors on LGL and occurs without promoting a significant proliferation, suggesting a functional activation rather than a proliferative expansion of LAK precursors. Our studies also indicate the existence of a correlation between the generation of LAK activity and the increase in TNF binding sites on LGL. Furthermore we demonstrate that the failure of low doses of IL-2 to induce LAK activity were related to their incapacity to induce TNF production by LGL and suggest that TNF alpha may be a physiologic mediator in the sequential activation stages of LGL into LAK effectors.

Cell Differentiation↗
PubMed1989

Functional interactions of IL2 and TNF in the differentiation of LGL into LAK effectors.

We have previously reported on the synergistic effect of IL2 and TNF on the differentiation of LGL into LAK effectors. In the present study, we have further investigated the molecular basis of this synergistic mechanism and examined the role of TNF in the induction of LAK activity. We show that the generation of optimal LAK activity by low doses of IL-2 in the presence of TNF involves the induction of high-affinity IL2 receptors on LGL and occurs without promoting significant proliferation, suggesting a functional activation rather than a proliferative expansion of LAK precursors. Using blocking studies with anti-Tac and with an anti-IL2 (IHII), which specifically inhibits the binding of IL2 to the p75 IL2 receptor component, we also show that both the p55 and the p75 are involved in the increase in TNF binding sites on LGL and the subsequent acquisition of LAK activity. We also demonstrate that the failure of low doses of IL2 to induce LAK activity is related to their incapacity to induce TNF production. Moreover, when specific antibodies against TNF were added to the culture, the differentiation of LGL into LAK effectors by optimal concentrations of IL2 in our system (2.5-5.0 ng/ml) was partially inhibited. This suggests that TNF may be a physiologic mediator in the sequential activation stages of LGL into LAK effectors.

Cell Differentiation↗
PubMed1989

The inhibitory effect of PGE2 on T cell activation is not associated with inhibition of PKC translocation.

We have recently reported on the effect of PGE2 on T cell activation and suggested that their immunosuppressive effect may involve the PKC activation pathway. In the present study, we further investigated the potential interference of PGE2 with PHA induced signaling in T lymphocytes. We demonstrate that the PHA mediated increase in IP3, the putative mobilizer of intracellular Ca2+, is slightly affected following cell incubation with PGE2. Treatment of cell culture with the tumor promoter TPA abrogates the suppressive activity of PGE2 whereas exogenous diacylglycerol (1,2-diolein) has only a marginal effect. This suggests that PGE2 affect PKC activity at sites distal to IP3 and DG generation. We also demonstrate that the PGE2 suppressive effect on T lymphocyte activation is not related to an inhibition of PKC translocation.

Cells, Cultured↗