Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It has been suggested that one means by which chemotherapeutic agents exert their effect on leukaemic cells, is via autocrine induction of fas-ligand which then binds to fas (CD95), activates the caspase pathway and results ultimately in apoptotic death. In order to test this hypothesis, we have treated leukaemic cell lines with various chemotherapeutic agents (idarubicin, etoposide, fludarabine and 2-CdA) with and without pre-treatment with fas (ZB4) and fas-ligand (NOK-1) blocking monoclonal antibodies. Cell cycle analysis and quantitation of apoptosis were performed by flow cytometry following propidium iodide staining. HL-60 cells were found to be sensitive to the induction of apoptosis with all drugs tested but were highly resistant to treatment with a fas-ligating antibody (CH11). Apoptosis was neither inhibited in parental CEM cells nor their mdr-expressing drug resistant counterpart, CEM/VLB100 by pre-treatment with either ZB4 or NOK1. In addition, CEM/VLB100 were slightly more sensitive to treatment with CH11 (100 ng/ml) than parental CEM cells (% age apoptosis = 30.35 and 23.675, p = 0.024) and at least as sensitive to recombinant fas-ligand (50 ng/ml) (% age apoptosis = 26.6 and 20.2, p = NS). We conclude that it is unlikely that fas/fas-ligand interactions play a significant role in the induction of apoptosis by these chemotherapeutic agents in the leukaemic cell lines tested.
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PMID:Inhibition of FAS/FAS-ligand does not block chemotherapy-induced apoptosis in drug sensitive and resistant cells. 1050 Aug 1

Primary cutaneous (PC) CD30-positive large cell lymphoma and lymphomatoid papulosis (LyP) represent the spectrum of PC CD30-positive lymphoproliferative disorders (LPDs) associated with a favorable prognosis. Noncutaneous CD30-positive anaplastic large cell lymphoma (ALCL), although morphologically similar to PC CD30-positive LPDs, seems to be a biologically distinct entity. Cell lines derived from noncutaneous ALCL express CD95 and undergo CD95-induced apoptosis. Little is known about expression or function of CD95/CD95L in cutaneous lesions. We examined a series of PC CD30-positive LPDs and noncutaneous ALCL for expression of CD95/CD95L to investigate possible differences between these histologically similar but biologically distinct entities. Paraffin-embedded, formalin-fixed tissue sections from 25 cases of CD30-positive LPDs (10 noncutaneous ALCL, 15 PC CD30-positive LPDs) were immunostained for CD3, CD20 (L26), CD43 (Leu22), CD30 (BerH2), anaplastic lymphoma kinase (ALK-1), CD95, and CD95L (C-33). One hundred large atypical cells and 100 small lymphocytes were counted to determine the percentage of CD95/ CD95L-positive cells. Statistical analysis using the Mann-Whitney U test was performed. CD95 expression was slightly higher in the large atypical cells of noncutaneous ALCL compared with PC CD30-positive LPDs (median, 100% versus 94%; P = .003) because of the lower expression of CD95 in LyP. CD95L expression was higher in the surrounding small lymphocytes in PC CD30-positive LPDs (median, 3% versus 13%; P = .002). Expression of CD95 in the small lymphocytes and CD95L in the large atypical cells was not significantly different. These results support the biologic distinction between cutaneous and noncutaneous CD30-positive LPDs and may have implications in the differing clinical behavior of these entities. Further study of expression and function of apoptosis-related proteins in these entities is warranted.
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PMID:Immunohistochemical analysis of CD30-positive lymphoproliferative disorders for expression of CD95 and CD95L. 1078 13

Cytotoxic T lymphocytes (CTLs) can kill target cells by the granule/exocytosis pathway or the Fas-mediated apoptosis pathway. The sensitivity of chronic lymphocytic leukemia (CLL) B cells to CTL-mediated apoptosis before and after CD40 activation was examined. Resting or CD40-activated CLL cells were found to be equally sensitive to class I-restricted CTL-mediated killing. Despite expressing CD95, the CD40-activated CLL target cells were found to be resistant to apoptosis induced by CH11, an IgM CD95 monoclonal antibody (mAb). Consistent with this, inhibitors of caspases, which are involved in the Fas-induced apoptotic pathway (eg, N-carbobenzoxy-Val-Ala-Asp fluoromethyl ketone [z-VAD-fmk]), were unable to block destruction of CLL target cells by CTL. In addition, preincubation of the effector T cells with the anti-Fas ligand mAb NOK-2 failed to inhibit their subsequent ability to kill CLL target cells. On the other hand, CTL activity was blocked by inhibitors of the granule exocytosis pathway such as ethylene-glyco-tetra-acetic acid or concanamycin A. These results indicate that CD40 activation does not impair the sensitivity of CLL cells to Fas-independent CTL-mediated apoptosis. (Blood. 2000;95:3853-3858)
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PMID:CD40 activation does not protect chronic lymphocytic leukemia B cells from apoptosis induced by cytotoxic T lymphocytes. 1084 20

When T cells are activated, the expression of the CD95 ligand is elevated, with the purpose of inducing apoptosis in target cells and to later eliminate the activated T cells. We have shown previously that mitogen-activated protein kinase (MAPK or ERK) signaling suppresses CD95-mediated apoptosis in different cellular systems. In this study we examined whether MAPK signaling controls the persistence and CD95-mediated termination of an immune response in activated T cells. Our results show that activation of Jurkat T cells through the T cell receptor immediately suppresses CD95-mediated apoptosis, and that this suppression is mediated by MAPK activation. During the phase of elevated MAPK activity, the activation of caspase-8 and Bid is inhibited, whereas the assembly of a functional death-inducing signaling complex (DISC) is not affected. These results explain the resistance to CD95 responses observed during the early phase of T cell activation and suggest that MAPK-activation deflects DISC signaling from activating caspase-8 and Bid. The physiological relevance of the results was confirmed in activated primary peripheral T cells, in which inhibition of MAPK signaling markedly sensitized the cells to CD95-mediated apoptosis.
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PMID:MAPK/ERK signaling in activated T cells inhibits CD95/Fas-mediated apoptosis downstream of DISC assembly. 1103 9

Human immunodeficiency virus-type 1 (HIV-1) infection is characterized by increased immune cell apoptosis. Apoptosis can be triggered by signals that arise from within the cell, or by signals that are elicited by binding of extracellular "death ligands" to their "death receptors," most of which belong to the tumor necrosis factor (TNF)-receptor family, such as CD95 (Fas/Apo-1). In immune cells the oligomerization of CD95, induced by its ligand CD95L, and the recruitment of different intracytoplasmic molecules that in turn activate FLICE/caspase 8 are crucial. To study the role of CD95/CD95L interactions during HIV-1 infection, we developed an original method based upon quantitative-competitive (QC) RT-PCR that allowed us to quantify the amounts of mRNA coding for the total (tCD95) and membrane (mCD95) forms of CD95. We first studied the expression of different forms of CD95 mRNA in a classical model of chronic HIV infection using two infected cell lines of different origin--lymphocytic (ACH-2) or monocytic (U1). We have shown that infected cells of monocytic origin preferentially produce the "protective" (soluble) form of CD95, and no detectable CD95L mRNA, while lymphoid cells produce more mRNA for the membrane form of CD95 (which triggers apoptosis) along with low but detectable amounts of CD95L mRNA. One can hypothesize that a complex balance exists between pro-apoptotic events, perhaps triggered by the host to limit viral production, and anti-apoptotic events likely triggered by the virus to increase its production and survival. In cells of monocytic origin, which act as a reservoir for the virus, the anti-apoptotic molecules are favored; in cells of lymphocytic origin, molecules with an apoptotic meaning are prevalent.
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PMID:Quantitation of CD95 and CD95L mRNA expression in chronic and acute HIV-1 infection by competitive RT-PCR. 1119 40

In recent years, some studies on the expression of CD95(Fas/APO-1) ligand (CD95L) in tissues or cells raised concerns about the specificity of the antibodies used. We therefore tested 12 CD95L antibodies for their reliability in immunocyto/histochemistry by (i) staining CD95L-transfected and control CV-1/EBNA cells and (ii) comparing staining patterns in immunohistochemically labeled tissue sections with the localization of CD95L+ cells in in situ hybridization. While G247-4, NOK-1, NOK-2, 4H9, and MIKE-1 stained CD95L-transfected cells and did not significantly bind to controls, G247-4 was the only antibody giving satisfying signals in tissue sections perfectly matching the distribution of CD95L+ cells by in situ hybridization. MAb 33, C-20, and N-20 comparably stained both transfected and control cells and showed considerable background or falsely positive staining in sections. MIKE-2, 8B8, A11, and 4A5 did not or only very faintly bind to either cells and, thus, were not tested on sections. We conclude that G247-4 is the only tested antibody that is recommendable for immunohistochemistry.
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PMID:CD95 ligand (CD95L) immunohistochemistry: a critical study on 12 antibodies. 1131 10

RRR-alpha-tocopherol succinate (vitamin E succinate, VES) is a potent, selective apoptotic agent for cancer cells but not normal cells. VES has been shown to inhibit the growth of a wide variety of tumor cells in cell culture and animal models. Studies addressing mechanisms of action of VES-induced apoptosis have identified transforming growth factor-beta, Fas/CD95-APO-1, and mitogen-activated protein kinase (MAPK) signaling pathway involvement. Here we show that MAPKs, the extracellular signal-regulated kinases (ERK), and the stress-activated protein kinases, c-Jun NH2-terminal kinases (JNK), but not p38, are critical mediators in VES-induced apoptosis of human breast cancer MDA-MB-435 cells. VES activates ERK1/2 and JNK both in level and duration of kinase activity. Expression of dominant negative mutants of ERK1, MAPK/ERK activator-1, or JNK1 but not p38 blocked phosphorylation of the substrate glutathione S-transferase-c-Jun and inhibited VES-induced apoptosis. Increased phosphorylation and transactivation activity of nuclear transcription factors c-Jun, ATF-2, and Elk-1 are observed after VES treatments; however, only c-Jun and ATF-2 appear to be involved in VES-induced apoptosis based on antisense blockage experiments. Collectively, these results imply a critical role for ERK1 and JNK1 but not p38 in VES-induced apoptosis of human MDA-MB-435 breast cancer cells.
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PMID:Activation of extracellular signal-regulated kinase and c-Jun-NH(2)-terminal kinase but not p38 mitogen-activated protein kinases is required for RRR-alpha-tocopheryl succinate-induced apoptosis of human breast cancer cells. 1152 56

Stimulation of CD95 leads to oligomerization of this receptor and the recruitment of the Fas-associated death domain (FADD) and procaspase-8 to form the death-inducing signaling complex (DISC). Subsequent proteolytic activation of caspase-8 at the DISC leads to the activation of downstream caspases and execution of apoptosis. The anticancer drug 9-nitrocamptothecin (9NC) inhibits the nuclear enzyme topoisomerase I (Top1), an event followed by apoptosis of cancer cells. We investigated whether other mechanisms downstream of the DNA-Top1-9NC complexing step regulate the apoptotic ability of 9NC in DU145 cells. We demonstrate that induction of apoptosis in DU145 cells, upon exposure to 9NC, is associated with de novo expression of CD95 and CD95L, suggesting that 9NC-induced apoptosis is mediated by the CD95 system. In this line, we observed early activation of procaspase-3, -7, and -8, but not -1, -9, and -10. Moreover, 9NC treatment resulted in the dramatic down-regulation of c-FLIP(short) expression, but not that of c-FLIP(long) or FADD. Furthermore, incubation of DU145 cells with a neutralizing antibody (NOK-1) to CD95L or transient transfection of a c-FLIP(short) expression vector into DU145 cells partially abrogated 9NC-triggered apoptosis. We propose that 9NC triggers apoptosis by driving DU145 cells from a nonapoptotic status (c-FLIP(short)(high), CD95(low), CD95L(low)) toward a proapoptotic status (c-FLIP(short)(low), CD95(high), CD95L(high)). These findings indicate that in addition to a Top1-mediated effect, 9NC can additionally activate a CD95/CD95L-dependent apoptotic pathway.
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PMID:Induction of apoptosis in 9-nitrocamptothecin-treated DU145 human prostate carcinoma cells correlates with de novo synthesis of CD95 and CD95 ligand and down-regulation of c-FLIP(short). 1158 48

Anticancer treatment using cytotoxic drugs is considered to mediate cell death by activating key elements of the apoptosis program and the cellular stress response. While proteolytic enzymes (caspases) serve as main effectors of apoptosis, the mechanisms involved in activation of the caspase system are less clear. Two distinct pathways upstream of the caspase cascade have been identified. Death receptors, eg, CD95 (APO-1/Fas), trigger caspase-8, and mitochondria release apoptogenic factors (cytochrome c, Apaf-1, AIF), leading to the activation of caspase-9. The stressed endoplasmic reticulum (ER) contributes to apoptosis by the unfolded protein response pathway, which induces ER chaperones, and by the ER overload response pathway, which produces cytokines via nuclear factor-kappaB. Multiple other stress-inducible molecules, such as p53, JNK, AP-1, NF-kappaB, PKC/MAPK/ERK, and members of the sphingomyelin pathway have a profound influence on apoptosis. Understanding the complex interaction between different cellular programs provides insights into sensitivity or resistance of tumor cells and identifies molecular targets for rational therapeutic intervention strategies.
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PMID:Cellular stress response and apoptosis in cancer therapy. 1167 28

The death ligands CD95L and Apo2L/TRAIL are promising investigational agents for the treatment of malignant glioma. EGFR is overexpressed in a significant proportion of malignant gliomas in vivo. Here, we report that CD95L-induced cell death is enhanced by EGFR inhibition using tyrphostine AG1478 in 7 of 12 human malignant glioma cell lines. Conversely, CD95-mediated and Apo2L-induced cell death are both inhibited by overexpression of EGFR in LN-229 cells. CD95L-induced cell death augmented by AG1478 is accompanied by enhanced processing of caspase 8. LN-229 cells overexpressing the viral caspase inhibitor, crm-A, are not sensitized to CD95L-induced cell death by AG1478, indicating that EGFR exerts its antiapoptotic properties through a caspase 8-dependent pathway. These data define a modulatory effect of EGFR-activity on death ligand-induced apoptosis and indicate that EGFR inhibition is likely to improve the efficacy of death ligand-based cancer therapies. Furthermore, it is tempting to speculate that EGFR amplification protects tumor cells from death ligand-mediated host immune responses in vivo and that EGFR's effects on death receptor-mediated apoptosis may explain the anti-tumor effects of non-cytotoxic, unarmed anti-EGFR family antibodies.
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PMID:CD95-mediated apoptosis of human glioma cells: modulation by epidermal growth factor receptor activity. 1177 Aug 95


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