Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.22.61 (caspase-8)
 6,833 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Brief periods of in vitro hypoxia/ischemia induce apoptosis of cultured renal epithelial cells, but the underlying mechanisms remain unknown. We show that partial ATP depletion (approximately 10-65% of control) results in a duration-dependent induction of apoptosis in Madin-Darby canine kidney (MDCK) cells, as evidenced by internucleosomal DNA cleavage (DNA laddering and in situ nick end labeling), morphological changes (cell shrinkage), and plasma membrane alterations (externalization of phosphatidylserine). The ATP-depleted cells display a significant upregulation of Fas, Fas ligand, and the Fas-associating protein with death domain (FADD). Exogenous application of stimulatory Fas monoclonal antibodies also induces apoptosis in nonischemic MDCK cells, indicating that they retain Fas-dependent pathways of programmed cell death. Furthermore, cleavage of poly(ADP)ribose polymerase (PARP) is evident after ATP depletion, indicating activation of caspases. Indeed, the apoptotic cells display a significant increase in caspase-8 (FLICE) activity. Finally, apoptosis induced by ATP depletion is ameliorated by pretreatment with inhibitors of caspase-8 (IETD), caspase-1 (YVAD), or caspase-3 (DEVD) but is not affected by inhibitors of serine proteases (TPCK). Our results indicate that partial ATP depletion of MDCK cells results in apoptosis and that Fas- and caspase-mediated pathways may play a critical role.
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PMID:Partial ATP depletion induces Fas- and caspase-mediated apoptosis in MDCK cells. 1036 72

Transduction of cancer cells with herpes simplex virus thymidine kinase gene (HSVtk) followed by prodrug ganciclovir (GCV) treatment has been shown to induce apoptosis. In this study, four murine tumors including B16F10 melanoma, NG4TL4 sarcoma, H6 hepatoma and 1MEA 7R.1 hepatoma were found to vary in sensitivity to this gene therapy strategy in vitro but, at effective doses of GCV, the HSVtk-transduced cells of all four tumors showed similar kinetics of early rise in p53 protein levels, then cell cycle S-/G2-phase arrest and finally signs of apoptosis. Immunoblot analyses revealed that Fas (CD95/APO-1), Fas ligand (FasL) and two downstream mediators, RIP and caspase-3, (CPP32, YAMA, Apopain) were increased in GCV-treated HSVtk-transduced tumor cells the cell cycle arrest and before apoptosis. Increased expression of FasL could also be observed in vivo in HSVtk-transduced tumors induced to regress by GCV treatment. Enzyme measurements using specific substrate showed that the caspase-3 activation followed kinetically the FasL expression. More than half of the HSVtk/GCV-induced cell death could be abrogated by addition to the cell culture medium of a specific antisense oligonucleotide to block FasL synthesis, a recombinant Fas/Fc chimeric protein to compete with Fas receptor for FasL binding, or cell-permeable specific tetrapeptide inhibitors of caspase-3 or caspase-8.
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PMID:Involvement of Fas (CD95/APO-1) and Fas ligand in apoptosis induced by ganciclovir treatment of tumor cells transduced with herpes simplex virus thymidine kinase. 1043 92

Transforming growth factor-beta1 (TGF-beta1) has been shown to induce apoptosis in normal or transformed hepatocytes. To elucidate the biochemical pathways leading to apoptosis induced by TGF-beta1 in human hepatoma cells (HuH-7), we examined the expression of Bcl-2-related proteins and X-chromosome-linked inhibitor of apoptosis (XIAP), and activation of the caspase cascade following TGF-beta1 treatment. Bcl-xL expression began to decline at 12 hours after TGF-beta1 treatment and progressively decreased to very low levels in a time-dependent manner. Bax expression showed a little change throughout the experiment. On the other hand, activation of caspase-8 was clearly observed at 36 hours after TGF-beta1 treatment, followed by activation of caspase-9, and caspase-3 was activated at 48 hours after treatment at which time apoptosis of HuH-7 cells was observed. TGF-beta1 significantly decreased XIAP expression in HuH-7 cells. Addition of an inhibitor of caspase-8 or caspase-3 (IETD-FMK or DEVD-CHO) markedly inhibited TGF-beta1-induced apoptosis of HuH-7 cells. Fas/Fas ligand (FasL) interactions in HuH-7 cells were not involved in the apoptotic process. Furthermore, epidermal growth factor (EGF) also completely inhibited TGF-beta1-induced apoptosis of HuH-7 cells by inhibiting activation of the caspase cascade. Our results suggested that activation of caspase-3 initiated through caspase-8 activation is involved in the apoptotic process induced by TGF-beta1 in HuH-7 cells. Our results also showed that down-regulation of the expression of Bcl-xL and XIAP by TGF-beta1 may facilitate activation of caspase-3 in these cells.
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PMID:Activation of caspase-8 in transforming growth factor-beta-induced apoptosis of human hepatoma cells. 1053 43

Deletion of activated peripheral T cell clones by apoptosis requires the regulated expression of Fas ligand (FasL) and sensitization of these cells to CD95-mediated signaling. To investigate the signaling pathways responsible for FasL expression in T cells, we tested-besides subfamily-selective protein kinase C (PKC) inhibitors - the effect of constitutively active mutants of representatives of all PKC subfamilies, i.e. PKCalpha,epsilon,theta,iota, on FasL luciferase promoter reporter constructs. In synergy with a constitutively active form of protein phosphatase 2B calcineurin (CaN), only PKCtheta, but not PKCalpha,epsilon,iota, preferentially induced FasL promoter reporter activity and, consequently, FasL protein expression in Jurkat T cells. Activation of an inducible PKCtheta AE-estrogen receptor fusion mutant led to a CaN-dependent and rapid FasL reporter activity detected as early as 4 h after addition of 4-hydroxytamoxifen, incidating a direct effect of PKCtheta action on FasL expression. Consistently, in Jurkat T cells, expression of PKCtheta AE / CaN significantly enhanced FasL protein expression and apoptosis in a CD95-dependent manner since cell death was not observed in T cells co-expressing the caspase-8 inhibitor crmA. Taken together, our results support the notion that PKCtheta and CaN are sufficient to regulate apoptosis through FasL expression.
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PMID:Synergistic action of protein kinase C theta and calcineurin is sufficient for Fas ligand expression and induction of a crmA-sensitive apoptosis pathway in Jurkat T cells. 1055 9

alpha-Fetoprotein (AFP) is an oncoembryonal protein with multiple cell growth regulating, differentiating and immunosuppressive activities. Previous studies have shown that treatment of tumor cells in vitro with 1-10 microM AFP produces significant suppression of tumor cell growth by inducing dose-dependent cytotoxicity, but the molecular mechanisms underlying these AFP functions are obscure. Here, we show that AFP cytotoxicity is closely related to apoptosis, as shown by cell morphology, nuclear DNA fragmentation and caspase-3-like activity resulting in cleavage of poly(ADP-ribose) polymerase. Apoptosis was significantly inhibited by a CPP32 family protease inhibitor whereas a general caspase inhibitor had no inhibitory effect, showing some enhancement of AFP-mediated cell death. Using fluorogenic caspase substrates, we found that caspase-3-like proteases were activated as early as 4 h after treatment of Raji cells with 15 microM AFP, whereas caspase-1, caspase-8, and caspase-9-like activity was not detected during the time interval 0.5-17 h. AFP treatment of Raji cells increased Bcl-2 protein, showing that AFP-induced apoptosis is not explained by downregulation of the Bcl-2 gene. This also suggests that AFP operates downstream of the Bcl-2-sensitive step. AFP notably decreased basal levels of soluble and membrane-bound Fas ligand. Incubation of AFP-sensitive tumor cells (HepG2, Raji) with neutralizing anti-Fas, anti-tumor necrosis factor receptor (TNFR)1 or anti-TNFR2 mAb did not prevent AFP-induced apoptosis, demonstrating its independence of Fas-dependent and TNFR-dependent signaling. In addition, it was found that cells resistant to TNF-induced (Raji) or Fas-induced (MCF-7) apoptosis are, nevertheless, sensitive to AFP-mediated cell death. In contrast, cells sensitive to Fas-mediated cell death (Jurkat) are completely resistant to AFP. Taken as a whole, our data demonstrate that: (a) AFP induces apoptosis in tumor cells independently of Fas/Fas ligand or TNFR/TNF signaling pathways, and (b) AFP-mediated cell death involves activation of the effector caspase-3-like proteases, but is independent of upstream activation of the initiator caspase-1, caspase-8, and caspase-9-like proteases.
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PMID:alpha-fetoprotein causes apoptosis in tumor cells via a pathway independent of CD95, TNFR1 and TNFR2 through activation of caspase-3-like proteases. 1058 68

The mechanism of apoptosis induced by 2-chloro-2'-deoxyadenosine (2CdA) in human leukemia cell line MOLT-4 was investigated. 2CdA induced increases of 3'-OH ends of genomic DNA, ladder-like DNA fragmentation and phosphatidylserine translocation to the outer membrane, which are apoptotic characteristics. These apoptotic phenomena induced by 2CdA were inhibited by cycloheximide (CHX; a protein synthesis inhibitor), deoxycytidine (dC; a substrate of deoxycytidine kinase), acetyl Ile-Glu-Thr-Asp aldehyde (Ac-IETD-CHO; a caspase-8 inhibitor) and acetyl Asp-Glu-Val-Asp aldehyde (Ac-DEVD-CHO; a caspase-3 inhibitor). The protein synthesis-dependent expression of Fas and Fas ligand (Fas-L) was detected by treatment with 2CdA. The proteolytic processing of procaspases-8 and -3 to produce active fragments, caspases-8 (p18) and -3 (p17), respectively, was observed after treatment with 2CdA, and suppressed by cycloheximide. Increases in the activities of caspases-8 and -3 were observed after 2CdA treatment. Their activation was also dependent on protein synthesis. These results indicated that 2CdA-induced apoptosis was triggered by phosphorylation of 2CdA followed by the protein synthesis-dependent expression of Fas and Fas-L and activation of caspases-8 and -3.
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PMID:2-Chloro-2'-deoxyadenosine induces apoptosis through the Fas/Fas ligand pathway in human leukemia cell line MOLT-4. 1067 48

Our recent studies suggest that human squamous cell carcinoma of the head and neck (SCCHN) is capable of activating an intrinsic mechanism of programmed-cell death in interacting lymphocytes in situ and in vitro. The current study used Jurkat T-cell line as a model to investigate intracellular apoptotic events in T cells interacting with SCCHN. Apoptosis induced in T lymphocytes by tumor cells was in part Fas-mediated, since it was partially, but significantly, inhibited in the presence of anti-Fas ligand Ab or in Fas-resistant Jurkat cells. The synthetic caspase inhibitors, N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (Z-VAD-FMK) and N-benzyloxycarbonyl-Asp-glu-Val-Asp-fluoromethyl ketone (Z-DEVD-FMK), effectively blocked apoptosis of Jurkat cells co-incubated with SCCHN cell lines, suggesting the involvement of caspases in tumor-induced apoptosis of lymphocytes. Overexpression of CrmA, an inhibitor of caspase-1 and caspase-8, partially inhibited tumor-induced T-cell death. Caspase-8 and caspase-3 were identified as effector molecules in the execution of tumor-induced T-cell death, since the proform enzymes were processed into active subunits during co-incubation of T cells with tumor cells. Furthermore, co-incubation with tumor cells resulted in cleavage of poly(ADP-ribose) polymerase (PARP), a common caspase-3 substrate, and in cleavage of TcR-zeta chain, shown by us to be a T-cell specific caspase-3 substrate. Overexpression of Bcl-2 did not provide protection of T cells from SCCHN-induced DNA degradation. Instead, the Bcl-2 protein was cleaved in the target T cells during their co-incubation with tumor cells. These findings demonstrate that tumor cells can trigger in T lymphocytes caspase-dependent apoptotic cascades, which are not effectively protected by Bcl-2. (Blood. 2000;95:2015-2023)
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PMID:Tumor-induced apoptosis of T lymphocytes: elucidation of intracellular apoptotic events. 1070 69

Cytotoxic endoribonucleases (RNases) possess a potential for use in cancer therapy. However, the molecular determinants of RNase-induced cell death are not well understood. In this work, we identify such determinants of the cytotoxicity induced by onconase, an amphibian cytotoxic RNase. Onconase displayed a remarkable specificity for tRNA in vivo, leaving rRNA and mRNA apparently undamaged. Onconase-treated cells displayed apoptosis-associated cell blebbing, nuclear pyknosis and fragmentation (karyorrhexis), DNA fragmentation, and activation of caspase-3-like activity. The cytotoxic action of onconase correlated with inhibition of protein synthesis; however, we present evidence for the existence of a mechanism of onconase-induced apoptosis that is independent of inhibition of protein synthesis. The caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp(OMe) fluoromethyl ketone (zVADfmk), at concentrations that completely prevent apoptosis and caspase activation induced by ligation of the death receptor Fas, had only a partial protective effect on onconase-induced cell death. The proapoptotic activity of the p53 tumor suppressor protein and the Fas ligand/Fas/Fas-associating protein with death domain (FADD)/caspase-8 proapoptotic cascade were not required for onconase-induced apoptosis. Procaspases-9, -3, and -7 were processed in onconase-treated cells, suggesting the involvement of the mitochondrial apoptotic machinery in onconase-induced apoptosis. However, the onconase-induced activation of the caspase-9/caspase-3 cascade correlated with atypically little release of cytochrome c from mitochondria. In turn, the low levels of cytochrome c released from mitochondria correlated with a lack of detectable translocation of proapoptotic Bax from the cytosol onto mitochondria in response to onconase. This suggests the possibility of involvement of a different, potentially Bax- and cytochrome c-independent mechanism of caspase-9 activation in onconase-treated cells. As one possible mechanism, we demonstrate that procaspase-9 is released from mitochondria in onconase-treated cells. A detailed understanding of the molecular determinants of the cytotoxic action of onconase could provide means of positive or negative therapeutic modulation of the activity of this potent anticancer agent.
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PMID:Molecular determinants of apoptosis induced by the cytotoxic ribonuclease onconase: evidence for cytotoxic mechanisms different from inhibition of protein synthesis. 1076 89

Paclitaxel (Taxol) kills tumor cells by inducing both cellular necrosis and apoptosis. A major impediment to paclitaxel cytotoxicity is the establishment of multidrug resistance whereby exposure to one chemotherapeutic agent results in cross-resistance to a wide variety of other drugs. For example, selection of MCF-7 breast cancer cells for resistance to doxorubicin (MCF-7ADR cells) results in cross-resistance to paclitaxel. This appears to involve the overexpression of the drug transporter P-glycoprotein which can efflux both drugs from tumor cells. However, MCF-7ADR cells possess a deletion mutation in p53 and have considerably reduced levels of the Fas receptor, Fas ligand, caspase-2, caspase-6, and caspase-8, suggesting that paclitaxel resistance may also stem from a bona fide block in paclitaxel-induced apoptosis in these cells. To address this issue, we examined the ability of the P-glycoprotein inhibitor valspodar to restore paclitaxel accumulation, paclitaxel cytotoxicity, and paclitaxel-induced apoptosis. Compared to drug sensitive MCF-7 cells, MCF-7ADR cells accumulated >6-fold less paclitaxel, were approximately 100-fold more resistant to killing by the drug, and were highly resistant to paclitaxel-induced apoptosis. In contrast, MCF-7ADR cells pretreated with valspodar were indistinguishable from drug-sensitive cells in their ability to accumulate paclitaxel, in their chemosensitivity to the drug, and in their ability to undergo paclitaxel-induced apoptosis. Valspodar, by itself, did not affect these parameters. This suggests that the enhancement of paclitaxel toxicity in MCF-7ADR cells involves a restoration of apoptosis and not solely through enhanced drug-induced necrosis. Morever, it appears that changes in the levels/activity of p53, the Fas receptor, Fas ligand, caspase-2, caspase-6, or caspase-8 activity have little effect on paclitaxel-induced cytotoxicity and apoptosis in human breast cancer cells.
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PMID:Role of specific apoptotic pathways in the restoration of paclitaxel-induced apoptosis by valspodar in doxorubicin-resistant MCF-7 breast cancer cells. 1083 93

Fas/Fas ligand (FasL) is well known for its role in delivering apoptotic signals; however, it is unclear whether FasL can mediate apoptosis in cardiomyocytes. We hypothesized that apoptosis via Fas/FasL system may be augmented in damaged cardiomyocytes. To determine whether FasL mediates cardiomyocyte apoptosis, recombinant FasL (rFasL) was added to the culture of neonatal rat ventricular myocytes pretreated with and without doxorubicin. Without doxorubicin, high dose of rFasL caused an increase in TUNEL-positive cardiomyocytes and a mild decrease in MTT activities. When cardiomyocytes were pretreated with doxorubicin (0.5 microM), rFasL dramatically augmented TUNEL-positive cardiomyocytes in a concentration-dependent manner, which was accompanied with nuclear fragmentations. The rFasL also caused a concentration-dependent reduction in MTT activities in cardiomyocytes. The rFasL-induced caspase-8 activity was greatly facilitated by pretreatment of doxorubicin. TUNEL-positive nuclei with rFasL was inhibited by Fas-Fc, neutralizing agent of rFasL, and Z-IETD-FMK, caspase-8 inhibitor. Fas mRNA transcript by RT-PCR was up-regulated in cardiomyocytes with doxorubicin. We conclude that FasL can induce cardiomyocyte apoptosis particularly when cardiomyocyte becomes susceptible for Fas-mediated apoptosis.
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PMID:Apoptosis in rat cardiac myocytes induced by Fas ligand: priming for Fas-mediated apoptosis with doxorubicin. 1088 43


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