Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.22.56 (caspase-3)
 35,750 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The IAP (inhibitor of apoptosis) family of anti-apoptotic proteins regulates programmed cell death. Of the six known human IAP-related proteins, XIAP is the most potent inhibitor. To study the mechanistic effects of XIAP on DNA damage-induced apoptosis, we prepared U-937 cells that stably overexpress XIAP. The results demonstrate that XIAP inhibits apoptosis induced by 1-[beta-d-arabinofuranosyl]cytosine (ara-C) and other genotoxic agents. XIAP had no detectable effect on ara-C-induced release of mitochondrial cytochrome c and attenuated cleavage of procaspase-9. In addition, we show that ara-C induces the association of XIAP with the cleaved fragments of caspase-9 and thereby inhibition of caspase-9 activity. The results also demonstrate that ara-C induces cleavage of procaspase-3 by a caspase-8-dependent mechanism and that XIAP inhibits caspase-3 activity. These results demonstrate that XIAP functions downstream of procaspase-9 cleavage as an inhibitor of both proteolytically processed caspase-9 and -3 in the cellular response to genotoxic stress.
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PMID:XIAP regulates DNA damage-induced apoptosis downstream of caspase-9 cleavage. 1093 Apr 19

Antileukemic interactions between the nucleoside analog 1-beta-D-arabinofuranosylcytosine (ara-C) and the kinase inhibitor 7-hydroxystaurosporine (UCN-01) have been examined in relation to Bcl-2 expression/phosphorylation, mitochondrial damage, caspase activation, and loss of clonogenic potential. Subsequent exposure of ara-C-pretreated U937 cells (1 microM; 6 hr) to UCN-01 (300 nM; 24 hr) resulted in marked potentiation of pro-caspase-3 and -9 cleavage/activation, poly(ADP-ribose)polymerase degradation, diminished mitochondrial membrane potential (Deltapsi(m)), enhanced cytochrome c release, reduction in the S-phase fraction, and induction of classic apoptotic morphologic features. Enforced expression of full-length Bcl-2 significantly protected cells (at 24 hr) from ara-C/UCN-01-induced caspase activation and apoptosis, but was ineffective in preventing loss of Deltapsi(m) and cytochrome c release. Ectopic expression of a Bcl-2 N-terminal phosphorylation loop-deleted protein (Bcl-2Delta(32-80)) was more potent than its full-length counterpart in blocking drug-induced loss of Deltapsi(m, ) caspase activation, and apoptotic morphology, but not cytochrome c release. Examination of cells at later intervals revealed that ectopic expression of Bcl-2 or Bcl-2Delta(32-80) could only delay, but not prevent, mitochondrial damage, caspase activation, and cell death induced by ara-C/UCN-01 treatment. Despite their initial ability to inhibit apoptosis, neither full-length nor truncated Bcl-2 protein restored clonogenic potential to drug-treated cells. These findings indicate that subsequent exposure of ara-C-pretreated human leukemia cells to UCN-01 potently triggers mitochondrial damage and apoptosis, and that these events are postponed but not prevented by ectopic expression of Bcl-2 or its phosphorylation loop-deleted counterpart.
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PMID:Potentiation of 1-beta-D-arabinofuranosylcytosine-mediated mitochondrial damage and apoptosis in human leukemia cells (U937) overexpressing bcl-2 by the kinase inhibitor 7-hydroxystaurosporine (UCN-01). 1102 Apr 46

The response of myeloid leukemia cells to treatment with 1-beta-D-arabinofuranosylcytosine (ara-C) includes activation of the c-Abl protein tyrosine kinase and the stress-activated protein kinase (SAPK). The present studies demonstrate that treatment of human U-937 leukemia cells with ara-C is associated with translocation of SAPK to mitochondria. STI571 (imatinib mesylate), an inhibitor of c-Abl, blocked both activation and mitochondrial targeting of SAPK in the ara-C response. In concert with these effects of STI571, similar findings were obtained in c-Abl-deficient cells. The results further show that STI571 inhibits ara-C-induced loss of mitochondrial transmembrane potential, caspase-3 activation, and apoptosis. These findings demonstrate that STI571 down-regulates c-Abl-mediated signals that target the mitochondria in the apoptotic response to ara-C.
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PMID:Inhibition of c-Abl with STI571 attenuates stress-activated protein kinase activation and apoptosis in the cellular response to 1-beta-D-arabinofuranosylcytosine. 1202 10

Up-regulation of Bcl-2 protein may contribute to drug resistance, by decreasing apoptosis after treatment, in pre-B and B-cell leukemias in pediatric patients. By contrast, augmented caspase-3 activity, an effector caspase, may be indicative of drug sensitivity due to increased cellular apoptosis. We have reported the development of an in vitro human T-lymphoblastic leukemia model resistant to ara-C and/or native E. coli L-asparaginase (ASNase), mimicking the drug resistance to the Capizzi II regimen. We have investigated the potential drug synergism between Idarubicin (IDA) and Taxotere (TXR) that may be active in the ara-C and ASNase double drug-resistant cell lines. The additive or synergistic activity between IDA and TXR is drug concentration-dependent in inducing caspase-3 activation and cellular apoptosis. We exposed two human drug-resistant cell lines that do not express the MDRI phenotype, one resistant to ASNase alone (CEM/ASNase-1-3) and the other resistant to both ara-C and ASNase (CEM/ara-C/I/ASNase-0.5-2), to physiologically achievable concentrations of IDA, TXR, or their combination. Both lines showed either synergistic drug activity to the combination regimen in comparison to either drug used alone, as determined by MTT assay, or additivity as demonstrated by flow cytometry after Annexin V and propidium iodide (PI) staining. After exposure of the ASNase-resistant line to various concentrations, the intracellular levels of Bcl-2 protein decreased to near zero relative to untreated control cells. The Bcl-2 protein reductions in these cells ranged from 30% to <1%, 49% to <1%, and 27% to 3% when treated with IDA or TXR as a single drug or IDA + TXR combination, respectively. Similarly, intracellular Bcl-2 levels in the double-resistant cell line decreased with reductions ranging from 24% to <1%, 87% to <1%, and 46% to <1% of the untreated control after treatment with IDA, TXR, or their combination, respectively. Conversely, the caspase-3 activity increased in a dose-dependent manner and inversely-correlated with loss of cell viability (r= 0.91) after exposure to IDA + TXR combination in the double drug-resistant line to both ara-C and ASNase. We conclude that the combination of the IDA + TXR regimen is highly synergistic or additive in drug resistant human leukemic cell clones. The molecular mechanism of action is due to the down-regulation of Bcl-2 protein and up-regulation of caspase-3 activity. This drug combination warrants further investigation for use in the treatment of patients with ara-C and/or ASNase refractory leukemias.
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PMID:The combination regimen of idarubicin and taxotere is effective against human drug-resistant leukemic cell lines. 1216 12

Responses to the CDK inhibitor flavopiridol (FP) have been examined in U937 leukemia cells ectopically expressing full-length Bcl-2 or an N-terminal phosphorylation loop-deleted protein (Bcl-2). A 3-fold increase in full-length Bcl-2 protein conferred substantial resistance to ara-C-associated lethality, but not to FP-mediated cytochrome c release, caspase-3 and-9 activation and apoptosis. In a second clonal line, a 6-fold increase in Bcl-2 expression delayed but did not ultimately prevent FP-associated apoptosis. In marked contrast, cells ectopically expressing the Bcl-2 loop-deleted protein (32-80) were highly resistant to FP-mediated cytochrome c release, caspase-3, -8, and -9 activation, Bid and PARP cleavage, and apoptosis despite relatively low levels of protein expression. The loop-deleted Bcl-2, but not full-length Bcl-2 protein also protected clonogenic cells from FP-mediated lethality. Finally, in Bcl-2-overexpressing cells, FP lethality was not attenuated by the caspase-8 inhibitor IETD-FMK, arguing against a role for the extrinsic, receptor-mediated pathway in circumventing Bcl-2-associated resistance. Collectively, these findings indicate that FP induces cytochrome c release in leukemic cells despite overexpression of Bcl-2, and suggest that this event may be modulated by negative regulatory factors residing within the N-terminal phosphorylation loop region.
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PMID:Loss of the Bcl-2 phosphorylation loop domain is required to protect human myeloid leukemia cells from flavopiridol-mediated mitochondrial damage and apoptosis. 1217 Jul 73

Cytosine arabinoside (ara-C) is a nucleoside analog used in the treatment of hematologic malignancies. One of the major side effects of ara-C chemotherapy is neurotoxicity. In this study, we have further characterized the cell death induced by ara-C in sympathetic neurons. Similar to neurons undergoing trophic factor deprivation-induced apoptosis, ara-C-exposed neurons became hypometabolic before death and upregulated c-myb, c-fos, and Bim. Bax deletion delayed, but did not prevent, ara-C toxicity. Neurons died by apoptosis, indicated by the release of mitochondrial cytochrome-c and caspase-3 activation. p53-deficient neurons demonstrated decreased sensitivity to ara-C, but neither p53 nor multiple p53-regulated genes were induced. Mature neurons showed increased ara-C resistance. These results demonstrate that molecular mechanisms underlying ara-C-induced death are similar to those responsible for trophic factor deprivation-induced apoptosis. However, substantial differences in neuronal death after these two distinct stress stimuli exist since ara-C toxicity, unlike the developmental death, can proceed in the absence of Bax.
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PMID:Cytosine arabinoside rapidly activates Bax-dependent apoptosis and a delayed Bax-independent death pathway in sympathetic neurons. 1293 79

Functional inducible NOS (iNOS) may be involved in the prolonged lifespan of chronic lymphocytic leukemia cells (B-CLL), although the exact mechanisms implicated remain elusive as yet. In this work, we have examined iNOS expression in normal B lymphocytes and B-CLL cells in pro- and antiapoptotic conditions. Our results demonstrate: (1) The existence of a new splice variant characterized by a complete deletion of exon 14 (iNOS 13-16(14del)), which was preferentially detected in normal B lymphocytes and may represent an isoform that could play a role in the regulation of enzyme activity. (2) The existence of another alternatively spliced iNOS mRNA transcript involving a partial deletion of the flavodoxin region (iNOS 13-16(neg)) was correlated to a decreased B-CLL cell viability. The 9-beta-D-arabinofuranosyl-2-fluoradenine or fludarabine (F-ara) treatment induced iNOS 13-16(neg) transcript variants, whereas IL-4 enhanced both the transcription of variants, including these exons (iNOS 13-16(pos)), and the expression of a 122 kDa iNOS protein. These results suggest that in B-CLL, a regulation process involving nitric oxide (.- NO) levels could occur by a post-transcriptional mechanism mediated by soluble factors. Our results also provide an insight into a new complementary proapoptotic action of F-ara in B-CLL by the induction of particular iNOS splice variants, leading to the activation of a caspase-3-dependent apoptotic pathway.
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PMID:Post-transcriptional regulation of inducible nitric oxide synthase in chronic lymphocytic leukemia B cells in pro- and antiapoptotic culture conditions. 1457 28

Nucleoside anticancer drugs like gemcitabine (2'-deoxy-2',2'-difluorocytidine) are potent inducers of p53, and ectopic expression of wild-type p53 sensitizes cells to these agents. However, it is also known that nucleosides are efficient activators of apoptosis in tumor cells that do not express a functional p53. To clarify this issue, we examined the effects of gemcitabine and 4'-thio-beta-d-arabinofuranosylcytosine (T-ara-C) on p73, a structural and functional homologue of p53, whose activation could also account for nucleoside-induced apoptosis because no functionally significant mutations of p73 have been reported in cancers. Acute treatment of HCT 116 colon carcinoma cells with gemcitabine or T-ara-C induced marked cytotoxicity and cleavage of caspase-3 and poly(ADP-ribose) polymerase. T-ara-C and gemcitabine markedly induced p53 accumulation as well as increased levels of phospho-p53 (Ser15/Ser20/Ser46) and induced its binding to a consensus p53 response element. Despite robust activation of p53 by T-ara-C and gemcitabine, we found that wild-type and p53-/- HCT 116 cells exhibited almost equivalent sensitivity towards these nucleosides. Examination of p73 revealed that T-ara-C and gemcitabine markedly increased p73 protein levels and p73 DNA-binding activities in both p53-/- and wild-type cells. Furthermore, T-ara-C- and gemcitabine-induced increases in p73 levels occur due to a decrease in p73 protein turnover. RNA interference studies show that nucleoside-induced p73 increases are independent of c-Abl, a nucleoside-activated kinase recently implicated in p73 stabilization. HCT 116 lines, wherein the downstream p53/p73 targets Bax and PUMA (p53 up-regulated modulator of apoptosis) were deleted, were less sensitive to T-ara-C and gemcitabine. Together, these studies indicate that c-Abl-independent p73 stabilization pathways could account for the p53-independent mechanisms in nucleoside-induced apoptosis.
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PMID:c-Abl-independent p73 stabilization during gemcitabine- or 4'-thio-beta-D-arabinofuranosylcytosine-induced apoptosis in wild-type and p53-null colorectal cancer cells. 1650 15

The current study aimed to investigate whether electrical stimulation could prevent apoptotic neuronal cell death during treatment with cytosine arabinoside (ara-C). From in-vitro experiments, the effects of electrical stimulation were assessed on neurite fragmentation and neuronal cell death in ara-C-treated dorsal root ganglion (DRG) explants. Ara-C treatment increased neurite fragmentation and neuronal cell death in DRG explants and activated caspase-3 by cleaving it, which could induce apoptosis. Electrical stimulation can significantly reduce neurite fragmentation and neuronal cell death compared with nonelectrically stimulated groups. Furthermore, electrical stimulation inhibited caspase-3 activation and reduced apoptotic neuronal death in DRG explants. It was suggested that the neuroprotective effect of electrical stimulation is likely mediated by the inhibition of caspase-3 activation and therefore the inhibition of apoptosis following ara-C treatment.
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PMID:Electrical stimulation inhibits cytosine arabinoside-induced neuronal death by preventing apoptosis in dorsal root ganglion neurons. 2760 31


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