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)

It is well known that dysfunction of the apoptotic pathway confers apoptosis resistance and results in a low sensitivity of human cancer cells to therapeutic agents. A novel strategy to overcome the resistance is to target the apoptotic pathway directly. To identify molecular targets in the apoptotic pathway that are differentially regulated in cancer and normal cells, we have examined the levels of apoptotic effectors and inhibitors in human tumor and normal cell lines as well as in cancer and normal tissues. These include three pancreatic cancer lines (BXPC-3, MIA PaCa-2, and Panc-1), four breast cancer cell lines (MDA-MB-231, MDA-MB-435, MDA-MB-361, and MCF-7), and colon carcinoma line (SW620). Additionally, breast carcinoma tissue specimens were examined. Compared with normal human fibroblast and mammary epithelial cell lines, we detected high basal levels of caspase-3 and caspase-8 activities and active caspase-3 fragments in the tumor cell lines and cancer tissues in the absence of apoptotic stimuli. Furthermore, the tumor cells expressed high levels of survivin and XIAP, two members of the inhibitor of apoptosis (IAP) protein family. When the activity of these IAPs was blocked by expression of dominant-negative mutant survivin (survivinT34A) and XIAP-associated factor 1, respectively, apoptosis was induced in tumor but not normal cell lines. Moreover, down-regulation of both survivin and XIAP significantly enhanced tumor-cell apoptosis as compared with inhibition of either survivin or XIAP alone. These results suggest that up-regulated IAP expression counteracts the high basal caspase-3 activity observed in these tumor cells and that apoptosis in tumor cells but not normal cells can be induced by blocking IAP activity. Therefore, IAPs are important molecular targets for the development of cancer-specific therapeutic approaches.
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PMID:Coexistence of high levels of apoptotic signaling and inhibitor of apoptosis proteins in human tumor cells: implication for cancer specific therapy. 1458 79

Apoptosis occurs in the placenta throughout gestation, with a greater frequency near term in comparison to the first trimester. The Fas/FasL system represents one of the main apoptotic pathways controlling placental apoptosis. Although first trimester trophoblast cells express both Fas and FasL, they are resistant to Fas-induced apoptosis. Therefore, trophoblast resistance to Fas-mediated apoptosis may be due to the inhibition of the pathway downstream of Fas stimulation. Expression levels of X-linked inhibitor of apoptosis (XIAP) were recently shown to decrease in third trimester placentas, correlating with an increase in placental apoptosis. As a potent caspase inhibitor, XIAP prevents the activation of caspase-9 through its BIR3 domain and caspase-3 activation via the linker-BIR2 domain. In the present study, high levels of the active form of XIAP were detected in first trimester trophoblast cells, whereas term placental tissue samples predominantly expressed the inactive form of XIAP. Using a XIAP inhibitor, phenoxodiol, we demonstrate that XIAP inactivation sensitizes trophoblast cells to Fas stimulation, as evidenced by the anti-Fas mAb-induced decrease in trophoblast cell viability and increase in caspase-8, caspase-9 and caspase-3 activation. This suggests a functional role for XIAP in the regulation of the Fas apoptotic cascade in trophoblast cells during pregnancy.
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PMID:X-linked inhibitor of apoptosis (XIAP) confers human trophoblast cell resistance to Fas-mediated apoptosis. 1466 4

T cells expressing human leukemia virus (HTLV) type 1, the etiological agent of adult T-cell leukemia, are remarkably resistant to conventional chemotherapy, and the need for drugs that effectively kill these cells is apparent. Here we show that roscovitine, an inhibitor of cyclin-dependent kinases (CDKs), induces the apoptosis of the HTLV-1-transformed T-cell line MT-2. Roscovitine prevented the tyrosine phosphorylation and consequent activation of the transcription factor signal transducer and activator of transcription (STAT) 5 when presented to MT-2 cells in the presence or absence of a caspase-3 inhibitor, and ectopic expression of a dominant-negative form of STAT5 in MT-2 cells induced apoptosis. Roscovitine and dominant-negative STAT5 also reduced the expression of the antiapoptotic protein XIAP, and STAT5 was associated with the XIAP promoter in vivo. Antibody to platelet-derived growth factor (PDGF) alpha receptors coprecipitated STAT5 from extracts of untreated but not roscovitine-treated cells. The tyrosine phosphatase inhibitor sodium orthovanadate ablated the inhibitory effects of roscovitine on STAT5/PDGF alpha receptor interaction, STAT5 activity, and cell survival. We suggest that roscovitine reduces the abundance of tyrosine-phosphorylated PDGF alpha receptors; as a result, STAT5 does not become active, and STAT5 gene products required for cell survival are not expressed.
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PMID:Roscovitine inhibits STAT5 activity and induces apoptosis in the human leukemia virus type 1-transformed cell line MT-2. 1467 20

Apicidin, a histone deacetylase inhibitor, is a novel cyclic tetrapeptide with potent antiproliferative activity against various cancer cells. We examined whether apicidin potentiates the imatinib-induced apoptosis of Bcr-Abl-positive human leukaemia cells. In K562 cells, the co-administration of minimally toxic concentrations of imatinib and apicidin (imatinib/apicidin) for 48 h produced a marked increase in mitochondrial damage, processing of caspase cascades and apoptosis. Similar results were observed in leukaemic blasts obtained from patients with chronic myeloid leukaemia in blast crisis. Imatinib/apicidin co-treatment for 48 h resulted in a near complete loss of the full-length XIAP (X-linked inhibitor of apoptosis) protein, with a corresponding increase in the 29-kDa XIAP cleavage product. Both the degradation of XIAP and increased release of second mitochondria-derived activator of caspase/direct IAP-binding protein with low pI (Smac/DIABLO) into the cytosol were abrogated by pretreatment with the caspase-3 inhibitor DEVD-CHO. Imatinib/apicidin co-treatment for 48 h produced a prominent decrease in Bcr-Abl protein levels in a caspase-dependent manner. In summary, these data indicate that apicidin potentiates the imatinib-induced apoptosis of Bcr-Abl-positive leukaemia cells through the enhanced activation of the mitochondria-dependent caspase cascades, accompanied by caspase-dependent downregulation of Bcr-Abl and XIAP. These findings generate a rationale for further investigation of apicidin and imatinib as a potential therapeutic strategy in Bcr-Abl-positive leukaemias.
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PMID:Apicidin potentiates the imatinib-induced apoptosis of Bcr-Abl-positive human leukaemia cells by enhancing the activation of mitochondria-dependent caspase cascades. 1468 26

Many environmental and therapeutic agents initiate apoptotic cell death by inducing the release of cytochrome c from the mitochondria, which activates Apaf-1 (apoptotic protease-activating factor-1). This large (approximately 130kD) protein is a mammalian homologue of CED-4, an essential protein involved in programmed cell death in the nematode C. elegans. Cytochrome c activates Apaf-1, which oligomerizes to form an approximately 700-1400-kDa caspase-activating complex known as the Apaf-1 apoptosome. Caspase-9, an initiator caspase, is then recruited to the complex by binding to Apaf-1 through CARD-CARD (caspase recruitment domain) interactions to form a holoenzyme complex. Subsequently, the Apaf-1/caspase-9 holoenzyme complex recruits the effector caspase-3 via an interaction between the active site cysteine in caspase-9 and the critical aspartate, which is the cleavage site for generating the large and small subunits of caspase-3 that constitute the activated form of caspase-3. This initiates the caspase cascade that is responsible for the execution phase of apoptosis. Intracellular levels of K+, XIAP an inhibitor of apoptosis protein, and at least two mitochondrial released proteins, Smac/DIABLO and Omi/Htra 2 a serine protease, tightly regulate formation and function of the apoptosome. Thus, a number of physiological mechanisms ensure that the apoptosome complex is only fully assembled and functional when the cell is irrevocably committed to die. It is interesting that more recent studies show that a variety of small molecules can directly activate or inhibit caspase activation by interfering with the formation and function of the apoptosome complex. The cytotoxicity of many conventional chemotherapeutic drugs rests on their ability to induce apoptosome formation and apoptosis. Defects in this pathway can result in drug resistance, and the discovery that small molecules can directly activate or inhibit the apoptosome may provide new alternative treatments for cancer.
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PMID:Chemical-induced apoptosis: formation of the Apaf-1 apoptosome. 1470 65

The mechanisms of apoptosis in the loss of myocytes in skeletal muscle with age and the role of mitochondrial and sarcoplasmic reticulum-mediated pathways of apoptosis are unknown. Moreover, it is unknown whether lifelong calorie restriction prevents apoptosis in skeletal muscle and reverses age-related alterations in apoptosis signaling. We investigated key apoptotic regulatory proteins in the gastrocnemius muscle of 12 and 26 month old ad libitum fed and 26 month old calorie-restricted male Fischer-344 rats. We found that apoptosis increased with age and that calorie-restricted rats showed less apoptosis compared with their age-matched cohorts. Moreover, pro- and cleaved caspase-3 levels increased significantly with age and calorie-restricted rats had significantly lower levels than the aged ad libitum group. Neither age nor calorie restriction had any effect on muscle caspase-3 enzyme activity, but the levels of X-linked inhibitor of apoptosis, particularly an inhibitor of caspase-3, increased with age and were reduced significantly in the 26 month old calorie-restricted cohort. The apoptotic inhibitor apoptosis repressor with a caspase recruitment domain (ARC), which inhibits cytochrome c release, underwent an age-associated decline in the cytosol but increased with calorie restriction. In contrast, mitochondrial ARC levels increased with age and were lower in calorie-restricted rats than in age-matched controls, suggesting a translocation of this protein to attenuate oxidative stress. The translocation of ARC may explain the reduction in cytosolic cytochrome c levels observed with age and calorie restriction. Moreover, we found a striking approximately 350% increase in the expression of procaspase-12 (caspase located at the sarcoplasmic reticulum) with age which was significantly lower in the 26 month old calorie-restricted group. The total protein level of apoptosis-inducing factor in the plantaris muscle increased with age and was reduced calorie-restricted rats compared with age-matched controls, but there were no significant changes in this pro-apoptotic protein in the isolated nuclei. Calorie restriction is able to lower the apoptotic potential in aged skeletal muscle by altering several key apoptotic proteins toward cellular survival, thereby reducing the potential for sarcopenia.
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PMID:Aging and lifelong calorie restriction result in adaptations of skeletal muscle apoptosis repressor, apoptosis-inducing factor, X-linked inhibitor of apoptosis, caspase-3, and caspase-12. 1473 88

There are many factors contributing to the resistance to TRAIL (Tumor necrosis factor-related apoptosis-inducing ligand)-induced apoptosis. However, it is not clear whether the mechanism of resistance to TRAIL is constitutive or inductive. Therefore, the purpose of this study was to investigate the resistant mechanisms to TRAIL at different levels in the apoptotic pathway. The human T-lymphoblastic leukemic CEM cell line showed more resistant to TRAIL-induced apoptosis compared with the human chronic myeloid leukemic K562 cell line. Lower level of constitutive caspase-8 expression in the CEM cell line led to a poor response to both TRAIL-induced activation of caspase-3 and reduction in the mitochondrial membrane potential (DeltaPsim). There was no significant difference in the constitutive levels of NF-kappaB in CEM and K562 cell lines. However, CEM cells showed a faster response to TRAIL-induced NF-kappaB activation than K562 cells. TRAIL-induced regulation of Bcl-2 family of proteins included an up-regulation in Bcl-2/Bcl-XL and a down-regulation in Bax. IAPs, such as XIAP, cIAP-1, cIAP-2 and Survivin were all up-regulated during the treatment with TRAIL. In summary, our data suggest that the leukemic cells resistance to TRAIL-induced apoptosis might be due to the deficiency in the constitutive caspase-8 expression. Development of potential resistance to apoptosis by TRAIL can occur in both TRAIL-resistant and TRAIL-sensitive leukemic cells.
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PMID:Potential mechanisms of leukemia cell resistance to TRAIL-induced apopotosis. 1473 5

In this issue of Cancer Cell, Schimmer et al. report the identification of small molecule antagonists of XIAP that overcome its inhibition of caspase-3. It was remarkable that the compounds directly induced cell death in tumor cells while having little toxicity on normal cells. This suggests that caspases are already activated in tumor cells, which is different from the caspase activation status in normal mammalian cells. In comparison with Smac peptides targeting XIAP-mediated caspase-9 inhibition, which do not directly induce cell death, it appears that liberating downstream caspases rather than upstream caspases may be a preferred strategy for cancer drug discovery.
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PMID:Antagonizing XIAP-mediated caspase-3 inhibition. Achilles' heel of cancers? 1474 24

The apoptosome is a large caspase-activating ( approximately 700-1400 kDa) complex, which is assembled from Apaf-1 and caspase-9 when cytochrome c is released during mitochondrial-dependent apoptotic cell death. Apaf-1 the core scaffold protein is approximately 135 kDa and contains CARD (caspase recruitment domain), CED-4, and multiple (13) WD40 repeat domains, which can potentially interact with a variety of unknown regulatory proteins. To identify such proteins we activated THP.1 lysates with dATP/cytochrome c and used sucrose density centrifugation and affinity-based methods to purify the apoptosome for analysis by MALDI-TOF mass spectrometry. First, we used a glutathione S-transferase (GST) fusion protein (GST-casp9(1-130)) containing the CARD domain of caspase-9-(1-130), which binds to the CARD domain of Apaf-1 when it is in the apoptosome and blocks recruitment/activation of caspase-9. This affinity-purified apoptosome complex contained only Apaf-1XL and GST-casp9(1-130), demonstrating that the WD40 and CED-4 domains of Apaf-1 do not stably bind other cytosolic proteins. Next we used a monoclonal antibody to caspase-9 to immunopurify the native active apoptosome complex from cell lysates, containing negligible levels of cytochrome c, second mitochondria-derived activator of caspase (Smac), or Omi/HtrA2. This apoptosome complex exhibited low caspase-processing activity and contained four stably associated proteins, namely Apaf-1, pro-p35/34 forms of caspase-9, pro-p20 forms of caspase-3, X-linked inhibitor of apoptosis (XIAP), and cytochrome c, which was only bound transiently to the complex. However, in lysates containing Smac and Omi/HtrA2, the caspase-processing activity of the purified apoptosome complex increased 6-8-fold and contained only Apaf-1 and the p35/p34-processed subunits of caspase-9. During apoptosis, Smac, Omi/HtrA2, and cytochrome c are released simultaneously from mitochondria, and thus it is likely that the functional apoptosome complex in apoptotic cells consists primarily of Apaf-1 and processed caspase-9.
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PMID:Pro-apoptotic proteins released from the mitochondria regulate the protein composition and caspase-processing activity of the native Apaf-1/caspase-9 apoptosome complex. 1499 23

A functional disorder associated with weightlessness is well documented in osteoblasts. The apototic features of this disorder are poorly understood. Harmful stress induces apoptosis in cells via mitochondria and/or Fas. The Bax triggers cytochrome c release from mitochondria, which can be blocked by the Bcl-2. Released cytochrome c then activates the initiator caspase, caspase-9, which can be blocked by the anti-apototic (IAP) family of molecules. The effector caspase, caspase-3, finally exerts DNA fragmentation. We conducted this study to examine the apoptotic effects of vector-averaged gravity on normal human osteoblastic cells. Cell culture flasks were incubated on the clinostat, which generated vector-averaged gravity condition (simulated microgravity) for 12, 24, 48, and 96 hours. Upon termination of clinostat cultures, the cell number and cell viability were assessed. DNA fragmentation was analyzed on the agarose-gel electrophoresis. The mRNA levels for Bax, Bcl-2, XIAP, and caspase-3 genes were analyzed by semi-quantitative RT-PCR. Twenty-four hours after starting clinostat rotation, the ratios of Bax/Bcl-2 mRNA levels (indicator of apoptosis) were significantly increased to 136% of the 1G static controls. However, the XIAP mRNA levels (anti-apoptotic molecule) were increased concomitantly to 138% of the 1G static controls. Thus, cell proliferation or cell viability was not affected by vector-averaged gravity. DNA fragmentation was not observed in clinostat group as well as in control group. Finally, the caspase-3 mRNA levels were not affected by vector-averaged gravity. Simulated microgravity might modulate some apoptotic signals upstream the mitochondrial pathway.
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PMID:Antagonism between apoptotic (Bax/Bcl-2) and anti-apoptotic (IAP) signals in human osteoblastic cells under vector-averaged gravity condition. 1503 9


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