Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of the non-tumor-promoting protein kinase C (PKC) activator bryostatin 1 and the PKC inhibitors staurosporine and UCN-01 were examined with respect to modulation of 1-[beta-D-arabinofuranosyl]cytosine (ara-C)-induced apoptosis in human myeloid leukemia cells (HL-60) overexpressing the antiapoptotic protein Bcl-2. HL-60/Bcl-2 cells displayed a 5-fold increase in Bcl-2 protein compared with empty-vector counter-parts (HL-60/pCEP4) but comparable levels of Bax, Mcl-1, and Bcl-xL. After exposure to an equimolar concentration of ara-C (10 microM for 6 hr), HL-60/Bcl-2 cells were significantly less susceptible to apoptosis, DNA fragmentation, and loss of clonogenicity than HL-60/pCEP4 cells. The protective effect of increased Bcl-2 expression was manifested by a failure of ara-C to induce activation/cleavage of the Yama protease (CPP32; caspase-3) and degradation of one of its substrates, poly(ADP-ribose)polymerase to an 85-kDa cleavage product. When HL-60/Bcl-2 cells were preincubated with bryostatin 1 (10 nM; 24 hr) or coincubated with either staurosporine (50 nM; 6 hr) or UCN-01 (300 nM; 6 hr) after a 1-hr preincubation, exposures that exerted minimal effects alone, ara-C-induced apoptosis and DNA fragmentation were restored to levels equivalent to, or greater than, those observed in empty-vector controls. These events were accompanied by restoration of the ability of ara-C to induce CPP32 cleavage and activation, poly(ADP-ribose) polymerase degradation, and inhibition of colony formation. Western analysis of Bcl-2 protein obtained from overexpressing cells treated with bryostatin 1, staurosporine, or UCN-01 revealed the appearance of a slowly migrating species and a general broadening of the protein band, effects that were insensitive to the protein synthesis inhibitor cycloheximide. Alterations in Bcl-2 protein mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis were reversed by treatment of lysates with alkaline phosphatase or protein phosphatase 2A; actions of the latter were blocked by the specific phosphatase inhibitor okadaic acid. In vivo labeling studies of Bcl-2 protein demonstrated increased incorporation of [32PO4]orthophosphate in drug-treated cells. Last, phosphorylated Bcl-2 failed to display decreased binding to the proapoptotic protein Bax. Collectively, these findings indicate that bryostatin 1, which down-regulates PKC, and staurosporine and UCN-01, which directly inhibit the enzyme, circumvent resistance of Bcl-2-overexpressing leukemic cells to ara-C-induced apoptosis and activation of the protease cascade. They also raise the possibility that modulation of Bcl-2 phosphorylation status contributes to this effect.
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PMID:Agents that down-regulate or inhibit protein kinase C circumvent resistance to 1-beta-D-arabinofuranosylcytosine-induced apoptosis in human leukemia cells that overexpress Bcl-2. 939 80

Valinomycin is a potassium ionophore, and is well known to cause the collapse of the mitochondrial membrane potential. It has been reported that loss of mitochondrial membrane potential is observed in the early stages of apoptosis induced by various agents. Thus, the effects of valinomycin on tumor cells were examined. Valinomycin induced uncoupling of respiration and depolarization of isolated mitochondria. Depolarization of intact mitochondria in AH-130 rat ascites hepatoma cells was also induced by valinomycin. Valinomycin induced apoptosis revealing the typical apoptotic characteristics such as fragmentation and ladder formation of DNA, shrinkage of cells, and formation of pycnotic nucleus. There was a correlation between the depolarization of mitochondria and DNA fragmentation. After depolarization of mitochondria, the activity of caspase-3-like protease but not caspase-1-like protease increased markedly. In contrast, this apoptosis did not involve the release of reactive oxygen species from mitochondria, increase in intracellular calcium concentration, or protein synthesis. In addition, anti-apoptotic members of the Bcl-2 family (Bcl-xL and Bcl-2) were not correlated with apoptosis. These results indicate that valinomycin might induce apoptosis through degradation of the mitochondrial membrane potential. Taken together, these observations suggest that there may be a mechanism that transmits the signal from mitochondrial depolarization to subsequent apoptosis execution steps.
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PMID:Valinomycin induces apoptosis of ascites hepatoma cells (AH-130) in relation to mitochondrial membrane potential. 943 61

The expression of several apoptosis-regulating genes was evaluated in 9 human breast cancer cell lines, 2 immortalized human mammary epithelial lines, 1 normal breast tissue biopsy, and 3 primary breast tumors, using a multiple antigen detection (MAD) immunoblotting method. The anti-apoptotic proteins Bcl-2, Bcl-X(L), Mcl-1, and BAG-1 were present at immunodetectable levels in 7, 10, 10, and 9 of the 11 lines. Comparing these 11 cell lines among themselves revealed that steady-state levels of Bcl-2, Bcl-X(L), Mcl-1, and BAG-1 were present at relatively higher levels in 4, 6, 5, and 5 of the lines, respectively. In contrast, the pro-apoptotic proteins Bax and Bak were detected in all 11 cell lines, and were present at relatively higher levels in 10 and 5 of the 11 lines, respectively. The Interleukin-1beta converting enzyme (ICE) homolog CPP32 (Caspase-3) was expressed in 10/11 breast cell lines. High levels of p53 protein, indicative of mutant p53, were found in 8 of the 11 lines and correlated inversely with Bax expression (p = 0.01). Bcl-2 and BAG-1 protein levels were positively correlated (p = 0.03). Immunoblot analysis of primary adenocarcinomas revealed expression of the anti-apoptotic proteins Bcl-2, Bcl-X(L), Mcl-1, and BAG-1, as well as the pro-apoptotic proteins Bax, Bak, and CPP32, in at least 2 of the 3 tumors examined. Immunohistochemical analysis was also performed for all of these proteins using 20 paraffin-embedded breast cancer biopsy specimens that all contained residual normal mammary epithelium in combination with both invasive cancer and carcinoma in situ. All of these apoptosis-regulating proteins were detected in primary breast cancers, though the percentage of immunopositive tumor cells varied widely in some cases. Comparisons of the intensity of immunostaining in normal mammary epithelium and invasive carcinoma suggested that Bcl-2 immunointensity tends to be lower in cancers than normal breast epithelium (p = 0.03), whereas CPP32 immunointensity was generally higher in invasive cancers (p < 0.0001). Taken together, the results demonstrate expression of multiple apoptosis-modulating proteins in breast cancer cell lines and primary tumors, suggesting complexity in the regulation of apoptosis in these neoplasms of mammary epithelial origin.
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PMID:Expression of multiple apoptosis-regulatory genes in human breast cancer cell lines and primary tumors. 949 1

Interleukin-1beta converting enzyme (ICE) family proteases (caspases) are known to be implicated as important effectors of apoptotic pathways. The purpose of this study was to elucidate the role of ICE family proteases in apoptosis of mouse cells derived from the terminal proximal tubule (S3) treated with cisplatin, an anti-tumor drug, or staurosporine, a protein kinase C inhibitor. For this purpose, we measured the activities of ICE family proteases and examined the effects of tetrapeptide and viral ICE family protease inhibitors on the activities of ICE family proteases in and the degree of apoptosis of S3 cells treated with cisplatin and staurosporine. RT-PCR analysis revealed that S3 cells as well as mouse kidney express mRNA for ICE and CPP32, an ICE family protease. Results of enzymatic analysis, determination the degree of DNA fragmentation and cytotoxicity test suggest that CPP32 mediates cisplatin-induced apoptosis of S3 cells, whereas ICE family proteases other than CPP32 mediate staurosporine-induced apoptosis of S3 cells. In conclusion, distinct ICE family proteases mediate apoptosis of mouse proximal tubule cells depending on the stimuli to which the cells are exposed.
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PMID:Distinct interleukin-1beta-converting enzyme family proteases mediate cisplatin- and staurosporine-induced apoptosis of mouse proximal tubule cells. 951 15

Homeostasis of cell numbers is achieved by balancing the proliferative and death states of cells. Proper regulation in a cell requires an accurate coordination between these two processes. Indeed, dysregulation of cell cycle progression is essential for the initiation of apoptosis. Retinoblastoma protein (RB) is an important tumor suppressor and a cell cycle regulator. Most recent studies suggest that RB also plays a regulatory role in the process of apoptosis. During the onset of apoptosis, the hyperphosphorylated form of RB (p120/hyper) is converted to a hypophosphorylated form (p115/hypo), which is mediated by a specific protein-serine/ threonine phosphatase activity. Accompanied by the internucleosomal fragmentation of DNA, the newly formed p115/hypo/RB is immediately cleaved by a protease that has properties of the caspase family. During apoptosis, RB is also cleaved in its carboxyl terminus by a caspase-3-like activity. By contrast, the unphosphorylated form of RB (p110/unphos) remains uncleaved during apoptosis. Further studies suggest that p110/unphos/RB functions as an inhibitor of apoptosis. Therefore, regulation of the RB proteolytic activities and consequent RB levels is important for the determination of cellular fate.
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PMID:RB and apoptotic cell death. 954 37

Proteolytic cleavage of key cellular proteins by caspases (ICE, CPP32, and Ich-1/Nedd2) may be crucial to the apoptotic process. The retinoblastoma tumor suppressor gene is a negative regulator of cell growth and the retinoblastoma protein (pRb) exhibits anti-apoptotic function. We show that pRb is cleaved during apoptosis induced by either UV irradiation or anti-Fas antibody. Our studies implicate CPP32-like activity in the proteolytic cleavage of pRb. The kinetics of proteolytic cleavage of pRb during apoptosis differ from that observed for other cellular proteins, suggesting that the specific cleavage of pRb during apoptosis may be an important event.
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PMID:Proteolytic cleavage of retinoblastoma protein upon DNA damage and Fas-mediated apoptosis. 955 24

How tumor cells develop resistance to apoptosis induced by cytokines and chemotherapeutic agents is incompletely understood. In the present report, we investigated apoptosis induction by tumor necrosis factor (TNF) in two human T cell lines, Jurkat and HuT-78. While TNF inhibited the growth of Jurkat cells and activated caspase-3, it had no effect on HuT-78 cells. It was further found that HuT-78 cells constitutively expressed the nuclear transcription factor NF-kappaB. TNF activated NF-kappaB in Jurkat cells but not in HuT-78 cells. HuT-78 cells were also resistant to NF-kappaB activation induced by phorbol ester, H2O2, ceramide, endotoxin, and interleukin-1. Despite the presence of preactivated NF-kappaB, HuT-78 cells also expressed high levels of IkappaB-alpha, the inhibitory subunit of NF-kappaB and, unlike Jurkat cells, were resistant to TNF-induced degradation of IkappaB-alpha. Its half-life in HuT-78 cells was 12 h as opposed to 45 min in Jurkat cells. Antibodies against TNF blocked the constitutive activation of NF-kappaB and proliferation of HuT-78 cells but had no significant effect on Jurkat cells, suggesting an autocrine role for TNF. The antioxidant pyrrolidine dithiocarbamate also suppressed constitutive NF-kappaB activation and it reversed the cell's sensitivity to TNF-induced cytotoxicity and activation of caspase-3. Overall, these results suggest that constitutive activation of NF-kappaB, TNF, and prooxidant pathway in certain T cell lymphomas causes resistance to apoptosis, and this can be reversed by antioxidants.
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PMID:Constitutive activation of NF-kappaB causes resistance to apoptosis in human cutaneous T cell lymphoma HuT-78 cells. Autocrine role of tumor necrosis factor and reactive oxygen intermediates. 959 51

Multidrug resistance mediated by the drug efflux protein, P-glycoprotein (P-gp), is one mechanism that tumor cells use to escape death induced by chemotherapeutic agents. However, the mechanism by which P-gp confers resistance to a large variety of structurally diverse molecules has remained elusive. In this study, classical multidrug resistant human CEM and K562 tumor cell lines expressing high levels of P-gp were less sensitive to multiple forms of caspase-dependent cell death, including that mediated by cytotoxic drugs and ligation of Fas. The DNA fragmentation and membrane damage inflicted by these stimuli were defined as caspase dependent by various soluble peptide fluoromethylketone caspase inhibitors. Inhibition of P-gp function by the anti-P-gp mAb MRK-16 or verapamil could reverse resistance to these forms of cell death. Inhibition of P-gp function also enhanced drug or Fas-mediated activation of caspase-3 in drug-resistant CEM cells. By contrast, caspase-independent cell death events in the same cells, including those mediated by pore-forming proteins or intact NK cells, were not affected by P-gp expression. These observations suggest that, in addition to effluxing drugs, P-gp may play a specific role in regulating some caspase-dependent apoptotic pathways.
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PMID:The drug efflux protein, P-glycoprotein, additionally protects drug-resistant tumor cells from multiple forms of caspase-dependent apoptosis. 961 32

The molecular events involved in tumor cell death induced by novel photoproducts of merocyanine 540 (pMC540) are poorly understood. Using HL60 leukemia and M14 melanoma cell lines we investigated the role of the apoptotic pathway in pMC540-mediated cell death. Tumor cells exposed to pMC540 showed cell size shrinkage and an increase in the sub-diploid DNA content. A loss of membrane phospholipid asymmetry associated with apoptosis was induced by pMC540 in both tumor cell lines as evidenced by the externalization of phosphatidylserine. A dose-dependent increase in caspase-3 protease activity suppressed by the tetrapeptide inhibitor DEVD-CHO was observed in both cell lines. Western blot analysis of poly (ADP-ribose) polymerase, a caspase substrate, showed the classical cleavage pattern (116 to 89 kDa) associated with apoptosis in pMC540-treated cell lysates. Furthermore, caspase inhibition blocked the externalization of membrane PS, indicating that the loss of membrane phospholipid asymmetry is a downstream event of caspase activation. These findings demonstrate that tumor cell death induced by pMC540 is mediated by caspase proteases.
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PMID:Caspase proteases mediate apoptosis induced by anticancer agent preactivated MC540 in human tumor cell lines. 965 88

Activation of the p53-mediated DNA damage response induces either G1 cell cycle arrest or apoptosis. The G1 cell cycle arrest is in part caused by the p53-dependent transcriptional activation of the CDK inhibitor, p21(Cip1/Waf1). We report here that human p21 protein is rapidly induced but selectively cleaved during the apoptotic response to gamma-irradiation. Such an event occurred early, well before the morphological appearance of apoptosis. Ectopical expression of p53 in tumor cells alone could induce p21 expression, followed by p21 cleavage and apoptosis. The cleavage of p21 could be reproduced in extracts prepared from irradiated cells or by recombinant caspase-3, suggesting that a caspase-like activity is responsible for this cleavage. p21 binds independently to both CDK2 and proliferation cell nuclear antigen (PCNA). Our studies indicated that p21 cleavage by the caspase-like activity specifically abolished its interaction with PCNA, suggesting that p21 cleavage may interfere with normal PCNA-dependent repair. Our data suggest that p21 may serve as a critical checkpoint regulator for both cell cycle arrest and apoptosis during the p53-mediated DNA damage response. Manipulation of the checkpoint regulators involved in cell cycle arrest and apoptosis may thus provide a novel strategy to cancer therapy.
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PMID:Cleavage of CDK inhibitor p21(Cip1/Waf1) by caspases is an early event during DNA damage-induced apoptosis. 966 8


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