Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P10415 (Bcl-2)
 33,771 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Etoposide (VP-16) is one of several DNA-damaging agents that induce subcellular structural changes associated with apoptosis. VP-16 exerts its DNA-damaging and cytotoxic effects subsequent to interference with DNA topoisomerase II activity. VP-16 also stimulates c-jun and c-fos mRNA expression in some cell lines, including human leukemia K562 and HL-60 cells. To compare the temporal relationship between drug-induced c-jun expression and apoptosis, we examined cell morphology, cell viability, DNA integrity, and c-jun induction during VP-16 treatment of K562 and HL-60 cells. VP-16 (10 microM)-induced internucleosomal DNA damage and nuclear fragmentation were readily apparent within 6 hr in HL-60 cells but were absent in K562 cells treated for up to 24 hr. Some internucleosomal DNA damage was observed in K562 cells but only after treatment with 100 microM VP-16 for 24 hr. In contrast, VP-16-induced DNA single-strand breaks, VP-16-induced topoisomerase II/DNA covalent complex formation, and VP-16-mediated growth inhibition were similar in K562 and HL-60 cells. Also, the time course of VP-16-induced c-jun mRNA expression was comparable for both K562 and HL-60 cell lines. Western blot analysis of whole-cell lysates showed that Bcl-2 protein levels were 13-fold greater in HL-60 cells than in K562 cells. Thus, the resistance of VP-16-treated K562 cells to apoptosis was not attributable to protection by Bcl-2. Furthermore, the relatively high levels of Bcl-2 in HL-60 cells were not sufficient to protect these cells against apoptosis. Together, our results indicate that the temporal coupling of VP-16-induced DNA damage, c-jun expression, and apoptosis is cell type specific and suggest that different signaling pathways for apoptosis are operating in these two human leukemia cell lines.
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PMID:Differential induction of etoposide-mediated apoptosis in human leukemia HL-60 and K562 cells. 796 39

Treatment of U-937 promonocytic cells with the DNA topoisomerase II inhibitor etoposide rapidly caused death by apoptosis, as determined by changes in chromatin structure, production of DNA breaks, nucleosome-sized DNA degradation, decrease in mitochondrial membrane potential and phosphatidyl serine translocation in the plasma membrane, and at the same time induced intracellular acidification. Both the execution of the apoptotic process and the intracellular acidification were reduced by the addition of forskolin plus theophylline or other cAMP increasing agents. These agents also attenuated the induction of apoptosis by camptothecin, heat-shock, cadmium chloride and X-radiation. Although etoposide slightly increased the production of reactive oxygen intermediates, this increase was not prevented by forskolin plus theophylline, and the addition of antioxidant agents failed to inhibit apoptosis. Etoposide caused a great increase in NF-(kappa)B binding activity, which was not prevented by forskolin plus theophylline, while AP-1 binding was little affected by the topoisomerase inhibitor. The treatments did not significantly alter the levels of Bcl-2 and Bax. By contrast, the expression of c-myc, which was very high in untreated U-937 cells and only partially inhibited by etoposide, was rapidly and almost totally abolished by the cAMP increasing agents. Finally, it was observed that etoposide caused a transient dephosphorylation of retinoblastoma (Rb), which was associated with cleavage of poly(ADP-ribose) polymerase (PARP). Both Rb dephosphorylation and PARP cleavage were inhibited by forskolin plus theophylline. The inhibition of Rb (type I) phosphatase and ICE/CED-3-like protease activities, and the abrogation of c-myc expression, are mechanisms which could explain the anti-apoptotic action of cAMP increasing agents in myeloid cells.
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PMID:cAMP increasing agents attenuate the generation of apoptosis by etoposide in promonocytic leukemia cells. 945 37

The c-myc oncoprotein accelerates programmed cell death (apoptosis) after growth factor deprivation or pharmacological insult in many cell lines. We have shown that max, the obligate c-myc heterodimeric partner protein, also promotes apoptosis after serum withdrawal in NIH3T3 fibroblasts or cytokine deprivation in interleukin-3 (IL-3)-dependent 32D murine myeloid cells. We now show that c-myc- and max-overexpressing 32D cells differ in the nature of their apoptotic responses after IL-3 removal or treatment with chemotherapeutic compounds. In the presence of IL-3, c-myc overexpression enhances the sensitivity of 32D cells to Etoposide (Sigma, St Louis, MO), Adriamycin (Pharmacia, Columbus, OH), and Camptothecin (Sigma), whereas max overexpression increases sensitivity only to Camptothecin. Drug treatment of c-myc-overexpressing cells in the absence of IL-3 did not alter the spectrum of drug sensitivity other than to additively accelerate cell death. In contrast, enhanced sensitivity to Adriamycin, Etoposide, and Taxol (Bristol-Meyers Squibb, Princeton, NJ) was revealed in max-overexpressing cells concurrently deprived of IL-3. Differential rates of apoptosis were not strictly correlated with the ability of the drugs to promote G1 or G2/M arrest. Ectopic expression of Bcl-2 or Bcl-XL blocked drug-induced apoptosis in both cell lines. In contrast, whereas Bcl-2 blocked apoptosis in both cell lines in response to IL-3 withdrawal, Bcl-XL blocked apoptosis in max-overexpressing cells but not in c-myc-overexpressing cells. These results provide mechanistic underpinnings for the idea that c-myc and max modulate distinct apoptotic pathways.
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PMID:Distinct apoptotic responses imparted by c-myc and max. 968 Mar 70

Etoposide is among the most widely used anti-cancer drugs. Its use, however, has been associated with increased risk of secondary acute myeloid leukemia (AML) which is characterized by chromosomal translocations suggesting involvement of recombination-associated motifs at the breakpoints. A PCR-based assay was developed to quantitate the frequency of two illegitimate V(D)J recombinase-mediated genomic rearrangements-a 20-kb deletion in the hprt gene and the bcl2/IgH translocation (t(14;18)) found in non-Hodgkin's lymphoma. We examined both lymphocyte and non-lymphocyte blood cell DNA of children with acute lymphoblastic leukemia (ALL) for changes in the frequencies of these biomarkers during etoposide therapy to determine the level of illegitimate V(D)J recombination changes during therapy. A low level of t(14;18) was found in the lymphocytes before etoposide treatment, which was significantly reduced during etoposide therapy. In before-etoposide samples, no t(14;18) were found among 7.72x107 non-lymphocytes; during treatment none were found among 1.87x108 non-lymphocytes. Deletions were not found before etoposide treatment in either the lymphocytes (6.67x107) or non-lymphocytes (5.43x107) and were non-significantly elevated during etoposide therapy (1 in 1.4x108 lymphocytes and 1 in 1.39x108 non-lymphocytes). It is interesting to note the one patient with an hprt deletion mutation in non-lymphocytes; V(D)J recombination is not normally found in this cell type, but is the cell type from which AML derives. Several patients had clones of t(14;18)-bearing cells as determined by DNA sequence analysis. These results suggest that this etoposide-based chemotherapy was ineffective in producing genomic rearrangements mediated by illegitimate V(D)J recombination in these patients.
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PMID:The frequency of illegitimate V(D)J recombinase-mediated mutations in children treated with etoposide-containing antileukemic therapy. 980 12

The proto-oncogene product Bcl-2 protects a wide variety of cell types from apoptosis via a hitherto unknown mechanism. Bcl-2 has been shown to function upstream of the death proteases (caspases) in some, but not all, occurrences of apoptotic cell death. Using the myeloid leukemic cell line P39 we report the chemotherapy-induced caspase-dependent cleavage of endogenous Bcl-2. Etoposide treatment of these cells triggered a time-dependent activation of type II and type III caspases and cleavage of Bcl-2 yielding a 23 kDa cleavage fragment. The emergence of this cleavage product was blocked by the general caspase inhibitor zVAD-fmk, as well as the type III caspase inhibitor IETD-fmk and the caspase-9-selective inhibitor LEHD-fmk, while the type II caspase inhibitor DEVD-fmk proved considerably less efficient. Bcl-2 cleavage preceded cleavage of the known caspase-3 substrate, poly(ADP-ribose) polymerase (PARP), as well as that of the caspase-6 substrate, lamin B, indicating that Bcl-2 cleavage is a relatively early event in the apoptosis cascade in this experimental model. While evidence for cleavage of Bcl-2 in several subcellular compartments of etoposide-treated cells was obtained, this cleavage was detected predominantly in the mitochondrial fraction, thus providing further support for the central role of mitochondria in apoptosis. Caspase-mediated cleavage following etoposide treatment of these myeloid leukemic cells may represent a means for the attenuation of Bcl-2 function upon apoptosis induction.
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PMID:Cleavage of Bcl-2 is an early event in chemotherapy-induced apoptosis of human myeloid leukemia cells. 1037 76

P39/Tsugane is a myelomonocytoid cell line derived from a patient with myelodysplastic syndrome (MDS). The cells readily undergo apoptosis in response to various agents, and the cell line has been suggested as a useful model to study apoptosis in MDS. The aims of the present study were to assess differentiation and apoptosis induced with all-trans retinoic acid (ATRA) and etoposide, to characterize the mode of apoptosis in these two model systems, and to assess the influence of granulocyte colony-stimulating factor (G-CSF), which in combination with erythropoietin has been shown to inhibit apoptosis in MDS. ATRA induced differentiation and apoptosis in a concentration- and time-dependent manner. Differentiated cells were partially rescued (by 50%) from apoptosis with G-CSF. Etoposide induced apoptosis in a concentration- and time-dependent manner, but no signs of preceding maturation or G-CSF rescue were detected. ATRA- and etoposide-induced apoptosis were both mediated through the caspase pathway and were partially blocked with the general caspase inhibitor zVAD-fmk. Simultaneous treatment with G-CSF and zVAD-fmk additively blocked ATRA-induced apoptosis. However, the two pathways differed in terms of substrate cleavage during apoptosis. ATRA-induced apoptosis caused actin cleavage, which was not affected by G-CSF, and Bcl-2 downregulation. Etoposide induced a caspase-dependent cleavage of Bcl-2, while actin remained intact. The Fas system did not seem to play a major role in any of these apoptotic pathways. Our results may provide new tools to study the mechanisms of apoptosis in MDS.
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PMID:Two pathways of apoptosis induced with all-trans retinoic acid and etoposide in the myeloid cell line P39. 1042 9

The suppression of apoptosis is one mechanism by which tumours become drug resitant. Extracellular signals from the germinal centre (GC) of secondary lymphoid tissue can rescue B cells from physiological- and chemotherapy-induced apoptosis. Such survival signals include CD40 receptor ligation, interleukin-4 (IL-4) receptor stimulation and the interaction of the integrin ligand VCAM-1 with its receptor. The GC environment was modelled in vitro by providing B lymphoma cells with these survival signals. JLP119 B lymphoma cells underwent apoptosis after exposure to the topisomerase II inhibitor etoposide and this was dramatically reduced when the cells were cultured in the GC system. CD40 receptor ligation resulted in increased levels of Bcl-XL. Etoposide diminished the binding between Bax and Bcl-XL but this was restored by IL-4 and VCAM-1 triggered signals. These data demonstrate combined effects of three microenvironmental signals on the Bcl-2 family and illustrate the potential importance of such signalling pathways in drug resistance of tumour cells.
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PMID:Survival signals within the tumour microenvironment suppress drug-induced apoptosis: lessons learned from B lymphomas. 1073 82

Expression of Bcl-2 is important in determining cancer cell resistance to chemotherapy. However, it is not clear whether cell-cell interactions regulate Bcl-2 expression. Using rat breast carcinoma cells selected for loss of hormone responsiveness, we found that parental E-cadherin-expressing cells (E cells) were more sensitive to etoposide-induced apoptosis than hormone-non-responsive cells (F cells), which failed to express E-cadherin. Expression of beta-catenin and pp120 src substrate proteins, which associate with E-cadherin, was unaffected. To determine whether re-expression of E-cadherin in F cells would restore etoposide sensitivity, F cells were transfected with an expression vector coding for the mouse E-cadherin gene. Stable clonal isolates expressing E-cadherin (F. Cad) showed increased sensitivity to etoposide treatment compared with control clones (F.Neo). Expression of E-cadherin resulted in a redistribution of beta-catenin from the cytoskeletal/nuclear fraction to the cytoplasmic/membrane fraction of the cells. E-cadherin-expressing clones also showed reduced invasion through basement membrane. Etoposide-induced apoptosis was characterized by morphological changes (nuclear blebbing) and DNA fragmentation. Induction of CPP32-like caspase activity was also observed in F.Cad transfectants but not F.Neo cells. Unlike F cells, F.Cad transfectants were not able to express Bcl-2, but transient transfection of bcl-2 resulted in re-expression and resistance to etoposide treatment. Therefore, E-cadherin may negatively regulate Bcl-2 expression by altering the availability of nuclear beta-catenin. Loss of E-cadherin in invasive tumor cells may lead to increased Bcl-2 expression and resistance to chemotherapeutic drugs.
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PMID:Expression of E-cadherin reduces bcl-2 expression and increases sensitivity to etoposide-induced apoptosis. 1079 87

Ceramide has recently been regarded as a potential mediator of apoptosis. In the present study, the effects of Bcl-2 and Bax on the ceramide-mediated apoptotic pathways were examined in glioma cells overexpressing Bcl-2 or Bax. Etoposide, cisplatin and tumor necrosis factor-alpha induced apoptosis of C6 rat glioma cells which was associated with ceramide formation due to activation of neutral sphingomyelinase, followed by release of mitochondrial cytochrome c into the cytosol and activation of caspases-9 and -3. The growth of C6 cells stably overexpressing either Bcl-2 or Bax was almost equal to that of the vector-transfected cells. Bax overexpression enhanced etoposide-induced apoptosis through acceleration of cytochrome c release and caspases activation. However, Bax had no effect on ceramide formation. Similar findings were obtained in C6 cells and U87-MG human glioblastoma cells which were transiently overexpressed with Bax. In contrast, Bcl-2 overexpression resulted in a retardation of the apoptotic process via prevention of cytochrome c release and caspases activation, and ceramide formation was also blocked when Bcl-2 was highly overexpressed in glioma cells. In addition, transient overexpression of Bcl-xL also exerted inhibitory effects on ceramide formation and apoptotic cell death induced by etoposide. These results indicate that Bax promotes apoptosis regardless of ceramide formation and that Bcl-2 or Bcl-xL prevents ceramide formation by repressing neutral sphingomyelinase as well as ceramide-induced cytochrome c release. Oncogene (2000) 19, 3508 - 3520
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PMID:Influence of Bax or Bcl-2 overexpression on the ceramide-dependent apoptotic pathway in glioma cells. 1091 9

MCL1 (ML1 myeloid cell leukemia 1), a Bcl-2 (B- cell lymphoma-leukemia 2) homologue, is known to function as an anti-apoptotic protein. Here we show in vitro and in vivo that MCL1 interacts with the cell cycle regulator, proliferating cell nuclear antigen (PCNA). This finding prompted us to investigate whether MCL1, in addition to its anti-apoptotic function, has an effect on cell cycle progression. A bromodeoxyuridine uptake assay showed that the overexpression of MCL1 significantly inhibited the cell cycle progression through the S-phase. The S-phase of the cell cycle is also known to be regulated by PCNA. A mutant of MCL1 that lacks PCNA binding (MCL1(Delta)(4A)) could not inhibit cell cycle progression as effectively as wild type MCL1. In contrast, MCL1(Delta)(4A) retained its anti-apoptotic function in HeLa cells when challenged by Etoposide. In addition, the intracellular localization of MCL1(Delta)(4A) was identical to that of wild type MCL1. An in vitro pull-down assay suggested that MCL1 is the only Bcl-2 family protein to interact with PCNA. In fact, MCL1, not other Bcl-2 family proteins, contained the PCNA-binding motif described previously. Taken together, MCL1 is a regulator of both apoptosis and cell cycle progression, and the cell cycle regulatory function of MCL1 is mediated through its interaction with PCNA.
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PMID:Regulation of apoptosis and cell cycle progression by MCL1. Differential role of proliferating cell nuclear antigen. 1097 39


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