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)

Mechanisms of etoposide (VP-16) resistance have been evaluated in a human promyelocytic leukemia HL60 cell line. HL60 resistant (HL60/AR) cells were selected for resistance with adriamycin and were 250-fold resistant to VP-16. We have found that while a significantly higher (10 to 15-fold more) dose of VP-16 was required to induce similar amounts of SDS-KCI-precipitable DNA-protein complex formation in the resistant cell line, there was no difference in the repair of VP-16-induced DNA damage, indicating that differential DNA repair was not involved in VP-16 resistance in HL60 cells. VP-16 treatment significantly inhibited c-myc expression and induced c-jun and c-fos expressions in sensitive cells. In contrast, VP-16 had no effect on c-myc, c-jun or c-fos expressions in resistant cells. The level of bcl2 oncogene was similar in both cell lines; however, treatment with VP-16 resulted in a time- and dose-dependent degradation of the genomic DNA into oligo-sized DNA only in the sensitive cells, indicating that differential expressions of oncogenes (c-myc, c-jun, and c-fos) and susceptibility to apoptosis may play important roles in the sensitivity and resistance to VP-16 in HL60 cells.
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PMID:Differential oncogene expression and susceptibility to apoptosis in the human leukemia HL60 cell lines: implications for etoposide resistance. 764 49

Bcl-2 has been shown to inhibit apoptosis induced by several anticancer agents and to cause a dissociation between etoposide (VP-16)-induced protein-cross-linked DNA strand breaks and VP-16-induced cell death. We suggested previously that VP-16-induced cytotoxicity is mediated by a series of events leading from cleavable complex formation to aberrant DNA recombination, as measured by sister chromatid exchange (SCE) and Southern blot analysis of the hypoxanthine phosphoribosyl transferase (hprt) gene mutations. To further evaluate this hypothesis and to determine whether Bcl-2 could affect any steps leading to the aberrant DNA recombination process, we stably transfected an expression vector containing human Bcl-2 cDNA into V79 Chinese hamster cells. This transfection resulted in overexpression of the Bcl-2 gene product. We subsequently quantitated the relationship between VP-16-induced cytotoxicity, DNA strand breaks, SCE, and mutant frequency at the hprt locus in these Bcl-2-overexpressing cells. Two independent Bcl-2-overexpressing cell lines, BCL2/2 and BCL2/4, showed 3-5 times higher survival at 15 microM VP-16 compared with parental V79 cells or control NeoR cells that were obtained by transfecting V79 cells with the expression vector containing the G-418 resistance gene only. DNA single-strand breaks induced by VP-16 were similar in parental V79, control NeoR, BCL2/2, and BCL2/4 cells. In contrast, VP-16 induced significantly less SCE in Bcl-2-overexpressing cell lines compared with parental V79 and control NeoR cells. The SCE/chromosome induced by 15 microM VP-16 were 0.65, 0.42, 0.09, and 0.10, respectively, in V79, NeoR, BCL2/2, and BCL2/4. In addition, there was an excellent correlation between VP-16-induced SCE and cytotoxicity in all cell lines. Furthermore, VP-16-induced mutant frequencies at the hprt locus were 5-10 times less in BCL-2/2 and BCL-2/4 cells than those observed in the V79 or NeoR control cells. These results indicate that overexpression of Bcl-2 is associated with reduction in VP-16-induced genetic recombination, mutation, and cytotoxicity. Moreover, they suggest that Bcl-2 modulates cytotoxicity of VP-16 between cleavable complex formation and subsequent induction of DNA recombination events. Thus, our results provide important support for the hypothesis that VP-16-induced cytotoxicity is associated with aberrant recombination events, including gene deletions and rearrangements.
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PMID:Inhibition of etoposide (VP-16)-induced DNA recombination and mutant frequency by Bcl-2 protein overexpression. 766 76

Resistance to apoptosis plays an important role in tumors that are refractory to chemotherapy. We report that Bcl-XL, which functions like Bcl-2 to inhibit apoptosis, is highly expressed in MCF-7 human breast carcinoma cells. We used Bcl-XS, a dominant negative inhibitor of Bcl-2 and Bcl-XL, to demonstrate the role of these genes in modulating chemotherapy-induced apoptosis. Bcl-XS overexpressed in MCF-7 cells by stable transfection does not affect viability by itself but induces a marked increase in chemosensitivity to VP-16 or taxol. Using an ELISA assay which quantitates DNA damage, we demonstrate that this sensitization is due to apoptosis, suggesting the therapeutic utility of targeting this pathway.
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PMID:Overexpression of Bcl-XS sensitizes MCF-7 cells to chemotherapy-induced apoptosis. 778 Sep 58

bcl-x is a new member of the bcl-2 gene family and is highly expressed in neural tissues. The present study was designed to determine the expression of the bcl-x gene products in neuroblastoma (NB) and their role in the modulation of chemotherapy-induced apoptosis. Twenty-seven NB cell lines were screened by quantitative immunoprecipitation for Bcl-xL, Bcl-xS, and Bcl-2 expression. None of the cell lines expressed Bcl-xS. Twenty-four of 27 (88%) of the NB cell lines expressed Bcl-xL and 21 of 27 (78%) were positive for Bcl-2. The level of Bcl-xL and Bcl-2 expression was variable among the lines analyzed. Bcl-2 expression was restricted to cells of chromaffin lineage, whereas Bcl-xL was seen in both chromaffin and nonchromaffin lines. To determine whether Bcl-xL could mediate chemotherapy resistance, a NB cell line expressing negligible levels of Bcl-xL was transfected with a bcl-xL expression vector, and unique clones were generated expressing variable levels of Bcl-xL. Cells were treated either with cisplatinum (CP), 4-hydroperoxy-cyclophosphamide (4-HC), or etoposide (VP-16) to induce apoptosis, and cell viability and DNA degradation were determined. Following treatment with CP or 4-HC, Bcl-xL-expressing cells showed significantly increased viability as compared to vector-transfected controls (P < 0.005). Flow cytometric analysis of propidium iodide-stained nuclei following CP or 4-HC treatment revealed significantly increased DNA degradation in controls as compared to Bcl-xL-expressing lines (P < 0.004). DNA analysis by pulsed-field gel electrophoresis revealed high molecular weight (approximately 40 kb) DNA degradation in controls, whereas the DNA in cells expressing Bcl-xL was largely intact. In contrast to CP and 4-HC, results with VP-16 revealed a short-term delay in the onset of apoptosis in Bcl-xL-expressing cells with no long-term survival advantage. The results of these studies indicate Bcl-xL is expressed in NB cells and functions in a manner analogous to Bcl-2 by inhibiting chemotherapy-induced apoptosis.
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PMID:Bcl-xL is expressed in neuroblastoma cells and modulates chemotherapy-induced apoptosis. 778 Sep 71

A variant of human prostate PC3 cells, isolated from PC3 cells, was shown to be significantly resistant (> 10-fold) to several clinically active anticancer drugs, including VP-16 and cisplatin. Previous studies showed that resistance to these drugs was not due to expression of the mdr1 gene, or modifications in topoisomerases but may have resulted from high expressions of certain proto-oncogenes (Yamazaki et al. (1994) Biochim. Biophys. Acta 1226, 89-96). Flow cytometry, DNA gel electrophoresis and northern blot analysis were used to further characterize drug responses in sensitive and resistant cells. Treatment of the sensitive PC3 cells with VP-16 and CDDP resulted in accumulation of cells in S and G2, and G1 and S phases, respectively, and caused significant degradation of the genomic DNA into internucleosomal sized DNA fragments, indicating apoptosis. In contrast, resistant PC3 cells showed little or no DNA fragmentation. Resistant PC3(R) cells expressed 2-3-fold more bcl2 protein than the parental PC3 cells, and overexpressed c-myc, c-jun and H-ras mRNA compared to sensitive cells. Treatment with VP-16 or CDDP significantly induced c-myc mRNA levels in sensitive PC3 cells. H-ras message was not affected by either VP-16 or CDDP treatment in PC3 cells. These studies, taken together, suggest that a differential susceptibility to apoptosis and chemosensitivity may be related to altered levels of bcl2 and/or oncogene overexpression in PC3(R) cells.
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PMID:Relationships between proto-oncogene expression and apoptosis induced by anticancer drugs in human prostate tumor cells. 782 30

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

We reviewed recent reports on apoptosis and summarized the presentations at the Shirafu Cancer Symposium, 1993. The study of programmed cell death, apoptosis, has become one of the mainstream in cell biology, particularly in immunology, developmental biology and oncology. To determine whether the apoptotic cell death induced by anti-cancer agents could be inhibited by bcl-2, we established a bcl-2-transfected human small cell lung cancer cell line, SBC-3/Bcl-2. SBC-3/Bcl-2 showed higher resistance to ADM, CPT-11 and MMC compared with the parental line SBC-3. Agarose gel electrophoresis showed typical DNA fragmentation of SBC-3 following treatment with CPT-11 or MMC. In contrast, the same concentration of the drugs did not induce DNA fragmentation in SBC-3/Bcl-2. However, there was no difference in sensitivity to CDDP, VP-16, ACNU, MTX and Taxol between SBC-3 and SBC-3/Bcl-2 (Ohmori, T. et al. Biochem. Biophys. Res. Commun. 1993). These studies indicate that bcl-2 can modulate the cytotoxicity of some anti-cancer agents by inhibiting the process of apoptosis. We speculate that some apoptotic pathways are bcl-2-sensitive and others bcl-2-independent.
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PMID:[Anticancer agents and apoptosis]. 810 88

Previous studies have shown that the bcl-2 gene encodes a mitochondrial protein that contributes to neoplastic cell expansion primarily by promoting cell survival through interference with "programmed cell death" (PCD), also termed "apoptosis." Because many chemotherapeutic drugs are capable of initiating pathways leading to apoptosis, we determined whether deregulated bcl-2 expression could render cells resistant to several drugs commonly used in the treatment of non-Hodgkin's lymphomas, including dexamethasone (DEX), methotrexate (MTX), 1-beta-D-arabinofuranosyl-cytosine (Ara-C), etoposide (VP-16), vincristine (VC), cisplatin (CP), and hydroperoxycyclophosphamide (4-HC). For these experiments, we achieved high levels of p26-Bcl-2 protein production in a human pre-B-cell leukemia line 697 by stable infection with a recombinant bcl-2-containing retrovirus and then compared these cells with control virus-infected 697 cells. Control 697 cells were induced to undergo apoptosis by all drugs tested as defined by DNA degradation into oligonucleosomal-length fragments, cell shrinkage, and subsequent cell death. In contrast, 697 cells with elevated Bcl-2 protein levels exhibited strikingly prolonged cell survival and markedly reduced DNA fragmentation when cultured in the presence of these antineoplastic agents. Although high levels of Bcl-2 protein protected 697 cells from the acute cytotoxic effects of DEX and the other drugs tested, Bcl-2 did not prevent these drugs from suppressing the proliferation of 697 cells. However, when 697 cells were treated with DEX or MTX for 3 days, then washed and cultured in semisolid media without drugs, bcl-2-virus-infected cells gave rise to colonies at much higher frequencies than 697 cells stably infected with control virus. These results indicate that by protecting 697 leukemic cells from the acute cytotoxicity of DEX and some other chemotherapeutic drugs, high levels of p26-Bcl-2 can create the opportunity for re-initiation of cell growth when drugs are withdrawn. The findings may be relevant to clinical correlative studies of non-Hodgkin's lymphoma patients that have found an association between worse prognosis and bcl-2 gene rearrangements or t[14;18] translocations.
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PMID:Bcl-2 oncoprotein blocks chemotherapy-induced apoptosis in a human leukemia cell line. 841 86

We reviewed recent investigations on apoptosis related to anticancer chemotherapy. The study of programmed cell death, apoptosis, has become one of the main stream in cellular biology, particularly in immunology, developmental biology and oncology. To determine whether the apoptotic cell death induced by anticancer agents could be inhibited by bcl-2 oncogene, we established a bcl-2 transfected human small cell lung cancer cell line, SBC-3/Bcl-2. SBC-3/Bcl-2 showed higher resistance to ADM, CPT-11 and MMC compared to the parental line SBC-3. Agarose gel electrophoresis showed typical DNA fragmentation of SBC-3 following treatment with CPT-11 or MMC. In contrast, the same concentration of the drugs did not induce DNA fragmentation in SBC-3/Bcl-2. However, there was no difference in sensitivity to CDDP, VP-16, ACNU, MTX and Taxol between SBC-3 and SBC-3/Bcl-2 (Ohmori T, et al: Biochem Biophys Res Commun 1993). These results suggest that bcl-2 can modulate the cytotoxicity of some anticancer agents by inhibiting the process of apoptosis. We speculate that some apoptotic pathways are bcl-2-dependent and others bcl-2-independent.
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PMID:[Anticancer agents and apoptosis]. 858 98

Bax, a member of the Bcl-2 family of proteins, has been shown to promote apoptosis while other members of the family, including Bcl-XL and Bcl-2, inhibit cell death induced by a variety of stimuli. The mechanism by which Bax promotes cell death is poorly understood. In the present report, we assessed the ability of Bax to antagonize the death repressor activity of Bcl-XL during chemotherapy-induced apoptosis in the lymphoid cell line, FL5.12. Expression of wild-type Bax countered the repressor activity of Bcl-XL against cell death mediated by VP-16 and cisplatin. We performed site-directed mutagenesis of the BH1, BH2, and BH3 homology regions in Bax to determine the ability of wild-type and mutant Bax to heterodimerize with Bcl-XL and to antagonize the protective effect of Bcl-XL against chemotherapy-induced apoptosis. Bax proteins expressing alanine substitutions of the highly conserved amino acids glycine 108 in BH1, tryptophan 151 and 158 in BH2, and glycine 67 and aspartic acid 68 in BH3 retained their ability to promote chemotherapy-induced cell death that was inhibited by Bcl-XL and to form heterodimers with Bcl-XL. Bax proteins containing deletions of the most highly conserved amino acids in BH1 (Delta102-112) and BH2 (Delta151-159) maintained the ability of Bax to antagonize the death repressor activity of Bcl-XL and to associate with Bcl-XL. However, Bax with BH3 deleted did not form heterodimers with Bcl-XL, but retained its ability to counter the death repressor activity of Bcl-XL. These results demonstrate that the conserved BH3, but not BH1 or BH2, homology region of Bax is necessary for its interaction with Bcl-XL in mammalian cells. Furthermore, our results indicate that Bax does not require BH1, BH2, BH3, or heterodimerization with Bcl-XL to counter the death repressor activity of Bcl-XL. Therefore, Bax can antagonize Bcl-XL during VP-16 and, in a lesser degree, during cisplatin-induced cell death independent of its heterodimerization with Bcl-XL.
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PMID:Bax can antagonize Bcl-XL during etoposide and cisplatin-induced cell death independently of its heterodimerization with Bcl-XL. 879 52


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