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)

Bcl-2 is a novel protooncogene which prolongs cell survival and suppresses apoptosis. We examined whether constitutive expression of transfected human bcl-2 conferred resistance to two different DNA damaging drugs, nitrogen mustard (HN2) and camptothecin (CPT) in a murine, IL-3 dependent cell line (FL5.12). HN2 treatment produced 2-fold less cell death and DNA degradation in cells overexpressing bcl-2 relative to control cells transfected with a construct bearing only the neoR gene. DNA degradation was characterized by oligonucleosomal length fragments indicating that programmed cell death or apoptosis had occurred. Equimolar HN2 produced similar extents of interstrand cross-link formation and repair in each cell line. Cell cycle characteristics were similar for both cell lines following equimolar HN2 treatment, exhibiting a brief S phase delay followed by a longer G2 arrest. Time course studies indicated that DNA fragmentation occurred following peak G2 arrest in control cells and 12 h later in bcl-2 transfected cells. Equimolar CPT exposure also induced 2-fold less death and apoptotic DNA fragmentation in bcl-2 transfected compared to control cells. DNA single strand break formation and resealing kinetics were comparable in both cell lines following equimolar CPT treatment. CPT caused similar cell cycle perturbations in both cell lines, with a brief S phase block detectable 12 h after an equimolar drug dose. Kinetic studies showed apoptosis occurred following maximal S phase arrest in control and 12 h later in bcl-2 transfected cells. By contrast, IL-3 withdrawal produced rapid and extensive DNA degradation and apoptosis in controls 24 h postwithdrawal, and this process was inhibited 3-4-fold in bcl-2 transfectants. Cell cycle analysis showed both cell lines arrested in G0/G1 following IL-3 removal. In summary, bcl-2 transfection affords a 2-fold protection from HN2 and CPT cytotoxicity and decreases drug induced apoptosis in FL5.12 cells, despite the different mechanisms of action and cell cycle effects of each agent. Bcl-2 overexpression appears to represent a novel drug resistance mechanism of potential clinical significance.
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PMID:Constitutive expression of human Bcl-2 modulates nitrogen mustard and camptothecin induced apoptosis. 846 5

Activated murine peritoneal macrophage cytotoxicity against P815 tumor cells has been shown to be mediated by the reactive nitrogen intermediates (RNI) produced by macrophages from L-arginine through nitric oxide (NO) synthase. Previous results from this laboratory indicated that NO-dependent killing of P815 fulfilled the criteria for apoptotic death. Work by others, in turn, demonstrated that the product of the bcl-2 gene confers protection against various inducers of apoptosis, including reactive oxygen intermediates. Experiments were performed to determine whether Bcl-2 could equally protect sensitive cells from RNI-dependent apoptosis within the context of a relevant biologic system such as the delivery of such RNI by activated macrophages. Results demonstrated that transfection of P815 cells with the human bcl-2 gene confers immunity from RNI-dependent, macrophage-mediated cytotoxicity. In contrast with wild-type or mock-transfected P815 cells, which do not contain detectable Bcl-2, bcl-2-transfected cells showed minimal DNA fragmentation and cell membrane failure when cocultured with activated macrophages. Additional findings indicate that Bcl-2 affords the transfected cells almost complete resistance to the DNA-fragmenting effects of chemically generated NO or H202 and partial protection from their cytolytic effects. These findings are consistent with the hypothesis that tumor cells expressing bcl-2 may escape destruction by macrophage-dependent immune surveillance mechanisms.
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PMID:B cell lymphoma-2 transfected P815 cells resist reactive nitrogen intermediate-mediated macrophage-dependent cytotoxicity. 868 26

Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries but the clinical presentation and rate of disease progression are highly variable. When treatment is required the most commonly used therapy is the nitrogen mustard alkylating agent, chlorambucil (CLB), with or without prednisone. Although CLB has been used in the treatment of CLL for forty years the exact mechanism of action of this agent in CLL is still unclear. Studies in proliferating model tumor systems have demonstrated that CLB can bind to a variety of cellular structures such as membranes, RNA, proteins and DNA; however, DNA crosslinking appears to be most important for antitumor activity in these systems. In addition, a number of different mechanisms can contribute to CLB resistance in these tumor models including increased drug metabolism, DNA repair and CLB detoxification resulting from elevated levels of glutathione (GSH) and glutathione S-transferase (GST) activity. However, unlike tumor models in vitro, CLL cells are generally not proliferating and studies in CLL cells have raised questions about the hypothesis that DNA crosslinking is the major mechanism of antitumor action for CLB in this disease. CLB induces apoptosis in CLL cells and this appears to correlate with the clinical effects of this agent. Thus, alkylation of cellular targets other than DNA, which can also induce apoptosis, may contribute to the activity of CLB. Alterations in genes such as p53, mdm-2, bcl-2 and bax which control entry into apoptosis may cause drug resistance. Loss of wild-type p53 by mutation or deletion occurs in 10 to 15% of CLL patients and appears to correlate strongly with poor clinical response to CLB. The induction of apoptosis by CLB is paralleled by an increase in P53 and Mdm-2 but this increase in not observed in patients with p53 mutations indicating that with high drug concentrations CLB can produce cell death through P53 independent pathways. The level of Mdm-2 mRNA in the CLL cells is not a useful predictor of drug sensitivity. In addition, although Bax and Bcl-2 are important regulators of apoptosis and the levels of these proteins are elevated in CLL cells compared with normal B cells, the levels of Bax and Bcl-2, or the Bax:Bcl-2 ratio, are not important determinants of drug sensitivity in this leukemia. Finally, whereas CLB and nucleoside analogs may produce cell death in CLL by a P53 dependent pathway other agents, such as dexamethasone or vincristine, may act through P53-independent pathways.
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PMID:Chlorambucil in chronic lymphocytic leukemia: mechanism of action. 903 Oct 99

Several genes have been implicated in the regulation of apoptosis including bcl-2, bax, bcl-X and p53. These genes may be important in the development of nitrogen mustard (NM) drug resistance in B-cell chronic lymphocytic leukemia (B-CLL). Using Western blot analysis, we examined the levels of Bcl-2, Bax, Bcl-X and p53 protein expression and determined whether the levels of these proteins correlated with in vitro drug resistance in CLL patients' lymphocyte samples. Our investigations suggest that in CLL, NM drug resistance develops without any detectable alteration of Bcl-2, Bax or Bcl-X. In addition, we determined the presence of p53 mutations in 14 samples in order to assess if there is an association between in vitro drug resistance and the presence of p53 mutations. Using single-stranded conformational polymorphism (SSCP) and sequencing analysis, we observed a p53 mutation in two out of seven resistant samples. The mutation occurring in both cases was a G:C --> A:T transition at codon 273 (exon 8). One of these cases was de novo resistant to the nitrogen mustards. Only one of six samples with acquired resistance to the nitrogen mustards had a p53 mutation suggesting that p53 mutations are not a prominent feature of acquired NM resistance in CLL.
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PMID:Relationship between nitrogen mustard drug resistance in B-cell chronic lymphocytic leukemia (B-CLL) and protein expression of Bcl-2, Bax, Bcl-X and p53. 945 75

The cause of neuronal death in Parkinson's, Alzheimer's, and other neurodegenerative diseases is not known, except in some hereditary forms of these disorders in which a mutated gene has been identified. Even in these cases, the molecular mechanisms that underlie the loss of specific populations of neurons have not been determined, although it is highly probable that apoptosis is involved. Some of the biochemical events that occur during apoptosis have been elucidated. We focus in this review on the role played by the proapoptotic caspases, the antiapoptotic proteins of the Bcl-2 family, and the apoptosis associated signal transducers such as ceramide, calcium, and reactive nitrogen or oxygen species. The role of the mitochondria and the possible implication of cell cycle regulators will also be addressed. Of particular interest are the endogenous inhibitory mechanisms and the pharmacologic agents that can be used to block apoptosis signaling cascades, because they offer models for the development of therapeutic strategies designed to prevent the evolution of pathologic neurodegeneration.
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PMID:Neuropharmacologic aspects of apoptosis: significance for neurodegenerative diseases. 1036 78

In a systematic study to elucidate the involvement of pro- and anti-apoptotic proteins in alkylating drug resistance of tumor cells, we utilized the A2780(100) line, that was selected by repeated exposure of A2780 cell line (human ovarian carcinoma line) to chlorambucil (CBL). A2780(100) was 5 - 10-fold more resistant to nitrogen mustards (IC50 of 50 - 60 microM) and other DNA crosslinking agents, e.g., cisplatin, and also to DNA topoisomerase inhibitor etoposide (ETO) than A2780. CBL (125 microM) induced extensive apoptosis in A2780 associated with mitochondrial damage but not in A2780(100). No significant differences were observed between A2780 and A2780(100) cells in the basal levels, or the enhanced levels in some cases after CBL treatment, of DNA repair proteins involved in repair of alkyl base adducts or in repair of DNA crosslinks or double strand break repair. However, the basal levels of anti-apoptotic proteins Bcl-xL and Mcl-1 were 4 - 8-fold higher in A2780(100) than in A2780 neither of which expressed Bcl-2. In contrast, the levels of pro-apoptotic Bax and Bak were 3 - 5-fold higher in the CBL-treated A2780 but not in A2780(100). ETO (5 microM) induced apoptosis in A2780 without altering the levels of Bax and Bak in these cells. At the same time, neither overexpression of Bcl-xL in A2780, nor its antisense expression in A2780(100), and nor overexpression of Bax in A2780(100), significantly affected drug sensitivity of either line. Our results suggest that a change in an early step in DNA damage processing which affects intracellular signaling, such as enhanced DNA double-strand break repair, could be the primary cause for development of resistance in A2780(100) cells to drugs which induce DNA crosslinks or double strand-breaks.
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PMID:Acquired alkylating drug resistance of a human ovarian carcinoma cell line is unaffected by altered levels of pro- and anti-apoptotic proteins. 1064 89

Nitric oxide (NO) challenge to human neuroblastoma cells (SH-SY5Y) ultimately results in apoptosis. Tumor suppressor protein p53 and cell cycle inhibitor p21 accumulate as an early sign of S-nitrosoglutathione-mediated toxicity. Cytochrome c release from mitochondria and caspase 3 activation also occurred. Cells transfected with either wild type (WT) or mutant (G93A) Cu, Zn-superoxide dismutase (Cu,Zn-SOD) produced comparable amounts of nitrite/nitrate but showed different degree of apoptosis. G93A cells were the most affected and WT cells the most protected; however, Cu, Zn-SOD content of these two cell lines was 2-fold the SH-SY5Y cells under both resting and treated conditions. We linked decreased susceptibility of the WT cells to higher and more stable Bcl-2 and decreased reactive oxygen species. Conversely, we linked G93A susceptibility to increased reactive oxygen species production since simultaneous administration of S-nitrosoglutathione and copper chelators protects from apoptosis. Furthermore, G93A cells showed a significant decrease of Bcl-2 expression and, as target of NO-derived radicals, showed lower cytochrome c oxidase activity. These results demonstrate that resistance to NO-mediated apoptosis is strictly related to the level and integrity of Cu,Zn-SOD and that the balance between reactive nitrogen and reactive oxygen species regulates neuroblastoma apoptosis.
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PMID:Cu,Zn-superoxide dismutase-dependent apoptosis induced by nitric oxide in neuronal cells. 1067 49

Free radicals are highly reactive molecules implicated in the pathology of traumatic brain injury and cerebral ischemia, through a mechanism known as oxidative stress. After brain injury, reactive oxygen and reactive nitrogen species may be generated through several different cellular pathways, including calcium activation of phospholipases, nitric oxide synthase, xanthine oxidase, the Fenton and Haber-Weiss reactions, by inflammatory cells. If cellular defense systems are weakened, increased production of free radicals will lead to oxidation of lipids, proteins, and nucleic acids, which may alter cellular function in a critical way. The study of each of these pathways may be complex and laborious since free radicals are extremely short-lived. Recently, genetic manipulation of wild-type animals has yielded species that over- or under-express genes such as, copper-zinc superoxide dismutase, manganese superoxide dismutase, nitric oxide synthase, and the Bcl-2 protein. The introduction of the species has improved the understanding of oxidative stress. We conclude here that substantial experimental data links oxidative stress with other pathogenic mechanisms such as excitotoxicity, calcium overload, mitochondrial cytochrome c release, caspase activation, and apoptosis in central nervous system (CNS) trauma and ischemia, and that utilization of genetically manipulated animals offers a unique possibility to elucidate the role of free radicals in CNS injury in a molecular fashion.
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PMID:Free radical pathways in CNS injury. 1106 54

Apoptosis, a form of genetically programmed cell death, plays a key role in regulation of cellularity of the arterial wall. During atherogenesis, deregulated apoptosis may cause abnormalities of arterial morphogenesis, wall structural stability, and metabolisms. Many biophysiologic and biochemical factors, including mechanical forces, reactive oxygen and nitrogen species, cytokines, growth factors, oxidized lipoproteins, etc. may influence apoptosis of vascular cells. The Fas/Fas ligand/caspase death-signaling pathway, Bcl-2 protein family/mitochondria, the tumor suppressive gene p53, and the proto-oncogene c-myc may be activated in atherosclerotic lesions and mediate vascular apoptosis during the development of atherosclerosis. Abnormal expression and dysfunction of these apoptosis-regulating genes may attenuate or accelerate vascular cell apoptosis and affect the integrity and stability of plaques. Clarification of the molecular mechanism that regulates apoptosis may help design a new strategy for treatment of atherosclerosis and its major complication, the acute vascular syndromes.
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PMID:Biologic effect and molecular regulation of vascular apoptosis in atherosclerosis. 1128 45

Nitric oxide (NO), an important molecule involved in neurotransmission, vascular homeostasis, immune regulation, and host defense, is generated from a guanido nitrogen of L-arginine by the family of NO synthase enzymes. Large amounts of NO produced for relatively long periods of time (days to weeks) by inducible NO synthase in macrophages and vascular endothelial cells after challenge with lipopolysaccharide or cytokines (such as interferons, tumor necrosis factor-alpha, and interleukin-1), are cytotoxic for various pathogens and tumor cells. This cytotoxic effect against tumor cells was found to be associated with apoptosis (programmed cell death). The mechanism of NO-mediated apoptosis involves accumulation of the tumor suppressor protein p53, damage of different mitochondrial functions, alterations in the expression of members of the Bcl-2 family, activation of the caspase cascade, and DNA fragmentation. Depending on the amount, duration, and the site of NO production, this molecule may not only mediate apoptosis in target cells but also protect cells from apoptosis induced by other apoptotic stimuli. In this review, we will concentrate on the current knowledge about the role of NO as an effector of apoptosis in tumor cells and discuss the mechanisms of NO-mediated apoptosis.
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PMID:Nitric oxide-induced apoptosis in tumor cells. 1144 61


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