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)

We examined the role of Mcl-1 and Bcl-2 expression in the induction of apoptosis. through blocking protein tyrosine kinase (PTK), protein kinase C (PKC), phosphatidylinositol 3-kinase (P13-K) and mitogen-activated protein kinase (MAPK)/Erk kinase (MEK) signaling pathways by various kinase inhibitors in MCF-7 breast cancer cells. The PTK inhibitor genistein (GEN) and PKC inhibitor staurosporine (STP) down-regulated Mcl-1 and Bcl-2 expression, and induced growth inhibition by blocking at the G2/M phase of cell cycle, followed by apoptosis, leading to chromatin condensation and DNA fragmentation. LY294002 (LY)-mediated inhibition of P13-K activity down-regulated Bcl-2 but not Mcl-1 expression. triggered growth arrest at the G1/G0 phase of cell cycle and also led to apoptosis marked with chromatin condensation and DNA fragmentation. The MEK inhibitor U0126 (U0) decreased Bcl-2 expression but not Mcl-1 expression, inhibited cells growth and induced G1/G0 arrest. but in this case cell death occurred without significant apoptotic features. The kinase inhibitor concentration dependence of cytotoxicity correlated well with down-regulation of Bcl-2 but not with changes in Mcl-1 levels. This suggests that Bcl-2 plays a predominant role in the regulation of cell death induced by cell signaling alterations whereas Mcl-1 does not appear to control cell survival under these conditions in MCF-7 cells. Further studies showed that the combination of GEN, STP and LY with U0 can produce synergetic cytotoxic effects on MCF-7 cells. Our results suggest that PTK, PKC, P13-K and MEK signaling pathways can regulate Bcl-2 expression and form an integrated network that plays a critical role in cell survival.
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PMID:Cytotoxicity induced by manipulation of signal transduction pathways is associated with down-regulation of Bcl-2 but not Mcl-1 in MCF-7 human breast cancer. 1176

Reduction of BRCA-1 expression through nonmutational events may be a predisposing event in the onset of sporadic breast cancer. In this study, we investigated the mechanisms through which the environmental carcinogen benzo[a]pyrene (B[a]P) lowered BRCA-1 mRNA levels in breast cancer MCF-7 cells. We report that B[a]P does not compromise the stability of BRCA-1 mRNA, but represses transcriptional activity of a 1.69-kb BRCA-1 (pGL3-BRCA-1) promoter fragment that contains both exon-1A and exon-1B transcription start sites. The loss of BRCA-1 promoter activity was accompanied by accumulation of CYP1A1 and BAX-alpha mRNA and p53 and p21 protein, whereas levels of Bcl-2 mRNA were reduced. The aromatic hydrocarbon receptor ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), which is not metabolized, did not affect BRCA-1 promoter activity or the cellular levels of BRCA-1 and p53 protein, but it did induce a CYP1A1-like promoter. Conversely, treatment with the B[a]P metabolite 7r,8t-dihydroxy-9t,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) repressed BRCA-1 promoter activity and protein, while increasing p53 and p21 protein levels. Transient expression of dominant-negative p53 ((175)Arg-->His) counteracted the detrimental effects of BPDE on BRCA-1 promoter activity and protein levels. Similarly, treatment with B[a]P, TCDD, or BPDE failed to repress transcription from the pGL3-BRCA-1 construct transfected into ZR75.1 breast cancer cells containing mutated p53 ((152)Pro-->Leu). We conclude that activation of the aromatic hydrocarbon receptor is not sufficient for down-regulation of BRCA-1 transcription, which is, however, inhibited by the B[a]P metabolite BPDE through a p53-dependent pathway.
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PMID:Activation of the aromatic hydrocarbon receptor pathway is not sufficient for transcriptional repression of BRCA-1: requirements for metabolism of benzo[a]pyrene to 7r,8t-dihydroxy-9t,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene. 1178 67

PTHrP is secreted by breast cancer cells in vivo and in vitro. In the breast cancer cell line MCF-7, PTHrP overexpression is associated with increased mitogenesis. We used this cell line to study the mechanism for the proliferative effects of PTHrP. Clonal MCF-7 lines were established overexpressing wild-type PTHrP or PTHrP mutated in the nuclear localization signal (NLS). Mutation of the NLS negated the proliferative effects and nuclear trafficking of PTHrP, indicating that increased mitogenesis is mediated via an intracrine pathway. Cells overexpressing wild-type PTHrP were enriched in G2 + M stage of the cell cycle compared with cells overexpressing NLS-mutated PTHrP, indicating an intracrine role for PTHrP in cell cycle regulation. Wild-type PTHrP also protected MCF-7 cells from serum starvation-induced apoptosis. Cells overexpressing wild-type PTHrP showed significantly greater cell survival than cells overexpressing NLS-mutated PTHrP. The ratios of the apoptosis-regulating proteins Bcl-2 to Bax and Bcl-x(L) to Bax were higher in cells overexpressing wild-type, but not NLS-mutated, PTHrP compared with control cells. These findings suggest that the proliferative effects of PTHrP in breast cancer cells are mediated through regulation of the cell cycle and apoptosis, and that controlling PTHrP production in breast cancer may be therapeutically useful.
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PMID:Intracrine PTHrP protects against serum starvation-induced apoptosis and regulates the cell cycle in MCF-7 breast cancer cells. 1179 15

Gemcitabine is a relatively new agent with promising activity in solid tumors. Few data are available regarding mechanisms of resistance to gemcitabine downstream from the drug-target interaction. The present study was performed to gain insight into the role of p53 status on the cytotoxicity of gemcitabine on cancer cells. Drug sensitivity, drug metabolism, cell kinetics and drug-induced apoptosis were compared in 2 lines derived from the mammary adenocarcinoma MCF-7: the wildtype p53 (wt-p53) containing MN-1 cell line and, the MDD2 line containing a dominant negative variant of the p53 protein (mut-p53). The MDD2 cell line was significantly more resistant to gemcitabine cytotoxicity than the MN-1 cell line. The resistant phenotype could not be attributed to a defective gemcitabine activation/degradation pathway or altered levels of expression of intracellular targets. Although both cell lines exhibited p53 accumulation, MN-1 but not MDD2 cells, displayed p21(WAF1) induction after exposure to gemcitabine. Gemcitabine induced an S-phase arrest in both cell lines. A more pronounced block in G1 phase, however, was observed in MN1 cells. Exposure to gemcitabine induced a higher degree of apoptosis in MN-1 than in MDD2 cells. This corresponded with suppression of Bcl-2 and Bcl-X/L expression in wt-p53 cells exposed to gemcitabine whereas Bcl-2 levels remained stable and Bcl-X/L levels increased in mut-p53 cells exposed to gemcitabine. We conclude that the p53 status of cancer cells influences their sensitivity to gemcitabine cytotoxicity. Our evidence suggests that loss of p53 function leads to loss of cell cycle control and alterations in the apoptotic cascade, conferring resistance to gemcitabine in cancer cell lines displaying a mut-p53.
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PMID:Expression of a non-functional p53 affects the sensitivity of cancer cells to gemcitabine. 1180 4

Kaurane diterpenes have been identified from numerous medicinal plants, which have been used for treatment of inflammation and cancer, however, their molecular mechanism of action remains unclear. We have previously shown that kamebakaurin and other three kaurane diterpenes selectively inhibit activation of transcription factor NF-kappaB, a central mediator of apoptosis and immune responses. We here demonstrate that kamebakaurin is a potent inhibitor of NF-kappaB activation by directly targeting DNA-binding activity of p50. Kamebakaurin prevented the activation of NF-kappaB by different stimuli in various cell types. Kamebakaurin did not prevent either stimuli-induced degradation of IkappaB-alpha or nuclear translocation of NF-kappaB, however, it significantly interfered DNA binding activity of activated NF-kappaB in cell and in vitro and preferentially prevented p50-mediated DNA-binding activity of NF-kappaB rather than that of RelA as measured using in vitro translated p50 and RelA proteins. Moreover, a p50 mutant with a Cys-62 --> Ser mutation was not inhibited with kamebakaurin, indicating that the effect of kamebakaurin was probably due to its interaction with cysteine 62 in p50. The covalent modification of p50 by kamebakaurin was further demonstrated by mass spectrometry analysis that showed an increase in the molecular mass of kamebakaurin-treated p50, and this modification was not reverted by addition of dithiothreitol. These results suggested that kamebakaurin exhibited its inhibitory activity by a direct covalent modification of cysteine 62 in the p50. Also, treatment of cells with kamebakaurin prevented the tumor necrosis factor-alpha (TNF-alpha)-induced expression of antiapoptotic NF-kappaB target genes encoding c-IAP1 (hiap-2) and c-IAP2 (hiap-1), members of the inhibitor of apoptosis family, and Bfl-1/A1, a prosurvival Bcl-2 homologue, and augmented the TNF-alpha-induced caspase 8 activity, thereby resulting in sensitizing MCF-7 cells to TNF-alpha-induced apoptosis. Taken together, kamebakaurin is a valuable candidate for the intervention of NF-kappaB-dependent pathological conditions such as inflammation and cancer.
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PMID:Kaurane diterpene, kamebakaurin, inhibits NF-kappa B by directly targeting the DNA-binding activity of p50 and blocks the expression of antiapoptotic NF-kappa B target genes. 1187 50

3,3'-Diindolylmethane (DIM) is a major in vivo derivative of the putative anticancer agent indole-3-carbinol (I3C), which is present in vegetables of the Brassica genus. At concentrations above 10 microM, DIM inhibited DNA synthesis and cell proliferation in both estrogen receptor replete (MCF-7) and deficient (MDA-MB-231) human breast cancer cells in a concentration- and time-dependent manner. These antiproliferative effects were accompanied by characteristic indications of programmed cell death in both cell lines, including externalization of phosphatidylserine, chromatin condensation, and DNA fragmentation. Furthermore, Western and Northern blot analyses, as well as coimmunoprecipitation assays, revealed that in both MCF-7 and MDA-MB-231 cells, DIM treatment decreased total transcript and protein levels of the apoptosis inhibitory protein Bcl-2, and the amount of Bcl-2 bound to the pro-apoptotic protein Bax. DIM treatment also caused an increase in Bax protein levels, but did not affect the level of Bax that was bound to Bcl-2. As a functional test of the role of Bcl-2 down-regulation in the DIM-induced apoptotic response, ectopic expression of Bcl-2 in MCF-7 cells was shown to attenuate the apoptotic effect of DIM. These results demonstrate that DIM can induce apoptosis in breast cancer cells independent of estrogen receptor status by a process that is mediated by the modulated expression of the Bax/Bcl-2 family of apoptotic regulatory factors.
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PMID:Bcl-2 family-mediated apoptotic effects of 3,3'-diindolylmethane (DIM) in human breast cancer cells. 1193 41

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL/APO-2L) induces apoptosis in a variety of tumour cells upon binding to death receptors TRAIL-R1 and TRAIL-R2. Here we describe the sensitization by interferon (IFN)-gamma to TRAIL-induced apoptosis in the breast tumour cell lines MCF-7 and MDA-MB231. IFN-gamma promoted TRAIL-mediated activation of caspase-8, Bcl-2 interacting domain death agonist (Bid) degradation, Bcl-2-associated X protein (Bax) translocation to mitochondria, cytochrome c release to the cytosol and activation of caspase-9 in these cell lines. No changes in the expression of TRAIL receptors were observed upon IFN-gamma treatment. Overexpression of Bcl-2 in MCF-7 cells completely inhibited IFN-gamma-induced sensitization to TRAIL-mediated cell death. Interestingly, TRAIL-induced apoptosis was also clearly enhanced by IFN-gamma in caspase-3-overexpressing MCF-7 cells, in the absence of Bax translocation to mitochondria and cytochrome c release to the cytosol. In summary, our results suggest that IFN-gamma facilitates TRAIL-induced activation of mitochondria-regulated as well as mitochondria-independent apoptotic pathways in breast tumour cells.
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PMID:Mitochondria-dependent and -independent mechanisms in tumour necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis are both regulated by interferon-gamma in human breast tumour cells. 1193 54

MBP-1, a cellular factor, appears to be involved in multiple functions, including transcriptional modulation, apoptosis and cell growth regulation. In this study, we have investigated the signaling pathway involved in MBP-1 mediated apoptotic cell death. Human carcinoma cells infected with a replication deficient adenovirus expressing MBP-1 (AdMBP-1) induced apoptosis, when compared with cells infected by replication-defective adenovirus (dl312) as a negative control. Transduction of MBP-1 in carcinoma cells releases cytochrome c from mitochondria into the cytosol leading to activation of procaspase-9, procaspase-3 and PARP cleavage. We previously observed that MBP-1 mediated apoptosis can be protected by Bcl-2, although MBP-1 does not share a homology with the BH domain of the Bcl-2 family member of proteins. To further understand the mechanism of MBP-1 mediated apoptosis, we examined whether MBP-1 modulates the Bcl-2 gene family. Our results demonstrated that human breast carcinoma cells infected with AdMBP-1 selectively reduced Bcl-xL mRNA and protein expression when compared with dl312 infected negative control cells. An in vitro transient reporter assay also suggested repression of the Bcl-x promoter activity by MBP-1. Additional studies indicated that MBP-1 modulates Ets family protein function, thereby downregulating Bcl-xL expression. Taken together, our results suggest that MBP-1 selectively represses Bcl-xL expression in MCF-7 cells and induces mitochondrial involvement in the apoptotic process.
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PMID:MBP-1 mediated apoptosis involves cytochrome c release from mitochondria. 1197 36

Loss of estrogen-responsiveness and impaired E-cadherin expression/function has been linked to increased metastatic potential of breast cancer cells. In this study, we report that proliferation of breast cancer cells can resume following removal of a toxic stimulus causing severe impairment of cell adhesion and estrogen responsiveness. This type of response was induced by okadaic acid (OA) in MCF-7 cells, and was accompanied by an almost complete block of DNA synthesis, loss of cell-cell contact and cell detachment from culture dishes, loss of estrogen receptor (ER), progesterone receptor (PR) and E-cadherin, whereas only a weak, if any, inhibition of protein synthesis could be observed. These responses were detected in MCF-7 cells after a 1-day treatment with 50 nM OA, and could be reversed if OA-treated cells were recovered in a culture medium devoid of the toxin, so that rescued cells resumed growth 8-12 days after replating. By pulse-chase experiments, we found that protein synthesis was not significantly affected in rescued cells, whose DNA synthesis, instead, was almost completely blocked during the first days of MCF-7 cell rescue from OA treatment. We also analyzed E-cadherin, mitogen activated protein kinase isoforms ERK1 and ERK2, Bcl-2 and BAX proteins during the rescue of MCF-7 cells from OA-induced cell death, and found that their expression followed temporally defined patterns. Cellular levels of E-cadherin returned to control levels within the first days of the rescue, followed by ER, ERK1, and ERK2, and finally by Bcl-2 and BAX proteins. Under our experimental conditions, restoration of cell adhesion did not require a functional ER system, but recovery of a normal ER pool accompanied resumption of estrogen-dependent proliferation of OA-treated MCF-7 cells.
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PMID:Recovery of cellular E-cadherin precedes replenishment of estrogen receptor and estrogen-dependent proliferation of breast cancer cells rescued from a death stimulus. 1211 23

During apoptosis, Smac (second mitochondria-derived activator of caspases)/DIABLO, an IAP (inhibitor of apoptosis protein)-binding protein, is released from mitochondria and potentiates apoptosis by relieving IAP inhibition of caspases. We demonstrate that exposure of MCF-7 cells to the death-inducing ligand, TRAIL (tumor necrosis factor-related apoptosis-inducing ligand), results in rapid Smac release from mitochondria, which occurs before or in parallel with loss of cytochrome c. Smac release is inhibited by Bcl-2/Bcl-xL or by a pan-caspase inhibitor demonstrating that this event is caspase-dependent and modulated by Bcl-2 family members. Following release, Smac is rapidly degraded by the proteasome, an effect suppressed by co-treatment with a proteasome inhibitor. As the RING finger domain of XIAP possesses ubiquitin-protein ligase activity and XIAP binds tightly to mature Smac, an in vitro ubiquitination assay was performed which revealed that XIAP functions as a ubiquitin-protein ligase (E3) in the ubiquitination of Smac. Both the association of XIAP with Smac and the RING finger domain of XIAP are essential for ubiquitination, suggesting that the ubiquitin-protein ligase activity of XIAP may promote the rapid degradation of mitochondrial-released Smac. Thus, in addition to its well characterized role in inhibiting caspase activity, XIAP may also protect cells from inadvertent mitochondrial damage by targeting pro-apoptotic molecules for proteasomal degradation.
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PMID:Proteasome-mediated degradation of Smac during apoptosis: XIAP promotes Smac ubiquitination in vitro. 1212 69


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