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Query: UMLS:C0006142 (breast cancer)
 160,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study evaluated the action of tamoxifen and estradiol on the function of isolated liver mitochondria. We observed that although tamoxifen and estradiol per se did not affect mitochondrial complexes II, III, or IV, complex I is affected, this effect being more drastic (except for state 4 of respiration) when mitochondria were coincubated with both drugs. Furthermore, using two respiratory chain inhibitors, rotenone and diphenyliodonium chloride, we identified the flavin mononucleotide site of complex I as the target of tamoxifen and/or estradiol action(s). Tamoxifen (25 microm) per se induced a significant increase in hydrogen peroxide production and state 4 of respiration. Additionally, a significant decrease in respiratory control ratio, transmembrane, and depolarization potentials were observed. Estradiol per se decreased carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP)-stimulated respiration, state 3 of respiration, and respiratory control ratio and increased lag phase of repolarization. With the exception of state 4 of respiration whose increase induced by tamoxifen was reversed by the presence of estradiol, the effects of tamoxifen were highly exacerbated when estradiol was present. We observed that 10 microm tamoxifen in the presence of estradiol affected mitochondria significantly by decreasing FCCP-stimulated respiration, state 3 of respiration, respiratory control ratio, and ADP depolarization and increasing the lag phase of repolarization. All of the deleterious effects induced by 25 microm tamoxifen were highly exacerbated in the presence of estradiol. Furthermore, we observed that the effects of both compounds were independent of estrogen receptors because the pure estrogen antagonist ICI 182,780 did not interfere with tamoxifen and/or estradiol detrimental effects. Altogether, our data provide a mechanistic explanation for the multiple cytotoxic effects of tamoxifen including its capacity to destroy tamoxifen-resistant breast cancer cells in the presence of estradiol. This new piece of information provides a basis for the development of new and promising anticancer therapeutic strategies.
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PMID:Tamoxifen and estradiol interact with the flavin mononucleotide site of complex I leading to mitochondrial failure. 1641 Feb 52

Multiple functions have been reported for the transcription factor and candidate tumour suppressor, CTCF. Among others, they include regulation of cell growth, differentiation and apoptosis, enhancer-blocking activity and control of imprinted genes. CTCF is usually localized in the nucleus and its subcellular distribution during the cell cycle is dynamic; CTCF was found associated with mitotic chromosomes and the midbody, suggesting different roles for CTCF at different stages of the cell cycle. Here we report the nucleolar localization of CTCF in several experimental model systems. Translocation of CTCF from nucleoplasm to the nucleolus was observed after differentiation of K562 myeloid cells and induction of apoptosis in MCF7 breast cancer cells. CTCF was also found in the nucleoli in terminally differentiated rat trigeminal ganglion neurons. Thus our data show that nucleolar localization of CTCF is associated with growth arrest. Interestingly, the 180 kDa poly(ADP-ribosyl)ated isoform of CTCF was predominantly found in the nucleoli fractions. By transfecting different CTCF deletion constructs into cell lines of different origin we demonstrate that the central zinc-finger domain of CTCF is the region responsible for nucleolar targeting. Analysis of subnucleolar localization of CTCF revealed that it is distributed homogeneously in both dense fibrillar and granular components of the nucleolus, but is not associated with fibrillar centres. RNA polymerase I transcription and protein synthesis were required to sustain nucleolar localization of CTCF. Notably, the labelling of active transcription sites by in situ run-on assays demonstrated that CTCF inhibits nucleolar transcription through a poly(ADP-ribosyl)ation-dependent mechanism.
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PMID:Targeting of CTCF to the nucleolus inhibits nucleolar transcription through a poly(ADP-ribosyl)ation-dependent mechanism. 1659 48

Ecto-5'-nucleotidase (CD73) was overexpressed in malignancies of epithelial origin and was involved in a variety of cellular processes such as cytoprotection and anti-inflammation. In the present study, human mammary T-47D cells were transfected with pcDNA-NT5E to establish a CD73 overexpressed cell model. Short small interfering RNA (siRNA) was used to silence the epidermal growth factor receptor (EGFR) gene. Real-time PCR, RT-PCR and western-blot were used to study CD73 and EGFR expression. Surface CD73 activity was assessed by quantifying the conversion of etheno-AMP to ethenoadenosine via HPLC. Interleukin (IL)-8 mRNA and protein expression were analyzed by RT-PCR and ELISA. Cell motility, invasiveness and adhesion to extracellular matrix (ECM) were measured by in vitro invasion and adhesion assay before and after transfection. We demonstrated that abilities of migration, invasions and adhesion to ECM in pcDNA-NT5E transfected T-47D cells increased significantly, which can be blocked by CD73 inhibitor alpha, beta-methylene ADP(APCP). Addition of adenosine reversed the effects of APCP. The mRNA and protein expression of EGFR and IL-8 increased in pcDNA-NT5E transfected T-47D cells. EGFR siRNA down-regulated EGFR expression dramatically, leading to migration and invasion activities inhibition in pcDNA-NT5E transfected T-47D cells. Our results suggest that up-regulated adenosine production, EGFR and IL-8 expression due to overexpressed CD73 may involved in CD73-promoted breast cancer metastasis.
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PMID:Overexpression of Ecto-5'-nucleotidase (CD73) promotes T-47D human breast cancer cells invasion and adhesion to extracellular matrix. 1747 Oct 30

Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear enzyme that catalyzes the poly(ADP-ribosyl)ation of target proteins in response to DNA damage and has been proposed to play a role in DNA repair, recombination, transcription, cell death, cell proliferation, as well as in stabilization of the genome. We have recently shown that PARP-1 deficiency causes mammary tumorigenesis in mice. In the present study, we investigated whether genetic variants and single nucleotide polymorphisms (SNPs) of PARP-1 contribute to human breast cancer. To this end, we screened all PARP-1 exons, 7.1kb of intron-exon junction and 1.0-kb promoter sequences in 83 French patients with breast cancer and 100 controls by direct sequencing of genomic DNA. Twenty rare genetic variants of PARP-1, including c.1148C>A (Ser383Tyr), c.1354C>A (Arg452Arg), c.2819A>G (Lys940Arg) were detected in nine (10.8%) breast cancers of these patients. Among 31 polymorphic sites examined, five haplotype-tagging SNPs (htSNPs) of PARP-1 were identified. Interestingly, the genotype distribution of htSNP c.852T>C (Ala284Ala) was likely associated with loss of estrogen- and progesterone-receptor expression. The present study implies that genetic variants of PARP-1 may contribute to breast cancerogenesis and that PARP-1 htSNP c.852T>C (Ala284Ala) may influence hormonal therapy of breast cancer.
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PMID:Analysis of genetic variants of the poly(ADP-ribose) polymerase-1 gene in breast cancer in French patients. 1756 Jan 63

The molecular mechanisms of genistein-induced apoptosis of human breast cancer MCF-7 cells were investigated. Genistein showed 50% cell growth inhibition at IC50=27.5+/-0.8 micromol/l in 24 h incubation under 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay conditions. Genistein is known to express both cell growth activity at nanomolar concentrations and anti-cell growth activity at micromolar concentrations. It was found that genistein at 100 micromol/l concentration effectively induced apoptosis of MCF-7 cells in 24 h. Genistein-induced apoptosis involved activation of calpain, caspase 7 and poly(ADP ribose) polymerase. Dantrolene, an inhibitor of Ca release from the endoplasmic reticulum, inhibited genistein-induced activation of calpain and caspase 7, in addition to effectively negating genistein-induced apoptosis. MCF-7 cells treated with genistein also showed increased phosphorylation of p38 mitogen-activated protein kinase, whereas no effect was observed for extracellular signal-regulating kinase 1/2. Phosphorylation of apoptosis signaling kinase 1, an upstream regulator of p38 mitogen-activated protein kinase, was also increased by genistein treatment. Genistein-induced phosphorylation of apoptosis signaling kinase 1 and p38 mitogen-activated protein kinase was diminished by the presence of dantrolene. These results suggest that genistein-induced apoptosis in MCF-7 cells is mediated through calpain-caspase 7 and apoptosis signaling kinase 1-p38 mitogen-activated protein kinase activation cascades that involve Ca release from the endoplasmic reticulum.
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PMID:Genistein-induced apoptosis of human breast cancer MCF-7 cells involves calpain-caspase and apoptosis signaling kinase 1-p38 mitogen-activated protein kinase activation cascades. 1776 93

Poly(ADP-ribose) polymerase 1 (PARP-1) is a DNA-binding enzyme that is activated by DNA breaks, converting them into an intracellular signal via poly(ADP-ribosyl)ation of nuclear proteins. Negatively charged polymers of ADP-ribose (PAR) attached to PARP-1 itself and histones lead to chromatin relaxation, facilitating the access of base excision/single strand break repair proteins and activating these repair enzymes. PARP inhibitors have been developed to investigate the role of PARP-1 in cell biology and to overcome DNA repair-mediated resistance of cancer cells to cytotoxic therapy. Since the early benzamide inhibitors of the 1980s PARP inhibitors, developed through structure-activity relationships and crystal structure-based drug design, that are 1,000 x more potent have been identified. These novel PARP inhibitors have been shown to enhance the antitumour activity of temozolomide (a DNA-methylating agent), topoisomerase poisons and ionising radiation in advanced pre-clinical studies and are now under clinical evaluation. PARP inhibitors can also selectively kill cells and tumours with homozygous defects in the hereditary breast cancer genes, BRCA1 and BRCA2.
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PMID:PARP inhibitor development for systemic cancer targeting. 1789 12

The anti-estrogenic drug tamoxifen, which is used therapeutically for treatment and prevention of breast cancer, can lead to the development of thrombosis. We found that tamoxifen rapidly increased intracellular free calcium [Ca2+]i in human platelets from both male and female donors. Thus 10 microM tamoxifen increased [Ca2+]i above the resting level by 197 +/- 19%. Tamoxifen acted synergistically with thrombin, ADP, and vasopressin to increase [Ca2+]i. The anti-estrogen ICI 182780 did not attenuate the effects of tamoxifen to increase [Ca2+]i; however, phospholipase C inhibitor U-73122 blocked this effect. 4-hydroxytamoxifen, a major metabolite of tamoxifen, also increased [Ca2+]i, but other tamoxifen metabolites and synthetic derivatives did not. Three hydroxylated derivatives of triphenylethylene (corresponding to the hydrophobic core of tamoxifen) which are transitional structures between tamoxifen (Ca agonist) and diethylstilbestrol (Ca antagonist) increased [Ca2+]i slightly (6% to 24%) and partially inhibited thrombin-induced [Ca2+]i elevation (68% to 79%). Therefore the dimethylaminoethyl moiety is responsible for tamoxifen being a Ca agonist rather than antagonist. 4-Hydroxytamoxifen and polymer-conjugated derivatives of 4-hydroxytamoxifen increased [Ca2+]i, with similar efficacy. The ability of tamoxifen to increase [Ca2+]i in platelets, leading to platelet activation, and its ability to act synergistically with other platelet agonists may contribute to development of tamoxifen-induced thrombosis.
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PMID:Tamoxifen stimulates calcium entry into human platelets. 1804 5

Platelets contribute to the development of metastasis, the most common cause of mortality in cancer patients, but the precise role that anti-platelet drugs play in cancer treatment is not defined. Metastatic tumor cells can produce platelet alphaIIb beta3 activators, such as ADP and thromboxane A(2) (TXA(2)). Inhibitors of platelet beta3 integrins decrease bone metastases in mice but are associated with significant bleeding. We examined the role of a novel soluble apyrase/ADPase, APT102, and an inhibitor of TXA(2) synthesis, acetylsalicylic acid (aspirin or ASA), in mouse models of experimental bone metastases. We found that treatment with ASA and APT102 in combination (ASA + APT102), but not either drug alone, significantly decreased breast cancer and melanoma bone metastases in mice with fewer bleeding complications than observed with alphaIIb beta3 inhibition. ASA + APT102 diminished tumor cell induced platelet aggregation but did not directly alter tumor cell viability. Notably, APT102 + ASA treatment did not affect initial tumor cell distribution and similar results were observed in beta3-/- mice. These results show that treatment with ASA + APT102 decreases bone metastases without significant bleeding complications. Anti-platelet drugs such as ASA + APT102 could be valuable experimental tools for studying the role of platelet activation in metastasis as well as a therapeutic option for the prevention of bone metastases.
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PMID:APT102, a novel adpase, cooperates with aspirin to disrupt bone metastasis in mice. 1826 Jan 28

In mammalian cells, ADP ribosylation factor like 2 (Arl2) has been shown to form a complex with tubulin binding cofactor D (TBC-D) and the tumor suppressor protein phosphatase 2A (PP2A). We have previously shown that alterations in Arl2 protein content were associated with corresponding modifications of the tumor suppressor PP2Ac protein content in breast cancer cells. Here, we show that modified Arl2 expression level influences sensitivity to various anticancer compounds such as taxol, navelbine, gemcitabine and doxorubicin in MCF7 derived cell lines. Modifications of Arl2 expression levels were also associated with an altered phosphorylation status and/or cellular sublocalization of certain PP2A targets such as p53, a key mediator of chemotherapy-induced apoptosis. A decreased level of Arl2 expression was associated with an increase of phospho-ser15-p53, a form which was found to be preferentially bound to microtubules. Assays using okadaic and cantharidic acid, two different PP2A inhibitors, showed an increase in microtubule-bound phospho-p53 and reduced sensitivity to chemotherapy. Our results suggest that Arl2 could, via PP2A, influence p53 phosphorylation status. Certain forms of phosphorylated p53 demonstrating increased binding to microtubules appear to be less prone to nuclear translocation after exposure to chemotherapeutic agents, thereby possibly contributing to reduced chemosensitivity.
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PMID:Expression of Arl2 is associated with p53 localization and chemosensitivity in a breast cancer cell line. 1881 14

Previous investigations demonstrated that melatonin exerts an oncostatic action on estrogen-responsive breast cancer, both in vitro and in vivo. Nevertheless, the pro-apoptotic effect of melatonin is still a matter of debate. An experimental study was undertaken to focus on melatonin-related apoptosis and to identify the apoptotic pathways involved. Whole cell-count, flow-cytometry analysis and proteins involved in apoptotic pathways [p53, p73, murine double minute 2 (MDM2), caspases-9,-7,-6, cleaved-poly ADP ribose polymerase (PARP), Bcl-2, Bax and apoptotic inducing factor (AIF)] were investigated in human MCF-7 breast cancer cells treated with physiological (1 nM) concentration of melatonin. Melatonin exerts a significant growth-inhibitory effect on MCF-7 cells, becoming evident after 72 hr and thereafter increasing linearly up to 144 hr. In this model, the growth-inhibition is transforming growth factor beta 1 (TGFbeta1)-dependent and it might be reversed by adding an anti-TGFbeta1 antibody. Melatonin induces a significant rise in apoptotic rate, at both 24 and 96 hr. The anti-TGFbeta1 antibody almost completely suppresses melatonin-related late apoptosis; however, early apoptosis is unaffected. Early programmed cell death is associated with a significant increase in the p53/MDM2 ratio and in AIF release, without modifications in caspase activity or cleaved-PARP levels. Activated caspases-9 and -7 and cleaved-PARP increased significantly at 96 hr, concomitantly with a down-regulation of the Bcl-2/Bax ratio. These data suggest that two distinct apoptotic processes are triggered by melatonin in MCF-7 cells: an early, TGFbeta1 and caspase-independent response, and a late apoptotic TGFbeta1-dependent process in which activated-caspase-7 is likely to be the terminal effector.
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PMID:Evidence for a biphasic apoptotic pathway induced by melatonin in MCF-7 breast cancer cells. 1917 54


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