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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using molecular hybridization, ligand blotting and immunoprecipitation, our studies were designed to identify the insulin-like growth factor binding proteins (IGFBPs) produced by human breast cancer cells in culture and evaluate their regulation by estradiol (E2) and polyamines (PA). We demonstrate that the hormone-dependent MCF-7 and -independent BT-20 cell lines express the mRNA for IGFBP-2 (1.7 kb) and secrete this BP (31 kDa) in the conditioned medium. In contrast, the hormone-independent MDA-MB-231 cell line does not express the IGFBP-2 gene, while synthesizing and secreting IGFBP-1. E2 administration (10(-9) M) did not significantly influence IGFBPs secretion in MCF-7 cells. Addition of alpha-difluoromethylornithine (DFMO, 4 mM), an inhibitor of PA biosynthesis, consistently lowered IGFBP-2 mRNA in the MCF-7 and BT-20 cell lines and IGFBP-1 mRNA in MDA-MB-231 cells. Surprisingly, however, this compound either did not influence IGFBPs secretion in MCF-7 cells or actually increased their secretion in the BT-20 and MDA-MB-231 cell lines. PA involvement in IGFBPs production by breast cancer cells is complex and may involve differential regulation of transcriptional and post-translational events.
Mol Cell Endocrinol 1991 Jun
PMID:Identification and regulation of insulin-like growth factor binding proteins produced by hormone-dependent and -independent human breast cancer cell lines. 171 94

We have examined the ability of estradiol (E2) to regulate the expression of three mRNAs [for pS2, progesterone receptor (PR), and estrogen receptor (ER)], known to be under E2 regulation in the parental E2 growth-responsive MCF-7 cells, in an E2 growth-independent MCF-7 K3), previously isolated from the parental estrogen-dependent MCF-7 K1 human breast cancer cells after long term growth in vitro in the absence of estrogen, acquired estrogen-independent growth in vitro as well as the ability to form tumors in nude mice in vivo without estrogen. We find that the content of pS2 mRNA and the transcription rate of the pS2 gene, while being markedly increased by E2 in MCF-7 K1 cells, are no longer stimulated by E2 in this subline, although protein kinase activators tremendously increase (greater than 10-fold) pS2 mRNA in both K1 and K3 cells. In fact, basal pS2 mRNA levels are elevated 2.8 +/- 0.4-fold in MCF-7 K3 cells, and E2 evokes a concentration-dependent suppression of the pS2 mRNA level. In contrast, PR mRNA in the K3 subline, as in the parental K1 cells, is still up-regulated by E2, and ER mRAN content and the ER mRNA transcription rate are still down-regulated by E2 and show normal E2 dose-response relationships, implying that the ER in this subline is functional. These results demonstrate that the progression to estrogen-independent growth in K3 cells is accompanied by a change in the regulation of some estrogen-induced genes by estrogen. While PR and ER retain normal patterns of regulation by E2, the pS2 gene in the estrogen growth-independent K3 subline is differentially affected and is no longer stimulated by E2. Our data suggest that this altered regulation of the pS2 gene is probably not caused by a defect of the ER or ER regulation in this subline.
Mol Endocrinol 1991 Sep
PMID:Differential regulation of gene expression by estrogen in estrogen growth-independent and -dependent MCF-7 human breast cancer cell sublines. 172 71

The effects of 17 beta-estradiol, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and their combination on the metabolism of [1-13C] glucose were determined in cell suspensions of wild-type MCF-7 human breast cancer cells, by 13C NMR spectroscopy. Preliminary studies showed that, during the 7-hr duration of the NMR experiment, the cells maintained their viability and their aryl hydrocarbon responsiveness. Lactate was the major glucose metabolite detected in these studies, and the rate of lactate formation in the untreated (control) and 17 beta-estradiol (10(-9) M)-treated cells was 60 and 86 fmol/cell/hr, respectively; this represented a 40% increase in lactate formation in the cells treated with 17 beta-estradiol; comparable results were observed for the percentage of glucose converted into lactate. In contrast, TCDD (10(-9) M) did not significantly alter the rate of glucose metabolism or lactate formation. Co-treatment of the cells with 17 beta-estradiol (10(-9) M) plus TCDD (10(-8) to 10(-10) M) showed that TCDD completely inhibited the 17 beta-estradiol-induced metabolism of [13C] glucose to lactate in MCF-7 cells. In contrast, 2,8-dichlorodibenzo-p-dioxin (10(-8) M), a weak aryl hydrocarbon receptor agonist, did not inhibit estrogen-induced glucose-to-lactate metabolism in MCF-7 cells. In addition, it was shown that TCDD caused a significant decrease in 17 beta-estradiol-induced lactate formation within 1 hr after treatment, whereas the induction of monooxygenase activity was not observed until 3 hr after exposure of the cells to TCDD. These data indicate that TCDD-induced 17 beta-estradiol metabolism is not related to the decrease in the rate of conversion of glucose to lactate. These results further define the antiestrogenic responses elicited by TCDD and show that 13C NMR spectroscopy provides a unique method for measuring, in real time, the effects of TCDD on specific metabolic pathways.
Mol Pharmacol 1991 Dec
PMID:Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on 17 beta-estradiol-induced glucose metabolism in MCF-7 human breast cancer cells: 13C nuclear magnetic resonance spectroscopy studies. 175 38

We have used the screening techniques of chemical mismatch cleavage, single stranded conformational polymorphism, and gel retardation to discover a number of estrogen receptor RNA variants in clinical breast cancer tissues. We have found basepair insertions, transitions, and deletions as well as alternative splicing, yielding deletions of exon 3, 5, or 7. Using a yeast transactivation assay we have discovered receptors with outlaw function, including both a dominant-positive receptor, which is transcriptionally active in the absence of estrogen, and a dominant-negative receptor, which is itself transcriptionally inactive, but prevents the action of normal estrogen receptor. These variants could have clinical significance, helping to explain breast tumor behavior and patient outcome.
Mol Endocrinol 1991 Nov
PMID:Estrogen receptor variants in clinical breast cancer. 177 64

Experiments were undertaken to characterize mRNAs coding for the estrogen receptor (ER) in the human breast cancer cell line T47D. We report here the isolation of cDNAs corresponding to three isoforms of this receptor in addition to a majority of wild-type clones. Sequence analysis showed that these isoforms are generated through alternative splicing. None of the alternatively spliced isoforms of ER is able to bind to an estrogen-responsive element (ERE) in a gel mobility shift assay in vitro or to activate transcription of a reporter gene containing an ERE in vivo. One isoform, ER delta E3, which harbors a deletion of exon 3 encoding the second zinc finger of the DNA-binding domain, inhibits estrogen-dependent transcription activation in a dominant negative fashion when it is cotransfected with the wild-type ER and reporter plasmid. It also inhibits DNA binding of wild-type ER in a gel mobility shift assay in vitro. Since ER delta E3 is not able to bind to its response element, the observed inhibitory effect probably occurs through protein-protein interactions. This could involve the formation of a heterodimer between mutant and wild-type receptors, competition for a limiting transcription factor, or both. These results may have implications for understanding the loss of estrogen responsiveness that frequently occurs in breast cancer.
Mol Endocrinol 1991 Nov
PMID:Identification of a dominant negative form of the human estrogen receptor. 177 72

We studied the effects of interleukin-1 alpha (IL-1) and tumor necrosis factor-alpha (TNF), alone and in combination, on MCF-7 breast cancer cells to determine whether these cytokines alter cell growth, TNF gene expression, and TNF secretion. We found that IL-1 alone and TNF alone inhibited cell growth in a dose-dependent manner. Each cytokine arrested growth in the G0/G1 phase of the cell cycle, with maximum growth inhibition at 1000 U/ml (P less than 0.05) and 100 U/ml (P less than 0.01), respectively. However, the combination of these two cytokines did not result in greater growth inhibition or a greater percentage of cells arrested in the G0/G1 phase of the cell cycle compared with each cytokine alone. We examined the effect of exogenous IL-1 and TNF on TNF gene expression by Northern blot analysis. In the absence of any cytokine, these cells do not express TNF mRNA. Exposure to IL-1 (1000 U/ml) induced TNF mRNA at 3 h; however, mRNA levels diminished thereafter to barely detectable levels by 24 h. Exposure to TNF (1000 U/ml) also induced TNF mRNA at 3 h, but in contrast to IL-1, the level of enhanced expression persisted at these levels through 72 h of exposure. Secretion of TNF by these cells is induced by exogenous TNF, but not by IL-1. IL-1 and TNF in combination do not produce greater inhibition of growth, greater amounts of TNF mRNA at 3 h, or greater secretion of TNF than that produced by TNF alone.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1991 Nov
PMID:Interleukin-1 alpha and tumor necrosis factor-alpha (TNF alpha) inhibit growth and induce TNF messenger RNA in MCF-7 human breast cancer cells. 177 75

Human progesterone receptors (PR) were overexpressed in Spodoptera frugiperda (Sf9) insect cells using a recombinant baculovirus system. Recombinant viruses were constructed that produced either full-length A (94K) or B (120K) forms of human PR, and each was expressed as a functional protein. Steroid and DNA binding activities were found to be indistinguishable from that of endogenous human PR in T47D breast cancer cells. Moreover, as analyzed by gel-mobility shift, recombinant PR-A and PR-B each bound to specific progesterone response elements in a strictly hormone-dependent manner. Native receptors expressed in Sf9 cells also exhibited structural properties similar to that of endogenous PR. Cytosolic PR (PR-A or PR-B), prepared in low salt buffer, sedimented on density gradients as an 8S oligomeric complex that was converted largely to 4S by treatment with 0.4 M NaCl. Immune isolation of the 8S cytosol PR complex and analysis of protein composition revealed the presence of two specific copurifying proteins of approximately 90K and 70K. The 90-K component was identified immunologically as heat shock protein 90. The 70-K component was not identified but is likely to be the insect equivalent of heat shock protein 70. Immune isolation of PR from Sf9 cells metabolically labeled with [32Pi], revealed that expressed PR was capable of being phosphorylated in insect cells. Hormone addition to Sf9 cells, however, did not stimulate the same increase in PR phosphorylation or upshift in mobility on sodium dodecyl sulfate gels that occurs with endogenous receptors in T47D cells. Thus some, but not all, phosphorylations occur with human PR expressed in Sf9 cells. These phosphorylation data, together with the fact that expressed PR required hormone for DNA binding, indicate that the hormone-dependent phosphorylation step responsible for PR upshifts on sodium dodecyl sulfate-polyacrylamide gel electrophoresis is not required for receptor binding to DNA. The baculovirus expression system, therefore, may prove valuable in dissecting the functional role(s) for both hormone-dependent and hormone-independent PR phosphorylation.
Mol Endocrinol 1991 Nov
PMID:Characterization and functional properties of the A and B forms of human progesterone receptors synthesized in a baculovirus system. 177 77

Expression of transforming growth factor alpha (TGF alpha) mRNA and protein can be stimulated by estrogens such as 17 beta-estradiol (E2) in estrogen-responsive rodent and human breast cancer cells. To ascertain if E2 can directly regulate TGF alpha expression through the 5'-flanking region of the human TGF alpha gene, E2-responsive MCF-7 or ZR-75-1 human breast cancer cells or E2-nonresponsive MDA-MB-231 breast cancer cells were transiently transfected with a plasmid containing an 1140-base pair (bp) Sac-I fragment of the TGF alpha 5'-flanking region ligated to the chloramphenicol acetyltransferase (CAT) gene. Cells that were transfected and subsequently treated with physiological concentrations of E2 (10(-11)-10(-8) M) for 24 h exhibited a 2- to 10-fold increase in CAT activity. The E2 stimulation of CAT activity was dose-dependent with an increase first found at 10(-10) M E2. The increase in CAT activity could be detected within 24-36 h after the addition of E2. There was no significant change in CAT activity in transiently transfected MDA-MB-231 cells as mediated through the TGF alpha 5'-flanking region after E2 treatment. MCF-7 cells were also transiently transfected with different fragments of the TGF alpha 5'-flanking region ligated to the luciferase gene. In the absence of E2 treatment, no detectable luciferase activity was found.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1991 Dec
PMID:Regulation by estrogen through the 5'-flanking region of the transforming growth factor alpha gene. 179 40

Cell proliferation and phenotype of cells from female reproductive tissues are regulated by estrogens. It is therefore important to understand how estrogen action can be modulated. It recently has been reported that certain nuclear receptors can antagonize the tumor promoter 12-O-tetradeconylphorbol-13-acetate (TPA) by direct interaction with the transcription factor AP-1, and that the AP-1 constituents cJun and cFos can inhibit receptor activity. This mutual antagonism appears to be based on direct protein-protein interaction. In the human breast cancer cell line MCF-7, TPA leads to growth arrest and altered cell morphology. We have investigated here whether in MCF-7 cells and other cell lines AP-1 and estrogen receptors (ERs) can inhibit each other's activity. We find that TPA or the AP-1 components cJun and cFos can inhibit estradiol-dependent estrogen receptor activity in most cell lines investigated. In addition, ER mRNA is rapidly down-regulated in MCF-7 cells. Gel retardation experiments show that ER DNA binding is inhibited in vitro by cJun protein, while ER also can inhibit cJun DNA binding. However, in vivo we do not observe inhibition of AP-1 activity by ER in the cell lines investigated here. On the contrary, we observed an enhancing effect at low ER concentrations on AP-1. Together our data suggest a new regulatory pathway by which ER activity can be modulated by AP-1. Several mechanisms including ER-AP-1 protein interaction appear to be involved.
Mol Endocrinol 1991 Dec
PMID:Inhibition of estrogen receptor activity by the tumor promoter 12-O-tetradeconylphorbol-13-acetate: a molecular analysis. 179 43

In order to investigate further the mechanisms associated with growth inhibition of human breast cancer cells by progestins and nonsteroidal antiestrogens, their effect on c-myc gene expression in T-47D-5 and T-47D cells has been investigated. The c-myc mRNA levels were differentially regulated by the synthetic progestin, medroxyprogesterone acetate and the nonsteroidal antiestrogen, monohydroxytamoxifen, in both cell lines. Antiestrogen treatment caused a persistent decrease in c-myc mRNA levels while the progestin caused a more complex response. Initially c-myc mRNA levels increased approx. 2-fold, this was followed by a decrease and then partial recovery. The end result, however, of each of these treatments is decreased cell number.
J Steroid Biochem Mol Biol 1991 Jul
PMID:Differential regulation of c-myc by progestins and antiestrogens in T-47D human breast cancer cells. 182 55


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