Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04155 (pS2)
 1,234 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In search of critical genes in the mechanism of estrogen action in human breast cancer, we previously showed that estrogen stimulates transcription of the c-myc gene in estrogen-dependent (MCF-7) cells. We have now examined the role of c-myc in estrogen-stimulated growth of MCF-7 cells through the use of a synthetic antisense c-myc phosphorothioate oligonucleotide to specifically inhibit expression of the c-myc protein. Estrogen induces a 5-fold increase in c-myc protein expression within 90 min in steroid-deprived cells, as detected by Western blot. Prior exposure of MCF-7 cells to 10 microM c-myc antisense oligonucleotide results in up to 95% inhibition of the c-myc protein expression induced by estrogen. Antisense-myc oligonucleotide inhibits estrogen-stimulated cell growth by up to 75% over 9 days and also exerts a cytostatic effect on the growth of estrogen-independent MDA-MB-231 cells which show relatively high, constitutive expression of c-myc. Sense-myc and antisense-pS2 oligonucleotides have no effect on c-myc protein level or growth in either cell line. These results demonstrate both the specific and durable effects of antisense phosphorothioate oligonucleotides. Furthermore, these results indicate a critical role for c-myc in the growth of breast cancer cells and support the hypothesis that loss of estrogen regulation of this gene may be an important factor in the progression of breast cancer.
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PMID:Inhibition of c-myc expression by phosphorothioate antisense oligonucleotide identifies a critical role for c-myc in the growth of human breast cancer. 185 15

The phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA) (10 nM) produce a marked reduction in the growth, measured by thymidine uptake, of MCF-7 cells in full growth medium, but had only a small effect on MDA-MB-231 and T47D cells. Bryostatin alone also inhibited growth but to a lesser extent than seen with TPA. The effect of TPA on MCF-7 cells was partially reversed by bryostatin, added simultaneously or after TPA, suggesting bryostatin does not simply mimic TPA in this system. Even though both are believed to act via effects on protein kinase C, bryostatin appears to act as antagonist to the effect of TPA as well as a partial agonist on its own. When the oestrogen receptor positive MCF-7 and T47D cells were maintained in charcoal stripped serum, the increase in DNA synthesis on stimulation with oestradiol was inhibited with 50 nM TPA in MCF-7 cells but not in T47D cells. The effects of these treatments on the expression of two well characterised oestrogen responsive genes pNR2(pS2) and pNR100 (Cathepsin-D) were examined. Rather than preventing transcription of these oestrogen responsive genes, TPA alone increased pNR2 and pNR100 levels in MCF-7 cells and the combined effect of oestradiol and TPA had a marked synergistic effect in increasing the transcript levels of these genes. In T47D cells pNR2 transcripts were not detected and the increase in pNR100 mRNA levels were not affected by TPA. We conclude that the inhibitory effects of TPA on the growth stimulation of MCF-7 cells by oestradiol was not due to a general inhibition of the expression of oestrogen responsive genes. An alternative possibility examined was that the growth inhibitory effect of TPA on MCF-7 cells might be due to stimulation of TGF-beta 1, acting as an autocrine inhibitory growth factor. Oestradiol treatment of MCF-7 cells reduced the levels of TGF-beta 1 mRNA whereas TPA produced a marked increase. The combined effect of TPA and oestradiol further increased TGF-beta 1 mRNA above the levels seen with TPA alone. Bryostatin had little effect on TGF-beta 1 expression either alone or in combination with oestradiol. These observations are consistent with the hypothesis that the inhibitory effect of TPA on MCF-7 cells may be partly due to autocrine inhibition by TGF-beta 1.
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PMID:Phorbol ester and bryostatin effects on growth and the expression of oestrogen responsive and TGF-beta 1 genes in breast tumour cells. 191 Dec 15

Of the steroid hormone receptor family members, the estrogen receptor (ER) is notable in containing a sizable (42-amino acid) C-terminal region, denoted domain F. This F region differs from its adjacent hormone-binding domain, domain E, in that it is not well conserved among different vertebrate ER species, and its role in the biological activity of the ER is not well defined. We report an important role for the F domain of the ER in modulating the magnitude of gene transcription by estrogen and antiestrogen, and in determining the effectiveness of antiestrogens in suppressing estrogen-stimulated gene transcription. Using transient transfections, we have examined, in several cell types, the transcriptional activity of the full-length wild type human ER and ER lacking the carboxy-terminal F domain (delta F ER, containing amino acids 1-554) or ER altered in the F domain by point mutations. In some cells, namely Chinese hamster ovary (CHO) cells and MDA-MB-231 human breast cancer cells expressing wild type ER or delta F ER, estradiol (E2) stimulates equally transcription of several estrogen-responsive promoter-reporter gene constructs [estrogen ca-18119 element, (ERE)2-TATA-CAT, (ERE)2-pS2-CAT, (ERE)2-progesterone receptor(distal)-CAT]; however, the antiestrogens trans-hydroxytamoxifen and ICI 164,384, which stimulate transcription of some of these reporter constructs with the wild type ER, were unable to stimulate transcription with delta F ER. In addition, these antiestrogens were more effective antagonists of E2-stimulated transcription by delta F ER than by wild type ER. By contrast, in HeLa human cervical cancer cells and 3T3 mouse fibroblast cells, the delta F ER exposed to E2 is much less effective than wild type ER in stimulating transcription, and antiestrogens were less potent in suppressing E2-stimulated transcription by the delta F ER. These differences in response of the delta F and wild type ER to estrogen or antiestrogen do not appear to be due to a change in receptor expression level, binding affinity for ligands, or binding to estrogen response element DNA. Our data support the supposition that the conformation of the receptor-ligand complex is different with estrogen vs. antiestrogen and with wild type vs. delta F ER, such that its potential for interaction with protein cofactors or transcription factors is different and is markedly influenced by cell context. Thus, the F domain of the ER has a specific modulatory function that affects the agonist/antagonist effectiveness of antiestrogens and the transcriptional activity of the liganded ER in cells.
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PMID:The carboxy-terminal F domain of the human estrogen receptor: role in the transcriptional activity of the receptor and the effectiveness of antiestrogens as estrogen antagonists. 747 65

In addition to stimulation of the target gene fatty-acid synthetase, the synthetic progestin R5020 strongly inhibited estradiol-induced pS2 and cathepsin D mRNA levels in MCF7 human breast cancer cells as shown by Northern blot analysis. Inhibition was half-maximal with 30 pM R5020, and the antiprogestin RU486 had only a weak effect. Two human progesterone receptor isoforms have been described; isoform A is a truncated form of isoform B and lacks the 164 N-terminal amino acids. We hypothesized that the two isoforms could have a differential capacity to transrepress estrogen-induced responses. Therefore, in MDA-MB231 cells containing no progesterone and estrogen receptors, we transiently transfected progesterone receptor expression vectors coding for form B (hPR1 or hPR0) or form A (hPR2) along with the estrogen receptor expression vector HEO. We show that R5020 inhibited estradiol-induced transcription of the pS2-CAT reporter plasmid only in cells selectively expressing isoform B. The same results were obtained when progesterone receptor isoforms were overexpressed in MCF7, Ishikawa, HeLa, or NIH-3T3 cells. Transrepression was dependent on the promoter context since the extent of inhibition by isoform B was higher when evaluated with pS2 or cathepsin D nonpalindromic estrogen-responsive element-mediated transcription than with the perfect palindromic form of the vitellogenin gene. Isoform A was inefficient regardless of the reporter construct used. Inhibition varied with the isoform ratio, and isoform B had a dominant effect, with > 70% inhibition measured in cells transfected with the same amount of both progesterone receptor isoforms. Progestin repressed only one of the two transcription activation functions of the estrogen receptor, AF-2, which corresponds to the hormone-binding domain. We conclude that differential expression of progesterone receptor isoforms could be responsible for a tissue-specific inhibition of estrogen target genes by progestins.
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PMID:Differential effect of forms A and B of human progesterone receptor on estradiol-dependent transcription. 808

The effects of cadmium on estrogen receptor and other estrogen-regulated genes in the human breast cancer cell line MCF-7 were studied. Treatment of MCF-7 cells with 1 microM cadmium decreased the level of estrogen receptor 58%. Cadmium induced a parallel decrease in estrogen receptor mRNA (62%). Progesterone receptor levels increased 3.2-fold after cadmium treatment. This induction was blocked by the anti-estrogen ICI-164,384. Progesterone receptor mRNA was also increased by cadmium, as well as cathepsin D mRNA. An in vitro nuclear transcription run-on assay showed that cadmium increased the transcription of the progesterone receptor and pS2 genes and decreased transcription of the estrogen receptor gene. These are not general effects of heavy metals, as zinc, 25 and 100 microM, did not affect progesterone receptor protein and mRNA levels. Cadmium stimulated pS2 and progesterone receptor mRNAs in a clone of MDA-MB-231 cells transfected with the human estrogen receptor, but had no effect in MDA-MB-231 cells transfected with antisense estrogen receptor. Cadmium also stimulated an estrogen response element in transient transfection experiments. These data suggest that the effects of cadmium are mediated by the estrogen receptor independent of estradiol. In addition to its effect on gene expression, cadmium induced the growth of MCF-7 cells 5.6-fold.
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PMID:Effect of cadmium on estrogen receptor levels and estrogen-induced responses in human breast cancer cells. 820 12

The estrogenic action of some persistent organochlorine pesticide residues may play a role in the progression of hormonally responsive tumors of the breast and uterus. The prototypical xenoestrogen o,p'-dichlorodiphenyltrichloroethane (o,p'-DDT) acts by binding and activating the estrogen receptor (ER). The present study focuses attention on the mechanisms through which another organochlorine compound, beta-hexachlorocyclohexane (beta-HCH), exerts estrogen-like effects in human breast cancer cells. Both o,p'DDT and beta-HCH stimulated proliferation in a dose-dependent manner in the ER-positive cell lines MCF-7 and T47D but not in the ER-negative lines MDA-MB231, MDA-MB468, and HS578T. Both compounds produced an increase in the steady state level of pS2 mRNA in MCF-7 cells. These responses were equal in magnitude to the maximal effect of estradiol, and they were inhibited by inclusion of the antiestrogen ICI164384. On the other hand, when tested in a competitive binding assay, beta-HCH did not displace 17beta-[3H]estradiol from the ER even at a concentration that was 40,000-fold higher than the tracer steroid. Furthermore, nuclear retention of the ER during homogenization procedures was induced by a 2- or 24-h treatment of MCF-7 cells with o,p'-DDT and 17beta-estradiol but not by treatment with beta-HCH; this indicates that beta-HCH nether activates the ER, nor is it converted intracellularly to an ER ligand. Transcriptional activation by beta-HCH occurs in estrogen-responsive GH3 rat pituitary tumor cells transfected with a luciferase reporter construct driven by a complex 2500-bp portion of the PRL gene promoter; this trans-activation response is inhibited by inclusion of ICI164384. However, beta-HCH is ineffective in stimulating a reporter construct driven only by a consensus estrogen response element and a minimal promoter derived from the herpes simplex virus thymidine kinase gene. Thus, beta-HCH cannot act on a simple, single estrogen response element; rather, it requires the combinatorial regulation found in a complex promoter. These data are consistent with the notion that beta-HCH stimulation of cell proliferation and gene expression is ER dependent, but its action is not through the classic pathway of binding and activating the ER. beta-HCH may represent a new class of xenobiotic that produces estrogen-like effects through nonclassic mechanisms and, therefore, may be of concern with regard to breast and uterine cancer risk.
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PMID:Novel estrogenic action of the pesticide residue beta-hexachlorocyclohexane in human breast cancer cells. 896 93

Toxaphene (polychlorinated camphenes) is an insecticidal mixture of >670 chemicals, which was widely used until the mid 1980s. Due to their lipophilic and volatile nature, these chemicals accumulate in animal and human tissues and continue to be a major contaminant in marine and freshwater biota. Cytotoxic and genotoxic effects in mammalian test systems suggest that toxaphene is a carcinogen and reports support the hypothesis that toxaphene could have tumor-promoting potential in human breast tissue. In order to examine the potential of toxaphene as an environmental endocrine disrupter, we investigated its effect on the estrogen receptor (ER) function in human breast cancer MCF-7 cells. Using transient gene expression experiments, we observed approximately 60% and 80% inhibition of the constitutive and 17beta-estradiol induced ER-dependent transactivation, respectively. The involvement of the ER in the ability of toxaphene to block the estrogen action was verified by cotransfection studies in ER-negative MDA-MB-231 cells. The interference of toxaphene with the ER mediated responses was supported by a significant suppression of endogenously expressed pS2 RNA and decreased levels of secreted pS2 protein. These reproducible results indicate that toxaphene can disturb hormonal signals mediated by the ER and suggest that these environmental chemicals have potential endocrine disrupting activities which may affect the reproductive health and increase the risk of carcinogenesis.
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PMID:Effect of toxaphene on estrogen receptor functions in human breast cancer cells. 927 43

Differences in gene expression are likely to explain the phenotypic differences between hormone-responsive and hormone-unresponsive breast cancer. We have identified differentially expressed cDNAs in the estrogen receptor (ER)-positive MCF7 breast carcinoma cell line compared with the ER-negative MDA-MB-231 breast carcinoma cell line. Differential screening isolated four differentially expressed genes: cytokeratin 8, cytokeratin 18, Hsp27 and GPCR -Br. To identify differentially expressed genes of lower abundance, suppression subtractive hybridization was utilized and 29 differentially expressed clones were isolated. Sequence analysis revealed that 11 clones were from previously described genes: HEK8, neuropeptide Y receptor Y1, p21 WAF-1, p55 PIK, cytokeratin 18 (cloned twice), fructose-1,6-biphosphatase, cytokeratin 8, TGFbeta1 binding protein, elongation factor 1alpha2 and pS2. The remaining 18 clones did not match sequences in the GenBank/EMBL database, indicating that they may be novel genes. Expression of pS2, neuropeptide Y receptor Y1 and three novel clones was induced by estradiol, indicating estrogen-responsiveness. The expression pattern of one novel gene, DEME -6, correlated with expression of ER and ERF -1/ AP -2gamma in a panel of breast carcinoma cell lines. A 2.6 kb cDNA of DEME -6 was sequenced and contains an open reading frame of 574 amino acids that demonstrates 62.4% similarity with a gene from Caenorhabditis elegans chromosome III. Expression of DEME -6 was also detected in primary breast carcinomas but not in normal breast tissue, as determined by RT-PCR. These findings support the hypothesis that a set of genes coordinately regulated with ER , but not necessarily estradiol-responsive, are characteristic of the hormone-responsive breast cancer phenotype.
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PMID:Differential screening and suppression subtractive hybridization identified genes differentially expressed in an estrogen receptor-positive breast carcinoma cell line. 946 76

It has recently been suggested that mutation of a conserved tyrosine to asparagine within the ligand-binding domain of the estrogen receptor (ER) alpha confers hormone-independent activation and insensitivity to antiestrogens (Q. X. Zhang et al., Cancer Res., 57: 1244-1249, 1997). In view of the recent discovery of ERbeta and the development of the novel nonsteroidal antiestrogen EM-800 and its active metabolite EM-652, we decided to reexamine this issue by introducing a series of mutations at the conserved tyrosine 537 in ERalpha and 443 in ERbeta and measuring their transcriptional activity in the absence and presence of estradiol and the antiestrogens EM-652, ICI 182,780, and 4-hydroxytamoxifen. As demonstrated previously for ERalpha, we observed that substituting a serine or asparagine but not a phenylalanine for the conserved tyrosine 443 in ERbeta confers constitutive transcriptional activity to the receptor. This activity was apparent on both the vitA2-ERE and the pS2 promoters in Cos-1 and HeLa cell lines as well as the human breast cancer cell line MDA-MB-231. However, the ligand-independent transcriptional activity of all ERalpha and ERbeta mutants examined, including the tyrosine to asparagine substitutions, was completely abolished by the three antiestrogens tested in this system. Furthermore, hormone-independent interaction of ERalpha and ERbeta mutant receptors with the steroid receptor coactivator-1 was abrogated by these antiestrogens. Our report, therefore, indicates that antiestrogens would be effective agents against constitutively active tyrosine ERalpha and ERbeta mutants and suggests that this particular type of modified receptors are unlikely to contribute to resistance toward antiestrogens in breast cancer therapy.
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PMID:Ligand-independent activation of the estrogen receptors alpha and beta by mutations of a conserved tyrosine can be abolished by antiestrogens. 950 Apr 42

Potential antiproliferative effects of tocotrienols, the major vitamin E component in palm oil, were investigated on the growth of both estrogen-responsive (ER+) MCF7 human breast cancer cells and estrogen-unresponsive (ER-) MDA-MB-231 human breast cancer cells, and effects were compared with those of alpha-tocopherol (alphaT). The tocotrienol-rich fraction (TRF) of palm oil inhibited growth of MCF7 cells in both the presence and absence of estradiol with a nonlinear dose-response but such that complete suppression of growth was achieved at 8 microg/mL. MDA-MB-231 cells were also inhibited by TRF but with a linear dose-response such that 20 microg/mL TRF was needed for complete growth suppression. Separation of the TRF into individual tocotrienols revealed that all fractions could inhibit growth of both ER+ and ER- cells and of ER+ cells in both the presence and absence of estradiol. However, the gamma- and delta-fractions were the most inhibitory. Complete inhibition of MCF7 cell growth was achieved at 6 microg/mL of gamma-tocotrienol/delta-tocotrienol (gammaT3/deltaT3) in the absence of estradiol and 10 microg/mL of deltaT3 in the presence of estradiol, whereas complete suppression of MDA-MB-231 cell growth was not achieved even at concentrations of 10 microg/mL of deltaT3. By contrast to these inhibitory effects of tocotrienols, alphaT had no inhibitory effect on MCF7 cell growth in either the presence or the absence of estradiol, nor on MDA-MB-231 cell growth. These results confirm studies using other sublines of human breast cancer cells and demonstrate that tocotrienols can exert direct inhibitory effects on the growth of breast cancer cells. In searching for the mechanism of inhibition, studies of the effects of TRF on estrogen-regulated pS2 gene expression in MCF7 cells showed that tocotrienols do not act via an estrogen receptor-mediated pathway and must therefore act differently from estrogen antagonists. Furthermore, tocotrienols did not increase levels of growth-inhibitory insulin-like growth factor binding proteins (IGFBP) in MCF7 cells, implying also a different mechanism from that proposed for retinoic acid inhibition of estrogen-responsive breast cancer cell growth. Inhibition of the growth of breast cancer cells by tocotrienols could have important clinical implications not only because tocotrienols are able to inhibit the growth of both ER+ and ER- phenotypes but also because ER+ cells could be growth-inhibited in the presence as well as in the absence of estradiol. Future clinical applications of TRF could come from potential growth suppression of ER+ breast cancer cells otherwise resistant to growth inhibition by antiestrogens and retinoic acid.
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PMID:Tocotrienols inhibit the growth of human breast cancer cells irrespective of estrogen receptor status. 962 93


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