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)

Comparison of mRNA ratios of a non-DNA-binding estrogen receptor (ER(alpha)) isoform, missing exon 3 (ER(alpha)delta3), to the full-length ER(alpha), in normal breast epithelium to that in primary breast cancers and breast cancer cell lines revealed a 30-fold reduction of this ratio in cancer cells (P < 0.0001). To test what functions may have been affected by the loss of ER(alpha)delta3, stable clones of MCF-7 cells expressing ectopic ER(alpha)delta3 protein, at the range of physiological ER(alpha), were generated. In vector-transfected controls the ER(alpha)delta3-mRNA and protein were less than 10% while in the ER(alpha)delta3-expressing clones, ER(alpha)delta3-mRNA and protein ranged from 36-76% of the total ER(alpha). Estrogen (E2) stimulated the expression of pS2-mRNA in pMV7 vector control cells, but the stimulation was reduced by up to 93% in ER(alpha)delta3-expressing clones. In addition, several properties associated with the transformed phenotype were also strongly affected when ER(alpha)delta3 protein was reexpressed. Compared with vector-transfected control cells, the saturation density of the ER(alpha)delta3-expressing clones was reduced by 50-68%, while their exponential growth rate was only slightly (14.5 +/- 5%) lower. The in vivo invasiveness of the ER(alpha)delta3-expressing cells was significantly reduced (P = 0.007) by up to 79%. E2 stimulated anchorage-independent growth of the pMV7 vector control cells, but reduced it to below baseline levels in ER(alpha)delta3 clones. The reduction of the pS2 response to E2 in the ER(alpha)delta3-expressing clones and the E2 block of anchorage-independent growth to below baseline were more pronounced than expected from the dominant negative function of ER(alpha)delta3. These observations suggest that E2 may activate an additional ER(alpha)delta3-dependent inhibitory pathway. The drastic reduction of ER(alpha)delta3 to ER(alpha) ratio in breast cancer, and the fact that when present in breast cancer cells this isoform leads to a suppression, rather than enhancement, of the transformed phenotype by E2 suggests that the regulation of ER(alpha)-mRNA splicing may need to be altered for the breast carcinogenesis to proceed.
Mol Endocrinol 1997 Dec
PMID:Loss of an estrogen receptor isoform (ER alpha delta 3) in breast cancer and the consequences of its reexpression: interference with estrogen-stimulated properties of malignant transformation. 941 4

The unique structure in which six cysteine residues in a sequence of 38 or 39 amino acid residues form three disulphide bonds in a 1-5, 2-4 and 3-6 configuration constitutes the basic elements of a trefoil domain. Today three mammalian trefoil factors (TFF1, TFF2 and TFF3) containing one or two trefoil domains are known. Trefoil factors are usually associated with the mucin layer of the gastrointestinal tract. Early studies on trefoil factors concentrated on structure elucidation and sites of expression in health and disease, whereas studies over the last 3-5 years have focused on the mechanism of action and the search for specific receptors. This review summarises our present knowledge of trefoil peptide structures, their sites of expression, and their protection and repair functions, with a focus on the mechanism by which these peptides exert their biological function.
Cell Mol Life Sci 1997 Dec
PMID:Trefoil peptides: from structure to function. 944 40

Estrogen (E) inhibits the growth of both non-tumorigenic, immortal human mammary epithelial cells (HMEC) and breast cancer cells which stably express exogenous estrogen receptors (ER). The anti-estrogenic compounds 4-hydroxy-tamoxifen (HT) and ICI 164384 (ICI) have different effects on the growth of the ER-transfectants. HT is a potent growth inhibitor, while ICI has no effect by itself but is able to block the anti-proliferative effects of E and HT. In order to elucidate the mechanism by which E or HT-bound ER inhibit cell growth, we have evaluated the effects of these compounds on the growth of HMEC stably expressing ER with mutations or deletions in the N-terminal A/B domain, the DNA-binding domain (DBD), and the C-terminal ligand-binding domain. These studies revealed that E and HT require different structural domains of the ER for their anti-proliferative activities. The N-terminal A/B domain is required for HT-, but not E-dependent growth inhibition. The DNA-binding domain of the ER is not essential for HT-mediated anti-proliferative effects, but is important for E-dependent activity. The effect of ER mutations on the ligand-inducible expression of the endogenous progesterone receptor (PR) and pS2 genes was also evaluated. Neither gene was induced in the cells containing the ER mutated in the DBD, even though cell growth was inhibited. These results suggest that E and HT use different pathways to elicit their anti-proliferative effects and that this occurs via modulation of genes that are controlled by mechanisms different from those important for activation of the PR and pS2 genes.
J Steroid Biochem Mol Biol 1997 Aug
PMID:Different estrogen receptor structural domains are required for estrogen- and tamoxifen-dependent anti-proliferative activity in human mammary epithelial cells expressing an exogenous estrogen receptor. 944 40

A novel estrogen receptor mRNA splice variant which lacks the entire exon 5 and part of exon 4 and 6 was identified using reverse transcription PCR in human breast carcinomas. The variant was translated in vitro and produced a protein of approximately Mr 31000 which lacked the ligand binding domain. The binding of the variant estrogen receptor (ER) to a synthetic estrogen-responsive element (ERE) was compared with that of the wild-type ER (wtER). The variant ER bound weakly to the synthetic ERE, both in the presence and absence of estradiol, whilst the wtER bound strongly in the absence and the presence of estradiol. When wtER and variant ER were simultaneously translated in vitro, no heterodimerization was observed using band shift assay. Addition of increasing amounts of variant ER protein to the wtER in the ERE binding reaction showed that the variant protein competed with the binding of the wtER to the synthetic ERE. Furthermore, variant ER are not transcriptionally active. The variant was also expressed in 96% of the 102 breast tumours analysed, of which 62 were tamoxifen-resistant tumours. The expression of this variant was significantly higher (relative to ER) in untreated ER-positive breast tumours which were both progesterone receptor (PgR) negative and pS2 negative phenotype.
J Steroid Biochem Mol Biol 1997 Aug
PMID:A novel estrogen receptor variant mRNA lacking exons 4 to 6 in breast carcinoma. 944 45

The estrogen receptor (ER) is a ligand-dependent transcription factor that regulates the expression of estrogen-responsive genes. ER-mediated transcriptional changes are brought about by interaction of the ER with the estrogen response element (ERE). In this study, we examined the interaction of the Xenopus laevis ER DNA binding domain (DBD) and the intact ER with the X. laevis vitellogenin A2 ERE and the human pS2 ERE. Using gel mobility shift, DNase I footprinting, and methylation interference assays, we demonstrated that the DBD bound only as a dimer to the A2 ERE. However, the DBD bound as a monomer to the consensus pS2 ERE half site at lower DBD concentrations and then as a homodimer to the consensus and imperfect pS2 ERE half site at higher DBD concentrations. Antibody supershift experiments carried out with partially purified, yeast-expressed full-length ER demonstrated that three ER-specific antibodies interacted differentially with A2 and pS2 ERE-bound ER, indicating that receptor epitopes were differentially exposed. Furthermore, partial digestion of the A2 and pS2 ERE-bound ER with chymotrypsin or trypsin produced distinct protease cleavage patterns. Taken together, these data provide evidence that differential interaction of the DBD with the A2 and pS2 EREs brings about global changes in ER conformation. The conformational changes in ER induced by individual ERE sequences could lead to association of the receptor with different transcription factors and assist in the differential modulation of estrogen-responsive genes in target cells.
Mol Cell Biol 1998 Apr
PMID:Estrogen response elements function as allosteric modulators of estrogen receptor conformation. 952 64

Alterations in the expression of the breast and ovarian cancer susceptibility gene BRCA1 may contribute to the development of mammary and ovarian neoplasia. The sex-steroid estrogen modulates cell proliferation of normal and neoplastic breast and ovarian epithelial cells, but the role of estrogen regulation on the expression of BRCA1 remains to be defined. In this study, estrogen-regulated BRCA1 expression was examined in breast and ovarian cancer cells. Estrogen stimulated the proliferation of estrogen receptor (ER)-positive breast MCF-7, C7-MCF-7, and ovarian BG-1 cells as well as the expression of the estrogen-inducible pS2 gene. This was concomitant with upregulation of BRCA1 mRNA (2.5- to 5.0-fold) and a 3- to 10-fold induction of BRCA1 protein (230 kDa). Cell fractionation studies localized the BRCA1 protein to the nucleus in both unstimulated and estrogen-stimulated cells. The antiestrogen ICI-182780 inhibited estrogen-induced cell proliferation, BRCA1 mRNA induction, and BRCA1 protein expression in ER-positive cells. Conversely, estrogen did not influence expression of BRCA1 in HBL-100 cells that lacked the estrogen receptor, although the constitutive levels of BRCA1 mRNA (but not protein) in these cells were 5- to 30-fold higher than in other breast and ovarian cancer cells. Secretion of the BRCA1 protein into the cell medium did not account for the discrepancy between the mRNA and protein levels in HBL-100 cells. Proliferation of HBL-100 cells was not affected by either estrogen or ICI-182780. Taken together, these data support a role for the steroid estrogen and the involvement of the estrogen receptor pathway in the modulation of expression of BRCA1. We therefore propose that stimulation of cell proliferation may be a prerequisite for upregulation of BRCA1 in breast and ovarian cancer cells.
Mol Carcinog 1998 Jun
PMID:Estrogen upregulation of BRCA1 expression with no effect on localization. 965 54

Estrogen receptor (ER)-negative breast carcinomas are often difficult to treat as they do not respond to hormone therapy. In an attempt to determine if expressing the human estrogen receptor in an ectopic manner could restore the hormone responsiveness of these cells, we have expressed the human ER in ER-negative MDA-MB 231 breast cancer cells using a recombinant adenovirus gene delivery system that allows high level expression of ER in essentially all cells. In these cells, the ER was correctly translated, had a wild type hormone binding affinity (Kd = 0.6 nM), bound well to estrogen response element-containing DNA, and showed an activation pattern of estrogen response element-reporter gene activity by estrogen and antiestrogens very similar to that observed in MCF-7 breast cancer cells containing endogenous ER (stimulation by estrogen, no stimulation by the antiestrogens trans-hydroxytamoxifen or ICI 164384, and blockade of estradiol stimulation by trans-hydroxytamoxifen or ICI 164384). Intriguingly, estradiol stimulation of these cells was also able to induce expression of pS2, an estrogen regulated gene considered to be a favorable prognostic marker for endocrine therapy in ER-positive breast cancer cells. Expression of the ER had no effect by itself on the proliferation rate of MDA-MB 231 cells. However, treatment of the ER-containing cells with estradiol or with the pure antiestrogen ICI 164 384 suppressed proliferation of the cells while the antiestrogen trans-hydroxytamoxifen had little effect on proliferation; and cotreatment with trans-hydroxytamoxifen reversed the estradiol- or ICI 164 384-evoked suppression of proliferation. To understand the mechanism underlying the inhibition of proliferation by estradiol, we examined the expression of several growth related endogenous genes. c-Myc protooncogene expression was strongly inhibited by treatment with estradiol as was expression of BRCA1 and BRCA2 genes, which is in agreement with their mitogenic-dependent expression, while expression of beta-actin, a housekeeping gene, was not affected by hormone treatment. Together, these data suggest that reexpressing the human ER in breast cancer cells that no longer express this protein renders them sensitive to hormone treatment. The ability of the antiestrogen ICI 164 384 to suppress the proliferation of ER-negative breast cancer cells that reexpress ER might be useful ultimately as an endocrine gene therapy approach for controlling the growth of ER-negative breast cancer cells. The application of recombinant adenoviruses expressing the human ER presents interesting features which might be used as a basis for designing more powerful and effective treatments for ER-negative breast cancers.
Mol Cell Endocrinol 1999 Mar 25
PMID:Expression of human estrogen receptor using an efficient adenoviral gene delivery system is able to restore hormone-dependent features to estrogen receptor-negative breast carcinoma cells. 1037 22

Dominant negative estrogen receptors are transcriptionally inactive, altered forms of the estrogen receptor (ER) that can dimerize with the ER and have the potential to inactivate the biological functions of this receptor. Here, we provide the first report that adenoviral delivery of a dominant negative ER to ER-positive breast cancer cells is able to effectively suppress estrogen-stimulated cell proliferation and the hormonal induction of endogenous genes. We constructed recombinant adenoviral vectors expressing a dominant negative ER (S554 fs, Ad-fs) or, for comparison, antisense ER (Ad-AS), or the sense wild-type ER (Ad-WT). Expression of the dominant negative ER or antisense ER, but not wild-type ER, blocked estradiol stimulation of the estrogen-responsive genes pS2 and c-myc. The dominant negative ER also fully abolished the estradiol-induced increase in proliferation of MCF-7 breast cancer cells, as did the antisense ER. The antiproliferative effects of the dominant negative and antisense ERs are explained by an increase in the number of cells in the G0/G1 stage of the cell cycle and decrease in the number of cells in G2/M as determined by flow cytometry, and also by a significant increase in the percentage of cells undergoing apoptosis. Our data strongly support the idea that targeting ER action using recombinant viral delivery of dominant negative ERs is an effective way to suppress ER-positive breast cancer cell proliferation and suggests the potential attractiveness of dominant negative gene therapy approaches targeted to the ER for the treatment of hormone-responsive breast cancer.
Mol Endocrinol 1999 Jun
PMID:Adenovirus-mediated delivery of a dominant negative estrogen receptor gene abrogates estrogen-stimulated gene expression and breast cancer cell proliferation. 1037 95

To determine the molecular mechanisms underlying the "cross talk" between the activity of 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD), which binds to arylhydrocarbon receptor (AHR) and estradiol (E2)-liganded estrogen receptor (ER), we first examined the initial step of estrogen action, ligand binding to ER. None of the AHR ligands tested, i.e. TCDD, benzo[a]pyrene, 3,3',4,4',5-pentachlorobiphenyl, beta-naphthoflavone, or alpha-naphthoflavone, bound to ER alpha. We report the first examination of TCDD interaction with ER beta: TCDD did not displace E2 from ER beta. We then examined a second possible mechanism, i.e. direct inhibition of ER alpha binding to estrogen response elements (EREs) by the AHR/AHR nuclear translocator (ARNT) complex. The AHR/ARNT heterodimer did not bind either a full or half-site ERE. However, AHR/ARNT bound specifically to oligomers containing naturally occurring EREs derived from the human c-fos, pS2, and progesterone receptor (PR) gene promoters that include xenobiotic response element (XRE)-like sequences. In contrast, neither purified E2-liganded-ER from calf uterus or recombinant human ER alpha bound a consensus XRE. TCDD inhibited E2-activated reporter gene activity from a consensus ERE and from EREs in the pS2, PR, and Fos genes in transiently transfected MCF-7 human breast cancer cells. However, this inhibition was not reciprocal since E2 did not inhibit TCDD-stimulated luciferase activity from the CYP1A1 promoter in transiently transfected MCF-7 or human endometrial carcinoma HEC-1A cells. We propose that at least part of the mechanism by which the AHR/ARNT complex inhibits estrogen action is by competitively inhibiting ER alpha binding to imperfect ERE sites, adjacent to or overlapping XREs.
Mol Cell Endocrinol 1999 Nov 25
PMID:The aryl hydrocarbon receptor (AHR)/AHR nuclear translocator (ARNT) heterodimer interacts with naturally occurring estrogen response elements. 1061 2

Local estradiol production within breast tissue is maintained by the aromatase cytochrome P450arom complex, which has been localized primarily to the stromal component of tumors but also has been detected in the breast epithelial cells. Paracrine interactions between stromal and epithelial components of the breast are critical to the sustained growth and progression of breast tumors. Maintenance of the differentiated state, including hormone and growth factor responsiveness, requires extracellular matrix proteins as substrata for cells. This research has focused on developing a cell culture system that more closely mimics in vivo interactions in order to dissect actual paracrine signaling between these two cell types. Human fibroblasts were isolated from breast tissue and were maintained in a cell culture system grown on plastic support or on a collagen I support matrix. The collagen I matrix model supports cell maintenance and subsequent differentiation on collagen rather than maximal proliferation, therefore allowing for a more accurate environment for the study of hormonal control and cellular communication. Initial experiments compared aromatase activity of patient fibroblasts grown on plastic versus collagen I using the tritiated water release method. Constitutive aromatase activity was found to be lower when cells were grown on a collagen gel for 4-7 days (7.7 fold lower) using DMEM/F12 containing 10% dextran coated charcoal stripped serum. However, fibroblasts grown on collagen I appeared to be significantly more responsive to stimulation by 100 nM dexamethasone (plastic: 6.0 fold induction, collagen: 33.2 fold induction) when pretreated for 12 h prior to measurement of aromatase activity. In an effort to examine paracrine interactions between the stromal and epithelial cells in breast tissue, experiments using conditioned media from fibroblast cultures were performed. Testosterone administration to fibroblasts results in the production of estradiol into the media in sufficient concentrations to elicit an increase in pS2 expression when the conditioned media is administered to MCF-7 cells. The addition of a potent aromatase inhibitor resulted in a complete suppression of fibroblast-derived estrogens and showed only a modest increase in pS2 expression. Culturing breast fibroblasts and epithelial cells on extracellular matrix allows for a more meaningful examination of the paracrine interactions between these cell types within the context of an appropriate extracellular environment. This study highlights the need for evaluation of gene expression in cell culture systems that accurately reflect the tissue microenvironment.
J Steroid Biochem Mol Biol
PMID:Effects of matrix components on aromatase activity in breast stromal cells in culture. 1062 15


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