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Query: UNIPROT:P04155 (pS2)
 1,234 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To understand better the antiestrogen-resistant phenotype that frequently develops in breast cancer patients receiving tamoxifen, we cultured MCF-7 breast cancer cells long-term (>1 yr) in the presence of the antiestrogen trans-hydroxytamoxifen (TOT) to generate a subline refractory to the growth-suppressive effects of TOT. This subline (designated MCF/TOT) showed growth stimulation, rather than inhibition, with TOT and diminished growth stimulation with estradiol (E2), yet remained as sensitive as the parental cells to growth suppression by another antiestrogen, ICI 164,384. Estrogen receptor (ER) levels were maintained at 40% of that in parent MCF-7 cells, but MCF/TOT cells failed to show an increase in progesterone receptor content in response to E2 or TOT treatment. In contrast, the MCF/TOT subline behaved like parental cells in terms of E2 and TOT regulation of ER and pS2 expression and transactivation of a transiently transfected estrogen-responsive gene construct. DNA sequencing of the hormone binding domain of the ER from both MCF-7 and MCF/TOT cells confirmed the presence of wild-type ER and exon 5 and exon 7 deletion splice variants, but showed no point mutations. Compared to the parental cells, the MCF/TOT subline showed reduced sensitivity to the growth-suppressive effects of retinoic acid and complete resistance to exogenous TGF-beta1. The altered growth responsiveness of MCF/TOT cells to TOT and TGF-beta1 was partly to fully reversible following TOT withdrawal for 16 weeks. Our findings underscore the fact that antiestrogen resistance is response-specific; that loss of growth suppression by TOT appears to be due to the acquisition of weak growth stimulation; and that resistance to TOT does not mean global resistance to other more pure antiestrogens such as ICI 164,384, implying that these antiestrogens must act by somewhat different mechanisms. The association of reduced retinoic acid responsiveness and insensitivity to exogenous TGF-beta with antiestrogen growth resistance in these cells supports the increasing evidence for interrelationships among cell regulatory pathways utilized by these three growth-suppressive agents in breast cancer cells. In addition, our findings indicate that one mechanism of antiestrogen resistance, as seen in MCF/TOT cells, may involve alterations in growth factor and other hormonal pathways that affect the ER response pathway.
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PMID:Response-specific antiestrogen resistance in a newly characterized MCF-7 human breast cancer cell line resulting from long-term exposure to trans-hydroxytamoxifen. 901 Mar 27

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.
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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

Estrogen receptor (ER), progesterone receptor (PR), the estrogen-inducible protein pS2, and plasminogen activator inhibitor-1 (PAI-1) are important prognostic factors in primary breast cancer. The protein concentrations of these factors in breast tumors have been well documented. However, few data about the mRNA expression of ER, PR, pS2, and PAI-1 in breast cancer are available, which is mostly due to the limitations of conventional techniques for mRNA analysis. We have described a competitive reverse transcription-PCR system for the simultaneous quantification of ER, PR, pS2, and PAI-1 mRNA in tumor samples. Here, we evaluated 100 tumor biopsies from breast cancer patients for the mRNA expression of ER, PR, pS2, and PAI-1. The results were analyzed for correlations with protein status and with clinical data. Significant correlations between mRNA expression levels and protein concentrations of all tested markers were found. In only a few cases was there an obvious discordance between the measurable amounts of mRNA and protein, especially for ER and PR. In addition, ER, PR, and pS2 mRNA levels correlated significantly with each other. No correlation between PAI-1 mRNA amount and the expression of the other markers was found. With respect to clinical data, ER and PR mRNA levels were found to be inversely correlated to tumor size and histological grade but not to the lymph node status. pS2 and PAI-1 mRNA expression were not correlated with tumor size, grade, or lymph node involvement. In conclusion, competitive reverse transcription-PCR may be used as an alternative for the study of prognostic factors in human breast cancer and other malignancies. However, before mRNA expression is measured for diagnostics, a presumed concordance of mRNA and protein expression must be evaluated very carefully for every gene.
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PMID:Messenger RNA determination of estrogen receptor, progesterone receptor, pS2, and plasminogen activator inhibitor-1 by competitive reverse transcription-polymerase chain reaction in human breast cancer. 1038 38

To evaluate the prognostic relevance of Ki-67 and topoisomerase IIalpha expression in relation to tumor stage, grade, and hormone receptor content, 942 ductal infiltrating carcinomas of the breast were examined by means of the monoclonal antibodies Ki-S11 (Ki-67) and Ki-S4 (topoisomerase IIalpha). pS2, c-erbB2, and p53 were additionally considered as prognostic variables. The median follow-up time was 149 months. Eight-hundred-and-sixty-three tumors reacted with Ki-S11 and Ki-S4; the labeling indices of the two antigens were closely associated (r = 0.93). Both correlated positively with the tumor size, c-erbB2, and p53 expression, and negatively with patient age, hormone receptor content, and pS2 immunostaining. In the univariate analysis, Ki-S11 and Ki-S4 scores, nodal status, tumor size, tumor grade, and progesterone receptor content strongly predicted both overall and metastasis-free survival (p < 0.00001). Estrogen receptor status, p53, and c-erbB2 were of minor significance. Concerning overall survival, multivariate Cox regression analysis selected a Ki-S4 score >25% (p < 0.00001) next to the nodal status, and before tumor size, progesterone receptor content, and patient age. Independent predictors of the occurrence of distant metastases were nodal status, Ki-S4, tumor size, grade 1, and progesterone receptor negativity, in that order. The Ki-S11 score was of independent prognostic significance only if examined as a continuous variable. We conclude that topoisomerase IIalpha expression as assessed by monoclonal antibody Ki-S4 may add valuable information to current prognostic models for breast cancer. Its predictive value appears to be essentially related to the proliferative activity of tumor cells.
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PMID:Prognostic significance of Ki-67 and topoisomerase IIalpha expression in infiltrating ductal carcinoma of the breast. A multivariate analysis of 863 cases. 1047 80

Breast cancer screening is important for the early detection of breast cancer. Tumors that become symptomatic in the screening interval are known as interval cancers but the reasons for their rapid progression are unknown. Estrogen receptor expression is lower in interval cancers suggesting that they may have reduced hormonal responsiveness. To investigate this hypothesis we have measured the expression of the estrogen receptor and three estrogen-responsive genes (cathepsin D, progesterone receptor, and TFF1) in screen-detected and interval breast cancers. The expression of the protease cathepsin D was not associated with estrogen receptor in either group of tumor. Progesterone receptor expression was highly correlated with that of the estrogen receptor in both groups of tumors but it was not expressed at significantly different levels in the two groups of tumors. Expression of TFF1, a cellular motogen, was correlated with estrogen receptor in screen-detected but not interval cancers and was expressed at markedly higher levels in interval breast tumors, the group that expresses lower levels of estrogen receptor. Interval cancers are characterized by high levels of expression of TFF1 and/or Ki67 suggesting that cell migration and cell division play important roles in the rapid progression of interval cancers. The observation that TFF1 expression in interval cancers tends to be estrogen-independent and that interval cancers have reduced estrogen receptor expression suggests they may have a reduced response to hormone therapy.
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PMID:High expression of the trefoil protein TFF1 in interval breast cancers. 1143 68

Estrogen receptor-alpha (ER alpha) is a ligand-dependent transcription factor that mediates physiological responses to 17 beta-estradiol (E2). Ligand binding rapidly down-regulates ER alpha levels through proteasomal proteolysis, but the functional impact of receptor degradation on cellular responses to E2 has not been fully established. In this study, we investigated the effect of blocking the ubiquitin-proteasome pathway on ER alpha-mediated transcriptional responses. In HeLa cells transfected with ER alpha, blocking either ubiquitination or proteasomal degradation markedly increased E2-induced expression of an ER-responsive reporter. Time course studies further demonstrated that blocking ligand-induced degradation of ER alpha resulted in prolonged stimulation of ER-responsive gene transcription. In breast cancer MCF7 cells containing endogenous ER alpha, proteasome inhibition enhanced E2-induced expression of endogenous pS2 and cathepsin D. However, inhibiting the proteasome decreased expression of progesterone receptor (PR), presumably due to the heterogeneity of the PR promoter, which contains multiple regulatory elements. In addition, in endometrial cancer Ishikawa cells overexpressing steroid receptor coactivator 1, 4-hydroxytamoxifen displayed full agonist activity and stimulated ER alpha-mediated transcription without inducing receptor degradation. Collectively, these results demonstrate that proteasomal degradation is not essential for ER alpha transcriptional activity and functions to limit E2-induced transcriptional output. The results further indicate that promoter context must be considered when evaluating the relationship between ER alpha transcription and proteasome inhibition. We suggest that the transcription of a gene driven predominantly by an estrogen-responsive element, such as pS2, is a more reliable indicator of ER alpha transcription activity than a gene like PR, which contains a complex promoter requiring cooperation between ER alpha and other transcription factors.
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PMID:Inhibiting proteasomal proteolysis sustains estrogen receptor-alpha activation. 1528 35

Estrogen receptor-alpha (ERalpha) is a member of the nuclear receptor superfamily of ligand-activated transcription factors. Abundant evidence demonstrates that ERalpha agonists promote, whereas antagonists inhibit, receptor binding to coactivators. In this report we demonstrate that binding of the ICI 182,780 (ICI) pure antiestrogen to ERalpha promotes its interaction with the cAMP response element-binding protein-binding protein (CBP)/p300 but not the p160 family of coactivators, demonstrating the specificity of this interaction. Amino acid mutations within the coactivator binding surface of the ERalpha ligand-binding domain revealed that CBP binds to this region of the ICI-liganded receptor. The carboxy-terminal cysteine-histidine rich domain 3 of CBP, rather than its amino-terminal nuclear interacting domain, shown previously to mediate agonist-dependent interactions of CBP with nuclear receptors, is required for binding to ICI-liganded ERalpha. Chromatin immunoprecipitation assays revealed that ICI but not the partial agonist/antagonist 4-hydroxytamoxifen is able to recruit CBP to the pS2 promoter, and this distinguishes ICI from this class of antiestrogens. Chromatin immunoprecipitation assays for pS2 and cytochrome P450 1B1 promoter regions revealed that ICI-dependent recruitment of CBP, but not receptor, to ERalpha targets is gene specific. ICI treatment did not recruit the steroid receptor coactivator 1 to the pS2 promoter, and it failed to induce the expression of this gene. Taken together, these data indicate that recruitment of the CBP coactivator/cointegrator without steroid receptor coactivator 1 to ERalpha is insufficient to promote transcription of ERalpha target genes.
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PMID:The pure estrogen receptor antagonist ICI 182,780 promotes a novel interaction of estrogen receptor-alpha with the 3',5'-cyclic adenosine monophosphate response element-binding protein-binding protein/p300 coactivators. 1684 May 38

Estrogen receptor (ER), one member of nuclear hormone receptor (NR) family, is an estrogen-dependent transcriptional factor that plays an important role in development, progression and treatment of breast cancer. Transcriptional co-factors (co-activators and co-repressors) are critical for ER to transduce hormone and metabolic signaling to target genes. A number of functional and structural studies have elucidated the precise mechanisms of co-activator interaction with the ligand-inducible activation domain in ER via one and several LXXLL motifs (where X is any amino acid) known as NR-Box. By the yeast two-hybrid system we have identified a novel ER-alpha interacting protein ERIAP (Estrogen Receptor Interacting and Activating Protein) which contains two consensus LXXLL motifs. ERIAP associated with ER-alpha in a ligand-dependent manner, as demonstrated by in vivo immunoprecipitation and in vitro GST capture assays. The two NR boxes were essential for ERIAP interaction with ER-alpha. Furthermore, ERIAP specifically enhanced ligand-mediated ER-alpha transcriptional activity in a dose-dependent fasion and increased the expression of estrogen-responsive gene pS2. Thus, our present findings indicate that ERIAP functions as a new coactivator for ER-alpha transcriptional activity, which may play an important role in development and progression of breast cancer.
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PMID:Identification and function of coactivator of estrogen receptor: ERIAP. 1944 95

Estrogen receptor-alpha (ERalpha) and its ligand estradiol (E2) has critical roles in breast cancer growth and are key therapeutic targets. In this study, we report a novel dual role of the adenosine A1 receptor (Adora1) as an E2/ERalpha target and a regulator of ERalpha transcriptional activity. In ERalpha-positive breast cancer cells, E2 upregulated Adora1 messenger RNA (mRNA) and protein levels, an effect that was reversed by the E2 antagonist ICI 182 780. Small interference RNA ablation of Adora1 in ERalpha-positive cells reduced basal and E2-dependent proliferation, whereas Adora1 over-expression in an ERalpha-negative cell line induced proliferation. The selective Adora1 antagonist, DPCPX, reduced proliferation, establishing Adora1 as a mediator of E2/ERalpha-dependent breast cancer growth. Intriguingly, Adora1 ablation decreased both mRNA and protein levels of ERalpha and, consequently, estrogen-responsive element-dependent ERalpha transcriptional activity. Moreover, Adora1 ablation decreased binding activity of ERalpha to the promoter of its target gene TFF1 and led to reduced TFF1 promoter activity and mRNA levels, suggesting that Adora1 is required for full transcriptional activity of ERalpha on E2 stimulation. Taken together, we showed a short feed-forward loop involving E2, ERalpha and Adora1 that favors breast cancer growth. These data suggest that Adora1 may represent an important target for therapeutic intervention in hormone-dependent breast cancer.
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PMID:Adenosine A1 receptor, a target and regulator of estrogen receptoralpha action, mediates the proliferative effects of estradiol in breast cancer. 1993 20

Estrogen receptor (ER) transcriptional cross-talk after activation by 17beta-estradiol (E2) has been studied in considerable detail, but comparatively little is known about the ways in which synthetic estrogen-like chemicals, so-called xenoestrogens, interfere with these signalling pathways. E2 can stimulate rapid, non-genomic signalling events, such as activation of the Src/Ras/Erk signalling pathway. We investigated how activation of this pathway by E2, the estrogenic environmental contaminants o,p'-DDT, beta-HCH and p,p'-DDE, and epidermal growth factor (EGF) influences the expression of ER target genes, such as TFF1, ER, PR, BRCA1 and CCND1, and the proliferation of breast cancer cells. Despite commonalities in their estrogenicity as judged by cell proliferation assays, the environmental contaminants exhibited striking differences in their non-genomic and genomic signalling. The gene expression profiles of o,p'-DDT and beta-HCH resembled the effects observed with E2. In the case of beta-HCH this is surprising, considering its reported lack of affinity to the "classical" ER. The expression profiles seen with p,p'-DDE showed some similarities with E2, but overall, p,p'-DDE was a fairly weak transcriptional inducer of TFF1, ER, PR, BRCA1 and CCND1. We observed distinct differences in the non-genomic signalling of the tested compounds. p,p'-DDE was unable to stimulate Src and Erk1/Erk2 activations. The effects of E2 on Src and Erk1/Erk2 phosphorylation were transient and weak when compared to EGF, but beta-HCH induced strong and sustained activation of all tested kinases. Transcription of TFF1, ER, PR and BRCA1 by E2, o,p'-DDT and beta-HCH could be suppressed partially by inhibiting the Src/Ras/Erk pathway with PD 98059. However, this was not seen with p,p'-DDE. Our investigations show that the cellular activities of estrogens and xenoestrogens are the result of a combination of extranuclear (non-genomic) and nuclear (genomic) events and highlight the need to take non-genomic effects and signalling cross-talk into consideration, when screening for environmental estrogens. Otherwise, chemicals devoid of ER affinity, such as beta-HCH, but with an effect profile otherwise similar to estrogens might be overlooked in safety testing.
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PMID:Cross-talk between non-genomic and genomic signalling pathways--distinct effect profiles of environmental estrogens. 2020 45


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