Estrogen and antiestrogen interaction with estrogen receptor of MCF-7 cells - Relationship between processing and estrogenicity

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Estrogenic and antiestrogenic down-regulation of estrogen receptor levels: Evidence for two different mechanisms

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A subpopulation of immunoglobulin G in man selectively interacts with the hormone-binding sites of estrogen receptors.

Since the binding sites of hormone receptors may be similar to those of antihormone antibodies, we wondered whether the former might not be recognized by the idiotypic network. To test this hypothesis we investigated the interaction of plasma immunoglobulin G (IgG) with the binding sites of estrogen receptors (ER) from uterine or mammary tissue. Using ER isolated from uterine cytosol we found that IgG from normal subjects shifted the position of purified receptor in sucrose gradients and displaced [3H]estradiol (E2) from its receptor-binding sites. Equilibrium studies revealed competitive inhibition by IgG of E2 binding to the ER. IgG isolated by adsorption on a rat uterine cytosol-Blue B matrix gel column also bound to the ER, and this binding was inhibited by an excess of E2. After an 18-h exposure of MCF-7 mammary carcinoma cells in monolayer culture to IgG (2 mg/ml), Scatchard analysis of [3H]E2 binding revealed a reproducible decrease in the available receptor sites from 2.52 +/- 0.56 (+/- SEM) to 0.68 +/- 0.48 fmol/microgram DNA (n = 10). This effect was selective, since enriched anti-ER IgG obtained by adsorption on purified receptor was 20 times more potent than total IgG, whereas IgG identically prepared but not retained by affinity chromatography had no activity. Exposure of the cells to the IgG for 45 min also revealed, as with isolated ER, specific competition of the IgG with E2 for the E2-binding sites; the Kd increased from 10.5 +/- 1.6 to 27.5 +/- 7.2 X 10(-11) M (n = 7). Enriched antireceptor IgG was a 20 times more effective competitor, and the IgG not retained by affinity chromatography had no activity. In conclusion, our observations indicate the presence of ER on the cell surface, interaction of ER with IgG from plasma of normal subjects, and competitive antagonism of these IgG with E2 uptake leading to a decrease in effective ER concentrations.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Human chorionic gonadotropin-like substance in plasma of normal nonpregnant subjects and women with breast cancer.

To understand ectopic hormone secretion in cancer we compared the plasma concentrations of the hCG-like substance in normal nonpregnant subjects and in women with breast cancer. In 45 normal men the plasma concentrations did not vary with age (median, 5 pg/ml; range, less than 3-169) whereas in 45 normal women they increased after menopause (median, 48 pg/ml; range, less than 5 -569, n = 20, P less than 0.0001). In 56 women with breast cancer the plasma concentrations of the hCG-like substance after menopause were much higher than in normal women (median, 202 pg/ml; range, 14-1561; n = 35; P less than 0.001), with no abnormally high pituitary gonadotropin values and no relationship with the tumor burden (same median after mastectomy, 198 pg/ml; n = 21). This hCG-like substance was glycosylated and similar to standard hCG according to molecular size, ionic strength, and immunoreactivity. Our data are compatible with the following conclusions: 1) the plasma concentration of the hCG-like substance is normally very low but dependent on gonadal function in women. Its source might be the pituitary gland or peripheral tissues. 2) Its concentration is much increased in postmenopausal women with breast carcinoma. This increase is found with normal pituitary gonadotropin values and is independent of the tumor burden, suggesting it is of extrapituitary and nontumoral origin.Comparative StudyJournal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Both IgG and IgM anti-beta2 glycoprotein i antibodies assays are clinically useful to the antiphospholipid syndrome diagnosis

Objectives: The aim of our study was to evaluate the clinical values of anti-beta2 glycoprotein I antibodies (anti-beta2GPI) IgG and IgM comparing with lupus anticoagulant (LA), anticardiolipin antibodies (aCL) in the two clinical groups of antiphospholipid syndrome (APS), vascular thrombosis (VT) and pregnancy morbidity (PM). Methods: Eighty patients who fulfilled the APS clinical criteria, VT n534; PM n540, both VT and PM n56 were included. LA, aCL and three anti-beta2GPI ELISA kits were tested. Results: Sensitivities of LA, aCL and anti-beta2GPI assays were found respectively 62, 26 and 41% in VT, and 28, 28 and 30% in PM. The sensitivity for the APS diagnosis could reach to 63% using triple tests. The presence of LA (P,0.01, OR54.3) or anti-beta2GPI IgG alone (P,0.05, OR58.4) was significantly associated with VT. IgM isotype was found more frequent in PM (92%) than in VT (57%) among all positive anti-beta2GPI cases. Conclusion: Both IgG and IgM anti-beta2GPI assays were useful when clinical features of APS presented, even its standardization is ongoing. A decreased by half sensitivity of LA in PM compared with that in VT underlines the importance of adding anti-beta2GPI in PM of APS, especially IgM isotype although recent review questioned its significance.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Estrogen-like activity of a subpopulation of natural antiestrogen receptor autoantibodies in man

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Evidence of an estrogen receptor form devoid of estrogen binding ability in MCF-7 cells

In MCF-7 breast cancer cells, hydroxytamoxifen (OH-Tam) up-regulates the estrogen receptor (ER) in a form unable to bind [3H]estradiol (E2). We show here that this property is not restricted to this antiestrogen. [3H]E2 binding assays (whole cell assays, DCC assays on cell extracts) and enzyme immunoassays (Abbott) performed in parallel, establish the permanent presence of such unusual ERs in the absence of any exposure of the cells to a ligand. E2 and the pure antiestrogen RU 58 668, which down-regulate ER, also decrease [3H]E2 binding. In control cells, these ERs represent about the half of the whole receptor population; they also display a tendency to stabilize within the cell nucleus. Loss of E2 binding ability appears irreversible, since we failed to label receptor accumulated under OH-Tam with [3H]E2 or [3H]tamoxifen aziridine (TAZ). Cycloheximide (CHX), which blocks E2-induced down regulation of ER, failed to stabilize [3H]E2 binding (whole cell assay) after an [3H]E2 pulse (1 h), confirming that regulation of E2 binding and peptide level are related to different regulatory mechanisms. Loss of binding ability could not be ascribed to any ER cleavage as demonstrated by Western blotting with a panel of ER antibodies raised against its various domains (67 kDa ER solely detected). We propose that loss of E2 binding ability is related to the aging process of the receptor, i.e. it is progressively converted to a form devoted to degradation after it has accomplished its physiological role. Ligands may favor (E2, RU 58 668) or impede (OH-Tam) this elimination process. (C) 2000 Elsevier Science Inc.SCOPUS: ar.jinfo:eu-repo/semantics/publishe