Estrogenic and anti-estrogenic regulation of estrogen receptor in MCF-7 breast-cancer cells: comparison of immunocytochemical data with biochemical measurements.
Data from immunocytochemical assessment of estrogen receptor (ER) regulation in MCF-7 cells under estrogenic and anti-estrogenic stimulation were compared with those obtained by enzyme immunoassay (Abbott ER-EIA). Similar trends were observed, although ER level variations were less marked when assessed immunocytochemically. We confirmed reports of ER disappearance in the presence of estrogens (Es; E2 and DES) and pure anti-estrogens (AEs; RU 58,668 and ICI 164,384) as well as its increase with partial AEs (4-OH-TAM and RU 39,119). E2-induced ER down-regulation was partly blocked by actinomycin D (AMD), okadaic acid (OK) and cycloheximide (CHX) when assessed by these 2 methods. Down-regulation by pure AEs was not impeded by CHX, indicating that they operate differently from Es (i.e., transformation of ER to a form sensitive to constitutive degradation activity). In situ pre-labeling of the cells with [3H]TAZ indicated that all investigated ligands eliminate pre-existing ER through binding to newly synthetized receptors, since [3H]TAZ co-valently associates with ER; E2 and RU 58,668 were more effective than 4-OH-TAM in this regard. CHX blocked ER disappearance even in the presence of pure AEs, which is in contrast to the data established with cells not pre-exposed to [3H]TAZ. Nuclear location of [3H]TAZ-ER complexes may explain this discrepancy, since pure AE-ER complexes were reported to be incapable of nuclear translocation.
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Laboratoire J.-C. Heuson de Cancérologie Mammaire, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium.
Larsimont
D
D
Querton
G
G
El Khissiin
A
A
Laios
I
I
Legros
N
N
Leclercq
G
G
D001943:Breast Neoplasms / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D015536:Down-Regulation; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology*; D004967:Estrogens / Q000494:pharmacology*; D006801:Humans; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D007700:Kinetics; D019319:Okadaic Acid / Q000494:pharmacology; D053284:Polyunsaturated Alkamides; D011960:Receptors, Estrogen / Q000378:metabolism*; D013629:Tamoxifen / Q000494:pharmacology; D013997:Time Factors; D014407:Tumor Cells, Cultured; D005466:Fluorocarbons
D003513:Cycloheximide; D003609:Dactinomycin; D004958:Estradiol; D004965:Estrogen Antagonists; D004967:Estrogens; D019319:Okadaic Acid; D053284:Polyunsaturated Alkamides; D011960:Receptors, Estrogen; D013629:Tamoxifen; C086511:RU 58668; D005466:Fluorocarbons; C051781:ICI 164384