title: Down-regulation of messenger ribonucleic acid and protein levels for estrogen receptors by phorbol ester and calcium in MCF-7 cells.
abstract: Treatment of MCF-7 cells, a human mammary carcinoma cell line, with phorbol ester [12-O-tetradecanoylphorbol-13-acetate (TPA)] or calcium ionophore (A23187) was associated with striking effects on levels of estrogen receptor (ER) mRNA, specific binding of 17 beta-[3H]estradiol [( 3H]E2), and immunoreactive ER. TPA (10(-7) M) caused a time-dependent reduction of ER mRNA which was below the level of detection after 9 h. Similar effects of TPA appeared at levels of specific binding of [3H]E2 as well as immunoreactive ER. In contrast, TPA induced an increase in mRNA for beta-actin. Incubation of MCF-7 cells with increasing concentrations of TPA (10(-11)-10(-7) M) was associated with biphasic effects on ER mRNA and proteins. Levels of immunoreactive progesterone receptors (PR) were induced by E2 (10(-9) M) in a time-dependent manner. In the presence of TPA (10(-7) M), where ER levels were suppressed, no induction of PR was observed. Removal of TPA (10(-7) M) after 10 h (ER mRNA) or 22 h (ER proteins) of treatment was associated with a continued suppression of both mRNA and protein levels during the entire incubation period (48 h). Treatment with A23187 (2 x 10(-7) M) also caused a time-dependent down-regulation of levels of ER mRNA and proteins. These effects occurred somewhat more slowly than those of TPA. Levels of beta-actin mRNA were not changed by this treatment. These results indicate that changes in estrogen sensitivity are mediated by calcium-dependent protein kinases in human mammary carcinoma MCF-7 cells.
authors.affiliation: Institute of Medical Biochemistry, University of Oslo, Norway.
authors.forename: A H
authors.initials: AH
authors.lastname: Ree
authors.forename: B F
authors.initials: BF
authors.lastname: Landmark
authors.forename: S I
authors.initials: SI
authors.lastname: Walaas
authors.forename: H
authors.initials: H
authors.lastname: Lahooti
authors.forename: L
authors.initials: L
authors.lastname: Eikvar
authors.forename: W
authors.initials: W
authors.lastname: Eskild
authors.forename: V
authors.initials: V
authors.lastname: Hansson
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects*; D004958:Estradiol / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D012333:RNA, Messenger / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D012333:RNA, Messenger; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D000001:Calcimycin; D004958:Estradiol; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium