Differential activation of wild-type estrogen receptor alpha and C-terminal deletion mutants by estrogens, antiestrogens and xenoestrogens in breast cancer cells.
17beta-Estradiol (E2), diethylstilbestrol (DES) and several synthetic (or xenoestrogenic) compounds induced transactivation in MCF-7 or MDA-MB-231 cells transfected with wild-type estrogen receptor alpha (ERalpha) and a construct (pERE(3)) containing three tandem estrogen responsive elements (EREs) linked to a luciferase gene. In contrast, the antiestrogens ICI 182,780 and 4-hydroxytamoxifen (4-OHT) were inactive in this assay. We have investigated the effects of these compounds and several structurally-diverse estrogenic compounds on transactivation in cells transfected with pERE(3) and wild-type ERalpha, mutant ERalpha (1-553), and ERalpha (1-537) containing deletions of amino acids 595-554 and 595-538, respectively. These constructs were used to develop an in vitro assay to distinguish between different structural classes of estrogenic compounds. The results obtained using these constructs were highly cell context- and structure-dependent. Neither E2- nor diethylstilbestrol-induced transactivation in MCF-7 (or MDA-MB-231) cells transfected with pERE(3)/ERalpha (1-537) due to partial deletion of helix 12; however, octylphenol and nonlylphenol, resveratrol (a phytoestrogen), kepone and 2',3',4',5'-tetrachloro-4-biphenylol were "estrogenic" in MCF-7 cells transfected with pERE(3)/ERalpha (1-537). Moreover, the structure-dependent estrogenic activities of several synthetic estrogens (xenoestrogens) in MDA-MB-231 cells were different than those observed in MCF-7 cells. These results demonstrate that the estrogenic activity of many synthetic compounds do not require activation function 2 (AF-2) of ERalpha and are mechanistically different from E2. These data suggest that xenoestrogens are selective ER modulators (SERMs).
Wu
Fei
F
Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, United States.
Safe
Stephen
S
D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology; D020847:Estrogen Receptor Modulators / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism*; D004967:Estrogens / Q000494:pharmacology*; D006801:Humans; D009154:Mutation; D020080:Tandem Repeat Sequences; D015533:Transcriptional Activation; D014162:Transfection
D020847:Estrogen Receptor Modulators; D047628:Estrogen Receptor alpha; D004967:Estrogens; D004958:Estradiol