title: Clomiphene citrate down-regulates estrogen receptor-α through the ubiquitin-proteasome pathway in a human endometrial cancer cell line.
abstract: We examined how clomiphene citrate (CC) reduces estrogen receptor-α (ERα) in a human endometrial cancer cell line. Ishikawa human endometrial cancer cells were treated with ERα ligands such as 17β-estradiol (E2), CC, and the pure antiestrogen, ICI 182,780 (ICI). Thereafter, the expression levels of ERα protein and mRNA were analyzed by western blot and real-time quantitative PCR, respectively, and those of ubiquitinated ERα were analyzed by immunoprecipitation of ERα followed by immunoblotting with an anti-ubiquitin antibody. The expression levels of ERα protein after treatment with E2, CC, and ICI were significantly decreased compared to pre-treatment levels without a corresponding decrease in ERα mRNA. These ligands significantly increased the levels of ubiquitinated ERα compared to vehicle treatment. Co-treatment with the proteasome inhibitor, MG132, abrogated the decrease in ERα levels caused by treatment with the ligands only. We demonstrated, for the first time, a CC-induced decrease in ERα mediated by the ubiquitin-proteasome pathway in human endometrial cancer cells.
authors.affiliation: Department of Obstetrics and Gynecology, Yamagata University Faculty of Medicine, Yamagata 990-9585, Japan.
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Amita
authors.affiliation: Department of Obstetrics and Gynecology, Yamagata University Faculty of Medicine, Yamagata 990-9585, Japan. Electronic address: totakaha@med.id.yamagata-u.ac.jp.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Takahashi
authors.affiliation: Department of Obstetrics and Gynecology, Yamagata University Faculty of Medicine, Yamagata 990-9585, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Igarashi
authors.affiliation: Department of Obstetrics and Gynecology, Yamagata University Faculty of Medicine, Yamagata 990-9585, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Nagase
mesh_terms: D045744:Cell Line, Tumor; D002996:Clomiphene / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects*; D016889:Endometrial Neoplasms / Q000235:genetics* / Q000473:pathology; D047628:Estrogen Receptor alpha / Q000235:genetics* / Q000378:metabolism; D005260:Female; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D008024:Ligands; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D025801:Ubiquitin / Q000378:metabolism*; D054875:Ubiquitination / Q000187:drug effects
chemical_list: C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D007976:Leupeptins; D008024:Ligands; D012333:RNA, Messenger; D025801:Ubiquitin; D049452:Green Fluorescent Proteins; D002996:Clomiphene; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde
keywords: Clomiphene citrate; Endometrium; Estrogen receptor-α; Proteasome; Ubiquitination