title: An estrogen-independent MCF-7 breast cancer cell line which contains a novel 80-kilodalton estrogen receptor-related protein.
abstract: Long-term growth of estrogen-responsive human breast cancer cell lines in estrogen-free media leads inevitably to the development of estrogen-independent growth. We have identified and characterized a unique subclone of the MCF-7 human breast cancer cell line, named MCF-7:2A, which grows maximally in the absence of endogenous estrogens but whose growth is inhibited by the antiestrogens 4-hydroxytamoxifen and ICI 164,384. The MCF-7:2A cells express high levels of estrogen receptor (ER; 477 fmol/mg protein), which can be reduced by growth in 10 nM 17 beta-estradiol (201 fmol/mg protein). Basal progesterone receptor synthesis is very low in the 2A cells (< 1 fmol/mg protein) but can be dramatically increased by 10 nM 17 beta-estradiol (384 fmol/mg protein). Clearly, the pathways that control growth and estrogen-regulated genes such as the progesterone receptor are now dissociated in these cells. MCF-7:2A cells also possess two unique characteristics. First, the MCF-7:2A cells constitutively activate an ER-responsive luciferase reporter construct in the absence of any estrogens, and this activation can be blocked by either 4-hydroxytamoxifen or ICI 164,384. This constitutive activity is not observed in the parental MCF-7 cells. Second, they express an 80-kDa protein that cross-reacts with three distinct antibodies to the ER. The MCF-7:2A cells were subjected to an additional round of limiting dilution subcloning, and 10 independent clones were all shown to express both the 66- and 80-kDa ERs as observed in the MCF-7:2A line. This confirms that both ERs are being expressed in each cell and are not the result of a mixed population of cells. While numerous ER variants have been reported previously, no ER has until now been described that is larger than the wild-type 66-kDa ER. The MCF-7:2A cells provide a unique model to use in the study of ER action and the development of estrogen-independent growth in human breast cancer cells.
authors.affiliation: Department of Human Oncology, University of Wisconsin Comprehensive Cancer Center, Madison 53792, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Pink
authors.forename: S Y
authors.initials: SY
authors.lastname: Jiang
authors.forename: M
authors.initials: M
authors.lastname: Fritsch
authors.forename: V C
authors.initials: VC
authors.lastname: Jordan
mesh_terms: D015153:Blotting, Western; D001943:Breast Neoplasms; D002455:Cell Division / Q000187:drug effects*; D002999:Clone Cells; D004591:Electrophoresis, Polyacrylamide Gel; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007700:Kinetics; D008156:Luciferases / Q000096:biosynthesis; D008970:Molecular Weight; D053284:Polyunsaturated Alkamides; D014176:Protein Biosynthesis; D011506:Proteins / Q000032:analysis; D011960:Receptors, Estrogen / Q000032:analysis / Q000096:biosynthesis*; D011980:Receptors, Progesterone / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000187:drug effects
chemical_list: C059917:ERD5 protein, human; D004965:Estrogen Antagonists; D053284:Polyunsaturated Alkamides; D011506:Proteins; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D011994:Recombinant Proteins; D013629:Tamoxifen; C016601:afimoxifene; D004958:Estradiol; C051781:ICI 164384; D008156:Luciferases