title: Estrogen regulation of thrombospondin-1 in human breast cancer cells.
abstract: Expression of thrombospondin-1 (TSP-1), a large extracellular matrix protein, has been associated with modulation of angiogenesis and tumor growth. Both pro and antiangiogenic properties of TSP-1 have been described, and the role of TSP-1 expression in the growth and progression of human breast cancer is not clear. Because estrogens cause progression of many breast cancers, and estradiol (E2) downregulates a TSP-1 receptor, we examined whether TSP-1 is regulated by estrogen and involved in tumor progression. E2 induced TSP-1 expression in T47-D and MCF-7 breast cancer cells in vitro within 3 to 6 hr; the induction was blocked by the anti-estrogen ICI 182,780, indicating that estrogen receptors (ER) are necessary for this effect. Furthermore, E2 caused the production of TSP-1 protein from tumor cells in an ER-alpha-dependent manner. The E2-mediated TSP-1 RNA induction was dose-dependent and blocked by actinomycin D, indicating that the response to E2 was at least partly transcriptional. Transfection studies with deletion constructs of the TSP-1 promoter identified an estrogen-responsive region in the human TSP-1 promoter, located between -2,200 and -1,792 bp upstream of the transcription start site. An antibody against TSP-1 restricted the proliferation of E2-dependent MCF-7 cells in vitro and in vivo. A panel of breast cancer cells proliferated in the presence of low concentrations of exogenous TSP-1, whereas higher concentrations inhibited proliferation. A real-time PCR analysis showed that E2 also induced TSP-1 mRNA in the normal mammary glands of immature ovariectomized mice in an ER-dependent manner. In summary, we report the novel observation that TSP-1 production is directly controlled by estrogens in ER-positive breast cancer cells, and the released protein has pro-growth regulatory functions. Consequently, we propose that TSP-1 could be a therapeutic target for anti-tumor therapy in early-stage tumors. (c) 2009 UICC.
authors.affiliation: Department of Biomedical Sciences, University of Missouri, Columbia, 65211, USA. hyders@missouri.edu
authors.forename: Salman M
authors.initials: SM
authors.lastname: Hyder
authors.forename: Yayun
authors.initials: Y
authors.lastname: Liang
authors.forename: Jianbo
authors.initials: J
authors.lastname: Wu
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D000077267:Fulvestrant; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D008321:Mammary Glands, Animal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D011401:Promoter Regions, Genetic; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism; D019700:Thrombospondin 1 / Q000378:metabolism*
chemical_list: D004965:Estrogen Antagonists; D004967:Estrogens; D011960:Receptors, Estrogen; D019700:Thrombospondin 1; D000077267:Fulvestrant; D004958:Estradiol