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: Salman M Hyder, Yayun Liang, Jianbo Wu
• Journal: International journal of cancer (Int J Cancer) Vol. 125 Issue 5 Pg. 1045-53 (Sep 01 2009) ISSN: 1097-0215 [Electronic] United States
• PMID: 19391135 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Estrogen Antagonists
• Estrogens
• Receptors, Estrogen
• Thrombospondin 1
• Fulvestrant
• Estradiol

Topics

• Animals
• Blotting, Northern
• Breast Neoplasms (drug therapy, metabolism, pathology)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Estradiol (analogs & derivatives, pharmacology)
• Estrogen Antagonists (pharmacology)
• Estrogens (pharmacology)
• Female
• Fulvestrant
• Gene Expression Regulation, Neoplastic (drug effects)
• Humans
• Mammary Glands, Animal (cytology, drug effects, metabolism)
• Mice
• Promoter Regions, Genetic
• Receptors, Estrogen (genetics, metabolism)
• Thrombospondin 1 (metabolism)