title: Identification of estrogen-induced genes downregulated by AhR agonists in MCF-7 breast cancer cells using suppression subtractive hybridization.
abstract: Aryl hydrocarbon receptor (AhR) agonists inhibit 17beta-estradiol (E2) induced growth of MCF-7 human breast cancer cells in vitro and rodent mammary tumor growth in vivo. Genes associated with inhibitory AhR-estrogen receptor (ER) crosstalk were investigated in MCF-7 human breast cancer cells using poly(A)(+)RNA from cells treated with either 1 nM E2 (target) or E2 plus 1 nM 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (reference) or 25 microM diindolylmethane (DIM) as AhR agonists in MCF-7 cells. Suppression subtractive hybridization (SSH) was subsequently used to identify 33 genes with sequence homology to known human genes that are induced by E2 and inhibited by AhR agonists in MCF-7 cells; two unknown genes were also identified. Many of these genes are involved in cell proliferation and these include cell cycle regulators (cdc28/cdc2-associated protein), nucleotide synthases (thymidylate synthase), early intermediate genes (early growth response alpha, EGRalpha) and other proteins involved in signaling pathways (calmodulin, ATP synthase alpha subunit). Thus SSH has identified a diverse spectrum of new genes that are affected by inhibitory AhR-ER crosstalk and among this group are a subset of genes that may be critical for the in vivo antitumorigenic effects of AhR agonists.
authors.affiliation: Department of Veterinary Physiology and Pharmacology, A&M University, College Station, TX 77843, USA.
authors.forename: I
authors.initials: I
authors.lastname: Chen
authors.forename: T
authors.initials: T
authors.lastname: Hsieh
authors.forename: T
authors.initials: T
authors.lastname: Thomas
authors.forename: S
authors.initials: S
authors.lastname: Safe
mesh_terms: D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology; D015152:Blotting, Northern; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics*; D015536:Down-Regulation; D004958:Estradiol / Q000378:metabolism / Q000494:pharmacology; D004967:Estrogens / Q000378:metabolism* / Q000494:pharmacology; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D017403:In Situ Hybridization / Q000379:methods*; D007211:Indoles / Q000494:pharmacology; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D018336:Receptors, Aryl Hydrocarbon / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D016588:Anticarcinogenic Agents; D004967:Estrogens; D007211:Indoles; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D004958:Estradiol; C016392:3,3'-diindolylmethane