Estrogen and aryl hydrocarbon receptor expression and crosstalk in human Ishikawa endometrial cancer cells (original) (raw)
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Molecular and Cellular Endocrinology, 1999
To determine the molecular mechanisms underlying the ''cross talk'' between the activity of 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD), which binds to arylhydrocarbon receptor (AHR) and estradiol (E 2 )-liganded estrogen receptor (ER), we first examined the initial step of estrogen action, ligand binding to ER. None of the AHR ligands tested, i.e. TCDD, benzo[a]pyrene, 3,3%,4,4%,5-pentachlorobiphenyl, b-naphthoflavone, or a-naphthoflavone, bound to ERa. We report the first examination of TCDD interaction with ERb: TCDD did not displace E 2 from ERb. We then examined a second possible mechanism, i.e. direct inhibition of ERa binding to estrogen response elements (EREs) by the AHR/AHR nuclear translocator (ARNT) complex. The AHR/ARNT heterodimer did not bind either a full or half-site ERE. However, AHR/ARNT bound specifically to oligomers containing naturally occurring EREs derived from the human c-fos, pS2, and progesterone receptor (PR) gene promoters that include xenobiotic response element (XRE)-like sequences. In contrast, neither purified E 2 -liganded-ER from calf uterus or recombinant human ERa bound a consensus XRE. TCDD inhibited E 2 -activated reporter gene activity from a consensus ERE and from EREs in the pS2, PR, and Fos genes in transiently transfected MCF-7 human breast cancer cells. However, this inhibition was not reciprocal since E 2 did not inhibit TCDD-stimulated luciferase activity from the CYP1A1 promoter in transiently transfected MCF-7 or human endometrial carcinoma HEC-1A cells. We propose that at least part of the mechanism by which the AHR/ARNT complex inhibits estrogen action is by competitively inhibiting ERa binding to imperfect ERE sites, adjacent to or overlapping XREs.
2000
The molecular mechanisms underlying the apparent "cross-talk" between estrogen receptor (ER)-and arylhydrocarbon receptor (AHR)-mediated activities are unknown. To determine how AHR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) may inhibit ER action and, conversely, to examine how 17--estradiol (E 2 ) affects AHR activity, we examined discrete activities of each receptor, i.e., protein-protein interactions, DNA binding, and transcriptional activation. We report that AHR interacts directly with ER␣, COUP-TF, and ERR␣1, in a ligand-specific manner in vitro. Unoccupied or -napthoflavone (-NF)-occupied AHR showed stronger interaction with ER␣, COUP-TF, and ERR␣1 than when AHR was occupied by the partial antagonist ␣-naphthoflavone (␣-NF), indicating a role for ligand in AHR interaction with these proteins. We also report that AHR interacts with COUP-TF in transfected CV-1 cells. In contrast, the AHR nuclear translocator protein (ARNT) did not interact with COUP-TF, ERR␣1, or ER␣. We next examined the interaction of either ER␣ or COUP-TF with a consensus xenobiotic response element (XRE). Purified ER␣ did not bind the consensus XRE, but COUP-TFI bound the consensus XRE, suggesting a role for COUP-TF as a AHR/ARNT competitor for XRE binding. In transiently transfected MCF-7 human breast cancer cells, overexpression of COUP-TFI inhibited TCDD-activated reporter gene activity from the CYP1A1 promoter. TCDD inhibited estradiol (E 2 )-activated reporter gene activity from a consensus ERE and from the EREs in the pS2 and Fos genes, and COUP-TFI did not block the antiestrogenic activity of TCDD. The specific interaction of COUP-TF with XREs and AHR together with the inhibition of TCDD-induced gene expression by COUP-TF suggests that COUP-TF may regulate AHR action both by direct DNA binding competition and through protein-protein interactions.
The Ah receptor inhibits estrogen-induced estrogen receptor � in breast cancer cells
Biochem Biophys Res Commun, 2004
We have studied the effect of the aryl hydrocarbon receptor ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on estrogen receptor (ER) β gene expression in the human breast cancer cell line, T47D. TCDD inhibited 17β-estradiol (E2)-induced up-regulation of both ER β wild type and ER β cx mRNA. Cycloheximide pre-treatment had no inhibitory effect, and the estimated half-life of ER β mRNA of about 33 min was not changed by any hormone administration. Chromatin immunoprecipitation experiments showed recruitment of ER α to the ER β promoter. Gel mobility shift experiments revealed an E2-induced protein binding to a half site estrogen response element in the ER β promoter, and TCDD reduced that binding. These results show that ER α regulates the expression of its own heterodimerization partner, ER β, in T47D cells. TCDD, an anti-estrogenic compound, inhibits ER α-mediated induction of ER β mRNA. These findings add to our understanding of cross talk between dioxin and estrogen signaling in human cells.
Ah receptor agonists as endocrine disruptors: antiestrogenic activity and mechanisms
Toxicology Letters, 1998
Ž. 2,3,7,8-Tetrachlorodibenzo-p-dioxin TCDD and related compounds induce a broad spectrum of biochemical and toxic responses and disrupt multiple endocrine pathways. Research in this laboratory has focused on characterizing Ž. aryl hydrocarbon receptor AhR-mediated antiestrogenicity in the rodent uterus and mammary and in human breast Ž. cancer cells. TCDD inhibits multiple estrogen E2-induced responses in these tissues including development or growth of human mammary and endometrial cancer cells, carcinogen-induced mammary cancer in rats, and mammary cancer in mice bearing breast cancer cell xenografts. The mechanisms of AhR-mediated antiestrogenicity Ž. are complex; however, studies on the molecular biology of cross-talk between the AhR and estrogen-receptor ER signaling pathways have been initiated using several E2-regulated genes as models. The results indicate that the Ž. nuclear AhR complex targets specific genomic core inhibitory dioxin responsive elements iDREs in promoter regions of some E2-responsive target genes to inhibit hormone-induced transactivation. The pS2, cathepsin and c-fos genes have functional iDREs, whereas the iDRE in the progesterone receptor gene promoter was not functional. Research has also focused on development of AhR-based antiestrogens which inhibit mammary tumor development and growth but do not exhibit prototypical AhR-induced toxic responses.
Molecular and cellular endocrinology, 1994
17fl-Estradiol (E2) induces progesterone receptor (PR) binding, immunoreactive protein, nuclear PR formation and PR mRNA levels in MCF-7 human breast cancer cells. Gel mobility shift analysis of nuclear extracts from E2-treated cells also exhibited a higher intensity retarded band associated with formation of a PR complex with a consensus [32p]progesterone/glucocorticoid responsive element. In contrast, 1 nM 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alone did not alter or decrease these same responses in MCF-7 cells; however, in ceils co-treated with 1 nM TCDD plus 1 nM E 2, TCDD significantly inhibited all the E2-induced responses. Scatchard analysis of PR binding demonstrated that TCDD decreased the number of E2-induced PR cellular binding sites but not the binding affinity of the PR for a radiolabeled promegestrone. In parallel studies, 3-methylcholanthrene, a prototypical polynuclear aromatic hydrocarbon, also inhibited E2-induced PR binding and immunoreactive protein. For a series of halogenated aromatics including 2,3,7,8-and 1,2,7,8-tetrachlorodibenzofuran, 1,3,7,8-TCDD and 6-methyl-l,3,8-trichlorodibenzofuran, their rank order potency for inhibiting E2-induced PR binding paralleled their rank order binding to the aryl hydrocarbon (Ah) receptor. These results support a role for the Ah receptor in mediating the antiestrogenic activity of polynuclear and halogenated aromatic hydrocarbons and illustrate cross-talk between the Ah and estrogen receptor signal transduction pathways.
Toxicological …, 2000
The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and the role of aryl hydrocarbon receptor (AhR) in estradiol (E 2)induced uterine epithelial mitogenic activity and secretory protein mRNA expression were determined. Ovariectomized wild-type (wt) and AhR-knockout (AhRKO) mice received oil, E 2 , or 5 g/kg TCDD؉E 2. E 2 stimulated similar large increases in the uterine epithelial labeling index (LI) and mRNA abundance for the E 2-dependent epithelial secretory protein, lactoferrin (LF), in both wt and AhRKO mice. However, uterine epithelial LI and LF mRNA were significantly reduced by TCDD؉E 2 in wt but not AhRKO mice. To determine the roles of stromal and epithelial AhR in the TCDD effect, uterine stroma and epithelium from AhRKO and wt mice were enzymatically separated and recombined into four types of tissue recombinants that either contained or lacked AhR in one or more tissue compartments. Tissue recombinants were grafted into nude mice, which were later ovariectomized and given oil, E 2 , or TCDD؉E 2. Epithelial LI was significantly reduced by TCDD in grafts containing stromal AhR, regardless of epithelial AhR status. However, LI was unaffected by TCDD in grafts lacking stromal AhR, even when epithelial AhR was present. Thus, TCDD inhibits E 2-induced uterine epithelial mitogenic and secretory activity, and this requires AhR. Antiproliferative effects of TCDD on uterine epithelia appear to be mediated indirectly through stromal AhR, suggesting that liganded AhR alters epithelial function by disrupting normal E 2-induced stromal activity. This is the first demonstration that TCDD impairs uterine epithelial function by altering normal stromalepithelial interactions in vivo.
Biological Chemistry, 2006
The aryl hydrocarbon receptor (AhR) binds with high affinity to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related halogenated aromatics, but also binds with lower affinity to structurally diverse exogenous and endogenous chemicals. One study reported that 3methylcholanthrene (3MC) activated the estrogen receptor (ER) through the AhR, which acts as co-regulatory protein, whereas a recent report showed that 3MC directly bound and activated ERa. This study also shows that the AhR agonists benzowaxpyrene, 3,39,4,49-tetrachlorobiphenyl, chrysin, 6-methyl-1,3,8-trichlorodibenzofuran, and 3,39-diindolylmethane also induce ERa-dependent transactivation. Moreover, in chromatin immunoprecipitation assays, these compounds induce binding of AhR and ERa to the CYP1A1 and pS2 gene promoters, which is consistent with their activities as both selective AhR modulators (SAhRMs) and selective ER modulators (SERMs).
The Ah receptor inhibits estrogen-induced estrogen receptor β in breast cancer cells
Biochemical and Biophysical Research Communications, 2004
We have studied the effect of the aryl hydrocarbon receptor ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on estrogen receptor (ER) b gene expression in the human breast cancer cell line, T47D. TCDD inhibited 17b-estradiol (E 2 )-induced up-regulation of both ER b wild type and ER b cx mRNA. Cycloheximide pre-treatment had no inhibitory effect, and the estimated halflife of ER b mRNA of about 33 min was not changed by any hormone administration. Chromatin immunoprecipitation experiments showed recruitment of ER a to the ER b promoter. Gel mobility shift experiments revealed an E 2 -induced protein binding to a half site estrogen response element in the ER b promoter, and TCDD reduced that binding. These results show that ER a regulates the expression of its own heterodimerization partner, ER b, in T47D cells. TCDD, an anti-estrogenic compound, inhibits ER amediated induction of ER b mRNA. These findings add to our understanding of cross talk between dioxin and estrogen signaling in human cells.
Molecular Cancer Research, 2009
In this study, we examined the role of estrogen receptors (ER) in aryl hydrocarbon receptor (AHR)-dependent transactivation. Chromatin immunoprecipitation assays showed that AHR agonists differentially induced recruitment of ERα to the AHR target genes CYP1A1 and CYP1B1. Cotreatment with 17β-estradiol significantly increased β-naphthoflavone (BNF)-and 2,3,7,8-tetrachlorodibenzop-dioxin-induced recruitment of ERα to CYP1A1, whereas 3,3′-diindolylmethane induced promoter occupancy of ERα at CYP1A1 that was unaffected by cotreatment with 17β-estradiol. Cyclical recruitment of AHR and ERα to CYP1A1 was only observed in cells treated with BNF. Stable and subtype-specific knockdown of ERα or ERβ using shRNA showed that suppression of ERα significantly reduced, whereas knockdown of ERβ significantly enhanced, AHR agonist-induced Cyp1a1 expression in HC11 mouse mammary epithelial cells. AHR agonist-induced Cyp1b1 expression was reduced by ERβ knockdown but unaffected by ERα knockdown. The siRNA-mediated knockdown of ERα in MCF-7 human breast cancer cells did not affect 2,3,7,8-tetrachlorodibenzo-p-dioxin-dependent regulation of CYP1A1 and CYP1B1 mRNA expression. In agreement with our in vitro findings in the HC11 cells, ERα knockout mice exhibit reduced BNF-dependent induction of Cyp1a1 mRNA. These results establish ligand-and promoter-specific influences on the cyclical recruitment patterns for AHR and show ER species-, subtype-, and promoter-specific modulation of AHR-dependent transcription. (Mol Cancer Res