Interaction of human estrogen receptors α and β with the same naturally occurring estrogen response elements

Hyder, Salman M.; Chiappetta, Constance; Stancel, George M.

doi:10.1016/s0006-2952(98)00355-4

Cited by 91 publications

(56 citation statements)

References 14 publications

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“…This shift is noticeable mainly in the agonist mode and is consistent in the whole compound collection; hence the rank of potencies is conserved between LBD and full-length ERβ reporters. It is worth noting that ERβ is considerably weaker transactivator than ERα due to lower affinity for ERE half-sites [22-24]. In agreement with this observation, we obtained only moderate fold induction of luciferase activity using U2OS-ERβ/3xERE cell line (3 to 4-fold) in contrast to wider dynamic range offered by U2OS-ERβ-LBD/9xGal4UAS cell line (25-fold).…”

Section: Resultssupporting

confidence: 85%

Two Panels of Steroid Receptor Luciferase Reporter Cell Lines for Compound Profiling

Sedlák¹,

Paguio²,

Bartůněk

2011

CCHTS

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Steroid hormone receptors represent a major target in drug discovery. As ligand inducible transcription factors, their activity can be modulated by small lipophilic molecules. Here we describe two panels of potent and selective luciferase reporter cell lines based on cells with low endogenous steroid receptor activity (U2OS). The panels contain reporter cell lines for estrogen receptors α and β, androgen, glucocorticoid, mineralocorticoid, and progesterone receptors. In the first panel, the activation of either synthetic, steroid response elements containing promoter or viral promoter is mediated by full-length steroid receptors. The second panel is based on the expression of the chimeric receptor, which was created by the replacement of the N-terminal part of the molecule by Gal4 DBD and that binds to multiple UAS sites in the reporter promoter. Both panels were extensively characterized by profiling 28 ligands in dose response manner in agonist and antagonist mode. We have analyzed and compared the responses to tested ligands from both panels and concluded that in general both systems generated similar qualitative response in terms of potency, efficacy, partial agonism/antagonism, mixed agonistic/antagonistic profiles and the rank of potencies was well conserved between both panels. However, we have also identified some artifacts introduced by the Gal4/LBD reporter assays in contrast to their full-length receptor reporter counterparts. Keeping in mind the advantages and drawbacks of each reporter format, these cell lines represent powerful and selective tools for profiling large compound libraries (HTS) and for detailed study of mechanisms by which compounds exert their biological effects.

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Section: Resultssupporting

confidence: 85%

Two Panels of Steroid Receptor Luciferase Reporter Cell Lines for Compound Profiling

Sedlák¹,

Paguio²,

Bartůněk

2011

CCHTS

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“…However, AKT phosphorylation site is present only in ER␣ (36). ERs exist as homodimers as well as ER␣⅐ER␤ heterodimers, and these combinations have different affinity for EREs (37,38). Therefore, induction of ERE containing genes upon activation of AKT may be cell type-dependent.…”

Section: Discussionmentioning

confidence: 99%

Phosphatidylinositol 3-Kinase/AKT-mediated Activation of Estrogen Receptor α

Campbell¹,

Bhat‐Nakshatri

Patel³

et al. 2001

Journal of Biological Chemistry

891

650

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Estrogen receptors (ERs) mediate most of the biological effects of estrogen in mammary and uterine epithelial cells by binding to estrogen response elements in the promoter region of target genes or through protein-protein interactions. Anti-estrogens such as tamoxifen inhibit the growth of ER-positive breast cancers by reducing the expression of estrogen-regulated genes. However, anti-estrogen-resistant growth of ER-positive tumors remains a significant clinical problem. Here we show that phosphatidylinositol (PI) 3-kinase and AKT activate ER␣ in the absence of estrogen. Although PI 3-kinase increased the activity of both estrogen-independent activation function 1 (AF-1) and estrogendependent activation function 2 (AF-2) of ER␣, AKT increased the activity of only AF-1. PTEN and a catalytically inactive AKT decreased PI 3-kinase-induced AF-1 activity, suggesting that PI 3-kinase utilizes AKTdependent and AKT-independent pathways in activating ER␣. The consensus AKT phosphorylation site Ser-167 of ER␣ is required for phosphorylation and activation by AKT. In addition, LY294002, a specific inhibitor of the PI 3-kinase/AKT pathway, reduced phosphorylation of ER␣ in vivo. Moreover, AKT overexpression led to up-regulation of estrogen-regulated pS2 gene, Bcl-2, and macrophage inhibitory cytokine 1. We demonstrate that AKT protects breast cancer cells from tamoxifen-induced apoptosis. Taken together, these results define a molecular link between activation of the PI 3-kinase/AKT survival pathways, hormone-independent activation of ER␣, and inhibition of tamoxifen-induced apoptotic regression.

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“…To interpret our findings of decreased ERE v -tk-Luc activation by the PA derivatives, it should be remembered that this construct does not contain a significant portion of the vitellogenin gene promoter, only 2 copies of the small regulatory element ERE v (AGGTCA-N 3 -TGACCT) that has been shown to directly bind and be activated by ER␣ (␤) homo (hetero)dimers. 28 Thus, specific inhibition of ERE v -tk-Luc by PA must be mediated directly through ERE v and, therefore, presumably involves changes in the levels or function of ERs or other transactivating proteins that are able to bind to ERE v . The specificity of these inhibitory effects as being mediated through the ER was confirmed using MD-MB-231 cells.…”

Section: Discussionmentioning

confidence: 99%

Inhibition of estrogen-dependent breast cell responses with phenylacetate

et al. 2001

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The aromatic fatty acid phenylacetate (PA) and its analogs have come under intense investigation due to their ability to cause the growth arrest of a variety of neoplasia, including human breast cancer. We have determined that PA and its halide derivative 4-chlorophenylacetate (4-CPA) showed marked antiproliferative activity on 3 of 6 human breast cancer cell lines tested. Interestingly, the 3 cell lines that were growth inhibited by PA and 4-CPA were estrogen receptor (ER) positive (T47-D, MCF-7 and ZR-75-1) whereas those that were little affected by these compounds were ER-negative (MDA-MB-157, MDA-MB-231 and SK-Br-3). Dose response studies indicated that 4-CPA inhibited the growth of the sensitive (ER؉) cell lines with a potency 3-4 times that of PA. These findings suggest that there is "crosstalk" between the PA and estrogen signaling pathways such that PA can directly inhibit estrogen-dependent events. This hypothesis was directly tested in vitro using ER؉ MCF-7 cells that were stably transfected with a luciferase reporter construct driven by the full length ( Key words: phenylacetate; breast cancer; estrogen; receptorBreast cancer is 1 of the most prevalent types of cancer observed in women, developing in approximately 1 of 9 women sometime during their lifetime. The etiology of this malignancy is known to involve a complex interplay of genetic, environmental, and hormonal factors that influence the physiological status of the host. 1,2 With regards to the latter factor, there is considerable data that implicate the involvement of steroid hormones, especially estrogen, in the development and progression of breast cancer. This fact has lead to the use of antiestrogens in the therapeutic intervention of this disease. To date, the clinical use of antiestrogens has been limited to compounds that inhibit estrogen signaling at the level of the estrogen receptor (ER) by competing with the ligand (i.e., estrogen) for receptor binding. 3 Although shown to be extremely useful, the clinical results are often unpredictable due to the complex functional activity of ERs liganded with different antiestrogen compounds or the ability of the receptors to undergo changes (mutations or otherwise) that can alter their functional characteristics or response to estrogen antagonists. 4 Thus, there is a need to develop therapeutic compounds that can inhibit the estrogen signaling pathway by mechanisms that may not depend upon competitive ligand binding to the ER.Aromatic fatty acids, of which phenylacetate (PA) is a prototype, constitute a new class of low toxicity drugs with demonstrated antitumor activity in experimental models and in humans. PA is a natural metabolite of phenylalanine that was originally described as a plant growth hormone. 5 Normally found in micromolar concentrations in human plasma, PA has a long clinical history as treatment for conditions associated with hyperammonemia such as in children with urea cycle disorders. 6,7 This clinical experience has indicated that millimolar blood serum levels can be achiev...

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Interaction of human estrogen receptors α and β with the same naturally occurring estrogen response elements

Cited by 91 publications

References 14 publications

Two Panels of Steroid Receptor Luciferase Reporter Cell Lines for Compound Profiling

Two Panels of Steroid Receptor Luciferase Reporter Cell Lines for Compound Profiling

Phosphatidylinositol 3-Kinase/AKT-mediated Activation of Estrogen Receptor α

Inhibition of estrogen-dependent breast cell responses with phenylacetate

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