Abstract 4072: Overexpression of FOXO1 increased sensitivity to Tamoxifen in MCF7 cells, and is associated with estrogen receptor α (ERα) expression

AbstractBioactive fractions obtained from medicinal plants which have been used for the treatment of multiple diseases could exert their effects by targeting common pathways. Prior knowledge of their usage could allow us to identify novel molecular links. In this study, we explored the molecular basis of action of one such herbal formulation Cissampelos pareira L. (Cipa), used for the treatment of female hormone disorders and fever. Transcriptomic studies on MCF7 cell lines treated with Cipa extract carried out using Affymetrix arrays revealed a downregulation of signatures of estrogen response potentially modulated through estrogen receptor α (ERα). Molecular docking analysis identified 38 Cipa constituents that potentially bind (ΔG < − 7.5) with ERα at the same site as estrogen. The expression signatures in the connectivity map (https://clue.io/;) revealed high positive scores with translation inhibitors such as emetine (score: 99.61) and knockdown signatures of genes linked to the antiviral response such as ribosomal protein RPL7 (score: 99.92), which is a reported ERα coactivator. Further, gene knockdown experiments revealed that Cipa exhibits antiviral activity in dengue infected MCF7 cells potentially modulated through estrogen receptor 1. This approach reveals a novel pathway involving the ESR1-RPL7 axis which could be a potential target in dengue viral infection.

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The Human Estrogen Receptor-α Isoform hERα46 Antagonizes the Proliferative Influence of hERα66 in MCF7 Breast Cancer Cells

Endocrinology ◽

10.1210/en.2005-0866 ◽

2005 ◽

Vol 146 (12) ◽

pp. 5474-5484 ◽

Cited By ~ 65

Author(s):

Graziella Penot ◽

Christine Le Péron ◽

Yohann Mérot ◽

Eva Grimaud-Fanouillère ◽

François Ferrière ◽

...

Keyword(s):

Breast Cancer ◽

Cell Cycle ◽

Estrogen Receptor ◽

Cell Growth ◽

Activation Function ◽

Estrogen Receptor Α ◽

Breast Cancer Cell Lines ◽

Mcf7 Cells ◽

Exact Function ◽

Human Estrogen Receptor

The expression of two human estrogen receptor-α (hERα) isoforms has been characterized within estrogen receptor-α-positive breast cancer cell lines such as MCF7: the full-length hERα66 and the N terminally deleted hERα46, which is devoid of activation function (AF)-1. Although hERα66 is known to mediate the mitogenic effects that estrogens have on MCF7 cells, the exact function of hERα46 in these cells remains undefined. Here we show that, during MCF7 cell growth, hERα46 is mainly expressed in the nucleus at relatively low levels, whereas hERα66 accumulates in the nucleus. When cells reach confluence, the situation reverses, with hERα46 accumulating within the nucleus. Although hERα46 expression remains rather stable during an estrogen-induced cell cycle, its overexpression in proliferating MCF7 cells provokes a cell-cycle arrest in G0/G1 phases. To gain further details on the influence of hERα46 on cell growth, we used PC12 estrogen receptor-α-negative cell line, in which stable transfection of hERα66 but not hERα46 allows estrogens to behave as mitogens. We next demonstrate that, in MCF7 cells, overexpression of hERα46 inhibits the hERα66-mediated estrogenic induction of all AF-1-sensitive reporters: c-fos and cyclin D1 as well as estrogen-responsive element-driven reporters. Our data indicate that this inhibition occurs likely through functional competitions between both isoforms. In summary, hERα46 antagonizes the proliferative action of hERα66 in MCF7 cells in part by inhibiting hERα66 AF-1 activity.

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Raloxifene and ICI182,780 Increase Estrogen Receptor-α Association with a Nuclear Compartment via Overlapping Sets of Hydrophobic Amino Acids in Activation Function 2 Helix 12

Molecular Endocrinology ◽

10.1210/me.2006-0074 ◽

2007 ◽

Vol 21 (4) ◽

pp. 797-816 ◽

Cited By ~ 27

Author(s):

Mathieu Lupien ◽

M. Jeyakumar ◽

Elise Hébert ◽

Khalid Hilmi ◽

David Cotnoir-White ◽

...

Keyword(s):

Estrogen Receptor ◽

Ligand Binding ◽

Transcriptional Activity ◽

Resonance Energy Transfer ◽

Resonance Energy ◽

Activation Function ◽

Estrogen Receptor Α ◽

Mcf7 Cells ◽

Hydrophobic Residues ◽

Helix 12

Abstract The basis for the differential repressive effects of antiestrogens on transactivation by estrogen receptor-α (ERα) remains incompletely understood. Here, we show that the full antiestrogen ICI182,780 and, to a lesser extent, the selective ER modulator raloxifene (Ral), induce accumulation of exogenous ERα in a poorly soluble fraction in transiently transfected HepG2 or stably transfected MDA-MB231 cells and of endogenous receptor in MCF7 cells. ERα remained nuclear in HepG2 cells treated with either compound. Replacement of selected hydrophobic residues of ERα ligand-binding domain helix 12 (H12) enhanced receptor solubility in the presence of ICI182,780 or Ral. These mutations also increased transcriptional activity with Ral or ICI182,780 on reporter genes or on the endogenous estrogen target gene TFF1 in a manner requiring the integrity of the N-terminal AF-1 domain. The antiestrogen-specific effects of single mutations suggest that they affect receptor function by mechanisms other than a simple decrease in hydrophobicity of H12, possibly due to relief from local steric hindrance between these residues and the antiestrogen side chains. Fluorescence anisotropy experiments indicated an enhanced regional stabilization of mutant ligand-binding domains in the presence of antiestrogens. H12 mutations also prevent the increase in bioluminescence resonance energy transfer between ERα monomers induced by Ral or ICI182,780 and increase intranuclear receptor mobility in correlation with transcriptional activity in the presence of these antiestrogens. Our data indicate that ICI182,780 and Ral locally alter the ERα ligand binding structure via specific hydrophobic residues of H12 and decrease its transcriptional activity through tighter association with an insoluble nuclear structure.

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Estrogen receptor α regulates the expression of syndecan-1 in human breast carcinoma cells

Endocrine Related Cancer ◽

10.1530/erc-18-0285 ◽

2019 ◽

Vol 26 (6) ◽

pp. 615-628 ◽

Cited By ~ 4

Author(s):

Emmanuelle Fleurot ◽

Caroline Goudin ◽

Vincent Hanoux ◽

Pierre-Jacques Bonnamy ◽

Jérôme Levallet

Keyword(s):

Estrogen Receptor ◽

De Novo ◽

Acquired Resistance ◽

Inverse Correlation ◽

Estrogen Receptor Α ◽

Mcf7 Cells ◽

Irreversible Inhibitor ◽

Attractive Therapeutic Target ◽

Antihormonal Therapy ◽

Er Expression

Breast cancer (BC) is the primary cause of cancer-related mortality among women. Patients who express the estrogen receptor (ER), which mediates the tumorigenic effects of estrogens, respond to antihormonal therapy. Loss of ER expression or acquired resistance to E2 is associated with aggressive malignant phenotypes, which lead to relapse. These BC subtypes overexpress syndecan-1 (SDC1), a transmembrane heparan sulfate proteoglycan that mediates angiogenesis as well as the proliferation and invasiveness of cancer cells. We showed here that the activation of ER-alpha (ERα) by estrogens induces downregulation of SDC1 expression in ER(+) MCF7 cells but not in T47D cells. Loss of ERα expression, induced by RNA interference or a selective ER downregulator, led to subsequent SDC1 overexpression. E2-dependent downregulation of SDC1 expression required de novo protein synthesis and was antagonized by treatment with BAY 11-7085, an irreversible inhibitor of IκBα phosphorylation, which inhibits the activation of NFκB. Downregulation of SDC1 expression required ERα and activation of IKK, but was independent to downstream transcriptional regulators of NFκB. BAY 11-7085 prevented E2-mediated phosphorylation of ERα on Ser118, increasing its proteasomal degradation, suggesting that IKK stabilized E2-activated ERα, leading to subsequent downregulation of SDC1 expression. Our results showed that sustained ER signaling inhibits SDC1 expression. Such antagonism elucidates the inverse correlation between SDC1 and ER expression in ER(+) BC as well as the overexpression of SDC1 in hormone receptor-negative BC subtypes with the most aggressive phenotypes. These results identify SDC1 as an attractive therapeutic target for BC as well as for other endocrine-associated cancers.

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