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Complex regulation of LCoR signaling in breast cancer cells.

ABSTRACT: Ligand-dependent corepressor (LCoR) is a transcriptional repressor of ligand-activated estrogen receptors (ERs) and other transcription factors that acts both by recruiting histone deacetylases and C-terminal binding proteins. Here, we first studied LCOR gene expression in breast cancer cell lines and tissues. We detected two mRNAs variants, LCoR and LCoR2 (which encodes a truncated LCoR protein). Their expression was highly correlated and localized in discrete nuclear foci. LCoR and LCoR2 strongly repressed transcription, inhibited estrogen-induced target gene expression and decreased breast cancer cell proliferation. By mutagenesis analysis, we showed that the helix-turn-helix domain of LCoR is required for these effects. Using in vitro interaction, coimmunoprecipitation, proximity ligation assay and confocal microscopy experiments, we found that receptor-interacting protein of 140?kDa (RIP140) is a LCoR and LCoR2 partner and that this interaction requires the HTH domain of LCoR and RIP140 N- and C-terminal regions. By increasing or silencing LCoR and RIP140 expression in human breast cancer cells, we then showed that RIP140 is necessary for LCoR inhibition of gene expression and cell proliferation. Moreover, LCoR and RIP140 mRNA levels were strongly correlated in breast cancer cell lines and biopsies. In addition, RIP140 positively regulated LCoR expression in human breast cancer cells and in transgenic mouse models. Finally, their expression correlated with overall survival of patients with breast cancer. Taken together, our results provide new insights into the mechanism of action of LCoR and RIP140 and highlight their strong interplay for the control of gene expression and cell proliferation in breast cancer cells.

SUBMITTER: Jalaguier S

PROVIDER: S-EPMC5562849 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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Complex regulation of LCoR signaling in breast cancer cells.

Jalaguier S S Teyssier C C Nait Achour T T Lucas A A Bonnet S S Rodriguez C C Elarouci N N Lapierre M M Cavaillès V V

Oncogene 20170417 33

Ligand-dependent corepressor (LCoR) is a transcriptional repressor of ligand-activated estrogen receptors (ERs) and other transcription factors that acts both by recruiting histone deacetylases and C-terminal binding proteins. Here, we first studied LCOR gene expression in breast cancer cell lines and tissues. We detected two mRNAs variants, LCoR and LCoR2 (which encodes a truncated LCoR protein). Their expression was highly correlated and localized in discrete nuclear foci. LCoR and LCoR2 stron ...[more]

PMID: 28414308

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Project description:Estrogen signaling and epigenetic modifications, in particular DNA methylation, are involved in regulation of gene expression in breast cancers. Here we investigated a potential regulatory cross-talk between these two pathways by identifying their common target genes and exploring potential underlying molecular mechanisms in human MCF7 breast cancer cells. Principal Findings: Gene expression profiling revealed that the expression of approximately 150 genes was influenced by both 17β-estradiol (E2) and a hypomethylating agent 5-aza-2’-deoxycytidine (DAC). Based on gene ontology (GO), CpG island prediction analysis and previously reported estrogen receptor (ER) binding regions, we selected six genes for further analysis (BTG3, FHL2, PMAIP1, BTG2, CDKN1A and TGFB2). GO analysis suggests that these genes are involved in intracellular signaling cascades, regulation of cell proliferation and apoptosis, while CpG island prediction of promoter regions reveals that the promoters of these genes contain at least one CpG island. Using chromatin immunoprecipitation, we show that ERα is recruited to CpG islands in promoters, but neither in an E2- nor in a DAC-dependent fashion. DAC treatment reactivates the expression of all selected genes although only the promoters of BTG3 and FHL2 genes are methylated, with E2 treatment showing no effect on the methylation status of these promoters. Conclusions: We identified a set of genes regulated by both estrogen signaling and DNA methylation. However, our data does not support a direct molecular interplay of mediators of estrogen and epigenetic signaling at promoters of regulated genes. The aim of the study was to identify genes regulated by estrogen signaling and DNA methylation, using microarray approach. We compared the effects of E2 and DAC on global gene expression profiles in MCF7 cells. By comparing C_E2 (MP5-MP8 average) with C_EtOh samples (MP1-MP4 average), 802 genes were identified as up-regulated by E2, while 851 genes were identified as down-regulated by E2. 1017 genes were identified as up-regulated by DAC, by comparing A_EtOh (MP9-MP12 average) samples with C_EtOh, suggesting that DNA methylation is involved in their regulation. To identify possible common targets, we have compared the DAC up-regulated genes with E2-regulated genes. 88 annotated genes are found to be up-regulated by both E2 and DAC, suggesting that E2 has a hypomethylation-like effect on the regulation of these genes. 58 annotated genes are found to be down-regulated by E2 and up-regulated by DAC, suggesting that E2 has a hypermethylation-like effect on the regulation of these genes.

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Complex regulation of LCoR signaling in breast cancer cells.

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Complex regulation of LCoR signaling in breast cancer cells.

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