Unknown,Transcriptomics,Genomics,Proteomics

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GR and ER co-activation alters the expression of differentiation genes and associates with improved ER+ breast cancer outcome

ABSTRACT: Analysis of MCF-7 cells treated for 4h with Ethanol, Estradiol (E2), Dexamethasone (Dex), or Estradiol + Dexamethasone (E2 + Dex) In estrogen receptor (ER)-negative breast cancer (BC), high tumor glucocorticoid receptor (GR) expression has been associated with a relatively poor outcome. In contrast, using a meta-analysis of several genomic datasets, here we find that tumor GR mRNA expression is associated with improved ER+ relapse-free survival (RFS) (independently of progesterone receptor (PR) expression). To understand the mechanism by which GR expression is associated with a better ER+ BC outcome, the global effect of GR-mediated transcriptional activation in ER+ BC cells was studied. Analysis of GR chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) in ER+/GR+ MCF-7 cells revealed that upon co-activation of GR and ER, GR chromatin association became enriched at proximal promoter regions. Furthermore, following ER activation, increased association of GR was observed at ER, FOXO, and AP1 response elements. In addition, it was determined that ER associated with GR response elements, suggesting that ER and GR interact in a complex. Co-activation of GR and ER resulted in increased expression (relative to ER activation alone) of transcripts that encode proteins promoting cellular differentiation (e.g. KDM4B, VDR) and inhibiting Wnt-signaling (IGFBP4). Finally, expression of these individual pro-differentiation genes was associated with significantly improved RFS in ER+ BC patients. Together, these data demonstrate that the co-expression and subsequent activity of tumor cell GR and ER contribute to the less aggressive natural history of early-stage BC by coordinating the altered expression of genes favoring differentiation. Four treatment samples (Vehicle V, Dex D, E2, or Dex+E2). Three biological replicate experiments per sample. Vehicle sample is Ethanol control.

ORGANISM(S): Homo sapiens

SUBMITTER: Suzanne Conzen

PROVIDER: E-GEOD-79761 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:HGU133+2.0 Microarray on TNBC cells (MDA-MB-231) treated for 4, 8, or 12h with vehicle, 100nM dexamethasone, 100nM Dex/100nM Mifepristone, or 100nM Dex/100nM CORT108297 Purpose: Although high glucocorticoid receptor (GR) expression in early-stage estrogen receptor (ER)-negative breast cancer (BC) is associated with shortened relapse-free survival (RFS), how associated GR transcriptional activity contributes to aggressive BC behavior is not well understood. Using potent GR antagonists and primary tumor gene expression data, we sought to identify a tumor-relevant gene signature based on GR activity that would be more predictive than GR expression alone. Design: Global gene expression and GR ChIP-sequencing were performed to identify GR-regulated genes inhibited by two chemically distinct GR antagonists, mifepristone and CORT108297. Differentially expressed genes from MDA-MB-231 cells were cross-evaluated with significantly expressed genes in GR-high versus GR-low ER-negative primary BCs. The resulting subset of GR targeted genes was analyzed in two independent ER-negative BC cohorts to derive and then validate the GR activity signature (GRsig). Results: Gene expression pathway analysis of glucocorticoid-regulated genes (inhibited by GR antagonism) revealed cell survival and invasion functions. GR ChIP-seq analysis demonstrated that GR antagonists decreased GR chromatin association for a subset of genes. A GRsig comprised of n=74 GR activation-associated genes (also reversed by GR antagonists) was derived from an adjuvant chemotherapy-treated Discovery cohort and found to predicted probability of relapse in a separate Validation cohort (HR=1.9; p= 0.012). Conclusions: The GRsig discovered herein identifies high-risk ER-negative/GR-positive BCs most likely to relapse despite administration of adjuvant chemotherapy. Because GR antagonism can reverse expression of these genes, we propose that addition of a GR antagonist to chemotherapy may improve outcome of these high-risk patients.

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GR and ER co-activation alters the expression of differentiation genes and associates with improved ER+ breast cancer outcome

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