Dataset Information

Genomics of signalling crosstalk of estrogen receptor alpha in breast cancer cells

ABSTRACT: The estrogen receptor a (ERa) is a ligand-regulated transcription factor. However, a wide variety of other extracellular signals can activate ERa in the absence of estrogen. The impact of these alternate modes of activation on gene expression profiles has not been characterized. We show that estrogen, growth factors and cAMP elicit surprisingly distinct ERa-dependent transcriptional responses in human MCF7 breast cancer cells. In response to growth factors and cAMP, ERa primarily activates and represses genes, respectively. The combined treatments with the antiestrogen tamoxifen and cAMP or growth factors regulate yet other sets of genes. In many cases, tamoxifen is perverted to an agonist, potentially mimicking what is happening in certain tamoxifen-resistant breast tumors and emphasizing the importance of the cellular signaling environment. Using a computational analysis, we predicted that a Hox protein might be involved in mediating such combinatorial effects, and then confirmed it experimentally. Although both tamoxifen and cAMP block the proliferation of MCF7 cells, their combined application stimulates it, and this can be blocked with a dominant-negative Hox mutant. Thus, the activating signal dictates both target gene selection and regulation by ERa, and this has consequences on global gene expression patterns that may be relevant to understanding the progression of ERa-dependent carcinomas. Keywords: treatment response

ORGANISM(S): Homo sapiens

PROVIDER: GSE10466 | GEO | 2008/05/22

SECONDARY ACCESSION(S): PRJNA108025

REPOSITORIES: GEO

ACCESS DATA

Dataset's files

Source:

			Action	DRS
		Other

Items per page:

1 - 1 of 1

Similar Datasets

Project description:Targeting the estrogen signaling pathway has proved to be of great value in the treatment of human breast cancer. Tamoxifen, a selective estrogen receptor modulator (SERM), is the most widely used antiestrogen. However, only 40-50% of patients with estrogen receptor (ER) positive breast cancer benefit from tamoxifen treatment and 30-50% acquire resistance and the disease progresses. Continuous treatment with conventional therapy may contribute to cancer progression in recurring cancers through the accumulation of drug resistant cancer progenitors. We found that MCF7 tamoxifen-resistant (TAM-R) cells possess a significantly higher proportion of cancer progenitor cells than tamoxifen-sensitive MCF7 cells. Our results indicate that the chemokine receptor CXCR4 plays an important role in the maintenance of cancer progenitors in a tamoxifen-resistant cell line and downregulation of CXCR4 signaling by small molecule antagonists specifically inhibits growth of a stem-like cell population in tamoxifen-resistant tumors both in vitro and in vivo. Whole genome gene expression analysis revealed aryl hydrocarbon receptor (AhR) signaling as one of the top networks that is differentially regulated in MCF7(TAM-R) xenograft tumors treated with the CXCR4 antagonist AMD3100 as compared to MCF7 tumors. Further, small molecule antagonists of AhR signaling specifically inhibit the progenitor population in MCF7(TAM-R) cells suggesting that the aryl hydrocarbon receptor could be a putative target for the treatment of tamoxifen-resistant breast cancers. Introduction transplants remains limited by the ability to expand these cells ex vivo. An unbiased screen with primary human HSCs identified a purine derivative, StemRegenin 1 (SR1), that promotes the ex vivo expansion of CD34+ cells. Culture of HSCs with SR1 led to a 50-fold increase in cells expressing CD34 and a 17-fold increase in cells that retain the ability to engraft immunodeficient mice. Mechanistic studies show that SR1 acts by antagonizing the aryl hydrocarbon receptor (AHR). The identification of SR1 and AHR modulation as a means to induce ex vivo HSC expansion should facilitate the clinical use of HSC therapy. Tamoxifen resistant or sensitive xenografts; mice treated with estrogen and/or CXCR4 modulators

Project description:Altered expression of microRNAs (miRNAs), an abundant class of small non-protein-coding RNAs that mostly function as negative regulators of protein-coding gene expression, is common in cancer. Here we analyze the regulation of miRNA expression in response to estrogen, a steroid hormone that is involved in the development and progression of breast carcinomas and that is acting via the estrogen receptors (ER) transcription factors. We set out to thoroughly describe miRNA expression, by using miRNA microarrays and real time RTPCR experiments, in various breast tumor cell lines in which estrogen signaling has been induced by 17β-estradiol (E2). We show that the expression of a broad set of miRNAs decreases following E2 treatment in an ER-dependent manner. We further show that enforced expression of several of the repressed miRNAs reduces E2-dependent cell growth, thus linking expression of specific miRNAs with estrogen-dependent cellular response. In addition, a transcriptome analysis revealed that the E2-repressed miR-26a and miR-181a regulate many genes associated with cell growth and proliferation, including the progesterone receptor gene, a key actor in estrogen signaling. Strikingly, miRNA expression is also regulated in breast cancers of women who had received antiestrogen neoadjuvant therapy thereby showing an estrogen-dependent in vivo regulation of miRNA expression. Overall, our data indicates that the extensive alterations in miRNA regulation upon estrogen signalling pathway plays a key role in estrogen-dependent functions and highlights the utility of considering miRNA expression in the understanding of antiestrogen resistance of breast cancer. 9 samples analyzed. Triplicates were done. MCF-7+miR26a+E2 (n=1 to 3) ; MCF7+miRctrl+E2 (n=1 to 3) ; MCF7+miRctrl+vehicle (n=1 to 3). We generated pairwise comparisons using EASANA from GenoSplice technology: MCF-7+miR26a+E2 versus MCF7+miRctrl+E2 and MCF-7+miRctrl+E2 versus MCF7+miRctrl+vehicle. Fold change ≥1.5 were selected.

Dataset Information

Genomics of signalling crosstalk of estrogen receptor alpha in breast cancer cells

Dataset's files

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets