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Gene expression profiles of MCF7 breast cancer cells following estrogen and anti-estrogen treatment

ABSTRACT: We have previously demonstrated that endoxifen is the most important tamoxifen metabolite responsible for eliciting the anti-estrogenic effects of this drug in breast cancer cells expressing estrogen receptor-alpha. The goals of this study were to compare the gene expression profiles elicited by endoxifen to that of other anti-estrogens in MCF7 cells. We also examined the gene expression profiles elicited by various endoxifen concentrations in the presence of tamoxifen and its other primary metabolites in order to better understand the molecular contributions of endoxifen to the effects of tamoxifen. Total RNA was isolated from parental MCF7 cells following 24 hour treatments with various individual or combined ligands. All studies were conducted in replicates of 3.

ORGANISM(S): Homo sapiens

SUBMITTER: Hawse John

PROVIDER: S-ECPF-GEOD-43702 | biostudies-other |

REPOSITORIES: biostudies-other

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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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Gene expression profiles of MCF7 breast cancer cells following estrogen and anti-estrogen treatment

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