Gene Regulation by Estrogen Signaling and DNA Methylation in MCF7 Breast Cancer Cells

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 17-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 ER 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.

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Putnik M, Zhao C, Gustafsson JÅ, Dahlman-Wright K