Co-regulated gene expression by oestrogen receptor α and liver receptor homolog-1 is a feature of the oestrogen response in breast cancer cells

Oestrogen receptor alpha (ER alpha) is a nuclear receptor that is the driving transcription factor expressed in the majority of breast cancers. Recent studies have demonstrated that the liver receptor homolog-1 (LRH-1), another nuclear receptor, regulates breast cancer cell proliferation and promotes motility and invasion. To determine the mechanisms of LRH-1 action in breast cancer, we performed gene expression microarray analysis following RNA interference for LRH-1. Interestingly, gene ontology (GO) category enrichment analysis of LRH-1-regulated genes identified oestrogen-responsive genes as the most highly enriched GO categories. Remarkably, chromatin immunoprecipitation coupled to massively parallel sequencing (ChIP-seq) to identify genomic targets of LRH-1 showed LRH-1 binding at many ER alpha binding sites. Analysis of select binding sites confirmed regulation of ER alpha-regulated genes by LRH-1 through binding to oestrogen response elements, as exemplified by the TFF1/pS2 gene. Finally, LRH-1 overexpression stimulated ER alpha recruitment, while LRH-1 knockdown reduced ER alpha recruitment to ER alpha binding sites. Taken together, our findings establish a key role for LRH-1 in the regulation of ER alpha target genes in breast cancer cells and identify a mechanism in which co-operative binding of LRH-1 and ER alpha at oestrogen response elements controls the expression of oestrogen-responsive genes.