Research Resource: Interplay between the Genomic and Transcriptional Networks of Androgen Receptor and Estrogen Receptor α in Luminal Breast Cancer Cells

The cellular response to circulating sex steroids is more than the sum of individual hormone actions, instead representing an interplay between activities of the evolutionarily related steroid hormone receptors. An example of this interaction is in breast cancer, where the risk of dying from estrogen receptor-alpha (ER alpha)-positive disease decreases approximately 4-fold when androgen receptor (AR) expression is high. In this study, we used chromatin immunoprecipitation sequencing (ChIP-seq) and microarray expression profiling to investigate the genomic and transcriptional cross talk between AR and ER alpha signaling in a luminal breast cancer cell line model, ZR-75-1. Expression profiling demonstrated reciprocal interference between 5 alpha-dihydrotestosterone (DHT)- and 17 beta-estradiol (E-2)-induced transcriptional programs. Specifically, regulation of 26% of E-2 and 15% of DHT target genes was significantly affected by cotreatment with the other hormone, in the majority of cases (78-83%) antagonistically. Pathway analysis suggested that DHT cotreatment, for example, depleted E-2-regulated pathways in cell survival and proliferation. ChIP-seq identified substantial overlap between the steroid receptor cistromes in ZR-75-1 cells, with 10-13% of AR- and ER alpha-binding sites located within 10 kb of the other receptor. Enrichment of androgen response elements in ER alpha-binding sites and vice versa was revealed by motif analysis, and AR-binding sites were enriched about E-2-responsive genes affected by DHT cotreatment. Targeted ChIP and expression analysis revealed locus-specific outcomes when AR and ER alpha bind to the same DNA region. This work provides the first cistrome data for two steroid receptors in the same cell, insight into the antagonistic interplay between estrogens and androgens in luminal breast cancer, and an important resource for future work aimed at evaluating interrelated steroid receptors in different cellular systems. (Molecular Endocrinology 26: 1941-1952, 2012)