The ESR1 enrichment is of particular significance as ESR1 encodes the estrogen receptor (ER), the defining TF of this class of breast cancer. To further evaluate the ER binding sites as defined by in vivo occupancy, we used the ER cistrome previously defined by chromatin immunoprecipitation in MCF-7 cells (Carroll et al., 2006). The regions within the 6q24 gene set computationally predicted to bind ER by the presence of an ER DNA binding motif are significantly enriched for in vivo ER binding sites defined by chromatin immunoprecipitation (P <1×10-6).
