Previous studies on estrogen receptor α (ERα) and estrogen binding sites (ERBS) in breast cancer cell lines have shown a particular class of eRNAs that are mostly upregulated by estrogen; furthermore, features such as open chromatin, and enrichment of H3K4me1, p300/CBP, and RNA polymerase II are enhanced when estrogen-associated eRNA production is promoted [6,28]. This evidence concerns the gene ESR1 and breast cancer.