ESR1 and breast cancer: Of the 18 ChIP-seq datasets, six histone modifications, including histone H3 lysine 4 methylations (H3K4me1, H3K4me3), lysine 9 trimethylation (H3K9me3), lysine 27 trimethylation (H3K27me3), lysine 36 trimethylation (H3K36me3), and histone H3 lysine 27 acetylations (H3K27ac), were conducted in each of the HCC1954 cell line, an estrogen receptor negative (ER−) breast cancer cell line, MCF-7 cell line, an estrogen receptor positive (ER+) breast cancer cell line, and human mammary epithelial cells (HMEC), a normal breast cell line.