The enrichment of histone acetyl-transferases (CBP/p300) and histone H3K4 trimethylases (MLL2 and MLL3) and the histone acetylation and H3K4 trimethylations at the HOXA5 promoter in the presence of E2 suggest their important roles in E2-mediated regulation of HOXA5 expression in breast cancer. The gene discussed is HOXA5; the disease is breast cancer.