The functional state of chromatin has been defined largely by the covalent modifications of the histones, with their specific patterns serving as indicators of transcriptional activity.[22] To further confirm that epigenetic activation of POU4F1 is responsible for its high expression in BLBC, we investigated the histone modification of POU4F1 in different subtypes of breast cancer cell lines and normal breast epithelial cells. The gene discussed is POU4F1; the disease is breast cancer.