TSA inhibits HDAC activity [69], downregulates HDAC1 expression [75], increases histone H4 [69] and estrogen receptor (ER) acetylation in breast cancer cell lines [76], increases histone H3 lysine 9 and lysine 27 acetylation [76] and upregulates p21, p27 and p57 expression in colon cancer cell lines [75] Additionally, in PCa, TSA increases histone H4 lysine 16 acetylation, particularly in CRPC cell lines [73], and affects p53 acetylation [49]. This evidence concerns the gene ESR1 and breast cancer.