CCND1 and breast cancer: ERα co-activators CBP/p300, functioning as histone acetyltransferases (HATs), enhance H3K27ac for facilitating ERα-mediated transcriptional activity, whereas pharmacological inhibition of CBP/p300 by A-485 and GNE-049 could downregulate ERα to suppress oncogenic c-Myc and cyclin D1 expression and the proliferation of ERα+ BC cells (4, 14, 15).