TP53 and breast cancer: Our results that knockout of BRD4 significantly blocked colony formation in the TNBC cells lines MDA-MB-231, MDA-MB-468, and HS578T carrying mutant p53, while it only slightly decreased the colony formation of MCF-7 cells that carry wild-type p53, suggesting that the sensitivity of the breast cancer cells’ response to the BET inhibitor might be dependent on the status of p53.