Knowing that I-CBP112 allowed for a higher drug concentration in the breast cancer cell line and phenocopied iABC in terms of drug accumulation and cell sensitization to anticancer therapeutics, and that I-CBP112 altered nucleosome acetylation, we verified if the CBP/EP300 inhibitor affected the transcription and protein levels of ABC proteins, which, according to the literature, contribute to multidrug resistance. The gene discussed is EP300; the disease is breast cancer.