Cbp/p300 bromodomain inhibitor–i–cbp112 declines transcription of the key abc transporters and sensitizes cancer cells to chemotherapy drugs

Abstract

The high expression of some ATP‐binding cassette (ABC) transporters is linked to mul-tidrug resistance in cancer cells. We aimed to determine if I‐CBP112, which is a CBP/p300 bromo-domain inhibitor, altered the vulnerability of the MDA‐MB‐231 cell line to chemotherapy drugs, which are used in neoadjuvant therapy in patients with triple negative breast cancer (TNBC). MDA‐MB‐231 cells represent TNBC, which is negative for the expression of estrogen and proges-terone receptors and HER2 protein. An I‐CBP112‐induced decrease in the expression of all the studied ABCs in the breast, but also in the lung (A549), and hepatic (HepG2) cancer cell lines was associated with increased accumulation of doxorubicin, daunorubicin, and methotrexate inside the cells as well as considerable cell sensitization to a wide range of chemotherapeutics. Gene promoters repressed by I‐CBP112 in MDA‐MB‐231 cells, such as ABCC1 and ABCC10, were charac-terized by enhanced nucleosome acetylation and, simultaneously, by considerably lower tri-methylation in the transcription‐promoting form of H3K4me3. The CBP/p300 bromodomain in-hibitor induced the recruitment of LSD1 to the gene promoters, and the inhibition of this deme-thylase in the presence of I‐CBP112 prevented the repression of ABCC1 and ABCC10 and, to a considerable extent, cancer cells’ sensitization to drugs. In conclusion, the CBP/p300 bromodomain inhibitor I‐CBP112 can be considered as a potent anti‐multidrug‐resistance agent, capable of re-pressing key ABC transporters responsible for drug efflux in various cancer types.