MCL1 and breast cancer: Myeloid cell leukemia 1 (MCL1) is a pro-survival protein overexpressed in a variety of different cancers, such as lymphoma, leukemia, breast cancer, and MM.271 MCL1 can combine with pro-apoptotic factors Bim, Bak, and Bax by PPI and silence their proapoptotic functions.272 Therefore, MCL1 has been regarded as a critical survival factor in human cancers.