MCL1, which is overexpressed in many cancers, is another important pro-survival protein in BCL2 family.20 There are some MCL1-dependent tumors, such as breast cancer, acute myelocytic leukemia (AML) and non-small cell lung cancer (NSCLC).38, 39, 40, 41 Upon these cancers, BCL2 or BCL-XL inhibitors did not work well. This evidence concerns the gene MCL1 and breast cancer.