To better elucidate the potential mechanism of the enhanced effects of carfilzomib on DOX-induced apoptosis in breast cancer cells, we first assessed the effects of the combination of CFZ with DOX on the activity of NF-κB, SAPK/JNK, and p38 MAPK in 7 subtypes of breast cancer cell lines. This evidence concerns the gene MAPK8 and breast carcinoma.