Finally, we confirm that through up-regulating the protein level of Eg5, TRAF4 down-regulates the protein level of Cleaved Caspase-3, pro-apoptotic protein Bax, and up-regulates the anti-apoptotic protein Bcl-2, indicating that TRAF4 inhibits breast cancer cell apoptosis by up-regulating the protein level of Eg5 protein. Here, BAX is linked to breast cancer.