In order to confirm the role of TRAF4 and Eg5 in the development of breast cancer in vivo, we transplanted breast tumours developed from MCF-7 cells, which were stably transfected with empty plasmid or TRAF4 overexpressed pasmid or both TRAF4 overexpressed pasmid and Eg5 sh-RNAs into nude mice. The gene discussed is TRAF4; the disease is breast cancer.