Abstract: Objective To investigate whether overexpression of TRAF4 in human breast cancer may impact its cell proliferation. Methods This study had two groups, MDA-MB-231 transfected with pcDNA3-TRAF4-DM-TRAF or pcDNA3. We detected the expression and localization of TRAF4 with immunofluorescence and western blot. We detected the expression of the phosphorylation level of p70S6K and S6 with westernblot. Flow cytometry detected the cell cycle. MTT Assay detected the cell reproductive capacity. Results TRAF4 localized in both cytoplasm and nuclei in MDA-MB-231. Nuclear expression of TRAF4 in nuclei was lower than that in cytoplasm (P <0.05). After pcDNA3-TRAF4-DM-TRAF was transfected into the cells, the expression of TRAF4 in nuclei was increased (P <0.05). The phosphorylation level of p70S6K and S6 significantly increaseced ( P <0.05，P < 0.01). More S phase cells were detected (P < 0.01) by FCM . The cell proliferation was promoted by MTT (P < 0.01). Conclusion The expression of TRAF4 in nuclei may play an important in the cell proliferatuion by promoting p70S6K and S6 activation.

Key words: Breast cancer, TRAF4, Cell proliferation