Abstract: Objective To explore the expression of MCUR1 in MM patients, and to analyze the effect and molecular mechanism of MCUR1 on the cell cycle and apoptosis of MM cells lines. Methods The leukemia RPMI 8226 cells transiently transfected with the MCUR1 small interfering RNA1 and 2 were used as experimental groups (siMCUR1-1 and siMCUR1-2), and paralleled with negative control siRNA (siCtrl) as the control group. The mRNA expression of MCUR1 in MM patients and control group was analyzed by real-time PCR. The effect of silencing MCUR1 was detected by real-time PCR and Western blot. The effects of MCUR1 on the cell growth, cell cycle and apoptosis in RPMI 8226 cells were detected by using CCK-8 and flow cytometry respectively. Detection the protein expression of p53 and its downstream molecular by Western blot. Results Compared with normal group, the MCUR1 mRNA expression in MM patients was higher (P<0.05). Compared with the control group, the cell growth of the siMCUR1 groups were significantly decreased in RPMI 8226 cells (P<0.05), and the percentage of siMCUR1 cells in G1 phase was significantly increased，while the percentage of siMCUR1 cells in S phase was significantly decreased. The apoptosis percentage of siMCUR1 cells was higher than that in the control cells. The protein level of p53 and BAX in the siMCUR1 cells were higher than that in the control cells, while the protein level of BCL2, Cyclin D1 and Cyclin E in the siMCUR1 cells were lower than that in the control cells. Conclusions The expression of MCUR1 is raised in MM patients, while MCUR1 promotes MM cells growth through down-regulation of p53.

Key words: MCUR1, cell cycle, apoptosis, p53, multiple myeloma