To explore the effects of proteasome inhibitor PS-341 on the cytokine expressions of mesenchymal stem cells (MSC) in patients with multiple myeloma (MM), MSCs of 11 patients were cultured in medium of RPMI 1640 containing 10% FBS. When cells grew to 5 x 10(5) - 1 x 10(6), cells were exposed to 50 nmol/L PS-341 for 4 hours, then harvested. The expressions of IL-6, IL-1beta and SCF were detected by RT-PCR. The results indicated that after treatment with PS-341 the expressions of IL-6, IL-1beta and SCF of MSCs decreased markedly, especially that of IL-1beta, compared with control (P < 0.05, P < 0.01, P < 0.05, respectively). There were obviously differences of IL-1beta expression between refractory/relapsed group and complete remission (CR) group and IL-1beta expression was inhibited more seriously in CR group, whereas there were no significant differences of IL-6 and SCF expression between two groups; IL-1beta expression of patients treated with PS-341 was not detected; there were not effects of IL-1beta expression on expressions of IL-6 and SCF. It is concluded that proteasome inhibitor PS-341 downregulated the expressions of IL-6, IL-1beta and SCF of MSCs in patients with MM.