Objective      To investigate the effect of ebselen on the proliferation and apoptosis in multiple myeloma (MM) cells and its probably mechanism.       Methods      Cell viability of human MM cell line U266 was examined by CCK-8 assay kit after treated by ebselen at 0，5，10，20，25，30，35 and 40 μmol/L for 8

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48 or 72 h. The production of reactive oxygen species (ROS) was measured by Singlet ROS Probe. JC-1 dye was used to assay the mitochondrial membrane potential (△Ψm). The apoptosis assay was done through Hoechst staining. The protein levels of Bcl-2

Bax

caspase 9 and cytochrome C were detected by Western blotting.       Results      Ebselen was found to significantly decrease cell viability and increase apoptosis accompanied by enhancing production of ROS in U266 cells. Further studies revealed cytochrome C was released from the mitochondria to cytosol accompanied by mitochondrial membrane potential △Ψm decrease

while caspase 9 was not observed to be activated.        Conclusion      Ebselen may enhance the production of endogenous ROS

and induce MM cell apoptosis via mitochondria-mediated apoptotic pathway.