Objective To observe the impact of matrine on apoptosis of multiple myeloma and the possible mechanism. Methods Human multiple myeloma cell lines RPMI 8226 and U266 were given matrine in different concentration（ 0. 25

0. 5

1. 0

or 2. 0 mg / ml）. Proteasome inhibitor MG132 was set to be positive control. The inhibition rate of matrine to multiplication of two types of cells was determined adopting methyl thiazolyl tetrazolium（ MTT）method. Early apoptosis level of two types of cells was detected by flow cytometry. Expression changes of ubiquitin（ Ub）

20 S core particle（ p Ab） and NF-κB signaling pathway related proteins（ p-NF-κB p65 B

IκBα

p-IκBα

IKKα） of two cell lines were detected with Western-blot method. Results Under the action of matrine in the same concentration

the inhibitory rate of cell proliferation of two cell lines at the 48 th hour was much higher than that at the 24 th hour（ P < 0. 05 or P < 0. 01）. With the increasing of matrine concentration

the apoptosis rate of all cell lines increased gradually（ P < 0. 05 or P < 0. 01）. With the increasing of matrine effective concentration

Ub level in RPMI 8226 cells up-regulated and p Ab decreased progressively. While Ub expression did not change obviously

but p Ab expression decreased in U266 cells. Matrine might inhibit the expressions of p-NF-κB p65 B inside cell nucleus and p-IκBαinside cytoplasm and up-regulate the expression of IκBαinside RPMI 8226 cytoplasm in two cell lines

especially when the concentration was 2. 0 mg / ml（ P < 0. 5 or P < 0. 01）. Conclusion Matrine might promote apoptosis of multiple myeloma cells with some concentration-time dependence. The critical factor might be that matrine inhibits the activity of proteasome.