Objective To observe the inhibitory effect of Hedyotis Diffusa Injection （HDI） on the proliferation of multiple myeloma （MM） cell lines RPMI 8226 and U266 and its mechanism. Methods The RPMI 8226 and U266 cells of 1×106/ml concentration were seeded into the RPMI 1640 culture solution with 10% fetal bovine serum

100 U/ml penicillin and 100 μg/ml streptomycin. The cells in logarithmic growth phase were selected to do the experiment. The inhibitory effect of HDI on RPMI 8226 and U266 was detected and the concentration was screened. The effect of HDI with different concentrations on the apoptosis

cell cycle

cytokines and cell lines related gene mRNA of RPMI 8226 and U266 was observed. Results There were 0

20

40 and 60 μl/ml concentrations of HDI selected on RPMI 8226 and U266. HDI could inhibit the proliferation of RPMI 8226 and U266 and induce RPMI 8226 apoptosis with G1/S phase arrest. HDI could down-regulate the vascular endothelial growth factor （VEGF） level of RPMI 8226 and U266 supernatant with concentration dependence. HDI could up-regulate the interleukin-6 （IL-6） level of RPMI 8226 and down-regulate the IL-6 level of U266 （P<0.05 or P<0.01）. The expression of RPMI 8226 and U266 cell lines related genes was changed after processed by 40μl/ml HDI except Bax and Caspase-3 （P<0.05 or P<0.01）. Conclusion HDI can inhibit the proliferation of RPMI 8226 and U266 cells

which may be relevant to promoting apoptosis

arresting cell cycle and changing cytokines and expression of cells related gene mRNA with different way.