Abstract: OBJECTIVE:To observe the effects of oridonin on proliferation and apoptosis of myeloma RPMI8226cells and to investigate the potential underlying mechanisms.METHODS:RPMI8226 cells were treated with various concentrations of oridonin.Cell proliferation was analyzed using the thiazolyl blue tetrazolium bromide method.Ultramicrostructure was observed by transmission electron microscopy.Annexin-V/PI staining and flow cytometry was performed to determine cell apoptosis.Expression of apoptosis-related proteins was evaluated by western blot analysis.RESULTS:Oridonin suppressed the proliferation of RPMI8226 cells and induced apoptosis in a timeand dose-dependent manner.Transmission electron microscopy confirmed apoptotic morphologyupon treatment with 20μmol/L oridonin and western blot revealed decreased expressions of the apoptosis suppressors survivin,Bcl-2 and pro-caspase-3 proteins,and the increased expression of the apoptosis inducer Bax.CONCLUSION:Our results show that oridonin exhibits an inhibitory effect on the proliferation of RPMI8226 cells and induces apoptosis.This is associated with altering the balance between Bcl-2 and Bax protein expressions and decreased survivin and pro-caspase-3 expressions.

Key words: Oridonin, Multiple myeloma, Apopto sis, Survivin, Bcl-2-associated X protein, Caspase 3