Triptolide-induced apoptosis by inactivating nuclear factor-kappa B apoptotic pathway in multiple myeloma in vitro

The effect of triptolide on proliferation and apoptosis of human multiple myeloma RPMI-8226 cells in vitro, as well as the roles of nuclear factor-kappa B (NF-kappa B) and I kappa B alpha was investigated. The effect of tritptolide on the growth of RPMI-8226 cells was studied by MTT assay. Apoptosis was detected by Hoechest 33258 staining and Annexin V/PI double staining assay. The expression of NF-kappa B and I kappa B alpha was observed by Western blot and confocal microscopy. The results showed that triptolide inactivated NF-kappa B apoptotic pathway in human multiple myeloma RPMI-8226 cells. Triptolide at nM range induced proliferation inhibition in a dose- and time-dependent manner and apoptosis in a dose-dependent fashion in RPMI-8226 cells. Besides, we observed the inhibition of NF-kappa B /p65 in the nuclear fraction was correlated with the increase in the protein expression of I kappa B alpha in the cytosol. These results suggested that triptolide might exhibit its strong anti-tumor effects via inactivation of NF-kappa B/p65 and I kappa B alpha.