Synergistic antitumor activity of oridonin and arsenic trioxide on hepatocellular carcinoma cells

Abstract

Although arsenic trioxide (As2O3) has been successfully employed in treatment of patients with APL (acute promyelocytic leukemia), the sensitivity of solid tumor cells to this treatment was much lower than APL cells. The single agent of As2O3 was inefficient for treatment of hepatocellular carcinoma (HCC) in phase II trial demonstrating that new modalities of treatment with enhanced therapeutic effect are needed. In this study, we showed that oridonin, a diterpenoid isolated from traditional Chinese medicine Rabdosia rubescences, greatly potentiated apoptosis induced by As2O3 in hepatocellular carcinoma cells. The synergistic pro-apoptosis effect of combination of these two drugs led to increase in intracellular reactive oxygen species (ROS) level and N-acetyl-L-cysteine (NAC), a thiol-containing anti-oxidant, was able to completely block the effect. The combination treatment induced ROS-dependent decrease in mitochondrial membrane potential (MMP) decrease, and relocation of Bax and cytochrome C. Besides, oridonin dramatically increased the intracellular Ca2+ overload triggered by As2O3.

 oridonin was obtained from Biopurify (Cheng Du, China).