Objective: Effects of arsenic trioxide (As2O3) on hepatocellular carcinoma (HCC) has been documented widely. In addition, autophagy plays dual roles in the survival and death of cancer cells. Therefore, we investigated the exact role of autophagy in As2O3 -induced apoptosis in liver cancer cells.
Methods: The viability of hepatoma cells was determined with MTT assay. The apoptosis of As2O3-induced liver cancer cells was evaluated by flow cytometry, Hoechst 33258 staining and TUNEL assays. The autophagy of liver cancer cell was detected by immunofluorescence, western blot assay and transmission electron microscopy.
Results: Upon treatment with As2O3, the viability of HepG2 and SMMC-7721 cells was decreased in a time- and dose-dependent manner. The apoptosis rates of both liver cancer cells increased with the concentration of As2O3 as determined by Flow cytometry. Apoptosis in liver cancer cells induced by As2O3 was also demonstrated by the activation of the caspase cascade and the regulation of Bcl-2/Bax expression. Furthermore, we also found that As2O3 treatment induced liver cancer cells autophagy, which was demonstrated by western blot, immunofluorescence of LC3-II and Beclin 1 expression and transmission electron microscopy observation. In liver cancer cells, As2O3 inhibited the PI3K/AKT/mTOR signal pathway that plays a vital role in both apoptosis and autophagy. The PI3K activator, SC-79 partially reversed As2O3-induced autophagy and apoptosis. Furthermore, inhibiting autophagy with 3-MA partially reversed As2O3-induced cell viability inhibition, and enhanced autophagy with serum starvation facilitated As2O3-induced cell death.
Conclusion: As2O3 is able to induce liver cancer cells apoptosis and autophagy. Autophagy induced by As2O3 may play a proapoptotic effect in the anti-liver cancer effects. Our present study provides novel insights into the anti-liver cancer effects of As2O3.

Key words: Apoptosis, Arsenic trioxide, Autophagy, Primary liver cancer