Autophagy plays a pro-apoptotic role in arsenic trioxide-induced cell death of liver cancer

Objective

The effects of arsenic trioxide (As₂O₃) on hepatocellular carcinoma have been documented widely. 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 using the MTT assay with or without fetal bovine serum. The rate of apoptosis in liver cancer cells treated with As₂O₃ was evaluated using flow cytometry, Hoechst 33258 staining, and TUNEL assays. The rate of autophagy among liver cancer cells treated with As₂O₃ was detected using 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 cell lines increased with the concentration of As₂O₃, as shown by flow cytometry. Apoptosis in liver cancer cells treated with As₂O₃ was also shown by the activation of the caspase cascade and the regulation of Bcl-2/Bax expression. Furthermore, As₂O₃ treatment induced autophagy in liver cancer cells; this finding was supported by Western blot, immunofluorescence of LC3-II and beclin 1, and transmission electron microscopy. In liver cancer cells, As₂O₃ inhibited the phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (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-methyladenine partially reversed the negative effects of As₂O₃ on cell viability. Serum starvation increased autophagy and amplified the effect of As₂O₃ on cell death.

Conclusion

As₂O₃ induces apoptosis and autophagy in liver cancer cells. Autophagy induced by As₂O₃ may have a proapoptotic effect that helps to reduce the viability of liver cancer cells. This study provides novel insights into the effects of As₂O₃ against liver cancer.

Please cite this article as: Deng ZT, Liang SF, Huang GK, Wang YQ, Tu XY, Zhang YN, Li S, Liu T, Cheng BB. Autophagy plays a pro-apoptotic role in arsenic trioxide-induced cell death of liver cancer. J Integr Med. 2024; 22(3): 295–302.