Sarmentosin Induces Autophagy-dependent Apoptosis via Activation of Nrf2 in Hepatocellular Carcinoma.

Background and aims: Hepatocellular carcinoma (HCC) is a common and deadly cancer. Accumulating evidence supports modulation of autophagy as a novel approach for determining cancer cell fate. The aim of this study to evaluate the effectiveness of sarmentosin, a natural compound, on HCC in vitro and in vivo and elucidated the underlying mechanisms.

Methods: Cell functions and signaling pathways were analyzed in HepG2 cells using western blotting, real-time PCR, siRNA, transmission electron microscopy and flow cytometry. BALB/c nude mice were injected with HepG2 cells to produce a xenograft tumour nude mouse model for in vivo assessments and their tumors, hearts, lungs and kidneys were isolated.

Results: We found that autophagy was induced by sarmentosin in a concentration- and time-dependent manner in human HCC HepG2 cells by western blot assays and scanning electron microscopy. Sarmentosin-induced autophagy was abolished by the autophagy inhibitors 3-methyladenine, chloroquine, and bafilomycin A1. Sarmentosin activated Nrf2 in HepG2 cells, as shown by increased nuclear translocation and upregulated expression of Nrf2 target genes. Phosphorylation of mTOR was also inhibited by sarmentosin. Sarmentosin stimulated caspase-dependent apoptosis in HepG2 cells, which was impaired by silencing Nrf2 or chloroquine or knocking down ATG7. Finally, sarmentosin effectively repressed HCC growth in xenograft nude mice and activated autophagy and apoptosis in HCC tissues.

Conclusions: This study showed sarmentosin stimulated autophagic and caspase-dependent apoptosis in HCC, which required activation of Nrf2 and inhibition of mTOR. Our research supports Nrf2 as a therapeutic target for HCC and sarmentosin as a promising candidate for HCC chemotherapy.