TTF1-NP induces protective autophagy during apoptosis by inhibiting the Akt/mTOR pathway and activating JNK in human liver cancer cells

Abstract

TTF1-NP is a flavonoid nanoparticle based on 5,2′,4′-trihydroxy-6,7,5′-trimethoxyflavone (TTF1), which is derived from the medicinal plant Sorbaria sorbifolia that grows in the Changbai Mountain. We previously demonstrated antitumor effects of TTF1-NP in human hepatoma including induction of apoptosis and inhibition of angio-genesis, migration and invasion. Herein, we examined the effects of TTF1-NP on autophagy and its relationship with apoptosis, and explored potential underlying mechanisms in human hepatoma cell lines. We conducted cell viability assays, Annexin V/propidium iodide double staining, Hoechst staining, monodansylcadaverine staining, transmission electron microscopy, green fluorescent protein-light chain 3 plasmid transfection and western blots. We found that TTF1-NP induced apoptosis and autophagy in HepG2 and SMMC-7721 cells. Pretreatment with the autophagy inhibitor 3-methyladenine promoted TTF1-NP-induced apoptosis. TTF1-NP decreased levels of phosphorylated (p)-Akt, p-mTOR and p-ERK1/2 and increased p-JNK levels in the two cell lines. Treating cells with insulin, SP600125 and U0126 indicated that the Akt/mTOR pathway and JNK were involved in TTF1-NP-induced autophagy. Together, these findings suggest that TTF1-NP induced protective apoptosis-related autophagy by modulating the Akt/mTOR and JNK pathways in HepG2 and SMMC-7721 cells. Therefore, autophagy may be a potential target for TTF1-NP in human hepatoma therapy.