Tetrandrine induces autophagy of ovarian cancer cells by inhibiting PI3K/Akt/mTOR signaling pathway

AIM To investigate the effect of tetrandrine on the autophagy of human ovarian serous cystadenocarcinoma SKOV3 cells, and to explore its molecular mechanism. METHODS The SKOV3 cells were treated with various concentrations of tetrandrine, and the cell viability was measured by MTT assay. The formation of autophagolysosomes was observed by acridine orange staining under fluorescence microscope. The protein levels of LC3, mTOR, p-mTOR, Akt and p-Akt in the SKOV3 cells were determined by Western blot. The viability of the SKOV3 cells treated with tetrandrine alone or combined with autophagy inhibitor 3-methyladenine (3-MA) were measured by MTT assay. RESULTS Tetrandrine significantly inhibited the viability of SKOV3 cells in a dose-dependent manner (P<0.01). The results of acridine orange fluorescence staining showed that the number of intracellular autophagolysosomes with bright red fluorescence in the SKOV3 cells was significantly increased after tetrandrine treatment, while the autophagolysosomes were rarely observed in control group. The protein levels of LC3-II and P62 in the SKOV3 cells were significantly increased after tetrandrine treatment (P<0.01). Furthermore, treatment with tetrandrine resulted in significant down-regulation of phosphorylated form of mTOR and AKT in the SKOV3 cells (P<0.01), while total mTOR and AKT protein levels were not changed. Finally, combination of tetrandrine and 3-MA significantly decreased the cell viability compared with using tetrandrine alone (P<0.01). CONCLUSION The autophagy of human ovarian cancer SKOV3 cells were induced by tetrandrine and the molecular mechanism may be related to inhibition of PI3K/Akt/mTOR signaling pathway．