Inhibition of Nasopharyngeal Carcinoma by Beta-Lapachone Occurs by Targeting the Mammalian Target of Rapamycin (mTOR)/PI3K/AKT Pathway, Reactive Oxygen Species (ROS) Production, and Autophagy Induction.

ABSTRACT

BACKGROUND Beta-lapachone has been shown to exhibit potent anti-cancer effects against various cell lines. In the present study, we examined the anti-cancer effects of beta-lapachone, a quinone, against human HNE1 nasopharyngeal carcinoma cells, and also assessed its effects on cellular migration and invasion, autophagy, mTOR/PI3K/AKT signalling pathway, and ROS production. MATERIAL AND METHODS CCK-8 cell counting assay was used to assess cell viability effects after lapachone treatment. Its effects on the mTOR/PI3K/AKT biochemical pathway were examined by Western blot analysis. Transmission electron microscopy was used to study autophagy induced by beta-lapachone. Effects on cell invasion and cell migration were evaluated by Transwell method. RESULTS The results revealed that beta-lapachone suppresses the proliferation of HNE1 cells, with an IC50 of 30 µM. These growth-inhibitory effects of beta-lapachone were found to be dose-dependent. The investigation of the effects of beta-lapachone on the mTOR/PI3KAKT signalling pathway showed that beta-lapachone blocked this pathway in a concentration-dependent manner. Beta-lapachone also inhibited the migration and invasion of HNE1 nasopharyngeal cancer cells, as shown by Transwell assay. The fluorescence microscopy analysis showed that beta-lapachone increased production of reactive oxygen species (ROS), which is also linked with a concentration-dependent decrease in mitochondrial membrane potential (MMP) levels. Electron microscopy analysis showed that beta-lapachone caused the development of the autophagosomes, and the frequency of the autophagosomes increased with increased dosage of beta-lapachone. The beta-lapachone-triggered autophagy was also associated with increased protein levels of LC3 II and decreased levels of p62. CONCLUSIONS The findings of this study suggest that beta-lapachone inhibits the growth of nasopharyngeal cancer cells by promoting autophagy, and it may be useful in cancer drug discovery paradigms.