Theaflavin promoted apoptosis in nasopharyngeal carcinoma unexpectedly via inducing autophagy in vitro

OBJECTIVE(S): This study aimed to investigate the mechanism of the anticancer effect of theaflavin (TF) in nasopharyngeal carcinoma. MATERIALS AND METHODS: CNE2 cells were used to study the anticancer effect of TF. This study used Cell Counting Kit-8 (CCK8) assay on proliferation and used flow cytometry to detect apoptosis. The protein expression of Bcl-2, Bax, caspase 3, and caspase 9 was detected by Western blot, and autophagy-related proteins were also detected. RESULTS: TF inhibited proliferation of CNE2 cells, promoted apoptosis, and up-regulated the expression of caspase 3, caspase 9, and Bax, and decreased the level of Bcl-2. Unexpectedly, TF induced autophagy rather than inhibiting autophagy through up-regulating the levels of the autophagy marker light chain 3 (LC3) and Lysosomal-associated membrane protein 1 (LAMP1) and reducing levels of the autophagosome cargo protein p62, and the effect was via the mTOR pathway. Besides, autophagy inhibitor Chloroquine (CQ) suppressed the effect of TF on Bax, Bcl-2 and activation of caspase 3 and caspase 9. CONCLUSION: TF promoted apoptosis of nasopharyngeal carcinoma cells, the mechanism was unexpectedly involved in inducing autophagy.