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: CNE۲ cells were used to study the anticancer effect of TF. This study used Cell Counting Kit-۸ (CCK۸) assay on proliferation and used flow cytometry to detect apoptosis. The protein expression of Bcl-۲, Bax, caspase ۳, and caspase ۹ was detected by Western blot, and autophagy-related proteins were also detected.Results: TF inhibited proliferation of CNE۲ cells, promoted apoptosis, and up-regulated the expression of caspase ۳, caspase ۹, and Bax, and decreased the level of Bcl-۲. Unexpectedly, TF induced autophagy rather than inhibiting autophagy through up-regulating the levels of the autophagy marker light chain ۳ (LC۳) and Lysosomal-associated membrane protein ۱ (LAMP۱) and reducing levels of the autophagosome cargo protein p۶۲, and the effect was via the mTOR pathway. Besides, autophagy inhibitor Chloroquine (CQ) suppressed the effect of TF on Bax, Bcl-۲ and activation of caspase ۳ and caspase ۹.Conclusion: TF promoted apoptosis of nasopharyngeal carcinoma cells, the mechanism was unexpectedly involved in inducing autophagy.

Keywords:

Apoptosis , Autophagy , Nasopharyngeal carcinoma , Proliferation , Theaflavin