Tanshinone IIA sensitizes oral squamous cell carcinoma to radiation due to an enhanced autophagy

Purpose: Tanshinone IIA (TanIIA), which is derived from the roots of Salvia miltiorrhiza (Danshen), has multiple pharmacological activities. However, the radiosensitivezing activity of TanIIA in oral cancer cells has not been studied extensively. The purpose of this study is to investigate the radiosensitizing effects of TanIIA in human oral squamous cell carcinoma SCC090 and examined the underlying mechanisms. Methods: Clonogenic assay was used to investigate the radiosensitizing effect of TanIIA on SCC090. And then, apoptosis and reactive oxygen species (ROS) induced by the combination of TanIIA with radiation were analyzed by Flow cytometry. Finally, autophagy was detected by monodansylcadervarine (MDC) staining. Results: TanIIA could significantly sensitize SCC090 to radiation. Meanwhile, an increase ROS generation after exposed to the combination treatment was found. In addition, the protein levels of Beclin 1, Atg5 and LC3-II, three important proteins involved in autophagy were increased in cells. Conclusions: TanIIA exerted a strong radiosensitizing effect on SCC090 comparing with the simple drug or single radiation treatment, which was due to an enhanced ROS generation and autophagy. (C) 2016 Elsevier B.V. All rights reserved.