A spirostanol saponin isolated from Tupistra chinensis Baker simultaneously induces apoptosis and autophagy by regulating the JNK pathway in human gastric cancer cells

T-17, a bioactive spirostanol saponin extracted from Tupistra chinensis Baker, was previously reported with anti-inflammatory and cytotoxic activities. However, the mechanism underlying of its anti-proliferation activity remains to be elucidated. In this study, we investigated the anti-gastric cancer cell growth activity of T-17 in terms of cell viability, colony formation, cell cycle, induction of apoptosis/autophagy, and JNK pathway. T-17 showed dose-dependent cytotoxicity in SGC-7901 and AGS cell lines, it induced caspase-mediated apoptosis as well as G0/G1 phase arrest and modulation of cyclinE2 and p21 expression. In addition, T-17 promoted the cancer cell autophagy as evidenced with increased expression of Beclin-1 and decreased p62 in western blot and formation of GFP-LC3 puncta. Furthermore, T-17-induced autophagy decreased gastric cancer cell apoptosis as assessed by pharmacological autophagy inhibitors and ATG5 siRNA usage. Importantly, the activation of JNK pathway was simultaneously involved in T-17-induced apoptosis and autophagy. Taken together, the results suggest that T-17 is a promising cytotoxic agent for therapeutic treatment of human gastric adenocarcinoma, which provides a good foundation for further research and development of Tupistra chinensis Baker.

Keywords: JNK pathway; Tupistra chinensis Baker; apoptosis; autophagy; spirostanol saponins.