L-A03, a dihydroartemisinin derivative, promotes apoptotic cell death of human breast cancer MCF-7 cells by targeting c-Jun N-terminal kinase.

L-A03 is a dihydroartemisinin derivative and exerts distinct anti-tumor activity in vitro. Previous studies showed that induction of autophagy and deficiency in nitric oxide (NO) generation contributed to apoptotic cell death in L-A03-treated MCF-7 cells. However, the detailed mechanism is still unclear. In this study, the role of mitogen-activated protein kinases (MAPKs) in this apoptotic process was investigated. L-A03 (7.5-30 µM) selectively inhibited the activation of c-Jun N-terminal protein kinase (JNK) with no significant effect on extracellular signal related kinase (ERK) and p38. In addition, the possible mechanism of interaction between JNK and L-A03 was also investigated by molecular docking. In the presence of SP600125, a specific JNK inhibitor, induction of autophagy and apoptosis with L-A03 at 15 µM were elevated, but NO generation was attenuated, indicating that JNK inactivation is essential for apoptotic cell death. Interestingly, autophagy induction and NO generation did not affect the activation of JNK, demonstrating that JNK is upstream to autophagy and NO. Taken together, L-A03-induced JNK inactivation enhances autophagic and apoptotic cell death, but represses the generation of NO. This study provides a new insight on the mechanism of L-A03-induced cell death by targeting JNK.

Timosaponin AIII induces apoptosis and autophagy in human melanoma A375-S2 cells.

Timosaponin AIII (AIII), a steroidal saponin isolated from Anemarrhena asphodeloides Bge. Our study showed that AIII induced both apoptosis and autophagy, and autophagy inhibited apoptosis in A375S2 cells. Furtherly, this study was carried out to investigate what kind of cytokines plays an important role in this process. The results revealed that AIII induced apoptosis through activating c-Jun N-terminal protein kinase (JNK) or extracellular signal related kinase (ERK) signaling pathway and generating NO. However, JNK or ERK inhibited autophagy, while NO had no effect on autophagy. Therefore, JNK, ERK or NO regulates two programmed death processes in different ways. AIII did not show obvious cytotoxic effect on human peripheral blood mononuclear cells, which indicated that AIII has less side effects on normal cells, and could be considered as a leading compound for developing novel anticancer drug.