Morusin induces apoptosis and autophagy via JNK, ERK and PI3K/Akt signaling in human lung carcinoma cells

Due to drug resistance and side effects, the development of novel therapeutics for the treatment of lung cancer is still in an urgent need. Morusin, a naturally occurring prenylated flavonoid isolated from the root bark of Morus alba, has been reported to be a promising candidate for cancer treatment including lung cancer. This study aimed to validate the anti-cancer effects of morusin in human non-small cell lung cancer (NSCLC) cell lines A549 and NCI-H292. The results indicated that morusin had growth inhibitory, pro-apoptotic and pro-autophagic effects on A549 and NCI-H292 cells. The induction of apoptosis was characterized by chromatin condensation and PARP cleavage. Mitochondrial membrane potential (MMP) loss, cytochrome c release, Bax/Bcl-2 dysregulation, and caspase-3 cleavage were also observed, indicating a mitochondria-dependent apoptosis was induced by morusin. A pro-autophagic effect was demonstrated by the increased level of LC3-II and decreased level of SQSTM1/p62. Furthermore, morusin inhibited PI3K/Akt signaling and activated JNK, ERK pathways as indicated by the alteration in the ratio of phosphorylation level over total protein expression level. A PI3K/Akt inhibitor (LY294002), a JNK inhibitor (SP600125) and a MEK/ERK inhibitor (U0126) contributed to the determination that these pathways were involved in both apoptosis and autophagy induced by morusin. Moreover, morusin treatment strikingly enhanced intracellular ROS level, an ROS scavenger NAC blocked cell death and changes of Akt, JNK and ERK induced by morusin.