Eldecalcitol induces apoptosis and autophagy in human osteosarcoma MG-63 cells by accumulating ROS to suppress the PI3K/Akt/mTOR signaling pathway

Eldecalcitol (ED-71) is a new type of vitamin D analog, and vitamin D has been reported to have therapeutic effects in infectious disease, autoimmune disease, and Cancer. However, the anti-cancer effect of ED-71 remains unclear. The objective of this study was to explore the anti-cancer effect of ED-71 in human osteosarcoma cells and to identify the related mechanism. The CCK8 assay results showed that ED-71 inhibited MG-63 cell viability in dose and time dependent manners. Cloning and Transwell invasion assays showed that ED-71 inhibited clonal and invasion ability of MG-63 cells. Flow cytometry results showed ED-71 the G2/M cycle arrest rate, Apoptosis, and intracellular ROS. Western blot was used to detect cleaved-caspase-3, Bax, Bcl-2, LC3-II/LC3-I, and p62 levels and the mTOR pathway. The increase of LC3-II and p62 indicated that ED-71 induced the formation of autophagosomes and inhibited Autophagy flux. Furthermore, ED-71-induced Apoptosis was weakened after adding 3-methyladenine and ED-71-induced early Autophagy was weakened by Caspase-3 inhibitor (Z-VAD-FMK), which indicated the two processes active each Other in the presence of ED-71. Furthermore, N-acetylcysteine (NAC) pretreatment reversed the ED-71-treatment outcomes, including increased Apoptosis and Autophagy and inhibition of the PI3K/Akt/mTOR pathway. In conclusion, our results reveal that ED-71 induced G2/M arrest, Apoptosis and Autophagy in MG-63 cells by accumulating ROS to suppress the PI3K/Akt/mTOR signaling pathway.