MNNG/HOS and U2OS cells were seeded in 96-well plates at a concentration of 3×103 cells per hole and treated with various concentrations of Lycorine for48 h. Then 100 μl of 50 μM EdU (Cell Light EdUDNA Imaging Kit; Guangzhou RiboBio, China) was added to each well, and the cells were cultured in the medium for an additional 2 h. The cells were then stained as previously described.25 (link) Finally, the cells were observed under fluorescence microscopy and images were taken. EdU positive cells were calculated with the following formula: (EdU add-in cells/Hoechst stained cells) × 100%.26 (link)