Clone formation assay
The clone formation experiment was used to evaluate the effect of NCTD on the cloning ability of A549 cells. A549 cells were cultured in a 6-well microplate (1000 cells / well) in 2 ml of 10% fetal calf serum and 5% CO2 humidified atmosphere at 37 ° C overnight. The cells were then treated with the prepared drug working solution NCTD on a 6-well plate for 7 days, and then stained with 0.1% crystal violet (Sigma, St. Louis, Mo, USA) for 15 minutes. A digital camera (Canon, EOS350D, Tokyo, Japan) was used to obtain images of the number of colonies.