Colony formation assay

A549 and H1299 cells were trypsinized, counted, plated in a 6-well plate at a density of 100 cells/well, and incubated at 37°C for 14 days. The culture medium was changed every 2 days. The cell colony was fixed with 4% paraformaldehyde for 10 min and stained with crystal violet for 20min. Cell colonies were counted under a light microscope and photographed using a digital camera. All samples were in triplicate.