Colony formation assays

Cells in the logarithmic growth phase were collected and made into single-cell suspensions. A total of 50 to 100 cells were seeded per well in 6-well plates. The drug was added to the corresponding group of cells and then cultured in an incubator. When the control showed visible colony formation, the culture was terminated; the culture medium was discarded and the cells were washed twice with precooled PBS. The cells were fixed with prechilled 4% paraformaldehyde for 10–15 min and then stained with crystal violet staining solution for 10–15 min. After natural drying, colony formation was observed under an inverted microscope and photographed.