*4.4. Colony Formation Assay*

Cell colony formation assay was performed according to the reference methods [45,48]. Firstly, cells were digested, harvested, and suspended using DMEM medium, and 400 cells/well were seeded

into 6-well cell culture plates and incubated with multifloroside (25-200 μM) or gefitinib (25 μM) for 12 days, until the cells in the control dishes had formed visible colonies. Then the colonies were washed three times with PBS and fixed with 4% paraformaldehyde for 20 min. All cells were stained with 0.2% crystal violet for 20 min. The stained colonies were counted and compared with the control samples. The medium was changed every three days.
