Colony forming assay

Survival ability and capability to form a new colony of single cancer cell were examined through clonogenic or colony forming assay [45]. The single cell suspension containing 250 viable cells was prepared from human lung cancer cells after treatment with 0–50 μM norcycloartocarpin for 24 h. The cells were placed onto 6-well plate and further cultured under 5% CO₂ at 37°C for 7 days. Then, forming colonies were stained with 0.05% w/v crystal violet in 4% formaldehyde for counting the colony number.