2.12 Cisplatin sensitization by the clonogenic survival assay

HeLa cells (450 cells/well) were seeded into 6-well plates and allowed to attach overnight. Each indicated final concentration of cisplatin was added. After 24 h, compound 7 at a final concentration of 75 μM or DMSO vehicle control was added to the wells, and plates were incubated for another 24 h. The culture medium was replaced with fresh medium, and cells were cultured for another 6 days. Cells were gently rinsed twice with PBS, fixed with 3.7% formaldehyde (w/v), and stained with 0.5% crystal violet (w/v). Colonies containing more than approximately 40 cells were counted. Each treatment was performed in triplicate. The survival rate was reported as 1 for the average of colony numbers in wells that received the vehicle control of cisplatin [0.9% sodium chloride (w/v)].