Development of cisplatin-resistant cell lines

Parental A549 (A549P) and H157 (H157P) cells were continuously treated with a gradually increased concentration of cisplatin for 6 months according to the method described by Barr et al.⁵⁵. Briefly, cells were treated with 1 µM cisplatin for 72 hours and allowed to recover for the following 72 hours. After repeating one more cycle at 1 µM cisplatin concentration, the cells were then treated with 2 µM cisplatin in the following two cycles. This procedure was repeated with increasing cisplatin concentrations up to 30 µM. During the cisplatin-resistance induction procedure, the IC₅₀ values of every 5 passages were determined in cisplatin-cytotoxicity tests and compared with those of the parental cells. The treatment continued until the increased IC₅₀ value remained unchanged. The cisplatin-resistant cell lines obtained by this method were maintained in growth media containing 10 µM cisplatin.