The Mechanism of Acquired Resistance to Cisplatin by a Human Ovarian Cancer Cell Line

The present study was designed to elucidate the mechanism of resistance to cisplatin. A cisplatin‐resistant cell line (KFr) was established from KF cells derived from human serous cystadenocarcinoma of the ovary. The DNA histogram revealed an increase of S‐phase cells and a decrease of G(1)‐phase cells in cultured KFr cells, compared to that in cultured KF cells. Although the cisplatin content in the KF cells incubated with cisplatin at 10 μg/ml increased in a time‐dependent manner, that in the KFr cells remained unchanged during the experimental period. When 0.5 mg of cisplatin was administered ip to nude mice with KF or KFr tumor, the cisplatin content in the KFr tumor was significantly lower than that in the KF tumor. The KFr cells showed a cross‐resistance to L‐phenylalanine mustard, while no cross‐resistance to vincristine or 5‐fluorouracil was observed. These findings suggest that the mechanism of cisplatin resistance in the KFr cells involves a decrease of cisplatin accumulation in the tumor cells.