Loss of in vitro cytotoxicity of cisplatin after storage as stock solution in cell culture medium at various temperatures.

BACKGROUND: Cisplatin (cis-dichlorodiammineplatinum [II]) is one of the most potent and widely used cytotoxic drugs in cancer therapy. However, in vitro cytotoxicity assays often yield diverging results. Therefore, it is believed by many investigators that cisplatin is not effective in vitro. The authors investigated whether the experimental conditions used could be responsible for the diverging results.
METHODS: In vitro cytotoxicity assays were performed using the original cisplatin solution as distributed by the manufacturer or a 5-fold dilution of this in cell culture medium after storage for 2 weeks or 1 month at various temperatures (room temperature, 4 degrees C, and -20 degrees C).
RESULTS: The original solution of cisplatin retained the full cytotoxic potency for at least 1 month under all storage conditions tested. The highest loss of cytotoxicity resulted from storage of cisplatin in cell culture medium in which a >7-fold increase in the concentration that inhibits 50% occurred after 2 weeks' storage at room temperature. Solutions stored in culture medium at -20 degrees C retained full cytotoxic potency.
CONCLUSIONS: Cisplatin is a potent cytotoxic drug in vitro when stored under appropriate conditions. These findings are of relevance for in vitro studies with cisplatin.