The differential hypoxic cytotoxicity of bioreductive agents determined in vitro by the MTT assay.

We obtained good agreement between the MTT assay and conventional clonogenic assays regarding the concentration and contact time required to produce a given level of killing of Chinese hamster V79 cells treated in either air of N2 with a range of bioreductive cytotoxic drugs. All agents chosen for these experiments represented classes of compounds known to be more toxic towards hypoxic cells than they are to aerobic cells. Namely a quinone, mitomycin C; a di-N-oxide, SR4233; and a number of nitro-heterocyclics including misonidazole. The MTT assay is carried out with V79 cells attached to the bottom of 1 cm glass wells within a 24 well plate. All procedures, that is drug exposure, cell growth, metabolism of MTT are then carried out in situ. To measure optical density we used an ELIZA plate reader modified to take 24-well plates. We propose that this method provides a simple, rapid procedure for evaluating the cytotoxicity of bioreductive drugs.