tirapazamine and thiazolyl-blue

To determine the dependency of the aerobic and hypoxic toxicity of tirapazamine on the intracellular activity of DT-diaphorase.. A panel of 18 human cell lines comprising predominantly small cell and nonsmall cell lung cancer and breast cancer lines were used. The activity of DT-diaphorase was determined in cytosolic preparations from cell lysates. The toxicity of tirapazamine was determined using the MTT assay after either 96 or 3 h aerobic exposure or 3 h treatment in hypoxia.. The cell lines exhibited a 5000-fold range in DT-diaphorase activity. In toxicity experiments, values of IC50 range from 10.2-120 microM and from 155-1230 for 96 and 3 h aerobic exposures, respectively. In N2, IC50s ranged from 8-55 microM. None of the toxicity values correlate with activity of DT-diaphorase, neither did the ratio of aerobic:hypoxic toxicity (differential toxicity).. The expression of DT-diaphorase in human tumor cells does not affect the toxicity of tirapazamine.

Topics: Antineoplastic Agents; Humans; NAD(P)H Dehydrogenase (Quinone); Radiation-Sensitizing Agents; Tetrazolium Salts; Thiazoles; Tirapazamine; Triazines; Tumor Cells, Cultured

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.

Topics: Animals; Antineoplastic Agents; Cell Line; Cell Survival; Colony-Forming Units Assay; Cricetinae; Drug Screening Assays, Antitumor; Mitomycin; Mitomycins; Oxygen; Radiation-Sensitizing Agents; Tetrazolium Salts; Thiazoles; Tirapazamine; Triazines