Glutathione as a determinant of cellular response to doxorubicin.

We have studied in detail the relationship between glutathione (GSH) depletion and sensitivity of HEp3 human carcinoma cells to doxorubicin [Adriamycin (ADR)]. Exponentially growing HEp3 cells were incubated with L-buthionine sulfoximine (BSO), an inhibitor of GSH synthesis, for different periods so that a range of GSH depletion could be obtained. These GSH-depleted cells were then treated with a combination of BSO and ADR (1 microgram/ml) for various durations. Under these conditions, the cytotoxicity of ADR was significantly enhanced by GSH depletion. The extent of ADR dose enhancement was found to be inversely proportional to cellular GSH level at the time of ADR treatment. Furthermore, it was shown that the dose-enhancement factors (DEF) also correlated with the duration of combined BSO and ADR treatment. For example, at a GSH level of 45% of untreated control, 18.5 +/- 3 fmol/cell or 4.8 +/- 0.3 X 10(-3) fmol/mum3 (+/- SD), DEF of 8.0, 6.4, and 5.0 were obtained for treatment periods of 3 hours, 2 hours, and 1 hour, respectively. Further study showed that the GSH kinetics differed significantly for the different treatment times, which indicates that GSH kinetics may be an important factor in determining the intrinsic sensitivity of HEp3 cells to ADR. Furthermore, the kinetics of GSH response to ADR varied significantly between cell lines. In the study of the effect of such differences, the GSH kinetics of 3 human ovarian tumor cell lines with different intrinsic sensitivities to ADR were investigated.(ABSTRACT TRUNCATED AT 250 WORDS)