Glutathione manipulation and the radiosensitivity of human tumour and fibroblast cell lines.

We have studied the role of glutathione (GSH) in determining radiation response in five human tumour and one human fibroblast cell line. GSH concentration was measured using the Tietze assay and compared with clonogenic survival following gamma-irradiation. No relationship between GSH concentration and aerobic radiosensitivity was observed. The addition of 10 mM extracellular cysteamine produced protection factors in all cell lines, ranging from 1.6 to 2.1, but had little influence on cellular GSH concentration. Depletion of GSH by buthionine sulphoximine (0.1 mM for 18 h) had negligible effect on cell survival, though moderate radiosensitization resulted from extreme GSH depletion after 30-min treatment with 1 mM dimethylfumarate. The degree of aerobic sensitization did not correlate with GSH levels. Irradiation under hypoxia produced oxygen enhancement ratios varying from 1.6 to 2.6, with no relationship to GSH content.