The alkaline elution procedure developed by Kohn and co-workers was used with the RPMI-6410 cultured human lymphoblastoid cell line to examine the hypothesis that anthracycline-induced DNA strand scission is mediated by oxygen- or superoxide-derived free radicals. Hypoxia was induced by gassing with nitrogen containing 5% carbon dioxide and less than 4 ppm oxygen. Alkaline elution studies showed hypoxia was induced, as the oxygen enhancement ratios for DNA strand breaks was 2.4 and 2.6 for the 250 R ± oxygen and the 500 R ± oxygen (1 R = 2.58 × 10−4 C/kg) experiments, respectively. The pattern of adriamycin-induced DNA strand breaks and cross-linking was not affected by hypoxia with 1-h adriamycin exposures between 0.05 and 1.0 μg/mL. Similarly, 1-h exposures of N-trifluoroacetyladriamycin-14-valerate at 3 or 10 μg/mL gave essentially identical alkaline elution profiles in the presence or absence of oxygen. These results do not support the hypothesis that oxygen-derived radicals play a primary role in anthracycline-induced DNA strand breakage.
Interferon production by a human lymphoblastoid cell line (DG-75) free of the Epstein-Barr genome.
