A batch elution method with hydroxylapatite was developed to assay DNA damage by a set of antitumor anthracycline derivatives and was standardized with respect to the kinetics of unwinding, size of the alkaline unwinding unit, and fidelity of selective elution of single and double-stranded DNA. The method was applied to a study of a set of 10 antitumor anthracycline derivatives which inhibit growth of CCRF-CEM human leukemia cells over a range of potencies exceeding four orders of magnitude. The derivatives, including Adriamycin, daunorubicin, and carminomycin, vary in structure at C-4 and C-13, with substitutions at C-14 and N and stereochemical differences at C-4′, In a static model (fixed drug concentrations and incubation times), the potency [1/ID37 (concentration of agent that inhibits cell growth by 37%)] of nine of the ten derivatives may be expressed as functions of DNA damage (n), inhibition of thymidine incorporation (l), and drug retention (r): ID37 = Ka(r/l·n)kb, with a coefficient of correlation of >0.99. A kinetic model with 4-demethoxydaunorubicin (varying concentrations and incubation times) was also described. Following initial uptake and a period of rapid loss after cells are washed free of excess drug, the change in agent concentration in the cells follows first-order kinetics. The cell index (cell number after 50 hr in drug-free growth medium/cell number after initial 2-hr exposure with drug) may be expressed linearly in terms of the kinetics of drug loss (coefficient of correlation, >0.98), or as functions of 1/n (coefficient of correlation, >0.958), 1/l·n (coefficient of correlation, >0.963), or r/l·n (coefficient of correlation, >0.963). These studies may be used to define a class of similarly acting anthracycline agents and to give some insight into the mechanism of action of the agents that fall within the class.


this investigation was supported in part by Grants CA-13039 and CA-24778, awarded by the National Cancer Institute, Department of Health, Education and Welfare. A preliminary report was presented at the National Cancer Institute-European Organization for Research on Treatment of Cancer Symposium on New Drugs in Cancer Therapy (Brussels, September 7 and 8, 1978)(35).

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