DNA breaks in P288 tumor cells in mice after treatment with daunorubicin and adriamycin.

Extensive DNA damage was found in tumor cells after therapeutic doses of daunorubicin and adriamycin (2.5 - 10 mg/kg) were administered to mice bearing lymphocytic leukemia (P-288). After low doses (0.6 mg/kg), DNA breaks were evident as early as 1-3 hr after daunorubicin and as determined with adriamycin the damage lasted as long as 72 hr. In a comparison, actinomycin D produced smaller amounts of damage by 3 hr after the administration of maximally tolerated doses (0.8 mg/kg) and even less after 0.4 mg/kg. These experiments indicate that the antitumor activity of daunorubicin and adriamycin in treated mice may result from damage to the cellular DNA.