Mechanism of action of 5-nitro-2'-deoxyuridine.

Abstract

Results are described that demonstrate that the mechanism of action of the potent cytotoxic agent 5-nitro-2'-deoxyuridine (NO2-dUrd) involves thymidine (dThd) kinase catalyzed formation of 5-nitro-2'-deoxyuridylate (NO2dUMP) and subsequent potent inhibition of thymidylate (dTMP) synthetase by this compound. The evidence for this is as follows: (a) cells lacking dThd kinase are not inhibited by high concentrations of NO2dUrd; (b) the drug has no effect on dThd or uridine (Urd) incorporation into nucleic acids but prevents incorporation of deoxyuridine (dUrd); (c) growth inhibition is reversed by dThd but not by dUrd; (d) NO2dUrd causes changes in deoxynucleoside triphosphate pool sizes which are characteristic of specific inhibition of dTMP synthetase; (e) cells treated with [3H]NO2dUrd possess macromolecular bound [3H]NO2dUMP, which has properties characteristic of the NO2dUMP-dTMP synthetase complex. Treatment of L1210 leukemic mice at 400 mg/kg daily for 6 days gave only a 33% increase in life span, probably because of its rapid degradation to the inactive nitrouracil.