MOLECULAR-BASIS OF THE ANTINEOPLASTIC ACTIVITY OF 3'-AMINO-3'-DEOXYTHYMIDINE

Abstract

3''-Amino-3''-deoxythymidine decreased the incorporation of [2-14C]thymidine into DNA of [mouse leukemia] L1210 cells in vitro, and produced an accumulation of [2-14C]thymidine di- and triphosphate. The extent of these effects varied with the amount of recovery time after removal of 3''-amino-3''-deoxythymidine prior to addition of labeled thymidine. The distribution of radioactivity in the acid-soluble fraction derived from [3H]3''-amino-3''-deoxythymidine was as follows: 50% as 3''-amino-3''deoxythymidine, 20% as the monophosphate, 10% as the diphosphate and 20% as the triphosphate derivatives. No incorporation of [3H]3''-amino-3''deoxythymidine into L1210 DNA could be detected. 3''-Amino-3''deoxythymidine -5''triphosphate is a competitive inhibitor against dTTP [deoxy-thymidine triphosphate] with a Ki of 3.3 .mu.M, while the Km for dTTP was 8 .mu.M using activated calf thymus DNA as the template and DNA polymerase-.alpha.. Evidently, a major site of inhibition by 3''-amino-3''-deoxythymidine is inhibition of the DNA polymerase reaction.