In vivo development of cytosine arabinoside resistance in the BN acute myelocytic leukemia.

The in vivo development of an ara-C-resistant leukemic cell line is reported in a rat leukemia model (BNML) that is generally accepted as a relevant model for human acute myelocytic leukemia. It took 32 continuous leukemia transplant generations, performed over 20 months, and a total dose of 28.5 g ara-C/kg to induce complete resistance. Preliminary data indicate that the development of ara-C resistance is related with decreased intracellular levels of deoxycytidine kinase. Deoxycytidine deaminase levels were not increased. Thus this enzyme does not seem to be involved with induction of resistance. This preclinical rat model for human AML provides a solid basis for studies in depth on the mechanism(s) and possible prevention and effective treatment of resistance to ara-C.