Metabolism and chemotherapeutic activity of 9-beta-D-arabinofuranosyl-2-fluoroadenine against murine leukemia L1210 and evidence for its phosphorylation by deoxycytidine kinase

The 2-fluoro derivative of 9-beta-D-arabinofuranosyladenine (2-F-ara-A) and its soluble 5'-formate and 5'-phosphate derivatives were therapeutically effective against the parent leukemia L1210 (L1210/0). 2-F-ara-A and 9-beta-D-arabinofuranosyladenine 5'-formate were inactive aginst a 1-beta-D-arabinofuranosylcytosine-resistant subline (L1210/ara-C) that was deficient in deoxycytidine kinase. Deoxycytidine prevented 2-F-ara-A-induced inhibition of proliferation of L1210/0 cells in culture and alleviated 2-F-ara-a inhibition of DNA synthesis. After treatment of mice with 9-beta-D-arabinofuranosyladenine 5'-formate, intracellular levels of the 5'-triphosphate of 9-beta-D-arabinofuranosylfluoroadenine in leukemia cells were more than 10 times higher in L1210/0 cells than in L1210/ara-C cells. Similar results were obtained in this line of leukemia cells from mice treated with the 5'-monophosphate of 9-beta-D-arabinofuranosyl-2-fluoroadenine. Thus, L1210/ara-C cells deficient in deoxycytidine kinase activity were also deficient in capacity to phosphorylate 2-F-ara-A. Kinase activity from L1210/0 cells for deoxycytidine and for 2-F-ara-A coeluted from calcium phosphate cellulose and from diethylaminoethyl cellulose columns and had similar mobility on gel electrophoresis. Deoxyadenosine kinase was clearly separated from deoxycytidine kinase. Deoxycytidine competed with 2-F-ara-A for phosphorylation by the partially purified enzyme from L1210 cells. These results indicate that 2-F-ara-A is phosphorylated to the 5'-monophosphate by deoxycytidine kinase of leukemia L1210 cells.