METABOLISM AND CHEMOTHERAPEUTIC ACTIVITY OF 9-BETA-D-ARABINOFURANOSYL-2-FLUOROADENINE AGAINST MURINE LEUKEMIA-L1210 AND EVIDENCE FOR ITS PHOSPHORYLATION BY DEOXYCYTIDINE KINASE

Abstract

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 [mouse] leukemia L1210 (L1210/0) [cells]. 2-F-ara-A and 9-.beta.-D-arabinofuranosyladenine 5''-formate were inactive against 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. 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. 2-F-ara-A apparently is phosphorylated to the 5''-monophosphate by deoxycytidine kinase of leukemia L1210 cells.