ISOLATION AND CHARACTERIZATION OF A DEOXYCYTIDINE KINASE-DEFICIENT HUMAN PROMYELOCYTIC LEUKEMIC-CELL LINE HIGHLY RESISTANT TO 1-BETA-D-ARABINOFURANOSYLCYTOSINE

  • 1 January 1984
    • journal article
    • research article
    • Vol. 44  (11) , 5029-5037
Abstract
A deoxycytidine kinase-deficient variant of a human promyelocytic leukemic cell line (HL-60/ara-C) was isolated and characterized. These cells are capable of proliferating in the presence of 10-6 M 1-.beta.-D-arabinofuranosylcytosine (ara-C), a level achieved in the plasma of leukemic patients undergoing conventional-dose ara-C therapy. The cells share numerous biological and biochemical features with the parent line, including morphology; rate of growth; cloning characteristics; karyotype; rates of DNA, RNA and protein synthesis; and ability to undergo terminal differentiation in the presence of agents such as 12-O-tetradecanoylphorbol acetate and dimethyl sulfoxide. In contrast, these cells display a great reduction in the total intracellular accumulation of ara-C following a 4-h exposure to 10-6 M ara-C(2.4 vs. 99.0 pmol ara-C/106 cells). Resistant cells exposed to 10-6 M ara-C for 1 h also exhibited a reduction in the generation [1.2 vs. 31.9 pmol 1-.beta.-D-arabinofuranosylcytosine 5''-triphosphate (ara-CTP)/106 cells] and the 4-h retention (0.30 vs. 3.87 pmol ara-CTP/106 cells) of ara-CTP, the lethal ara-C metabolite, in comparison to parent cells. Incorporation of ara-C into resistant HL-60 cell DNA was also profoundly decreased. These biochemical alterations were associated with a 1000-fold decrease in the sensitivity of clonogenic cells to continuously administered ara-C (ara-C 50% inhibitory concentration: 1.8 .times. 10-6 M for HL-60/ara-C; 3.0 .times. 10-9 M for HL-60). A variety of antagonists of de novo pyrimidine synthesis inhibited the growth of ara-C-sensitive and -resistant cells to a similar extent. When HL-60 cells were exposed to a lethal concentration of thymidine (5 .times. 10-3 M), coadministration of 5 .times. 10-6 M deoxycytidine restored 90 .+-. 4% (SD) of colony-forming capacity. Normal human bone marrow progenitor cells were protected to a similar degree by 3 .times. 10-3 M deoxycytidine. In contrast, deoxycytidine concentrations as high as 5 .times. 10-3 M were unable to confer any protection of HL-60/ara-C cells under identical conditions. An enzymatic perturbation rendering human leukemic cells highly resistant to ara-C may be exploited to achieve a selective in vitro chemotherapeutic effect.