INCORPORATION OF A POTENT ANTILEUKEMIC AGENT, 5-AZA-2'-DEOXYCYTIDINE, INTO DNA OF CELLS FROM LEUKEMIC MICE

Abstract

5-Aza-2''-deoxycytidine administered at a daily dose of 1.5 mg/kg increased the life-span of P388 leukemia-bearing BALB/c .times. DBA/2 F1 mice by 5 times and that of 2nd generation lymphoma-bearing AKR mice by 2.5 times. Higher doses (total dose, 20 mg/kg) led to favorable results when administered in 2 portions on days 4 and 5 after the s.c. inoculation of leukemic cells. The same total dose given on 5 days was toxic. The LD50 was 190 mg/kg. The drug was also effective in L1210 leukemia. 5-Aza-2''-deoxycytidine inhibited the phosphorylation of 2''-deoxycytidine in the acid soluble pool of cells from leukemic AKR mice as well as its incorporation into DNA. In vitro the inhibition of uptake of 2''-deoxycytidine into cells from leukemic mice by 5-aza-2''-deoxycytidine had a competitive character (Ki, 8 .times. 10-5 M). Although 5-aza-2''-deoxy[4-14C]cytidine of low specific activity was not detected in DNA isolated from the livers of leukemic mice, the same 3H labeled drug of high specific radioactivity was selectively localized in the nuclei of leukemic cells as revealed by autoradiography. The incorporation of [3H]-5-aza-2''-deoxycytidine into DNA of cells from leukemic mice was confirmed by the chromatographic separation of DNA on a column of Kieselguhr coated with methylated albumin.