DIFFERENTIAL ACTIVITIES OF ADENOSINE-DEAMINASE ISOZYMES IN ACUTE-LEUKEMIA

ADA isozymes (ADA(1) and ADA(2)) were analyzed using an ADA inhibitor [erythro-9-(2-hydroxyl-3-nonyl) adenine,EHNA] which inhibited over 99% of ADA(1) and did not inhibit ADA(2) at all. The ratio of ADA(1) and ADA(2)(ADA(1)/ADA(2)) on acute promyelocytic leukemic cell lines (HL-6 0) which differentiated to mature blood cells by 12-0-tetradecanoyl-ph orbol-13-acetate (TPA) was repressed, while in the proliferation stage of HL-60 cells, the ratio increased. ADA(1) and ADA(2) activities of leukemic cells obtained from 33 Patients with acute myeloid leukemia ( AML), chronic myeloid leukemia (CML) and CML in blast crisis (CML-BC) and 7 normal leukocytes were determined using this inhibitor/method. T he levels ofADA(1) activity in almost all AMLs except two (cases 5 and 7, M(2) and M(3)) were higher than in normal leukocytes, but levels o f ADA(2) were almost the same as normal leukocytes in all AMLs. In the two stages of CML between chronic phase and blast crisis the ADA(1) a ctivity tended to be higher in peripheral blood mononuclear cell blast transformation than in chronic phase CML. On the other hand, ADA(2) a ctivity showed no change in these samples. Similarly, ADA(1) activity of chronic phase CML was lower than in normal leukocytes. These result s suggested that the ratio of ADA(1)/ADA(2) may represent a biochemica l marker for AML and CML-BC, together with the extent of the different iation in leukemia cells.