Effects of antileukemic agents on the activity of terminal deoxynucleotidyl transferase from human normal thymic and leukemic cells "in vitro".

Several widely used and experimental antileukemic drugs have been tested on the activity of Terminal deoxynucleotidyl Transferase (TdT) purified from normal human thymocytes and T-derived acute lymphoblastic leukemia peripheral blood lymphoblasts. The majority of these inhibitors were equally potent inhibitors of the enzyme from thymocytes or leukemic lymphocytes. Adriamycine and etoposide were more potent inhibitors of the enzyme purified from thymocytes. Vincristine was a more potent inhibitor of TdT extracted from leukemic lymphocytes than from thymocytes. These results are discussed in terms of possible functions for TdT in the two types of cells and on the value of TdT as an indicator for clinical treatment.