[Serum deoxythymidine kinase in hematological malignancy]

A recently developed deoxythymidine kinase (TK) assay, utilizing 125I-iodo-deoxyuridine as a substrate, was used in the investigation of sera from 57 healthy persons and 46 patients with hematological malignancies. All but one sample drawn from normal adults had TK activities below 10 U/l (4.75 +/- 1.60 U/l) On the other hand, most TK activities in patient sera were remarkably elevated. Interestingly, the TK activities in non-remission and acute phase were especially high in contrast with those in remission and chronic phase. The TK activities in the supernatants derived from cultured and frozen leukemic cells were significantly higher than those in the supernatants derived from lymphocytes and spleen cells. These results suggest that the high level of TK activity in patient sera comes from malignant cells and serves as a good marker for tumor mass.