Thermal effects on DNA synthesis in bone marrow cells of patients with acute myeloblastic leukemia

It has been known that thymidylate synthetase (TS) and thymidine kinase (TK) are DNA-synthesizing enzymes via the de novo and salvage pathways, respectively, in pyrimidine metabolism, and an immunological method using a monoclonal antibody to bromodeoxyuridine (BrdU) is useful for the detection of S-phase cells. We investigated the effects of hyperthermia on DNA synthesis in bone marrow cells obtained from patients with acute myeloblastic leukemia. TK isozymes in bone marrow cells of patients with acute myeloblastic leukemia were separated into two types, i.e.. fetal type isozyme in cytosolic cell fraction and adult type isozyme in mitochondrial cell fraction. Heating at over 43°C as a hyperthermia markedly suppressed enzyme activity of fetal type TK isozyme and number of S-phase cells labelled with BrdU, but not activities of adult type TK isozyme and TS. These results indicate that hyperthermia may regulate the proliferation of S-phase cells by the suppression of salvage synthesis of DNA.