Nuclear DNA-Polymerase Estimation in Human Leukaemic Myeloblasts

Abstract

A technique which detects the presence of DNA-polymerase in cell nuclei by measuring the incorporation of 3H-TTP was used to estimate the proportion of leukemic myeloblasts which contains DNA-polymerase and DNA capable of acting as primer-template. In 6 cases of previously untreated acute myeloid leukemia, the 3H-TTP labeling index (3H-TTP LI) was much larger than the fraction in DNA synthesis. After a single flash injection of cytosine arabinoside, a pronounced decline was observed in the 3H-TTP LI, which can be explained by a direct inhibition of DNA-polymerase. No change was observed in the fraction of cells labeled with 3H-thymidine. A decrease in 3H-TTP LI was also observed after a single i.v. dose of methotrexate.