PRELIMINARY STUTY ON IN VITRO INCORPORATION OF BONE MARROW CELLS OF ACUTE LEUKEMIA WITH ³H-TDR

Bone marrow aspirates from patients with various types of acute leukemia were obtained before and after treatment, and in vitro incorporation of ³H-TdR with aspirated cells was studied by means of autoradiography. The degree of intracellular incorpo- ration and its variations in each case were expressed by the labeling index（LI）, i. e. the percentage of labeled cells. Marrow samples from selected non-leukemic patients served as controls. The LI_R, LI_L, and LI in 24 cases of acute leukemia before chemotherapy or in relapse were found to be lower than those observed in 21 controls. In 19 cases who responded to chemotherapy with complete remission, the averages of all 3 indices were found to be higher than those in the controls. The difference in either instance was significant. In a follow-up of 5 cases with sustained remission for 2 to 8 years, the LI values were found to be rather stable and comparable with those seen in the controls. In another 5 cases, subsequent studies showed a decrease in either LI_L or LI_R, correlating well with an impending relapse. In one of them no corresponding increase in the LI was noted while the disease was in complete remission, and a relapse soon took place. The above results suggest that in vitro ³H-TdR incorporation study may provide useful informations for acute leukemia with regard to therapy and prognosis. As the method is simple and easy to be carried out, it may be found to have practical usefulness in the future.