Leukemic Cell Proliferation as Determined by in Vitro Deoxyribonucleic Acid Synthesis*

The immature cells circulating in the blood of leukemic patients are believed to reflect the proliferative activity of the malignant tissue. The rate of DNA synthesis by these cells may provide information as to the rate of growth of leukemic cells, since the DNA synthetic period is believed to occupy a specific interval in the generation cycle of dividing cells. This report gives our findings con- cerning this parameter of leukemic proliferation, as reflected by the uptake of isotopes into leukemic cell DNA in vitro. The results indicate that the conceptualization of the acute leukemic process, as one involving rapid cell growth, must be viewed in the perspective of the total bulk of divisible cells, since the amount of DNA synthesized by acute leukemic cells is often much less than that synthesized by normal immature cells in the same time period. This implies that the generation time of acute leukemic cells is often prolonged.