Proliferative state of blast cell progenitors in acute myeloblastic leukemia (AML).

Peripheral blood from patients with acute myeloblastic leukemia (AML) contains cells capable of giving rise to colonies in culture when stimulated by media conditioned by leukocytes (LCM) in the presence of phytohemagglutinin (PHA). Two types of colonies are recognized with high frequency: The first grows in the presence of low concentrations of PHA LCM, have a blast-like morphology, and are numerically correlated with morphologically identified blast cells. The second requires either high PHA LCM concentrations or PHA alone with or without 2-mercaptoethanol and consists of cells capable of forming rossettes with sheep erythrocytes and resembles. T-lymphocyte colonies from normal blood. Precursors of blast cell colonies from 15 leukemic patients were tested for cycle state, using either the 3H-thymidine or hydroxyurea techniques. All were found to have a high proportion of cells in the S phase of the cycle. In contrast, T lymphocyte precursors from three normal individual were quiescent. The data are consistent with the maintenance of the leukemic blast cell populations by the proliferative activity of a small subpopulation of blasts.