Humoral regulation of human leukemic progenitor cell cycle: the case for turning off the cell cycle

Colony-forming cells of chronic myelocytic leukemia as well as acute nonlymphocytic leukemia in the resting state can be turned on and mobilized into cell cycle with exposure to leukocyte conditioned medium. In addition, evidence indicates that the leukemic colony-forming cells in cell cycle can be turned off and mobilized out of cell cycle by withholding the leukocyte conditioned medium. The system used in this study will be invaluable in biologic studies of leukemic cell cycling and its manipulation. With the concept of leukemic cell-cycle manipulation established, new approaches to treatment of leukemia based on growth manipulation should be explored.