[Drug sensitivity of human acute myelocytic leukemia cells (HL-60) and normal human myelocytes (CFU-C) in a co-culture].

The chemotherapeutic susceptibility of normal human granulocyte-macrophage progenitor cells (CFU-C) and established human acute myelogenous leukemia (AML) cells (HL-60) in co-culture were determined. Nucleated marrow cells (2 X 10(5)) and HL-60 cells (5 X 10(3)) were mixed in 0.33% agar containing McCoy's 5a medium, 10% fetal calf serum, 0.1 ml of human placenta-conditioned medium and various concentrations of vincristine, cytosine arabinoside or daunorubicin to a total of 1.1 ml. They were incubated in 5% humidified CO2 at 37 degrees C for 8 to 10 days. CFU-C and HL-60 colonies were differentiated morphologically. In the absence of chemotherapeutic agents, the CFU-C colony formation was inhibited with the increasing number of HL-60 cells. CFU-C is equivalent or less sensitive than the leukemic cells in separate culture, but in co-culture it becomes more susceptible to vincristine and daunorubicin. These data indicate AML cells exert inhibitory effects on normal marrow CFU-C. In such state, normal hematopoietic cells become more susceptible to certain chemotherapeutic agents.