Differentiation of myeloid cells in liquid culture: 2. Acute myelocytic leukemia cells

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Abstract
In a companion paper13 we demonstrated that normal peripheral blood granulocytic precursor cells differentiate after 2–3 weeks in suspension culture. In the studies described here leukemic blast cells obtained from 14 patients with acute myelocytic leukemia (AML) and two patients with chronic myelocytic leukemia in blastic crisis were cultured in McCoy's 5A medium containing 15 per cent fetal bovine serum for 2–3 weeks at 37°C in an atmosphere of 5 per cent CO2–95 per cent room air. ‘Spontaneous’ myeloid differentiation (20 × 104 viable mature myeloid cells ml−1) occurred in the cultures of cells obtained from 8 pts. The differentiation was granulocytic in three cases, monocytic in four cases and of mixed type in one case. Differentiation was independent of the growth of the cells in culture and occurred in four cases after the first week. Monocytic differentiation was seen only in AML of the FAB M4 type whereas granulocytic or mixed differentiation were seen only in AML of the FAB M1 or M2 types. When PHA leucocyte conditioned medium (PHA‐LCM) was added to the cultures monocytic/macrophage differentiation was favoured. Inducers of the differentiation of the HL‐60 cell line (N‐methylacetamide, cytosine arabinoside, or retinoic acid) had no consistent effect on the differentiation and were at times inhibitory. Three patients received therapy with low dose cytosine arabinoside and no correlation was observed between the outcome of the treatment and leukemic cell differentiation in culture in the presence of the drug.