Survival of mice inoculated with non-differentiating myeloid leukemia cells is prolonged by the injection of an inducer of cell differentiation with a sensitizer.

The effect of injection of an inducer and sensitizer on the survival times of syngeneic SL mice inoculated with resistant mouse myeloid leukemia cells (Ml) was examined. In vitro, the resistant Ml cells could not be induced to differentiate into mature macrophages and granulocytes by inducer (certain proteins, bacterial lipopolysaccharides, or glucocorticoids) alone, but could be induced to differentiate by treatment with both the inducer and a sensitizer (actinomycin D). In vivo, lipopolysaccharide alone scarcely affected the survival of SL mice inoculated with the resistant cells, but lipopolysaccharide plus actinomycin D significantly prolonged their survival. Administration of both lipopolysaccharide and actinomycin D also prolonged the survival of athymic nude mice inoculated with resistant Ml cells. These results suggest that prolongation of the survival of SL mice inoculated with resistant Ml cells is associated with the induction of differentiation of the cells.