Inhibition of CFU-GM colony growth by the addition of L-739,749.

L-739,749 was a one-time addition 24 hours after establishment of the cultures, with respective concentrations of L-739,749 as indicated. Results in all cases are the mean of experiments performed in triplicate and are expressed as the percentage inhibition of maximal spontaneous CFU-GM colony growth. Error bars indicate the standard error of margin. Solid bars: Inhibition of JMML spontaneous CFU-GM colony growth. Results represent the mean of experiments performed in triplicate from 10 different patients with JMML. Hatched bars: Inhibition of GM-CSF–stimulated normal donor CFU-GM colony growth from marrow mononuclear cells obtained fresh from 5 different normal adult marrow donors. Results are expressed as the percentage inhibition of maximal CFU-GM colony growth stimulated by GM-CSF (either 2 ng/mL or 0.32 ng/mL). Diagonal bars: Inhibition of GM-CSF stimulated normal donor CFU-GM colony growth from marrow mononuclear cells that had been previously obtained from 3 different normal adult marrow donors and had been put in liquid nitrogen for long-term storage. Results are expressed as the percentage inhibition of maximal CFU-GM colony growth stimulated by GM-CSF (2 ng/mL). Open bars: Inhibition of spontaneous CFU-GM colony growth from the bone marrow mononuclear cells of an age-matched patient eventually diagnosed with thrombocytopenia with absent radii (TAR syndrome). The child did not meet the diagnostic criteria for JMML. CFU, colony-forming unit; CSF, colony-stimulating factor; GM, granulocyte macrophage; JMML, juvenile myelomonocytic leukemia.