FIG. 6.
IGF-I is required for survival of transformed macrophages. (A) J2-WT1 cells were plated (105 cells per dish) and treated for the indicated times with 10 μg of IGF-I neutralizing antibody or nonimmune IgG control/ml, in the presence or absence of M-CSF (NF, no factor). Neutral red dye uptake was used to measure cell viability at 0, 24, and 48 h after antibody treatment. The data were normalized to the number of viable cells at 0 h and are the average ± standard error of the mean of three independent experiments. (B) J2-KO1 cells (104 cells per dish) were plated in soft agar with increasing concentrations of human IGF-I. After 7 days, colonies (>50 cells) were scored. Each assay was performed in duplicate with standard errors indicated. (C) Transformed IGF-I−/− macrophages require M-CSF for survival. IGF-I−/− and IGF-I+/− bone marrow cells were infected with J2 and maintained in M-CSF for several weeks. Cells (5 × 104) were plated in soft agar in the presence or absence of M-CSF, and after 7 days colonies (>50 cells) were scored. The data are means ± standard errors of the means from two independent experiments, each performed in duplicate. Statistical significance was evaluated using Student's unpaired t test (*, P < 0.05; **, P < 0.01).