FIG. 3.

Signaling through MEK1/2 and PI3K is required for survival of transformed macrophages. (A) J2-WT1 and J2-KO1 macrophages (∼1 × 10⁵ cells) were treated with 20 μM PD98059 (to inhibit MEK1/2) or vehicle (dimethyl sulfoxide), in the presence and absence of M-CSF (NF, no factor). Neutral red uptake was used to measure viable cells at 0, 24, and 48 h after addition of the inhibitor. The mean values and standard errors at each time point were derived from three to four independent experiments. Statistical analysis (unpaired Student's t test) showed that J2-WT1 cells treated with PD98059 had significantly reduced survival (*, P < 0.05) and that J2-KO1 cells cultured in the presence of M-CSF were unaffected by treatment with the inhibitor. (B) The same experiment was performed as in panel A, except that cells were treated with 40 μM LY294002 (to inhibit PI3K). Statistical analysis indicated that both cell lines showed a significant loss in viability upon addition of the inhibitor, with or without M-CSF treatment.