Proliferation and c-

fos activation induced by G-CSF and SCF require PI3K and ERK activity. (A) MO7e-G cells were factor starved overnight, incubated with the indicated compounds, then treated for 30 minutes with SCF (100 ng/mL) and G-CSF (10 ng/mL). RNA was extracted and analyzed by semiquantitative RT-PCR with primers specific for c-fos (upper) and GAPDH (lower). (B) MO7e-G cells were factor starved for 18 hours, incubated with or without the combination of PD98059 (P) and wortmannin (W), then cultured in the presence of no growth factor, SCF (100 ng/mL), G-CSF (10 ng/mL), or both. Cell counts were obtained daily and are presented as the means and SD of 4 independent experiments.