M-CSF specifically induces P-ERK and c-Fos, whereas G-CSF specifically induces P-STAT3 and P-SHP2 in marrow progenitors. (A) Murine bone marrow (mBM) cells isolated from mice exposed to 5-FU were lineage depleted; cultured for 2 hours with IL-3, IL-6, and SCF; and subjected to FACS for MCSFR/GCSFR or Mac-1/Gr-1. (B) Lineage-negative mBM cells were cultured in media containing IL-3, IL-6, and SCF for 1 hour, removed from cytokine for 1 hour, and then cultured with no cytokine (C), M-CSF (M), or G-CSF (G) for 30 minutes. Total cellular proteins were then subjected to Western blotting. (C) Lineage-negative mBM cells cultured similarly were analyzed for P-SHP2, total SHP2, and tubulin.