M-CSF and G-CSF signaling with MEK or SHP2 inhibition in marrow progenitors. (A-B) Lineage-negative murine bone marrow (BM) cells were cultured with IL-3, IL-6, and SCF for 1 hour; removed from cytokine for 1 hour; and then cultured with no cytokine, M-CSF, or G-CSF with no inhibitor, 5 μM U0126, or 50 μM NSC-87877 for 30 minutes. Total cellular proteins were then subjected to Western blotting for indicated proteins.