IGF-I–stimulated proliferation of H929 cells occurs through the PI-3K/Akt pathway and does not involve PKCs or RhoA. (A) H929 cells starved for 12 hours in serum-free medium were pretreated with indicated concentrations (2.5 μM to 40 μM) of the Akt inhibitor AI and either stimulated or not stimulated with 100 ng/mL IGF-I for 10 minutes. Cell lysates were subjected to SDS-PAGE or precipitated (AP) with GST-RBD glutathione beads and then subjected to SDS-PAGE, transferred to membranes, and blotted with indicated antibodies. (B) H929 cells were grown in medium with or without IGF-I and the following inhibitors: PI-3K inhibitor LY294002 (LY, 10 μM); Akt inhibitor AI (20 μM); Rho-associated kinase inhibitor Y27632 (10 μM); MAPK inhibitor PD98059 (PD; 20 μM) p70S6 kinase inhibitor rapamycin (Rap; 10 μM); PKC inhibitor Go6983 (500 nM) and PKC inhibitor Go6976 (500 nM) for 24 and 48 hours. Cell proliferation was measured by MTT assay. Results are shown as means ± SE (n = 4) and are representative of 3 independent experiments. * indicates P < .01; **, P < .001.