IGF-I–induced migration is blocked by inhibition of the PKC and RhoA pathways. H929 cells pretreated with increasing concentrations (0.025 μM to 1 μM) of PKC inhibitors were plated on polycarbonate pore membranes (5-μM pore size) on which 2 bone marrow stromal cell lines, HS-27A (A) or HS-5 (B), were pregrown for 24 hours. (C) H929 cells pretreated with the indicated inhibitors (Figure 6B) were plated on HS-27A layered membranes as in panel A. Medium containing IGF-I and the indicated inhibitors was then added to the bottom chambers and plates were incubated for 4 hours. Cells in the lower chamber were harvested and counted following trypan blue staining. Results are shown as means ± SE (n = 3) and are representative of 3 independent experiments. * indicates P < .01; **, P < .001.