The HMG-CoA/GG-PP/Rho/Rho-kinase pathway is crucial for CAM-DR. (A) Simvastatin-induced CAM-DR inhibition is mediated via GG-PP. NCI-H929 myeloma cells were grown in the presence (+HS-5) or absence (in suspension) of HS-5 cells. Simvastatin (1 μM) and melphalan (20 μM) were added for 48 hours as indicated. Only GG-OH (10 μM), not F-OH (10 μM), was able to prevent simvastatin-induced CAM-DR inhibition. (B) CAM-DR is mediated via GGTase. Cocultured NCI-H929 (NCI) and HS-5 cells were treated with 30 μM melphalan. GGTI-298 (5 μM), but not FTI-277 (2.5 μM), was able to prevent CAM-DR. (C) CAM-DR is mediated via Rho kinase activation. Cocultured NCI-H929 (NCI) and HS-5 cells were treated with 20 μM melphalan. Inhibition of Rho kinase by 20 μM Y-27632 prevents CAM-DR. (D) Inhibition of the GG-PP/Rho/Rho-kinase pathway does not induce de-adhesion. NCI-H929 (NCI) myeloma cells were grown adherent to HS-5 cells or in suspension as control. Then, 5 μM GGTI-298 or 20 μM Y-27632 was added for 48 hours. The number of viable cells in suspension was determined by the WST-1 viability assay. (E) Inhibition of the HMG-CoA/GG-PP/Rho/Rho-kinase pathway does not induce substantial integrin modulation. NCI-H929 myeloma cells were treated for 48 hours with 1 μM simvastatin, 5 μM GGTI-298, or 20 μM Y-27632. Surface expression levels of the adhesion molecules VLA-4 and LFA-1 were determined by flow cytometry. Mean values with standard deviations and P values are shown. n.s. indicates not significant.