RAC1 and osteosarcoma: These results are in agreement with the fact that Rho GDIα, a Rho guanine dissociation inhibitor that represses the activity of Rho GTPases including RhoA, Rac1 and Cdc42, has been shown to be a positive regulator of both ERα and ERβ transcriptional activities in human osteosarcoma cells [24]