Integrin engagement by natural ligands or specific antibodies (Abs) initiates a series of intracellular signaling events that are important for regulating different cell functions, including migration, adhesion, proliferation, differentiation, apoptosis, and specific gene expression. A central role in the integrin-triggered signaling cascades is played by activation of the small GTP-binding proteins belonging to the Ras and Rho families (1 –3 ).