RAC1 and breast cancer: Even though Dbs was first described as an activator of RhoA and Cdc42, but not Rac1, in the activation of multiple signaling pathways using specific inhibitors (Whitehead et al., 1999; Snyder et al., 2002), a subsequent study using siRNA directed at Cdc42 and Rac1 demonstrated a role for both Cdc42 and Rac1 in activating breast cancer cell migration.