Transfection of T47D breast cancer cells with constitutively active Cdc42 has been shown recently to drive migration via the Cdc42-specific effector TNK2 (formally known as Ack1), which binds to activated cdc42 but not to Rho or Rac, and subsequent activation of breast cancer antioestrogen resistance 1 (BCAR1) (formally known as p130Cas) [10,11]. Here, TNK2 is linked to breast cancer.