RAC1 and neoplasm: Thus, the Eps8/Abi1/Sos1 tricomplex is a key regulator of αvβ6‐dependent tumour cell function, acting as a molecular switch that alters the balance between Rac1 and Rho activation, and biasing function towards a pro‐migratory (Rac1‐dependent) or pro‐TGF‐β1 activation (Rho‐dependent) phenotype, respectively.