SMAD3 and neoplasm: Since RAC1B, autocrine TGFβ1, and SMAD3 all inhibited migration, and co-depletion of either RAC1B and TGFB1 or RAC1B and SMAD3 failed to provide an additional or synergistic effect over those with depletion of only one gene, we proposed the RAC1B-autocrine TGFβ-SMAD3 axis to represent a novel tumor suppressor pathway [100].