Single cell migration is a transforming growth factor-beta receptor II -dependent event. (A) Transforming growth factor-beta receptor II knockout (TβRII KO) cells used for xenografting were reconstituted with a functional human TβRII construct. Transforming growth factor-beta receptor II control (TβRIIfl/fl) cells were used as a control for active transforming growth factor beta (TGF-β) signaling as assessed by phospho-Smad2 expression. A shorter exposure of the hTβRII blot was used for all TβRII KO lanes due to overexpression signal strength. (B) Reconstitution of active TGF-β signaling in TβRII KO epithelia recapitulated the single cell migratory phenotype observed in TβRIIfl/fl tumors.