RAC1 and head and neck squamous cell carcinoma: We previously demonstrated that the EMT regulator Twist1 induces mesenchymal migration of head and neck squamous cell carcinoma (HNSCC) cells through suppression of let‐7i to activate Rac1, and that the effect could only be observed in 3D cells culture.23 We therefore speculate that EMT‐induced cellular migration is associated with the changes in biophysical and biomechanical properties in 3D environment.