CDK4 and head and neck squamous cell carcinoma: While it was reported that T198 phosphorylation of cell cycle regulator p27 promotes cyclin D1–CDK4–p27 complex assembly (78), as well as increases p27-RhoA–mediated cell motility (79), HK2 silencing–mediated T198 p27 loss could be a potential underlying cue in controlling HNSCC cell growth and migration.