Next, we demonstrated that knocking down USP44 in thyroid cancer cells reduced p21 protein levels, while ectopic expression of wild-type USP44 but not its enzymatically inactive mutant, led to an increase in p21 protein levels, indicating that USP44 regulates p21 protein expression dependent on its deubiquitinating enzyme activity. Here, USP44 is linked to thyroid gland carcinoma.