The nasopharyngeal xenograft model confirmed that the tumor volume and weight of mice injected with sh-USP21#1-transfected cells were smaller and lower than those of mice injected with sh-NC-transfected cells, indicating that knockdown of USP21 can inhibit tumor growth in vivo and USP21 can promote tumor growth in mice (Figure 5(a)). The gene discussed is USP21; the disease is neoplasm.