After stratifying all HCC patients from the TCGA and GSE14520 datasets into high USP21 expression group and low USP21 expression groups, Kaplan–Meier analysis indicated that those individuals whose tumors expressed the highest USP21 transcript levels had significantly poorer overall survival (OS) than those with low USP21 (TCGA P = 0.0265 and GSE14520 P = 0.0089) (Fig. 1f, g). Here, USP21 is linked to hepatocellular carcinoma.