USP7 and hepatocellular carcinoma: Some studies have shown that USP7 is a key effector protein in the emergence of DOX chemoresistance in neuroblastoma, hepatocellular carcinoma and pancreatic cancer, and USP7 inhibition can significantly increase the chemosensitivity of tumors (Fan et al., 2013; Zhang et al., 2020a; Chen et al., 2020).