As an ubiquitin E3 ligase, TRIM21 could mediate the ubiquitination and degradation of many interacting proteins, including TRPM2, IRF-8, SQSTM1/p62, Oct-1, Par-4, p21, p53, c-FLIP and BCL2, and may be involved in regulation of the inflammation, immune response, cell metabolism, redox homeostasis, and cancer [21–27]. Here, TRIM21 is linked to cancer.