TRIM21 and neoplasm: From the results they found that the assembly polypeptide 2 (AP2) complex can deliver IgGs into tumor cells; in addition, the IgGs that entered tumor cells can recognize the targets through their Fab domains and then interact with tripartite motif‐containing 21 (TRIM21) through their Fc domains to trigger RHOC ubiquitin‐mediated degradation.