TRIM21 and neoplasm: When MDA‐MB‐231EV, MDA‐MB‐231CCT6A, MDA‐MB‐231CCT6A+TRIM21 or MDA‐MB‐231CCT6A+TRIM21‐ΔRING cells were injected into nude mice, compared with MDA‐MB‐231CCT6A cells, MDA‐MB‐231CCT6A+TRIM21 cells presented significantly reduced tumour weight and tumour volume.