Moreover, a reduction in CD8+ T/IFN‐γ expression (Figure 7K) and Th1/T‐bet expression was detected in the lung metastasis tissues of the mice in the 4T1Cct6a group compared with those in the 4T1EV group, whereas a rise in tumour count in the 4T1Cct6a+Trim21 mice group compared with those in the 4T1Cct6a+Trim21‐ΔRING mouse group was detected. Here, TRIM21 is linked to neoplasm.