CTLA4 and breast cancer: TCR diversity of cancer tissues or peripheral blood could also be used as an indicator of prognosis of patients with various cancers (20), such as breast cancer (21), liver cancer (22), nasopharyngeal carcinoma (23), diffuse large B-cell lymphoma (24), malignant melanoma (25), etc. Some studies have suggested that targeted immunotherapy, such as CTLA-4 inhibitors, could promote the reconstruction of TCRs and increase their diversity (26).