CTLA4 and cancer: In recent years, immune checkpoint blockade (ICB) therapy targeting cytotoxic T lymphocyte-associated protein 4 (CTLA-4) or programmed cell death protein 1 (PD-1), and chimeric antigen receptor T cell (CAR-T) therapy utilizing genetic engineering to alter T cells to produce transmembrane proteins on the cell surface with an extracellular antibody fragment domain that recognizes tumor antigen, brings a new direction for cancer immunotherapy (4–6).