Cancer immunotherapy using anticytotoxic anti‐T‐cell antigen‐4 (CTLA4) antibodies (anti‐CTLA4) or anti‐programmed cell death‐protein1 (PD1) antibodies (anti‐PD1) have been approved for melanoma, non‐small‐cell lung cancer, and renal cell carcinoma and are also under investigation with respect to various other cancer types. Here, CTLA4 is linked to cancer.