ICIs can reinvigorate the anti-tumor immune response by blocking or disrupting the checkpoint protein of co-inhibitory signaling between T cells and cancer cells, such as programmed cell death (PD)-1, PD-ligand 1 (PD-L1), or cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) [1,2,3]. Here, CTLA4 is linked to cancer.