Tumors can be classified as having or lacking a T-cell-inflamed microenvironment [168] and immunotherapeutic interventions, including checkpoint inhibitors such as antiprogrammed death 1 (PD-1), programmed death-ligand 1 (PD-L1) and anti-cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) antibodies have shown efficacy in patients with a preexisting T cell-inflamed cancer microenvironment [169]. Here, CTLA4 is linked to cancer.