PDCD1 and cancer: In ovarian cancer, immunotherapeutic approaches under investigation include immune checkpoint blockade (targeting programmed cell death protein 1 (PD-1), programmed death-ligand 1 (PD-L1), or cytotoxic T-lymphocyte–associated protein 4 (CTLA-4)), therapeutic cancer vaccines (CVs), adoptive cell therapies such as tumor-infiltrating lymphocytes (TILs) or chimeric antigen receptor T cells (CAR-T cells), and oncolytic viruses (9, 10).