Novel biological therapies such as tumor-antigen targeted vaccines (1, 2) and immune checkpoint blockade [i.e., monoclonal antibody (mAb)-based therapies targeting cytotoxic T-lymphocyte antigen 4 (CTLA-4) or programed cell death protein-1 (PD-1) (3–5)] have been designed to target specific determinants expressed by different tumor types and their associated stroma and immune compartments. The gene discussed is PDCD1; the disease is neoplasm.