While therapeutics that unleash the anti-tumor response by blocking inhibitory signaling pathways such as PD-1/PD-L1 have demonstrated the promise of tumor immunotherapy, immunotherapies that stimulate a specific anti-tumor response such as Sipuleucel-T, the first FDA-approved therapeutic cancer vaccine (1), have also provided a proof of concept for that approach. The gene discussed is PDCD1; the disease is neoplasm.