Here, we tested the antitumor capacity of the combination of DNA decitabine and PD-1 inhibitor in vitro in a tumor cell and T cell coculture system and in mice bearing mouse MC38 solid tumors or EG7 lymphomas, and confirmed that DP therapy elicited superior antitumor immunity compared with anti–PD-1 single-agent. The gene discussed is PDCD1; the disease is lymphoma.