PDCD1 and neoplasm: When MIF-KO mice with YUMMER1.7 tumors were treated with anti–PD-1, 100% of the animals (n = 5 mice injected bilaterally with tumors) had rapid and complete regression of tumors by day 20 and ongoing antitumor responses after cessation of anti–PD-1 therapy and upon tumor rechallenge, which was significantly improved compared with untreated MIF-KO mice (Figure 2, F and G).