This design was based on a preclinical correlative study, in which researchers found that newly activated tumor-specific CD8+ T cells expressed PD-1 while upregulating IL-2Rα and that the anti-tumor effect of anti-PD-1 was dependent on the activation of PD-1+ CD25+ CD8+ T cells via autocrine IL-2/IL2-Rα signaling (205). This evidence concerns the gene PDCD1 and neoplasm.