Likewise, the similarity in tumor antigen specificity and TCR repertoire of PD-1+CD8+ T cells in both circulating peripheral blood and TILs implies that circulating PD-1+CD8+ T lymphocytes could be a window to provide access to TSTs, and thus, PD-1 expression identified diverse patient-specific antitumor T cell responses in the peripheral blood, providing a novel non-invasive strategy for developing personalized therapies for cancer using neoantigen-reactive lymphocytes or TCR-T cells (26–28). This evidence concerns the gene PDCD1 and cancer.