T Cells Expanded from PD-1+ Peripheral Blood Lymphocytes Share More Clones with Paired Tumor-Infiltrating Lymphocytes.

Both tumor-infiltrating lymphocytes (TIL) and PD-1+ peripheral blood lymphocytes (PBL) are enriched for tumor-reactive clones recognizing known and unknown tumor antigens. However, the relationship between the T-cell receptor-β (TCRβ) repertoires of the TILs and T cells expanded from paired PD-1+ PBLs, and whether T cells expanded from PD-1+ PBLs can be used to treat patients with cancer as TIL substitutes remain unclear. Here, we established a highly efficient protocol to prepare polyclonal T cells from PD-1+ PBLs. A functional T-cell assay and tetramer staining revealed that cells from PD-1+ PBLs were relatively enriched for tumor-reactive T cells. Furthermore, deep TCRβ sequencing data revealed that an average of 11.29% (1.32%-29.06%; P = 0.015; n = 8) tumor-resident clonotypes were found in T cells expanded from paired PD-1+ PBLs, and the mean accumulated frequency of TIL clones found in T cells expanded from PD-1+ PBLs was 35.11% (7.23%-78.02%; P = 0.017; n = 8). Moreover, treatment of four patients, who failed multiline therapy and developed acquired resistance to anti-PD-1, with autologous T cells expanded from PD-1+ PBLs combined with anti-PD-1 antibody elicited objective responses from three of them. These results indicate that T cells expanded from PD-1+ PBLs share more clones with paired TILs and could be used to treat patients with cancer as TIL substitutes. SIGNIFICANCE: This study harnesses the tumor reactivity of PD-1+ PBLs, developing a method to expand T cells from these clones as a potential therapeutic strategy and TIL substitute in patients with cancer.See related commentary by Ladle, p. 1940.