Massive PD-L1 and CD8 double positive TILs characterize an immunosuppressive microenvironment with high mutational burden in lung cancer.

Background Programmed cell death ligand 1 (PD-L1) expressed on tumor and immune cells are both associated with the response to programmed cell death 1 (PD-1) pathway blockade therapy. Here, we examine the role of CD8+PD-L1+ tumor-infiltrating lymphocyte (Tils) in the tumor microenvironment of non-small cell lung cancer (NSCLC). Methods Tumor tissue samples of a total of 378 patients from two NSCLC cohorts were collected retrospectively. Tumor genetic variations were measured by targeted next-generation sequencing of 543 oncogenes. Tils were assessed by multiplex immunohistochemistry assay. Correlations among Tils, tumor genetic variations, and clinicopathological characteristics were analyzed. Results The levels of CD8+PD-L1+ Tils varied in NSCLC tumor tissues. Tumor samples with high CD8+PD-L1+ Tils had higher levels of CD8+ Tils, CD68+ macrophages, PD-L1+ tumor cells, PD-1+ Tils, and CD163+ M2-type macrophages, and also had a higher tumor mutation burden, all of which collectively constituted a typically hot but immunosuppressive tumor microenvironment. Therefore, in a non-immunotherapy cohort, we observed that the higher the CD8+PD-L1+ Tils level in the tumor tissue, the worse the prognosis (progression-free survival; cohort A, stage I–II tumor; p=0.005). Contrarily, in an immunotherapy cohort, where the immune suppression was blocked by anti-PD-1 treatment, the higher the CD8+PD-L1+ Tils level, the better the response to the anti-PD-1 treatment (complete response/partial response vs stable disease/progressive disease; cohort B; p=0.0337). Conclusions CD8+PD-L1+ Tils may be an indicator of the hot but immunosuppressive tumor microenvironment which is related to a high tumor mutation burden. PD-1 pathway blockade therapy can help to mitigate this immunosuppression and obtain better curative effects.