Immune responses in pancreatic cancer may be restricted by prevalence of activated regulatory T-cells, dysfunctional and senescent T-cells

Abstract Objective Pancreatic cancer has the worst prognosis of any human malignancy and leukocyte infiltration is a major prognostic marker of the disease. As current immunotherapies confer negligible survival benefits, there is a need to better characterise leukocytes in pancreatic cancer to identify better therapeutic strategies. Design In this study, a multi-parameter mass-cytometry analysis was performed on 32,000 T-cells from eight human pancreatic cancer patients. Single-cell RNA sequencing dataset analysis was performed on a cohort of 24 patients. Multiplex immunohistochemistry imaging and spatial analysis were performed to map immune infiltration into the tumour microenvironment. Results Regulatory T-cell populations demonstrated highly immunosuppressive states with high TIGIT, ICOS and CD39 expression. CD8 + T-cells were found to be either in senescence or an exhausted state. The exhausted CD8 T-cells had low PD-1 expression but high TIGIT and CD39 expression. These findings were corroborated in an independent pancreatic cancer single-cell RNA dataset from 24 patients. Conclusions These data suggest that T-cells are major players in the suppressive microenvironment of pancreatic cancer. Our work identifies novel therapeutic targets that should form the basis for rational design of a new generation of clinical trials in pancreatic ductal adenocarcinoma. Statement of Significance This study elucidates the T-cell phenotypes in pancreatic ductal adenocarcinoma (PDAC). T-cells potentiate immune-suppression through an activated regulatory T-cell population expressing high TIGIT, ICOS and CD39. CD8 + T-cells were primarily senescent or TIGIT + exhausted, but with minimal PD-1 expression. These findings propose new immunotherapy targets for PDAC.