Single-cell RNA-seq reveals immune landscape of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) has complex tumor immune microenvironment (TIME), the clinical values of which remains to be explored. This study aimed to delineate the immune landscape of PDAC and determine the clinical value of immune features in TIME. There was a significant difference in immune profiles between PDAC and adjacent normal pancreatic tissues. Several novel immune features were captured by quantitative pathology analysis on mIHC, some of which were significantly correlated to the prognosis of PDAC patients. A risk score-based prognostic model was developed according to these immune features. We also drew a user-friendly nomogram plot to predict the overall survival of patients by combining risk score and clinicopathologic features. Both mIHC and scRNA-seq analyses showed the expression of PD-L1 was scarce in PDAC. We found that PD1+ cells were distributed in different T cell subpopulations, not enriched in a specific subpopulation. In addition, there were other conserved receptor-ligand pairs (CCL5-SDC1/4) besides PD1-PD-L1 interaction between PD1+ T cells and PD-L1+ tumor cells. Our findings reveal the immune landscape of PDAC and highlight the significant value of combined application of mIHC and scRNA-seq in uncovering TIME, which might provide new clues for developing immunotherapy strategies.