Multiplex Quantitative Analysis of Tumor-Infiltrating Lymphocytes, Cancer-Associated Fibroblasts, and CD200 in Pancreatic Cancer

SIMPLE SUMMARY: Pancreatic cancer is one of the most lethal types of cancer, and immunotherapy treatment options for these patients are limited by the characteristically “cold” tumor microenvironment. In this work, we analyze the expression levels and prognostic value of stromal tumor-infiltrating lymphocyte (CD4, CD8, and CD20) and cancer-associated fibroblast (Thy-1, FAP, and SMA) subpopulations in a cohort of pancreatic ductal adenocarcinoma patients. We additionally characterize the expression and prognostic value of CD200, a potential target for immune checkpoint blockade in these patients. CD8 and FAP were found to have prognostic significance for progression-free survival and overall survival after multivariate analysis. CD200 expression was heterogeneous in tumor and stromal cells and did not demonstrate prognostic value in this cohort. Our results point to CD8 and FAP as potential prognostic biomarkers and demonstrate the heterogeneous expression pattern of CD200 in patients with pancreatic ductal adenocarcinoma. ABSTRACT: Pancreatic cancer is marked by a desmoplastic tumor microenvironment and low tumor immunogenicity, making it difficult for immunotherapy drugs to improve outcomes for patients. Tumor-infiltrating lymphocytes (TILs) and cancer-associated fibroblasts (CAFs) are seen in the tumor microenvironment of patients with pancreatic ductal adenocarcinoma (PDAC). In this work, we sought to characterize the expression levels and potential prognostic value of TILs (CD4, CD8, and CD20) and CAFs (Thy-1, FAP, and SMA) in a large retrospective cohort of PDAC patients. Additionally, we investigated the expression levels and prognostic significance of CD200, an immunoinhibitory protein that has shown interest as a potential target for immune checkpoint blockade. We measured the expression levels of these seven proteins with multiplexed immunofluorescence staining and quantitative immunofluorescence (QIF). We found CD8 and FAP to be independent predictors of progression-free survival and overall survival. CD200 was found to be heterogeneously expressed in both the tumor and stromal compartments of PDAC, with the majority of patients having positive stromal expression and negative tumor expression. This work demonstrates the potential clinical utility of CD8 and FAP in PDAC patients, and it sheds light on the expression patterns of CD200 in pancreatic cancer as the protein is being tested as a target for immune checkpoint blockade.