Primary and metastatic cellular landscapes in human pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a complex tumor microenvironment (TME). We utilized single cell RNA sequencing to compare the TMEs of metastatic sites and primary tumors. We detected increased prevalence of exhausted CD8⁺ T cells in metastases, as well as the enrichment of complement pathway encoding genes in immunosuppressive tumor-associated macrophages, consistent with profound immunosuppression in metastatic disease. In cancer-associated fibroblasts, we identified a unique upregulation of metabolic genes, including UPP1, in metastasis. In cancer cells, we uncovered a specific gene signature upregulated in liver metastases; this signature was present in a proportion of primary tumors in the TCGA dataset, where it correlated with worse survival. Overall, our analysis of primary and metastatic PDAC defines a "high-risk" gene signature, metabolic reprogramming, and increased immune suppression in metastasis.