High-dimensional deconstruction of pancreatic ductal adenocarcinoma identifies tumor microenvironmental communities associated with survival
Authors: Storrs Erik P. , Usmani Abul , Chati Prathamesh , Sloan Ian , Krasnick Bradley A. , Babbra Ramandeep , Harris Peter K. , Qaium Faridi , Chatterjee Deyali , Wetzel Chris , Goedegebuure S. Peter , Hollander Thomas , Anthony Hephzibah , Ponce Jennifer , Badiyan Shahed , Henke Lauren , Kim Hyun , Denardo David G. , Lang Gabriel D. , Cosgrove Natalie D. , Kushnir Vladimir M. , Early Dayna S. , Hawkins William G. , Masood Ashiq , Ding Li , Fields Ryan C. , Das Koushik K. , Chaudhuri Aadel A. 
Published: May 2022

Bulk and single-cell analyses of the pancreatic ductal adenocarcinoma (PDAC) tumor microenvironment (TME) have revealed a largely immunosuppressive milieu. Thus far, efforts to utilize insights from TME features to facilitate more effective therapeutics have largely failed. Here, we performed single-cell RNA sequencing (scRNA-seq) on a cohort of treatment-naive PDAC time-of-diagnosis endoscopic ultrasound-guided fine needle biopsy samples (n=22) and surgical samples (n=6), integrated with 3 public datasets (n=49), resulting in ∼140,000 individual cells from 77 patients. Based on expression markers assessed by Seurat v3 and differentiation status assessed by CytoTRACE, we divided the resulting tumor cellular clusters into 5 molecular subtypes based on expression of previously reported marker genes: Basal, Mixed Basal/Classical, Classical Low, Classical High, and ADEX. We then queried these 5 tumor cell profiles, along with 15 scRNA-seq-derived tumor microenvironmental cellular profiles, in 391 bulk expression samples from 4 published datasets of localized PDAC with associated clinical metadata using CIBERSORTx. Through unsupervised clustering analysis of these 20 cell state fractions representing tumor, leukocyte and stromal cells, we identified 7 unique clustering patterns representing combinations of tumor cellular and microenvironmental cell states present in PDAC tumors. We termed these cell state patterns communities, and found them to correlate with overall survival, tumor ecotypes, and tumor cellular differentiation status. The community associated with worst overall survival contained basal tumor cells, exhausted CD4 and CD8 T cells, and was enriched for fibroblasts. In contrast, the highest overall survival was associated with a community high in immune cell enrichment. The differentiation state of tumor cells (assessed by CytoTRACE) was also correlated with survival in a dose-dependent fashion. Further, we identified a subset of PDAC samples that were significantly enriched for CD8 T and plasma cells that achieved a 2-year overall survival rate of 71%, suggesting we can identify PDAC patients with significantly improved prognoses and, potentially, higher sensitivity to immunotherapy.

In summary, we identified novel tumor microenvironmental communities from high-dimensional analysis of PDAC RNA sequencing data that reveal new connections between tumor microenvironmental composition and patient survival that could lead to better upfront risk stratification and more personalized clinical decision-making.