Abstract A042: Cancer associated fibroblasts drive transcriptional changes in tumor cells from classical to basal phenotype and promote epithelial-to-mesenchymal transition in human pancreatic ductal adenocarcinoma
Authors: Guinn Samantha , Tandurella Joseph , Lee Jae W. , Zabransky Daniel J. , Ramani Mili , Patel Jignasha , Fertig Elana J. , Jaffee Elizabeth M. , Burkhart Richard A. , Zimmerman Jacquelyn W. 
Published: January 2024

Abstract
Introduction: Pancreatic ductal adenocarcinoma (PDAC) is a heterogeneous tumor comprised of epithelial tumor, endothelial, immune, and importantly, cancer associated fibroblasts (CAFs) cells. CAFs drive a complex tumor microenvironment (TME) through mechanisms of intratumoral interactions that are incompletely understood. It’s crucial to account for the complex role of CAFs in modern ex-vivo tumor systems as regulators of both promoting and restraining tumor growth, providing growth factor support, reprogramming immune cells, and altering the TME. Using our patient-derived organoid (PDO) and CAF coculture, we identify novel intercellular interactions between CAF and PDO that promote tumor cell proliferation, impair response to therapy, and alter transcriptional phenotype. Methods: We interrogate mechanisms of cellular crosstalk in the PDAC TME using a novel three-dimensional, patient-matched coculture of PDO and CAFs, established from patients undergoing surgical resection. Molecular characterization included bulk RNA sequencing-based transcriptomics, comprehensive proteome profiling for 107 secreted proteins with curated validation by ELISA, cellular phenotyping by multiparameter flow cytometry, and qPCR for validation of curated gene lists. Results: Bulk RNAseq of FACS sorted CAF – PDO cocultures from 12 patients demonstrate Moffitt classification transcriptional changes in 42% of samples compared to PDO monoculture, suggesting CAFs drive basal tumor phenotype. To investigate protein level changes, we compared the secreted proteome of PDOs that transitioned to a basal phenotype after coculture to PDOs that did not undergo transition. Proteome analysis from coculture supernatant revealed that HGF, GDF15, TFF3, and VEGF-A are significantly increased in samples that undergo classical to basal transition. Pathway analysis comparing transcriptional data from classical and basal PDOs identifies significant upregulation of pathways associated with epithelial-to-mesenchymal transition (EMT), inflammation, and NF-kB in basal PDOs. Further, coculture leads to decreased expression of E-cadherin and increased expression of N-cadherin on the surface of PDOs while CAF markers remain unchanged. This interaction is accompanied by an increase in PDO proliferation in coculture, suggesting that CAF presence enhances tumorgenicity and changes epithelial tumor cell fitness. Ongoing experiments will investigate tumor cell-CAF interactions spatially using matched patient tissue to complement the in vitro coculture system. Conclusions: Interactions between cancer cells and CAFs drive overall tumor biology via a complex TME and contribute to poor PDAC patient outcomes. Using our patient matched PDO - CAF coculture, we demonstrate that a CAF competent TME drives PDO plasticity towards a more basal transcriptional phenotype and enhanced EMT. We introduce an elegant approach combining in vitro coculture experiments and high dimensional assays to investigate the complex biology of the TME and inform the mechanisms driving cancer biology in individual patients with PDAC.
Citation Format: Samantha Guinn, Joseph Tandurella, Jae W. Lee, Daniel J. Zabransky, Mili Ramani, Jignasha Patel, Elana J. Fertig, Elizabeth M. Jaffee, Richard A. Burkhart, Jacquelyn W. Zimmerman. Cancer associated fibroblasts drive transcriptional changes in tumor cells from classical to basal phenotype and promote epithelial-to-mesenchymal transition in human pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr A042.