Abstract B122: Multimodal Validation of a Plastic Transitional State in Pancreatic Ductal Adenocarcinoma

Abstract Pancreatic ductal adenocarcinoma (PDAC) is characterized by profound intratumoral heterogeneity and cellular plasticity, which drive therapeutic resistance. While molecular subtyping into classical and basal-like states has provided a framework, the biology of cells transitioning between these phenotypes remains poorly understood. This study aimed to characterize and validate a transitional, co-expressor cell state at the single-cell, spatial, and proteomic levels to elucidate mechanisms of subtype plasticity. We employed an integrative, multi-platform approach combining single-cell RNA sequencing (scRNA-seq), multiplex immunohistochemistry (mIHC), and laser microdissection with mass spectrometry-based proteomics (LMD-MS) to investigate tumor cells co-expressing the classical marker GATA6 and the basal-like marker KRT17. scRNA-seq analysis revealed that a significant population of tumor cells co-expresses GATA6 and KRT17, existing along a transcriptional continuum between the classical and basal-like poles. Pseudotime trajectory analysis identified a path from the GATA6+ classical state towards the KRT17+/GATA6+ transitional state, governed by the upregulation of pathways including MYC signaling and epithelial-mesenchymal transition (EMT). To validate these findings spatially, mIHC confirmed the presence of KRT17+/GATA6+ double-positive cells, frequently located at the interface between well-differentiated, GATA6-rich glandular structures and poorly differentiated, KRT17-rich infiltrative fronts. Furthermore, LMD-MS was used to provide proteomic confirmation. By isolating pure populations of GATA6+ and double-positive cells, we confirmed that transitional cells are enriched in proteins associated with metabolic reprogramming and cellular motility. Our findings demonstrate that PDAC plasticity is not a simple switch but a dynamic continuum involving a tangible transitional cell state. These co-expressor cells, with their unique metabolic and signaling dependencies, represent a key driver of tumor progression and a potential reservoir for therapeutic resistance. Targeting the specific vulnerabilities of this transitional phenotype offers a promising strategy to overcome plasticity, prevent relapse, and improve therapeutic outcomes in PDAC. Citation Format: Lyanne A. Delgado Coka, Jorge Villar Samaniego, Thomas Beggs, Anastasia Terbaci, Tristan Kwai, Karen Bai, Natalia Marchenko, Scott Powers, Luisa Escobar Hoyos, Kenneth Shroyer. Multimodal Validation of a Plastic Transitional State in Pancreatic Ductal Adenocarcinoma abstract. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research—Emerging Science Driving Transformative Solutions; Boston, MA; 2025 Sep 28-Oct 1; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85 (18Suppl₃): Abstract nr B122.