Abstract 3873: Understanding spatial organization of cellular plasticity in pancreatic ductal adenocarcinoma

Abstract Pancreatic ductal adenocarcinoma (PDAC) is notorious for poor survival rates, underscoring the urgency of understanding factors that drive tumor progression. A key player in this process is epithelial-mesenchymal transition (EMT), known for its role in enhancing cancer cell adaptability, resistance to treatment, and metastasis. Our study focuses on EMT within PDAC, using single-cell spatial transcriptomics to explore how the tumor microenvironment influences changes in cellular states. We introduce a novel method involving Gaussian mixture models (GMM) to categorize EMT stages in single-cell data and utilize deep learning for label transfer of these tumor cell states, including intermediate cell states, onto spatial transcriptomic data with limited gene panels and sparse count profiles. We find strong spatial autocorrelation of classical cells and a dispersion of basal cells alongside other cells at intermediate stages of the EMT spectrum. By leveraging the spatial proximity of clonally related cells, we confirm that cells transition along the EMT spectrum in a gradient and infer transition rates. We next leverage density gradients of tumor cells in different states to identify distinct neighborhoods with varying EMT subtype composition. We observe significant variations in cell density among different EMT states. A focus on cancer-associated fibroblasts (CAFs) and macrophages reveals differences in these cells across density contours. We also examine differential ligand-receptor interactions across cell state gradients to better understand the cellular interactions that drive EMT transitions and alter the tumor environment. By leveraging spatial transcriptomics, this research aims to provide new biological insights into PDAC intratumoral heterogeneity, potentially leading to the identification of novel therapeutic targets to disrupt treatment resistance. Citation Format: Izabella Zamora, Milan Parikh, Bidish K. Patel, Lynn Bi, Doron Haviv, Jingyi Cao, Carina Shiau, Martin Hemberg, William L. Hwang, Nir Hacohen, David T. Ting, Arnav Mehta. Understanding spatial organization of cellular plasticity in pancreatic ductal adenocarcinoma abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 3873.