Abstract A110: Clec4f is expressed in a subset of primary PDAC cells and confers invasive behavior
Authors: Bye Bailey A. , Walsh Richard M. , Eades Austin E. , VanSaun Michael N. 
Published: January 2024

Abstract
Pancreatic ductal adenocarcinoma (PDAC) is a particularly deadly disease with a 5-year survival rate of just 12%. Poor survival is due in part to late detection of aggressive disease coincident with distant metastases, most often in the liver. While multiple proteins have been implicated in driving PDAC metastasis, effective targeted therapeutics have yet to be developed. Therefore, understanding factors contributing to PDAC liver metastasis has significant implications for diagnosis and treatment of the disease. Evidence has emerged to suggest that a subpopulation of cells with a pre-disposition for successful seeding and outgrowth in the liver are cultivated at the primary site prior to dissemination. Investigating public datasets generated from mouse models of PDAC liver metastasis, we noted upregulation of C-type Lectin Domain Family 4 Member F (Clec4f), a galactose-binding receptor. Importantly, we also detected Clec4f expression in a subset of primary PDAC tumor epithelial cells, which established our hypothesis that Clec4f is a novel regulator of PDAC dissemination. Preliminary in vitro invasion assays demonstrate that PDAC cells engineered to overexpress Clec4f exhibit more invasive behavior compared to control cells, displaying a more mesenchymal phenotype upon confluence in 2D culture and increased invasive protrusion when grown as 3D spheroids compared to control cells. To better examine tumor-intrinsic Clec4f-expressing PDAC cells in isolation, we sorted Clec4f-expressing cells from a mouse PDAC tumor via FACS to culture in vitro. However, upon establishment in culture, the sorted cells lost Clec4f expression. Importantly, Clec4f expression in other cell types has been shown to be dependent on niche-derived TGFβ signaling, which has also been shown to regulate tumor cell invasiveness and dissemination in PDAC. This led us to probe for Clec4f-expressing tumor cells in a mouse model of PDAC lacking TGFβ receptor 2 (PKT model). In the PKT model, we observed no Clec4f-expressing tumor cells, which suggested that niche-derived TGFβ signaling is required for the upregulation of Clec4f in PDAC. Using a variety of established cellular markers, we also determined that Clec4f was co-expressed in a subset of Synaptophysin (Syp) positive enteroendocrine cells in PDAC tissue. We are currently working to determine which niche components in the tumor microenvironment provide the necessary signals to upregulate Clec4f expression in PDAC tumor cells. We expect the outcome of this study to shed light upon pro-dissemination niche dynamics in PDAC and how they contribute to the deadly process of liver metastasis.
Citation Format: Bailey A. Bye, Richard M. Walsh, Austin E. Eades, Michael N. VanSaun. Clec4f is expressed in a subset of primary PDAC cells and confers invasive behavior [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 A110.