Abstract 3052: Investigating the role of FOXA1/2 & HNF4⍺ in pancreatic ductal adenocarcinoma

Abstract PDAC represents a formidable challenge with an alarmingly low 5-year survival rate of less than 12%. Integrated genomic, transcriptomic, and proteomic analyses have identified two distinct PDAC subtypes: classical and basal. The critical difference between these subtypes lies in the expression of endodermal lineage specifiers, with the classical subtype expressing FOXA1, FOXA2 (FOXA1/2), and HNF4⍺, critical for pancreatic cell-fate determination, while the basal subtype downregulates these genes, leading to the loss of endodermal identity. We reason that the transcription factors (TF), FOXA1/2 and HNF4α, that play critical roles in pancreatic development, are not only biomarkers of the classical subtype but are essential regulators of PDAC subtype differentiation state. Despite their relevance in other cancers, their specific functions in PDAC remain largely unexplored. We aim to define the functional roles of FOXA1/2 and HNF4⍺ in the classical PDAC subtype, exploring their regulation of growth and cellular identity. Previous published work in our lab has shown that exogenous HNF4⍺ restrains growth in a panel of human and murine PDAC cell lines. Furthermore, we have shown that HNF4⍺ regulates the classical subtype program of PDAC. While FOXA1/2 and HNF4⍺ cooperatively enact gene expression changes in normal tissue, the extent to which cooperative interactions between these TFs are required to activate the classical gene expression program of PDAC remains unknown. Overall, we will test the central hypothesis that FOXA1/2 and HNF4⍺ are critical regulators of the transcriptional network governing the cellular identity of classical PDAC. To test this hypothesis, we will be reconstituting and modulating the expression of these factors in human and murine PDAC cell and organoid lines. We will assess gene expression changes through RNA-seq and genomic localization of these TFs through ChIP-seq. We have conducted bulk RNA sequencing on Foxa1/2-positive and negative organoids to transcriptionally identify differences brought on by Foxa1/2 deletion and found over 2, 200 differentially expressed genes. Foxa1/2 deletion led to a significant decline in the classical PDAC signature based on gene ontology. Furthermore, we show that HNF4α can inhibit organoid growth in the absence of FOXA1/2. We discovered that HNF4⍺ targets, such as Lgals4, expression levels are unaltered at the RNA level independent of FOXA1/2. By assessing the roles of FOXA1/2 and HNF4α in PDAC, we aim to determine the transcriptional network governed by these factors in the classical subtype of PDAC Citation Format: Walter A. Orellana, Katherine Gillis, Pengshu Fang, Gabriela Fort, Eric L. Snyder. Investigating the role of FOXA1/2 Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 3052.