Abstract 5633: Unravelling the pleiotropic role of HNF4α in invasive mucinous adenocarcinoma of the lung (IMA)
Authors: Dadzie Headtlove Essel , Fort Gabriela , Gillis Katherine , Fang Pengshu , Orellana Walter , Snyder Eric L. 
Published: March 2024

Abstract
IMA is a distinct subtype of lung adenocarcinoma (LUAD), marked by a cellular identity shift from a pulmonary to a gastric lineage with the loss of the pulmonary lineage specifier NKX2-1. This distinctive transformation underscores the complexity of lung cancer heterogeneity and highlights the critical role of lineage-specifying transcription factors in dictating tumor behavior. Notably, both human and murine models of IMA overexpress HNF4α, a known lineage specifier for gastric differentiation in the adult mouse mucosa. Also, concomitant deletion of Hnf4a and Nkx2-1 at tumor initiation impairs tumor growth and the extent of HNF4α in regulating IMA tumor growth, cellular identity and drug response remains unknown at large. Here, we utilized genetically engineered mouse models (GEMM) that relies on a sequential recombination strategy to delete Hnf4a in established tumors. We induce tumor formation through intratracheal delivery of Flp-O virus, activating the expression of mutant KRASG12D and Cre in lung epithelial cells. Tamoxifen administration recombines either Nkx2-1 alone (KN) or in combination with Hnf4a (KNH). We have extensively studied the phenotypic role of HNF4α in GEMM and organoids and identified gene sets regulated by HNF4α in IMA at the bulk level. To complement our findings, we profiled both the tumor and stromal compartments via scRNAseq analysis on our GEMM to gain insights into the cellular diversity within the tumor microenvironment (TME) and the role HNF4α plays. Additionally, we performed ChIPSeq in organoids to elucidate the genome occupancy of HNF4α and determine the mechanisms of gene regulation in IMA. We find that deletion of Hnf4a impairs tumor growth in GEMM and this is phenocopied in organoids. We identified numerous differentially expressed genes (DEGs) in KNH compared to KN and validated several DEGs in vivo. GSEA analysis reveals a significant involvement in regulating cellular identity and suggests a potential impact on anti-tumor immune responses. To this, our scRNAseq data revealed an enrichment of N2-TAN (tumor associated neutrophils) associated genes in KNH compared to KN, suggesting a nuanced interplay between HNF4α and the TME. Additionally, HNF4α exhibited dual functionality, acting as an activator and indirectly as a repressor by modulating the activity of other transcription factors like FOXA1. FOXA1 was found to bind de novo target genes following the loss of HNF4α. These findings so far collectively illuminate the multifaceted role of HNF4α in IMA, primarily driving tumorigenesis in a cell autonomous manner and secondarily skewing the TME towards a protumor via N2-TAN following loss of HNF4α in tumors.
Citation Format: Headtlove Essel Dadzie, Gabriela Fort, Katherine Gillis, Pengshu Fang, Walter Orellana, Eric L. Snyder. Unravelling the pleiotropic role of HNF4α in invasive mucinous adenocarcinoma of the lung (IMA) [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(6_Suppl):Abstract nr 5633.