Abstract 6600: Investigating molecular regulators of a dual identity state in lung adenocarcinoma

Abstract Lung adenocarcinoma (LUAD) is the largest subtype of lung cancer and is the most common cause of cancer related death. LUAD progression is driven by both genetic alterations and epigenetic changes that confer increased lineage plasticity and heterogeneity, but underlying mechanisms dictating cell identity in LUAD remain incompletely understood. The lineage defining transcription factors, NKX2-1 and FoxA1/2, coordinately maintain a pulmonary identity in LUAD. Recent work suggests that NKX2-1-positive (NKX2-1+) LUAD evolves from an alveolar-like state and adopts various disparate cell fates that drive progression, including “dual-identity” states, characterized by acquisition of gastrointestinal (GI) and pulmonary-like states in the same cell. Using sophisticated genetically engineered mouse models and 3D organoid cultures, we demonstrated that the gastrointestinal transcription factor HNF4α, which robustly marks the dual-identity state, is critical for growth in NKX2-1+ LUAD. We performed bulk RNA-seq and single cell RNA-seq in vitro and in vivo, and we found that loss of HNF4α alters the differentiation state of NKX2-1+ LUAD, causing cells to shed elements of their gastric identity in favor of alternate differentiation states. Using paired chromatin immunoprecipitation sequencing and RNA-seq in dual-identity organoids, we found that HNF4α can access and activate many of its canonical gastrointestinal target genes despite being aberrantly expressed in the lung, where it is typically epigenetically silenced early in development. Surprisingly, HNF4α also colocalizes with NKX2-1 and FoxA1/2 and binds at novel sites, suggesting that HNF4α acquires expanded activity in this state beyond its canonical roles. Together, our work unveils key insights into the mechanisms by which lineage defining transcription factors regulate cellular identity and growth in LUAD. Citation Format: Gabriela Fort, Soledad Camolotto, Rushmeen Tariq, Pengshu Fang, Katherine L. Gillis, Chris Stubben, Eric L. Snyder. Investigating molecular regulators of a dual identity state in lung 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(6_Suppl):Abstract nr 6600.