Abstract 1586: An emerging role for inflammation-associated alveolar intermediate cells in early phenotypic development of KRAS-mutant lung adenocarcinoma
Authors: Sinjab Ansam , Han Guangchun , Treekitkarnmongkol Warapen , Hao Dapeng , Dai Enyu , Solis Luisa M. , Moghaddam Seyed Javad , Fujimoto Junya , Chen Jichao , Edwards Matthew , Stevenson Christopher S. , Spira Avrum E. , Wang Linghua , Kadara Humam 
Published: June 2022

Abstract
Lung adenocarcinomas (LUAD) represent the most common lung cancer subtype and frequently harbor somatic mutations in the KRAS oncogene (KM-LUADs). While enhanced screening has improved early diagnosis of KM-LUAD, patient prognosis remains moderate to poor. Decoding the earliest events driving KM-LUADs can inform of ideal targets for its interception. Previous work showed that tobacco carcinogen (NNK) exposure leads to a pervasive field of injury comprised of molecular (e.g., KRAS mutations) and inflammatory changes that are shared between LUADs and their adjacent normal-appearing ecosystem. We and others have also shown that early immune and inflammatory alterations are implicated in the progression of normal lung (NL) epithelia and premalignant lesions (PMLs) to KM-LUAD. Yet, we still do not know the identities of specific epithelial subsets or how they promote a field of injury and inspire KM-LUAD pathogenesis. Here, we performed single-cell RNA-sequencing (scRNA-seq) of lungs from a human-relevant mouse model that develops PMLs and somatic KM-LUADs following NNK exposure. Analysis of 203,991 cells including 19,513 epithelial subsets after NNK cessation and at the onset of KM-LUADs revealed a unique population of alveolar cells that closely associated with tumor inception. These cells were highly evident in NNK- but not in control saline-exposed animals. Trajectory analysis showed that tumor clones developed through these transitionary cells, henceforth referred to as alveolar intermediate cells (AICs). Notably, AICs persisted for months after NNK cessation and acquired the same driver Kras mutations found in the resultant LUADs, thus supporting a role for AICs as KM-LUAD progenitors. Intriguingly, AICs harbored elevated expression of key components of p53 signaling (Trp53, Cdkn2a) and pro-inflammatory responses (IL-1β receptor Il1r1, NF-κB), and augmented cell-cell communication with Il1b+ macrophages which were enriched in LUAD-bearing lungs. Indeed, targeting IL-1β attenuated KM-LUAD development and increased anti-tumor immunity. In parallel, murine AIC expression profiles were significantly enriched in transcriptomes of human PMLs and LUADs. We thus probed our in-house and expanding scRNA-seq cohort of enriched (by sorting) epithelial subsets from human LUADs and NL, including 191,491 alveolar cells. AICs were not only evident in human lung tissues, but their fractions were also significantly increased in LUADs relative to NL. In conclusion, we identified a unique alveolar cell state that typified KM-LUAD progenitors, associated with inflammatory cues, and progressed along the pathologic continuum of damaged epithelium to KM-LUADs. Ongoing studies are evaluating whether AICs, in concert with tumor-initiating inflammation, trigger a field of injury that may underlie early phenotypic initiation and development of KM-LUAD.
Citation Format: Ansam Sinjab, Guangchun Han, Warapen Treekitkarnmongkol, Dapeng Hao, Enyu Dai, Luisa M. Solis, Seyed Javad Moghaddam, Junya Fujimoto, Jichao Chen, Matthew Edwards, Christopher S. Stevenson, Avrum E. Spira, Linghua Wang, Humam Kadara. An emerging role for inflammation-associated alveolar intermediate cells in early phenotypic development of KRAS-mutant lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1586.