Abstract 1467: Contribution of estrogen metabolites to never-smoking lung cancer
Authors: Cheung Mitchell , Vanderveer Lisa A. , Krzizike Daniel , Bodor J. Nicholas , Treat Joseph , Testa Joseph R. , Clapper Margie L. 
Published: March 2024

There has been a consistent rise in the incidence of non-small cell lung cancer (NSCLC) among individuals who have never smoked. Remarkably, over 50% of diagnosed female cases and 15-20% of male cases are never-smokers. Notably, NSCLC in never-smokers exhibits distinctive clinical and pathological features, notably a higher incidence of tumors with EGFR mutations, setting it apart from its counterpart in smokers. Despite the improved disease-free survival observed with EGFR-tyrosine kinase inhibitors, eventual relapse and limited responsiveness to immunotherapy are common, underscoring the urgency to comprehend the molecular mechanisms driving the escalating prevalence of NSCLC in never-smokers and develop targeted preventive and interceptive therapeutic strategies. The preponderance of females among NSCLC patients who never smoked has prompted an exploration into the potential contribution of estrogen to lung tumorigenesis. In contrast to prevailing research focused on estrogen receptor-mediated signaling, our investigations have yielded compelling evidence supporting the involvement of estrogen metabolism in lung carcinogenesis among never-smokers. This group is the first to report that estrogen is metabolized extensively in both mouse and human lungs, resulting in the generation of various derivatives, including the potential carcinogen 4-hydroxyestrogen (4-OHE). Notably, recent findings from our laboratory indicate that prolonged exposure of nonneoplastic human bronchial epithelial cells to 17β estradiol or 4-OHE, at concentrations approximating physiological levels, induces the accumulation of double-strand DNA breaks and cellular transformation. A comprehensive analysis was performed to further elucidate the mechanisms underlying the transformation process. Isolated transformed clones obtained after 9, 18, and 22 wks of exposure to 4-OHE were subjected to karyotyping, F.I.S.H., and RNA and exome sequencing. A longitudinal progression of aberrant chromosomal rearrangements and copy number alterations was observed, that increased with time of 4-OHE exposure. In addition, RNA-Seq analyses revealed the epithelial-mesenchymal transition pathway was highly enriched at the early timepoint (9 wks), while replicative stress-related signaling pathways were induced at all timepoints. To determine if the differentially expressed genes were also dysregulated in clinical lung cancer cases, TCGA lung adenocarcinoma (LUAD) data were examined. Interestingly, many of the genes upregulated after estrogen exposure were similarly overexpressed in the LUAD samples and often associated with a worse prognosis. In conclusion, our data support the role of estrogen metabolites in promoting lung cancer among never-smokers. (Supported by CA217161 and generous contributions from the Hellendall Family Foundation, Gregory G. Lawton and the Timothy and Aurora Hughes Cancer Research Fund.)

Citation Format: Mitchell Cheung, Lisa A. Vanderveer, Daniel Krzizike, J. Nicholas Bodor, Joseph Treat, Joseph R. Testa, Margie L. Clapper. Contribution of estrogen metabolites to never-smoking lung cancer [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 1467.