Abstract 3934: Smoking's influence on divergent paths to lung cancer
Authors: Evans Edward James , Marongiu Fabio , Lim Emilia , Pich Oriol , Zhuang Yonghua , Gao Dexiang , Hill William , Murphy Cian , Turner Ryan , Ghosh Moumita , Miller York , Jamal-Hanjani Mariam , Swanton Charles , DeGregori James 
Published: March 2024

Abstract
Lung cancer is the leading cause of cancer mortality in the world. Many studies have highlighted how mutagens from cigarette smoke promote specific mutations such as G12 mutations in KRAS, contributing to clonal evolution that leads to lung cancer. Despite the indisputable correlation between smoking and lung cancer, people who have never smoked account for the 7th leading cause of cancer mortality. Given the differences in predominant exposures, we hypothesize that the clonal evolution between people with and without smoking histories are markedly different. Therefore, we analyzed lung samples from people with different cigarette smoking exposure to elucidate smoking’s effect on the somatic mutational landscape in the progression to lung cancer. To observe somatic mutations subjected to different exposures of smoking, we used a rare-mutation detection technique called DuplexSeq to analyze somatic variants from 200+ lung samples. We acquired DNA from cells from bronchoscopy brushings and lung punches of histologically normal tissue from people with and without lung cancer and who currently, formerly, or never smoked cigarettes. Through collaborations, we characterized mutations using bioinformatic pipelines, various databases, and statistical methods. In samples from people who smoke, we observe an enhancement of mutations with higher variant allele frequencies and pervasive positive selection acting on mutations in many cancer-associated genes. From our bronchoscopy brushings, NOTCH1 mutations show the most definitive increase of protein-altering variants, while NF1 and KRAS show a predominance of driver mutation in lung punches. Unexpectedly, people without lung cancer who never smoked had a notable presence of pathogenic mutations in PTEN and PIK3CA. Furthermore, multiple punches from the same individual highlight how expansions of mutations have stronger similarity within an individual than across individuals regardless of smoking status. This association points to the importance of the inherent lung microenvironment in influencing the mutational landscapes in lung cancer progression. Altogether, these results show how smoking increases the oncogenicity of observable mutations in the lung but does not preclude the presence of oncogenic clones, emphasizing the value of precision diagnoses and prevention. Ongoing research will be centered around functional assays to determine the impact of observed mutations on tissue function and longitudinal studies using mutational landscapes as a proxy for lung cancer risk.
Citation Format: Edward James Evans, Fabio Marongiu, Emilia Lim, Oriol Pich, Yonghua Zhuang, Dexiang Gao, William Hill, Cian Murphy, Ryan Turner, Moumita Ghosh, York Miller, Mariam Jamal-Hanjani, Charles Swanton, James DeGregori. Smoking's influence on divergent paths to 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 3934.