Abstract 3997: Somatic mutational processes in the cancerization field of the normal-appearing airway reveal early drivers in the development of non-small cell lung cancer
Authors: Sivakumar Smruthy , Jakubek Yasminka , Lucas F Anthony San , Lang Wenhua , McDowell Christina , Weber Zachary , Behrens Carmen , Kalhor Neda , Moran Cesar , El-Zein Randa , Davies Gareth , Fujimoto Junya , Mehran Reza , Swisher Stephen G. , Wang Jing , Fowler Jerry , Dubinett Steven , Spira Avrum E. , Ehli Erik , Wistuba Ignacio I. , Scheet Paul , Kadara Humam 
Published: August 2018

BACKGROUND: There are very few strategies to treat non-small cell lung cancer (NSCLC) at its primitive stages largely due to our poor understanding of molecular aberrations in development of the malignancy and that would be ideal targets for early treatment. Work from our group and others revealed that visually "normal" airway cells carry alterations (e.g. expression and copy number changes) that are characteristic of the nearby lung tumor, signifying a "field of cancerization" that is pertinent to the pathobiology of the tumor. Yet, the landscape of driver alterations in the cancerization field of the normal-appearing airway remains largely unexplored.

METHODS: 409 cancer-associated genes were surveyed by deep targeted sequencing in tumor adjacent (small airways) and distant (mainstem bronchi/large airways, nasal epithelia, normal lung parenchyma) normal-appearing tissues as well as in multi-region tissues from paired tumors contrasting events in blood, for a total of 500 samples from 48 patients with early-stage NSCLC (11 squamous cell carcinomas and 37 adenocarcinomas). Somatic point mutations were interrogated by aggregating multiple mutation callers. Mutation were then paired with our recent study of genome-wide copy number alterations (CNAs) inferred from high-density whole-genome SNP microarrays.

RESULTS: We identified somatic point mutations in 76 normal-appearing field samples (75% of patients) which were overall concordant with profiles in corresponding NSCLCs. Somatic mutation signatures associated with smoking, APOBEC activity and DNA mismatch repair were common to both airway field samples and NSCLCs from smoker cases. Airway field mutation burdens, while varied, increased significantly with proximity to the tumor. Most field mutations were observed in tumor-adjacent small airways (from 31 patients) some of which were in known drivers such as TP53, KEAP1, STK11 and KRAS. Somatic mutations were also identified in more distant normal samples including large airways (TP53, SETD2, CDKN2A), normal lung parenchyma (RB1, RET) and nasal epithelium (AKT1). We then integrated point mutation and CNA data and found "two-hit" gene alteration patterns in airway field samples that were consistent with their matched NSCLCs, including point mutated gene/CNA pairs such as KEAP1 and STK11/19p loss, TP53/17p loss and KRAS/12p gain. Some additional cases exhibited single hits (e.g., TP53) in their airway field progressing to "two-hits" (e.g., TP53/17p loss) in the matched NSCLC.

CONCLUSIONS: Our integrative high-throughput sequence and genome-wide SNP analyses implicate early mutational processes and putative drivers in the progression of the mutagenized "normal" airway field of cancerization to NSCLC thus offering insights into strategies for interception via early detection and personalized prevention.

Citation Format: Smruthy Sivakumar, Yasminka Jakubek, F Anthony San Lucas, Wenhua Lang, Christina McDowell, Zachary Weber, Carmen Behrens, Neda Kalhor, Cesar Moran, Randa El-Zein, Gareth Davies, Junya Fujimoto, Reza Mehran, Stephen G. Swisher, Jing Wang, Jerry Fowler, Steven Dubinett, Avrum E. Spira, Erik Ehli, Ignacio I. Wistuba, Paul Scheet, Humam Kadara. Somatic mutational processes in the cancerization field of the normal-appearing airway reveal early drivers in the development of non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3997.