Abstract 3537: Targeted deep sequencing of driver mutations in airway epithelial cells from smokers

Background: Inter-individual variation in risk for lung cancer is based on variation in both exposure to environmental factors and genetic predisposition. As such, it is reasonable to hypothesize that prevalence of mutations in the airway epithelium will vary based on the combined effects of these lung cancer risk factors. Genes most commonly mutated in non-small cell lung cancer were recently reported from The Cancer Genome Atlas (TCGA) project. The purpose of this study was to use targeted deep sequencing to assess the prevalence of these mutations in bronchial epithelial cells (BEC) of individuals at high demographic risk for lung cancer. Methods: We enrolled 19 individuals with varying demographic risk for lung cancer, who were undergoing standard-of-care bronchoscopy into an IRB-approved research study in which we collected 1-5 million BEC via bronchoscopic brush biopsy and extracted genomic DNA. 10 subjects were smokers with lung cancer, 6 subjects were smokers without lung cancer, and 3 subjects were non-smokers without lung cancer. For targeted deep sequencing, we prepared synthetic spike-in competitive internal standards for each of 12 gene loci commonly mutated in lung cancer based on TCGA results and combined them into an IS mixture (ISM). DNA aliquots from each patient were quantified and mixed with equivalent genome equivalents of ISM prior to library preparation to control for technical artifacts associated with library preparation and NGS platform-specific error. The DNA input varied depending on sample quantity; there were 5 samples with 50,000 genome copies loaded, 12 samples with 100,000 genome copies loaded, and 2 samples with 1 million genome copies loaded. This approach enabled reliable measurement of 95% confidence limits of variant allele frequency (VAF), controlled for technical sequencing error, and allowed confident call of variants at a VAF of 0.1% and lower. Libraries for specimens from each of the 19 subjects were first sequenced using the Illumina MiSeq platform to ensure equal coverage across targets and samples. Deeper sequencing was then obtained using the Illumina NextSeq platform. Results: Preliminary results showed that smokers harbored mutations up to 1.6% in gene loci associated with non-small cell lung cancer according to TCGA, while none were identified in non-smoking controls. Conclusion: Initial results suggest that airway epithelial cells in smokers acquire somatic mutations that gradually lead to malignant conversion. Deep sequencing replicate experiments are underway to expand these results. Citation Format: Daniel J. Craig, Thomas M. Blomquist, Erin L. Crawford, James C. Willey. Targeted deep sequencing of driver mutations in airway epithelial cells from smokers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3537.