Abstract PL03-02: Somatic mutations, germline risk and ancestry in lung adenocarcinoma
Authors: Meyerson Matthew L. 
Published: June 2022

Abstract
Like most cancer types, lung cancer is caused predominantly by somatic genome alterations. In lung adenocarcinoma, the most common histological type of lung cancer, these alterations are known to occur in multiple pathways including the p53 pathway, the receptor tyrosine kinase (RTK)/Ras/Raf/MAP kinase (MAPK) pathway and PI3 kinase pathway, the Rb1/cell cycle pathway, the Swi/Snf pathway, the Myc pathway, and the telomerase pathway, among others.
Genome-wide association studies comparing polymorphisms in germline DNA from patients with lung cancer and from unaffected control subjects have led to the identification of multiple germline risk alleles for lung adenocarcinoma, including the HLA locus, the telomerase catalytic subunit gene locus, and, notably, the nicotinic acetylcholine receptor locus, where polymorphisms appear to modulate individual propensity for smoking.
The components of inherited lung cancer risk, particularly in nonsmokers, are not fully understood, but there appear to be variations in lung adenocarcinoma mutations in distinct ancestry groups, which may be related to inherited factors. In particular, the frequency of somatic EGFR and KRAS mutations in lung cancer varies by ethnicity. Somatic EGFR mutation rates are higher in lung cancers from patients with East Asian ancestry and lower in lung cancers from patients with European or African ancestry. Somatic KRAS and STK11 mutation rates show the opposite pattern, higher in lung cancers from patients with European or African ancestry and lower in lung cancers from patients with East Asian ancestry. In patients from Latin America, somatic lung cancer EGFR mutation frequencies vary by country, with higher frequencies in Peru, intermediate frequencies in Mexico, Colombia, Costa Rica and Brazil, and lower frequencies in Argentina.
To explore the relationship between the somatic genome in lung cancer and ethnicity related germline risk, we performed cancer gene panel sequencing of DNA from over 1,000 lung cancers from Mexico and Colombia, countries with significant population admixture. We developed methods to infer ancestry from the tumor DNA sequence based on coverage of single nucleotide polymorphisms. This study revealed associations between ancestry and somatic lung cancer genomic alterations, including tumor mutational burden, and specific driver mutations in EGFR, KRAS, and STK11. A local ancestry score was more strongly correlated with EGFR mutation frequency compared with global ancestry correlation, suggesting that germline genetics, rather than environmental exposure, could underlie these disparities.
Our study suggests that the variation in EGFR and KRAS somatic mutation frequency in lung cancer is associated with genetic ancestry in patients from Latin America, and suggests further studies to identify germline alleles that underpin this association. If we find a germline locus or loci that could impact the development of lung cancers with EGFR and/or KRAS mutation, this might help in improving lung cancer prevention and screening for populations of Latin American origin and others. Furthermore, multiple studies now highlight the importance of EGFR mutation screening and EGFR-directed targeted therapy for lung cancer patients in Latin America and with origins in Latin America.
Citation Format: Matthew L. Meyerson. Somatic mutations, germline risk and ancestry in 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 PL03-02.