Abstract 3933: Comprehensive molecular characterization of mitochondrial mutational landscape across the evolution of lung adenocarcinoma
Authors: Singh Alka , Dasgupta Santanu , Koppayi Ashwin L. , Rooper Lisa , Mishra Vasudha , Sidransky David , Agrawal Nishant , Suresh Karthik , Izumchenko Evgeny 
Published: March 2024

The human mitochondrial genome is prone to genetic alterations, which lead to somatic mutations, changes in mtDNA copy number and altered expression of respiratory chain subunits. This is in part due to the fact that mtDNA has a limited ability to repair itself when it is damaged. Although a buildup of somatic mutations in mtDNA has been associated with increased cancer risk, the role of mtDNA alterations in malignant transformation of lung adenocarcinoma has not been addressed. Therefore, a clear understanding of changes in mtDNA along the pathway of lung tumorigenesis is critical for identifying molecular biomarkers related to carcinogenesis and tumor progression. Like all solid tumors, lung adenocarcinoma is thought to be initiated and to progress through a series of genetic alterations, including changes in mtDNA. Lungs resected for primary adenocarcinomas often harbor minute discrete foci of cytologically atypical pneumocyte proliferations designated as atypical adenomatous hyperplasia (AAH). Evidence suggests that AAH represents an initial step in the progression to adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA) and ultimately fully invasive adenocarcinoma (ADA). In this study we used a unique cohort of 52 patients with matched specimens (n=133) representing different steps of disease progression (AAH, AIS, and MIA) coupled with novel ultra-deep mitochondrial sequencing (mtDNA-Seq) method to assess the mtDNA mutational landscape throughout the continuum of lung adenocarcinoma development. Utilizing a custom bioinformatics workflow, somatic mutations were detected in a subset of the premalignant non-invasive lesions, with overall higher mutational load observed in MIA and ACA specimens. Additionally, large degree of inter-patient heterogeneity were observed for mtDNA copy numbers in conjunction with the clonal histological evolution of pulmonary neoplasia. Moreover, an appreciable number of coding and non-coding mutations from regulatory regions of the mtDNA were detectable in the precursor AAH lesions and the continuum of LUAD progression. Majority of shared mutations showed heteroplasmic transition with increase in fractional abundance in ADA, compared to the AHH lesions, thereby indicating spatial clonal expansion as they progressed histologically. Here we report the first comprehensive characterization of mitochondrial mutational landscape in dynamic evolution of lung adenocarcinoma, and provide insight into the heterogeneity of clonal events associated with the progression from noninvasive to malignant disease.

Citation Format: Alka Singh, Santanu Dasgupta, Ashwin L. Koppayi, Lisa Rooper, Vasudha Mishra, David Sidransky, Nishant Agrawal, Karthik Suresh, Evgeny Izumchenko. Comprehensive molecular characterization of mitochondrial mutational landscape across the evolution of lung adenocarcinoma [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 3933.