Abstract LB372: Understanding the origins of the mutational landscape

Abstract Chemical carcinogens in the exposome are a significant contributor to cancer risk, yet the molecular mechanisms linking exposure to mutation and tumorigenesis are not fully resolved. A central challenge in cancer biology is defining which and how chemically-induced DNA damage is converted into stable mutational landscapes that drive malignant transformation. The long-term objective of this project is to elucidate the origins of exposure-driven mutational signatures by integrating cellular nucleic acid adductomics with long-read Nanopore sequencing and single-molecule duplex sequencing, enabling direct, molecule-level connections between DNA damage, repair, and mutation. As a foundation for this effort, we will draw on our extensive prior work using benzene exposure models. We defined the urinary nucleic acid adductome in DNA repair proficient and deficient mice following exposure to a 1:1 M cocktail of 12C6 and 13C6 - benzene, demonstrating that expected and novel chemical-specific DNA adducts can be detected and identified in vivo and that adduct burden and composition varies with sex, and DNA repair capacity. These findings underscore the limitations of conventional approaches that restrict analysis of adduct burden assessment using targeted techniques. Our study establishes both the biological relevance and technical feasibility of high-throughput stable isotope nucleic acid adductomic profiling as a tool to understand the biological impact of the exposome. Building on this framework, we initiated pilot studies examining liver carcinogens with established relevance to hepatocellular carcinoma, including trichloropropane (TCP) and furan. Male and female B6C3F1/N wild-type mice were dosed with a 1:1 ratio of isotopically labeled toxins for five consecutive days (30 mg/mL), followed by tissue collection for downstream molecular analyses. While stable isotope DNA adductomic and sequencing analyses are ongoing, early physiological endpoints indicate measurable physiological responses to exposure. Male mice exhibited mean body-weight losses of approximately 1.9% following TCP exposure and 2.8% following furan exposure, consistent with acute toxicological stress. By combining nucleic acid adductomics with next-generation long-read and duplex sequencing, this work aims to establish a platform for defining the molecular origins of carcinogen-induced mutations and advancing mechanistic understanding of exposure-driven cancer risk. Citation Format: Alexandra Keidel, Jazmine Virzi, Mina McKee, Mu-Rong Chao, Chiung-Wen Hu, Ludmil Alexandrov, Gunnar Boysen, Marcus Cooke. Understanding the origins of the mutational landscape [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(8_Suppl):Abstract nr LB372.