DNA Map Reveals How Benzo(a)pyrene Harms Human Lung Cells

Researchers from the Swiss National Science Foundation and Philip Morris International mapped the effects of the compound benzo(a)pyrene (BaP) on DNA, down to the single-nucleotide level, in human lung cells. BaP is known to damage DNA, but it’s often identified in cigarette and industrial smoke. The study, published in the journal ACS Central Science, found a dose-dependent relationship between BaP exposure and DNA damage. Despite alterations to BaP concentrations, the pattern remained stable across the genome. Notably, the distribution of DNA damage was similar to a mutation pattern found in smoking-related lung cancers, indicating that the technique could help predict exposures that lead to cancers.

First, the researchers added the metabolized version of BaP to a culture medium with human lung cells. Then, they utilized single-nucleotide resolution DNA mapping to identify where the metabolite was attached to guanosines. The balance between damage and repair impacts whether the mutations that could cause disease carry forward when cells replicate. The study provides insight into the dynamic nature of DNA damage and repair processes, highlighting how genomic features shape the accumulation of alkylation products in the genome and predictive strategies for linking single-nucleotide resolution in vitro damage maps with human cancer mutations.

Chemical modifications to DNA bases can impact cell growth, miscode during replication, and influence disease etiology. However, knowledge of how genomic sequences and structures affect the accumulation of alkylated DNA bases has not been broadly characterized with high resolution, nor have patterns been linked with overall quantities of modified bases in the genome.

The researchers developed a single-nucleotide resolution damage sequencing method to map the main mutagenic adduct arising from BaP in a human lung cell line. They combined this analysis with quantitative mass spectrometry to evaluate the dose-response profile of adduct formation. By comparing damage with DNase hypersensitive sites, transcription levels, and other genome annotation data, the team found that although overall adduct levels rose with increasing chemical exposure concentration, genomic distribution patterns consistently correlated with chromatin state and transcriptional status.

The researchers determined preferred DNA triad sequence contexts for alkylation accumulation due to the single nucleotide resolution characteristics of this DNA damage map, revealing a characteristic DNA damage signature. This new BaP damage signature had a profile highly similar to mutational signatures identified previously in lung cancer genomes from smokers. The study provides predictive strategies for linking single-nucleotide resolution in vitro damage maps with human cancer mutations, allowing researchers to better understand how genomic features shape the accumulation of alkylation products in the genome.

This research highlights the importance of understanding the impact of potentially harmful environmental substances on human health, including their role in causing mutations that can lead to cancer. The study also showcases the potential for using single-nucleotide-resolution DNA mapping to predict genetic mutations related to human cancers, providing an avenue for earlier detection.