Study Evaluates Connection Between Smoking With DNA Changes Among Varying Racial and Ethnic Groups

Tobacco exposure in relation to health can differ across racial and ethnic groups, especially in relation to the link between smoking and epigenetics, which is the study of the mechanism by which gene expression is impacted. Researchers from the Keck School of Medicine of University of Southern California - Los Angeles conducted the largest multiethnic study evaluating the connection between smoking and DNA methylation of internal smoking dose between 6 racial and ethnic groups. The findings could provide scientists more knowledge on why some populations face a higher risk of lung cancer compared to others.^1,2

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Prior epidemiologic studies showed that despite self-reported smoking history, risk of lung cancer caused by smoking continued to vary based on race and ethnicity. However, researchers noted that these risks could be associated with racial and ethnic variances in the individuals use of nicotine and carcinogens from each cigarette.²

“We know that smoking affects people differently based on their race and ethnicity, but identifying epigenetic signatures of smoking would help us better predict risk for smoking-related diseases,” said Brian Huang, PhD, an assistant professor in the department of population and public health sciences at the Keck School of Medicine of USC and first author of the new study, in a press release.¹

The investigators at the Keck School of Medicine evaluated the connection between smoking with DNA methylation, which can adjust several biological occurrences. Data was included from 2728 individuals from 6 diverse racial and ethnic groups.¹

In the researcher’s primary study that used data from the Multiethnic Cohort Study (MEC), they observed that urinary total nicotine equivalents (TNEs), a calculation of nicotine uptake, displayed higher levels per cigarette among African Americans. Further, the findings showed lower levels among Japanese Americans compared to European Americans— consistent with higher and lower levels of lung cancer related to smoking among these populations. However, while the TNE uptake levels per cigarette among Native Hawaiians and Latinos were similar to European Americans, they were inconsistent with their higher and lower lung cancer risk, according to study authors.^1,2

In total, the investigators identified 408 DNA methylation markers, or CpG sites, that were connected to smoking—2 that contrasted based on race and ethnicity. Of the 408 sites, the study authors noted that 45 new sites were found in the current study. This emphasizes the importance of TNEs, as previous studies solely relied on self-reports.¹

“This gives us an indication that TNEs can provide more information beyond what we already know from self-reported measures of smoking,” Huang said in a press release.¹

Additionally, African American (site CYTH1) and Latino (site MYO1G) individuals that smoked were at a greater risk of epigenetic changes, compared to other racial and ethnic groups, according to study authors.¹

However, to provide more research, Huang and researchers gathered TNE and DNA methylation data from 340 individuals in the Singapore Chinese Health Study and 394 individuals in the Southern Community Cohort Study. The results showed various sites of the same CpG sites that were identified in the MEC study, along with sites that had a greater connection with TNEs.¹

Furthermore, Huang explained that the findings suggest that the strongest epigenetic indications of smoking remained consistent between multiple races and ethnic groups. The results can also inform scientists why certain populations face a higher risk of lung cancer; for example, there is a greater risk of lung cancer among African Americans who smoke compared to non-Hispanic Whites who smoke, vs a lower risk for Hispanic individuals who smoke.¹

Huang and researchers noted that they intend to conduct their next study to assess how epigenetic changes can increase an individual’s risk for lung cancer.¹

“By conducting these joint studies, we can understand the mechanism by which DNA methylation acts as a mediator between smoking and lung cancer, which can in turn improve our ability to predict lung cancer risk,” Huang said.¹

References

1. Large-scale study explores link between smoking and DNA changes across six racial and ethnic groups. EurekAlert!. News release. March 1, 2024. Accessed March 4, 2024. https://www.eurekalert.org/news-releases/1036321.

2. Epigenome-wide association study of total nicotine equivalents in multiethnic current smokers from three prospective cohorts. American Journal of Human Genetics. February 16, 2024. Accessed March 4, 2024. https://www.sciencedirect.com/science/article/abs/pii/S0002929724000314.