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Environ Res. 2018 Feb;161:418-424. doi: 10.1016/j.envres.2017.11.040.

Lifetime exposure to ambient air pollution and methylation of tumor suppressor genes in breast tumors.

Author information

1
Department of Epidemiology and Environmental Health, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States. Electronic address: Catherine.callahan@nih.gov.
2
Department of Epidemiology and Environmental Health, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States.
3
Department of Epidemiology and Biostatistics, Texas A&M Texas A&M University, College Station, TX, United States.
4
Department of Biostatistics and Epidemiology, University of North Texas Health Science Center, Fort Worth, TX, United States.
5
Division of Cancer Prevention and Control, College of Medicine and The Ohio State University Comprehensive Cancer Center, Columbus, OH, United States.
6
Division of Cancer Prevention and Control, College of Medicine and The Ohio State University Comprehensive Cancer Center, Columbus, OH, United States; Department of Biochemistry and Pharmacology, University of Medicine an Pharmacy Timisoara, Timisoara, Romania.
7
Department of Biostatistics and Bioinformatics, Roswell Park Cancer Institute, Buffalo, NY, United States.
8
City College of New York, New York, NY, United States.
9
Consulting in the Public Interest, Lambertville, NJ, United States.

Abstract

BACKGROUND:

We previously reported increased risk of breast cancer associated with early life exposure to two measures of air pollution exposure, total suspended particulates (TSP) and traffic emissions (TE), possible proxies for exposure to polycyclic aromatic hydrocarbons (PAHs). Exposure to PAHs has been shown to be associated with aberrant patterns of DNA methylation in peripheral blood of healthy individuals. Exposure to PAHs and methylation in breast tumor tissue has received little attention. We examined the association of early life exposure to TSP and TE with patterns of DNA methylation in breast tumors.

METHODS:

We conducted a study of women enrolled in the Western New York Exposures and Breast Cancer (WEB) Study. Methylation of nine genes (SFN, SCGB3A1, RARB, GSTP1, CDKN2A CCND2, BRCA1, FHIT, and SYK) was assessed using bisulfite-based pyrosequencing. TSP exposure at each woman's home address at birth, menarche, and when she had her first child was estimated. TE exposure was modeled for each woman's residence at menarche, her first birth, and twenty and ten years prior to diagnosis. Unconditional logistic regression was employed to estimate odds ratios (OR) of having methylation greater than the median value, adjusting for age, secondhand smoke exposure before age 20, current smoking status, and estrogen receptor status.

RESULTS:

Exposure to higher TSP at a woman's first birth was associated with lower methylation of SCGB3A1 (OR = 0.48, 95% CI: 0.23-0.99) and higher methylation of SYK (OR = 1.86, 95% CI: 1.03-3.35). TE at menarche was associated with increased methylation of SYK (OR = 2.37, 95% CI: 1.05-5.33). TE at first birth and ten years prior to diagnosis was associated with decreased methylation of CCND2 (OR ten years prior to diagnosis=0.48, 95% CI: 0.26-0.89). Although these associations were nominally significant, none were significant after adjustment for multiple comparisons (p < 0.01).

CONCLUSIONS:

We observed suggestive evidence that exposure to ambient air pollution throughout life, measured as TSP and TE, may be associated with DNA methylation of some tumor suppressor genes in breast tumor tissue. Future studies with a larger sample size that assess methylation of more sites are warranted.

PMID:
29197760
PMCID:
PMC5747980
[Available on 2019-02-01]
DOI:
10.1016/j.envres.2017.11.040

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