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Epigenetics. 2019 Nov;14(11):1065-1073. doi: 10.1080/15592294.2019.1631112. Epub 2019 Jun 23.

Differential DNA methylation in blood as a mediator of the association between cigarette smoking and bladder cancer risk among postmenopausal women.

Author information

1
Department of Epidemiology, School of Public Health, University of Washington , Seattle , WA , USA.
2
Program in Epidemiology, Division of Public Health Sciences, Fred Hutchinson Cancer Research Center , Seattle , WA , USA.
3
Program in Biostatistics, Division of Public Health Sciences, Fred Hutchinson Cancer Research Center , Seattle , WA , USA.
4
Department of Medicine, Vanderbilt University Medical Center , Nashville , TN , USA.
5
Departments of Epidemiology, Medicine, and Surgery, Brown University , Providence , RI , USA.
6
Cancer Prevention Program, Division of Public Health Sciences, Fred Hutchinson Cancer Research Center , Seattle , WA , USA.
7
Departments of Epidemiology and Pathology and Laboratory Medicine, Brown University , Providence , RI , USA.
8
Cancer Control Research, BC Cancer , Vancouver , BC , Canada.

Abstract

Smoking accounts for approximately 52% of bladder cancer incidence among postmenopausal women, but the underlying mechanism is poorly understood. Our study investigates whether changes in DNA methylation, as measured in blood, mediate the impact of smoking on bladder cancer risk among postmenopausal women. We conducted analyses among 206 cases and 251 controls that were current or never smokers at baseline from a previous case-control study of bladder cancer and genome-wide DNA methylation nested within the Women's Health Initiative. Separate mediation analyses were conducted for three CpG sites demonstrating robust associations with smoking in prior methylome-wide association studies: cg05575921 (AhRR), cg03636183 (F2RL3), and cg19859270 (GPR15). We estimated causal effects using the regression-based, four-way decomposition approach, which addresses the interaction between smoking and each CpG site. The overall proportion of the excess relative risk mediated by cg05575921 was 92% (p-value = 0.004) and by cg19859270 was 79% (p-value = 0.02). The largest component of the excess relative risk of bladder cancer due to 30 pack-years of smoking history in current smokers was the mediated interaction for both cg05575921 (72%, p = 0.02) and cg19859270 (72%, p-value = 0.04), where the mediated interaction is the effect of smoking on bladder cancer that both acts through differential methylation and depends on smoking history. There was little evidence that smoking was mediated through cg03636183. Our results suggest that differential methylation of cg05575921 and cg19859270 mediate the effects of smoking on bladder cancer, potentially revealing downstream effects of smoking relevant for carcinogenesis.

KEYWORDS:

Cigarette smoking; DNA methylation; F2R like thrombin or trypsin receptor 3 gene (); G protein-coupled receptor 15 gene (); aryl-hydrocarbon receptor repressor gene (); bladder cancer

PMID:
31232174
PMCID:
PMC6773399
[Available on 2020-06-23]
DOI:
10.1080/15592294.2019.1631112

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