Abstract
Cancer risk may be associated with DNA methylation (DNAm) levels in Long Interspersed Nucleotide Element 1 (LINE-1), a surrogate for global DNAm. Exposure to certain pesticides may increase risk of particular cancers, perhaps mediated in part through global DNAm alterations. To date, human data on pesticide exposure and global DNAm alterations are limited. The goal of this study was to evaluate alterations of LINE-1 DNAm by pesticides in a variety of classes. Data from 596 cancer-free male participants enrolled in the Agricultural Health Study (AHS) were used to examine associations between use of 57 pesticides and LINE-1 DNAm measured via Pyrosequencing in peripheral blood leucocytes. Participants provided information on pesticide use at three contacts between 1993 and 2010. Associations of ever/never pesticide use and lifetime days of application (years of use × days per year) and LINE-1 DNAm level were assessed using linear regression, adjusting for potential confounders (race, age at blood draw, and frequency of drinking alcohol) and other moderately correlated pesticides. After adjustment, ever application of 10 pesticides was positively associated and ever application of eight pesticides was negatively associated with LINE-1 DNAm. In dose-response analyses, increases in five pesticides (imazethapyr, fenthion, EPTC, butylate, and heptachlor) were associated with increasing LINE-1 DNAm (p(trend) < 0.05) and increases in three pesticides (carbaryl, chlordane, and paraquat) were associated with decreasing LINE-1 DNAm (p(trend) < 0.05). This study provides some mechanistic insight into the pesticide-cancer relationship, which may be mediated in part by epigenetics.