Abstract 3643: Fetal exposure to diethylstilbestrol and DNA methylation in adult women.
Authors: Harlid S Sophia , Xu Zongli , Panduri Vijayalakshmi , D'Aloisio Aimee , DeRoo Lisa , Sandler Dale , Taylor Jack A. 
Published: August 2014

Abstract
In utero diethylstilbestrol (DES) exposure has long term consequences including increased risk of vaginal and breast cancer. Epigenetic factors are suspected to contribute to some of these increased risks and animal studies show DES-mediated effects on DNA methylation in both uterine tissue and blood. However, there are currently no studies examining the effect of fetal DES exposure on DNA methylation in humans. Therefore, we investigated differences in DNA methylation between women exposed to DES in utero compared to unexposed women. All our study subjects were participants in the Sister Study -a prospective cohort focused on environmental and familial risk factors for breast cancer and other diseases. Within this study 1,156 women (2.3%) said that they were definitely or probably exposed to DES in utero. In a special sub study (including both women who reported positive exposure and women who reported no exposure), we confirmed exposure history with the woman's mother and from those with matching mother daughter reports we randomly selected 100 exposed and 100 unexposed women. We analyzed DNA methylation patterns in blood using the Illumina 450k array to assess methylation at 473,844 CpG sites. Primary analysis did not reveal any differentially methylated CpGs (dmCpGs) below the false discovery rate (FDR, q&lt;0.05), nonetheless there were about 8000 dmCpGs with p-values &lt;0.05. Stratification of women into subgroups -based on menopausal status, fertility related diagnoses or hormone intake- did not alter the results. Previous work using mouse models shows gene specific changes in gene expression and DNA methylation following perinatal exposure to DES. When we compared these expression changes in ten genes to changes in promoter methylation in our data we found an inverse correlation between gene expression in mouse and the direction of methylation in our samples. This was especially evident in the ERBB2 promoter region. We also examined the subset of genes known to directly interact with DES: in four of the seven direct DES targets (AR, TTR, AFP, and GLI3) we found a majority of the 5’ CpGs had lower methylation levels in exposed women, although these differences were not statistically significant. This is the first study investigating genome wide methylation changes in women subjected to an unusual and very potent prenatal exposure that is known to have severe consequences into adulthood. Study weaknesses include lack of information regarding dose and exact timing of exposure as well as use of whole blood instead of uterine target tissue, but we still observe changes at p&lt;0.05. If DNA methylation changes are detectable in blood decades after exposure this strengthens the idea that DES exposure leads to epigenetic changes and should be possible to verify even further using samples from uterine or vaginal tissue.
Citation Format: S Sophia Harlid, Zongli Xu, Vijayalakshmi Panduri, Aimee D'Aloisio, Lisa DeRoo, Dale Sandler, Jack A. Taylor. Fetal exposure to diethylstilbestrol and DNA methylation in adult women. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3643. doi:10.1158/1538-7445.AM2013-3643