Abstract 3262: Windows of susceptibility to endocrine disruptors and gene expression in mammary tissue

Abstract

Abstract Breast cancer is hormonally driven. Endocrine disruptors (EDs) are exogenous substances that mimic or antagonize endogenous hormone action and disrupt endocrine system function. While EDs have been shown to modulate the risk for mammary tumors in animal models, their effects at biologically relevant doses and during critical developmental windows remain poorly understood. We sought to examine the individual and combinatorial effects of three common EDs, diethyl phthalate, methyl paraben and triclosan in rats exposed at five distinct developmental windows of susceptibility - prenatal, neonatal, prepubertal, pubertal and parous/nulliparous. Pathological features and whole genome expression of normal rat mammary tissues were profiled to provide both qualitative and quantitative biological effects of EDs. ED exposure at levels comparable to human exposure resulted in profound changes in both gross phenotypes (e.g. reproductive mortality and mammary gland morphology) as well as in molecular genome profiles. Specifically, ED exposure appeared to hamper normal breast development and resulted in increased mortality in the offspring, possibly due to reduced milk production. Whole genome expression profiling of mammary tissues revealed that in the course of development, the number of differentially expressed genes was lower in ED-exposed rats compared to controls, suggesting developmental delay or suppression by EDs. Pathway enrichment analysis indicated that several processes including inflammation, metabolism and development were disrupted by ED exposure. Taken together, our findings reveal novel mechanisms of ED action in mammary development and strongly suggest the importance of taking into account the timing of exposure when studying the relationship between environment and disease. Citation Format: Kalpana Gopalakrishnan, Qian Li, Yula Ma, Luca Lambertini, Jia Chen, Susan L. Teitelbaum, Fabiana Manservisi, Fiorella Belpoggi, Luciano Bua, Laura Falcioni. Windows of susceptibility to endocrine disruptors and gene expression in mammary tissue. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3262. doi:10.1158/1538-7445.AM2014-3262