High-fat or ethinyl-estradiol intake during pregnancy increases mammary cancer risk in several generations of offspring

Maternal exposures during pregnancy influence the risk of many chronic adult-onset diseases in the offspring. We investigated whether feeding pregnant rats a high fat (HF) or ethinyl-estradiol (EE2)-supplemented diet affects carcinogen-induced mammary cancer risk in daughters, granddaughters and great-granddaughters. Here we show that mammary tumorigenesis is higher in daughters and granddaughters of HF rat dams and in daughters, granddaughters and great-granddaughters of EE2 rat dams. Outcross experiments indicate that increased mammary cancer risk is transmitted to HF granddaughters equally through the female or male germlines, but it is only transmitted to EE2 granddaughters through the female germline. The effects of maternal EE2 exposure on offspring's mammary cancer risk are associated with alternations in the DNA methylation machinery and methylation patterns in mammary tissue of all three EE2 generations. We conclude that dietary and estrogenic exposures in pregnancy increase breast cancer risk in multiple generations of offspring, possibly through non-genetic means We examined the whole genome methylation status of both control and EE2-supplemented diet rats in three consecutive generations