Background: DNA sequence accounts for the majority of disease heritability, including cancer. However, it is becoming clear that environmentally-induced epigenetic inheritance of disease can also occur. Epidemiological studies have shown that parental exposure to the pesticide DDT and other environmental toxicants is associated with increased tumor development, particularly breast cancer, in offspring. Here, we tested whether paternal exposure to DDT could lead to intergenerational increase in breast cancer development using a mouse model. We also investigated the mechanisms of intergenerational transmission.Methods: Male mice (c57bl/6) were exposed to DDT or to a control-vehicle (CO) solution and used for sperm collection or mating with unexposed females to produce the DDT or CO daughters. In another experiment, normal mouse embryos (zygote stage) were injected with purified sperm RNAs or synthetic miRNA-10b and implanted into surrogate mothers to produce RNA-injected offspring. DDT daughters or RNA injected females were used to study breast cancer development (carcinogen-induced or orthotopic models) and metabolic parameters. Paternal sperm was used for RNA-seq analysis and miRNA expression levels. Results: Pre-conception paternal DDT exposure altered the sperm small non-coding RNA load, with an increase in miRNAs and a specific surge in miRNA-10b levels. DDT offspring weighed less at birth and at weaning, but became overweight and showed metabolic dysfunction in adulthood compared to CO. DDT daughters also showed increased mammary tumorigenesis, developing more aggressive tumors that grew faster than in CO. This tumor phenotype was linked to suppression of the AMPK energy sensing pathway and mTOR activation in mammary tissues. Remarkably, embryonic injection of purified DDT sperm RNA or synthetic miRNA-10b recapitulated the mammary gland and tumor phenotypes observed in DDT daughters. Conclusions: To our knowledge, this is the first report of an association between paternal DDT exposure and breast cancer in offspring. Paternal DDT-induced programming of breast cancer development in daughters is mechanistically linked to sperm RNAs and, more specifically, miRNA-10b. The impact of DDT and other endocrine disrupting chemicals on sperm and programming of breast and other cancers in offspring needs to be evaluated in humans.
Citation Format: Raquel Santana Da Cruz, Hong Cao, Camile C. Fontelles, Apsra Nasir, Alexandra K. Gonsiewski, M. Idalia Cruz, Lu Jin, Sonia de Assis. Environmentally-induced epigeneticinheritance of cancer: Paternal exposure to pesticides induces intergenerational programming of breast cancer predisposition via sperm small RNAs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB229.