Transgenerational effects of maternal high fat diet during pregnancy on breast ca

描述（由申请人提供）：在动物模型和人类中，母亲在怀孕期间暴露于高脂肪（HF）饮食会增加雌性后代雌激素受体（ER+）和ER-乳腺癌的风险。这种影响可能不仅限于F1代的女儿：我们发现，在怀孕期间暴露于含有乙炔雌二醇（EE2）的饮食中，孙女（F2代）和曾孙女（F3代）患乳腺癌的风险也会增加。由于HF饮食增加妊娠E2水平，我们建议在小鼠中研究母体暴露于HF饮食是否会增加F1-F4代后代发生ER+和/或ER-乳腺癌的风险。此外，我们将研究这些跨代效应是否涉及DNA甲基化的变化。我们使用大规模平行测序进行的初步分析发现，与对照组相比，暴露于EE2的雌坝F1-F3代后代的乳腺中有144个“命名”基因低甲基化或高甲基化。这些基因中有21%是多梳靶基因（pcgt），其中又包括一些肿瘤抑制基因（TSGs），这表明母亲在怀孕期间的饮食，包括食用HF饮食，可能会诱导后代乳房中pctg /TSGs的甲基化。有趣的是，患乳腺癌的高风险女性表现出PcGTs和tsg的甲基化。DNA甲基化的增加可能是由DNA甲基转移酶（DNMT1， DNMT3a和DNMT3b）和多梳（EZH2, SUZ12）的上调引起的，我们和其他人已经发现这些发生在雌激素暴露的水坝的后代中。此外，dnmt和polycomb的上调可能是由雌激素诱导的针对它们的非编码mirna的抑制引发的，正如在子宫内暴露于EE2或HF饮食的MCF-7人乳腺癌细胞和大鼠的乳腺中所见（我们的初步数据）。在这项研究中，我们检验了一个假设，即母亲暴露于

DESCRIPTION (provided by applicant): Maternal exposure to a high fat (HF) diet during pregnancy increases estrogen receptor (ER+) and ER- mammary cancer risk among female offspring in animal models and in humans. The effect may not be limited to F1 generation daughters: we found that an exposure during pregnancy to a diet containing ethinyl estradiol (EE2) increased mammary cancer risk also in granddaughters (F2 generation) and great granddaughters (F3 generation). Since HF diet increases pregnancy E2 levels, we are proposing to investigate in mice whether maternal exposure to HF diet increases the risk of developing ER+ and/or ER- mammary cancer in F1-F4 generation offspring. In addition, we will investigate whether these transgenerational effects involve changes in DNA methylation. Our preliminary analysis performed using massively parallel sequencing identified 144 "named" genes which were either hypo- or hypermethylated in the mammary glands of F1-F3 generation offspring of EE2 exposed dams, compared to controls. 21% of these genes were polycomb target genes (PcGTs), which in turn included some tumor suppressor genes (TSGs), suggesting that maternal diet during pregnancy, including consumption of a HF diet, may induce methylation of PcTGs/TSGs in the offspring's breast. Interestingly, women at high risk of developing breast cancer exhibit methylation of PcGTs and TSGs. The increase in DNA methylation may be caused by up-regulation of DNA methyltransferases (DNMT1, DNMT3a and DNMT3b) and polycombs (EZH2, SUZ12), which we and others have found to occur in the offspring of estrogen exposed dams. Further, up-regulation of DNMTs and polycombs may have been initiated by estrogen-induced suppression of non-coding miRNAs which target them, as seen in MCF-7 human breast cancer cells and mammary glands of rats exposed to EE2 or HF diet in utero (our preliminary data). In this study, we test a hypothesis that maternal exposure to a HF diet during pregnancy induces a transgenerational increase in mammary cancer risk in the F1-F4 generation offspring by inducing DNA methylation of PcTGs/TSGs, via estrogen-induced down-regulation of miRNAs. A causal chain involving estrogen-induced down-regulation of miRNA, up-regulation of DNMTs and polycombs and subsequent methylation of PcGTs/TSGs, leading to increased mammary cancer in F1-F4 generation offspring, will be investigated by treating F1-F4 generation mice with histone deacetylase (HDAC) and DNMT inhibitors. Our preliminary study indicates that an exposure to HDAC+DNMT inhibitors during adult life completely reverses the increase in mammary cancer risk in in utero estrogen exposed mice, but whether these exposures reverse increased DNA methylation and increased mammary tumorigenesis in F2-F4 generations of estrogen exposed dams, is not known. Finally, as there is currently no way of knowing who might have been exposed to high in utero estrogenic environment, we will study whether these individuals can be identified by determining E2/ER regulated miRNA profile in the peripheral blood. PUBLIC HEALTH RELEVANCE: In this study, we will determine whether maternal exposure to a high fat diet during pregnancy, which elevates maternal estradiol levels, increases mammary cancer risk in F1-F4 generation mouse offspring by inducing methylation of PcGTs/TSGs. We also will determine whether increased methylation is associated with suppression of miRNAs which target DNA methyltransferases and polycombs. Finally, we will determine whether suppression of miRNAs in the peripheral RNA serves as a marker of having been exposed to elevated estrogenic environment in utero.