Effect of bisphenol A exposure on mammary stem cell function and transformation

描述(由申请人提供)：暴露于环境合成雌激素，如双酚A(BPA)，已被认为是乳腺癌发病率增加的原因之一。双酚A是现代生活中使用最广泛的化学品，是聚碳酸酯塑料和环氧树脂的一种成分，广泛用于食品和饮料容器和牙科密封剂。在啮齿类动物中，围产期暴露于低剂量的环境相关双酚A会导致癌前导管增生症、原位癌的诱导，并增加肿瘤发生的易感性。然而，这些观察到的潜在机制尚不清楚。小鼠乳腺干细胞(MASCs)具有促进青春期乳腺发育、孕期生长和重塑的潜能。最近的血统追踪研究也表明，在小鼠乳腺中存在干细胞的层次结构。值得注意的是，这些独特的一元性基底和管腔MASCs通过其特定的基因表达特征与不同的乳腺癌亚型相匹配。此外，癌基因和抑癌基因的调控可增加MASCs的干细胞区划和自我更新功能，提示MASC频率和功能的改变可能导致转化和肿瘤的发生。未发表的结果表明，青春期低剂量的BPA暴露可以改变不同谱系的MASCs的数量。最近的动物研究表明，BPA还通过雌激素信号促进肿瘤细胞的生长，BPA在整个生命周期的不同时间点暴露于BPA，可能导致乳腺癌的发生和发展。因此，推测乳腺在敏感窗口暴露于BPA可能通过MASC和/或干细胞生态位介导的机制导致其对肿瘤的易感性。除了小鼠，目的也是用普通的绒猴来确定BPA对其MASC功能和转化的影响，因为非人类灵长类动物与人类有着密切的系统发育关系，可以更好地模拟生理和病理因素对人类的影响。这一假设将通过三个具体目标进行检验。首先， 双酚A对非灵长类和灵长类受试者MASC功能的影响将被确定。本实验室开发的一种新的体外试验将被开发，以取代细胞表面标记 不是MASCs所特有的，用来量化系统BPA治疗后小鼠和恒河猴乳腺不同发育窗中MASC数量的变化。其次，将完成低剂量辐射对暴露于BPA的小鼠来源的MASCs转化潜力的影响的测定。为了这个特定的目的，需要检验的假设是，双酚A的转化活性可能与DNA损伤剂(如电离辐射)结合在一起更加明显，而电离辐射是乳腺癌的已知风险因素。第三，BPA治疗对肥胖小鼠和绒猴MASC功能的影响。这项研究不仅将回答BPA诱导的乳腺不同发育窗口的形态发生变化是否有干细胞起源的问题，而且还将揭示MASC对异种雌激素、辐射和肥胖等多种危险因素诱导的细胞转化的易感性，这将对人类乳腺癌的疾病预防具有重要意义。

DESCRIPTION (provided by applicant): Exposure to environmental synthetic estrogens, such as bisphenol A (BPA), has been implicated to contribute to the increasing incidence of breast cancer. Bisphenol A is a most pervasive chemical in modern life as a component of polycarbonate plastics and epoxy resins used widely for food and beverage containers and dental sealants. Perinatal exposure to low, environmentally relevant doses of BPA in rodents resulted in induction of preneoplastic ductal hyperplasias, carcinoma in situ, and increased susceptibility to tumorigenesis. However, the underlying mechanism for these observations is unclear. The murine mammary stem cells (MaSCs) have the potential to drive mammary gland development during puberty, and growth and remodeling during pregnancy. Recent lineage tracing studies also indicated the presence of a hierarchy of stem cells in the murine mammary gland. Significantly, these distinct unipotent basal and luminal MaSCs have been matched with different subtypes of breast cancer by their specific gene-expression signatures. Furthermore, modulation of oncogenes and tumor suppressors has been shown to increase stem cell compartment and self-renewal function of MaSCs, suggesting that alteration of MaSC frequency and function may lead to transformation and tumorigenesis. Unpublished results indicate that low dose BPA exposure during puberty can alter the number of different lineage MaSCs. Recent animal studies showed that BPA also promoted tumor cell growth through estrogenic signaling implicating the risk of development and progression of mammary cancer by BPA exposure at various time points throughout the lifespan. Thus it is hypothesized that mammary gland exposed to BPA at a susceptible window may lead to its susceptibility to tumorigenesis through a MaSC and/or stem cell niche mediated mechanism. In addition to mice, the intent is to also use common marmoset to determine the effect of BPA on its MaSC function and transformation because nonhuman primates, with their close phylogenetic relationship to humans, can better simulate the effects of physiological and pathological factors on humans. This hypothesis will be tested with three specific aims. First, the effect of BPA will be determined on MaSC function of non-primate and primate subjects. A novel in vitro assay developed in this laboratory will be exploited, instead of cell surface markers that are not specific for MaSCs, to quantify the alteration of basal and luminal MaSC number after systemic BPA treatment in various developmental windows of the mammary gland of mice and marmoset. Second, a determination of the effect of low dose irradiation on the transformation potential of MaSCs derived from BPA-exposed mice will be accomplished. The hypothesis to be tested for this specific aim is that the transforming activity of BPA may be more evident in combination with a DNA damaging agent such as ionizing radiation, which is a known risk factor for breast cancer. Third, the effect of BPA treatment on MaSC function of obese mice and marmosets will be examined. This proposed research will not only answer the question of whether BPA- induced morphogenesis changes in different developmental windows of mammary gland has a stem cell origin, but also shed light on MaSC susceptibility to multiple risk factor-induced cell transformation such as xenoestrogens, irradiation, and obesity, which will have important implications in disease prevention for human breast cancer.