Radiation and Genomic Instability in Finite Lifespan Human Mammary Epithelium

描述（由申请方提供）：电离辐射是H. J. Muller于1928年确定的第一种环境诱变剂，辐射是已知的人类致癌物。日本原子弹爆炸幸存者的流行病学证据表明，女性乳房对放射性癌症非常敏感。接受乳腺癌治疗的妇女有患新治疗相关乳腺癌的风险，接受胸部放射治疗的妇女也有患霍奇金病的风险。最近的数据表明，年轻女性（<40岁）患放射性乳腺癌的风险更高。我们对辐射如何作为致癌物的理解是有限的。其他人的工作表明，在未经治疗的乳腺活检标本中，从良性增生到恶性肿瘤的最早阶段，基因组不稳定性发生了转变，这表明不稳定基因组的发展是该疾病病因学的关键步骤。我们将测试的核心假设，暴露于电离辐射（X射线）将引起染色体不稳定性的克隆后代有限寿命的人乳腺上皮细胞（HMEC）。这是基于我们的初步发现，即照射一种有限寿命的HMEC菌株导致暴露于2戈伊或更高剂量的单次照射后存活的单次照射细胞后代的核型不稳定性。所用的HMEC菌株（选择后184）来自年轻供体，并且已经通过了第一个衰老屏障，p16表达丧失，但它们保留有限的寿命。这种类型的细胞在组织学正常的乳腺组织中发现于局灶性斑块中，但大多数有限寿命的HMEC（停滞前细胞）没有通过第一个衰老屏障。提出了两个目标。目的1使用来自40岁以下供体的细胞，检验电离辐射暴露导致选择后有限寿命HMEC核型不稳定的假设。目的2检验以下假设：与来自目的1中评价的相同供体的选择后有限寿命HMEC相比，在停滞前HMEC中辐射诱导的核型不稳定性的建立减少。机制研究将确定在建立辐射诱导的核型不稳定性中沉默p16 INK 4a或pRb的要求。这些研究将确定辐射诱导的核型不稳定性是否是一种罕见的或常见的发生后，辐射和是否需要建立表型的过渡过去的第一个衰老障碍。 公共卫生相关性：电离辐射是一种人类致癌物质，日本原子弹爆炸幸存者和医疗照射人群的结果表明，年轻女性乳房对辐射诱发的癌症非常敏感。其他研究表明，基因组不稳定性首先出现在人类乳腺活检材料中最早的恶性阶段-导管原位癌-这表明不稳定性是乳腺癌发展的重要早期特征。提出的实验解决辐射暴露是否elevening持久的基因组不稳定性在后代中的明显正常的有限寿命的人乳腺上皮细胞从捐助者40岁以下，这是否是一个共同的表型之间的个人，以及是否过渡过去的第一个衰老障碍是有限寿命的人乳腺上皮细胞表现出辐射诱导的基因组不稳定性所需的。

DESCRIPTION (provided by applicant): Ionizing radiation was the first environmental mutagen identified by H.J. Muller in 1928, and radiation is a known human carcinogen. Epidemiological evidence from the Japanese atomic bomb survivors indicates that the female breast is exquisitely sensitive to radiogenic cancer. Women treated for breast cancer are at risk for a new treatment associated breast cancer as are women treated with radiation to the chest for Hodgkin's disease. Recent data indicate that younger women (<age 40) are at a higher risk for radiogenic breast cancer. Our understanding of how radiation acts as a carcinogen is limited. Work by others demonstrated that a transition to genomic instability occurs at the transition from benign hyperplasia to the earliest stages of malignancy in untreated breast biopsy specimens, suggesting that development of an unstable genome is a key step in the etiology of the disease. We will test the central hypothesis that exposure to ionizing radiation (x-rays) will elicit chromosomal instability in the clonal descendants of finite lifespan human mammary epithelial cells (HMEC). This is based on our preliminary finding that irradiation of one strain of finite lifespan HMEC led to karyotypic instability amongst the progeny of single irradiated cells surviving exposure to single doses of 2 Gy or more. The strain of HMEC used (post-selection 184) is from a young donor, and has passed the first senescence barrier with a loss of p16 expression but they retain finite lifespan. Cells of this type are found in focal patches in histologically normal breast tissue, but the majority of finite lifespan HMEC (pre-stasis cells) have not passed the first senescence barrier. Two aims are proposed. Aim 1 tests the hypothesis that ionizing radiation exposure elicits karyotypic instability in post-selection finite lifespan HMEC using cells derived from donors below the age of 40. Aim 2 tests the hypothesis that the establishment of radiation-induced karyotypic instability is reduced in pre-stasis HMEC compared with post-selection finite lifespan HMEC from the same donors evaluated in Aim 1. Mechanistic studies will determine the requirements for silencing of p16INK4a or pRb in the establishment of radiation-induced karyotypic instability. These studies will determine whether radiation-induced karyotypic instability is a rare or a common occurrence after irradiation and whether a transition past the first senescence barrier is required for establishment of the phenotype. PUBLIC HEALTH RELEVANCE: Ionizing radiation is a human carcinogen, and results from the Japanese atomic bomb survivors and medically exposed populations have demonstrated that the young female breast is very sensitive to radiation-induced cancer. Others have shown that genomic instability first appears in human breast biopsy materials at the earliest malignant stage - ductal carcinoma in situ - suggesting that instability is an important early feature in the development of breast cancer. The experiments proposed address whether radiation exposure elicits persistent genomic instability in the progeny of apparently normal finite lifespan human mammary epithelial cells from donors below age 40, whether this is a common phenotype amongst individuals, and whether transition past the first senescence barrier is required for finite lifespan human mammary epithelial cells to exhibit radiation induced genomic instability.