Role of Estrogen and Iron in Breast Cancer

描述（由申请人提供）：乳腺癌（BC）的发病率在绝经后妇女比绝经前妇女高得多。雌激素是乳腺癌发展的一个众所周知的危险因素。然而，绝经后妇女的总雌激素水平低于绝经前妇女。这种明显的差异需要新的研究来更好地了解BC的病因和机制。在本研究中，我们假设绝经后高铁水平的积累是绝经后女性肿瘤前变化之一，并且在乳房组织中存在高局部雌激素的情况下，铁和雌激素都极大地促进了乳腺肿瘤的生长和氧化损伤。我们将使用携带血色素沉着症（HFE）基因突变的去卵巢（OVX）转基因铁负载小鼠模型来验证这一假设。该模型由于OVX导致雌激素水平降低，但由于HFE基因突变导致铁水平升高，从而模拟绝经后的状况。在Aim1中，我们将评估雌激素在野生型和铁负载HFE+/-小鼠乳腺上皮细胞增殖和自发肿瘤形成中的作用。雌性野生型C57BL6小鼠和HFE+/-小鼠将接受OVX。在植入17β -雌二醇（E2）后，比较Ki-67（一种增殖特异性抗原）和载铁突变型小鼠和野生型小鼠的自发肿瘤发生率。在Aim 2中，我们将评估E2是否在HFE+/-小鼠中诱导比野生型小鼠更高的肿瘤摄取和乳腺癌生长。将MXT+乳腺癌细胞接种于野生型和HFE+/-小鼠乳腺脂肪垫。测量乳腺癌的致瘤性、肿瘤潜伏期及肿瘤体积。将测定和比较乳腺组织中氧化DNA和蛋白质的水平。在Aim 3中，我们将确定e2介导的肿瘤生长是否依赖铁。MXT+细胞系转染转移受体小干扰RNA （siRNA）。将对siRNA转染物和亲本细胞之间的乳腺癌进行测量和比较。我们希望证明铁在雌激素依赖性BC中起重要作用，这一新的研究方向可能会极大地有益于女性婴儿潮一代的健康。

DESCRIPTION (provided by applicant): Breast cancer (BC) incidence rates are much higher in post- than pre-menopausal women. Estrogen is a well-known risk factor for BC development. Yet, total estrogen levels are lower in post- than pre-menopausal women. This apparent discrepancy calls for new research to better understand BC etiology and mechanisms. In the present study, we hypothesize that an accumulation of high iron levels due to menopause is one of the pre-neoplastic changes in post-menopausal women, and in the presence of high local estrogen in the breast tissue, both iron and estrogen greatly promote breast tumor growth and oxidative damage. We will test this hypothesis using an ovariectomized (OVX) transgenic iron-loaded mouse model carrying hemochromatosis (HFE) gene mutation. This model has a decreased estrogen level because of the OVX, but an increased iron level due to the HFE gene mutation, thus mimicking post-menopausal conditions. In Aim1, we will assess the role of estrogen in mammary epithelial proliferation and spontaneous tumor formation in wild-type and iron loaded HFE+/- mice. Female wild-type C57BL6 mice and HFE+/- mice will undergo OVX. After implantation of 17beta-estradiol (E2), Ki-67, a proliferation-specific antigen, and spontaneous tumor incidence of the iron-loaded mutant and wild-type mice will be compared. In Aim 2, we will assess whether E2 induces a higher tumor take and growth of mammary cancer in HFE+/- mice than in wild-type mice. MXT+ mammary cancer cells will be inoculated into the mammary fat pads of wild-type and HFE+/- mice. Mammary cancer tumorigenicity and tumor latency as well as tumor volume will be measured. Levels of oxidative DNA and protein in breast tissues will be determined and compared. In Aim 3, we will determine whether E2-mediated tumor growth is iron-dependent. The MXT+ cell line will be transfected with small interfering RNA (siRNA) of transferring receptor. Mammary cancer will be measured and compared between the siRNA transfectants and the parental cells. We expect to show that iron plays an important role in estrogen-dependent BC and this new direction of research may greatly benefit the health of female baby- boomers.