25-hydroxy-D3 as a possible chemopreventive agent for breast cancer

说明(申请人提供)：1，25(OH)2D3是维生素D作用的活性代谢物，是维生素D受体的配体。虽然在生理浓度下，它可能是无毒的，但在这个水平上，它也没有任何化学预防活性。在较高浓度时，它具有高度的钙化作用。随着最近发现1a(OH)酶(CYP27B1)在多种维生素D靶组织中的表达，25(OH)D3有可能作为血清中的主要天然保护剂。细胞色素P27B1可将其转化为细胞内活性的1，25(OH)2D3，从而发挥细胞生长调节和分化的作用。在这项研究中，我们将验证25(OH)D3通过转化为1，25(OH)2D3来维持细胞分化和抑制转化的假说。长期目标是开发25(OH)D3作为乳腺癌的天然化学预防药物。由于25(OH)D3转化为活性1，25(OH)2D3的关键是乳腺上皮细胞中的维生素D代谢酶CYP27B1，我们设计了两个特定的目标来系统地解决这个问题：目的1.证明CYP27B1在正常乳腺和乳腺癌上皮中的表达和调控。为此，我们提出了三个问题：1.正常乳腺上皮细胞和肿瘤乳腺上皮细胞在转录和翻译水平上的表达有无差异？2.细胞色素P27B1的表达和调控与细胞分化有关吗？3.细胞色素P27B1的转录(或启动子调控)是否具有组织特异性？如果转录是组织特异性的，25(OH)D3是否有可能用于乳腺癌的化学预防和治疗？目的2.确定25(OH)D3在乳腺癌化学预防中的作用。为此，我们提出了三个问题：1.25(OH)D3是否抑制乳腺上皮细胞的增殖或诱导其分化？2.25(OH)D3是否抑制DMBA诱导的乳腺病变的形成？这种作用在病变形成的起始或促进阶段是否具有选择性？3.25(OH)D3是否保护正常乳腺上皮细胞免受致癌物质诱导的转化？这项研究的结果将确定25(OH)D3在乳腺癌化学预防中的作用，并形成更广泛的RO1应用的基础。

DESCRIPTION (provided by applicant): 1,25(OH)2 D3 is the active metabolite of vitamin D action and serves as a ligand for vitamin D receptors. Although at a physiological concentration, it may not be toxic, it also does not have any chemopreventive activity at this level. At higher concentrations it is highly calcemic. With recent discovery that 1a(OH)ase (CYP27B1) is expressed in multiple vitamin D target tissues, it is possible that 25(OH)D3 can be used as a major natural protective agent in serum. It can be converted to the active 1,25(OH)2D3 in the cells by CYP27B1, allowing its function in cell growth modulation and differentiation. In this study, we will test the hypothesis that the 25(OH)D3 maintains the cell differentiation and inhibits transformation by conversion to 1,25(OH)2D3 in normal breast epithelial cells expressing CYP27B1. The long term goal is to develop 25(OH)D3 as a natural chemopreventive agent for breast cancer. Since the key for the conversion of 25(OH)D3 to active 1,25(OH)2D3 is vitamin D metabolizing enzyme CYP27B1 in breast epithelial cells, we have designed two specific aims to systematically address this issue in this project: Aim 1. To demonstrate the expression and regulation of CYP27B1 in both normal breast and breast cancer epithelial. For this aim, we ask three questions: 1. Is there any difference in expression of CYP27B1 between normal and tumor breast epithelial cells at transcriptional and translational levels? 2. Is CYP27B1 expression and regulation related to cell differentiation? 3. Is transcription (or promoter regulation) of CYP27B1 tissue specific? If transcription is tissue specific, is there any potential use of 25(OH)D3 for breast cancer chemoprevention and therapy? Aim 2. To determine the functional role of 25(OH)D3 in breast cancer chemoprevention. For this aim, we ask three questions: 1. Does 25(OH)D3 inhibit cell proliferation or induce differentiation in breast epithelial cells? 2. Does 25(OH)D3 inhibit the mammary alveolar lesion formation induced by DMBA and whether this effect is selective during the initiation or promotion phases of lesion formation? 3. Does 25(OH)D3 protect normal breast epithelial cells against transformation induced by carcinogen treatment? Results generated from this study will establish the role of 25(OH)D3 in breast cancer chemoprevention and form the basis of a more extensive RO1 application.