Inorganic phosphate regulated proliferation, transformation and tumorigenesis

说明(申请人提供)：无机磷在许多层面上对人体至关重要。在细胞水平上，它是能量代谢、激酶信号以及DNA和脂质的形成和功能所必需的组成部分。传统上，无机磷被认为是这些过程所需的被动离子，然而，最近的数据表明，这种离子在调节细胞功能方面发挥了更积极的作用。已发表的和初步的体外实验结果表明，多种类型的细胞暴露于高浓度的无机磷会改变生长特性、特定的信号转导途径和基因表达，包括癌症和转移相关因子，如骨桥蛋白、c-fos、EGR1和COX-2。我们在体内的初步结果证实了体外研究，并表明血清无机磷水平改变了皮肤癌变的两阶段模型的肿瘤发生。综上所述，有效无机磷水平可能是细胞生长和转化潜力的一个重要易感风险因素。血清无机磷的主要来源是饮食摄入，部分由于加工食品消费量的增加，美国人饮食中的无机磷含量继续上升，高于FDA认为的高水平。尽管饮食对功能基因组学有深远的影响越来越明显，然而，迄今为止，对血清磷水平变化的分子和细胞反应的研究才刚刚开始。这一提议将检验这样的假设：有效无机磷的数量通过特定的细胞和分子调控信号改变细胞的生长和转化潜力。为了验证这一假设，我们将利用已定义的体外细胞培养转化模型进行机制研究，并结合已建立的皮肤癌发生的两阶段模型来确定生理相关性。1)确定无机磷调控增殖和转化的细胞和分子机制：这一系列研究将检验一种假说，即磷酸盐转运与成纤维细胞生长因子受体激活相结合，调节小GTP结合蛋白N-ras和随后的AP-1转录激活，这是磷酸盐诱导的增殖和转化反应所必需的。2)明确饮食中无机磷在体内增殖、转化和致癌中的作用：在DMBA/TPA两阶段皮肤癌模型中，这一目的将检验减少膳食无机磷摄入量将减少肿瘤发生的假设。 与公众健康相关：无机磷是一种常见的饮食元素，美国人饮食中的磷含量持续上升，超过了FDA认为的高水平。近年来，无机磷被证明可以改变多种细胞的基因表达和生长表型，然而，关于饮食中磷的摄入量对人类健康的影响的研究很少。这项建议将调查饮食中无机磷在癌症发生、促进和进展中的作用。

DESCRIPTION (provided by applicant): Inorganic phosphate is critical to the human body on many levels. At the cellular level it is required as a component of energy metabolism, kinase signaling and in the formation and function of DNA and lipids. Traditionally, inorganic phosphate has been thought of as a passive, required ion for these processes, however, recent data suggests a more active role for this ion in the regulation of cell function. Published and preliminary in vitro results have revealed that exposure of a variety of cell types to elevated inorganic phosphate will alter growth properties, specific signal transduction pathways, and gene expression, including cancer and metastasis related factors such as osteopontin, c-fos, Egr1 and Cox-2. Our preliminary in vivo results corroborate the in vitro studies and suggest that the levels of serum inorganic phosphate alter tumorigenesis in the two-stage model of skin carcinogenesis. Taken together the results suggest that the level of available inorganic phosphate may be an important predisposing risk factor to the growth and transformation potential of cells. The main source of serum inorganic phosphate is from dietary intake and due, in part, to the increased consumption of processed foods, the amount of inorganic phosphate in the American diet continues to rise above levels already considered high by the FDA. Although it is becoming increasingly apparent that diet can have profound effects on functional genomics, however, to date the molecular and cellular responses to changes in serum phosphate levels have only begun to be investigated. This proposal will test the hypothesis that; the amount of available inorganic phosphate alters the growth and transformation potential of cells through specific cellular and molecular regulatory signals. To test the hypothesis we will utilize defined in vitro cell culture models of transformation for mechanistic studies in combination with the established two-stage model of skin carcinogenesis to determine physiological relevance. The studies propose herein will: 1) Determine the cellular and molecular mechanisms of inorganic phosphate regulated proliferation and transformation: This line of investigation will test the hypothesis that phosphate transport in combination with FGF receptor activation regulates the small GTP binding protein, N-ras and subsequent AP-1 transcriptional activation necessary for the phosphate-induced proliferation and transformation response. 2) Define the role of dietary inorganic phosphate on proliferation, transformation and tumorigenesis in vivo: This aim will test the hypothesis that reducing dietary inorganic phosphate consumption will decrease tumorigenesis in the DMBA/TPA two-stage skin carcinogenesis model. PUBLIC HEALTH RELEVANCE: Inorganic phosphate is a common dietary element and the amount in the American diet continues to rise above levels already considered high by the FDA. Inorganic phosphate has recently been demonstrated to alter gene expression and the growth phenotype of a variety of cell types however, there is little research regarding the affects of dietary phosphate intake on human health. This proposal will investigate the role of dietary inorganic phosphate in cancer initiation, promotion and progression.