Effects of Arsenic on PI-3K Signaling Pathway

描述（由申请人提供）：尽管砷被认为对人类皮肤具有高度致癌性，但其在细胞和分子水平上的作用尚不清楚。据认为，亚砷酸盐诱导的细胞增殖是涉及其致癌活性的中心事件之一。我们的初步数据显示，亚砷酸盐处理细胞的结果在激活磷脂酰肌醇3-激酶（PI-3 K）和下游激酶，蛋白激酶B（Akt）和p70 S6激酶（p70 S6 k），以及增加细胞周期蛋白D1的诱导，细胞增殖和转化的人角质形成细胞。考虑到PI-3 K及其下游激酶在细胞周期蛋白D1诱导、细胞增殖和转化中的重要作用，本研究的主要假设是PI-3 K及其下游信号通路在亚砷酸盐诱导的人角质形成细胞的细胞周期蛋白D1表达、细胞增殖和转化中起关键作用。长期目标是阐明亚砷酸盐导致人类皮肤癌发展的分子机制。本提案的总体目的是测试亚砷酸盐对PI-3 K信号转导通路的影响及其在人类角质形成细胞中调节细胞周期蛋白D1表达、细胞增殖和转化的作用。特别地，我们将根据以下可检验的假设和特定目的（SA）来研究这个问题：SA 1：为了检验PI-3 K是亚砷酸盐处理的人角质形成细胞中Akt和p70 S6 k活化所需的假设。SA 2：目的探讨PI-3 K/Akt/p70 s6 k信号通路在亚砷酸钠诱导人角质形成细胞cyclin D1表达和细胞增殖中的作用。SA 3：检验PI-3 K/Akt/p70 S6 k通路在亚砷酸盐诱导的人角质形成细胞的细胞转化中起作用的假设。SA 4：检验AP-1和/或NF κ B是响应于亚砷酸盐处理的人角质形成细胞中的下游转录因子的假设。SA 5：为了验证这一假设，AP-1和/或NF κ B的激活是诱导细胞周期蛋白D1的表达，细胞增殖和细胞转化所需的亚砷酸盐在HaCat细胞。本申请中提出的研究的意义在于，从所提出的研究中得出的结果将极大地促进对人体皮肤中亚砷酸盐引起癌症发展的分子机制的理解。更好地了解导致诱导细胞周期蛋白D1表达，细胞增殖和转化的信号转导途径，将提供设计更有效的预防和治疗砷引起的癌症的药物所需的有价值的信息。这些药物可能干扰导致细胞周期蛋白D1诱导、细胞增殖和细胞转化的信号传导途径。

DESCRIPTION (provided by applicant): Although arsenic is acknowledged to be highly carcinogenic to human skin, its action at the cellular and molecular level is not well understood. It is thought that arsenite-induced cell proliferation is one of the central events involved in its carcinogenic activity. Our preliminary data have revealed that treatment of cells with arsenite results in the activation of phosphatidylinositol 3-kinase (PI-3K) and downstream kinases, protein kinase B (Akt) and p70 S6 kinase (p70S6k), as well as an increase in cyclin D1 induction, cell proliferation and transformation in human keratinocytes. Considering the essential role of PI-3K and its downstream kinases in cyclin D1 induction, cell proliferation and transformation, the main hypothesis of this proposal is that PI-3K and its downstream signaling pathways play a pivotal role in arsenite-induced cyclin D1 expression, cell proliferation and transformation in human keratinocytes. The long-term goal is to elucidate the molecular mechanisms by which arsenite causes human skin cancer development. The overall aim of this proposal is to test the effect of arsenite on the PI-3K signal transduction pathway and its role in the regulation of cyclin D1 expression, cell proliferation and transformation in human keratinocytes. Especially, we will investigate this issue in accordance with the following testable hypotheses and specific aims (SA): SA 1: To test the hypothesis that PI-3K is required for the activation of Akt and p70S6k in arsenite-treated human keratinocytes. SA 2: To investigate whether PI- 3K/Akt/p70 s6k pathway plays a role in arsenite-induced cyclin D1 expression and cell proliferation in human keratinocytes. SA 3: To test the hypothesis that PI-3K/Akt/p70S6k pathway plays a role in arsenite-induced cell transformation in human keratinocytes. SA 4: To test the hypothesis that AP-1 and/or NFkappaB are downstream transcription factor(s) in human keratinocytes response to arsenite treatment. SA 5: To test the hypothesis that activation of AP-1 and/or NFkappaB is required for induction of cyclin D1 expression, cell proliferation and cell transformation by arsenite in HaCat cells. The significance of the research proposed in this application is that the results derived from the proposed studies will greatly facilitate the understanding of the molecular mechanism of cancer development caused by arsenite in human skin. A better understanding of signal transduction pathways leading to the induction of cyclin D1 expression, cell proliferation and transformation, will provide valuable information needed for designing more effective agents for the prevention and therapy of cancers caused by arsenite. Such agents could interfere with signaling pathways leading to cyclin D1 induction, cell proliferation and cell transformation.