Arsenic carcinogenicity: Metabolic disruption leads to loss of PTEN function

描述（由申请人提供）：人类砷暴露被称为现代人类历史上最严重的环境中毒。砷对人体的毒性会导致多种靶组织的癌症，包括肺、膀胱和皮肤。尽管无可争议的流行病学，可重复证实砷致癌性，没有明确的机制解释砷的致癌作用存在。磷酸酶和张力蛋白同源物（PTEN）基因是一种肿瘤抑制基因，在人类癌症研究中占有独特的地位，因为它可以说是唯一的肿瘤抑制基因，通常涉及通过功能丧失在家族性和散发性癌症。PTEN的主要肿瘤抑制机制是通过其失活Akt途径，Akt途径是细胞存活和增殖的中心效应物。Akt激活是体外慢性砷暴露的常见结果，包括砷诱导恶性转化的细胞培养模型。该项目旨在测试一种新的机制，通过这种机制，砷暴露可以抑制PTEN，导致其肿瘤抑制功能的丧失，从而导致Akt激活和砷诱导的致癌作用。利用细胞培养模型进行恶性转化的体外研究，我们的初步数据表明，无机三价砷的一般作用 砷暴露是细胞代谢的破坏，包括诱导有氧糖酵解和细胞内NADH水平升高。这是令人感兴趣的，因为已经证明PTEN活性被升高的NADH抑制。我们推测砷的致癌作用的一个重要机制是它能够干扰基本的细胞代谢，导致NADH水平升高，以及肿瘤抑制因子PTEN的功能丧失。两个具体目标将检验这一假设。目的1将定义时间关系和PTEN活性，Akt激活，与BEAS-2B细胞中恶性肿瘤的获得相关的关键表型之间的关联长期暴露于非细胞毒性，环境相关浓度的亚砷酸盐。目的2旨在纳入目的1中收集的数据，以影响衍生BEAS-2B细胞系中持续的、实验调节的、增加的和降低的NADH水平。这些BEAS-2B细胞系将接受目标1中使用的恶性转化方案（1 μ m亚砷酸盐约17周）。我们的假设预测，上调或下调NADH水平将导致增强或减弱恶性转化，分别。这个R 03项目提出了一个新的机制，涉及在环境致癌细胞信号的代谢控制的初步测试。

DESCRIPTION (provided by applicant): Human arsenic exposure has been referred to as the worst environmental poisoning in modern human history. Arsenic toxicity in exposed humans causes cancer in diverse target tissues, including lung, bladder and skin. Despite incontrovertible epidemiology that repeatable confirms arsenic carcinogenicity, no definitive mechanism explaining the carcinogenic action of arsenic exists. The phosphatase and tensin homologue (PTEN) gene is a tumor suppressor gene that holds a unique place in human cancer research, in that it is arguably the only tumor suppressor gene that is commonly involved through loss of function in both familial and sporadic cancers. The principal tumor-suppressive mechanism of PTEN is through it inactivation of the Akt pathway, a central effector of cell survival and proliferation. Akt activation is a frequently reported consequence of chronic arsenic exposure in vitro, including cell culture models of arsenic-induced malignant transformation. This project seeks to test a novel mechanism by which arsenic exposure could inactivate PTEN, leading to loss of its tumor-suppressive function, leading to Akt activation and arsenic-induced carcinogenesis. Using a cell culture model amenable to in vitro studies of malignant transformation, our preliminary data establish that a general effect of inorganic trivalent arsenic (arsenite) exposure is the disruption of cellular metabolism, including the induction of aerobic glycolysis and elevation of intracellular NADH level. This is intriguing because PTEN activity has been demonstrated to be inhibited by elevated NADH. We hypothesize that an important mechanism of arsenic's carcinogenic action is its ability to disturb fundamental cell metabolism, leading to elevated NADH levels, and the functional loss of the tumor suppressor, PTEN. Two specific aims will test this hypothesis. Aim 1 will define the temporal relationship and associations between PTEN activity, Akt activation, and key phenotypes associated with the acquisition of malignancy in BEAS-2B cells chronically exposed to a non-cytotoxic, environmentally relevant concentration of arsenite. Aim 2 is designed to incorporate data collected in Aim 1 to affect sustained, experimentally modulated, increased and decreased NADH level in derived BEAS-2B cell lines. These BEAS-2B cell lines will be subjected to the malignant transformation protocol used in Aim 1 (1 um arsenite for approximately 17 weeks). Our hypothesis predicts that upward or downward modulation of NADH level will result in enhanced or diminished malignant transformation, respectively. This R03 project proposes an initial test of a novel mechanism involving metabolic control of cell signaling in environmental carcinogenesis.