Arsenic Induced Miotic Arrest Associated Apoptosis

描述（由申请人提供）：砷是世界许多地方饮用水的天然污染物，是已知的人类致癌物质，在EPA危险化学品清单上排名第一。最常与慢性砷中毒有关的癌症是皮肤鳞状细胞癌和基底细胞癌。砷如何导致癌症尚不清楚。然而，国家研究理事会关于饮用水中砷的报告得出结论，最可能的作用方式是诱导染色体数量和结构异常。亚砷酸盐是在饮用水中发现的砷的致癌形式，它破坏有丝分裂，导致后期延迟，并在正常二倍体人成纤维细胞和外周血淋巴细胞中诱导非整倍体，以及在p53缺陷的人成纤维细胞中诱导有丝分裂阻滞相关凋亡（MAAA）。p53缺陷的人细胞对砷诱导的MAAA的敏感性表明，砷致癌的机制不同于阳光诱导的皮肤致癌，其中p53突变是早期和常见的事件。待研究的假设是，p53通过激活G2检查点反应来缓解亚砷酸盐诱导的后期阻滞，所述G2检查点反应使细胞周期蛋白B/cdc 2失活并解除有丝分裂出口网络的抑制，并允许细胞逃避亚砷酸盐诱导的MAAA。砷中毒细胞中的细胞凋亡的预防使得有丝分裂破坏后的遗传不稳定性（非整倍体）。鉴定与p53或p53调节基因相互作用以防止有丝分裂阻滞相关凋亡并允许细胞延迟通过有丝分裂的细胞因子将提供关于亚砷酸盐作用模式的有价值的信息。建议的具体目标是：（1）。确定在有丝分裂中被亚砷酸盐阻滞的p53（+）和p53（-）细胞中G2检查点通路的激活; 2.）通过G2检查点蛋白的过表达和靶向敲低来测试G2检查点激活在逃离亚砷酸盐诱导的后期阻滞中的作用; 3.）检测砷相关皮肤肿瘤是否为p53野生型或突变型。这些研究的结果将确定球员介导释放亚砷酸诱导有丝分裂停滞，并将提供有价值的信息砷诱导的致癌作用的机制，线索亚砷酸盐作为化疗剂的有用性和有价值的信息有丝分裂破坏药物杀死人类细胞的作用模式。

DESCRIPTION (provided by applicant): Arsenic is a natural contaminant of drinking water in many parts of the world, is a known human carcinogen and is #1 on the EPA list of hazardous chemicals. Cancers most often associated with chronic arsenism are squamous and basal cell carcinomas of the skin. How arsenic causes cancer is unknown. However, the National Research Council Report on Arsenic in Drinking Water concluded that the most likely mode of action is induction of numerical and structural chromosomal abnormalities. Arsenite, the carcinogenic form of arsenic found in drinking water, disrupts mitosis causing an anaphase delay and induces aneuploidy in normal diploid human fibroblasts and peripheral blood lymphocytes, and mitotic arrest associated apoptosis (MAAA) in p53 deficient human fibroblasts. The sensitivity of p53 deficient human cells to arsenite induced MAAA suggests that the mechanism of arsenite carcinogenesis is different than sunlight induced skin carcinogenesis in which p53 mutation is an early and common event. The hypothesis to be investigated is that p53 relieves the arsenite-induced anaphase block by activation of the G2 checkpoint response which inactivates cyclin B/cdc2 and derepresses the mitotic exit network and allow the cells to escape arsenite induced MAAA. It is the prevention of apoptosis in arsenic intoxicated cells that allows genetic instability (aneuploidy) after mitotic disruption. Identification of the cellular factors that interact with p53 or the p53 regulated genes to prevent mitotic arrest associated apoptosis and to allow cells to proceed through mitosis with a delay will provide valuable information regarding the mode of action of arsenite. The specific aims proposed are: 1.) Determine activation of the G2 checkpoint pathway in p53(+) and p53(-) cells arrested by arsenite in mitosis; 2.) Test by overexpression and targeted knockdown of G2 checkpoint proteins the role of G2 checkpoint activation in the escape from arsenite induced anaphase block; 3.) Test whether arsenic associated skin tumors are p53 wild type or mutant. The results of these studies will identify players mediating release from arsenite induced mitotic arrest, and will provide valuable information on the mechanism of arsenic induced carcinogenesis, clues to the usefulness of arsenite as a chemotherapeutic agent and valuable information on the mode of action of mitosis disrupting drugs in killing human cells.