Auto-Feedback Regulation of Beta-catenin in Human Cancer

人类癌症中β-连环蛋白的自动反馈调节

• 批准号: 6908698
• 负责人: BO LIU
• 金额: $ 26.4万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-05-01 至 2010-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6908698
• 关键词: adenomatous polyps; biological signal transduction; cell line; colon neoplasms; cytoskeletal proteins; gene deletion mutation; genetic regulation; genetically modified animals; green fluorescent proteins; intestinal mucosa; laboratory mouse; molecular chaperones; molecular oncology; neoplasm /cancer genetics; neoplastic transformation; protein protein interaction; transcription factor; tumor suppressor proteins

DESCRIPTION (provided by applicant): Beta-catenin is a key activator of Wnt signaling target genes. Aberrant activation of beta-catenin through mutational inactivation of its negative regulators has been implicated in the pathogenesis of several common human cancers. Recent studies from our laboratory have demonstrated that beta-catenin is subject to an autofeedback regulation after the adenomatous polyposis coli (APC) tumor suppressor protein mediated regulatory mechanism failed due to mutation. Functional screening of a cDNA library constructed by enriching beta-catenin induced genes through subtraction has lead to the identification the scaffolding protein Axin2, a target gene of beta-catenin. A homolog of Conductin or mouse Axil, Axin2 was previously identified as a negative regulator of Wnt/beta-catenin signaling by several other laboratories. Our transient expression experiments revealed a novel function of Axin2 in the destruction of beta-catenin that is uniquely different from that of the APC-mediated regulatory mechanism. We hypothesize that auto-feedback regulation of beta-catenin by Axin2 is an important mechanism of canonical Wnt/beta-catenin signaling. Based on this hypothesis, we suggest: 1) downregulation of beta-catenin requires a synergetic effect contributed by both APC and Axin 2; and 2) failure of Axin2-mediated auto-feedback regulation will lead to aberrant activation of beta-catenin and consequently neoplastic transformation. We propose to test this hypothesis using a combination of genetic and biochemical approaches as outlined in the following specific aims. AIM I: To assess whether synergistic cooperation between APC and Axin2 is required for the downregulation of beta-catenin using a set of genetically engineered colon cancer cell lines as the in vitro model system; and AIM II: To test whether loss of the auto-feedback function of Axin2 will cause aberrant activation of beta-catenin and tumorigenesis in vivo using genetically engineered mutant mice harboring heterozygous Axin2 allele. AIM III: To define the contribution of individual protein domains to the Axin2 tumor suppressor function, and use these information to delineate the unique features in Axin2-mediated destruction of beta-catenin. The long term goal of these proposed studies is to gain new mechanistic information concerning the pathogenesis of beta-catenin in human cancer, with the objective of identifying key cellular targets useful for rational cancer prevention and therapy.

描述（由申请人提供）：β -连环蛋白是Wnt信号靶基因的关键激活因子。β -连环蛋白通过其负调节因子的突变失活而异常激活，与几种常见人类癌症的发病机制有关。我们实验室最近的研究表明，在大肠腺瘤性息肉病（APC）肿瘤抑制蛋白介导的调节机制因突变而失效后，β -连环蛋白受到自反馈调节。对β -catenin诱导基因进行减法富集构建的cDNA文库进行功能筛选，鉴定出β -catenin的靶基因——支架蛋白Axin2。作为传导素或小鼠Axil的同源物，Axin2先前被其他几个实验室鉴定为Wnt/ β -连环蛋白信号的负调节因子。我们的瞬时表达实验揭示了Axin2在破坏β -连环蛋白中的一种新功能，这种功能与apc介导的调节机制截然不同。我们假设Axin2对β -catenin的自反馈调节是典型Wnt/ β -catenin信号传导的重要机制。基于这一假设，我们认为：1)β -catenin的下调需要APC和Axin 2的协同作用；2) axin2介导的自反馈调节的失败将导致β -连环蛋白的异常激活，从而导致肿瘤转化。我们建议使用遗传和生化方法的结合来检验这一假设，如下所述的具体目标。目的1：利用一组基因工程结肠癌细胞系作为体外模型系统，评估APC和Axin2是否需要协同合作下调β -连环蛋白；AIM II：利用携带杂合Axin2等位基因的基因工程突变小鼠，检测Axin2自反馈功能的丧失是否会导致体内β -连环蛋白的异常激活和肿瘤发生。目的III：定义单个蛋白结构域对Axin2肿瘤抑制功能的贡献，并利用这些信息描述Axin2介导的β -连环蛋白破坏的独特特征。这些拟议的研究的长期目标是获得关于β -连环蛋白在人类癌症发病机制的新机制信息，目的是确定有助于合理预防和治疗癌症的关键细胞靶点。