MOLECULAR CHARACTERIZATION OF ACF (ABERRANT CRYPT FOCI)

ACF（异常隐窝灶）的分子特征

• 批准号: 6513559
• 负责人: Daniel William Rosenberg
• 金额: $ 23.58万
• 依托单位: UNIVERSITY OF CONNECTICUT SCH OF MED/DNT
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-08-01 至 2004-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6513559
• 关键词: cell type; cellular oncology; chemical carcinogenesis; colon neoplasms; disease /disorder model; drug resistance; gene mutation; genetically modified animals; histopathology; hyperplasia; immunocytochemistry; inbreeding; laboratory mouse; molecular oncology; neoplasm /cancer genetics; neoplastic process; phospholipase A2; preneoplastic state

Aberrant crypt foci (ACF) is a precursor for colon cancer. Human and mouse ACR are either hyperplastic are either hyperplastic or dysplastic, a classification that is based on morphology and their potential to form tumors. Understanding mechanisms that govern formulation of ACFs and their conversion to fully malignant colonic lesions is the focus of this proposal. It is known that heritable characteristics of inbred mice lead to either susceptibility or resistance to formulation of colon tumors after carcinogen treatment. We will test two hypotheses that attempt to define genetic mechanisms that determine differential susceptibility. Specific aim 1: Does malignant potential of ACFs, formed in mice of differing colon tumor susceptibilities, result from the specific complement of gene mutations that target cells acquire? Using the colon carcinogen, azoxymethane, we will generate populations of ACF in mice. We have shown that hyperplastic ACF are produced in resistant strains, but fail to progress in carcinomas. We will conduct a detailed morphometric and genetic analysis of sub-populations of ACFs that will enable us to understand why azoxymethane-induced lesions fail to progress to tumors in resistant AKR mice. Laser capture micro-dissection will be used to isolated DNA from single crypts for mutational analyses of tumor related genes. 1.1 What is the time course of zoxymethane- induced ACF formation in tumor susceptible and resistant mice? 1.2 What functional characteristics distinguish hyperplastic and dysplastic ACF? 1.3 Are there differences between hyperplastic and dysplastic ACFs in the frequency of mutations in K-ras, A[C, beta-catenin and p53? Specific aim 2: Is malignant potential of ACFs controlled by expression of, and signalling by, the secretory phospholipase A2, encoded by the Moml locus? Among genetic factors that affect tumorigenesis factors that affect tumorigenesis in the multiple intestinal neoplasia (Min) model is the gene product of Moml, a calcium-dependent non-pancreatic secretory phospholipase (Pla2g2a [Pla2]). sPla2 plays a role in inflammation and hydrolyzes the sn-2 position of glycerolipids, releasing arachidonic acid for prostaglandin synthesis. We present evidence that sPla2 is differentially expressed in mouse clone in a patter inversely correlated with tumor susceptibility to azoxymethane: A/J < SWR < AKR. This suggests that colonic sPla2 also plays a role in chemically-induced tumorigenesis equivalent to its role in the Min model. We propose to explore the mechanism by which sPla2 affects tumor formation in sensitive and resistant mice. 2.1 What colon cell types produce sPla2/ Are there changes in sPla2 levels or function within and adjacent to carcinogen-induced ACF and tumors? 2.2 Can AKR resistances to carcinogen by reversed with the use of specific inhibitors of sPla2? 2.3 Can over- expression of sPla2 in transgenic A/J mice protect against azoxymethane- induced tumorigenesis?

异常隐窝病灶（ACF）是结肠癌的前兆。人类和小鼠ACR是增生性的，是增生性的或发育不良的，这是一种基于形态学及其形成肿瘤的潜力的分类。了解机制，管理制定的活性碳纤维和他们的转换为完全恶性结肠病变是这个建议的重点。众所周知，近交系小鼠的遗传特征导致致癌物治疗后对结肠肿瘤形成的易感性或抗性。我们将测试两个假设，试图定义决定差异易感性的遗传机制。具体目标1：在不同结肠肿瘤易感性的小鼠中形成的ACF的恶性潜能是否是靶细胞获得的基因突变的特定互补的结果？使用结肠致癌物氧化偶氮甲烷，我们将在小鼠中产生ACF群体。我们已经表明，增生性ACF耐药菌株中产生的，但未能在癌的进展。我们将对ACF亚群进行详细的形态学和遗传学分析，这将使我们能够理解为什么氧化偶氮甲烷诱导的病变在耐药AKR小鼠中不能进展为肿瘤。激光捕获显微切割将用于从单个隐窝中分离DNA，用于肿瘤相关基因的突变分析。1.1在肿瘤易感和耐药小鼠中，氧化偶氮甲烷诱导ACF形成的时间过程是什么？1.2什么功能特征区分增生和异型增生ACF？1.3增生性和发育异常的ACF在K-ras、A[C]、β-连环蛋白和p53突变频率方面是否存在差异？具体目标2：由Moml基因座编码的分泌型磷脂酶A2的表达和信号传导是否控制ACF的恶性潜能？在影响多发性肠肿瘤（Min）模型中的肿瘤发生的遗传因素中，影响肿瘤发生的遗传因素是Moml的基因产物，一种钙依赖性非胰腺分泌型磷脂酶（Pla 2g 2a [Pla 2]）。sPla 2在炎症中起作用，并水解甘油酯的sn-2位，释放花生四烯酸用于前列腺素合成。我们提供的证据表明，sPla 2在小鼠克隆中的差异表达与肿瘤对氧化偶氮甲烷的敏感性呈负相关：A/J < SWR < AKR。这表明结肠sPla 2也在化学诱导的肿瘤发生中起作用，相当于其在Min模型中的作用。我们建议探讨sPla 2影响敏感和耐药小鼠肿瘤形成的机制。2.1什么样的结肠细胞类型产生sPla 2/在致癌物诱导的ACF和肿瘤内和附近是否存在sPla 2水平或功能的变化？2.2使用sPla 2特异性抑制剂能逆转AKR对致癌物的耐药性吗？2.3转基因A/J小鼠中sPla 2的过表达能否保护氧化偶氮甲烷诱导的肿瘤发生？