DEVELOPMENT OF AN IN VIVO MODEL OF GENOMIC INSTABILITY (LACI--P53(+/-)MICE)

工作总结：P53蛋白对细胞功能和 保持基因组的完整性以应对环境 应激，包括化学和物理致癌物质。还原的p53基因 剂量(杂合P53基因缺陷小鼠)本身不足以 导致基因组不稳定并导致癌症。然而，我们和其他人， 已经证明了P53基因缺陷的小鼠暴露在化学和 物理致癌物很快就会引发癌症。洞察力和 了解器官/组织诱导的机制基础 使用模型致癌物的特定癌症对发展很重要 致癌物识别和最小化暴露的方法以及 制定干预和预防的公共卫生战略。这个 致癌物质，对氯仿、苯和酚酞各迅速 诱发部位特异性肿瘤(膀胱、组织细胞肉瘤或胸腺 P53(/-)杂合缺陷型C57BL/6小鼠的恶性淋巴瘤 (HET P53定义)。这一发现与假设一致，即 涉及TrP53基因座的失活突变或杂合性缺失在 啮齿类动物和人类癌症。每种致癌物都会诱发肿瘤 显示不同程度的野生型P53等位基因缺失 (酚酞；苯；对氯沙林)在het p53 def小鼠体内。使用 高频(苯)或完全(酚酞)丧失 野生型等位基因(Southern分析)未发现P53失活突变 可能会被找到。然而，在芳香胺诱导的情况下 膀胱肿瘤，我们未能观察到P53外显子的失活突变 5-9通过P53免疫组织化学、冷SSCP分析或限制性 聚合酶链式反应扩增外显子5-8的测序。尽管，使用相同的小鼠 携带LacI中性报告基因的菌株 证明膀胱被诱变了。这些数据说明 致癌物和组织特异性P53等位基因的显著差异 损失。因此，我们建立了模型来研究它们之间的关系 P53基因剂量、失活突变和潜在的 染色体不稳定的机制。

Summary of Work: The p53 protein is critical for cell function and maintaining the integrity of the genome in response to environmental stresses, including chemical and physical carcinogens. Reduced p53 gene dosage (heterozygous p53 deficient mice)by itself is insufficient to induce genomic instability and to cause cancer. However, we, and others, have demonstrated that p53 deficient mice exposed to chemical and physical carcinogens rapidly develop cancer. Gaining insight and understanding the mechanistic basis for induction of organ/tissue specific cancer using model carcinogens is important to developing methods for carcinogen identification and minimizing exposure as well as developing public health strategies for intervention and prevention. The carcinogens, p-cresidine, benzene, and phenolphthalein each rapidly induce site specific tumors (bladder, histiocytic sarcoma, or thymic lymphoma, respectively) in heterozygous p53 (+/-) deficient C57BL/6 mice (het p53 def). The findings are consistent with the hypothesis that inactivating mutations or LOH involving the trp53 locus are critical in rodent as well as human cancers. Each carcinogen induced tumors that demonstrated different levels of wild type p53 allele loss (phenolphthalein > benzene > p-cresidine) in the het p53 def mice. With either high frequency (benzene) or complete (phenolphthalein) loss of the wild type allele (Southern analysis) no inactivating mutations in p53 could be found. However, in the case of the aromatic amine induced bladder tumors, we failed to observe inactivating mutations in p53 exons 5-9 by either p53 immunohistochemistry, cold SSCP analysis, or limited sequencing of PCR amplified exon 5-8. Although, using mice of the same strain carrying the lacI neutral reporter gene we were able to demonstrate that the bladder was mutagenized. These data demonstrates the dramatic difference in carcinogen and tissue specific p53 allele loss. Thus, we have established models to investigate the relationship between p53 gene dosage, inactivating mutations, and the potential mechanism of chromosomal instability.