Carcinogen Inactivation Of Tumor Suppressor Genes In P53

P53 中肿瘤抑制基因的致癌物质失活

• 批准号: 6681846
• 负责人: JOHN EDGAR FRENCH
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6681846
• 关键词: benzene; bladder neoplasm; carbopolycyclic compound; carcinogen testing; carcinogens; chemical carcinogenesis; environment related neoplasm /cancer; gene dosage; gene environment interaction; gene targeting; laboratory mouse; loss of heterozygosity; lymphoma; mutagen testing; neoplasm /cancer genetics; p53 gene /protein; sarcoma; single strand conformation polymorphism; species difference; tumor suppressor genes

Human and rodent trans-species carcinogens often demonstrate similar organotropic patterns of neoplasia and loss of heterozygosity (LOH)[See Figure 1 and Table 1 below]. Recently, we have observed significant chromosome 11 LOH in B6.129-Trp53tm1Brd N5 mice heterozygous for a p53 null allele using simple sequence length polymorphic loci analysis (see Figure 2). Primers specific for known SSLP loci revealed amplicons consistent with the two strains, C57BL/6 and 129Sv, present in the mice. The degree of heterozygosity observed on chromosome 11was unexpected because the mice were reported to be on a C57BL/6-Trp53 (N5) background which would be approximately 3% 129Sv alleles primarily flanking the null allele (129 embryonic stem cell origin). By exploiting the observed heterozygosity on chromosome 11 in the 5th backcross generation, we learned that LOH was not restricted to theTrp53 locus as determined by Southern analysis of genomic DNA from tumors and control tissue. A complete copy of chromosome 11 of maternal origin carrying the p53 wildtype allele was lost during exposure to phenolphthalein resulting in thymic lymphomas in these mice. The investigation confirmed a chromosome 11 non-dysjunction mechanism of action for phenolphthalein as revealed by allelotype analysis based on comparison to the germline pattern of SSLP loci. Chromosome 11 loss also occurred in benzene and p-cresidine induced p53 (+/-) mouse sarcomas (oral, intubation) and thymic lymphomas (inhalation, whole animal) and bladder tumors (dietary), respectively. The results establish microsatellite (SSLP loci) mapping as a useful tool for determination of LOH in tumor studies using p53 haploinsufficient mice. We hypothesize that carcinogen induced DNA damage in the p53 haploinsufficient mice resulted in either chromosome 11 mis-segregation or recombination during induced repair processes that induced LOH resulting in genomic instability leading to neoplasia. In summary, we have shown that in independent studies that there is sufficient heterozygosity on chromosome 11 in the heterozygous p53 deficient (+/-) N5 generation mouse to use microsatellite markers at 5 cM intervals to demonstrate whole or partial chromosome loss through non-disjunction and homologous recombination.

人类和啮齿动物跨物种致癌物通常表现出相似的肿瘤和杂合性缺失（洛）的器官嗜性模式[见图1和下表1]。最近，我们使用简单序列长度多态性位点分析，在p53无效等位基因杂合子的B6.129-Trp 53 tm 1Brd N5小鼠中观察到显著的11号染色体洛（见图2）。已知SSLP基因座的特异性引物揭示了与小鼠中存在的两种菌株C57 BL/6和129 Sv一致的扩增子。在11号染色体上观察到的杂合性程度是出乎意料的，因为据报道小鼠处于C57 BL/6-Trp 53（N5）背景，这将是约3%的129 Sv等位基因主要侧接无效等位基因（129胚胎干细胞来源）。通过利用在第5代回交中观察到的11号染色体上的杂合性，我们了解到洛并不局限于Trp 53位点，这是通过对来自肿瘤和对照组织的基因组DNA的Southern分析确定的。携带p53野生型等位基因的母体11号染色体的完整拷贝在暴露于酚酞期间丢失，导致这些小鼠的胸腺淋巴瘤。该研究证实了染色体11非异常连接的作用机制，酚酞揭示了等位基因型分析的基础上比较的SSLP基因座的种系模式。苯和对克瑞西定诱导的p53（+/-）小鼠肉瘤（口腔，插管）和胸腺淋巴瘤（吸入，整个动物）和膀胱肿瘤（饮食），分别发生11号染色体丢失。结果建立微卫星（SSLP位点）定位作为一个有用的工具，用于确定洛缺失的肿瘤研究中使用p53单倍不足的小鼠。我们假设致癌物诱导的DNA损伤在p53单倍不足的小鼠导致染色体11错误分离或重组在诱导修复过程中，诱导洛缺失，导致基因组不稳定，导致肿瘤。总之，我们已经在独立研究中表明，在杂合p53缺陷（+/-）N5代小鼠中，11号染色体上有足够的杂合性，可以使用5 cM间隔的微卫星标记来证明通过非分离和同源重组导致的全部或部分染色体丢失。