MOLECULAR GENETICS OF AROMATIC AMINE INDUCED BLADDER CANCER

在100%的雄性p53缺陷（+/-）小鼠中观察到膀胱肿瘤 暴露于0.5%对克立西定（5-甲氧基-2-甲基苯胺）24周后 相比之下，B6 C3 F1小鼠在两年内的75至90周 生物测定 免疫组化分析p53表达阴性 对肿瘤基因组DNA的分析表明， 五分之一的移行细胞癌显示剩余的 野生型等位基因 无突变（冷外显子特异性单链 构象多态性分析），其与 序列鉴定的突变是可检测的。 因此， 一个等位基因，导致p53基因剂量的减少，可能就足够了 通过基因毒性过程中的基因组不稳定性增强肿瘤发生 p53缺陷小鼠的应激，但机制尚不清楚。 膀胱癌相关基因的突变或洛缺失 也可能涉及致癌作用。 此外，我们还观察到， 诱导肝脏的潜伏期急剧减少， 提示p53缺陷可能至少在 在这些小鼠中的肝癌发生。 目前，我们正在研究 来自膀胱肿瘤以及固定的膀胱肿瘤的DNA和RNA 使用原位PCR原位杂交（PCR ISH）检测p53和其他 选定的基因，用于深入了解潜在的分子 机制等 到目前为止，我们一直专注于表征和 p53缺陷小鼠鉴定化学物质的评价 致癌物质。 已生成足够的数据来证明其使用的合理性 在短期致癌研究中， 小鼠致癌潜力。 延迟的大幅减少使得 这是一种用于化学物质剂量测量研究的替代模型， 致癌作用 未来的研究将解决潜在的分子 p53缺陷小鼠对肿瘤细胞的敏感性增加的机制 化学致癌物

Bladder tumors were observed in 100% of male p53-deficient (+/-) mice after 24 weeks exposure to 0.5% p-cresidine (5-methoxy-2-methylaniline) in the diet, compared to 75 to 90 weeks in B6C3F1 mice in a two year bioassay. Immunohistochemical analysis for p53 expression was negative and analysis of the genomic tumor DNA indicated that approximately only one out of 5 transitional cell carcinomas show loss of the remaining wildtype allele. No mutations (cold exon-specific single strand conformational polymorphism analysis), which correlate very well with sequence identified mutations, were detectable. Thus, inactivation of one allele, resulting in reduction in p53 gene dosage, may be sufficient to enhance tumorigenesis through genomic instability during genotoxic stress in p53-deficient mice, but the mechanism remains unclear. Induction of mutations or LOH in other critical genes involved in bladder carcinogenesis may also be involved. In addition, we have also observed the induction of liver with a dramatic decrease in latency, which suggests that p53 deficiency may play at least an indirect role in hepatocarcinogenesis in these mice. At the present time we are examining both DNA and RNA from bladder tumors as well as fixed bladder tumors using in situ PCR in situ hybridization (PCR ISH) for p53 and other selected gene(s) for developing insight into the potential molecular mechanisms. To date we have focused on the characterization and evaluation of p53-deficient mice for the identification of chemical carcinogens. Sufficient data have been generated to justify their use in short term carcinogenesis studies for screening chemicals for their carcinogenic potential in mice. The dramatic reduction in latency make this an alternative model for dose metric studies of chemical carcinogenesis. Future studies will address the potential molecular mechanisms for the increased sensitivity of p53-deficient mice to chemical carcinogens.