IN VIVO MUTAGENESIS STUDIES USING TRANSGENIC MICE

大蓝鼠携带着30-40个拷贝的转基因整合 噬菌体Lambda，每个噬菌体携带一份大肠杆菌Laci 基因，它被用作体内诱变研究的报告。这个 这些研究的目标是利用laci基因对组织进行量化 作为潜在启动事件的特定基因组突变 致癌。我们继续努力定义试验性的 以及有助于分析体内突变的统计方法。在……里面 此外，我们正在使用大型蓝色系统来评估 细胞增殖对突变产量的影响 或者没有DNA损伤。黄曲霉毒素的体内致突变活性 致癌物/非致癌物对，2，4-或2，6-二氨基甲苯与 这些异构体的致癌潜力。细胞增殖 2，4-DAT的诱导似乎是产生 大蓝鼠肝脏的突变反应。我们还有 探讨肝部分切除后肝细胞增殖对肝细胞增殖的影响 在肝脏中产生的突变的产率，无论是否有 用强效诱变剂ENU进行预处理。Enu在肝脏中具有突变性 在没有肝切除的情况下；然而，在肝切除后，突变 ENU处理的小鼠肝脏频率(Mf)显著增加 动物。值得注意的是，单纯肝切除术并没有增加未经治疗的患者的MF。 控制动物。在正常情况下，目标单元格似乎 是正常复制的肝细胞。然而，在肝切除后，大多数 肝脏中的细胞经历1-3次细胞分裂，因此基本上 增加了累积突变风险的细胞数量。 这些数据表明，细胞增殖诱导的突变是高度 依赖于先前存在的DNA损伤的存在，因此，暗示 增殖诱导病因学中的原有DNA损伤 致癌。

The Big Blue mouse carries a transgenic integration of 30-40 copies of bacteriophage lambda each carrying a single copy of the E. coli lacI gene, which is used as a reporter for in vivo mutagenesis studies. The goal of these studies is to use the lacI gene to quantitate tissue specific genomic mutations as potential initiating events in carcinogenesis. We have continued our efforts to define the experimental and statistical methods useful for analyzing mutations in vivo. In addition, we are using the Big Blue system to assess the effects of cellular proliferation on the yield of mutations either in the presence or absence of DNA damage. The in vivo mutagenic activity of the carcinogen/noncarcinogen pair, 2,4- or 2,6-diaminotoluene correlates with the carcinogenic potential of these isomers. Cellular proliferation induced by 2,4-DAT appears to be a necessary prerequisite for generating a mutational response in the liver of Big Blue mice. We have also studied the role of proliferation induced by partial hepatectomy on the yield of mutations produced in the liver either with or without pretreatment with the potent mutagen, ENU. ENU is mutagenic in the liver in the absence of hepatectomy; however following hepatectomy, the mutant frequency (MF) was substantially increased in the livers of ENU-treated animals. Notably, hepatectomy alone did not increase the MF in untreated control animals. Under normal circumstances, the target cells appear to be the normally replicating liver cells. Upon hepatectomy, however, most cells in the liver undergo 1-3 cell divisions, thus substantially increasing the number of cells at risk for accumulating a mutation. These data suggest that cell proliferation induced mutations are highly dependent upon the presence of pre-existing DNA damage, thus, implicating pre-existing DNA damage in the etiology of proliferation-induced carcinogenesis.