P53 AND MOUSE MAMMARY TUMORIGENESIS

p53抑癌基因是人类乳腺癌中最常见的突变基因之一，包括功能获得突变和缺失突变。 到目前为止，由于p53基因缺失小鼠由于淋巴肉瘤的早期死亡率，很难研究p53基因缺失在实验性乳腺肿瘤发生中的作用。 我们已经开发了一个p53无效乳腺上皮细胞模型，通过回交原始p53无效小鼠到Balb/c小鼠。 将p53缺失的乳腺上皮细胞移植到同基因Balb/c小鼠的乳腺脂肪垫中，提供了一种独特的模型系统来检查p53基因缺失对单个组织的影响：乳腺上皮细胞形态发生和肿瘤发生。 初步数据表明，p53基因缺失的乳腺上皮细胞对肿瘤的发展高度敏感，并且肿瘤通常是非整倍体和转移性的。 在这项资助申请中，提出了三个具体的目标来研究p53基因缺失对乳腺肿瘤发生的作用。 具体目标1将通过确定肿瘤发生前病理学、激素相互作用和激素依赖性以及肿瘤发生中非整倍体的时间来检查p53缺失乳腺上皮细胞的生物学。具体目标2将使用cDNA阵列检查由于p53基因缺失而修饰的基因表达。 将在来自p53野生型和无效细胞群体的非转化（正常）和肿瘤细胞中评价基因表达。 具体目标3将使用多种方法分析具体目标2中鉴定的基因的功能特性，所述方法包括调节基因表达和恢复无效细胞中野生型p53基因活性。 待分析的初始基因是谷胱甘肽过氧化物酶，通过cDNA阵列分析，其在p53缺失乳腺细胞中被鉴定为下调。 总之，该模型允许利用移植方法分析原位乳腺中p53基因缺失的生物学、遗传学和分子后果。

The p53 tumor suppressor gene is one of the most frequently mutated genes in human breast cancer and includes gain of function mutations as well as deletion mutations. Until now, it has been difficult to examine the role of p53 gene deletion in experimental mammary tumorigenesis because of the early death rate of p53 null mice due to lymphosarcomas. We have developed a p53 null mammary epithelial model by backcrossing the original p53 null mouse into Balb/c mice. Transplantation of p53 null mammary epithelial cells into the mammary fat pads of syngeneic Balb/c mice provides a unique model system to examine the effects of p53 gene deletion on a single tissue: mammary epithelial cell morphogenesis and tumorigenesis. Preliminary data demonstrate that the p53 null mammary epithelial cells are highly susceptible to tumor development and the tumors are frequently aneuploid and metastatic. In this grant application, three specific aims are proposed to examine the role of p53 gene deletion on mammary tumorigenesis. Specific aim 1 will examine the biology of the p53-null mammary epithelial cell by determining the preneoplastic pathology, hormone interactions and hormone dependency for tumorigenesis, and the timing of aneuploidy in tumorigenesis. Specific aim 2 will examine modified gene expression due to p53 gene deletion using cDNA arrays. Gene expression will be evaluated in nontransformed (normal) and tumor cells from both p53 wild type and null cell populations. Specific aim 3 will analyze the functional properties of genes identified in specific aim 2 using a variety of approaches that include modulating gene expression and restoration of wild type p53 gene activity in null cells. The initial gene to be analyzed will be glutathione peroxidase which was identified as downregulated in p53 null mammary cells by cDNA array analysis. In summary, this model allows one to analyze the biological, genetic and molecular consequences of p53 gene deletion in the in situ mammary gland by taking advantage of transplantation methods.