ROLE OF A NEW PROTO-ONCOGENE,INT-5,IN BREAST NEOPLASIA

乳腺癌是人类癌症中最棘手的类型之一。 的 乳腺癌的病因学涉及遗传， 荷尔蒙和饮食因素。 试图获得一个清晰的理解 这些因子如何参与乳腺肿瘤发生的研究受到阻碍， 部分原因是缺乏关于特定遗传病变的信息， 有助于肿瘤发展的起始和/或演变。 我们 最近的研究已经鉴定和克隆了int-5基因组DNA， 一种独特且高度保守的新型小鼠乳腺肿瘤病毒（MMTV） BALB/c癌前病变D2增生的整合基因 肺泡结节（HAN）。 Int-5与其他int基因不同：它已经被 在癌前病变中发现，而不是癌性肿瘤;已经发现 在化学诱导的肿瘤中，而不是在病毒诱导的肿瘤中; 包括乳腺在内的各种正常组织中。 Int-5也是 不同于与乳腺癌有关的其它癌基因（c-myc， c-Ha-ras、c-erbB和HER-2/neu），因为其可能在早期乳腺癌中发挥作用。 癌前病变 int-5在乳腺癌和乳腺癌中的过度表达 在肿瘤和乳腺癌细胞系中的研究表明， 乳腺癌发生 因此，int-5基因是一个很好的候选基因， 研究这种基因在乳腺癌中的作用。 我们的目标是 直接检测int-5基因的转化能力， 使用体外细胞培养和体内转基因在乳腺癌中的作用 动物模型 我们的具体目标是：1）克隆小鼠和人类 使用小鼠基因组探针对int-5 cDNA进行测序，并通过 确定它们的核苷酸序列; 2）确定核苷酸序列 int-5基因组克隆的结构组成; 用MMTV-int-5表达载体对int-5基因的转化能力 细胞培养和转基因动物模型系统;转化正常人 将MMTV-int-5融合基因转染乳腺上皮细胞（MCF-10）， 在转化细胞中该基因的过度表达是否导致肿瘤 在裸鼠中形成。 同时，我们将培育int-5转基因动物， 在乳腺发育的不同阶段检查这些动物 和妊娠/哺乳对HAN形成的影响及其进展， 乳腺肿瘤，以及检查任何乳腺癌的发病率增加， 这些动物中的癌症; 4）确定int-5的预后意义 通过分析原发性乳腺肿瘤的int-5过度表达来过度表达 并将这些数据与其他临床因素进行比较。 这些研究将 提供基本知识，帮助理解 int-5基因及其编码的蛋白质，以及 int-5基因及其在乳腺癌中作用 转基因动物还提供 一个研究乳腺癌发病率的模型， 可以通过各种干预措施降低发病率，并研究 其他癌基因的协同效应，如果有的话，在激活这一点， 基因在乳腺肿瘤中的作用。

Breast cancer is one of the most problematic types of human cancer. The etiology of breast cancer involves a complex interplay of genetic, hormonal, and dietary factors. Attempts to gain a clear understanding of how these factors participate in mammary tumorigenesis have been hampered, in part, by a lack of information on the specific genetic lesions that contribute to the initiation and/or evolution of tumor development. Our recent studies have resulted in identifying and cloning int-5 genomic DNA, a unique and highly conserved novel mouse mammary tumor virus (MMTV) integration locus gene from the BALB/c precancerous D2 hyperplastic alveolar nodule(HAN). Int-5 is different from other int genes: it has been found in precancerous, rather than cancerous neoplasms; it has been found in chemically-, rather than virus-induced neoplasms; and it is expressed in a variety of normal tissues, including the mammary gland. Int-5 is also different from other oncogenes implicated in breast cancer (c-myc, c-Ha-ras, c-erbB and HER-2/neu) because of its possible role in early preneoplastic changes. Overexpression of int-5 in mammary and breast tumors and also in breast cancer cell lines suggests its involvement in mammary carcinogenesis. Therefore, int-5 gene is a good candidate for investigating the role of this gene in mammary cancer. Our objective is to test the transforming ability of int-5 gene directly to establish its role in breast cancer using in vitro cell culture and in vivo transgenic animal models. Our specific aims are: We will 1) clone mouse and human int-5 cDNAs using mouse genomic probe and characterize these clones by determining their nucleotide sequence; 2) determine the nucleotide sequence and structural organization of int-5 genomic clone; 3) establish the transforming ability of int-5 gene using MMTV-int-5 expression vector in cell culture and transgenic animal model systems; transform normal human breast epithelial cells (MCF-10) with MMTV-int-5 fusion gene and examine whether overexpression of this gene in transformed cells leads to tumor formation in nude mice. Also, we will generate int-5 transgenic animals, examine these animals during different stages of mammary gland development and pregnancy/lactation for formation of HAN and their progression to mammary tumors, as well as examine any increased incidence of mammary cancer in these animals; 4) establish the prognostic significance of int-5 overexpression by analyzing primary breast tumors for int-5 overexpression and comparing these data with other clinical factors. These studies will provide basic knowledge and help in understanding the characteristics of int-5 gene and its encoded protein, as well as the transforming ability of int-5 gene and its role in breast cancer. Transgenic animals also provide a model to study the incidence of breast cancer, to determine how this incidence can be reduced by various interventions, and to study the synergistic effect of other oncogenes, if any, in the activation of this gene in mammary neoplasms.