HIN-1,A Novel Putative Breast Tumor Suppressor Gene

描述(由申请人提供)：乳腺癌发生的分子遗传学变化尚未明确，而此类事件的识别是乳腺癌研究的一个主要焦点。为了确定这些变化，我们使用SAGE(基因表达系列分析)比较了正常乳腺上皮细胞、原位(DCIS导管原位癌)、浸润性乳腺癌和转移性乳腺癌的基因表达谱。通过对这些SAGE文库的配对比较，我们发现了一个新的基因HIN-1(High in Normal-1)，它只存在于正常的乳房腔上皮细胞中。随后，我们发现HIN-1在95%的人类乳腺癌标本中表达显着下调，包括早期乳腺癌，如导管和小叶原位癌。在大多数乳腺癌细胞系(95%)和原发肿瘤(70%)中，HIN-L的表达被甲基化抑制。根据预测的氨基酸序列，Hin-1似乎是一种新的分泌型蛋白质，与已知的蛋白质没有同源性。在正常和癌变的乳腺上皮细胞中存在一种假定的高亲和力HIN-1受体，提示其作用机制为自分泌。将HIN-1重新导入乳腺癌细胞似乎抑制了细胞的生长，并且HIN-1的表达仅限于终末分化的上皮细胞。基于这些最近发表的初步数据，我们假设HIN-1是一种乳腺癌抑制基因，是一种自分泌的上皮生长因子。目前的建议旨在进一步鉴定HIN-L基因的功能。这项建议的具体目的是(1)检验HIN-L是调节乳腺细胞生长、形态发生和存活的自分泌因子的假设；(2)分析HIN-1在发育中的和成人正常乳腺组织和乳腺癌组织中的体内表达；(3)检验HIN-1在小鼠乳腺发育中所必需的假说，以及HIN-1的缺失足以使小鼠乳腺肿瘤发生。BIN-1的功能特征及其参与的信号通路不仅有助于我们进一步了解乳腺发育和肿瘤发生的分子基础，而且还将为未来的翻译研究提供新的有价值的靶点。

DESCRIPTION (provided by applicant): Molecular genetic changes that underlie the initiation of breast cancer are poorly defined, and the identification of such events is a major focus of breast cancer research. In order to identify these changes we compared the gene expression profiles of normal mammary epithelial cells, and in situ (DCIS ductal carcinoma in-situ), invasive and metastatic breast carcinomas using SAGE (Serial Analysis of Gene Expression). Through the pair-wise comparison of these SAGE libraries, we have identified a novel gene HIN-1 (High In Normal-1) that is present only in normal luminal mammary epithelial cells. Subsequently we have shown that HIN-1 expression is significantly down regulated in 95% of human breast carcinoma specimens including early stage breast carcinomas such as ductal and lobular carcinoma in-situ. The expression of HIN-l is silenced by methylation in the majority of breast cancer cell lines (>95%) and primary tumors (>70%). HIN-1 appears to be a novel secreted protein with no homology to known proteins based on predicted amino acid sequence. A putative high affinity HIN-1 receptor is present in normal and cancerous mammary epithelial cells suggesting an autocrine mechanism of action. Reintroduction of HIN-1 into breast cancer cells appears to inhibit cell growth and the expression of HIN-1 is restricted to terminally differentiated epithelial cells. Based on these recently published and preliminary data, we hypothesize that HIN-1 is a breast tumor suppressor gene that is an autocrine epithelial growth factor. The current proposal is aimed at the further characterization of the function of the HIN-l gene. The specific aims of this proposal are (1) to test the hypothesis that HIN-l is an autocrine factor that regulates mammary cell growth, morphogenesis, and survival, (2) to analyze the in vivo expression of HIN-1 in developing and adult normal and cancerous breast tissue, and (3) to test the hypotheses that HIN-1 is required for mouse mammary gland development and loss of HIN-1 is sufficient for mouse mammary tumorigenesis. The functional characterization of BIN-1 and the signaling pathways in which it is involved will not only further our understanding of the molecular basis of mammary development and tumorigenesis, but will also provide new and valuable targets for future translational research.