HIN-1,A Novel Putative Breast Tumor Suppressor Gene

描述（由申请人提供）：乳腺癌起始的分子遗传变化定义不清，这些事件的识别是乳腺癌研究的主要焦点。为了确定这些变化，我们使用SAGE（基因表达序列分析）比较了正常乳腺上皮细胞、原位（DCIS导管原位癌）、浸润性和转移性乳腺癌的基因表达谱。通过对这些SAGE文库的两两比较，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腺腔上皮细胞中。随后，我们发现HIN-1的表达在95%的人类乳腺癌标本中显著下调，包括早期乳腺癌，如原位导管癌和小叶癌。在大多数乳腺癌细胞系（>95%）和原发性肿瘤细胞系（>70%）中，hin - 1的表达被甲基化沉默。根据预测的氨基酸序列，HIN-1似乎是一种与已知蛋白无同源性的新型分泌蛋白。一种推测的高亲和力的HIN-1受体存在于正常和癌性乳腺上皮细胞中，表明其作用机制是自分泌的。将HIN-1重新导入乳腺癌细胞似乎可以抑制细胞生长，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和初步的数据，我们假设HIN-1是一种乳腺肿瘤抑制基因，是一种自分泌上皮生长因子。目前的建议是旨在进一步表征hin - 1基因的功能。本课题的具体目的是：(1)验证HIN-1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在发育和成年正常及癌性乳腺组织中的体内表达情况；(3)验证小鼠乳腺发育需要HIN-1，小鼠乳腺肿瘤发生需要HIN-1缺失的假设。BIN-1的功能表征及其参与的信号通路不仅将进一步加深我们对乳腺发育和肿瘤发生的分子基础的理解，而且还将为未来的转化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.