SAFB1 /2 Factors as Noval Breast Tumor Suppressor Genes

描述(由申请人提供)：我们最近鉴定并鉴定了两个支架附着因子SAFB1和SAFB2，它们显示75%的同源性，并在染色体19p13上(以头对头的方向)映射在一起。我们已经发现SAFBs在乳腺癌细胞中起着生长抑制的作用，并且它们在染色体19p13上的位置显示出在临床乳腺癌中报告的最高杂合性丢失之一(78%)。在大约20%的乳腺癌中，SAFB1/2的蛋白表达缺失，低表达与总生存期缩短有关。我们在乳腺肿瘤中发现了SAFB1突变，这些突变在邻近的正常组织中不存在。因此，我们假设SAFB1和SAFB2是肿瘤抑制基因，其在乳腺肿瘤中的频繁失活导致肿瘤发生和转移的表型，我们将使用体内和体外模型进行评估。虽然这两种蛋白都是生长抑制因子和内质网共抑制因子，但它们也有不同的性质-两者都存在于细胞核中，但在应激条件下只有SAFB1被招募到核体中，只有SAFB2也出现在细胞质中，并与vinexin-beta结合。因此，我们将评估哪些SAFB功能是肿瘤抑制所必需的，哪些功能是SAFB1和SAFB2之间的相加、协同、补偿或拮抗功能。具体地说，我们会问：1)SAFB1/2在人类乳腺肿瘤中是如何失活的？我们将研究乳腺癌进化过程中的丢失，并确定失活是否通过突变和/或其他表观遗传事件发生，例如基因间双向SAFB1/2启动子的超甲基化。2)体外和体内中和SAFB1的生物学效应是什么？我们将比较和对比(通过RNAi)降低SAFB1和SAFB2的效果，临床乳腺癌标本中发现的SAFB突变，以及小鼠模型中基因敲除(SAFB1-/-和SAFB2-/-)的效果。3)SAFB1和SAFB2水平与乳腺癌的临床预后有何关系？我们将在一个排列的乳腺肿瘤库中测量SAFB1和SAFB2的水平，并将这些水平与生存和其他已知的预后因素相关联。这项结合了分子、细胞和体内遗传学方法的研究的成功完成，将为人类乳腺癌严重干扰的调控机制提供重要的见解。

DESCRIPTION (provided by applicant): We have recently identified and characterized two scaffold attachment factors termed SAFB1 and SAFB2, which show 75 percent homology and map together (in head-to-head orientation) on chromosome 19p13. We have discovered that the SAFBs function as growth inhibitors in breast cancer cells, and that their locus on chromosome 19p13 displays one of the highest losses of heterozygosity (78 percent) reported in clinical breast cancer. Protein expression of SAFB1/2 is lost in approximately 20 percent of breast cancers, and low expression is associated with a shorter overall survival. We have found SAFB1 mutations in breast tumors that are not present in adjacent normal tissue. Therefore, we hypothesize that SAFB1 and SAFB2 are tumor suppressors whose frequent inactivation in breast tumors results in tumorigenic and metastatic phenotypes, which we will assess using in vivo and in vitro models. While both proteins function as growth inhibitors and ER co-repressors, they also have distinct properties - both are found in the cell nucleus, but only SAFB1 is recruited to nuclear bodies under stress conditions, and only SAFB2 also appears in the cytoplasm and binds vinexin-beta. We will therefore assess which SAFB functions are essential for tumor suppression, and which functions are additive, synergistic, compensatory, or antagonistic between SAFB1 and SAFB2. Specifically, we will ask: 1) How are SAFB1/2 inactivated in human breast tumors? We will investigate loss during breast cancer evolution, and determine whether inactivation occurs through mutations and/or other epigenetic events such as hypermethylation of the intergenic bidirectional SAFB1/2 promoter. 2) What are the biological effects of neutralizing SAFB1 in vitro and in vivo? We will compare and contrast the effects of lowering (by RNAi) SAFB1 and SAFB2, of SAFB mutants identified in clinical breast cancer specimens, and of gene knockouts in mouse models (SAFB1-/- and SAFB2-/-). 3) How do SAFB1 and SAFB2 levels correlate with clinical breast cancer outcome? We will measure SAFB1 and SAFB2 levels in an arrayed breast tumor bank, and correlate the levels with survival and other known prognostic factors. Successful completion of this study, which incorporates molecular, cellular, and in vivo genetic approaches, will provide important insight into regulatory mechanisms which are critically disturbed in human breast cancer.