The Role of NC2 in Gene Repression by Tumor Hypoxia

描述（由申请人提供）：在几项临床研究中，肿瘤缺氧已被证明是治疗结果不良的预后指标。这些发现与治疗方式无关，手术治疗的缺氧肿瘤与放射治疗的肿瘤一样差。小鼠遗传模型和VHL缺陷型肿瘤患者表明，转录因子HIF-1诱导基因响应缺氧的能力可能在肿瘤发生中起刺激作用。然而，缺氧也是一种有效的基因表达抑制剂，但很少有研究探讨缺氧依赖性基因下调的机制。我们提出的假设是，基因阻遏缺氧可以有助于tmornigenesis，和NC 2（负辅因子2）分子是负责至少有一些这种抑制。NC 2 α/β（Dr 1/DRAP）最初被表征为能够在体外抑制转录的生物化学活性。我们有初步的证据表明，抑制活性诱导缺氧细胞，缺氧细胞提取物未能转录（至少）在体外的一些模板。这种活性的生物化学表征表明，NC 2可能是一个一般的缺氧转录阻遏物。通过低氧诱导的NC 2然后可以通过低氧抑制的靶基因如肿瘤抑制因子血小板反应蛋白1和2（TSP 1/TSP 2）、凋亡抑制因子stathmin和存活素以及肿瘤标志物α胎儿蛋白（AFP）的下调来促进肿瘤形成。因此，我们建议建立一个遗传系统的分析NC 2的作用，在肿瘤的发展。我们将通过三个具体目标来实现这一目标，首先确定NC 2负责体内特定靶启动子的低氧抑制，其次进行NC 2 α和NC 2 β的结构-功能关系以鉴定对低氧基因抑制至关重要的结构域，第三构建具有受损NC 2活性的肿瘤细胞系，其原则上测试证明低氧基因抑制在模型肿瘤形成中是重要的。这些研究将确定通过NC 2活性的低氧基因抑制是否可能成为未来治疗人类癌症的分子疗法的潜在治疗靶点。

DESCRIPTION (provided by applicant): Tumor hypoxia has been shown in several clinical studies to be a prognostic indicator of poor treatment outcome. These findings have been independent of therapeutic modality, with hypoxie tumors that are treated surgically doing equally as poorly as those treated with radiation therapy. Genetic models in mice, and patients with VHL-deficient tumors, have suggested that the ability to induce genes in response to hypoxia with the transcription factor HIF-1 may play a stimulatory role in tumorigenesis. Hypoxia, however, is also a potent repressor of gene expression, but few studies have investigated the mechanism of hypoxia-dependent gene downregulation. We present the hypothesis that gene repression by hypoxia can contribute to tmnorigenesis, and the NC2 (negative co-factor 2) molecules are responsible for at least some of this repression. NC2alpha/beta (Drl/DRAP) was originally characterized as a biochemical activity that was able to repress transcription in vitro. We have preliminary evidence that repressive activity is induced in hypoxic cells, and extracts from hypoxic cells fail to transcribe (at least) some templates in vitro. Biochemical characterization of this activity suggests that NC2 may be a general repressor of transcription in hypoxia. NC2 induction by hypoxia could then contribute to tumor formation through the downregulation of such hypoxia-repressed target genes as tumor suppressors thrombospondin 1 and 2 (TSP1/TSP2), apoptotic inhibitors stathmin and survivin, and tumor marker alpha fetal protein (AFP). We therefore propose to establish a genetic system for the analysis of NC2's role in tumor development. We will address this goal with three specific aims, first establish that NC2 is responsible for hypoxic repression of specific target promoters in vivo, second perform structure-function relationship of NC2alpha and NC2beta to identify domains that are critical for hypoxic gene repression, and third construct tumor cell lines with compromised NC2 activity that test proof in principle that hypoxic gene repression is important in model tumor formation. These studies will determine if hypoxic gene repression through NC2 activity could be a potential therapeutic target for future molecular therapeutics in the treatment of human cancers.