Cytokine modulated model growth inhibitory mechanisms

描述（由申请人提供）：细胞因子通过诱导肿瘤中生长抑制基因的表达或通过建立针对它们的免疫应答来调节体内肿瘤细胞生长。干扰素家族的细胞因子调节几种生理反应，如抗病毒，抗肿瘤和免疫功能。通过与其他细胞因子相互作用，IFN成为一个庞大的细胞间信号网络的组成部分，促进体内抗肿瘤和抗病原体监视系统。在早期的研究中，我们证明了干扰素诱导的抗肿瘤作用，特别是细胞凋亡，可以协同增强全反式维甲酸（RA）。这种维生素A代谢物本身在许多实验和临床模型中作为生长抑制剂。一些临床研究也证明了IFN/RA的有效的肿瘤抑制作用。我们假设IFN/RA采用新的基因产物来抑制肿瘤生长。为了鉴定参与IFN/RA诱导的细胞凋亡的关键分子，我们使用遗传策略并鉴定了与类维生素A干扰素诱导的死亡率（GRIM）相关的几个基因。一种这样的新基因产物GRIM-19通过凋亡抑制生长。我们和其他人的前期研究表明，它的活性受到DNA、病毒、癌蛋白和某些细胞蛋白的抑制。这些观察结果表明其有效的抗癌特性。在上一个资助期间，我们已经证明GRIM-19与信号转导和转录激活因子3（STAT 3）结合，并使用细胞系模型抑制其促生长作用。STAT 3是一种休眠的腺嘌呤调节的转录因子，在许多人类肿瘤中被致癌信号组成性激活。STAT 3活性在正常细胞中由反馈抑制剂调节。持续的STAT 3活性通过刺激参与这些反应的各种细胞基因的表达来促进肿瘤细胞的存活、增殖、转移。虽然STAT 3的致癌激活是一个重要步骤，但我们认为其抑制剂的丢失或失活也可能在促进肿瘤生长之前在此过程中发挥关键作用。在初步研究中，我们使用异种移植模型显示GRIM-19抑制组成型STAT 3诱导的肿瘤生长和转移。与这些一致，我们观察到在几种原发性人类肿瘤中GRIM-19的表达丧失和突变，这与STAT 3诱导基因的强烈上调和细胞生长的促进相关。在这次更新申请中，我们将使用基因敲除和转基因小鼠研究GRIM-19与体内肿瘤生长的生物学相关性。我们将使用体外和体内模型研究grim 19突变（在原发性肿瘤中发现）对癌基因诱导的肿瘤生长促进的影响。虽然STAT 3的失调在许多肿瘤中是已知的，但其失调的分子机制，特别是其抑制剂在肿瘤发展中的作用研究很少。本申请中提出的研究将定义GRIM-19中的肿瘤特异性功能障碍如何影响这种新的生长调节途径的功能。

DESCRIPTION (provided by applicant): Cytokines regulate neoplastic cell growth in vivo either by inducing the expression of growth suppressor genes in tumors or by mounting an immune response against them. The interferon family of cytokines regulates several physiologic responses such as antiviral, antitumor, and immune functions. By interacting with other cytokines, IFNs become an integral part of a large of intercellular signaling network that promotes anti-tumor and anti-pathogen surveillance system in vivo. In an earlier study, we demonstrated that the IFN-induced anti-tumor actions, especially apoptosis, could be synergistically augmented by all-trans retinoic acid (RA). This vitamin-A metabolite by itself acts as a growth inhibitor in many experimental and clinical models. Some clinical studies also demonstrated the potent tumor inhibitory effects of IFN/RA. We hypothesized that IFN/RA employs novel gene products for suppressing tumor growth. To identify the critical molecules involved in IFN/RA-induced apoptosis, we have used a genetic strategy and identified several Genes associated with Retinoid-Interferon-induced Mortality (GRIM). One such novel gene product, GRIM-19, suppresses growth via apoptosis. Previous studies by us and others showed that its activity suppressed by DNA viral oncoproteins and some cellular proteins. These observations indicate its potent anti-oncogenic characteristics. During the last funding period we have shown that GRIM-19 binds to Signal Transducer and Activator of Transcription 3 (STAT3) and suppresses its growth promoting action using cell line models. STAT3, a dormant cytokine-regulated transcription factor, is constitutively activated in a number of human tumors by oncogenic signals. STAT3 activity is regulated in normal cells by feedback inhibitors. Persistent STAT3 activity promotes survival, proliferation, metastasis of tumor cells by stimulating the expression of various cellular genes involved in those responses. Although oncogenic activation of STAT3 is an important step, we suggest that loss or inactivation of its inhibitors may also play a critical step in this process prior to the promotion of tumor growth. In preliminary studies, we showed that GRIM-19 suppress constitutive STAT3- induced tumor growth and metastasis using xenograft models. Consistent with these, we observed a loss of expression and mutations in GRIM-19 in several primary human tumors, which correlated with a strong upregulation of STAT3-inducible genes and promotion of cell growth. In this renewal application, we will investigate the biological relevance of GRIM-19 to tumor growth in vivo using knockout and transgenic mice. We will investigate the impact of grim19 mutations (found in primary tumors) on oncogene-induced tumor growth promotion using in vitro and in vivo models. Although a deregulation of STAT3 is known in many tumors, the molecular mechanisms of its deregulation, specifically the role of its inhibitors in tumor development are poorly studied. The studies proposed in this application will define how tumor- specific dysfunctions in GRIM-19 affect the functioning of this new growth regulatory pathway.