Modeling Apoptotic Suppression in a Mouse Model of Brain Tumors

描述（由申请人提供）：胶质瘤，最常见的原发性脑肿瘤，仍然无法治愈。开发有效的治疗方法取决于更好地了解负责产生这些肿瘤的相关细胞程序。癌症研究中的一个新兴概念认为，增殖细胞过程的激活不足以导致肿瘤进展而不伴随细胞凋亡的抑制。本研究的主要目的是探讨抗凋亡基因在胶质瘤发生、维持和发展中的作用。 信号转导和转录激活因子（STAT）信号通路中的基因在胶质瘤中过表达，并且该通路是与胶质瘤形成相关的多个细胞程序（包括凋亡抑制）的中心枢纽。特别是STAT 3基因与胶质瘤的侵袭性间质亚型相关。我们的假设是STAT信号通路介导的凋亡抑制在胶质瘤的恶性进展中起着因果作用。我们将通过在体内表达STAT信号轴中的基因来验证这一假设，以阐明STAT通路激活对胶质瘤进展的影响。目前，大多数评估体内基因过表达的研究都是在免疫缺陷小鼠的异种移植模型中进行的，这些模型无法重现脑肿瘤的微环境。这些模型使用通过植入完全恶性细胞形成的肿瘤，而不是由正常细胞中的转化事件产生的肿瘤，因此模糊了对基因对肿瘤在其进化过程中必须克服的关键阶段的影响的分析。为了研究抗凋亡基因如何影响肿瘤的发展，我们将采用一种使用RCAS/tv-a系统的体细胞转移方法。该模型允许研究基因表达对免疫活性小鼠中从其假定的起源细胞形成内源性肿瘤的影响。重要的是，该模型可用于研究免疫抑制对胶质瘤进展的影响，因为肿瘤诱导的免疫抑制是由STAT信号传导介导的。我们的初步研究表明，STAT信号通路中的抗凋亡基因（包括Bcl-2和STAT 3）增强了肿瘤形成，降低了生存率，促进了免疫抑制性瘤内巨噬细胞，并通过诱导坏死来加速恶性进展--这是高级别胶质瘤的标志。 为了研究抗凋亡信号传导程序的影响并表征其功能，将使用RCAS/tv-a系统表达STAT信号传导轴中的基因。具体而言，我们将研究Bcl 2（特异性目的1）和STAT基因家族（特异性目的2）在肿瘤形成和进展中的作用。我们期望发现它们在胶质瘤恶性变性中的作用以及它们对肿瘤免疫抑制的促进作用。最终，我们的研究结果将有助于确定神经胶质瘤的治疗靶点，该模型将用于测试针对这种致命疾病的新疗法。

DESCRIPTION (provided by applicant): Glioma, the most common primary brain tumor, remains incurable. Developing effective treatments depends on a better understanding of relevant cellular programs responsible for generating these tumors. An emerging concept in cancer research contends that activation of proliferative cellular processes is insufficient to cause tumor progression without concomitant suppression of apoptosis. The primary objective of this research proposal is to investigate the contribution of anti-apoptotic genes on the initiation, maintenance, and progression of glioma. Genes in the Signal Transducer and Activator of Transcription (STAT) signaling pathway are overexpressed in glioma and this pathway is a central hub of multiple cellular programs relevant to gliomagenesis including apoptotic suppression. The STAT3 gene, in particular, is associated with the aggressive mesenchymal subtype of glioma. Our hypothesis is that apoptotic suppression mediated by the STAT signaling pathway plays a causal role in the inexorable malignant progression of glioma. We will test this hypothesis by expressing genes in the STAT signaling axis in vivo to elucidate the effects of STAT pathway activation on glioma progression. Currently, most research evaluating gene overexpression in vivo is performed with xenograft models in immunodeficient mice that fail to recapitulate the microenvironment of brain tumors. These models use tumors formed by the implantation of fully malignant cells, rather than arising from a transformational event in a normal cell, thus obscuring analysis of the impact of a gene on the critical stages a tumor must overcome during its evolution. To study how anti-apoptotic genes affect tumor development we will employ a method of somatic cell transfer using the RCAS/tv-a system. This model permits the study of gene expression on endogenous tumor formation from its putative cell of origin in an immunocompetent mouse. Importantly, this model can be used to study the effect of immunosuppression on glioma progression as tumor-induced immunosuppression is mediated by STAT signaling. Our preliminary studies indicate that the anti-apoptotic genes in the STAT signaling pathway (including Bcl-2 and STAT3) enhance tumor formation, decrease survival, facilitate immunosuppressive intra-tumoral macrophages, and increase malignant progression by inducing necrosis - the hallmark of high-grade glioma. To investigate the impact of anti-apoptotic signaling programs and characterize their function, genes in the STAT signaling axis will be expressed using the RCAS/tv-a system. Specifically, we will investigate the roles of the Bcl2 (Specific Aim 1) and STAT gene families (Specific Aim 2) on tumor formation and progression. We expect to discover their contribution to the malignant degeneration of glioma and their promotion of tumor- induced immunosuppression. Ultimately, our results will help define therapeutic targets for glioma and the model will be used to test novel therapeutics against this deadly disease.