Role of TIEG1 in Foxp3+Treg development and tumor progression

描述(申请人提供)：翻译科学：癌症作为一种系统性疾病(15-CA-115)：虽然肿瘤疫苗可以诱导针对肿瘤抗原的CD4辅助细胞和CD8细胞毒性反应，但它们在临床上在导致肿瘤消退方面基本上无效。这是因为肿瘤细胞获得了许多逃避宿主免疫监视程序的机制。Foxp3+CD4+CD25+Treg介导的免疫抑制已成为肿瘤免疫逃逸的重要机制之一，也是肿瘤免疫治疗成功的主要障碍。大多数恶性肿瘤细胞，包括前列腺癌细胞，都会分泌大量的转化生长因子β，并已被证明通过诱导Foxp3的表达，将效应T细胞转化为肿瘤抗原特异性Tregs。这种肿瘤诱导的Tregs不仅抑制了抗肿瘤效应细胞的启动和效应功能，而且形成了一个广泛的自我放大的免疫抑制网络。因此，克服肿瘤诱导的Tregs的扩增和从头产生对于设计有效的免疫治疗策略以成功地治疗癌症至关重要。我们已经证明了转化生长因子-β诱导的早期基因-1(TIEG1)在转化生长因子-β处理的CD4T细胞中对Foxp3的转录调控中起着关键作用。E3连接酶Itch介导的单泛素化是TIEG1的核转位和转录激活所必需的。然而，在瞬时过表达系统中，Itch针对TIEG1进行单泛素化和多泛素化。我们的初步研究表明，抑制转化生长因子β诱导的Foxp3表达的IL-6可能通过多泛素化诱导TIEG1蛋白酶体降解。TYK2介导的TIEG1的磷酸化似乎是TIEG1多泛素化的识别信号。因此，我们假设，当CD4T细胞受到转化生长因子-β或IL-6刺激时，Itch针对TIEG1的单一泛素化和多泛素化不同，并调节其激活和降解。尽管关于Foxp3在Treg发育和功能中的作用的数据越来越多，但Foxp3的转录是如何调控的还不清楚。我们已经在Foxp3启动子上发现了一致的NFAT和TIEG1结合位点。由于大多数转录因子与其他紧密结合的因子协同工作，我们假设NFAT和TIEG1在Foxp3启动子上相互作用，调节染色质重塑和Foxp3表达。清楚地了解CD4T细胞中影响Foxp3转录的分子组合和相互作用将有助于设计策略来破坏肿瘤微环境中Tregs的抑制网络。以分泌大量转化生长因子-β的前列腺癌TRAMP-C2细胞为研究对象，分析TIEG1缺陷对Treg发生和肿瘤进展的影响。由于TIEG1不影响胸腺中nTreg的发育，靶向TIEG1是阻止Tregs从头诱导的一个有吸引力的策略。这样的策略有望消除最有效的肿瘤特异性Tregs，这些Tregs抑制抗肿瘤免疫反应，而不会触发自身免疫的风险。 公共卫生相关性：该申请是对恢复法挑战拨款的回应；研究领域：翻译科学专题；(15-CA-115)，癌症作为一种系统性疾病。这一创新应用提出了研究转化生长因子-β诱导的早期基因-1(TIEG1)在肿瘤细胞分泌的转化生长因子-β诱导Foxp3+Tregs过程中的作用。从这些研究中获得的结果有望获得重大的新见解，以最大限度地利用当前的免疫治疗方法。此外，它还符合挑战补助金的精神，因为它将需要雇用新员工，特别是在全国失业率最高的密歇根州底特律。

DESCRIPTION (provided by applicant): Translational Science: Cancer as a systemic disease (15-CA-115): Although tumor vaccines can induce CD4 helper and CD8 cytotoxic response against tumor antigens, they have been largely ineffective in causing tumor regression in the clinic. This is because the tumor cells acquire many mechanisms to evade the immune surveillance program of the host. Foxp3+CD4+CD25+Treg-mediated immune suppression has emerged as one of the crucial tumor immune evasion mechanisms and main obstacle of successful tumor immunotherapy. Most malignant cells including prostate cancer cells secret large amounts of TGF-¿ and has been shown to convert the effector T cells into tumor antigen specific Tregs by inducing Foxp3 expression. Such tumor induced Tregs not only suppress the priming and effector function of anti-tumor effector cells but also form a broad network of self-amplifying immunosuppressive network. Therefore, overcoming tumor induced expansion and de novo generation of Tregs is critically important for the design of effective immunotherapeutic strategies for successful cancer treatment. We have demonstrated a critical role of TGF-¿ inducible early gene-1 (TIEG1) in the transcriptional regulation of Foxp3 in CD4T cells treated with TGF-¿. E3 ligase Itch-mediated monoubiquitination is essential for nuclear translocation, and transcriptional activation of TIEG1. However, in transient overexpression systems Itch targets TIEG1 for both mono and polyubiquitination. Our preliminary studies suggest that IL-6 which inhibits TGF-¿ induced Foxp3 expression induces proteasomal degradation of TIEG1 possibly through polyubiquitination. Tyk2-mediated phosphorylation of TIEG1 seems to act as a recognition signal for polyubiquitination of TIEG1. Therefore, we hypothesize that Itch targets TIEG1 differentially for mono and polyubiquitination when the CD4T cells are stimulated with TGF-¿ or IL-6 and regulates its activation and degradation. Despite the growing body of data on the role of Foxp3 in Treg development and function, how Foxp3 transcription is regulated is not clear. We have identified consensus NFAT and TIEG1 binding sites adjacent to each other on Foxp3 promoter. Since, most transcription factors work cooperatively with other factors binding in close proximity we hypothesize that NFAT and TIEG1 interact on Foxp3 promoter and regulate chromatin remodeling and Foxp3 expression. A clear understanding of molecular combinations and cross-talks that imprint Foxp3 transcription in CD4T cells will aid in designing strategies to disrupt the inhibitory network of Tregs in tumor microenvironment. Using prostate cancer TRAMP-C2 cells which secrete large amount of TGF-¿, we will analyze the effect of TIEG1 deficiency on Treg development and tumor progression. Since TIEG1 does not effect nTreg development in the thymus, targeting TIEG1 is an appealing strategy to block the de novo induction of Tregs. Such a strategy is expected to eliminate most potent tumor specific Tregs that inhibit anti-tumor immune response without the risk of triggering autoimmunity. PUBLIC HEALTH RELEVANCE: The application is in response to the Recovery Act Challenge Grant; Research Area: Translational Science Topic; (15-CA-115), Cancer as a systemic disease. This innovative application proposes to study the role of TGF-¿ inducible early gene-1(TIEG1) in the induction of Foxp3+Tregs by TGF-¿ secreted from tumor cells. The results obtained from these studies are expected gain significant new insights to maximize current immunotherapeutic approaches. In addition it complies with the spirit of the Challenge Grant as it will necessitate the hiring of new employees, especially in Detroit, Michigan which suffers from the highest unemployment rate in the country.