Commitment and Plasticity of Th17 cells and Tregs in the Tumor Microenvironment

描述(申请人提供)：最近发现的T辅助17(Th17)细胞和调节性T细胞(Treg)显著促进了我们对生理和病理条件下人类免疫的理解。Tregs具有广泛的免疫抑制能力，在预防自身免疫和维持免疫动态平衡中发挥核心作用，而Th17细胞在宿主抵抗微生物感染中发挥重要作用，是一系列炎症性和自身免疫性疾病的重要致病因素。然而，Treg细胞也有有害的作用，它有助于感染病原体的持续存在，并阻断有效的抗肿瘤免疫。更好地了解Th17和Treg细胞反应之间的本质和密切联系对于阐明这些细胞在不同疾病发病机制中的作用以及开发治疗和预防包括癌症和自身免疫性疾病在内的免疫相关疾病的新策略至关重要。我们最近证实，在黑色素瘤、卵巢癌、乳腺癌和结肠癌的肿瘤浸润性T细胞(TIL)中存在Th17细胞群的增加。我们进一步发现，人肿瘤浸润性Th17细胞经过多次体外T细胞受体(TCR)刺激和扩增后，可以分化为产生干扰素和FoxP3+的细胞群，具有很强的抑制活性，提示肿瘤浸润性Th17细胞具有不稳定性和可塑性。因此，研究Th17细胞和Tregs之间的承诺、可塑性和相互转化，并了解肿瘤微环境中Th17向Treg分化的分子机制至关重要。我们的长期目标是确定Th17和Tregs在抗肿瘤免疫中的作用，并开发策略来修改它们的相互作用和功能，以改善癌症治疗。这一假设的中心假设是Th17细胞具有发育可塑性，可以在肿瘤微环境中分化为具有抑制功能的Treg细胞。具体目的1旨在鉴定非肿瘤部位的Th17细胞分化为Treg的共性，然后确定参与Th17向Treg分化和转化的潜在分子机制，包括FoxP3表达的表观遗传修饰和谱系特异性转录因子和细胞因子基因的重新编程。特定目的2将在小鼠肿瘤模型中研究Th17细胞向Tregs的体内分化。我们将首先在B16黑色素瘤模型中研究肿瘤微环境是否促进Th17细胞向Tregs的转化，使用来自FoxP3EGFP转基因小鼠的FoxP3-CD4+T细胞极化的高纯度Th17细胞。然后，我们将使用OT-II和FoxP3EGFP双转基因小鼠来确定抗原刺激是否对Th17细胞在肿瘤微环境中分化为Tregs起关键作用。这些研究的积极结果应该会导致操纵Th17和Treg细胞承诺治疗人类癌症和其他疾病的新策略。

DESCRIPTION (provided by applicant): Recent discovery of T-helper 17 (Th17) cells and regulatory T cells (Treg) has markedly facilitated our understanding of human immunity under both physiological and pathological conditions. Tregs have a broad immunosuppressive capacity and play a central role in the prevention of autoimmunity and maintenance of immune homeostasis, whereas Th17 cells play an important role in host defense against microbial infections, and are important contributors to the pathogenesis of a wide array of inflammatory and autoimmune diseases. However, Treg cells also have deleterious effects by aiding the persistence of infectious pathogens and blocking effective anti-tumor immunity. A better understanding of the nature and intimate links between Th17 and Treg cell responses will be critical for the elucidation of the roles of these cells in the pathogenesis of different diseases, and for the development of novel strategies to treat and prevent immune-related diseases including cancer and autoimmune diseases. We recently demonstrated that increased Th17 cell populations exist in the tumor-infiltrating T cells (TILs) of melanoma, ovarian, breast and colon cancers. We further discovered that human tumor-infiltrating Th17 cells can differentiate into IFN-?-producing and FoxP3+ populations possessing potent suppressive activity after multiple in vitro T cell receptor (TCR) stimulations and expansions, suggesting the instability and plasticity of tumor-infiltrating Th17 cells. Therefore, it is critical to investigate the commitment, plasticity and interconversion between Th17 cells and Tregs, and understand the molecular mechanisms responsible for the Th17-to-Treg differentiation in the tumor microenvironment. Our long-term goals are to identify the role of Th17 and Tregs in anti-tumor immunity and develop strategies to modify their interactions and functions for improved cancer treatment. The central hypothesis of this proposal is that Th17 cells have developmental plasticity and can differentiate into Tregs with suppressive function in the tumor microenvironment. Specific Aim 1 seeks to identify the generality of differentiation of Th17 cells derived from non-tumor sites into Tregs, and then to identify the potential molecular mechanisms, including epigenetic modification of FoxP3 expression and reprogramming of lineage-specific transcriptional factor and cytokine genes, involved in the Th17-to-Treg differentiation and conversion. Specific Aim 2 will investigate the differentiation of Th17 cells into Tregs in vivo in mouse tumor models. We will first investigate whether tumor microenvironments promote the conversion of Th17 cells into Tregs in a B16 melanoma tumor model using highly purified Th17 cells polarized from FoxP3-CD4+ T cells derived from FoxP3EGFP transgenic mice. We will then determine whether antigen stimulation is critical for the differentiation of Th17 cells into Tregs in the tumor microenvironment using OT-II and FoxP3EGFP double transgenic mice. A positive outcome of these studies should lead to novel strategies for manipulation of Th17 and Treg cell commitment for the treatment of human cancer and other diseases as well.