Notch-1 in T Cells: a central mediator of tumor induced anergy

描述(申请人提供)：髓系来源的抑制细胞(MDSC)通过一个或多个过程损害荷瘤宿主的T细胞功能，包括氨基酸精氨酸和半胱氨酸的耗尽，活性氧物种和一氧化氮的释放，以及调节性T细胞的诱导。然而，T细胞与MDSC接触后功能障碍的分子机制尚不清楚。Notch同源1易位相关蛋白(Notch-1)是促进急性淋巴细胞T细胞白血病发生的重要信号转导分子。然而，它对正常T细胞反应的影响却知之甚少。这项拟议的研究将首次确定T淋巴细胞Notch-1抑制在MDSC诱导的实体瘤T细胞抑制中的意义。此外，通过使用新的抗原特异性转基因小鼠模型，这项研究将促进对Notch-1在正常T细胞增殖、细胞毒性和细胞因子产生中作用的理解。在初步研究中，表达精氨酸酶I的肿瘤浸润性MDSC以与阻止T细胞增殖相同的比例抑制激活的T细胞中Notch-1的表达。此外，激活的T细胞 经Notch-1裂解抑制剂处理后，细胞增殖下降，干扰素-γ产生减少。这些结果在Notch-1条件性基因敲除小鼠的细胞中得到了证实，在这些小鼠中，激活的T细胞的增殖也减少了。初步数据表明，Notch-1在正常T细胞功能中起着重要作用，并且a T细胞-Notch-1表达降低可能是MDSC抑制肿瘤T细胞的机制之一。因此，我们假设实体瘤中诱导的MDSC抑制了T细胞中Notch-1的表达，从而损害了保护性抗肿瘤T细胞反应的发展。这项研究的完成有望为MDSC在癌症中抑制T细胞提供机制方面的见解。这项研究还可能使设计新的治疗方法来逆转癌症或其他疾病(如自身免疫性疾病、慢性感染和创伤)中的T细胞耐受，这些疾病的特征是MDSC的积累。为了验证我们的假设和实现本项目的目标，我们提出了以下具体目标：具体目标1：验证精氨酸酶I表达的MDSC通过抑制Notch-1的表达而在体外抑制T细胞功能的预测。特异性目的2：在体内确定Notch-1在肿瘤浸润性MDSC诱导的T细胞抑制中的作用。

DESCRIPTION (provided by applicant): Myeloid-derived suppressor cells (MDSC) impair T cell function in tumor-bearing hosts through one or more processes, including the depletion of the amino acids arginine and cysteine, the release of reactive oxygen species and nitric oxide, and the induction of regulatory T cells. However, the molecular mechanisms by which T cells become dysfunctional after contact with MDSC remain unclear. Notch homolog 1-translocation-related protein (Notch-1) has been determined to be an important signal transduction molecule in the promotion of acute lymphoblastic T cell leukemia. However, its influence on normal T cell responses is poorly understood. The proposed study will be the first to determine the significance of the inhibition of Notch-1 in T lymphocytes in the MDSC-induced T cell suppression occurring in solid tumors. Further, through the use of novel antigen- specific transgenic murine models, this investigation will advance the understanding of the role of Notch-1 in normal T cell proliferation, cytotoxicity, and cytokine production. In preliminary studies, tumor-infiltrating MDSC expressing arginase I inhibited the expression of Notch-1 in activated T cells at the same ratios at which they blocked T cell proliferation. In addition, activated T cells cultured with inhibitors of Notch-1 cleavage displayed decreased cell proliferation and impaired production of interferon gamma (IFN?). These results were confirmed in cells from Notch-1 conditional knockout mice, in which proliferation of activated T cells also decreased. The preliminary data suggest that Notch-1 plays a significant role in normal T cell function and that a decrease in T cell-Notch-1 expression is a possible mechanism for the MDSC-induced T cell inhibition in tumors. Thus, we hypothesize that MDSC induced in solid tumors inhibit the expression of Notch-1 in T cells and thereby impair the development of a protective anti-tumor T cell response. The completion of this research is expected to provide mechanistic insights into the suppression of T cells by MDSC in cancer. This study may also enable the design of new therapeutic approaches to reverse T cell tolerance in cancer or other conditions such as autoimmune diseases, chronic infections, and trauma, which are characterized by the accumulation of MDSC. To test our hypothesis and to achieve the objectives of this project, we propose the following Specific Aims: Specific Aim 1: Test the prediction that arginase I-expressing MDSC inhibit T cell function in vitro by impairing the expression of Notch-1. Specific Aim 2: Determine in vivo the role of Notch-1 in the T cell suppression induced by tumor-infiltrating MDSC.