Role of NKG2D in immune responses to turmors

描述(申请人提供)：NKG2D刺激性受体，由NK细胞、CD8+和其他T细胞表达，识别正常细胞低表达和各种肿瘤细胞上调的自身配体。肿瘤细胞表达NKG2D配体使细胞对NK细胞和某些情况下的T细胞的裂解反应敏感。我们的中心假设是NKG2D(部分)作为宿主肿瘤监视装置，使NK细胞和T细胞能够消除由于致癌压力而上调NKG2D配体的非常早期的肿瘤细胞。上一次资助期的研究表明，Nkg2d-/-小鼠在TraMP癌基因转基因小鼠中对一种高度侵袭性的、早期出现的前列腺癌的免疫监测以及对致癌物甲基菲诱发的纤维肉瘤的监测都受到了损害。我们建议研究NKG2DS在癌症免疫监测中的几个关键机制问题。具体目标1将解决NK细胞和/或T细胞是否在体内癌症模型中介导NKG2D介导的监视。我们将使用结合NKG2D基因敲除小鼠和缺乏NK细胞和/或T细胞的小鼠的遗传学研究来确定NKG2D监视主要是由NK细胞、T细胞还是两者共同介导。具体目标2将阐述NKG2D在体内特异性抗肿瘤反应中对CD8T细胞的作用。由于围绕NKG2D在增强CD8T细胞对肿瘤的反应中的作用存在争议，我们将在过继转移/肿瘤挑战模型中使用来自NKG2D基因敲除或野生型小鼠的已定义的TCR转基因T细胞，以研究CD8T细胞表达的NKG2D是否增强了最初的增殖和功能反应、记忆细胞的形成、记忆阶段的功能维持和排斥肿瘤的能力。具体目标3将确定NKG2D依赖的肿瘤监测是否发生在肿瘤起始阶段。我们的中心假设是，NKG2D监测是NKG2D配体上调的结果，而NKG2D配体上调是肿瘤发生的最早障碍。关键是要确定监测是在这么早的阶段发生，还是在以后发生。为了解决依赖NKG2D的监测在肿瘤启动的最早阶段或更晚的阶段起作用的建议，我们将研究野生型或NKG2D基因敲除小鼠的定时队列中的肿瘤形成，使用NKG2D配体表达模式、组织病理学分析和免疫渗透分析作为确定监测发生的阶段及其与配体表达和免疫细胞渗透的关系的方法。这一全面的系列实验将最终测试NKG2D在NK细胞和T细胞中的作用，它们之间的相互作用，NKG2D对CD8 T细胞反应的影响，以及NKG2D是否作用于早期或癌前细胞，而不是更晚期的肿瘤。毫无疑问，这些研究的结论将从根本上理解NKG2DS的作用。 公共卫生相关性这项研究解决了免疫反应如何攻击癌细胞。我们正在测试一种假设，即免疫细胞表面一种名为NKG2D的特定受体蛋白使这些细胞能够攻击和杀死癌细胞。初步结果显示，由于突变而缺乏这种蛋白质的动物患癌症的几率更高。然而，一些癌细胞通过这种识别系统逃脱了识别。我们的结果将有助于指导帮助我们的免疫系统攻击癌症的治疗剂的设计。

DESCRIPTION (provided by applicant): The NKG2D stimulatory receptor, expressed by NK cells, CD8+, and other T cells, recognizes self ligands that are poorly expressed by normal cells and upregulated by various tumor cells. Expression of NKG2D ligands by tumor cells sensitizes the cells to lysis by NK cells and in some cases T cells. Our central hypothesis is that NKG2D serves (in part) as a host tumor surveillance apparatus that enables NK cells and T cells to eliminate very early stage tumor cells that upregulate NKG2D ligands as a result of oncogenic stress To address key aspects of this hypothesis, we have generated Nkg2d-/- mice. Studies in the previous funding period demonstrated that Nkg2d-/- mice are impaired in immune surveillance of a highly aggressive, early- arising form of prostate adenocarcinoma in the TRAMP oncogene-transgenic mice, and in surveillance of fibrosarcomas induced by the carcinogen methylcolanthrene. We propose here to investigate several key mechanistic issues of NKG2Ds role in cancer immune-surveillance. Specific Aim 1 will address whether NK cells and/or T cells mediate NKG2D-mediated surveillance in cancer models in vivo. We will use genetic studies combining NKG2D knockout mice with mice deficient for NK cells and/or T cells to determine whether NKG2D surveillance is primarily mediated by NK cells, T cells, or both. Specific Aim 2 will address the role of NKG2D specifically on CD8 T cells in specific antitumor responses in vivo. Because of controversy surrounding the role of NKG2D in enhancing CD8 T cell responses to tumors, we will use defined TCR transgenic T cells from NKG2D knockout or wildtype mice in an adoptive transfer/tumor challenge model, in order to address whether NKG2D expressed by CD8 T cells enhances initial proliferative and functional responses, formation of memory cells, maintenance of functionality in the memory stage and capacity to reject tumors. Specific Aim 3 will determine whether NKG2D-dependent surveillance of TRAMP tumors occurs at the stage of tumor initiation. Our central hypothesis is that NKG2D surveillance is a consequence of NKG2D ligand upregulation resulting from pathways that serve as the earliest barriers to tumorigenesis. It is critical to determine whether surveillance occurs at such an early stage, or later. To address the proposal that NKG2D-dependent surveillance acts at the earliest stages of tumor initiation, or later, we will investigate tumor formation in timed cohorts of wildtype or NKG2D knockout mice, using NKG2D ligand expression patterns, histopathology analysis, and analysis of immune infiltrates as methods to pinpoint the stage at which surveillance occurs and its relation to ligand expression and immune cell infiltration. This comprehensive series of experiments will definitively test the role of NKG2D in NK cells and T cells, their interactions, the influence of NKG2D on CD8 T cell responses, and whether NKG2D acts on early or precancerous cells as opposed to more advanced tumors. There is no doubt that the conclusions of these studies will provide fundamental understanding of NKG2Ds role. PUBLIC HEALTH RELEVANCE This research addresses how the immune response attacks cancer cells. We are testing the hypothesis that a specific receptor protein called NKG2D on the surface of immune cells enables these cells to attack and kill cancer cells. The preliminary results show that animals that lack the protein due to a mutation have a higher incidence of cancer. Yet some cancer cells escape recognition by this recognition system. The results of our results will help to guide the design of therapeutic agents that help our immune systems attack cancer.