Role of NKG2D in immune responses to turmors

描述（由申请人提供）：NKG2D刺激受体，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细胞的裂解敏感。我们的中心假设是NKG2D（部分）作为宿主肿瘤监测装置，使NK细胞和T细胞能够消除因致癌应激而上调NKG2D配体的非常早期的肿瘤细胞。为了解决这一假设的关键方面，我们产生了NKG2D -/-小鼠。先前资助期的研究表明，Nkg2d-/-小鼠对高侵袭性、早期前列腺癌的免疫监视功能受损，对致癌物甲基蒽诱导的纤维肉瘤的免疫监视功能受损。我们建议在此研究NKG2Ds在癌症免疫监测中的几个关键机制问题。特异性目标1将解决NK细胞和/或T细胞在体内癌症模型中是否介导nkg2d介导的监测。我们将使用基因研究将NKG2D敲除小鼠与缺乏NK细胞和/或T细胞的小鼠结合起来，以确定NKG2D的监测主要是由NK细胞、T细胞还是两者共同介导的。特异性目标2将探讨NKG2D在体内特异性抗肿瘤反应中特异性作用于CD8 T细胞的作用。由于围绕NKG2D在增强CD8 T细胞对肿瘤反应中的作用存在争议，我们将在过继转移/肿瘤攻击模型中使用来自NKG2D敲除或野生型小鼠的TCR转基因T细胞，以解决CD8 T细胞表达的NKG2D是否增强了初始增殖和功能反应、记忆细胞的形成、记忆阶段功能的维持和对肿瘤的排斥能力。特异性Aim 3将确定nkg2d依赖性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，这种上调是由作为肿瘤发生的最早障碍的途径引起的。至关重要的是要确定监测是在如此早期阶段进行，还是在较晚阶段进行。为了解决NKG2D依赖性监视在肿瘤起始的最早阶段或更晚阶段起作用的建议，我们将研究野生型或NKG2D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浸润分析作为确定监视发生阶段及其与配体表达和免疫细胞浸润的关系的方法。这一系列全面的实验将明确测试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，这些研究的结论将对NKG2Ds的作用提供基本的理解。

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.