Targeting MCPyV to Overcome Immune Evasion in Merkel Cell Carcinoma

描述(由申请人提供)：本申请是针对NCI的特殊机会：利用RC-2“重大机会”机制开发艾滋病相关恶性肿瘤疫苗的探索性研究，RFA-0D-09-004。默克尔细胞癌(MCC)是一种罕见的侵袭性神经内分泌皮肤癌，每年困扰大约1500名美国人。与恶性黑色素瘤相比，MCC的致命性是前者的两倍以上。此外，MCC对健康的影响越来越大，因为其报告的发病率在过去20年中增加了两倍多。在流行病学研究中，微囊癌的发生与T细胞免疫功能障碍密切相关。事实上，在包括HIV、实体器官移植接受者和慢性淋巴细胞白血病患者在内的临床公认的T细胞功能障碍患者中，MCC的发病率增加了10到30倍。重要的是，在免疫抑制的患者中，当免疫功能恢复时，MCC有时会退化，这表明基于免疫的治疗可能对这种癌症有效。最近，一种新的人类多瘤病毒(Merkel cell PolyomaVirus，MCPyV)被发现，并似乎与大约80%的MCC的发病有关。重要的是，病毒蛋白在晚期和转移性MCC肿瘤中表达。我们的初步数据表明，这些病毒蛋白通常能够刺激MCC患者和对照组的体液和细胞免疫反应。此外，我们已经确定了MCC肿瘤用于逃避这些免疫反应的几种机制。MCPyV的生物学和免疫学特征为理解MCC的发病机制、预后标志物和治疗提供了希望。我们建议利用国家癌症研究所为“艾滋病相关恶性肿瘤疫苗的开发”提供的特殊机会来促进这一领域的重大进展。具体地说，我们将通过利用我们的三项关键资产来研究基于理性免疫的治疗这种疾病的潜力：独一无二的完整和不断扩大的MCC临床和组织资源集，成熟的免疫学专家合作者，以及我们对这种癌症如何逃避免疫系统的最新见解。尽管T细胞功能在控制这种癌症方面很重要，但MCC采用的免疫逃避策略仍然缺乏特征性。我们的初步数据显示，这些肿瘤经常下调MHC I类分子，典型的T细胞稀少浸润，并大量表达与自然杀伤(NK)细胞抑制相关的microRNAs。此外，T细胞和NK细胞侵入MCC肿瘤的证据在临床上和统计学上与提高22例测试集和35例MCC患者的独立验证集的存活率显著相关。我们将测试以下假设：在MCC中新发现的免疫逃避机制与生存相关，以及默克尔多瘤病毒靶向免疫疗法在这种HIV相关恶性肿瘤的合理治疗中很有希望。我们提出三个目标来描述MCC采取的免疫逃避策略，并开始开发合理的疫苗或过继免疫疗法的过程。目的1：明确两个大型独立MCC队列中T和NK细胞逃避的机制和预后意义。目的2：明确正常人和MCC患者对Merkel多瘤病毒的细胞免疫应答。目的：建立MCPyV特异性T细胞并检测其对表达Merkel多瘤病毒蛋白的APC的杀伤作用。这些目标在建议的期间是可行的，因为我们有广泛的初步数据、建立的MCC资源和我们的专家免疫学合作者。提高对相关免疫逃逸机制的了解并开发克服这些机制的方法将对MCC的预后和治疗产生快速影响，并可能为其他癌症的预后和治疗策略提供洞察。 公共卫生相关性：默克尔细胞癌(MCC)是一种与艾滋病毒相关的皮肤癌，其致命性是黑色素瘤的两倍，与一种新的人类多瘤病毒MCPyV密切相关。与免疫学专家合作，我们将使用我们来自数百名患者的临床注释血液和组织存储库来扩展我们的初步数据，这些数据表明MCC正在使用免疫逃避机制的广泛证据。具体地说，我们将定义对MCPyV的细胞免疫反应的性质，作为开发合理的、基于免疫的策略治疗这种癌症的关键初始步骤。

DESCRIPTION (provided by applicant): This application is responsive to the NCI specific opportunity: Exploratory Research in the Development of Vaccines for AIDS-associated Malignancies using the RC-2 "Grand Opportunities" mechanism, RFA-0D- 09-004. Merkel Cell Carcinoma (MCC) is an uncommon, aggressive neuroendocrine skin cancer that afflicts approximately 1,500 Americans each year. MCC is more than twice as likely to be lethal when compared to malignant melanoma. Furthermore, MCC has an increasing health impact as its reported incidence has more than tripled in the past 20 years. MCC incidence is strongly associated with T cell immune dysfunction in epidemiologic studies. Indeed, MCC incidence is 10- to 30-fold increased in people with clinically recognized T cell dysfunction including HIV, solid organ transplant recipients, and chronic lymphocytic leukemia patients. Importantly, in immune suppressed patients, MCC sometimes regresses when immune function is restored suggesting immune- based therapies may be effective in this cancer. Recently, a new human polyomavirus (Merkel cell polyomavirus, MCPyV) was discovered and appears to be involved in the pathogenesis of approximately 80% of MCCs. Importantly viral proteins are expressed in advanced and metastatic MCC tumors. Our preliminary data demonstrate that these viral proteins are typically capable of stimulating both humoral and cellular immune responses in MCC patients and controls. Furthermore, we have identified several mechanisms that MCC tumors use to escape from these immune responses. Characterizing MCPyV biology and immunology offers hope of substantial progress in understanding the pathogenesis, prognostic markers, and treatment of MCC. We propose to take advantage of the special opportunity provided by the NCI's support for "Development of vaccines for AIDS-associated malignancies" to catalyze significant progress in this field. Specifically, we will investigate the potential of rational immune- based therapy for this disease by capitalizing on three of our key assets: a uniquely complete and expanding set of MCC clinical and tissue resources, established expert immunology collaborators, and our recent insights into how this cancer evades the immune system. Despite the importance of T cell function in controlling this cancer, the immune evasion strategies employed by MCC remain poorly characterized. Our preliminary data show that these tumors often down- regulate MHC class I, typically have a sparse infiltrate of T cells, and abundantly express microRNAs associated with natural killer (NK) cell inhibition. Moreover, evidence of T- and NK-cell invasion into MCC tumors was strikingly clinically and statistically associated with improved survival in a test set of 22 cases and in an independent validation set of 35 MCC patients. We will test the hypotheses that immune evasion mechanisms newly identified in MCC are associated with survival and that Merkel polyomavirus-targeted immune therapy is promising in the rational treatment of this HIV-associated malignancy. We propose three Aims to characterize the immune evasion strategies adopted by MCC and begin the process of developing rational vaccine or adoptive immunotherapy for this disease. Aim 1: Define the mechanisms and prognostic significance of T and NK cell evasion in two large independent MCC cohorts. Aim 2: Define the cellular immune response against the Merkel polyomavirus in normal individuals and MCC patients. Aim 3: Generate MCPyV-specific T cells and measure killing of APC expressing Merkel polyomavirus proteins. These aims are feasible during the proposed period because of our extensive preliminary data, established MCC resources and our expert immunologic collaborators. An improved understanding of the relevant immune evasion mechanisms and developing the means to overcome them would have a rapid impact on prognosis and therapy of MCC as well as potentially offer insight on prognosis and treatment strategies for other cancers. PUBLIC HEALTH RELEVANCE: Merkel Cell Carcinoma (MCC) is an HIV-associated skin cancer that is twice as lethal as melanoma and strongly associated with a new human polyomavirus, MCPyV. Working with expert immunology collaborators, we will use our repository of clinically annotated blood and tissues from several hundred patients to expand on our preliminary data suggesting extensive evidence of immune evasion mechanisms in use by MCC. Specifically, we will define the nature of the cellular immune response to MCPyV as a key initial step toward developing rational, immune-based strategies to treat this cancer.