Merkel cell polyomavirus T antigens in tumorigenesis

默克尔细胞多瘤病毒 T 抗原在肿瘤发生中的作用

• 批准号: 8833939
• 负责人: ANDRZEJ A. DLUGOSZ
• 金额: $ 35.52万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8833939
• 关键词: Adult; Animal Model; Animals; Antigen Targeting; Antigens; Apoptosis; Automobile Driving; Binding; Biological; Brain Neoplasms; C-terminal; Cancer Etiology; Carcinoma in Situ; Cell Culture Techniques; Cell Maintenance; Cells; Complex; Cultured Cells; DNA Damage; Data; Development; Distant Metastasis; Embryo; Employee Strikes; Epidermis; Epithelial; Epithelium; Fibroblasts; Gene Expression Profile; Genetically Engineered Mouse; Growth; Human; Human Papillomavirus; Hyperplasia; In Situ; In Vitro; Individual; Infection; Knowledge; Large T Antigen; Lead; Length; Lesion; Light; Link; Maintenance; Malignant Neoplasms; Malignant neoplasm of cervix uteri; Merkel Cells; Merkel cell carcinoma; Modeling; Mus; Mutagenesis; Mutation; Neoplastic Cell Transformation; Neuroendocrine Tumors; Neurosecretory Systems; Oncogene Proteins; Oncogenes; Oncogenic; Patients; Phenotype; Play; Polyomavirus; Polyomavirus Transforming Antigens; Population; Preclinical Testing; Process; Proliferating; Property; Protein Phosphatase 2A Regulatory Subunit PR53; Proteins; RB1 gene; Reporting; Role; SKP Cullin F-Box Protein Ligases; Series; Signal Pathway; Simian virus 40; Skin; Skin Cancer; Skin Neoplasms; Small T Antigen; Squamous cell carcinoma; Staging; Survival Rate; Testing; Transgenic Mice; Transgenic Organisms; Tumor Suppressor Proteins; Viral; Viral Proteins; Viral Tumor Antigens; Virus; Work; Xenograft procedure; advanced disease; base; cancer type; cell transformation; cellular targeting; effective therapy; in vivo; insight; keratinocyte; knock-down; mouse model; neoplastic; neoplastic cell; new therapeutic target; novel; oral cavity epithelium; outcome forecast; overexpression; postnatal; preclinical study; progenitor; public health relevance; research study; response; targeted treatment; tool; tumor; tumorigenesis; ubiquitin-protein ligase; virus development

DESCRIPTION (provided by applicant): Merkel cell polyomavirus T antigens and neoplastic transformation in vivo Project Summary Merkel cell carcinoma (MCC) is a rare neuroendocrine skin tumor with a poor prognosis at advanced disease stages due to the unavailability of effective treatments. Most MCCs carry sequences from a novel polyomavirus, Merkel cell polyomavirus (MCPyV), and express two putative oncoproteins: MCPyV small T antigen (sTAg) and tumor-specific truncated large T antigen (tLTAg). Like other viral oncoproteins, MCPyV transforming antigens are predicted to interact with multiple cellular proteins including tumor suppressors: tLTAg targets RB1 while sTAg targets the PP2A complex. At least some knock-down studies in cultured cells and xenografts support a requirement for tLTAg and sTAg antigens in MCC tumor cell maintenance. In addition, overexpression studies in cultured fibroblasts point to stAg as the predominant transforming oncogene which, surprisingly, operates in a PP2A-independent manner. In contrast, sTAg-driven fibroblast transformation is strictly dependent on a recently-described domain that binds the Fbxw7 component of the SCF E3 ubiquitin ligase complex and leads to accumulation of LTAg and several cellular oncoproteins that are Fbxw7 substrates. These reports have provided valuable insight into the transforming potential of sTAg in cultured fibroblasts, but studies assessing whether MCPyV TAgs can function as oncogenic drivers in vivo have not yet been reported. In preliminary studies we show that MCPyV sTAg, but neither tLTAg nor full-length LTAg, is a potent transforming oncogene in skin and oral epithelia of transgenic mice, leading to striking hyperplasia, impaired terminal differentiation, a DNA damage response, and apoptosis. We propose a series of experiments to further study the in vivo transformation potential of individual MCPyV TAgs, and to test their functional interaction when co-expressed in inducible mouse models. To investigate the MCC tumor cell of origin, we will compare MCPyV TAg transforming potential when targeted to 1) proliferating versus differentiating cellular compartments of epidermis, and 2) Merkel cell progenitors versus differentiated Merkel cells. We will also isolate defined cell populations from conditional MCPyV TAg transgenic mice and study their response to TAg expression in cell culture, enabling functional studies aimed at defining mechanisms of transformation which can then be verified in vivo. The proposed studies are highly significant since they will help fill a critical gap in our knowledge by defining the biological activity of MCPyV TAgs in intact animals, providing a much-needed set of tools for studying factors contributing to the development and maintenance of MCPyV-associated cancer. In addition, these studies will help identify MCPyV TAg cellular targets whose deregulation via non-viral mechanisms may drive the development of virus-negative MCC, and may contribute more generally to the development of other types of cancer. Finally, the proposed work is likely to have direct translational relevance to MCC patients, as it may lead to the identification of new therapeutic targets and yield much-needed mouse models for functional studies and preclinical trials.

项目概述默克尔细胞癌（Merkel cell carcinoma， MCC）是一种罕见的神经内分泌皮肤肿瘤，由于缺乏有效的治疗方法，在疾病晚期预后较差。大多数mcc携带一种新型多瘤病毒，默克尔细胞多瘤病毒（MCPyV）的序列，并表达两种推定的癌蛋白：MCPyV小T抗原（sTAg）和肿瘤特异性截断大T抗原（tLTAg）。与其他病毒癌蛋白一样，预计MCPyV转化抗原可与多种细胞蛋白相互作用，包括肿瘤抑制因子：tLTAg靶向RB1，而sTAg靶向PP2A复合物。至少在培养细胞和异种移植物中进行的一些敲除研究支持在MCC肿瘤细胞维持中需要tLTAg和sTAg抗原。此外，在培养成纤维细胞中的过表达研究指出stAg是主要的转化癌基因，令人惊讶的是，它以不依赖pp2a的方式起作用。相反，stag驱动的成纤维细胞转化严格依赖于最近描述的一个结构域，该结构域结合SCF E3泛素连接酶复合物的Fbxw7组分，并导致LTAg和几种作为Fbxw7底物的细胞癌蛋白的积累。这些报道为培养成纤维细胞中sTAg的转化潜力提供了有价值的见解，但是评估MCPyV标签是否可以作为体内致癌驱动因素的研究尚未报道。在初步研究中，我们发现MCPyV sTAg，而不是tLTAg或全长LTAg，在转基因小鼠的皮肤和口腔上皮中是一种有效的转化癌基因，导致显著的增生、终端分化受损、DNA损伤反应和细胞凋亡。我们提出了一系列的实验来进一步研究个体的体内转化潜力