基于遗传易感性构建鼻咽癌基因工程小鼠模型

Nasopharyngeal carcinoma (NPC) is a unique type of head and neck cancer that arises from the epithelium of the nasopharynx. NPC exhibits a striking geographic and ethnic distribution, the incidence of NPC is unusually high in Southeast Asia and southern China, but rare worldwide. The exact genetic changes attributable for the pathogenesis of NPC are still elusive, as a result the genetically engineered mouse models (GEMM) that mimicking spontaneous NPC are currently unavailable. Multiple factors, including genetic susceptibility, Epstein-Barr virus (EBV) infection and environmental factors contribute to NPC development. EBV has been proposed as a driving factor in NPC pathogenesis, however, transgenic mouse models carrying EBV oncogenes do not develop tumors, indicating that viral infection may not contribute to NPC initiation. Besides the presence of EBV, familiar aggregation of NPC and the occurrence of multiple cases of the disease in first-degree relatives have been reported in endemic regions, strongly indicating that genetic susceptibility is a major determinant of NPC. Based on the discoveries from our previous NPC genome-wide association study (GWAS), we focused on a NPC susceptibility gene TNFRSF19, which is highly expressed in NPC and is required for cell proliferation and NPC development. By studying TNFRSF19, we gained insights into the functional mechanisms responsible for increased susceptibility to NPC. The preliminary results indicate that despite the distinct aberrant genes between NPC and head and neck cancer, they share common aberrant signaling pathway that driving tumorigenesis. The applicant aims to generate Tnfrsf19 transgenic mouse model to prove the causal role of genetic susceptibility in NPC pathogenesis.

鼻咽癌是起源于鼻咽上皮的一种特殊类型的头颈癌。鼻咽癌具有显著的地域和人种特征，主要在我国华南和东南亚国家高发。鼻咽癌的确切病因尚未完全阐明，相应的自发性鼻咽癌动物模型也一直没有建立起来。鼻咽癌的发生一般被认为是多因素联合作用的结果，包括遗传易感、EB病毒感染和环境因素。EB病毒曾被认为是鼻咽癌的致病因子，然而EB病毒癌基因的转基因小鼠并不能模拟鼻咽癌的发生。除了EB病毒感染，家族聚集性是鼻咽癌的一大特征，提示遗传易感性可能是鼻咽癌的首要病因。申请人利用团队前期的全基因组关联分析（GWAS）结果，重点解析了一个在鼻咽癌中获得性高表达的易感基因TNFRSF19的体内功能，阐明了其分子机制。前期数据显示，尽管鼻咽癌和它的近亲头颈癌拥有不同的基因异常，但在导致的信号通路紊乱上具有很大的相似之处。申请人将建立鼻咽癌易感基因TNFRSF19的转基因小鼠模型，验证遗传易感性和这一罕见肿瘤的因果关系。

鼻咽癌是高发于亚洲尤其是我国的地域性肿瘤。鼻咽癌的确切病因尚未完全阐明，一般被认为是多因素联合作用的结果，包括遗传易感、EB病毒感染和环境因素。本项目旨在揭示东亚人群独有的遗传多样性与鼻咽癌易感性之间的联系。现代人类群体全基因组扫描分析发现东亚人群发生独有的基因突变EDAR V370A，90%以上现代中国人携带这一基因突变，以往研究认为该基因突变与毛囊和汗腺发育相关，但这些表型难以解释该基因突变的强选择优势。前期结果证实EDAR高表达于免疫系统。通过构建EDAR V370A基因敲入小鼠模型，发现EDAR V370A点突变小鼠幼稚CD4 T细胞和B细胞增殖能力显著强于野生型小鼠，并促进幼稚CD4 T细胞分化为Th17。体内结果显示，EDAR V370A加剧脂多糖诱导的炎症反应，并且在抗真菌感染中具有明显的保护作用。以上结果提示在免疫系统的平衡选择压力下，东亚人群独有的EDAR V370A基因突变促进前炎症反应和保护真菌感染，同时可能引起东亚人群对部分慢性感染疾病相比其他种群更加易感。本项目成功建立了模拟东亚基因型的EDAR V370A的小鼠模型，证实该gain-of-function突变赋予东亚人群更强的细胞免疫，为今后我国病原微生物感染提供了免疫系统东亚人源化小鼠模型，也有助于理解这一显性突变在东亚人群中流行至今的原因。项目执行期内发表SCI论文一篇，申请专利一项，负责人于2019年获得国自然优秀青年基金的资助。