EBV相关胃癌中HER2低表达的分子机制及其潜在临床意义

HER2 is an important molecular target for the treatment of gastric cancer. Our preliminary study found that there was a lower HER2 expression in Epstein-Barr virus-associated gastric carcinoma (EBVaGC) than that in Epstein-Barr virus-negative gastric carcinoma (EBVnGC). Further research also found that there was a target sequence of ebv-miR-BART16 and ebv-miR-BART9* in the 3'-UTR of HER2 mRNA, respectively; and the two ebv-miRNAs could down-regulate the activity of HER2 luciferase reporter gene. This is a new discovery of the biological significance of the ebv-miRNAs. This project intends to transfect the Epstein-Barr virus-negative gastric carcinoma cell lines SGC7901 and MKN45, in which HER2 is overexpression, with the two ebv-miRNAs mentioned above, and transfect the EBVaGC cell lines SNU719, in which HER2 is low expression, with the anti-ebv-miRNAs, so as to observe the effects of the two ebv-miRNAs on HER2 expression, HER2 downstream signal transduction (PI3K-Akt and MAPK, and PLCγ) and the biologic behavior of the gastric carcinoma cells from both positive and negative aspects. We also observe the ability of the two ebv-miRNAs in inhibiting the growth of subcutaneously implanted gastric cancer in nude mice. In addition, the expressions of the two ebv-miRNAs in the human EBVaGC tissues are detected, and the correlation between their expression and the clinicopathological features and prognosis of the patients are analyzed statistically. The aims of this project are to reveal the molecular mechanisms of low HER2 expression in EBVaGC, and to provide a scientific basis for the treatment of gastric cancer.

HER2是治疗胃癌的重要靶分子。我们前期研究发现EBVaGC中HER2蛋白表达下调，进一步研究发现ebv-miR-BART16和BART9*在HER2 mRNA 3'-UTR存在靶序列，能下调HER2荧光素酶报告基因活性。这是ebv-miRNAs生物学意义的新发现。本课题拟将上述2种ebv-miRNAs转入HER2高表达胃癌细胞株SGC7901和MKN45，将anti-ebv-miRNAs转入HER2低表达EBVaGC细胞株SNU719，正反两方面观察2种ebv-miRNAs对HER2表达、HER2下游信号转导(PI3K-Akt、MAPK及PLCγ)和胃癌细胞生物学行为的影响；观察其抑制裸鼠胃癌移植瘤生长能力；并在人EBVaGC标本中检测2种ebv-miRNAs表达，统计学分析其表达与临床病理特征和预后的关系。旨在揭示EBVaGC中HER2低表达的分子机制，为其应用于胃癌治疗提供科学依据。

在本基金资助及课题组成员共同努力下，我们在EBV相关胃癌（EBVaGC）HER2表达下调的机制及胃癌分子病理方面进行了研究，相关内容和发现如下：1. EB病毒编码的LMP2A蛋白可以通过TWIST/YB-1轴下调HER2的表达；2. 探讨EBVaGC中基因组总甲基化的情况；3. 针对EBV阳性胃淋巴上皮瘤样癌中EBV潜伏类型和基因多态性进行系统研究；4. 对EBVaGC肿瘤局部免疫进行研究，发现EBVaGC中CD8+细胞毒性T细胞和调节性T细胞（Tregs）的数量均明显增多，提示肿瘤局部存在免疫激活和免疫抑制，并探讨了CD8+T细胞增多及Tregs增多的可能机制；5. 探讨EBVaGC中PIK3CA、JAK2、PD-L1和PD-L2蛋白水平的表达情况及临床意义；6. 分离EBVaGC干细胞并鉴定其表型，探讨EBVaGC实现免疫逃逸的机制。共发表论文7篇，其中SCI论文5篇，总影响因子21.86，单篇最高影响因子6.627。以上述发现为基础，获得2项国家自然科学基金项目资助（81572309，81602146）。培养研究生12名，其中3名硕士和4名博士已毕业，目前在读博士4名，硕士1名。.已发表的SCI论文：.1. Oncotarget 2015; 6: 207-220. 2. Human pathology 2016; 53: 25-34. 3. Scientific reports 2015; 5: 18057. 4. Gastric cancer 2015; 18: 246-255. 5. Medical oncology 2015; 32: 92.