EB病毒相关胃癌肿瘤浸润CD8+T淋巴细胞增多的分子机制

Epstein-Barr virus (EBV) is a herpes virus which is associated with a number of different cancers such as Burkitt’s lymphoma, Hodgkin lymphoma, nasopharyngeal carcinoma (NPC) and gastric carcinoma. As is known, EBV-encoded RNAs (EBERs) can be detected by in situ hybridization (ISH) in about 1.3-18% of gastric carcinomas, which are defined as Epstein-Barr virus associated gastric carcinomas (EBVaGCs). EBVaGC is known to be accompanied by massive lymphocytes. Our studies showed that the tumor infiltrating lymphocytes (TILs) mainly consisted of CD3+CD8+T cells in EBVaGCs. Forward study showed firstly that the apoptosis index (AI) of TILs in EBVaGC was lower than that in Epstein-Barr virus negative gastric carcinomas (EBVnGCs). In this study, the chemokines established as key regulators of immune cells trafficking in EBVaGC are analyzed by using a human chemokine antibody array. The chemokines may also protect CD8+T cells from apoptosis in EBVaGC. Apoptosis is induced by the receptor-mediated and/or mitochondria-mediated pathways. Both of these pathways are involved in inducing the onset of spontaneous apoptosis of circulating T cells observed in patients with malignant disease. Here, the potential involvement of the chemokines in inhibition of CD8+T cells apoptosis in EBVaGC and the expression of proapoptotic molecules, Fas and Bax, and antiapoptotic molecules, Bcl-2, in CD8+T cells in EBVaGC are investigated. The strong association of EBV infection with EBVaGC raised a possibility that EBV may promote lymphocytic infiltration in tumor site by inducing the chemokines. EBNA1、EBERs and LMP2A induce the expression the chemokines in EBVaGC requires further examination. In this study, we isolate and compare EBVaGC without EBNA1、EBERs and LMP2A expression, examining the roles of EBNA1、EBERs and LMP2A in the chemokines induction. The expression dynamics of the chemokines and its clinicopathological/prognostic significance in EBVaGC are also investigated. These findings will corroborate the accumulation mechanism of CD8+T cells and precise role of EBV in EBVaGC.

EB病毒（EBV）为自然界广泛存在的疱疹病毒科DNA致瘤病毒，与人类多种淋巴系统肿瘤、鼻咽癌及部分胃癌的发生密切相关。这部分与EBV感染密切相关的胃癌称为EB病毒相关胃癌（EBVaGC）。EBVaGC癌组织中有明显的淋巴细胞浸润倾向。我们前期研究发现在人EBVaGC中肿瘤浸润CD3+CD8+T细胞明显增多，并且凋亡减少。本课题拟在前期研究基础上通过趋化因子抗体芯片筛查EBVaGC独特表达的趋化因子并从趋化及抗凋亡两方面观察该趋化因子对CD8+T细胞的作用；通过流式细胞术的方法观察在EBVaGC中CD8+T细胞抗凋亡的信号通路；通过RNAi的方法观察EBVaGC中EBV潜伏基因表达产物对趋化因子表达的影响；并在人EBVaGC标本中，观察趋化因子表达的差异与临床病理特征和预后的关系。旨在阐明EBVaGC CD8+T细胞增多的分子机制，揭示EBV感染在胃癌中的意义，为胃癌的治疗提供科学依据。

EBV与多种肿瘤如淋巴瘤、鼻咽癌的发生发展密切相关。在胃癌中，约1.3-18%的胃癌与EBV感染密切相关，我们把这部分胃癌称为EB病毒相关胃癌（EBVaGC）。EBVaGC具有独特的肿瘤微环境，显著表现为肿瘤间质中大量淋巴细胞浸润。相关文献表明这些浸润的淋巴细胞主要为具有增殖活性的CD8+T细胞，但其机制及对肿瘤微环境的影响尚不清楚。据此，本课题通过检测EBVaGC肿瘤浸润淋巴CD3、CD8的表达，明确EBVaGC肿瘤浸润淋巴细胞以CD3+CD8+T细胞为主；进一步通过趋化因子抗体芯片及中和抗体阻断，明确EBVaGC中CCL21-CCR7轴对肿瘤浸润CD3+CD8+T细胞的抗凋亡作用及相关机制。