EpCAM介导弥漫大B细胞淋巴瘤免疫逃逸的机制研究

Epithelial cell adhesion molecule(EpCAM,) a tumor-associated antigen, related to immune escape in many cancers, but its underlying mechanism remains almost unknown. Our previous study has demonstrated that EpCAM was significantly high expression with a strong positive correlation with Th2 cells while negative correlation with Th1 cells in the patients with refractory recurrent diffuse large B cell lymphoma (DLBCL). Furthermore, ectopic expression of EpCAM in DLBCL promoted the secretion of Th2-related cytokines and activation of STAT6 in CD4+T cells. Thus，we here propose that EpCAM contributes to immune escape by modulating a shift from Th1 to Th2. In this project, we first confirmed that EpCAM promotes the differentiation of CD4+T cells into Th2 in both in vitro and in vivo study. Then, the Th2 immunodeficiency mice were established to demonstrate that EpCAM promotes Th2 production and induces tumor immune escape. The molecular mechanism will be explored through transcriptome analysis and other methods. Finally, we evaluate the value of EpCAM as the clinical therapeutic target and prognostic index for DLBCL in both mouse model and clinical cases. We expect that these proposed studies would provide a new insight into the mechanism for immune escape as well as a potential therapeutic target and novel prognostic indictor for DLBCL.

肿瘤相关抗原EpCAM与肿瘤免疫逃逸相关，但机制不明。课题组前期采用全基因组表达谱分析发现，难治复发性弥漫大B细胞淋巴瘤（DLBCL）患者明显高表达EpCAM，且与患者Th1比例负相关及Th2比例正相关。进一步研究发现肿瘤高表达EpCAM促进CD4+T细胞分泌Th2细胞因子及STAT6激活。课题组据此推测:EpCAM介导Th1/Th2向Th2偏倚导致肿瘤免疫逃逸。本课题首先干扰EpCAM表达，体内外证实EpCAM促进CD4+T细胞向Th2分化。其次，建立Th2免疫缺陷小鼠阐明EpCAM诱导Th2形成导致肿瘤免疫逃逸，并通过转录组分析等方法寻找并验证其分子机制。最后，通过小鼠模型及临床病例评估EpCAM作为DLBCL的临床治疗靶标和预后指标价值。从临床、动物、细胞、分子水平为EpCAM作为DLBCL免疫治疗靶点及预后指标提供理论依据。

弥漫大B细胞淋巴瘤（DLBCL）存在免疫逃逸，是疾病难治复发原因之一，但机制不明。首先我们发现难治复发弥漫大B细胞淋巴瘤患者Th2比例升高及Th1比例降低，并采用全基因组表达谱分析发现难治复发性DLBCL患者明显高表达EpCAM，且与患者Th1比例负相关及Th2比例正相关。对临床数据分析发现EpCAM高表达具有病变累及广泛及预后差的特点，生存分析提示高表达EpCAM往往具有更短的生存时间；对高表达EpCAM的弥漫大B细胞淋巴瘤患者的外周血CD4+T检测发现Th2相关的转录因子GATA3表达上调，Th1相关的转录因子T-bet表达下调，进一步检测Th细胞相关细胞因子分泌发现高表达EpCAM的DLBCL诱导Th2相关的细胞因子IL-4、IL-6分泌明显升高，而与Th1相关的细胞因子IFNγ、IL-2分泌明显降低，表明DLBCL高表达EpCAM可以诱导CD4+T细胞倾向于向Th2分化;最后，通过建立EpCAM高表达淋巴瘤细胞模型及小鼠模型，体内外试验发现EpCAM抗体AE7对淋巴瘤细胞无明显杀伤作用，但可以逆转淋巴瘤对化疗药DNR的耐药，可以延长小鼠生存时间，机制发现AE7通过下调Ras通路逆转细胞耐药。