Chemerin抑制肝癌及调控肝癌炎症微环境的机制研究

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors, and its development is closely associated with inflammation. The inflammatory microenvironment of HCC consists of various immune cells, non-hematopoietic stromal cells as well as many inflammatory mediators. During the progression of HCC, various immunesuppressive factors antagonize the anti-tumor immunity, promoting the tumor growth. Thus, the clarification of the underlying immunoregulatory mechanism of HCC could facilitate the development of the new immunotherapeutic strategy for HCC. Chemerin is a newly identified inflammation-related protein. Recent studies from other groups and us have demonstrated that chemerin has a complex role in regulating tissue inflammation. Our preliminary data showed that chemerin is highly expressed in normal liver but greatly down-regulated in the tumor tissue of HCC patients. Moreover, we found that chemerin was able to inhibit tumor growth in the mouse model of HCC. We proposed that chemerin has anti-tumor effects on HCC, which could be due to its ability of regulating the inflammatory microenvironment of HCC. This project aims to study the regulatory effects of chemerin on the inflammatory microenvironment of HCC by using several mouse models of HCC and the analysis of samples from HCC patients, identify the target cells and target molecules that are critically mediated the anti-tumor effects of chemerin, clarify the specific cell signaling molecule pathway that chemerin directly regulates, and finally provide the potential new therapeutic target for the immunotherapy of HCC.

肝癌是最常见的恶性肿瘤之一，其发生发展与炎症密切相关。肝癌炎症微环境由多种免疫细胞、非血源性间质细胞、以及多种炎性介质组成。肝癌进展过程中，免疫抑制因素占据优势，削弱抗肿瘤免疫。因此，深入探讨肝癌的免疫调节机制，有助于开发肝癌的免疫治疗新策略。Chemerin是一个新发现的炎症相关蛋白，文献报道和我们的研究揭示chemein通过多种机制调节炎症。我们的前期实验发现正常肝脏高表达chemerin，而肝癌患者瘤组织的chemerin表达水平明显下调，而且，chemerin可显著抑制小鼠肝癌。我们假设chemerin通过调控肝癌炎症微环境，发挥抑癌效应。本课题计划利用多种小鼠肝癌模型，结合临床样本分析，研究chemerin对肝癌炎症微环境的调控机制，鉴定介导chemerin抑癌效应的关键靶细胞和靶分子，阐明chemerin直接调节的细胞信号分子通路，为肝癌免疫治疗提供潜在新靶点。

肝癌是最常见的恶性肿瘤之一，其发生发展与炎症密切相关。肝癌炎症微环境由肿瘤细胞、基质细胞和多种炎性介质组成。已有报道髓样来源抑制细胞（MDSC)可介导促肿瘤炎症，参与免疫抑制和血管新生，促进肝癌的发生发展。Chemerin是一种炎症相关蛋白，根据炎症类型的不同，发挥促炎或抑炎效应。肝细胞是chemerin的主要来源，但chemerin在肝癌进展中的作用还所知甚少。我们分析肝癌患者样品发现相比正常对照，肝癌患者外周血和肿瘤局部chemerin蛋白水平显著下降，且与患者的不良预后密切相关。我们利用缺失chemerin的Rarres2-/-小鼠和肝脏原位接种Hepa1-6肝癌细胞进行体内机制研究，发现Rarres2-/-小鼠的肝原位肿瘤变大，出现肺转移，而Hepa1-6细胞过表达chemerin则抑制肿瘤生长。Chemerin缺失或过表达导致肿瘤局部的MDSC增加或减少，并伴随着抗肿瘤T细胞应答和血管新生的改变，而不影响NK细胞在肝癌组织的浸润。在T细胞缺陷的RAG1-/-小鼠肝脏接种过表达chemerin的Hepa1-6细胞仍然可以部分抑制肿瘤大小，提示chemerin的抑癌效应具有T细胞依赖和非T细胞依赖两种机制。我们进一步发现Chemerin抑制外周血MDSC的数量，并伴随着肿瘤组织的GM-CSF和IL-6的表达水平下降，但不影响MDSC的关键趋化因子，提示chemerin可能抑制GM-CSF和IL-6介导的MDSC的生成。我们发现chemerin的两个受体CMKLR1和CCRL2主要表达于肝癌细胞和肿瘤相关内皮细胞，而两种细胞分别是GM-CSF和IL-6的主要来源。利用体外细胞实验，我们证实了chemerin通过与两个受体相互作用，抑制NF-kb活化，从而抑制肝癌细胞和肿瘤相关内皮细胞分别产生GM-CSF和IL-6。最后利用中和抗体阻断GM-CSF和IL-6明显抑制Rarres2-/-小鼠的原位癌的大小和肺转移。我们的研究揭示了肝脏内源性高表达的Chemerin发挥负向调控肝脏炎症和肿瘤的发展，这样，下调Chemerin表达的因素可能导致肝脏炎症和肿瘤的发生发展；而给予外源性Chemerin或受体活化的小分子有可能作为潜在的肝癌治疗策略。