白介素-17在原发性肺癌发生及演进过程中的作用及其分子机制研究

Interleukin-17 (IL-17) is a critical pro-inflammatory cytokine, which may play an essential role in inflammation related carcinogenesis. Our team recently discovered that IL-17 receptor C (IL-17RC) was highly expressed in the tumor-associated macrophages (TAMs) of lung cancer. We found that TAMs in the lung cancer microenvironment were recruited by IL-17. These TAMs were induced to differentiate into the tumor-promoting M2 TAMs by prostaglandin E2. In addition, we found that IL-17RC expression was increased in alveolar hyperplasia, an early stage in lung cancer initiation, in the K-rasLA1 mouse lungs. IL-17 could also be detected in the bronchoalveolar lavage (BAL) fluid of mice after inhalation exposure to asbestos, a recognized lung carcinogen in humans. IL-17-positive alveolar macrophages could be detected in BAL after asbestos-exposure. IL-6 is an important downstream effector of IL-17 and is significantly increased in the lung of the mice post-exposure to asbestos. Based on these preliminary findings, we hypothesize that IL-17 may promote the initiation and progression of lung cancer. In order to test this hypothesis, we will make two types of animal models. One model is to over-express IL-17 in mouse lungs by adenovirus-mediated gene transfer of murine IL-17 cDNA through intra-tracheal injection. The other model is the IL-17RC gene knockout mouse. Urethane will be used to induce formation of primary lung cancers in both models. We will use these models to study the effects of IL-17 over-expression or blockade on lung cancer initiation and progression. We anticipate to identify the cellular and molecular mechanisms of how IL-17 affects the pathogenesis. Furthermore, we will test if anti-IL-17 neutralizing antibodies or inhibitors of TH17 cell can inhibit lung cancer initiation and progression in the animal models. We also propose to investigate the effects of IL-17 on lung cancer bionomics and its molecular mechanisms. This project is expected to identify new mechanisms of lung carcinogenesis, in order to develop novel methods for lung cancer prevention and treatment.

白介素-17（IL-17）是重要的炎症因子，可能在炎症相关的肿瘤发生中发挥重要作用。我们发现肺癌通过高表达IL-17募集肿瘤相关巨噬细胞至肿瘤微环境，并在前列腺素E2作用下分化为促进肿瘤发展的M2亚型；还发现K-rasLA1小鼠肺泡重度不典型增生病灶高表达IL-17受体C，而吸入致癌剂石棉可诱导小鼠肺泡灌洗液中出现IL-17及巨噬细胞表达IL-17。根据这些发现，我们推测IL-17可能参与肺癌发生及演进。本项目将通过基因转染建立IL-17高表达小鼠模型，并利用IL-17受体C基因敲除小鼠模型，分别采用乌拉坦诱导原发性肺癌的发生，明确IL-17在肺癌发生及演进中的作用；通过IL-17抗体和TH17细胞分化抑制剂，观察抑制IL-17对肺癌发生的影响；进一步在体外、体内对肺癌细胞施加IL-17，观察IL-17对肺癌细胞的直接和间接作用，同时研究其分子、细胞机理，探索肺癌发生及演进的新机制。

肺癌是我国发病率最高的恶性肿瘤，也是我国及全球癌症的首要死因。吸烟是导致肺癌的重要危险因素，白介素17（IL-17）作为一个重要的炎症因子，在吸烟所致的气道慢性炎症反应中，IL-17分泌明显增加。IL-17在不同肿瘤中表现出抑制和促进肿瘤进展的双重属性，我们前期研究发现在肺癌中，IL-17可促进肿瘤形成以M2型肿瘤相关巨噬细胞（TAMs）为主的免疫抑制微环境，可能具有促进肺癌进展的作用。本项目分别从阻断体内IL-17作用、增强肺部IL-17表达及药物干预IL-17等方面研究并证实了IL-17在肺癌发生及进展中的作用。我们首先构建IL-17受体C基因敲除的FVB小鼠（FVB Il17rc-/-小鼠），以FVB Il17rc+/+小鼠为对照，通过乌拉坦诱导小鼠原发性肺癌，借助micro-CT观察小鼠原发性肺癌的发生及进展。结果发现敲除IL-17RC基因，阻断IL-17的作用可减少肺癌的发生并延缓其进展，进而以携带IL-17 cDNA的腺病毒感染小鼠呼吸道，增强肺部IL-17表达，发现IL-17高表达可加速肺癌的发生与进展；以SR1001抑制体内IL-17主要来源的Th17细胞分化，减少IL-17的分泌或直接以抗IL-17抗体中和体内IL-17，发现均可显著抑制小鼠原发性肺癌的发生及进展，上述结果证实IL-17具有促进肺癌发生及进展的作用。为明确其具体机制，我们进一步对FVB Il17rc-/-小鼠及FVB Il17rc+/+小鼠肺癌标本进行研究，分别观察肿瘤细胞增殖、凋亡及肿瘤组织中新生血管生成，发现抑制或阻断IL-17可增加肿瘤细胞凋亡，减少增殖，也减少了新生血管形成。肿瘤微环境中活化的主要信号通路是ERK及NF-κB。我们还以免疫组化及流式细胞分析肿瘤组织中TAMs构成，发现阻断IL-17可降低肿瘤组织M2型TAMs密度。此外，我们还对不同演讲阶段的肺癌组织开展了全转录组测序，正在对数据进行深入分析挖掘。综合这些结果证实IL-17可通过促进肿瘤细胞增殖、抑制其凋亡、促进肿瘤新生血管形成、促进肿瘤形成免疫抑制微环境等机制促进肺癌的发生和进展，提示其有望成为肺癌防治的一个潜在靶点。