GFI1调控巨噬细胞介导的免疫应答抑制结肠癌肝转移的机制研究

Metastasis is the main cause of the death of colorectal cancer (CRC). The metastasis of tumor is the result of interaction between microenvironment and tumor cells. However, the interaction and molecular mechanism between microenvironment and CRC cells have not yet been fully elucidated. We have previously identified that CRC with high expression of GFI1 is difficult to develop distal organ metastasis. Is this related to the anti tumor immune response of the metastatic organ? We found that GFI1 significantly increased the content of tumor infiltrating macrophages in a large number of clinical samples and CRC liver metastasis model in mice. Therefore, based on previous results, we will analyze the influence of high expression of GFI1 in CRC cells on functions of macrophages with the help of CRC metastasis animal models and clinical samples; determine the key signal released by CRC cells that can regulate functions of macrophage; deeply analyze the effects of CRC cells GFI1 expression level on phagocytic function of macrophages and activation of inflammasomes in vivo / in vitro, clarify the partial mechanism of metastatic microenvironment to regulate CRC metastasis. This study will reveal the mechanism that GFI1 inhibits CRC transfer through the regulation of macrophage mediated immune response and provides a new idea for the clinical GFI1 deletion of CRC metastasis.

转移播散是结直肠癌（CRC）致死的主要原因，肿瘤远端转移的发生是转移微环境与肿瘤细胞相互作用的结果，然而微环境与CRC细胞间的相互作用及分子机制尚未完全阐明。我们前期已明确高表达GFI1的CRC难以发生远端器官转移，这是否与其影响了转移器官的抗肿瘤免疫应答有关？我们在大量临床样本及小鼠CRC肝转移模型中均发现GFI1可显著增加肿瘤浸润巨噬细胞的含量。因此本研究拟在前期研究基础上，借助CRC转移动物模型及临床样本，多层次分析CRC细胞中GFI1的高表达对巨噬细胞功能的影响，明确CRC细胞释放的影响巨噬细胞功能的关键信号；体内/外深入分析CRC细胞GFI1表达水平对巨噬细胞吞噬功能及炎性小体活化的影响，对CRC细胞死亡的影响，阐明转移微环境调控CRC转移的部分机制。本研究将揭示GFI1通过调控巨噬细胞介导的免疫应答抑制CRC转移的机制，为临床GFI1缺失CRC转移的治疗提供新思路。

结肠癌肝转移是临床结肠癌患者预后不良及死亡的主要原因，对结肠癌患者的肝转移进行早期评估和干预是解决这一临床问题的关键。我们在前期研究中已阐明GFI1可作为结肠癌肝转移的独立评价因子，GFI1低表达的患者更容易出现肝转移。在本研究中，我们探讨了GFI1调控巨噬细胞的吞噬杀伤功能从而影响肝转移发生的机制。借助体外肿瘤细胞与巨噬细胞共培养及体内结肠癌细胞脾注射肝转移模型，我们筛选并验证了巨噬细胞是参与调控结肠癌肝转移的关键免疫细胞，早期清除巨噬细胞可有效恢复Gfi1高表达的结肠癌细胞形成肝转移灶的能力。在此基础上，我们探讨了GFI1/Gfi1表达水平不同的结肠癌细胞对巨噬细胞吞噬杀伤功能的影响，明确GFI1/Gfi1低表达的结肠癌细胞即可诱导抗吞噬信号CD47-SIRPɑ的高度活化，又可招募SIRPɑ表达水平高的巨噬细胞到达肝组织，从而逃避巨噬细胞对其的吞噬清除。而GFI1/Gfi1高表达的结肠癌细胞可显著活化巨噬细胞炎性小体信号，促进IL1β的释放，IL1β可诱导GFI1/Gfi1高表达的结肠癌细胞死亡。这提示GFI1低表达的患者可早期恢复其巨噬细胞的吞噬杀伤能力，从而抑制其肝转移的发生。因此，我们继续筛选并验证调控巨噬细胞吞噬杀伤功能的关键分泌蛋白，为临床GFI1低表达结肠癌患者肝转移早期干预提供理论依据。