LRP16调控NLRP3炎症小体组装活化及其参与治疗触发瘤床免疫反应的机制研究

Inflammation is the seventh hallmark for cancer establishment and progression. Inflammatory responses play decisive roles at different stages of tumor development, including initiation, promotion, malignant conversion, invasion, and metastasis. Inflammation also affects immune surveillance and responses to therapy. Inflammasomes are molecular platforms activated upon cellular infection or stress that trigger the maturation of proinflammatory cytokines such as IL-1β to engage innate immune defenses. The NLRP3 inflammasome is currently the best-characterized inflammasome, however, the underlying mechanism of its assembly and activation remains unclear. A previous study has indicated that a crucial role for PKR in inflammasome activation, and indicate that it should be possible to pharmacologically target this molecule to treat inflammation. Our recent study demonstrated that LRP16 could form a protein complex with NLRP3 and PKR, indicating that LRP16 plays a crucial role in inflammasome activation. We propose these objectives as below: 1) To clarify the role and mechanism of LRP16 on the NLRP3 assembly at the molecular level; 2) Using a variety of gene knockout mouse model, to determine how the mechanism and regulation effect of LRP16 on NLRP3 invovled in the chemoradiotherapy-triggered tumor bed immune function; 3) From clinical specimens, to establish the relationship between the expression level of LRP16 and NLRP3 and the prognosis of patients with radiotherapy and chemotherapy, and the correlation between the immune cells homing to the tumor bed, revealing the clinical significance of NLRP3 regulation of LRP16 in tumor bed immunity; 4) To clarify the target of LRP16 mediated NLRP3 activation pathway as a potential to improve tumor bed immune tolerance.This project will identify a novel LRP16-mediated molecular pathway in regulating the NLRP3 inflammasome involved in tumor-bed immunity, and will also provide a potential new therapeutic target for the early diagnosis and treatment of cancer.

持续慢性炎症与免疫调节紊乱和肿瘤发生关系密切，NLRP3炎症小体在细胞和组织炎症的调控具有重要作用，但其激活机制仍不清楚，既往研究显示PKR作为NLRP3的调控蛋白参与其激活，我们发现LRP16能与PKR、NLRP3组成一个复合体，提示LRP16在NLRP3组装激活中的重要作用。本课题拟开展以下研究：1）从分子水平阐明LRP16对NLRP3组装的调控作用及机制；2）利用多种基因敲除鼠模型，从整体动物水平研究LRP16对NLRP3的调控及在放化疗触发瘤床免疫功能机制探讨；3）从临床标本水平，建立LRP16与NLRP3表达水平与瘤床免疫细胞归巢和病人预后的相关性研究，揭示LRP16调控NLRP3参与瘤床免疫的临床意义；4）阐明靶向LRP16介导NLRP3活化作为潜在改善瘤床免疫耐受的途径。本项目完成将识别一条新的调控NLRP3激活的分子途径及其在瘤床免疫调控中的潜在机制，为肿瘤治疗提供新选择。

基于我们前期研究发现LRP16在多种肿瘤中异常表达，提示LRP16参与肿瘤的发生发展过程。在该项目中，我们通过从细胞水平、动物模型及临床组织标本等不同层面探究了LRP16参与结直肠癌的发生发展，证实LRP16作为结直肠癌发生中的致癌基因，在结直肠癌细胞生长和放化疗抵抗的发生中具有重要的促进作用，LRP16的高表达与病人具有较差的预后和生存时间存在正相关性。机制上，通过质谱筛选相互作用蛋白，我们发现LRP16与PKR以及NF-kappaB之间相互作用。LRP16通过支架作用调控PKR依赖的DNA损伤诱导的NF-kappaB活性，促进肿瘤生长及放化疗抵抗的发生，该调控过程依赖于LRP16结合poly-(ADP-ribose)的能力；我们前期筛选出小分子化合物可以显著抑制LRP16与PKR、IKK之间的相互作用，钝化DNA损伤条件下LRP16调控的NF-kappaB活性逆转LRP16在放化疗抵抗中的功能作用。本项目的完成不仅为DNA损伤诱导NF-kappaB激活分子机制提供新认识，也为后续结直肠癌的临床诊断和增敏放化疗提供新的策略；此外，我们还发现低剂量组蛋白去乙酰化酶抑制能够重编程肿瘤相关巨噬细胞向抗肿瘤、促炎表型转变，同时抑制髓样抑制细胞的浸润，进而重塑肿瘤免疫抑制微环境，提高抗肿瘤免疫应答。低剂量组蛋白去乙酰化酶抑制剂与PD-L1抗体联合使用可以进一步提高肿瘤的治疗效果，延长荷瘤小鼠的生存期。主要内容发表在《eLife》和《Oncogene》杂志。