NLRX1通过I型干扰素通路协同PD-L1效应促进口腔鳞癌发展的研究

The immunotherapy targeting PD-L1 has been revealed to be efficacious in several malignancies, whereas its application is significantly hindered by the treatment resistance; taking OSCC as one example, the efficacy only presents as 13.3%（N Engl J Med, 2016）. One of the important approaches to overcome the resistance is to seeking out the key synergistic molecule of immunotherapy (Cell,2016). IFN-I is demonstrated to regulate the expression of PD-L1 in OSCC, and NLRX1 is upregulated in the OSCC cell that is immune cell-resistant. Thus, we propose that NLRX1 might inhibit the downstream IFN-I pathway by promoting autophagic degradation of STING, thereby suppressing the PD-L1 expression and mediating the immunotherapy resistance. To validate the hypothesis, the relationship between NLRX1 and STING/PD-L1 and the clinical significance are investigated in OSCC tissues and bioinformatics database; thereafter, the synergistic effect of NLRX1 and PD-L1 in OSCC would be explored in vitro and in vivo; besides, the mechanism that whether NLRX1 synergizes with PD-L1 through inhibiting the IFN-I pathway would be studied; lastly, preclinical investigation to overcome therapeutic resistance of PD-L1 by knocking down NLRX1 would be conducted in OSCC model, aiming at illuminating that whether NLRX1 serves as the key synergistic molecule in therapeutic resistance of PD-L1 and the detailed mechanism, and exploring the applying potential of NLRX1 as the target of immunotherapy.

以PD-L1为靶点的免疫治疗已被证实在多肿瘤中有效，但存在治疗抵抗，在口腔鳞癌中仅13.3%有效（N Engl J Med,2016）；寻找免疫治疗协同分子是克服此问题的有效途径（Cell,2016）。已发现OSCC中IFN-I可调控PD-L1表达，申请人发现免疫抵抗的OSCC细胞伴NLRX1上调，因此假定NLRX1可经自噬降解STING而抑制IFN-I及PD-L1而介导免疫抵抗。为验证此假说，拟首先在OSCC样本及数据库中探讨NLRX1与STING/PD-L1的相关性和临床意义；然后，体内外探究NLRX1与PD-L1在OSCC中协同效应；继之研究NLRX1通过抑制IFN-I实现与PD-L1协同效应的体内外机制；最后利用小鼠OSCC模型，敲低NLRX1解除PD-L1抵抗的临床前探究，阐明NLRX1是否为介导OSCC中PD-L1抵抗的关键分子及其机制，探究将其作为免疫治疗协同靶点的潜能。

以PD-L1为靶点的免疫治疗已被证实在多肿瘤中有效，但在口腔鳞癌中的有效率仅为13.3%（N Engl J Med,2016）；寻找免疫治疗协同分子是克服此问题的有效途径。已发现OSCC中IFN-I可上调PD-L1表达，肿瘤微环境中抗原提呈细胞(Antigen presenting cell, APC)表面PD-L1的表达水平与PD-L1单抗疗效密切相关(J Clin Invest, 2018)，申请人发现免疫杀伤抵抗的OSCC细胞伴NLRX1上调，前期研究曾报道HPV16 E7可与NLRX1互作从而降解STING(J Clin Invest, 2020)，但HPV- OSCC中未见相关报道，因此假定NLRX1可经自噬降解STING而抑制IFN-I及APC表面PD-L1，导致PD-L1治疗抵抗。基于生物信息学分析、OSCC临床样本、细胞功能与机制实验、动物体内实验的研究发现，NLRX1可能作为OSCC中促癌因子，通过靶向结合TUFM，增强线粒体自噬，从而激活STING降解轴，阻遏IFN-I通路激活和APC细胞表面PD-L1的表达，介导OSCC的PD-L1免疫治疗抵抗，靶向于NLRX1或自噬抑制具有增强OSCC的PD-L1免疫疗效的临床潜能，具有较高的临床转化意义；还发现了NLRX1可能通过诱导线粒体自噬降解抗原提呈相关主要蛋白MHC-I，减弱抗瘤免疫反应，而MHC-I主导的抗原呈递通路是CD8+T细胞激活的重要第一信号，这提示靶向NLRX1有望增强CD8+T细胞对于肿瘤的杀伤作用。本研究的科学意义是：其增强了我们对于口腔鳞癌PD-L1免疫治疗抵抗相关关键分子及其机制的理解，对寻找 OSCC 的免疫治疗增效靶点，发展新的OSCC治疗策略提供新思路；NLRX1有望成为判断OSCC预后和复发的分子标志物。