LKB1调节免疫微环境诱导肺癌抗PD-1免疫治疗原发耐药的分子机制研究

Patients with LKB1 mutation showed unfavorable response to PD-1/PD-L1 axis blockade immunotherapy in lung cancer according to recent clinical investigation, but the underlying mechanisms remain largely unclear. Our previous study identified LKB1 mutation was significantly correlated with reduced tumor infiltrating lymphocytes and PD-L1 expression (Clin Cancer Res 2017). Recently, our preliminary data showed that LKB1 deficiency (loss/mutation) was associated with decrease of leukocyte transendothelial migration related proteins and FAS/FASL pro-apoptosis signature through analysis of large data platform (TCGA etc.) and lung cancer specimens. Thus we presume that LKB1 deficiency affects the quantity and function of lymphocytes in tumor microenvironment and leads to primary resistance to anti-PD-1 therapy in lung cancer. We will use genome editing technique, cells co-culture and mice lung cancer model to verify our hypothesis in vitro and in vivo. We aim (1) to explore the molecular mechanism of LKB1 deficiency on leukocyte infiltration and immune-mediated apoptosis; (2) to investigate whether the combination of LKB1 pathway activator and anti-PD-1 therapy could reverse the primary resistance to immunotherapy in lung cancer mice model and provide evidence for further prospective clinical trial.

临床研究表明LKB1突变肺癌患者接受抗PD-1免疫治疗效果不佳，但具体分子机制尚不清楚。前期研究中，我们发现肺癌中LKB1突变与肿瘤浸润淋巴细胞及PD-L1表达减少显著相关（Clin Cancer Res 2017）。在此基础上，我们通过TCGA等大数据平台并结合肺癌临床标本分析发现：LKB1缺陷（缺失/突变）与淋巴细胞跨膜迁移相关分子及FAS/FASL促凋亡信号表达下降显著相关。因此，我们提出LKB1缺陷可能通过影响肿瘤微环境中淋巴细胞数量及功能进而诱导免疫治疗原发耐药的科学假设。本研究拟通过基因编辑技术、细胞共培养及小鼠肺癌模型等体内外实验，旨在：（1）系统阐述LKB1缺陷抑制肿瘤微环境中淋巴细胞浸润及促凋亡能力进而介导免疫治疗原发耐药的分子机制；（2）探讨LKB1通路激活剂联合抗PD-1治疗对LKB1缺陷肺癌免疫治疗原发耐药逆转的效果，为进一步开展前瞻性临床试验提供科学依据。

肝激酶B1（LKB1）突变在肺腺癌（LUAD）中普遍存在，导致免疫治疗的原发性耐药性，但其机制仍有待阐明。利用单细胞RNA测序，我们发现在Kras/Lkb1驱动的肿瘤中，由于T细胞跨膜迁移和粘附功能受损，导致T细胞浸润减少。在机制上，我们发现 LKB1 突变癌细胞通过下调细胞间粘附分子-1(ICAM1)介导的细胞粘附和攻击来主动逃避与T细胞的相互作用。 Lkb1缺陷型肿瘤中Icam1的异位表达增加了CD8+T细胞的浸润，并使肺癌对原位小鼠模型中的程序性细胞死亡-1 (PD-1) 阻断免疫疗法重新敏感。 进一步的药物筛选证明，CDK4/6抑制剂可以通过减弱磷酸化RB来上调 ICAM1的表达，改善免疫抵抗状态并恢复受损的T细胞跨膜迁移和粘附功能。更重要的是，在多个LKB1缺陷小鼠模型中，使用CDK4/6抑制剂和anti-PD-1免疫治疗的组合策略可恢复抗肿瘤免疫并促进ICAM1触发的免疫反应。因此，联合CDK4/6抑制剂和PD-1阻断治疗对于携带LKB1突变的肺癌患者是一种有前景的治疗方案。