ROS1融合蛋白调控肺癌中PD-L1表达及其分子机制研究

Tumor driven genes have been demonstrated to not only promote cancer cell proliferation, but also be involved in tumor immune escape. ROS1 (Receptor tyrosine kinase c-ros oncogene 1) is a key oncogenic driver gene, but the molecular mechanisms by which ROS1 participates in tumorigenesis remain elusive. Programmed death-ligand 1 (PD-L1) is a checkpoint of the immunosuppressive pathway and plays an important role in immunoescape of lung cancer. We firstly discovered that ROS1 fusion proteins can induce PD-L1 expression in lung cancer cells, which was associated with increased expression of miR-181a and p-ERK. Based on these findings, we hypothesize that ROS1 fusion proteins regulate PD-L1 expression through inducing miR-181a expression to activate ERK kinase in lung cancer cells. In this proposal, we will uncover the regulatory mechanism of PD-L1 expression by ROS1 fusion proteins in lung cancer. Moreover, we will establish a conditional mouse lung tumor model carrying ROS1 rearrangement to validate the regulatory mechanism in vivo, and to determine the effects of ROS1 on tumor immune microenvironment. Lastly, we will test the efficacy of PD-L1 antibody blockade plus Crizotinib on tumor growth in ROS1 rearrangement-driven murine lung cancer models. Therefore, the proposed studies will reveal novel mechanisms of how ROS1 promotes lung cancer growth, which may provide new insights into developing new strategies to treat lung cancer patients with expression of ROS1 fusion proteins.

一些肿瘤驱动基因不仅促进肿瘤细胞增殖，还参与肿瘤的免疫逃逸。ROS1融合基因是一个重要的肿瘤驱动基因，但其在肿瘤发生发展中的作用机制有待深入研究。我们前期研究表明，ROS1融合蛋白在肺癌细胞中调控免疫检查点蛋白PD-L1的表达，并且PD-L1表达与miR-181a、ERK磷酸化水平密切相关。因此，我们提出ROS1融合蛋白在肺癌细胞中通过miR-181a激活ERK激酶，上调PD-L1表达的假说。本项目拟在分子和细胞水平，分别干预ROS1融合基因、miR-181a及其靶基因、ERK的磷酸化，阐明ROS1融合蛋白调控PD-L1的分子机制；并将在原发肺癌小鼠模型中进一步验证该作用机制，观测肿瘤免疫微环境的相应变化；最后，我们将在动物模型中，初步探索针对肿瘤驱动基因ROS1的治疗与针对PD-L1治疗之间的协调效应。本研究将会揭示ROS1融合基因调控肿瘤生长的新机制，为肺癌的临床治疗提供新思路。

TKI靶向治疗后获得性耐药产生的机制大致分为两类：一类是突变依赖耐药，即驱动基因突变或者扩增导致肿瘤细胞逃逸靶向药物的识别，如EGFR T790M突变、ALK G1202R突变、ROS1 G2032R突变、MET扩增等；另一类是非突变依赖耐药，是肿瘤细胞在药物压力下产生了基因调控及表达模式变化，重新激活促癌通路诱导肿瘤进展。突变依赖的获得性耐药的发生源于靶基因突变或非靶基因突变，相关突变易于通过基因测序获得，目前的应对策略是针对新突变开发新的靶向药物，例如EGFR、ALK和ROS1的靶向药物已更新至第三代。非突变依赖的获得性耐药分子机制复杂不清，尚无有效干预手段。临床前研究发现联合用药可部分缓解此类耐药，如Aruora A和EGFR抑制剂联用，SHP2和ALK抑制剂联用，E-cadherin和ROS1抑制剂联用等，遗憾的是进入临床试验的联合用药并未取得明确治疗效果。