Argonaute 2调控KRAS突变非小细胞肺癌增殖及辐射敏感性的机制研究

KRAS突变型NSCLC易复发转移且仍缺乏有效治疗手段，是当前治疗的瓶颈与难点。申请者前期研究发现RNA干扰机制的核心蛋白Argonaute 2（AGO2）在KRAS突变依赖性NSCLC中发挥重要作用。AGO2通过与KRAS蛋白相互作用促进肿瘤增殖。而在电离辐射致DNA双链断裂情况下AGO2与KRAS解离。发生核转位的AGO2蛋白与DNA损伤修复相关蛋白BRIT1相互作用，参与同源重组（HR）修复。而胞浆AGO2通过调控miRNAs表达间接调节染色质结构影响HR效率。本课题以不同亚细胞定位AGO2功能及翻译后修饰特征作为切入点，借助基因组学及蛋白组学方法对AGO2介导KRAS突变依赖性肺癌生物学行为及放疗抵抗的具体机制进行深入研究，探讨AGO2在KRAS信号转导、RNA干扰途径、HR及表观遗传调控之间的作用。阐明上述问题将有助于开发全新的抗KRAS突变型NSCLC治疗策略。

Lung cancer is the most common cancer with high lethality. Carcinogenic Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation is the most common gain-of-function alteration, accounting for about 30% of lung adenocarcinomas in western countries and about 10% of Asian lung adenocarcinomas. In lung cancer, considerable progress in developing molecularly-driven therapeutics has been made in the past decades, mainly including targeted therapies against oncogenic drivers, such as EGFR, HER2, EML4-ALK, MET, ROS1, and BRAF mutations, and immunotherapies in non-oncogene-driven lung cancer, such as PD1 and PDL1 alterations. However, for KRAS-mutant lung cancer, the treatment options are still limited, and chemotherapies remain the first-line recommendation. Nowadays, a new wave of attempts is motivated to target KRAS directly, which has long been considered undruggable. According to our previous findings, argonaute 2 (AGO2), a key catalytic component of the RNA interfering silencing complex (RISC), has a pivotal role in KRAS-driven NSCLC by directly interacting with KRAS protein. AGO2 is essential for mutant KRAS-dependent cell proliferation and radiation resistance. Interestingly, during the DNA damage response (DDR)-induced by ionizing radiation, AGO2 disassociated with KRAS and translocated into the nuclear. Further investigation indicated that AGO2 may involve in the homologous recombination (HR) mechanism by interacting with BRIT1, an early DNA damage response protein, and recruiting to the DNA damaged sites. The applicant also found that AGO2 might modulate HR processing by directly interacting with chromatin remodeling factors. Unlike the nuclear form, cytosolic AGO2 can also regulate HR repair indirectly through an epigenetic mechanism, by affecting EZH2 function and histone modification via miRNAs-mediated RNA interference. This concept was supported by the evidence that IR altered the miRNA expression profile. The IR-induced upregulations of let-7c and miR-101, which may potentially target EZH2. The aim of this proposal is to decipher the underlying mechanism of AGO2 in regulating KRAS-downstream signaling, DNA damage repair system, and related epigenetic remodeling. Multiple assays, such as proteomics, genomics and transcriptomics methods, will be applied to map the post-regulation and regulation network of AGO2-involved radiation-induced DNA damage response. Our findings will reveal a novel DNA repair regulation system, by connecting two highly conserved gene defense mechanisms, RNA interference and DNA damage repair system. Our future work might provide novel targeting strategies for treating KRAS-mutant NSCLC.