DNA修复缺陷通过R-loop/STRs结构影响肺癌新生抗原质量的机制研究

免疫检查点抑制剂（ICIs）治疗是治愈肺癌的新希望，筛选对ICIs治疗获益的人群是最重要的问题之一。高质量肿瘤新生抗原是肺癌ICIs治疗潜在的有效性标志物，但目前缺乏有效的检测手段。临床证据提示DNA修复通路特定基因的共突变可预测ICIs疗效，可能与肿瘤新抗原质量相关。本研究着眼于肿瘤新生抗原产生的源头-DNA损伤，聚焦基因转录过程中形成的DNA-RNA三链结构R-loop相关的短串联重复DNA序列（R-loop/STRs），首次提出DNA修复通路中特定基因共突变所导致R-loop/STRs拷贝数不稳定是产生高质量肿瘤新生抗原的关键机制的假说，应用DRIP-seq技术，通过突变体纯化，DNA结构生化研究和临床样本验证等方法，阐明碱基切除修复、错配修复和同源重组修复等DNA修复通路参与R-loop/STRs拷贝数变异的详细分子机制，为临床预测肿瘤新生抗原质量和ICIs疗效提供全新的思路。

Immune checkpoint inhibitor (ICIs) therapy brings a new hope for cure of lung cancer, while screening patients who will be benefit from ICIs therapy is one of the most important but unsolved issues. High-quality tumor neoantigen is one of the potential biomarkers to predict therapeutic efficacy of ICIs, however there are no available effective detection methodology. Previous study showed a strong correlation between DNA repair deficiency and the efficacy of ICIs therapy. By fixating on the source of tumor neoantigen-DNA damages, in current study we focused on the short tandem repeat DNA sequences (STRs) in R-loop, a DNA-RNA triple-strand structure, which has been discovered recently that usually forms during gene transcription. In current study, we, for the first time, put forward the hypothesis that the R-loop/STRs copy number instability caused by the co-mutation of DNA repair genes is a key mechanism for generating high-quality tumor neoantigens. Through the DRIP-seq technology, purification of tumor mutants, DNA biochemistry and clinical sample validation, this project is set to clarify the detailed molecular mechanism of DNA repair pathways such as base excision repair, mismatch repair and homologous recombination repair involved in R-loop/STRs copy number variation. The results of this study will provide new insights from the perspective of tumor neoantigen generation for clinical screening patients who will be benefit from ICIs therapy.