circRNA是精细调控编码基因功能的重要分子，其侧翼Alu重复序列对circRNA成环有着至关重要的作用，该区域的结构变异极可能会干扰其形成，影响对下游基因的调控。课题组前期研究发现circRNA0050386在肺癌组织和血浆中的表达显著低于正常对照，且与抑癌基因SRGAP3表达呈正相关。该circRNA Alu序列存在多个变异位点，预实验发现c.536-/TTTA indel影响其表达并与肺癌发病风险有关，据此我们假设：该indel变异可能通过影响circRNA剪接，进而干扰其调控靶基因的效应而影响肺癌的发生发展。本项目拟在双中心大样本人群检测该indel的频率分布及circRNA的差异表达，分析其与肺癌发病的关联；通过基因编辑技术构建一系列含不同indel基因型的肺模式细胞系，整合体内、体外等实验方法系统研究该indel影响肺癌发生发展的分子机制，为肺癌的高危人群筛选和防治提供依据。

circRNAs are important molecules that help to exactly regulate the function of coding-genes. The flanking Alu repeat sequences are crucially important for the circularization of circRNAs. Structural variations in the Alu sequence may interfere with circRNA formation, and thus affect the regulation of downstream genes. Our preliminary study indicated that the expression of circRNA0050386 in lung cancer tissues and plasma were significantly lower than those of normal controls, and the expression level of circRNA was positively correlated with SRGAP3 gene's expression. There are genetic variants in the flanking Alu sequence of circRNA0050386. Among of them, c.536-/TTTA indel had a significant correlation with lung cancer risk and with circRNA0050386 expression. Thus, we hypothesized that c.536-/TTTA is associated with lung cancer risk via its effect on circRNA0050386 splicing, thereby interfering with the regulation of target genes. Here, in this project we plan to test the association between the c.536-/TTTA and lung cancer risk as well as prognosis by genotyping the indel and detecting the circRNA expression in a two-center large population study. To investigate the molecular mechanism of the c.536-/TTTA in lung cancer development and progression, a series of human bronchial epithetical model cell lines carrying different genotype of the c.536-/TTTA will be constructed via CRISPR/Cas9 technique, and a series of functional assays will be further implemented in vitro and in vivo. This project will help to clarify the mechanism of lung cancer pathology, and provide scientific evidences for the prevention and treatment of lung cancer.