遗传变异调控基因表达影响肺癌易感性的分子流行病学研究

Epidemiological studies have shown that the development of lung cancer is result from a complex interplay between genetic and environmental factors. In our previous studies, Genome-wide association studies (GWAS) of lung cancer have identified several novel susceptibility loci, which provided valuable insight into the mechanisms of lung cancer. However, ‘missing heritability’ is still the major challenge and the potential biological functional variants are still unclear for most of the identified loci by now. In this study, we plan to perform whole transcriptome sequencing and genome-wide genotyping to build a database of associations between genotypes and expression of genes. Then we will predict the expression of genes in the whole genome based on this database and our previous GWAS dataset, which will be further evaluated for the associations between cases and controls. The significantly associated genes will be further validated in an independent GWAS dataset of Asian from public database dbGap. We will also conduct molecular biology experiments to confirm the significant susceptibility genes and SNPs, and explore the potential susceptibility mechanisms. This study will help identify novel susceptibility genes of lung cancer, fill out the ‘missing heritability’, and explain the mechanisms underlying the associations. The findings of this project could be used to screen high-risk population, provide theoretical foundation for early prevention, diagnosis and treatment of lung cancer in Chinese population.

肺癌的发生是遗传因素与环境因素共同作用的结果。前期，全基因组关联研究（GWAS）发现了多个肺癌遗传易感区域，为阐明肺癌发生机制提供了重要线索。然而，目前我们仍面临肺癌“遗传度丢失”及真正致病基因(位点)尚未确认等关键科学问题。本课题拟通过对中国人群正常肺组织进行全转录组测序和全基因组分型，构建基因型-表达关联数据库；在此基础上，利用中国人群肺癌GWAS基因型数据，综合多个表达调控位点的联合效应预测基因的表达水平，评价基因表达与肺癌易感性的关联，并使用亚洲人群肺癌GWAS公共数据库进行独立验证；对研究发现的易感基因及其表达调控位点，进一步开展生物功能学研究，鉴定其遗传易感机制。本研究可以从基因水平整合多个表达调控位点的联合效应，降低多重比较的次数，提高研究效率。研究有望发现新的肺癌易感基因，填补肺癌“遗传度缺失”，解析肺癌遗传易感机制，为实施肺癌个体化预防及早诊早治提供理论依据。

本项目首先对116例中国人群的肺组织进行了全转录组RNA-Seq测序，对外周血进行了全基因组基因分型，构建了中国人群肺组织eQTL数据库。在此基础上，本项目利用中国人群肺癌GWAS数据库（13327肺癌病例vs. 13328对照）开展了TWAS分析，共鉴定出18个潜在肺癌易感基因，其中8个在肺组织中显著。通过共定位分析，我们揭示其中4个区域可能共享相同的GWAS和eQTL信号，包括2个已经报道的肺癌易感区域（6q22.1-DCBLD1和11q23.3-MPZL3）以及2个新的肺癌易感区域（4p15.31-DCAF16和11q23.3-CBL）。针对2个新易感区域的生物信息学分析，发现rs7667864（C>A）位于DCAF16启动子区，可显著增加肺组织中DCAF16表达（β=0.29，P= 3.84 × 10−8）；而rs2298650 (G > T)位于CBL增强子区，与肺组织中CBL表达降低有关（β=-0.17，P= 2.82 × 10−8）。在A549和SPCA1两个肺癌细胞系中敲降DCAF16，可显著抑制了细胞活力、降低了菌落形成能力，并抑制细胞迁移。而CBL是原癌基因，前期多项体内外功能学实验已经证实了CBL在肺癌发生中的重要作用。本研究在揭示已知肺癌易感区域关键基因的基础上，进一步发现了新的肺癌易感基因，为阐明肺癌遗传易感基础提供了新线索。除上述以外，我们还基于构建的肺癌遗传易感基础图谱，构建了中国人群肺癌遗传风险评分，并基于中国慢性病前瞻性队列进行了独立评价，揭示不同遗传风险的人群应采用个体化的筛查方案。基于该评分方案，我们还进一步探讨了遗传风险与常见生活方式在肺癌发生中的交互作用和联合效应，发表了多篇高质量研究论文。