全基因组DNA甲基化在苯并[a]芘致肺癌发生的作用及机制研究

肺癌的发生是环境因素和遗传因素共同作用的结果。环境因素可通过改变机体的表观遗传学特征，影响个体的表型和肺癌发生风险。DNA甲基化是表观遗传学的重要组成部分，本课题拟在前期小样本肺癌病例对照人群的全基因DNA甲基化研究的基础上，在东风同济队列中设计肺癌的巢式病例对照人群，进行高通量全基因组DNA甲基化芯片检测，探讨DNA甲基化水平与肺癌早期遗传学指标（端粒长度、线粒体DNA拷贝数）的剂量-效应关系及与肺癌发生风险的关联性；通过测定血浆中致癌性多环芳烃苯并[a]芘的代谢产物与白蛋白的加合物水平，发现并探讨与苯并[a]芘暴露相关的DNA甲基化位点及其在苯并[a]芘致肺癌发生的中介效应；对上述人群研究的结果进一步在三种肺细胞系中进行功能研究，探索其生物学机制。本课题将有助于阐明以DNA甲基化为代表的表观遗传学改变在肺癌发生过程中的作用，为建立肺癌发生风险的预测模型和寻找肺癌预防新靶点提供依据。

The environmental and genetic factors are both significant determinants for lung cancer development. Studies have reported that epigenetic characteristics could be altered by exposure to environmental stimuli and then affect individual phenotype and lung cancer susceptibility. DNA methylation is an important component of epigenetics. In the previous study, we have carried out an epigenome-wide association study of DNA methylation in 109 pairs of lung cancer cases and controls. In this project, we will design a further nested lung cancer case-control study form the prospective Dongfeng-tongji cohort (528 pairs), and use the high-throughput Illumina MethylationEPIC BeadChip to detect the DNA methylation levels of about 850,000 CpG cites in these subjects. We will then evaluate the epigenome-wide associations of methylation levels of these CpG sites and telomere length, mitochondrial DNA copy numbers, and the incident risk of lung cancer among this nested case-control study. In both lung cancer case-control and nested case-control study populations, we will detect the plasma concentrations of albumin adducts combined to benzo(a)pyrene-7,8-diol-9,10-epoxide (BPDE), the metabolized ultimate carcinogen for benzo[a]pyrene (B[a]P). The epigenome-wide associations between plasma concentration of BPDE-albumin adducts and DNA methylation levels will be evaluated in both populations, and the mediation roles of the B[a]P significantly-related CpG sites in the association between B[a]P exposure and lung cancer will also be tested. The biological mechanisms of the identified positive CpG sites will be further assessed by the functional studies in three lung cell lines (BEAS-2B, 16HBE, and A549), by treating these cell lines with different levels of B[a]P. The effects of these positive CpG sites on expression levels of corresponding genes and their different methylation levels between normal and tumor lung tissues will also be compared. This study will help to elucidate the role of epigenetic changes represented by DNA methylation in the occurrence of lung cancer and provide the scientific basis for the establishment of prediction models for lung cancer risk and new targets for lung cancer prevention.