Epigenetic Changes Link COPD and Lung Cancer

描述(申请人提供)：吸烟是慢性阻塞性肺疾病(COPD)和肺癌的主要致病因素，这些疾病的发病机制被认为是有联系的，因为COPD患者患肺癌的风险是前者的2-4倍。通过胞嘧啶启动子甲基化和组蛋白修饰导致的基因表观遗传沉默是肺癌发生和克隆发展过程中影响数百个基因表达的一个重要事件。我们最初对COPD吸烟者队列中发生癌症的嵌套病例对照研究表明，六个基因组中三个或更多基因的伴随甲基化与肺癌风险增加6.5倍相关。在Lovelace Smokers Cohort(LSC)的非癌症吸烟者中扩展这些研究表明，高甲基化指数(两个或更多基因甲基化)以及p16和GATA4基因的甲基化与肺功能低下有关。研究还发现，双链断裂修复能力和这一途径中的特定基因是痰中基因甲基化的决定因素，P53密码子72处的Proline变体对LSC的粘液细胞增殖和肺功能下降具有保护作用。基于这些研究，我们假设通过组织损伤和重塑介导的COPD的发展将驱动特定基因的表观遗传沉默，从而促进肺癌的发展。从COPD吸烟者的痰中检测这些基因可能会为COPD的发生发展和早期癌症检测提供新的生物标志物。目的1将通过比较患有和不患有慢性阻塞性肺疾病的患者的腺癌中的甲基组，并评估P53密码子72的基因型，来识别和验证甲基化作为COPD状态的函数的特征。目的2将使用来自非吸烟者的原代人支气管上皮细胞(BECs)，其中P53密码子72的精氨酸与长期暴露在香烟烟雾中的Pro基因型相比较，以识别基因和受影响的途径，重点是调控组织重塑和细胞凋亡的基因，以及多梳抑制复合体2(PRC2)基因。AIM 3将在LSC的200名COPD患者和400名对照的嵌套横断面研究中分析AIMS 1和AIMS 2中选定基因甲基化的患病率，并将在匹兹堡肺筛查研究(PLuSS)队列中验证甲基化患病率。目的4将确定与COPD相关的甲基化生物标志物是否显示随着时间的推移患病率增加，并预测肺功能的下降。将比较在3-4年内肺功能明显下降或无明显下降的参与者的甲基化患病率和甲基化指数。未来的研究将评估来自一项大型嵌套肺癌病例对照研究的受试者的痰中根据AIMS 3和4验证的基因，以确定它们对早期发生COPD和癌症检测的遗传和表观遗传风险谱的贡献。总而言之，这些研究的综合结果将为COPD与肺癌发展之间的联系提供新的见解。

DESCRIPTION (provided by applicant): Cigarette smoking is the main causative factor for Chronic Obstructive Pulmonary Disease (COPD) and lung cancer and the pathogenesis of these diseases is believed to be linked because individuals with COPD have a 2-4-fold higher risk of developing lung cancer. Epigenetic silencing of genes through promoter methylation of cytosines and histone modifications is now recognized as a major and causal event affecting expression of hundreds of genes during initiation and clonal development of lung cancer. Our initial nested, case-control study of incident cancer within a cohort of smokers with COPD showed that the concomitant methylation of three or more genes of a six gene panel was associated with a 6.5-fold increased risk for lung cancer. Extension of these studies in cancer-free smokers from the Lovelace Smokers Cohort (LSC) showed that a high methylation index (two or more genes methylated) and methylation of the p16 and GATA4 genes was associated with lower lung function. Studies also identified double-strand break repair capacity and specific genes within this pathway as determinants for gene methylation in sputum and that the proline variant at codon 72 of p53 is protective from mucous cell hyperplasia and decline of pulmonary function in the LSC. Based on these studies we hypothesize that the development of COPD mediated through tissue damage and remodeling will drive the epigenetic silencing of specific genes that in turn contribute to the development of lung cancer. The detection of these genes in sputum from smokers with COPD may provide new biomarkers for COPD development and progression, and early cancer detection. Aim 1 will identify and validate signatures for methylation as a function of COPD status by comparing the methylome in adenocarcinoma from patients with and without COPD and assess the association by genotype of p53 codon 72. Aim 2 will use primary human bronchial epithelial cells (BECs) from non smokers with the p53 codon 72 arginine versus proline genotype exposed chronically to cigarette smoke to identify genes and affected pathways with a focus on genes regulating tissue remodeling and apoptosis, and polycomb repressive complex 2 (PRC2) genes. Aim 3 will analyze the prevalence for methylation of selected genes from Aims 1 and 2 in a nested, cross-sectional study of 200 subjects with COPD and 400 controls from the LSC and the prevalence for methylation will be validated in Pittsburgh Lung Screening Study (PLuSS) Cohort. Aim 4 will determine whether methylation biomarkers found to be associated with COPD show increase in prevalence over time and predict for decline in pulmonary function. Methylation prevalence and methylation index among participants showing significant or no decline in pulmonary function over 3-4 years will be compared. Future studies will assess the genes validated under Aims 3 and 4 in sputum from subjects from a large nested lung cancer case-control study for their contribution to a developing genetic and epigenetic risk profile for early incident COPD and cancer detection. Together, the integrated results from these studies will provide novel insights into mechanisms that connect COPD to the development of lung cancer.