Leng Shuguang, Liu Yushi, Weissfeld Joel L, Thomas Cynthia L, Han Younghun, Picchi Maria A, Edlund Christopher K, Willink Randall P, Gaither Davis Autumn L, Do Kieu C, Nukui Tomoko, Zhang Xiequn, Burki Elizabeth A, Van Den Berg David, Romkes Marjorie, Gauderman W James, Crowell Richard E, Tesfaigzi Yohannes, Stidley Christine A, Amos Christopher I, Siegfried Jill M, Gilliland Frank D, Belinsky Steven A
: Lung Cancer Program, Lovelace Respiratory Research Institute, Albuquerque, NM (SL, YL, CLT, MAP, RPW, KCD, XZ, EAB, YT, SAB); Department of Epidemiology, Graduate School of Public Health (JLW) and Department of Medicine (TN, MR), University of Pittsburgh, Pittsburgh, PA; Center for Genomic Medicine, Department of Community and Family Medicine, Geisel School of Medicine, Dartmouth College, Hanover, NH (YH, CIA); Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA (CKE, DVDB, WJG, FDG); Department of Pharmacology & Chemical Biology, Hillman Cancer Center of the University of Pittsburgh Medical Center, Pittsburgh, PA (ALGD, JMS); Department of Internal Medicine, University of New Mexico, Albuquerque, NM (REC, CAS); Department of Pharmacology, University of Minnesota, Minneapolis, MN (JMS).
J Natl Cancer Inst. 2015 Feb 23;107(5):djv035. doi: 10.1093/jnci/djv035.
Lung cancer is the leading cause of cancer-related mortality worldwide. Detection of promoter hypermethylation of tumor suppressor genes in exfoliated cells from the lung provides an assessment of field cancerization that in turn predicts lung cancer. The identification of genetic determinants for this validated cancer biomarker should provide novel insights into mechanisms underlying epigenetic reprogramming during lung carcinogenesis.
A genome-wide association study using generalized estimating equations and logistic regression models was conducted in two geographically independent smoker cohorts to identify loci affecting the propensity for cancer-related gene methylation that was assessed by a 12-gene panel interrogated in sputum. All statistical tests were two-sided.
Two single nucleotide polymorphisms (SNPs) at 15q12 (rs73371737 and rs7179575) that drove gene methylation were discovered and replicated with rs73371737 reaching genome-wide significance (P = 3.3×10(-8)). A haplotype carrying risk alleles from the two 15q12 SNPs conferred 57% increased risk for gene methylation (P = 2.5×10(-9)). Rs73371737 reduced GABRB3 expression in lung cells and increased risk for smoking-induced chronic mucous hypersecretion. Furthermore, subjects with variant homozygote of rs73371737 had a two-fold increase in risk for lung cancer (P = .0043). Pathway analysis identified DNA double-strand break repair by homologous recombination (DSBR-HR) as a major pathway affecting susceptibility for gene methylation that was validated by measuring chromatid breaks in lymphocytes challenged by bleomycin.
A functional 15q12 variant was identified as a risk factor for gene methylation and lung cancer. The associations could be mediated by GABAergic signaling that drives the smoking-induced mucous cell metaplasia. Our findings also substantiate DSBR-HR as a critical pathway driving epigenetic gene silencing.
肺癌是全球癌症相关死亡的主要原因。检测肺癌脱落细胞中肿瘤抑制基因的启动子高甲基化可评估场癌化，进而预测肺癌。确定这种经过验证的癌症生物标志物的遗传决定因素，应能为肺癌发生过程中表观遗传重编程的潜在机制提供新的见解。
在两个地理位置独立的吸烟者队列中进行了一项全基因组关联研究，使用广义估计方程和逻辑回归模型来识别影响癌症相关基因甲基化倾向的基因座，该倾向通过痰液中检测的12个基因的基因panel进行评估。所有统计检验均为双侧检验。
发现了位于15q12的两个单核苷酸多态性（SNP）（rs73371737和rs7179575）可驱动基因甲基化，并在另一个队列中得到重复验证，其中rs73371737达到全基因组显著性水平（P = 3.3×10⁻⁸）。携带来自两个15q12 SNP风险等位基因的单倍型使基因甲基化风险增加57%（P = 2.5×10⁻⁹）。Rs73371737降低了肺细胞中GABRB3的表达，并增加了吸烟诱导的慢性黏液高分泌风险。此外，rs73371737变异纯合子的受试者患肺癌的风险增加了两倍（P = 0.0043）。通路分析确定同源重组DNA双链断裂修复（DSBR-HR）是影响基因甲基化易感性的主要通路，通过测量博来霉素刺激的淋巴细胞中的染色单体断裂得到验证。
一个功能性的15q12变异被确定为基因甲基化和肺癌的危险因素。这些关联可能由驱动吸烟诱导的黏液细胞化生的GABA能信号介导。我们的研究结果还证实DSBR-HR是驱动表观遗传基因沉默的关键通路。
