Department of Epidemiology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Carcinogenesis. 2011 Apr;32(4):507-15. doi: 10.1093/carcin/bgr014. Epub 2011 Feb 2.
Published genome-wide association studies (GWASs) have identified few variants in the known biological pathways involved in lung cancer etiology. To mine the possibly hidden causal single nucleotide polymorphisms (SNPs), we explored all SNPs in the extrinsic apoptosis pathway from our published GWAS dataset for 1154 lung cancer cases and 1137 cancer-free controls. In an initial association analysis of 611 tagSNPs in 41 apoptosis-related genes, we identified only 10 tagSNPs associated with lung cancer risk with a P value<10(-2), including four tagSNPs in DAPK1 and three tagSNPs in TNFSF8. Unlike DAPK1 SNPs, TNFSF8 rs2181033 tagged other four predicted functional but untyped SNPs (rs776576, rs776577, rs31813148 and rs2075533) in the promoter region. Therefore, we further tested binding affinity of these four SNPs by performing the electrophoretic mobility shift assay. We found that only rs2075533T allele modified levels of nuclear proteins bound to DNA, leading to significantly decreased expression of luciferase reporter constructs by 5- to -10-fold in H1299, HeLa and HCT116 cell lines compared with the C allele. We also performed a replication study of the untyped rs2075533 in an independent Texas population but did not confirm the protective effect. We further performed a mini meta-analysis for SNPs of TNFSF8 obtained from other four published lung cancer GWASs with 12 214 cases and 47 721 controls, and we found that only rs3181366 (r2=0.69 with the untyped rs2075533) was associated to lung cancer risk (P=0.008). Our findings suggest a possible role of novel TNFSF8 variants in susceptibility to lung cancer.
已发表的全基因组关联研究（GWAS）仅在肺癌病因学相关的已知生物学途径中发现了少数变异。为了挖掘潜在的因果单核苷酸多态性（SNP），我们从已发表的 1154 例肺癌病例和 1137 例无癌症对照的 GWAS 数据集中探索了外源性凋亡途径中的所有 SNP。在对 41 个凋亡相关基因中的 611 个标签 SNP 的初步关联分析中，我们仅发现 10 个标签 SNP 与肺癌风险相关，P 值<10(-2)，包括 DAPK1 中的 4 个标签 SNP 和 TNFSF8 中的 3 个标签 SNP。与 DAPK1 SNPs 不同，TNFSF8 rs2181033 标记了启动子区域中其他四个预测功能但未分型的 SNPs(rs776576、rs776577、rs31813148 和 rs2075533)。因此，我们通过进行电泳迁移率变动分析进一步测试了这四个 SNP 的结合亲和力。我们发现，只有 rs2075533T 等位基因改变了与 DNA 结合的核蛋白水平，导致 H1299、HeLa 和 HCT116 细胞系中荧光素酶报告基因构建体的表达显著降低 5 到 10 倍。我们还在德克萨斯州的一个独立人群中对未分型的 rs2075533 进行了复制研究，但未证实其保护作用。我们还对来自其他四个已发表的肺癌 GWAS 的 TNFSF8 SNPs 进行了小型荟萃分析，共纳入了 12214 例病例和 47721 例对照，结果发现只有 rs3181366（与未分型的 rs2075533 的 r2=0.69）与肺癌风险相关（P=0.008）。我们的研究结果表明，新型 TNFSF8 变体可能在肺癌易感性中起作用。
