Izumi Hiroyuki, Inoue Jun, Yokoi Sana, Hosoda Hiroshi, Shibata Tatsuhiro, Sunamori Makoto, Hirohashi Setsuo, Inazawa Johji, Imoto Issei
Department of Molecular Cytogenetics, Medical Research Institute and School of Biomedical Science, Tokyo Medical and Dental University, Tokyo 113-8510, Japan.
Hum Mol Genet. 2005 Apr 15;14(8):997-1007. doi: 10.1093/hmg/ddi092. Epub 2005 Mar 3.
Genome-wide screening of DNA copy number aberrations in 27 cell lines derived from non-small cell lung cancers (NSCLCs), using a custom-made comparative genomic hybridization (CGH)-array, identified a homozygous deletion of the deleted in bladder cancer 1 gene (DBC1) in one cell line. Homozygous deletion of DBC1, located at 9q33.1, was also observed in two of 53 primary NSCLC tumors examined. Moreover, 21 of the other 26 cell lines showed complete loss of DBC1 expression, although normal lung tissues express this gene, and treatment with 5-aza-2'-deoxycytidine restored expression of DBC1. Hypermethylation in part of a CpG island around the exon 1 of DBC1 has been reported in urothelial cancers, but the potential association between methylation and expression status was never clarified in that disease. In our experiments, a different part of the same CpG island showed promoter activity in vitro and was frequently methylated in our cell lines and primary tumors of NSCLC, where methylation status correlated inversely with gene expression. Among our primary NSCLC cases, methylation of the DBC1 promoter occurred more frequently in men, elderly patients and smokers than in women, younger patients and nonsmokers respectively, but it was not correlated with tumor stage or histology. Exogenous overexpression of DBC1 in NSCLC cell lines lacking its expression inhibited cell growth. Our results provide the first evidence that DBC1 is a likely tumor suppressor for NSCLC; silencing of the gene through homozygous deletion or methylation of its promoter region may be associated with progression of this disease.
使用定制的比较基因组杂交（CGH）阵列对27个源自非小细胞肺癌（NSCLC）的细胞系进行全基因组DNA拷贝数畸变筛查，在一个细胞系中发现膀胱癌缺失基因1（DBC1）存在纯合缺失。在所检测的53例原发性NSCLC肿瘤中，也有2例观察到位于9q33.1的DBC1纯合缺失。此外，尽管正常肺组织表达该基因，但在其他26个细胞系中的21个显示DBC1表达完全缺失，用5-氮杂-2'-脱氧胞苷处理可恢复DBC1的表达。尿路上皮癌中已报道DBC1外显子1周围部分CpG岛存在高甲基化，但在该疾病中甲基化与表达状态之间的潜在关联从未得到阐明。在我们的实验中，同一CpG岛的不同部分在体外显示出启动子活性，并且在我们的NSCLC细胞系和原发性肿瘤中经常发生甲基化，其中甲基化状态与基因表达呈负相关。在我们的原发性NSCLC病例中，DBC1启动子的甲基化在男性、老年患者和吸烟者中分别比女性、年轻患者和非吸烟者更频繁发生，但与肿瘤分期或组织学无关。在缺乏DBC1表达的NSCLC细胞系中外源性过表达DBC1可抑制细胞生长。我们的结果提供了首个证据，表明DBC1可能是NSCLC的肿瘤抑制因子；该基因通过纯合缺失或其启动子区域的甲基化而沉默可能与该疾病的进展有关。
