RASSF1A和p16转录本在非小细胞肺癌中的表达及启动子区甲基化

Transcriptional Expression and Promoter Hypermethylation of RASSF1A and p16 Gene in Non-small Cell Lung Cancer

目的研究RASSF1A和p16基因在国人非小细胞肺癌(NSCLC)组织中的转录及启动子区甲基化情况,探讨其转录失活的机制,为NSCLC的诊断和治疗寻找新的途径。方法应用半定量RT-PCR和甲基化特异性PCR法分析96例NSCLC及远癌正常肺组织中RASSF1A和p16基因mRNA的表达和启动子区甲基化情况。结果(1)53.12%(51/96)的NSCLC中RASSF1A表达明显下调或缺失;36.46%(35/96)的p16表达下调或缺失,而远癌正常肺组织均表达良好。(2)96例NSCLC中RASSF1A甲基化率48.96%(47/96),该基因表达明显下调或缺失的51例中39例(76.5%)出现甲基化,表达正常的45例中8例(17.8%)出现甲基化,两组对比差异有统计学意义(P<0.05);96例NSCLC中33例(34.38%)检测到p16启动子区甲基化,p16基因表达明显下调的35例中20例(57.1%)出现该基因CPG岛的甲基化,而表达正常的61例中13例(21.3%)出现甲基化,两组比较差异显著(P<0.05)。96例远癌正常肺组织均未检测到此两基因启动子有甲基化。结论RASSF1A和p16基因mRNA在国人NSCLC中较高比例的表达下调或缺失;甲基化可能是两基因表达失活的主要原因。

Objective To explore the transcriptional expression and the promoter hypermethylation of Ras association domain family 1A gene（RASSF1A） and p16 gene, and the major mechanisms for silencing of these two genes in non-small cell lung cancer（NSCLC） in Chinese. Methods RT-PCR and Methylationspecific PCR （MSP） was used to detect the transcriptional expression and aberrant methylation of RASSF1A and p16 gene in 96 human NSCLC tissues and matched 96 normal lung tissues far from cancer area. Results （1） The transcriptional expression of RASSF1A and p16 gene was normal in all normal lung tissues far from cancer area but low or loss in 53. 12%（51/96） carcinoma tissues for RASSF1A and in 36. 46%（35/96） carcinoma tissues for p16 gene. （2） Of the 96 NSCLC samples, methylation was detected in 48.96% for RASSF1A, 34.38% for p16. RASSF1A methylation was observed 39 of 51 （76. 5 %） in NSCLC samples with obvious down-regulation expression of RASSF1 A, 8 of 45 （17. 8% ） in cases in which the transcriptional expression of RASSF1A had no obvious change. The difference of two groups had statistical significance（P〈0. 05）. p16 gene promoter hypermethylation was found 20 of 35 （57. 1%） in cases with low or loss expression of p16 gene mRNA, 13 of 61 （21.3%） in cases in which transcriptional expression of p16 gene was normal. The difference of two groups had statistical signifi cance（P〈0. 05）. But no methylation was detected in 96 cancer-free tissues. Conclusion Loss or abnormal down-regulation of RASSF1A and p16 gene mRNA is a frequent event in patients with NSCLS in Chinese; The promoter hypermethylation of RASSF1A and p16 gene may be the major mechanisms for silencing of these two genes in NSCLC.