CHFR基因在鼻咽癌中异常甲基化的研究

Aberrant promoter hypermethylation of CHFR in nasopharyngeal carcinoma

目的:检测鼻咽癌中CHFR基因的转录表达及其启动子区甲基化状态,探讨其在鼻咽癌中的转录失活机制及其意义;评价鼻咽拭子检测CHFR基因甲基化状态在鼻咽癌诊断和治疗中的意义。方法:RT-PCR检测鼻咽癌细胞株中CHFR基因的转录表达水平。甲基化特异性PCR检测鼻咽癌细胞株、鼻咽癌活检组织、正常鼻咽组织及配套的鼻咽拭子样本中CHFR基因的甲基化状态。亚硫酸氢盐测序分析鼻咽癌细胞株和鼻咽癌组织、正常鼻咽组织中CHFR基因启动子区的具体甲基化状态。5-氮杂-2'-脱氧胞苷(5-aza-dC)处理鼻咽癌细胞株后观察CHFR基因转录表达水平的改变情况。结果:CHFR基因在鼻咽癌细胞株中转录表达下调或沉默;CHFR基因在鼻咽癌细胞株和鼻咽癌组织中均呈高频率、肿瘤特异性的甲基化。鼻咽癌患者鼻咽癌组织和配套鼻咽拭子样本中CHFR基因的甲基化频率分别为65.5%和63.8%,两者符合率达86.2%。鼻咽癌组织和细胞株中CHFR基因启动子区大部分的CpG位点为甲基化,而正常组织全为非甲基化;5-aza-dC可显著恢复鼻咽癌细胞株中CHFR基因的转录表达。结论:鼻咽癌中CHFR基因由于启动子区CpG岛的DNA甲基化而转录表达下调。鼻咽癌中CHFR基因的甲基化与患者T分期相关。检测鼻咽拭子中甲基化的CHFR基因可望作为鼻咽癌无创诊断的手段之一。

Objective：To discover the relationship of transcriptional levels and promoter methylation status of CHFR gene in human nasopharyngeal carcinoma,to discuss the significance and epigenetic mechanism of CHFR inactivation in NPC,and to evaluate the feasibility of detecting methylated CHFR in nasopharyngeal swab as a means for diagnosis of NPC.Method：Transcriptional levels of CHFR was evaluated by RT-PCR.Methylation specific PCR was used to detect the methylation status of CHFR in NPC cells,normal nasopharyngeal epithelia,primary tumors and their paired nasopharyngeal swabs.Detailed methylation status was confirmed by bisulfite sequencing.NPC cells were treated by the methyaltransfrase inhibitor 5-aza-dC and the reactivation of CHFR was evaluated by RT-PCR.Result：CHFR transcription was inactivated in NPC.The methylation frequency in NPC primary tumors and their paired swabs were 65.5% and 63.8%,respectively,with a 86.2% concordance.Bisulfite sequencing revealed a dense methylation in NPC cells and primary tumors,but all the normal nasopharyngeal epithelia were unmethylated.CHFR expression were restored after 5-aza-dC treatment.Conclusion：CHFR is epigenetically inactivated by promoter methylation in NPC.Detecting methylated CHFR can be served as a useful non-invasive means for diagnosis of NPC.