血小板反应蛋白1基因甲基化及其表达异常与鼻咽癌的关系

Correlation of promoter methylation and abnormal expression of THBS1 gene with nasopharyngeal carcinoma

目的探讨鼻咽癌组织中血小板反应蛋白1(thrombospondin 1,THBS1)基因启动子甲基化对其mRNA及蛋白水平表达的影响及与鼻咽癌临床病理特征的相关性。方法收集51例新鲜鼻咽癌标本及18例正常鼻咽黏膜标本。应用逆转录PCR检测THBS1 mRNA的表达,Western blot检测THBS1蛋白的表达,甲基化特异性PCR检测THBS1基因启动子区CpG岛甲基化。结果鼻咽癌组织中THBS1 mRNA(0.309±0.162)及蛋白(0.214±0.127)表达下调,与正常鼻咽黏膜组织对照组[分别为(0.528±0.096)、(0.514±0.118)]相比差异均具有统计学意义(P<0.01);鼻咽癌组织中基因启动子区高甲基化率显著高于其在正常鼻咽黏膜组织,差异有统计学意义(P<0.01)。鼻咽癌组织中THBS1 mRNA及蛋白表达下调均与THBS1基因启动子区高甲基化有关(P<0.01)。基因启动子区高甲基化率与鼻咽癌临床TNM分期、局部侵袭、淋巴结转移及远处转移呈正相关,差异均具有统计学意义(P<0.05)。结论鼻咽癌组织中存在THBS1 mRNA及蛋白异常低表达及启动子区的高甲基化,THBS1基因高甲基化可能抑制THBS1 mRNA及蛋白的表达,在鼻咽癌发生、发展中发挥重要作用。

Objective To determine the mRNA and protein expression of thrombospondin 1 （THBS1） and its aberrant DNA methylation in nasopharyngeal carcinoma （ NPC）, and then analyze the relationship of its aberrant DNA methylation with clinicopathological features of NPC. Methods A total of 51 NPC tissue samples and 18 normal nasopharyngeal （NNP） tissues were collected. The mRNA expression of THBS1 in NPC tissues and NNP tissues was detected by reverse-transcription polymerase chain reaction （RT-PCR）, and its protein expression was detected by Western blotting. The DNA methylation of the CpG island promoters of THBS1 in NPC tissues and NNP tissues was detected by the DNA methylation specific polymerase chain reaction. Results The mRNA and protein levels of THBS1 were significantly decreased in the NPC tissues than the NNP tissues （ P 〈 O. 01 ）. The positive rate of the hypermethylation of THBS1 gene was significantly higher in the NPC tissues than that the NNP tissues （ P 〈 0.01 ）. The decreased expression of THBS1 at mRNA and protein levels was associated with the hypermethylation of its gene promoter （ P 〈 0.01 ）. THBS1 gene hypermethylation status was positively correlated with NPC TNM staging, local invasion, lymphatic metastasis and distant metastasis （ each for P 〈 0.05 ）. Conclusion The aberrant hypermethylation of the CpG island promoter of THBS1 gene and their lower expression in NPC tissues may play a crucial role in carcinogenesis and development of NPC.