食管鳞癌中DACT2基因表达及甲基化状态研究

Expression and Methylation Status of DACT2 Gene in Esophageal Squamous Cell Carcinoma

[目的]检测食管鳞状细胞癌(ESCC)中DACT2基因表达及启动子区甲基化状态,探讨DACT2基因在食管鳞癌发生发展中的作用。[方法]分别应用逆转录—聚合酶链反应(RTPCR)以及甲基化特异性PCR(MSP)的方法检测DNA甲基转移酶抑制剂5-氮杂-2′-脱氧胞苷(5-aza-d C)处理前后的食管癌细胞系(TE1、TE13、T.Tn、Eca109)以及食管鳞癌组织及相应癌旁组织中DACT2 m RNA表达情况及启动子区甲基化状态。[结果]经5-aza-d C处理后4种食管癌细胞系中DACT2基因的表达均增高。4种未经5-aza-d C处理的食管癌细胞系中DACT2基因呈高甲基化状态。应用5-aza-d C处理后,DACT2基因在4种细胞系中均呈非甲基化状态。DACT2基因在食管鳞癌组织中的表达显著低于癌旁组织(0.66±0.53 vs 0.95±0.64,t=-2.43,P=0.018),并与淋巴结转移密切相关(t=-2.030,P=0.048)。食管鳞癌组织中DACT2基因的启动子区甲基化率显著高于癌旁组织(50.0%vs 21.1%,χ2=9.439,P=0.002),并与TNM分期、组织学分化程度和淋巴结转移密切相关(P均<0.05)。发生DACT2基因甲基化的食管鳞癌组织中DACT2基因的表达量显著低于未发生甲基化的食管鳞癌组织(0.46±0.32 vs 0.78±0.61,t=-2.341,P=0.023)。[结论 ]DACT2基因在食管鳞癌中的异常低表达与食管鳞癌的发生、发展密切相关,且其启动子区甲基化可能是导致其表达沉默的机制之一。

[Purpose] To investigate the expression and methylation status of DACT2 gene in esophageal squamous cell carcinoma（ESCC）. [Methods] The m RNA expression and methylation status of DACT2 gene in esophageal cancer cell lines（TE1,TE13,T.TN,Eca109） treated or untreated with DNA methyltransferase inhibitor 5-aza-2′-detoxycytidine（5-aza-d C）,and in ESCC tissues and corresponding non-cancerous tissues were detected by reverse transcription polymerase chain reaction（RT-PCR） and methylation specific PCR（MSP）,respectively. [Results] Relatively low expression and hypermethylation of DACT2 was detected in 4 esophageal cancer cell lines untreated with 5-aza-d C. After treatment with 5-aza-d C,the expression of DACT2 was enhanced,and the methylation status of DACT2 was reversed in esophageal cancer cell lines. The expression of DACT2 in ESCC tumor tissues was significantly reduced compared to corresponding non-cancerous tissues（0.66±0.53 vs 0.95±0.64,t=-2.43,P=0.018）,and was associated with lymph node metastasis（t=-2.030,P=0.048）. The methylation frequency of DACT2 promoter in ESCC tissues was significantly higher than that in corresponding normal tissues（50.0% vs 21.1%,χ2=9.439,P=0.002）,and was associated with TNM stage,pathological differentiation and lymph node metastasis（all P〈0.05）. The expressions of DACT2 in ESCC tumor tissues with methylation of the gene was significantly lower than that in tumor tissues with unmethylation of the gene（0.46 ±0.32 vs 0.78±0.61,t=-2.341,P=0.023）.[Conclusion] Aberrant low expression of DACT2 is closely related to the occurrence and development of ESCC,and promoter methylation may be one of the mechanisms for inactivation of DACT2 in ESCC.