上皮型钙黏素基因启动子甲基化和β-链接素基因突变对鼻咽癌细胞侵袭转移的影响

目的　检测鼻咽原发癌和淋巴结转移癌组织中上皮型钙黏素基因启动子的甲基化和 β 链接素基因第 3外显子的突变 ,探讨鼻咽癌癌细胞早期发生组织侵袭和淋巴结转移的机制。方法采用DNA甲基化特异性聚合酶链反应、DNA直接测序法和免疫组化法 ,检测 2 1例鼻咽原发癌组织和 2 1例淋巴结转移癌组织中上皮型钙黏素基因启动子的甲基化程度、β 链接素基因第 3外显子的点突变以及 β 链接素蛋白的表达差异性。结果　 (1) 2 1例鼻咽原发癌组织中 ,2 3.8% (5 2 1)的病例可以检测到上皮型钙黏素基因启动子的甲基化 ,而在 2 1例淋巴结转移癌组织中则有 6 1.9% (13 2 1) ,二者差异有显著性 (P <0 .0 1)。 (2 ) 4 2例癌组织中 ,仅有 3例 (7.1% )检测到 β-链接素第 3外显子的 3处点突变 ,分别为密码子 37(TCT→GCT)、密码子 4 1(ACC→GCC)和密码子 4 7(AGT→ACT) ,但与癌细胞的侵袭转移无相关性 (P >0 .0 5 )。 (3) β 链接素蛋白在鼻咽原发癌和淋巴结转移癌组织中均有较高的表达量 ,其表达部位均为胞膜 ,未见到胞核表达者 (P >0 .0 5 )。结论　 (1)鼻咽癌组织中 ,上皮型钙黏素基因启动子的甲基化是导致上皮型钙黏素表达下调的主要原因 ,也可能是最终造成癌细胞分离移动的决定因素。 (2 ) β 链接素基因第 3外显子的突

Influence of E-cadherin promoter methylation and mutation of beta-catenin on invasion and metastasis of nasopharyngeal carcinoma cells

OBJECTIVE: To study the mechanism of invasion and metastasis in early nasopharyngeal carcinoma (NPC) in relation to E-cadherin promoter methylation and mutation in exon 3 of beta-catenin. METHODS: Methylation of E-cadherin promoter, mutation in exon 3 of beta-catenin and differential expression of beta-catenin in the primary lesion of 21 NPC and the metastatic lymph node of 21 NPC were investigated by DNA Methylation-Specific PCR, direct sequencing and immunohistochemical method. RESULTS: Methylation on E-cadherin promoter was showed in 23.8% (5/21) primary lesions and 61.9% (13/21) metastatic lymph nodes (P < 0.01). Mutation in exon 3 of beta-catenin was showed in 3 of 42 tissues: codon 37 (TCT-->GCT), codon 41 (ACC-->GCC) and codon 47 (AGT-->ACT). However, there was no relation between these mutations and invasion or metastasis (P > 0.05). High beta-catenin expression on the membrane without nuclear expression was observed in 42 tissues (P > 0.05). CONCLUSION: 1. In NPC, methylation of promoter is a major cause of down-regulation of E-cadherin which may finally lead to detachment and metastasis of neoplastic cells, 2. Mutation in exon 3 of beta-catenin is a rare event in NPC. It may be an early event in the carcinogenesis of NPC but have no significant role in invasion and metastasis and 3. High expression of beta-catenin, as one of NPC characteristics, is not a key factor for invasion or metastasis.