鼻咽癌细胞中上皮细胞钙黏蛋白基因启动子甲基化的研究

目的 探讨鼻咽癌细胞中上皮细胞钙黏蛋白(E-cadherin)启动子甲基化对基因表达的影响,以及经去甲基化药物5-杂氮-2'-脱氧胞苷(5-Aza-dC)作用后肿瘤细胞增殖与侵袭能力的变化.方法采用逆转录(RT)-PCR、Western blot与免疫组织化学(polymer法)检测经5-Aza-dC处理前后HNE1和CNE2细胞中E-cadherin的表达水平,以甲基化特异性PCR(MSP)分析启动子甲基化状态,以四甲基偶氮唑盐(MTT)比色法与侵袭实验测定细胞增殖与侵袭能力的变化.结果 HNE1和CNE2细胞中E-cadherin表达水平减弱,其启动子区域存在部分甲基化现象;经5-Aza-dC作用后可显著上调鼻咽癌细胞E-cadherin的表达水平,降低基因启动子甲基化程度,同时显著抑制肿瘤细胞的增殖能力与侵袭能力.经20 μmol/L 5-Aza-dC作用后,HNE1与CNE2细胞的增殖能力与未处理组相比分别降低27.6%和34.3%,P＜0.05;HNE1与CNE2细胞经5-Aza-dC药物处理后,通过滤膜迁移进至侵袭小室下腔的数量与未处理组相比分别减少37.2%和29.7%,P＜0.05.结论基因启动子区域高甲基化状态是导致E-cadherin表达水平下调的机制之一,应用去甲基化药物可恢复E-cadherin表达并抑制肿瘤细胞的恶性生物学特征.

Study on promoter methylation status of E-cadherin gene in nasopharyngeal carcinoma cell lines

Objective To investigate the role of methylation on E-cadherin inactivation in nasopharyngeal carcinoma (NPC) cell line HNE1 and CNE2, as well as evaluate the inhibitory effect of 5-aza-2'-deoxycytidine (5-Aza-dC) on cell abilities of proliferation and invasion. Methods The expression level of E-cadherin was measured by RT-PCR, Western blot and immunohistochemistry ( polymer method),the methyaltion status was analyzed by methylation-specific PCR ( MSP), and cell proliferation and invasion were examined by MTT and invasion assay, separately before and after treatment with demethylating agent 5-Aza-dC. Results The expression level of E-cadherin was down-regulated compared with the normal tissue,simultaneously partially methylated in gene promoter. Treatment with 20 μmol/L 5-Aza-dC increased the expression of E-cadherin and reduced the methylation degree. Moreover, it also significantly suppressed cell growth (27.6% for HNE1 cells and 34.3% for CNE2 cells, P ＜0.05) and invasiveness (37. 2% for HNE1cells and 29.7% for CNE2 cells, P ＜ 0.05). Conclusions Aberrant methylation around gene promoter region may play an important part in down regulation of E-cadherin in NPC, suggesting a potential therapeutic strategy for demethylating agents such as 5-Aza-dC.