Li Zhi, Lin Su-xia, Liang Ying-jie
Department of Pathology, Sun Yat-sen Medical College, Sun Yat-sen University, Guangzhou 510089, China.
Zhonghua Bing Li Xue Za Zhi. 2003 Feb;32(1):25-30.
To detect the gene promoter methylation, mRNA and protein expression levels of E-cadherin and beta-catenin in primary and metastatic tumor samples of nasopharyngeal carcinoma (NPC), and to investigate the mechanism of invasion and metastasis of neoplastic cell in NPC.
Twenty-one patients with NPC were studied. The samples of primary tumor and paired lymph node metastatic tumor were collected and examined for aberrant gene promoter methylation in E-cadherin by DNA Methylation-specific polymerase chain reaction (MSP). Reverse transcriptase polymerase chain reaction (RT-PCR), Western blotting and immunohistochemical staining were adopted to detect mRNA and protein levels of E-cadherin and beta-catenin.
(1) The gene promoter methylation in E-cadherin was 52.4% (11/21) in primary tumor of NPC, and 80.9% (17/21) in lymph node metastatic tumor, which existed significant difference (P < 0.05). (2) In primary tumor, about 80% (0 approximately 100%) neoplastic cells expressed E-cadherin protein on the average, which was significantly higher than that of metastatic tumor (50% on the average, P = 0.004). The expression levels of beta-catenin protein were high in both primary and metastatic tumors, but with no statistic difference (P = 0.698). (3) By Western blotting analysis, the relative intensity of protein expression in E-cadherin was significantly higher in primary tumor (206.7 +/- 32.7) compared to that of metastatic tumor (65.0 +/- 15.9), while the expression of beta-catenin protein showed no difference between them (P = 0.754). (4) mRNA expression level of E-cadherin was higher in primary tumor than that of metastatic tumor.No remarkable difference was found for the mRNA expression of beta-catenin.
(1) Downregulation of mRNA and protein expression of E-cadherin may play a critical role in neoplastic cell invasion and metastasis in NPC. The aberrant promoter methylation of E-cadherin may ultimately alter the mobility and scattering of tumor cells in NPC. (2) Downregulation of E-cadherin alone may be enough for the tumor cell to lose intercellular adhesions which results in tumor cell invasion and metastasis. However, mutant beta-catenin could also involve in this progress. (3) The detection of gene promoter hypermethylation of E-cadherin should be evaluated in the screening and surveillance of NPC.
检测鼻咽癌（NPC）原发肿瘤及转移瘤组织中E-钙黏蛋白和β-连环蛋白基因启动子甲基化、mRNA及蛋白表达水平，探讨NPC肿瘤细胞侵袭转移机制。
对21例NPC患者进行研究。收集原发肿瘤及配对淋巴结转移瘤组织样本，采用DNA甲基化特异性聚合酶链反应（MSP）检测E-钙黏蛋白基因启动子异常甲基化情况。采用逆转录聚合酶链反应（RT-PCR）、蛋白质免疫印迹法（Western blotting）及免疫组织化学染色检测E-钙黏蛋白和β-连环蛋白的mRNA及蛋白水平。
（1）NPC原发肿瘤组织中E-钙黏蛋白基因启动子甲基化率为52.4%（11/21），淋巴结转移瘤组织中为80.9%（17/21），差异有统计学意义（P<0.05）。（2）原发肿瘤组织中，约80%（0～100%）肿瘤细胞平均表达E-钙黏蛋白，显著高于转移瘤组织（平均50%，P=0.004）。原发肿瘤和转移瘤组织中β-连环蛋白蛋白表达水平均较高，但差异无统计学意义（P=0.698）。（3）蛋白质免疫印迹法分析显示，原发肿瘤组织中E-钙黏蛋白蛋白表达相对强度（206.7±32.7）显著高于转移瘤组织（65.0±15.9），而β-连环蛋白蛋白表达无差异（P=0.754）。（4）原发肿瘤组织中E-钙黏蛋白mRNA表达水平高于转移瘤组织，β-连环蛋白mRNA表达无显著差异。
（1）E-钙黏蛋白mRNA及蛋白表达下调可能在NPC肿瘤细胞侵袭转移中起关键作用。E-钙黏蛋白启动子异常甲基化可能最终改变NPC肿瘤细胞的迁移和扩散。（2）单独E-钙黏蛋白下调可能足以使肿瘤细胞丧失细胞间黏附，导致肿瘤细胞侵袭转移。然而，突变的β-连环蛋白也可能参与这一过程。（3）E-钙黏蛋白基因启动子高甲基化检测应在NPC的筛查和监测中进行评估。
