人脑胶质瘤中EMP3和PCDH-γ-A11基因的甲基化调控

The methylation analysis of EMP3 and PCDH-γ-A11 gene in human glioma

目的研究胶质瘤中EMP3和PCDH-γ—A11基因的启动子甲基化与mRNA表达的关系，分析其在胶质瘤恶性进展中的启动子甲基化调控机制。方法使用甲基化PCR（MSP）检测EMP3和PCDH-γ-A11基因在胶质瘤、正常脑组织及胶质瘤细胞株中的基因启动子甲基化情况；Real—timePCR检测部分胶质瘤中两个基因的mRNA表达情况；统计学方法分析其基因启动子甲基化、mRNA表达及临床情况间的关系。检测去甲基化试剂5-Aza—CdR对U251和SHG-44细胞株中两个基因启动子甲基化和mRNA表达的影响。结果在88例胶质瘤中，EMP3基因启动子甲基化发生率为47．7％（42／88），其甲基化率随胶质瘤恶性程度的增加而增高；PCDH-γ-A11基因启动子甲基化发生率为86．4％（76／88），其甲基化率随胶质瘤恶性程度的增加而降低。各级别胶质瘤中EMP3和PCDH-γ-A11基因的mRNA表达与正常脑组织相比均下调（P〈0．01）。U251和SHG-44细胞株中均检测到EMP3和PCDH-γ-A11基因的启动子甲基化，并且5-Aza—CdR能重新激活两个基因的表达。结论胶质瘤中EMP3和PCDH-γ-A11基因启动子甲基化可能导致了其mRNA表达下调。EMP3和PCDH-γ-A11基因启动子甲基化可能成为胶质瘤恶性程度和预后评价的分子生物学标记，也可为胶质瘤的基因治疗提供新的靶点。

Objectives To study the relationship between promoter methylation and mRNA expressions of EMP3 and PCDH-γ-All genes in human glioma, and to analyze the regulation mechanism of promoter methylation in the progression of glioma. Methods The promoter metbylation of EMP3 and PCDH- γ-A11 was studied by a methylation specific PCR in 88 primary astrocytoma, 10 normal brain tissues and 2 glioma cell lines. The mRNA expressions were detected by real-time PCR in 30 primary glioma and 10 normal brain tissues. The correlations of their promoter methylation, mRNA expressions and clinicopathologic characteristics were analyzed. The promoter methylation were also detected in U251 and SHG-44 cell lines. Results The promoter methylation of EMP3 was dected in 42 tumors （47.7%） and the methylation of PCDH-γ-A11 was dected in 76 tumors （86. 4% ）. Their mRNA expressions were all significantly decreased in different pathological grade astrocytomas compared to the normal brain tissues （ P 〈 0. 01 ）. Their expressions were suppressed but could be reactivated by 5-aza-deoxycytidine in U251 and SHG-44 cell lines. Conclusions The promoter methylation of EMP3 and PCDH-γ-A11 genes may lead to the down- regulation of their mRNA levels in glioma. The promoter methylation and mRNA expressions of EMP3 and PCDH-γ-A11 are closely related with the maglinant development of glioma. The promoter methylation of the two genes may provide clues to evaluation of glioma malignancy as well as its prognosis. It also gives us an insight for future glioma medical therapy with a demethylating agent.