髓母细胞瘤与幕上原始神经外胚叶肿瘤中RASSF1A基因的甲基化差异  

Different hypermethylation status of RASSF1A in medulloblastoma and supratentorial primitive neuroectodermal tumor

作　　者：常青[1] 吴浩强[2] 

机构地区：[1]北京大学医学部病理系,100083 [2]香港中文大学威尔斯亲王医院病理解剖及细胞学系

出　　处：《中华病理学杂志》2007年第1期24-28,共5页Chinese Journal of Pathology

摘　　要：目的通过研究髓母细胞瘤与幕上原始神经外胚叶肿瘤(SPNET)中 RASSF1A 基因的甲基化改变,探讨颅内原始神经外胚叶肿瘤(PNET)的不同亚型中该基因的表遗传学差异及其意义。方法收集25例原发髓母细胞瘤,9例原发 SPNET,3株髓母细胞瘤细胞系和2株 SPNET 细胞系。采用甲基化特异性聚合酶链反应(MSP)检测 RASSF1A 基因启动子区的甲基化状态。应用去甲基化试剂5-aza-2′deoxycytidine 处理存在基因表达缺失的细胞系,探讨基因表达与甲基化之间的关系。结果100%(25/25)的原发髓母细胞瘤、6/9的原发 SPNET 及全部 PNET 细胞系中均检测到RASSFIA 基因的甲基化。相反,该基因甲基化在全部正常组织(包括2例小脑,5例大脑)中均未检测到。并且,RASSF1A 在 SPNET 中的甲基化率明显低于髓母细胞瘤(Fisher 精确检验,P=0.014)。在经去甲基化试剂处理的 PNET 细胞中,该基因表达得以恢复,证明甲基化与该基因沉默相关。结论RASSF1A 甲基化是肿瘤特异性的,RASSF1A 甲基化与 PNET 的发生有一定关联,不同亚型的 PNET 之间 RASSF1A 基因的不同甲基化状态提示髓母细胞瘤和 SPNET 是表遗传学上存在差异的两类肿瘤。Objective To investigate the epigenetic involvement of RASSF1A in intracranial primitive neuroectodermal tumors （PNETs） and compare the methylation patterns between medulloblastoma （MBs） and supratentorial PNETs （ SPNETs ）. Methods The methylation status at the promoter regions of RASSF1A was examined by methylation-specific polymerase chain reaction （MSP） in a cohort of 25 primary MBs, 9 primary SPNETs, 3 MB and 2 SPNET cell lines. RASSF1A-deficient PNET cell lines were treated with 5-aza-2＇deoxycytidine, a demethylating agent, to explore the relationship between hypermethylation and the gene expression. Results The results revealed no promoter hypermethylation of RASSF1A in 2 normal cerebellar and 5 normal cerebral tissue specimens examined. In contrast, promoter hypermethylation of RASSF1A was detected in 100% （25/25）of primary MBs, 6/9 of primary SPNETs, and all PNET cell lines. These results demonstrated that such epigenetic alteration was tumor-specific. The frequency of hypermethylation of RASSF1A in SPNETs was also found to be significantly lower than that in MBs （ Fisher＇s exact test, P = 0. 014）. Treatment of RASSF1A-deficient PNET cell lines with 5-aza-2＇ deoxycytidine restored RASSF1A expression, providing evidence that promoter hypermethylation contributes to transcriptional silencing. Conclusions These results demonstrate that RASSF1A plays an important role in the development of intracranial PNETs. Different hypermethylation status of RASSF1A are found in PNET subtypes suggesting that MBs and SPNETs are epigenetical distinct tumors.

关 键 词：髓母细胞瘤 神经外胚瘤 原始 DNA甲基化 RASSF1A 

分 类 号：R739.4[医药卫生—肿瘤]