胶质母细胞瘤MGMT基因启动子甲基化与蛋白表达

Heterogeneity of O6-methylguanine-DNA methyltransferase protein expression and gene promoter methylation in glioblastoma

目的 研究新发胶质母细胞瘤中肿瘤不同部位MGMT基因启动子甲基化及其蛋白表达关系及区域差异性.方法 在30例新发胶质母细胞瘤肿瘤不同部位采取2～4块标本,其中5例在术中神经导航引导下采取.甲基化特异性PCR（MSP）法检测标本中MGMT基因启动子甲基化状况,免疫组化法（IHC）检测组织切片MGMT蛋白表达情况.结果 43.56%（44/101）检测肿瘤组织中出现MGMT基因启动子甲基化,免疫组化检测（阴性,细胞弱着色＜10%或细胞无着色;弱阳性,10%≤细胞着色≤50%;强阳性,细胞着色＞50%）发现MGMT蛋白表达情况分别为阴性（32.67%）,弱阳性（43.56%）,强阳性（23.76%）.MGMT基因启动子甲基化与其蛋白表达无明显相关性（x2=2.905,P=0.088）.在肿瘤不同取材部位组织之间57%的患者（17/30）MGMT蛋白表达水平与37%患者（11/30）启动子甲基化存在不均一性.结论 MGMT基因启动子甲基化可能不是MGMT蛋白表达的惟一调节因素.同一肿瘤不同取材部位组织MGMT蛋白表达与其基因启动子甲基化水平不均一性的结果 质疑了单一取材标本的检测结果 及其对临床治疗方案选择的指导意义.

Objective To study the correlation of MGMT gene promoter methylation and protein expression and their regional variation in different specimens obtained from different regions within the tumor in patients with newly diagnosed glioblastoma. Methods Two to four samples in the same tumor were collected from different regions in 30 patients with newly diagnosed glioblastoma patients. In five patients among them,mutispecimens were obtained under assistance of neuronavigation system during the operation. In all samples,MGMT promoter profile were analyzed by Methylation - specific polymerase - Chain - reaction analysis, MSP ,while MGMT protein expression was detected in tissue sections by immunohistochemistry,IHC. Results MGMT promoter methylation was detected in 43. 56% （44/101） specimens. MGMT protein expression in tissue sections was assessed and scored：（1 ：no or positive tumor cells 〈 10%, 2： ≥ 10% ≤50% ,3： 〉 50%） ,The rate of MGMT staining with a score 1,2,3 in all of tumor sections was 32. 67% ,43.56% ,23. 76% respectively. No significant correlation between MGMT protein expression and promoter methylation（x2 =2. 905, P =0.088） was found. The regional heterogeneity of MGMT protein expression within the same tumor was in 57% （17/30） patients ;and the regional heterogeneity of gene promoter methylation was in37%（11/30）patients. Conclusions MGMT promoter methylation is probably not the only modulating element in MGMT protein expression. The heterogeneity of MGMT protein expression and its promoter methylation in the same tumor questions their guiding significance in making therapeutic scheme for individual patients with malignant glioma in clinical practice.