骨肉瘤组织MGMT基因甲基化状态的检测及其临床意义分析

Detection and clinical significance of methylated MGMT gene in osteosarcoma

目的探讨骨肉瘤组织O6-甲基鸟嘌呤-DNA甲基转移酶(MGMT)基因甲基化状态与MGMT蛋白表达及骨肉瘤化疗后肿瘤坏死率的关系。方法收集51例骨肉瘤组织样本,用甲基化特异性PCR(MSP)方法检测MGMT基因启动子区的甲基化状态,免疫组化方法检测MGMT蛋白的表达,并分析MGMT基因甲基化状态与肿瘤坏死率及临床病理资料的关系。结果 51例骨肉瘤组织MGMT基因启动子区甲基化发生率为23.5%(12/51),MGMT蛋白表达阴性率为27.5%(14/51);MGMT基因甲基化状态与骨肉瘤患者的年龄、性别、肿瘤大小、肿瘤类型等无明显关系(P>0.05)。MGMT基因甲基化的患者(共12例)化疗后肿瘤坏死率为Ⅰ级者0例,Ⅱ级者2例(16.7%),Ⅲ级者3例25.0%(25.0%),Ⅳ级者7例(58.3%),MGMT基因未甲基化的患者(共39例)化疗后肿瘤坏死率为Ⅰ级者23例(59.0%),Ⅱ级者13例(33.3%),Ⅲ级者2例(5.1%),Ⅳ级者1例(2.6%)。Wilcoxon秩和检验显示,骨肉瘤组织MGMT基因未甲基化患者的MGMT蛋白表达明显高于甲基化的患者(u=-4.92,P<0.001),而化疗后肿瘤坏死率明显低于甲基化的患者(P<0.05)。结论骨肉瘤组织MGMT基因甲基化状态对判断骨肉瘤患者化疗后的肿瘤坏死率具有重要意义。

Objective To investigate the relationship of MGMT （O-6-methylguanine-DNA methyltransferase） gene methylation with MGMT protein expression and tumor necrosis rate after chemotherapy in osteosarcoma patients. Methods Osteosarcoma tissues of 51 patients were collected,methylation of MGMT gene promoter was detected by methylation-specific PCR method,and protein expression of MGMT was examined by immunohistochemistry procedure,the relationship of MGMT gene methylation with tumor necrosis rate and clinicopathologic data of the patients were analyzed. Results The positive ratio of methylation MGMT gene promoter in 51 patients was 23.5% （12/51）. Negative percentage of MGMT protein expression was 27.4% （14/51）. No significant relationship was found between MGMT gene methylation in osteosarcoma tissues and the patient＇s age,sex,size and pathological types of neoplasms. After chemotherapy,the tumor necrosis rate of MGMT gene methylation patients from tumor grade Ⅰ to Ⅳ was 0% （0/12）,16.7% （2/12）,25.0% （3/12） and 58.3% （7/12）,respectively; in contrast,the tumor necrosis rate of MGMT gene unmethylation patients from tumor grade Ⅰ to Ⅳ was 59.0% （23/39）,33.3% （13/39）,5.1% （2/39） and 2.6% （1/39）,respectively. The results of Wilcoxon rank sum test showed the MGMT protein expression in MGMT gene unmethylation patients was significantly higher than that in MGMT gene methylation patients （u=-4.92,P0.001）,and the tumor necrosis rate after chemotherapy was lower than that in MGMT gene methylation patients （u=-4.92,P0.001）. Conclusions Methylation of MGMT gene promoter may play an important role in predicting the tumor necrosis rate after chemotherapy in osteosarcoma patients.