错配修复基因启动子甲基化和蛋白表达在葡萄胎的发生及恶变中的作用

目的探讨错配修复基因hMLH1和hMSH2启动子甲基化和蛋白表达在葡萄胎的发生及恶变中的作用.方法用甲基化敏感性核酸内切酶HpaⅡ酶切-PCR法,分析正常早孕人流绒毛、部分性葡萄胎(PM)、完全性葡萄胎(CM)和侵蚀性葡萄胎(IM)hMLH1和hMSH2启动子甲基化情况;免疫组化检测hMLH1和hMSH2原位蛋白表达.结果在正常早孕绒毛、PM、CM和IM组织中,hMLH1和hMSH2均表达于细胞滋养细胞,合体滋养细胞大多表达阴性,极少数为弱阳性.正常早孕绒毛组织均未发现hMLH1和hMSH2启动子甲基化,而hMLH1和hMSH2表达全部阳性,阳性率为100%,与PM、CM组织相比,启动子甲基化和蛋白表达均存在显著性差异(P＜0.05).IM中hMLH1和hMSH2启动子甲基化发生率分别为80.0%(12/15)和73.3%(11/15),与PM、CM相比无显著性差异(P＞0.05);IM hMLH1蛋白表达阳性率为54.5%(6/11),与PM、CM相比无显著性差异(P＞0.05);而hMSH2蛋白表达阳性率为36.4%(4/11),明显弱于CM,两者比较有显著性差异(P=0.044).CM和IM组织中hMSH2启动子甲基化与其蛋白表达间存在相关性(P值分别=0.001和0.039).结论hMLH1和hMSH2的高表达对正常细胞滋养细胞基因组的稳定性起着重要的作用;hMLH1和hMSH2启动子甲基化的发生和蛋白表达的缺失参与了葡萄胎的发生.

Mismatch repair gene promoter methylation and expression in hydatidiform moles and the malignant transformation

OBJECTIVE: In this study, we assayed promoter hypermethylation and protein expression of the mismatch repair gene (MMR) hMLH1 and hMSH2 in gestational trophoblastic diseases to understand the significance of MMR promoter methylation and expression in the pathogenesis and malignant transformation of hydatidiform mole. METHODS: DNA was extracted from chorion of early pregnancies, partial hydatidiform moles, complete hydatidiform moles, and invasive moles were over digested by methylation sensitive endonuclease Hpa II. Then the promoters were amplificated by polymerase chain reaction. The protein was detected by immunohistochemistry. RESULTS: In the normal placenta, neither hMLH1 nor hMSH2 promoter methylation was detected. Expression of hMLH1 and hMSH2 in cytotrophoblasts was strongly positive, and that was negative or weakly positive in syncytiotrophobasts. In all normal chorion, expression of hMLH1 and hMSH2 in cytotrophoblasts was strongly positive. In partial hydatidiform mole and complete hydatidiform mole, the methylation of hMLH1 and hMSH2 promoters was significantly higher than that of early placenta (P < 0.05), and the protein expression in cytotrophoblasts was significantly lower (P < 0.05). In the invasive mole, hMLH1 and hMSH2 promoter methylation were not significantly different as compared with the partial hydatidiform mole and complete hydatidiform mole (P > 0.05). Expression of hMLH1 in the invasive mole (54.5%, 6/11) was not significantly different as compared with the partial hydatidiform mole and complete hydatidiform mole (P > 0.05). But expression of hMSH2 in the invasive mole (36.4%, 4/11) was weaker than that in complete hydatidiform mole (P = 0.044). Promoter methylation and less expression of hMSH2 had correlations in complete hydatidiform mole or invasive mole. CONCLUSIONS: Strong expressions of hMLH1 and hMSH2 in the cytotrophoblasts of normal placenta may keep the genome stability. Promoter methylation and down-regulation of hMLH1 and hMSH2 are probably involved in the pathogenesis of hydatidiform mole.