Rb基因在肝细胞癌中的多种失活机制

MULTIPLE MECHANISMS OF Rb GENE INACTIVATION IN HEPATOCELLULAR CARCINOMA

目的:检测肝细胞癌 Rb 抑癌基因失活的多种机制。方法:采用多聚酶链反应—限制性片段长度多态性技术和 Southern 杂交方法对肝细胞癌 Rb 基因内含子1杂合缺失、Rb 基因结构异常和 Rb 基因5′端 CpG 岛的甲基化状态进行了分析。结果:在24例肝癌中,12例为杂合子,Rb 基因内含子1杂合缺失率为25%。在10例肝癌中未发现 Rb 基因重排现象,但2例分别在4.5kb 和9.8kb、7.5kb 处缺失。15例肝癌只有1例肝透明细胞癌出现 Rb 基因5′端高甲基化。结论:肝细胞癌Rb 基因的主要失活机制可能为缺失,除此之外,DNA 甲基化异常可能参与某些亚类肝癌 Rb 基因的失活。

Objectives:Deletion and abnormal DNA methylation are two important mechanisms for Rb gene inactivation.In this study,we analyzed the methylation state and alteration of Rb gene in structure. Methods:PCR-RFLP and Southern blot were used in analysis of deletion of Rb gene.Using methylation sensitive restriction endonuciease enzyme SacⅡ,we also detected the methylation of Rb gene at CpG island.Results:12 informative cases were found in 24 HCC and loss of heterozygosity(LOH) of Rb gene at intron 1 was 25%(3/12).No rearragement but deletion at 4.5kb band and 9.8kb,7.5kb band in 2 cases were found among 10 HCC cases.5 normal liver tissues and 14 HCC showed unmethylation in restriction enzyme SacⅡ recongnized CpG island at 5′ end of Rb gene except for one clear-cell hepatic carcinoma which revealed a hypermethylation.Conclusions:Mechanism of inactivation for Rb gene is multiple in HCC.The deletion may be a main reason for Rb gene inactivation in HCC,but DNA methylation may involve in some types of HCC.The alteration of Rb gene may be a late genetic event and useful in predicting prognosis of HCC.