家族性腺瘤性息肉病患者APC基因启动子区异常甲基化及大片段结构异常

目的 研究3个家族性腺瘤性息肉病(familial adenomatous polyposis,FAP)家系的腺瘤样息肉病(adenomatus polyposis coli)基因(APC)启动子1A区异常甲基化及DNA大片段结构异常.方法 对3个FAP家系成员的肿瘤组织标本和正常组织标本DNA进行化学修饰,应用甲基化特异PCR(methylation-speeif-ic PCR,MsP)和DNA序列分析方法筛查APC基因启动子1A区甲基化情况.采用多重连接依赖性探针扩增(multiplex ligation-dependent probe amplification,MIPA)分析系统检测5例FAP患者肿瘤组织标本和正常标本的APC基因的15个外显子及启动子区DNA大片段结构异常.结果 在1个家系中发现2例患者存在APC基因启动子1A区异常甲基化.同一个家系中另1例患者存在APC基因全基因杂合性缺失.结论 APC基因启动子1A区异常甲基化可影响APC功能,可能是结直肠癌进展过程中的早期事件;大片段缺失可能是导致典型FAP的一个因素.

Promoter hypermethylation and loss of heterozygosity of the APC gene in patients with familial adenomatous polyposts

Objective To investigate the status of hypermethylation in the promoter 1A region of the adenomatus polyposm coli(APC)gene in 3 familial adenomatous polyposis(FAP)pedigrees and to screen large fragment deletiom in the APC gene.Methods DNA from tumor tissues and corresponding normal tissues of 5 FAP patients was modified by sodium bisulfite.Then the methylation status of the APC gene was analvzed by methylation specific-PCR (MSP)and DNA sequencing.Multiplex ligation-dependent probe amplification(MLPA)waft used to screen aberrations involving large fragments from all teh 15 exons and pttmaoter region of APC gene.Results No methylation Wills present in normal tissues.Hypennethylation was found in tumor tissues of one proband and her son.Loss of heterozygosity was observed in another patient from the same FAP family.Conclusion Aberrant methylation ofthe APC promoter region proddes an important mechanism for impairing APC function and may occur early during colon neopLasia progression. Loss ofheterozygosity may play a role in patients with classical polyposis.