遗传性非息肉性大肠癌患者中hMLH1和hMSH2基因遗传性突变的分析

目的通过分析遗传性非息肉性大肠癌（ＨＮＰＣＣ）患者错配修复基因的遗传性突变，对患者的家族成员进行遗传咨询和症状前的基因诊断。方法用ＰＣＲ－异源双链体形成、ＰＣＲ－ＳＳＣＰ和ＤＮＡ序列分析技术，检测１４例ＨＮＰＣＣ、１０例有家族史大肠癌患者的外周血细胞ＤＮＡ，分析其错配修复基因ｈＭＬＨ１、ｈＭＳＨ２的所有３５个外显子。结果确认４／１４的ＨＮＰＣＣ、１／１０有家族史的大肠癌患者携带遗传性错配修复基因的突变，其中２例见于ｈＭＬＨ１基因，３例ｈＭＳＨ２基因。突变类型：３例由碱基缺失导致的移码突变，１例无义突变，１例错义突变。结论ＨＮＰＣＣ的发生与错配修复基因的突变密切相关；在大肠癌患者中检测遗传性错配修复基因的突变不宜仅限于严格符合临床诊断标准的ＨＮＰＣＣ患者。

GERMLINE MUTATION ANALYSIS IN hMLH1 AND hMSH2 GENES IN HEREDITARY NONPOLYPOSIS COLORECTAL CANCER AND COLORECTAL CANCER PATIENTS WITH FAMILIAL HISTORY

Objective Analysis for germline mutation in mismatch repair genes, hMLH1 and hMSH2, in hereditary nonpolyposis colorectal cancer(HNPCC) patients and presymptomatic diagnosis in HNPCC families.Methods Genomic DNA extracted from peripheral blood were subjected to mutation analysis in 35 exons of the hMLH1 and hMSH2 genes by heteroduplex and single strand conformation polymorphism(SSCP) followed by DNA sequencing of aberrant bands in 14 HNPCC and 10 colorectal cancer patients with familial history.Results Germline mutations were identified in 4/14 HNPCC patients and in 1/10 colorectal cancer patients with familial history, 2 of them in the hMLH1 and 3 in hMSH2 genes. The five mutations are all unique and are predicted to result in nonfunctional proteins by either frameshift (three), nonsense(one) or missense mutation (one) in evolutionarily conserved region.Conclusion HNPPC is closely related to the mutations of mismatch repair genes. Germline mutation analysis for presymptomatic diagnosis in HNPCC could not be limited in the patients meeting clinical diagnosis criteria (Amsterdam 1991).