中国人家族性结直肠癌错配修复基因大片段变异分析

目的分析中国人家庭性结直肠癌错配修复基因大片段变异的特点。方法 采用多重连接探针扩增技术，分析32例具有家庭史结直肠癌、20例散发性结直肠癌患者错配修复基因MSH2的16个外显子、MLH1的19个外显子及7个其它基因外显子的拷贝数。研究工作包括：（1）双盲法分析阴性和阳性对照样本，完成方法学可靠性检验；（2）分析结直肠癌患者外周血细胞DNA，筛查MSH2和MLH1基因大片段变异。结果 多重连接探针扩增技术分析系统稳定检出阳性对照样本的DNA大片段缺失；在3/32（9.4%）具有家庭聚集性结直肠癌患者中检出遗传性MSH2基因DNA大片段缺失。而在20例散发性结直肠癌患者未检出这类突变。结论 中国人家族性结直肠癌患者中错配修复基因的大片段变异是频发事件，对此类患者的遗传检测应包含错配修复基因大片段变异的筛查。

The analysis for identifying large DNA fragment aberrations of MSH2 and MLH1 genes from familial colorectal cancer in China

Objective To investigate the frequency of large fragment aberrations of MSH2 and MLH1 genes from Chinese colorectal cancer (CRC) patients with family history. Methods Sixteen exons of MSH2, nineteen exons of MLH1 and seven DNA sequences from the other genes of the samples were screened and checked by multiplex ligation-dependent probe amplification (MLPA). First, the methodology was confirmed by testing the positive and negative control samples. Then, 32 CRC or hereditary nonpolyposis colorectal cancer (HNPCC) patients with family history and 20 cases of sporadic CRC were applied to investigate for the large fragment aberrations of MSH2 and MLH1 genes. Results The genomic DNA fragment deletions of all positive controls were identified and verified by MLPA. Three cases of 32 familial (hereditary) CRC/HNPCC were detected and identified to be the germline heterozygous deletions of MSH2 gene, of which exons 1-7 were deleted from patient No.3, exon 11 from No.25 and exons 2-6 from No.11. However, no genomic DNA fragment aberration of either MSH2 or MLH1 gene was uncovered from 20 sporadic CRC. Conclusion Large DNA fragment aberrations of MSH2 gene was a frequent cause of Chinese HNPCC and CRC patients with family history, and the identification of those aberrations should be included in the regular genetic analysis for CRC/HNPCC patients.