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目的 探讨错配修复基因MSH2、MLH1功能和结构改变在低龄大肠癌患者发病中的作用。方法 配对提取 4 2例低龄 (<5 0岁 )大肠癌患者的正常细胞和肿瘤细胞DNA ,在错配修复基因功能状态分析的基础上 ,对伴有微卫星DNA不稳定 (MSI+ )患者 ,应用变性高效液相色谱技术(DHPLC)、DNA序列分析技术及定量多重PCR技术系统分析MSH2、MLH1基因的微小突变和大片段DNA缺失。结果 2 2 / 4 2 (5 2 .4 % )的患者肿瘤细胞检出MSI+ ,其中 10 / 4 2为高度不稳定 (MSI+ H) ,12 / 4 2低度不稳定 (MSI+ L)。对MSI+ 患者的进一步突变分析揭示 ,在 9例患者存在MSH2、MLH1基因的 8个位点遗传性单个碱基的改变 ,其中 3/ 8为新发现的点突变 ,5 / 8为基因的多态位点 ;在 2例存在MSI+ H的肿瘤组织检出MSH2基因大片段DNA(exon 1 6 )缺失或MLH1基因的错义突变Met2 4 2Ile。结论 中国人低龄大肠癌患者中MSH2、MLH1基因的遗传性和体细胞性突变为频发事件。
Objective To investigate the roles of mismatch repair genes (MSH2) and MLH1 in the pathogenesis of younger colorectal cancer. Methods The DNA of normal and tumor cells from 42 cases of colorectal cancer patients younger than age (<50 years old) was extracted by pairing. Based on the analysis of functional status of mismatch repair gene, the patients with microsatellite DNA instability (MSI +) Denaturing high performance liquid chromatography (DHPLC), DNA sequence analysis and quantitative PCR were used to systematically analyze the small mutations and large DNA deletions of MSH2 and MLH1 genes. RESULTS: MSI + was detected in 2 of 42 (52.4%) patients, with 10/42 being highly unstable (MSI + H) and 12/42 mildly unstable (MSI + L). Further mutation analysis of MSI + patients revealed that there were 9 single gene mutations in 8 sites of MSH2 and MLH1 genes, of which 3/8 were newly discovered point mutations and 5/8 were polymorphisms Locus. The deletion of MSH2 large fragment DNA (exon 16) or the missense mutation of MLH1 gene was detected in two tumor tissues with MSI + H. Met2 4 2Ile. Conclusion The hereditary and somatic mutations of MSH2 and MLH1 genes in Chinese patients with younger colorectal cancer are frequent.