Farrington S M, Lin-Goerke J, Ling J, Wang Y, Burczak J D, Robbins D J, Dunlop M G
Department of Surgery, University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom.
Am J Hum Genet. 1998 Sep;63(3):749-59. doi: 10.1086/301996.
Germ-line mutations in DNA mismatch-repair genes impart a markedly elevated cancer risk, often presenting as autosomal dominant hereditary nonpolyposis colorectal cancer (HNPCC). However, there are no pathognomonic features of HNPCC, not all gene carriers have a family history of the disease, and families fulfilling the Amsterdam criteria are relatively uncommon. Genetic testing of probands with early-onset colorectal cancer, irrespective of family history, is one approach that would allow predictive genetic testing of at-risk relatives. We cloned and sequenced hMSH2 and hMLH1 introns, to optimize genomic sequencing. We then systematically analyzed the entire hMSH2 and hMLH1 genes, by genomic sequencing and in vitro synthesized-protein-truncation assay (IVSP), in 50 colorectal cancer patients <30 years of age at diagnosis. To determine polymorphic variants, 26 anonymous donors also were sequenced. All subjects analyzed had at least 1 of 37 different polymorphic or pathogenic variants. IVSP complemented genomic sequencing, by detection of mutations not identified by genomic analysis. Fourteen cancer patients (28%) had pathogenic mutations, and a number of other variants also may have had a pathogenic significance that remains to be elucidated. Tumor replication-error status was useful in targeting sequencing efforts for this cohort of young patients: sensitivity was 86%, specificity 73%, and positive and negative predictive values 63% and 90%, respectively. These data indicate that an appreciable proportion of young colon cancer probands carry a germ-line mutation in a DNA mismatch-repair gene.
DNA错配修复基因中的种系突变会显著增加患癌风险，常表现为常染色体显性遗传性非息肉病性结直肠癌（HNPCC）。然而，HNPCC并无特征性表现，并非所有基因携带者都有该病家族史，且符合阿姆斯特丹标准的家族相对少见。对早发性结直肠癌先证者进行基因检测，无论其家族史如何，是一种可对高危亲属进行预测性基因检测的方法。我们克隆并测序了hMSH2和hMLH1内含子，以优化基因组测序。然后，我们通过基因组测序和体外合成蛋白截短试验（IVSP），对50例诊断时年龄小于30岁的结直肠癌患者的整个hMSH2和hMLH1基因进行了系统分析。为确定多态性变异，还对26名匿名供者进行了测序。所有分析对象至少有37种不同的多态性或致病性变异中的1种。IVSP通过检测基因组分析未发现的突变，补充了基因组测序。14名癌症患者（28%）有致病性突变，其他一些变异可能也具有致病性，有待进一步阐明。肿瘤复制错误状态有助于针对该年轻患者群体进行测序：敏感性为86%，特异性为73%，阳性和阴性预测值分别为63%和90%。这些数据表明，相当一部分年轻结肠癌先证者携带DNA错配修复基因的种系突变。
