利用二代测序技术对45例疑似Lynch综合征肿瘤的基因变异分析

Genetic analysis of 45 patients with suspected Lynch syndrome using next-generation sequencing

目的探讨二代测序(NGS)技术在Lynch综合征相关基因胚系突变检测中的价值。方法采用免疫组化方法检测2016—2018年在山东省立医院手术切除的肿瘤组织中MutL homolog 1(MLH1)、PMS1 homolog 2(PMS2)、MutS homolog 2(MSH2)和MutS homolog 6(MSH6)4种DNA错配修复(MMR)蛋白的表达情况。根据MMR的表达情况和临床资料,选取45例疑似Lynch综合征患者,提取其经显微镜证实无癌累及正常组织的DNA,对MLH1和MSH2等12个基因进行NGS测序分析,应用生物信息学技术分析基因胚系突变位点和意义。采用Sanger测序对10例患者的可疑致病位点进行验证。结果免疫组化检测显示,45例肿瘤组织标本中,MLH1和PMS2表达缺失22例,MSH2和MSH6表达缺失16例,MMR蛋白表达正常7例。NGS显示,28例结肠癌患者的正常组织样本中,4例有MLH1致病性突变,1例有MLH1疑似致病性突变,2例有MSH2致病性突变,2例有MSH2疑似致病性突变。6例直肠癌、6例胃癌和7例免疫组化检测MMR表达正常结直肠癌患者的正常组织样本中均未见明显MMR基因突变。5例子宫内膜癌患者的的正常组织样本中,MLH1和MSH2致病性突变各1例,MLH1疑似致病性突变1例。此外,NGS还检测到许多其他基因异常和未见报道的基因突变。Sanger测序均检测到与NGS检测结果相同的MLH1和MSH2基因突变位点。结论高通量NGS技术可以快速、准确、可靠地检测到疑似Lynch综合征患者的异常基因,对消化道等遗传性肿瘤的相关基因检测具有广阔的应用前景。

Objective To evaluate the value of next generation sequencing(NGS)in the genetic testing of Lynch syndrome.Methods Immunohistochemical method was used to detect the expressions of DNA mismatch repair(MMR)proteins,including MutL homolog 1(MLH1),PMS1 homolog 2(PMS2),MutS homolog 2(MSH2)and MutS homolog 6(MSH6)in colorectal cancer,gastric cancer and endometrial cancer tissues collected from Shandong Provincial Hospital between 2016 and 2018.The genomic DNA of 45 patients who were suspected with Lynch syndrome was extracted from non-cancerous tissue paraffin samples,which were postoperatively confirmed by microscope.The mutations of 12 genes including MLH1 and MSH2 were detected using NGS.The germline mutant sites and significance were analyzed by bioinformatics technology and further confirmed by using Sanger sequencing.Results The immunohistochemical results showed that the 45 cases of suspected Lynch syndrome included 22 cases of MLH1 and PMS2 deficient expression,16 cases of MLH2 and MSH6 deficient expression,and 7 cases of MMR proteins normal expression.The NGS result showed that 28 cases of adjacent sample from colon cancer patients included 4 cases of MLH1 pathogenic mutation,1 case of suspected MLH1 mutation,2 cases of MLH2 pathogenic mutation,2 cases of suspected MLH2 mutation.No MMR gene mutation was found in adjacent samples of 6 cases of rectal cancer,6 cases of gastric cancer and 7 cases of colorectal cancer with MMR normal expression.One case of MLH1 or MHL2 pathogenic mutation and one case of MLH1 suspected mutation was detected in adjacent samples of 5 cases of endometrial cancer.Moreover,NGS also detected many other genes mutations and unreported gene mutation sites.Pathogenic and suspected MLH1 and MSH2 mutations were verified by Sanger sequencing.Conclusions High-throughput NGS is a quick,accurate and reliable technique to identify gene variants in suspected Lynch syndrome patients.It has a wide application prospect for gene testing of tumors associated with Lynch syndrome.