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。     

中国人遗传性非息肉病性结直肠癌错配修复基因大片段缺失研究

目的了解中国人遗传性非息肉病性结直肠癌(hereditary nonpolyposis colorectal cancer．HNPCC)家系中MSH和MLH1基因大片段缺失情况及特点，以进一步完善中国人HNPCC家系遗传检测内容。方法取14个符合中国人HNPCC诊断标准的HNPCC家系肿瘤先证者外周血DNA，用荧光标记多重PCR技术结合GeneScan分析系统检测MSH2和MLH1基因大片段缺失。结果14例患者中有1例检测到MSH2基因第1～7外显子缺失，该家系另1例大肠癌患者和3个家系成员有同样的基因片段缺失。结论中国人HNPCC家系错配修复基因大片段缺失可能以MSH2比较常见。建议在中国人HNPCC家系遗传检测中常规包含错配修复基因大片段缺失检测。     

MLH1、MSH2基因 mRNA突变分析与遗传性非息肉性结直肠癌的基因诊断

目的检测胚系MLH1和MSH2基因mRNA突变，确立遗传性非息肉性结直肠癌（hereditary nonpolyposis colorectal cancer，HNPCC）家系。方法收集符合Amsterdam标准Ⅱ的12个家系14名家庭成员外周血，用特异引物和耐热性逆转录酶特异地逆转录MLH1和MSH2的RNA；利用长模板PCR扩增酶扩增逆转录产物（cDNA）；测序分析扩增产物。提取外周血的DNA，设计与利用上述方法检测出突变对应外显子的特异性引物，利用Taq DNA聚合酶扩增测序，以检测上述方法的有效性。结果利用基于外周血mRNA的方法，在6个家系中检出6个胚系突变，4个MLH1突变和2个MSH2突变，MLH1突变分别位于第8、12、16和第19外显子；MSH2突变分别位于第1和第2外显子。利用基于外周血DNA的方法，上述突变均在MLH1和MSH2相应的外显子中得到验证。突变类型为4个错义突变、1个同义突变和1个非编码区突变；其中5个突变国际上尚未报道；6个突变中有5个为病理性，分布于5个不同家系，该5个家系被确诊为HNPCC家系。结论基于外周血MLH1和MSH2 mRNA异常的检测能确诊HNPCC家系；该方法敏感、省时、节约成本。     

人错配修复基因hMLH1研究的新进展

人错配修复基因(mismatch repair,MMR)的主要功能是对DNA链中因某些原因造成的错误配对进行修复.目前已知MMR主要有hMLH1、hMSH2、hMSH6、hPMS2等.它们能够识别和修复在DNA复制过程中因插入、缺失或单核苷酸突变形成的错配,从而大大减低基因组微卫星不稳定性(MSI),维持基因组的稳定性.     

两个遗传性非患肉性结直肠癌家系中MLH1和MSH2基因的突变检测

目的 确定两个遗传性非息肉性结直肠癌(hereditary nonpolyposis colorectal cancer,HNPCC)家系的致病基因,选择MLH1基因和MSH2基因进行突变检测.方法 采用聚合酶链反应结合DNA直接测序法,对两个遗传性非息肉性结直肠癌家系的患者进行MLH1基因和MSH2基因的突变检测;发现变异后,采用PCR-限制性片段长度多态性或直接测序法鉴定此变异是否属于突变.结果 在家系A的患者中发现了位于MLH1基因第3外显子内的新突变c.243_244 insA;在家系B的患者中发现了MSH2基因第7外显子内的c.1215_1218dupCCGA突变,这两个突变都导致了编码蛋白的提前终止.结论 MLH1基因的c.243_244insA突变和MSH2基因的c.1215_1218dupCCGA突变分别是导致家系A和家系B发生遗传性非息肉性结直肠癌的致病突变.     

中国人遗传性非息肉病性结直肠癌MSH6基因胚系突变的测序研究

目的探讨中国人遗传性非息肉病性结直肠癌(hereditary nonpolyposis colorectal cancer,HNPCC)家系中MSH6基因胚系突变。方法采用PCR-直接测序的方法检测39个无胚系MSH2及MLH1基因突变、符合不同临床标准的中国人HNPCC家系先证者MSH6基因各外显子胚系突变;对137名正常人胚系基因组DNA进行错义突变相应外显子的测序分析。应用Envision二步法检测有突变的先证者肿瘤组织MSH6蛋白表达。结果在39个HNPCC先证者中共发现6个MSH6基因的胚系突变,分别位于第4、6、9和第10外显子;突变类型为4个错义突变、1个无义突变、1个剪接区的插入突变;对4个错义突变的相应外显子的测序分析显示:137名正常人胚系基因组DNA5例具有第6外显子1163密码子处的c.3488A>T的错义突变,约占3.65%(5/137),为单核苷酸多态性(single nucleotide polymorphism,SNP);其余错义突变在正常人群中均未发现。在6例有MSH6基因胚系突变家系的肿瘤组织中免疫组化染色除1例为SNP的肿瘤组织MSH6蛋白阳性表达外,其余均为阴性表达。经过查询国际HNPCC突变数据库及SNP数据库证实上述突变中5个为国际上尚未报道的病理性突变,1个为新发现的SNP。结论MSH6基因胚系突变在符合不同临床标准的中国人HNPCC中均起一定作用,对无MSH2及MLH1基因胚系突变的先证者行MSH6基因胚系突变的测序分析对确诊HNPCC家系是必要的。     

中国人消化道肿瘤发病的遗传背景因素——错配修复基因hMLH1错义突变Va1384Asp

目的 探讨中国人中存在的错配修复基因ｈＭＬＨ１ Ｖａ１３８４Ａｓｐ在大肠癌,胃癌,食道癌发病中的作用。方法 中国汉族人１０１例大肠癌患者,７９例胃癌患者,７６例食道癌患者,７９例和７６例胃癌和食道癌患者的亲属,１００名正常对照,各取正常体细胞,提取基因组ＤＮＡ。ＰＣＲ－ＳＳＣＰ和ＤＮＡ序列分析技术检测ｈＭＬＨ１基因的第１２外显子,比较分析Ｖａｌ３８４Ａｓｐ的检出率。     

658例结直肠癌错配修复蛋白的表达及其与临床病理特征的关系北大核心CSCD

目的探讨错配修复（mismatch repair,MMR）蛋白MLH1、MSH2、MSH6和PMS2在结直肠癌中的表达情况及其与患者临床病理特征之间的关系。方法收集中国医科大学附属盛京医院2016年1月至2017年1月间658例连续的结直肠癌病例,患者中男性409例,女性249例;年龄20-92岁,平均年龄（63±5）岁。采用免疫组织化学EnVision法检测结直肠癌组织中MLH1、MSH2、MSH6和PMS2蛋白表达缺失的情况,和MLH1蛋白表达缺失的结肠癌病例中的BRAF突变,分析MMR蛋白表达缺失与结直肠癌患者临床病理特征之间的关系。结果658例结直肠癌有44例（6．7％）发生MMR蛋白表达缺失,MLH1、MSH2、MSH6、PMS2蛋白表达缺失率分别为4．1％（27／658）、2．3％（15／658）、2．4％（16／658）、4．3％（28／658）。MMR蛋白表达缺失以MLH1与PMS2表达联合缺失（61．4％,27／44）、MSH2与MSH6表达联合缺失（34．1％,15／44）为主;PMS2和MSH6蛋白表达单独缺失的各有1例（2．3％,1／44）。进行BRAF V600E检测的27例MLH1蛋白缺失的病例中有7例（25．9％）为BRAF阳性,提示该7例患者可能存在因BRAF基因突变导致的MLH1蛋白表达缺失,属于散发型结直肠癌。结直肠癌组织中MMR蛋白表达缺失与肿瘤浸润深度、淋巴结转移、脉管癌栓、临床分期以及肿瘤血行转移无关（P〉0．05）,与更低程度的肿瘤组织分化、组织学类型和发病部位以及肿瘤浸润淋巴细胞数目增加显著相关（P〈0．01）：其中MLH1、PMS2蛋白表达缺失与组织学类型相关（P=0．049,P=0．013）,常伴黏液腺癌分化;MLH1、PMS2蛋白表达缺失多发生于右半结肠（P=0．006,P=0．002）;MSH2与MSH6蛋白表达缺失的患者发病年龄相对较小（P=0．014,P=0．023）;MSH2与PMS2蛋白表达缺失与性别相关,MSH2蛋白缺失多发生于女性（P=0．048）,PMS2蛋白表达缺失多发生于男性（P=0．031）。结论MMR蛋白缺失结直肠癌患者发病年龄低,组织分化程度低,发生部位多位于右半结肠,癌组织常伴有黏液腺癌分化。     

鸟氨酸氨甲酰基转移酶缺乏症OTC基因错义突变的分子鉴定

目的 对一个鸟氨酸氨甲酰基转移酶缺乏症(ornithine transcarbamylase deficiency,OTCD)家系进行分子遗传学检测,从基因水平确定其原因,为遗传咨询和产前诊断提供依据.方法 应用聚合酶链扩增技术和Sanger测序法对该家系成员的鸟氨酸氨甲酰转移酶基因(ornithine carbamoyltransferase,OTC)的10个外显子进行直接测序,检测潜在的致病突变,以100名健康人为正常对照.结果 先证者新生儿期发病,OTC基因测序发现其第9外显子发生错义突变c.917G＞C,第306位密码子由AGA突变为ACA,精氨酸替换为苏氨酸,即p.R306T.家系成员检测证实先证者母亲及家系中另外两名女性为表型正常的c.917G＞C杂合突变携带者,其他家系成员及100名对照者未发现上述突变.结论 结合生物信息学分析,错义突变c.917G＞C为该家系的致病原因.该突变尚未见报道,是一新发现的OTC基因突变位点.     

遗传性非息肉性结直肠癌的错配修复系统研究进展

遗传性非息肉性结直肠癌（ｈｅｒｅｄｉｔａｒｙｎｏｎ－ｐｏｌｙｐｏｓｉｓｃｏｌｏｒｅｃｔａｌｃａｎｃｅｒ，ＨＮＰＣＣ）是发病率最高的消化道肿瘤，受累个体在５０岁以前常发生结直肠癌、子宫内膜癌、卵巢癌、胃癌以及其它一些脏器的肿瘤〔１〕。从１９８９年起，由...     

Mismatch repair genes in renal cortical neoplasms

Mutation of human mutL homolog 1 (MLH-1) and human mutS homolog 2 (MSH-2) has been linked with the pathogenesis of colorectal carcinoma in hereditary nonpolyposis colorectal cancer syndrome and other carcinomas. Mutations of these genes in renal cell carcinomas were recently described. The aim of this study was to examine the expression of MLH-1 and MSH-2 in renal cortical neoplasms of various histological types by immunohistochemistry. Thirty-eight (n = 38) resected renal tumors were obtained from the surgical pathology files of the UMass Memorial Healthcare, including clear cell carcinomas (CLEARs, n = 20), papillary carcinomas (PAPs, n = 8), chromophobe carcinomas (CHRs, n = 4), and oncocytomas (ONCs, n = 6). Positive immunostaining for MLH-1 and MSH-2 was graded by the number of positive tumor cell nuclei, as follows: 0, negative; 1, up to one third of positive nuclei; 2, one to two thirds positive; and 3, greater than two thirds positive. Loss of MLH-1 or MSH-2 was defined as a tumor with grade 0 or 1, compared with the normal tubules. Normal tubules and intercalated ducts contained cells positive for MLH-1 and MSH-2 in all cases. For both antibodies, positive staining in tumors ranged from grade 1 to 3 in the CLEAR and PAP but was only grade 2 to 3 in the CHR and ONC. Loss of MLH-1 and/or MSH-2 occurred in malignant tumors but not in ONC. Loss of MLH-1 was present in 8 (40%) of 20 CLEARs and 4 (50%) of 8 PAPs, compared with loss of MSH-2 in 4 (20%) of 20 CLEARs and 1 (25%) of 4 CHRs. Our results suggest that loss of mismatch repair genes is involved in the malignant transformation in some renal carcinomas, particularly those derived from the proximal tubules.     

Novel germline mutations of hMSH2 in a patient with hereditary nonpolyposis colorectal cancer (HNPCC) and in a patient with six primary cancers

We screened for germline mutations of mismatch repair genes, hMLH1 and hMSH2, in five Japanese families carrying hereditary nonpolyposis colorectal cancer (HNPCC) and in a patient with multiple primary cancers. Screening the entire coding regions of both genes using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis, we found two novel germline mutations in hMSH2. One was a 1-bp insertion in exon 12, detected in a patient who had undergone surgery six times for independent tumors (four primary colorectal carcinomas, a small intestinal carcinoma, and an endometrial cancer). The other, in a second patient, was a missense mutation from CTT to TTT at codon 390 in exon 7 that resulted in substitution of phenylalanine for leucine. This conservative alteration was not found in any of 50 normal controls, but we cannot exclude the possibility that it may represent a rare polymorphism rather than a factor in the disease. Received: November 13, 1997 / Accepted: January 14, 1998     

Molecular basis of HNPCC: Mutations of MMR genes

Hereditary nonpolyposis colorectal cancer (HNPCC) is inherited as a dominant disorder caused by germline defects in one of at least four mismatch repair (MMR) genes. Two of these genes, hMSH2 and hMLH1, account for the vast majority of the germline mutations in HNPCC kindreds, whereas hPMS1 and hPMS2 are mutated in only few families. MMR genes also are susceptible to somatic mutations in sporadic tumors. The mutational spectrum of the MMR genes shows no predominant type of mutation. Furthermore, the mutations are spread throughout the length of the genes, with no significant hot spots. Identification of MMR genes as the cause of HNPCC made presymptomatic diagnosis a reality. However, the presence of multiple genes and the heterogeneity of mutations present challenges to the development of diagnostic tests for this disease. Hum Mutat 10:89–99, 1997. © 1997 Wiley-Liss, Inc.     

Unusual DNA mismatch repair-deficient tumors in Lynch syndrome: a report of new cases and review of the literature

Immunohistochemical detection of DNA mismatch repair proteins and polymerase chain reaction detection of microsatellite instability have enhanced the recognition of mismatch repair-deficient neoplasms in patients with Lynch syndrome and, consequently, led to the identification of tumors that have not been included in the currently known Lynch syndrome tumor spectrum. Here, we report 4 such unusual tumors. Three of the 4, a peritoneal mesothelioma, a pancreatic acinar cell carcinoma, and a pancreatic well-differentiated neuroendocrine tumor, represented tumor types that, to the best of our knowledge, have not been previously reported in Lynch syndrome. The fourth tumor was an adrenocortical carcinoma, which has rarely been reported previously in Lynch syndrome. Three of our 4 patients carried a pathogenic germ-line mutation in a mismatch repair gene. The unusual tumor in each of the 3 patients showed loss of the mismatch repair protein corresponding to the mutation. The fourth patient did not have mutation information but had a history of colonic and endometrial carcinomas; both lacked MSH2 and MSH6 proteins. Interestingly, none of the 4 unusual tumors revealed microsatellite instability on polymerase chain reaction testing, whereas an appendiceal carcinoma from 1 of the study patients who was tested simultaneously did. The recognition of such tumors expands the repertoire of usable test samples for the workup of high-risk families. As yet, however, there are no data to support the inclusion of these tumors into general screening guidelines for detecting Lynch syndrome, nor are there data to warrant surveillance for these tumors in patients with Lynch syndrome.     

Medullary carcinoma of the pancreas in a man with hereditary nonpolyposis colorectal cancer due to a mutation of the MSH2 mismatch repair gene

Pancreatic adenocarcinoma has been reported in kindreds with hereditary nonpolyposis colorectal cancer (HNPCC). Medullary carcinoma of the pancreas is a recently described rare variant of pancreatic adenocarcinoma. We describe a man with colorectal carcinoma who subsequently developed pancreatic medullary carcinoma. The tumor displayed microsatellite instability and loss of expression of the mismatch repair proteins MSH2 and MSH6. Mutational analysis of the mismatch repair genes MLH1 and MSH2 demonstrated a pathogenic nonsense mutation within the MSH2 gene, which is consistent with a diagnosis of HNPCC. This report adds support to an association between HNPCC and pancreatic adenocarcinoma displaying the medullary phenotype, suggesting that medullary features in a pancreatic carcinoma may point toward a genetic cancer predisposition. To our knowledge, this is the first reported case of medullary carcinoma of the pancreas in a patient with HNPCC due to a mutation of the MSH2 gene.     

Functional Analysis of BARD1 Missense Variants in Homology‐Directed Repair of DNA Double Strand Breaks

Genes associated with hereditary breast and ovarian cancer (HBOC) are often sequenced in search of mutations that are predictive of susceptibility to these cancer types, but the sequence results are frequently ambiguous because of the detection of missense substitutions for which the clinical impact is unknown. The BARD1 protein is the heterodimeric partner of BRCA1 and is included on clinical gene panels for testing for susceptibility to HBOC. Like BRCA1, it is required for homology‐directed DNA repair (HDR). We measured the HDR function of 29 BARD1 missense variants, 27 culled from clinical test results and two synthetic variants. Twenty‐three of the assayed variants were functional for HDR; of these, four are known neutral variants. Three variants showed intermediate function, and three others were defective in HDR. When mapped to BARD1 domains, residues crucial for HDR were located in the N‐ and C‐ termini of BARD1. In the BARD1 RING domain, critical residues mapped to the zinc‐coordinating amino acids and to the BRCA1‐BARD1 binding interface, highlighting the importance of interaction between BRCA1 and BARD1 for HDR activity. Based on these results, we propose that the HDR assay is a useful complement to genetic analyses to classify BARD1 variants of unknown clinical significance.     

Detection of Tn, sialosyl-Tn and T antigens in hereditary nonpolyposis colorectal cancer

The simple mucin-type carbohydrate antigens Tn, sialosyl-Tn, T and the cryptic sialylated variant of the last represent the mucin core oligosaccharide structures that are produced in the initial steps of the mucin biosynthetic pathway. Utilizing monoclonal antibodies anti-Tn antigen (HB-Tn1), anti-sialosyl-Tn antigen (HB-STn1), anti-T antigen (HB-T1) and the biotinylated Amaranthus caudatus agglutinin (ACA), we have investigated the expression of the simple mucin-type carbohydrate antigens in hereditary nonpolyposis colorectal cancer (HNPCC; 15 cases) compared with sporadic colorectal cancer (CRC; 60 cases) and normal colonic mucosa (30 cases). A variable positivity of Tn, sialosyl-Tn, T and the cryptic sialylated form of this latter antigen was encountered in both HNPCC and sporadic CRC cases; in addition, in normal colonic mucosa a constant reactivity was encountered only for Tn and the cryptic sialylated form of T, while negative results were always obtained for sialosyl-Tn and T antigens. Statistical analysis, performed using a Chi-square test, showed significantly lower (P=0.037) expression of sialosyl-Tn and higher (P=0.022) expression of T in HNPCC than in sporadic CRC, suggesting a greater presence of 1,3 galactosyl-transferase activity in HNPCC than in sporadic CRC. We were unable to identify a peculiar phenotype for HNPCC with simultaneous evaluation of reactivity for HB-Tn1, HB-STn1, HB-T1 and ACA; the biological significance of the preferential expression of T antigen in HNPCC remains to be investigated.     

遗传性非息肉病性结直肠癌的家系和染色体脆性部位研究

目的：报道一个遗传性非息肉病性结直肠癌的家系和细胞遗传学特征。方法：家系调查通过查阅患者病历,走访经治医生和知情成员所获得。细胞遗传学研究采用了外周血淋巴细胞脆性部位培养技术和G显带分析方法。结果：该家族患者符合阿姆斯特丹诊断标准,先证者祖父母后代发病呈常染色体显性遗传,致病基因来源于先证者祖母。细胞遗传学研究显示9例成员染色体异常率高达55．6％,其中1例正常成员亦检到脆性部位,是重点监测和随访的末病对象;表现为显性遗传的先证者祖父母后代5例成员与5例患者染色体异常率均达80％（4／5）。结论：根据系谱中发病规律和患者很高的染色体脆性部位检出率为该家族成员的发病预测、筛查、早诊断、早治疗具有简便、实用、经济的特点和应用价值,可让部分家族成员避免反复检查的痛苦。