错配修复基因变异与中国人散发性大肠癌发病年龄之间的关系

目的 :探讨错配修复基因变异与中国人散发性大肠癌发病年龄之间的关系。方法 :随机选取 1 0 0例临床初诊的散发性大肠癌患者 ,配对提取手术切除的癌组织和同源正常组织的基因组DNA ,检测并分析癌细胞微卫星DNA不稳定性 (MSI)。结果 :46/1 0 0 (46 % )的癌组织MSI阳性 (MSI+ ) ,其中 1 8%为MSI+ H ,2 8%MSI+ L。按年龄分组分析表明 ,发病年龄 <45岁的大肠癌患者中MSI+ 检出率明显高于≥ 65岁的大肠癌患者 (P <0 .0 5) ,且MSI+ 的检出率与患者的发病年龄呈负相关 (r =- 0 .95 ,P <0 .0 5) ,但与癌细胞的分化及患者的临床分期无关。结论 :中国人散发性大肠癌中错配修复基因功能的丧失可能出现在癌症发生的早期 ,可能参与构成部分散发性大肠癌发病的遗传背景因素     

错配修复基因与大肠癌相关性研究进展

目的 MMR系统是一组高度保守基因及其产物蛋白构成,其主要功能是纠正DNA复制、重组及基因损伤时出现的碱基配对错误.本研究总结国内外错配修复基因与大肠癌相关性的研究进展.方法 检索Pubmed和万方数据库,以“错配修复基因、微卫星不稳定、大肠癌”等为关键词,检索1997-01-2016-06的相关文献共102篇.纳入标准:(1)错配修复基因与微卫星不稳定的关系.(2)错配修复基因大肠癌的发生及预后的关系.根据纳入标准,最终选取49篇文献纳入分析.结果 错配修复系统是一种广泛存在于机体细胞内的自我修复机制,对防止基因突变和维持基因组稳定性方面起着重要作用.错配修复基因突变与微卫星不稳定关系密切,错配修复基因发生突变时,使机体肿瘤易感性明显增加.结论 错配修复系统是大肠癌的发生、发展的重要预后指标.     

错配修复基因与散发性肿瘤

错配修复基因（Mismatch Repair Genes，MMR genes）是细胞内负责对碱基错配进行修复的基因，它们的缺陷导致癌相关基因突变不能及时有效纠正，从而肿瘤易感。近年业发现MMR基因不仅与遗传性肿瘤有关，还与其它许多散发性肿瘤有关，现就其与散发性肿瘤的关系作一综述。     

微卫星不稳定散发性大肠癌的临床病理特征和DNA倍体研究

目的:探讨微卫星不稳定的散发性大肠癌的临床病理特征及微卫星不稳定表型和DNA倍体类型的关系。方法:对71例散发性大肠癌行BAT25和BAT26两个位点的微卫星不稳定检测和流式细胞术倍体分析,探讨微卫星不稳定状态和临床病理特征及DNA倍体类型的关系。结果:微卫星不稳定的阳性率为9.86%(7/71),微卫星不稳定表型和发病部位、组织学类型及分化程度相关(P<0.05),而与性别、年龄、淋巴结转移和分期无关。微卫星不稳定的散发性大肠癌中右半结肠癌和低分化腺癌的比例高于微卫星稳定者。68例患者检出二倍体和异倍体分别为18和50例,微卫星不稳定表型者5例为二倍体,因此和DNA倍体类型显著相关(P=0.012)。结论:微卫星不稳定的散发性大肠癌好发于右半结肠,具有低分化腺癌的倾向,多为二倍体。     

错配修复基因异常改变与大肠癌的关系

研究表明，大肠癌(colorectal cancer，CRC)的发生是1个多因素多步骤的过程，是机体的内因与环境的外因相互作用的结果。其中错配修复基因的改变与遗传性和散发性结直肠癌的基因不稳定性有关。本文就错配修复基因异常导致大肠癌的机制及其诊断与治疗的最新研究进展做一综述。     

DNA错配修复系统缺陷在结肠癌中的研究进展

结肠癌在其多阶段演变过程中涉及多种基因。约85％的结肠癌由染色体不稳定（chromosomalinsta-bility,CIN）引起,另有约15％的结肠癌则由DNA错配修复（mismatchrepair,MMR）基因缺陷所致,其中遗传性非息肉性结直肠癌（hereditarynonpolypo—siscolorectalcancer,HNPCC）占3％～5％,而散发性结肠癌占10％～15％。     

错配修复缺陷大肠癌

错配修复缺陷大肠癌熊斌郑树作者单位：浙江医科大学肿瘤研究所（杭州３１０００９）大肠癌是包括内外因的多因素病因和多步骤的癌变过程；最近发现错配修复功能缺陷（表现为微卫星不稳定性或称复制错误阳性）在某些大肠癌的发生发展中起重要作用，并被认为是大肠癌的一种...     

散发性结直肠癌微卫星不稳定状态与错配修复蛋白表达缺失及临床病理特征的相关性

目的： 探讨散发性结直肠癌微卫星不稳定(microsatellite instability,MSI)情况及其与错配修复 (mismatch repair,MMR) 蛋白MLH1、MSH2、MSH6、PMS2表达缺失的相关性,并总结MSI散发性结直肠癌的临床病理学特征。方法：多重荧光PCR法检测散发性结直肠癌肿瘤组织DNA的微卫星不稳定性,免疫组化(Immunohistochemistry,IHC)S-P法检测散发性结直肠癌肿瘤组织MLH1、MSH2、MSH6、PMS2蛋白的表达缺失,分析MSI发生与MMR蛋白表达缺失及临床病理特征的相关性。结果：75 例散发性结直肠癌检出MSI 21例(28%),包括 MSI-H 19例、MSI-L 2例,其他54例(72%)为MSS。检出MMR蛋白表达缺失16例(21.33%),其中15例(93.75%)为MSI-H、1例(6.25%)为MSS;MMR蛋白表达59例(78.67%),其中4例(6.78%)为MSI-H、2例(3.39%)MSI-L,其他53例为MSS。MSI组MMR蛋白缺失率(15/21,71.43%)显著高于MSS组(1/54,1.9%)（P<0.01）。MSI与患者年龄,是否黏液腺癌,肿瘤有无远处转移有关（P<0.01）,其中MSI-H好发于年龄>50岁、肿瘤无远处转移、MMR蛋白缺失人群,且类型以黏液腺癌为主。结论： 散发性结直肠癌肿瘤组织中MSI发生率高于MMR蛋白缺失率,并且MSI-H的散发性结直肠癌转移风险较低、预后较好。检测MSI 状态对提高结直肠癌的预防、诊断和治疗水平,降低结直肠癌的发病率和病死率有着重要意义。     

错配修复基因与大肠癌相关性的研究进展

ＤＮＡ错配修复（ｍｉｓｍａｔｃｈｒｅｐａｉｒ,ＭＭＲ）是机体内ＤＮＡ修复机制的一种重要形式,广泛存在于生物体中,在防止基因突变和维持基因组稳定性的过程中起关键作用。最早研究发现错配修复基因突变与遗传性非息肉性大肠癌的发生有密切关联。越来越多的研究发现,错配修复基因功能缺失在一部分散发性大肠癌的发生过程中也起到一定的作用。本文就错配修复基因与大肠癌相关性的研究进展作一综述。     

Clinical and molecular characterisation of hereditary and sporadic metastatic colorectal cancers harbouring microsatellite instability/DNA mismatch repair deficiency

BackgroundPatients treated with chemotherapy for microsatellite unstable (MSI) and/or mismatch repair deficient (dMMR) cancer metastatic colorectal cancer (mCRC) exhibit poor prognosis. We aimed to evaluate the relevance of distinguishing sporadic from Lynch syndrome (LS)-like mCRCs.Patients and methodsMSI/dMMR mCRC patients were retrospectively identified in six French hospitals. Tumour samples were screened for MSI, dMMR, RAS/RAF mutations and MLH1 methylation. Sporadic cases were molecularly defined as those displaying MLH1/PMS2 loss of expression with BRAFV600E and/or MLH1 hypermethylation and no MMR germline mutation.ResultsAmong 129 MSI/dMMR mCRC patients, 81 (63%) were LS-like and 48 (37%) had sporadic tumours; 22% of MLH1/PMS2-negative mCRCs would have been misclassified using an algorithm based on local medical records (age, Amsterdam II criteria, BRAF and MMR statuses when locally tested), compared to a systematical assessment of MMR, BRAF and MLH1 methylation statuses. In univariate analysis, parameters associated with better overall survival were age (P < 0.0001), metastatic resection (P = 0.001) and LS-like mCRC (P = 0.01), but not BRAFV600E. In multivariate analysis, age (hazard ratio (HR) = 3.19, P = 0.01) and metastatic resection (HR = 4.2, P = 0.001) were associated with overall survival, but not LS. LS-like patients were associated with more frequent liver involvement, metastatic resection and better disease-free survival after metastasectomy (HR = 0.28, P = 0.01). Median progression-free survival of first-line chemotherapy was similar between the two groups (4.2 and 4.2 months; P = 0.44).ConclusionsLS-like and sporadic MSI/dMMR mCRCs display distinct natural histories. MMR, BRAF mutation and MLH1 methylation testing should be mandatory to differentiate LS-like and sporadic MSI/dMMR mCRC, to determine in particular whether immune checkpoint inhibitors efficacy differs in these two populations.     

中国人遗传性非息肉病性结直肠癌错配修复缺陷表型分析

目的：对中国人遗传性非息肉病性结直肠癌的肿瘤组织进行hMSH2和hMLH1,蛋白表达监测及微卫星不稳定性检测。方法：共收集58个符合不同临床诊断标准的家系,对符合Amsterdam标准24个家系(AC组)的38个肿瘤(来自22个家系)、符合日本标准15个家系(JC组)的16个肿瘤(来自12个家系)、符合Bethesda指导纲要的19例患者(BG组)中12例的13个肿瘤组织进行研究。选取5个微卫星位点BAT26、BAT25、D2S123、D5S346和D17S250及单克隆抗体hMSH2和hMLH1用于分析。结果：AC组家系100％表现为高度微卫星不稳定性(MSI-H),其中81．8％(18／22)表现为hMSH2和hMLH1表达异常;JC组家系中,93．3％(14／15)和1／1个腺瘤表现为MSI-H,45．5％(5／11)表现为hMSH2或hMLH1表达异常;BG组家系中,53．8％(7／13)患者肿瘤表现为MSI-H,其中4／7表现hMSH1表达异常。结论：不同临床诊断标准的家系,其肿瘤组织MSI-H阳性和错配修复蛋白表达异常的频率不同,Amsterdam标准和日本标准可较准确地反映肿瘤组织中错配修复缺陷情况,但Bethesda指导纲要也不可或缺。在临床诊断的基础上,合用免疫组化和微卫星不稳定性检测,可以较全面地检测到错配修复缺陷肿瘤。错配修复蛋白表达异常和微卫星不稳定性密切相关。     

Genetic and clinical determinants of constitutional mismatch repair deficiency syndrome: Report from the constitutional mismatch repair deficiency consortium

BackgroundConstitutional mismatch repair deficiency (CMMRD) is a devastating cancer predisposition syndrome for which data regarding clinical manifestations, molecular screening tools and management are limited.MethodsWe established an international CMMRD consortium and collected comprehensive clinical and genetic data. Molecular diagnosis of tumour and germline biospecimens was performed. A surveillance protocol was developed and implemented.ResultsOverall, 22/23 (96%) of children with CMMRD developed 40 different tumours. While childhood CMMRD related tumours were observed in all families, Lynch related tumours in adults were observed in only 2/14 families (p = 0.0007). All children with CMMRD had café-au-lait spots and 11/14 came from consanguineous families. Brain tumours were the most common cancers reported (48%) followed by gastrointestinal (32%) and haematological malignancies (15%). Importantly, 12 (30%) of these were low grade and resectable cancers. Tumour immunohistochemistry was 100% sensitive and specific in diagnosing mismatch repair (MMR) deficiency of the corresponding gene while microsatellite instability was neither sensitive nor specific as a diagnostic tool (p < 0.0001). Furthermore, screening of normal tissue by immunohistochemistry correlated with genetic confirmation of CMMRD. The surveillance protocol detected 39 lesions which included asymptomatic malignant gliomas and gastrointestinal carcinomas. All tumours were amenable to complete resection and all patients undergoing surveillance are alive.DiscussionCMMRD is a highly penetrant syndrome where family history of cancer may not be contributory. Screening tumours and normal tissues using immunohistochemistry for abnormal expression of MMR gene products may help in diagnosis and early implementation of surveillance for these children.     

MutL homolog 1 methylation and microsatellite instability in sporadic colorectal tumors among Filipinos

BACKGROUNDColorectal cancer (CRC) ranks third in terms of incidence and second in mortality worldwide. In CRC, the silencing of mismatch repair genes, including the mutL homolog 1 (hMLH1) has been linked to microsatellite instability (MSI), the lengthening or shortening of microsatellite repeats. Very limited data have been presented so far on the link of hMLH1 methylation and MSI in Southeast Asia populations with sporadic CRC, and on its clinical significance.AIMTo investigate the significance of the MSI status and hMLH1 methylation in CRC Filipino patients.METHODSFifty-four sporadic CRC patients with complete clinical data were included in this study. Genomic DNA from CRC tumor biopsies and their normal tissue counterparts were profiled for MSI by high resolution melting (HRM) analysis using the Bethesda Panel of Markers (BAT25, BAT26, D2S123, D5S346, and D17S250). hMLH1 methylation screening was performed using bisulfite conversion and methylation specific polymerase chain reaction. Statistical analysis was conducted to calculate their associations to clinicopathological characteristics and survival relevance (Kaplan-Meier curves and the log-rank test).RESULTS hMLH1 methylation was observed in 9% and 35% of CRC and normal samples, respectively. Higher incidence of consistently methylated hMLH1 found in both normal and CRC was noticed for relation to location of tumor (P < 0.05). As for MSI status, D2S123 the most common unstable microsatellite and MSI-high (MSI-H) was the most common MSI profile, counted for 46% and 50% of normal and CRC tissues, respectively. The presence of MSI-low (MSI-L) and microsatellite stable (MSS) was 43% and 11% for normal, and 31% and 19% for CRC samples. The mean month of patients’ survival was shorter in patients whose normal and tumor tissues had methylated compared to those with unmethylated hMLH1 and with MSI-H compared to those with MSI-L/MSS (P < 0.05). This was supported by significant difference in Kaplan-Meier with log-rank analysis. This data indicated that hMLH1 methylation and high MSI status have prognostic value.CONCLUSIONThis study showed the clinical significance of hMLH1 methylation and MSI status in sporadic CRC Filipino patients, especially in the normal part of the tumor.     

Clinical implications of mismatch repair deficiency screening in patients with mixed neuroendocrine non-neuroendocrine neoplasms (MiNEN)

IntroductionMixed neuroendocrine non-neuroendocrine neoplasms (MiNEN) are rare tumors, mainly encountered in the gastroenteropancreatic tract. Based on the limited available data, MiNEN is usually a highly aggressive neoplasm combining a high-grade neuroendocrine and a non-neuroendocrine component, associated with a poor prognostic outlook. Deficient DNA mismatch repair (MMR) results in microsatellite instability, which is a useful screening marker for identifying patients with Lynch syndrome and a prognostic factor for chemotherapeutic interventions. Little information on MMR status in MiNEN is available in published studies. Therefore, the purpose of this study was to explore the status and putative role of MMR on MiNEN.MethodsWe investigated the MMR status in 44 cases and characterized their clinicopathological features and prognoses. Immunohistochemistry was performed for four mismatch repair proteins (MLH1, MSH2, MSH6, and PMS2).ResultsMean age at diagnosis was 61 years, and 75% of the patients were male. Lymph node metastases were observed in 14 (35.9%) patients. The most common tumor localizations were gastric (28 patients, 63.6%). Lack of immunohistochemical expression of MMR proteins was shown in 38.6% of cases. The common deletion rates of one or more proteins were 29.4% (5/17) for MLH1/PMS2 and 23.5% (4/17) for MLH1. Correlation between clinicopathological parameters showed that MMR deficiency was significantly associated with early TNM stage and better prognoses in patients with MiNEN.ConclusionMiNENs showed frequent losses of MMR protein expression, which contributes to the knowledge of the pathological and clinical aspects of MiNEN tumors.     

散发性结直肠癌的分子机制研究进展

结直肠癌是最常见的恶性肿瘤之一,其病因和发病机制十分复杂。大部分肠癌都是非遗传性的“散发性肠癌”,散发性肠癌是在环境因素影响下遗传和表观遗传学相继改变并累积,最终导致体细胞突变而发生的复杂的异质性疾病。其中最主要的三类基因变化是:染色体的不稳定性(CIN)、微卫星的不稳定性(MSI)和CpG岛甲基化表型(CIMP),表观遗传学变化是DNA的甲基化、组蛋白修饰、MicroRNA的改变。有些患者可能会有二至三种不同变化途径的同时呈现。更加透彻得理解肠癌发生发展背后分子生物学途径的变化将会有助于改善我们对肠癌的预防、监测、诊断和治疗策略。本文围绕结直肠癌发病的分子生物学机制的最新研究进展做一综述。     

Deficient mismatch repair system in patients with sporadic advanced colorectal cancer

A deficient mismatch repair system (dMMR) is present in 10–20% of patients with sporadic colorectal cancer (CRC) and is associated with a favourable prognosis in early stage disease. Data on patients with advanced disease are scarce. Our aim was to investigate the incidence and outcome of sporadic dMMR in advanced CRC. Data were collected from a phase III study in 820 advanced CRC patients. Expression of mismatch repair proteins was examined by immunohistochemistry. In addition microsatellite instability analysis was performed and the methylation status of the MLH1 promoter was assessed. We then correlated MMR status to clinical outcome. Deficient mismatch repair was found in only 18 (3.5%) out of 515 evaluable patients, of which 13 were caused by hypermethylation of the MLH1 promoter. The median overall survival in proficient MMR (pMMR), dMMR caused by hypermethylation of the MLH1 promoter and total dMMR was 17.9 months (95% confidence interval 16.2–18.8), 7.4 months (95% CI 3.7–16.9) and 10.2 months (95% CI 5.9–19.8), respectively. The disease control rate in pMMR and dMMR patients was 83% (95% CI 79–86%) and 56% (30–80%), respectively. We conclude that dMMR is rare in patients with sporadic advanced CRC. This supports the hypothesis that dMMR tumours have a reduced metastatic potential, as is observed in dMMR patients with early stage disease. The low incidence of dMMR does not allow drawing meaningful conclusions about the outcome of treatment in these patients.