遗传性非息肉病性大肠癌的研究进展

遗传性非息肉病性大肠癌(HNPCC)是一种由错配修复基因(MMR)突变造成的常染色体显性遗传病,又称Lynch综合征,是遗传性大肠癌的代表.HNPCC约占全部大肠癌的5%-15%.错配修复基因(MMR)的种系突变和微卫星不稳定(MSI)是其分子遗传学基础.HNPCC的临床病理特点突出,具有右半结肠多见、发病早、病理分化差、多原发癌多见的特点.目前其治疗方法以手术为主,COX-2阻滞剂可能成为HNPCC治疗的一个新的途径.近年来分子生物学的进展也为人们对HNPCC生物学行为和治疗的认识提供了有益的参考.     

Two novel germline mutations of MLH1 and investigation of their pathobiology in hereditary non-polyposis colorectal cancer families in China

AIM： To detect germline mutations of MLH1, and investigate microsatellite instability and expression of MLH1 in tumor tissues of hereditary non-polyposis colorectal cancer （HNPCC） with two novel germline mutations, and further investigate the pathobiology of the two novel mutations of MLH1. METHODS： RNA was extracted from the peripheral blood of 12 patients from 12 different families that fulfilled the Amsterdam 11 Criteria for HNPCC. Germline mutations of MLH1 were determined by RT-PCR, followed by cDNA sequencing analysis. PCR-GeneScan analysis was used to investigate microsatellite instability with a panel of five microsatellite markers （BAT26, BAT25, D5S346, D2S123 and mfd15）, along with immunohistochemical staining to detect the expression of MLH1 protein in two patients＇ tumor tissues with novel mutations. RESULTS： Three germline mutations were found in four patients, one of the mutations has previously been reported, but the other two, CGC→TGC at codon 217 of exon 8 and CCG→CTG at codon 581 of exon 16, have not been reported. The two patients＇ tumor tissues with novel mutations had high-frequency microsatellite instability that showed more than two unstable loci, and both tumors lost their MLH1 protein expression. CONCLUSION： The two novel germline mutations of MLH1 in HNPCC families i.e. CGC→TGC at codon 217 of exon 8 and CCG→CTG at codon 581 of exon 16, are very likely to have pathological significance.     

A novel <Emphasis Type="Italic">MSH2</Emphasis> mutation in a Chinese family with hereditary non-polyposis colorectal cancer

Background and aims Hereditary non-polyposis colorectal cancer (HNPCC) is one of the most common hereditary colon cancer syndrome accounting for 1–5% of all colorectal cancer cases. Germline mutations in DNA mismatch repair (MMR) genes are associated with the clinical phenotype of HNPCC. Defects in the MSH2 gene may account for about 40% of HNPCC cases including nucleotide substitutions, deletions and insertions. Only a few mutations were reported in Chinese families. This study was performed to identify the disease-causing gene mutation(s) and conduct pre-symptomatic diagnosis in a Chinese family with HNPCC. Materials and methods Mutation analysis in MLH1 and MSH2 followed by pre-symptomatic diagnosis in MSH2 was performed on genomic DNA isolated from the family members. Results A novel duplication mutation of four nucleotides in exon 7 of MSH2 (MSH2: c.1216_1219dupCGAC) resulting in a premature stop 10 codons downstream in MSH2 (p.L407fsX417) was found. The mutation was associated with HNPCC and an asymptomatic carrier was found in the family. Conclusion HNPCC in a Chinese family is associated with a novel mutation in the MSH2 gene (MSH2: c.1216_1219dupCGAC). Duo Zheng, Tiegang Li and Xiaoping Liu have contributed equally to this work.     

Molecular signaling mechanisms of apoptosis in hereditary non-polyposis colorectal cancer

Colorectal cancer is the second most leading cause of cancer related deaths in the western countries. One of the forms of colorectal cancer is hereditary non-polyposis colorectal cancer (HNPCC), also known as "Lynch syndrome". It is the most common hereditary form of cancer accounting for 5%-10% of all colon cancers. HNPCC is a dominant autosomal genetic disorder caused by germ line mutations in mismatch repair genes. Human mismatch repair genes play a crucial role in genetic stability of DNA, the inactivation of which results in an increased rate of mutation and often a loss of mismatch repair function. Recent studies have shown that certain mismatch repair genes are involved in the regulation of key cellular processes including apoptosis. Thus, differential expression of mismatch repair genes particularly the contributions of MLH1 and MSH2 play important roles in therapeutic resistance to certain cytotoxic drugs such as cisplatin that is used normally as chemoprevention. An understanding of the role of mismatch repair genes in molecular signaling mechanism of apoptosis and its involvement in HNPCC needs attention for further work into this important area of cancer research, and this review article is intended to accomplish that goal of linkage of apoptosis with HNPCC. The current review was not intended to provide a comprehensive enumeration of the entire body of literature in the area of HNPCC or mismatch repair system or apoptosis; it is rather intended to focus primarily on the current state of knowledge of the role of mismatch repair proteins in molecular signaling mechanism of apoptosis as it relates to understanding of HNPCC.     

Genetic diagnosis strategy of hereditary non-polyposis colorectal cancer

AIM： To study the characteristics of mismatch repair gene mutation of Chinese hereditary non-polyposis colorectal cancer （HNPCC） and hMLH1 gene promoter methylation, and to improve the screening strategy and explore the pertinent test methods. METHODS： A systematic analysis of 30 probands from HNPCC families in the north of China was performed by immunohistochemistry, microsatellite instability （MSI）, gene mutation and methylation detection. RESULTS： High frequency microsatellite instability occurred in 25 probands （83.3%） of HNPCC family. Loss of hMLH1 and hMSH2 protein expression accounted for 88% of all microsatellite instability. Pathogenic mutation occurred in 14 samples and 3 novel mutational sites were discovered. Deletion of exons 1-6, 1-7 and 8 of hMSH2 was detected in 3 samples and no large fragment deletion was found in hMLH1. Of the 30 probands, hMLH1 gene promoter methylation occurred in 3 probands. The rate of gene micromutation detection combined with large fragment deletion detection was 46.7%-56.7%. The rate of the two methods in combination with methylation detection was 63.3%. CONCLUSION： Scientific and rational detection strategy can improve the detection rate of HNPCC. Based on traditional molecular genetics and combined with epigenetics, multiple detection methods can accurately diagnose HNPCC.     

Three novel missense germline mutations in different exons of MSH6 gene in Chinese hereditary non-polyposis colorectal cancer families

AIM To investigate the germline mutations of MSH6 gene in probands of Chinese hereditary non-polyposis colorectal cancer (HNPCC) families fulfilling different clinical criteria.METHODS Germline mutations of MSH6 gene were detected by PCR-based DNA sequencing in 39 unrelated HNPCC probands fulfilling different clinical criteria in which MSH2 and MLH1 mutations were excluded. To further investigate the pathological effects of detected missense mutations, we analyzed the above related MSH6 exons using PCR-based sequencing in 137 healthy persons with no family history. The clinicopathological features were collected from the Archive Library of Cancer Hospital, Fudan University and analyzed.RESULTS Four germline missense mutations distributed in the 4th, 6th and 9th exons were observed. Of them,three were not found in international HNPCC databases and did not occur in 137 healthy controls, indicating that they were novel missense mutations. The remaining mutation which is consistent with the case H14 at c.3488A＞T of exon 6 of MSH6 gene was also found in the controls, the rate was approximately 3.65%(5/137) and the type of mutation was not found in the international HNPCC mutational and SNP databases,suggesting that this missense mutation was a new SNP unreported up to date.CONCLUSION Three novel missense mutations and a new SNP observed in the probands of Chinese HNPCC families, may play an important role in the development of HNPCC.     

MLH1 promoter germline-methylation in selected probands of Chinese hereditary non-polyposis colorectal cancer families

AIM： To detect the MLH1 gene promoter germline- methylation in probands of Chinese hereditary non- polyposis colorectal cancer （HNPCC）, and to evaluate the role of methylation in MLH1 gene promoter and molecular genetics in screening for HNPCC.METHODS： The promoter germline methylation of MLH1 gene was detected by methylation-specific PCR （MSP） in 18 probands from unrelated HNPCC families with high microsatellite-instability （MSI-H） phenotype but without germline mutations in MSH2, MLH1 and MSH6 genes. At the same time, 6 kindreds were col- lected with microsatellite-stability （MSS） phenotype but without germline mutations in MSH2, MIH1 and MSH6 genes as controls. The results of MSP were confirmed by clone sequencing. To ensure the reliability of the results, family H65 with nonsense germline mutation at c.2228C 〉 A in MSH2 gene was used as the negative control and the cell line sw48 was used as the known positive control along with water as the blank control. Immunochemical staining of MIH1 protein was performed with Envision two-step method in those patients with aberrant methylation to judge whether the status of MLH1 gene methylation affects the expression of MLH1 protein.RESULTS： Five probands with MIH1 gene promoter methylation were detected in 18 Chinese HNPCC families with MSI-H phenotype but without germline mutations in MSH2, MLH1 and MSH6 genes. Two of the five probands from families H10 and H29 displayed exhaustive-methylation, fulfilling the Japanese criteria （JC） and the Amsterdam criteria （AC）, respectively. The other 3 probands presented part-methylation fulfilling the AC. Of the 13 probands with unmethylation phenotype, 8 fulfilled the JC and the Bethesda guidelines （BG）, 5 fulfilled the AC. The rate of aberrant methylation in MLH1 gene in the AC group （22.2%, 4/18） was higher than that in the JC/BG groups （5.6%, 1/18） in all HNPCC families with MSI-H phenotype but without germline mutations in PISH2, PIIH1 and MSH6 genes. However, no proband with methy     

MS-HRM在遗传性非息肉性大肠癌筛查中的应用

目的探讨甲基化敏感性高分辨率熔解曲线分析(MS-HRM)在遗传性非息肉性大肠癌(HNPCC)筛查中的应用价值。方法采用实时荧光定量PCR技术检测miR-195在41例散发性大肠癌(SCRC)和9例HNPCC患者癌组织及对应癌旁正常组织(距离癌组织5 cm)中的表达水平,随后使用MS-HRM检测miR-195启动子区域CpG岛甲基化情况。结果 miR-195在HNPCC癌组织中的表达量为1.20±1.48,甲基化比例为55.56%(5/9);miR-195在SCRC组织中的表达量为0.76±1.06,甲基化比例为58.54%(24/41),差异无统计学意义(P0.05);miR-195在肠癌组织及癌旁正常组织中的平均表达水平分别为0.837±1.145和2.236±2.468,差异具有统计学意义(P0.05)。结论 miR-195在SCRC和HNPCC癌组织中的表达有无差异尚待进一步研究。miR-195可能有助于抑制肠癌发展,并且因其甲基化而参于大肠癌的发病机制。     

Novel MLH1 frameshift mutation in an extended hereditary nonpolyposis colorectal cancer family

~~Novel MLH1 frameshift mutation in an extended hereditary nonpolyposis colorectal cancer family@Tanya Kirilova Kadiyska$Laboratory of Molecular Pathology, University Hospital of Obstetrics and Gynecology, Bulgaria @Radka Petrova Kaneva$Laboratory of M…     

DNA microsatellite instability and mismatch repair protein loss in adenomas presenting in hereditary non-polyposis colorectal cancer

BACKGROUND AND AIM: Hereditary non-polyposis colorectal cancer (HNPCC), as its name implies, is associated with few adenomas, and the early evolution of colorectal neoplasia is poorly understood. In this study our aim was to clarify the genetic profiles of benign polyps in subjects with HNPCC using a combined molecular and immunohistochemical approach. METHODS: Thirty adenomas and 17 hyperplastic polyps were obtained from 24 affected HNPCC subjects. DNA was extracted from paraffin embedded tissue by microdissection and analysed for the presence of microsatellite instability (MSI) and mutations in five genes known to be targets in mismatch repair deficiency (TGFbetaRII, IGF2R, BAX, hMSH3, and hMSH6). Serial sections were stained by immunohistochemistry for hMLH1 and hMSH2. RESULTS: Twenty four (80%) of 30 adenomas showed MSI. Of MSI positive adenomas, 66.7% showed MSI at more than 40% of markers (high level of MSI (MSI-H)). Two of 17 hyperplastic polyps revealed MSI at one marker (low level of MSI (MSI-L)). A significant association was found between MSI-H and high grade dysplasia in adenomas (p=0.004). Eight of nine adenomas with mutations of coding sequences revealed high grade dysplasia and all nine were MSI-H. Four of the nine ranged in size from 2 to 5 mm. The presence of the hMSH6 mutation was significantly correlated with high levels of MSI (80% of markers) (p<0.02). Twenty four adenomas gave evaluable results with immunohistochemistry. One of six (17%) microsatellite stable, six of seven (86%) MSI-L, and 11 of 11 (100%) MSI-H adenomas showed loss of either hMLH1 or hMSH2. CONCLUSIONS: Most adenomas in subjects with a definite diagnosis of HNPCC show MSI (80%). The finding of MSI-L is usually associated with loss of expression of hMLH1 or hMSH2, unlike the situation in MSI-L sporadic colorectal cancer. The transition from MSI-L to MSI-H correlated with the finding of high grade dysplasia and mutation of coding sequences and may be driven by mutation of secondary mutators such as hMSH3 and hMSH6. Advanced genetic changes may be present in adenomas of minute size.     

北方人群HNPCC微卫星不稳定性和错配修复基因突变规律研究

目的探讨中国北方人群遗传性非息肉病性结直肠癌（HNPCC）微卫星不稳定性（MSI）和错配修复（MMR）基因突变的特征。方法通过MSI检测和MMR基因种系突变检测对30个中国北方人HNPCC家系进行系统分析。结果①25个家系表现为高度微卫星不稳定（MSI-H）,1个家系为低度微卫星不稳定（MSI-L）,4个家系表现为微卫星稳定（MSS）;②在25个MSI-H家系的先证者中,检测到14种致病性种系突变（hMLH1基因突变9种,hMSH2基因突变5种）,突变类型包括框移突变、无义突变、剪接区突变、错义突变,并发现3种新突变位点。结论中国北方人群HNPCC的错配修复基因突变谱广泛而多样,应开展系统研究,以建立北方人群的HNPCC错配修复基因突变库并制定相应的突变检测策略。     

遗传性非息肉病性结直肠癌的微卫星不稳定研究

目的　探讨国人北方人群HNPCC的微卫星不稳定 (microsatelliteinstability ,MSI)发生情况及其意义。方法　 44例患者来源于 3 0个HNPCC (hereditarynonpolyposiscolorectalcancer)家系 ,这些家系主要分布于北方 5省市。所有患者均符合BGl 3 (Bethes dal 3 )HNPCC诊断标准。以荧光标记法检测 44例患者的石蜡包埋组织微卫星稳定性。结果　 44例患者中高度微卫星不稳定 (highfrequencymicrosatelliteinstability ,MSI H)为 81.81( 3 6/ 44 ) ,低度微卫星不稳定 (lowfrequencymicrosatelliteinstability ,MSI L)为 6.82 ( 3 / 44 ) ,微卫星稳定 (microsatellitestable ,MSS)为 11.3 ( 5 / 44 ) ;所选择的 5个微卫星位点中Bat2 5和Bat2 62个位点MSI H的表达率较高 ,分别为 10 0 %和 97.2 2 %。符合AmsterdamⅡ和符合BGl 3标准的HNPCC患者的MSI H表达率分别为 85 .2 9%和 81,81% ,仅符合BGl 3标准 ,而不符合AmsterdamII的 10个患者中 ,7个发现MSI H。结论　HNPCC肿瘤的MSI H发生率高 ,MSI检测方法简便、易行 ,可作为错配修复基因种系突变初筛方法 ,Bethesdal 3标准可更多地收集到可疑的HNPCC患者     

Risk of colon cancer in hereditary non-polyposis colorectal cancer patients as predicted by fuzzy modeling： Influence of smoking

AIM: To investigate whether a fuzzy logic model could predict colorectal cancer (CRC) risk engendered by smoking in hereditary non-polyposis colorectal cancer (HNPCC) patients. METHODS: Three hundred and forty HNPCC mismatch repair (MMR) mutation carriers from the Creighton University Hereditary Cancer Institute Registry were selected for modeling. Age-dependent curves were generated to elucidate the joint effects between gene mutation (hMLH1 or hMSH2), gender, and smoking status on the probability of developing CRC. RESULTS: Smoking significantly increased CRC risk in male hMSH2 mutation carriers (P < 0.05). hMLHl mutations augmented CRC risk relative to hMSH2 mutation carriers for males (P < 0.05). Males had a significantly higher risk of CRC than females for hMLHl non smokers (P < 0.05), hMLHl smokers (P < 0.1) and hMSH2 smokers (P < 0.1). Smoking promoted CRC in a dose-dependent manner in hMSH2 in males (P < 0.05). Females with hMSH2 mutations and both sexes with the hMLHl groups only demonstrated a smoking effect after an extensive smoking history (P < 0.05). CONCLUSION: CRC promotion by smoking in HNPCC patients is dependent on gene mutation, gender and age. These data demonstrate that fuzzy modeling may enable formulation of clinical risk scores, thereby allowing individualization of CRC prevention strategies.     

遗传性非息肉病性大肠癌6家系临床分析

目的总结遗传性非息肉病性大肠癌(HNPCC)的临床特征,提高其早期诊断和治疗水平。方法对我院6个HNPCC家系进行调查,记录患者性别、发病年龄、肿瘤部位等。结果6个家系有大肠癌患者19例,占同期所有大肠癌的2.7%。其中男性10例,女性9例;发病年龄为26～74岁,中位年龄为53.4岁;共有大肠癌病灶23处,60.9%位于右半结肠,多原发大肠癌有4例。另有大肠腺瘤患者2例,白血病患者1例,原发性肝癌患者1例。结论HNPCC有明显的临床特征,利用这些特征有助于早期诊断和提高防治效果。     

Colonic epithelial cell proliferation in hereditary non-polyposis colorectal cancer

Background—Despite the recentdiscovery of four genes responsible for up to 90% of all cases ofhereditary non-polyposis colorectal cancer (HNPCC), there will still befamilies in whom predictive testing is not possible. A phenotypicbiomarker would therefore be useful. An upwards shift of theproliferative compartment in colonic crypts is reported to be one ofthe earliest changes in premalignant mucosa.
Aims—To assess the role of cryptcell proliferation as a phenotypic biomarker in HNPCC.
Patients—Thirty five patients at50% risk of carrying the HNPCC gene (21 of whom subsequently underwentpredictive testing and hence gene carrier status was known) and 18controls.
Methods—Crypt cell proliferationwas measured at five sites in the colon using two different techniques.Labelling index was determined using the monoclonal antibody MIB1 andwhole crypt mitotic index was measured using the microdissection andcrypt squash technique. The distribution of proliferating cells within the crypts was also assessed.
Results—There were no significantdifferences in the total labelling index or mean number of mitoses percrypt, nor in the distribution of proliferating cells within the crypt,between the study and control groups at any site. When the 21 patients in whom gene carrier status was known were analysed separately therewere no significant differences in the measured indices ofproliferation between the HNPCC gene carriers and non-gene carriers.
Conclusion—Crypt cell proliferationis not a discriminative marker of gene carriage in HNPCC.

Keywords:cell proliferation; hereditary non-polyposiscolorectal cancer

     

Endoscopic surveillance for hereditary non-polyposis colorectal cancer (HNPCC) family members in a Southern Italian region

Background

Surveillance in hereditary non-polyposis colorectal cancer (HNPCC) family members recommends baseline colonoscopy starting at age 20 and then surveillance colonoscopy every 1–2 years.

Aims

To verify adherence to the guidelines for HNPCC family members enrolled in endoscopic surveillance.

Methods

Data regarding 11 HNPCC families was retrieved from our database. Excluding 11 probands, 106 family members were evaluated and 40 underwent surveillance.

Results

At baseline colonoscopy, 7 colorectal cancers (CRC), 14 polyps (PO) [1 inflammatory, 2 hyperplastic, 10 adenomas with low grade dysplasia (LGD-AD) and 1 adenoma with high-grade dysplasia (HGD-AD)] were diagnosed in sixteen individuals. Twenty-eight HNPCC family members underwent endoscopic surveillance, with a total of 94 surveillance colonoscopies. Of these, 45 were positive (4 CRC, 3 inflammatory PO, 34 hyperplastic PO, 21 LGD-AD and 5 HGD-AD).Mean time between two consecutive surveillance colonoscopies was 24.6 months (range 4–168). Median time to first positive surveillance colonoscopy was 84 months for HNPCC family members with negative baseline colonoscopy, and 60 months for those with positive baseline colonoscopy (p = 0.21).

Conclusions

Our data suggests that surveillance colonoscopy every 2 years is adequate to diagnose advanced lesions in HNPCC family members, and improves their compliance with surveillance.     

Role of detection of microsatellite instability in Chinese with hereditary nonpolyposis colorectal cancer or ordinary hereditary colorectal cancer

AIM: To detect microsatellite instability (MSI) in patients with hereditary nonpolyposis colorectal cancer or ordinary hereditary colorectal cancer and to provide criteria for screening the kindreds with hereditary nonpolyposis colorectal cancer at molecular level. METHODS: MSI was detected in the specimens from 20 cases with HNPCC, 20 cases with ordinary hereditary colorectal cancer and 20 cases with sporadic colorectal cancer by means of polymerase chain reaction-single strand conformation polymorphism. RESULTS: The positive rate of MSI was 85% (17/20) in HNPCC group, 40% (8/20) in ordinary hereditary colorectal cancer group and 10% (2/20) in the sporadic colorectal cancer group respectively. The differences were significant. The mean ages of the three groups were 43.6, 52.2, and 61.8 years respectively, which increased gradually. The incidence of right hemicolon cancer was 64.7%, 37.5%, and 0% respectively, which decreased gradually and had significant difference. The expression ratio of BAT26 and BAT25 was 94.1% respectively, which was highest in the 5 gene sites studied. The incidence of poorly differentiated adenocarcinoma was 70.6% in HNPCC group among high frequency microsatellite instability (MSI-H), which was higher than the other two groups, which had 50% and 50% respectively. CONCLUSION: The incidence of MSI-H is higher in HNPCC group. The detection of MSI is simple and economical and has high correlation with the clinicopathologic feature of HNPCC and can be used as a screening method to detect the germ line mutation of the mismatch repair gene.     

Clinical and molecular features of young-onset colorectal cancer

Colorectal cancer(CRC) is one of the leading causes of cancer related mortality worldwide. Although young-onset CRC raises the possibility of a hereditary component, hereditary CRC syndromes only explain a minority of young-onset CRC cases. There is evidence to suggest that young-onset CRC have a different molecular profile than late-onset CRC. While the pathogenesis of young-onset CRC is well characterized in individuals with an inherited CRC syndrome, knowledge regarding the molecular features of sporadic young-onset CRC is limited. Understanding the molecular mechanisms of young-onset CRC can help us tailor specific screening and management strategies. While the incidence of late-onset CRC has been decreasing, mainly attributed to an increase in CRC screening, the incidence of young-onset CRC is increasing. Differences in the molecular biology of these tumors and low suspicion of CRC in young symptomatic individuals, may be possible explanations. Currently there is no evidence that supports that screening of average risk individuals less than 50 years of age will translate into early detection or increased survival. However, increasing understanding of the underlying molecular mechanisms of young-onset CRC could help us tailor specific screening and management strategies. The purpose of this review is to evaluate the current knowledge about young-onset CRC, its clinicopathologic features, and the newly recognized molecular alterations involved in tumor progression.     

Microsatellite instability—a useful diagnostic tool to select patients at high risk for hereditary non-polyposis colorectal cancer: a study in different groups of patients with colorectal cancer

BACKGROUND: Clinical diagnosis of hereditary non-polyposis colorectal cancer (HNPCC) is based on a typical family history. As molecular genetic testing is predominantly restricted to these families, gene carriers not meeting the clinical criteria may be missed. AIMS: To examine the value of microsatellite instability (MSI) as a tool to increase the likelihood for uncovering a mismatch repair germline mutation in patients with colorectal cancer and to identify a genotype-phenotype relation in families with verified mutations. METHODS: Systematic search for germline mutations (hMSH2 and hMLH1 genes) was performed in 96 patients: 57 fulfilled the Amsterdam criteria (group 1) and 12 the looser HNPCC criteria (group 2). Seventeen patients showed familial clustering of cancers (group 3) and 10 patients under 50 years had sporadic cancer (group 4), the latter of whom all exhibited MSI+ tumours. RESULTS: A similar proportion of germline mutations was found in patients who fulfilled the clinical criteria of HNPCC and had MSI+ tumours (groups 1 and 2; 15/39) compared with patients who did not meet these clinical criteria but who had MSI+ tumours (groups 3 and 4; 8/27 patients). Affected relatives of patients with hMLH1 mutations showed a significantly higher frequency of colorectal cancer but a lower frequency of endometrium cancer than those with hMSH2 mutations. CONCLUSIONS: MSI in tumour tissue is a useful criterion for selecting patients who should be tested for germline mutations in the mismatch repair genes hMSH2 and hMLH1 irrespective of their family history. Among carriers of hMSH2 mutations the tumour spectrum was broader than among carriers of hMLH1 mutations.