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Monoallelic PMS2 germline mutations cause 5-15% of Lynch syndrome, a midlife cancer predisposition, whereas biallelic PMS2 mutations cause approximately 60% of constitutional MMR deficiency (CMMRD), a rare childhood cancer syndrome. Recently improved DNA and RNA-based strategies are applied to overcome problematic PMS2 mutation analysis due to the presence of pseudogenes and frequent gene conversion events. Here, we determined PMS2 mutation detection yield and mutation spectrum in a nationwide cohort of 396 probands. Furthermore, we studied concordance between tumor IHC/ MSI (immunohistochemistry/ microsatellite-instability) profile and mutation carrier state. Overall, we found 52 different pathogenic PMS2 variants explaining 121 Lynch syndrome and nine CMMRD patients. In vitro MMR assays suggested pathogenicity for three missense variants. Ninety-one PMS2 mutation carriers (70%) showed isolated loss of PMS2 in their tumors, for 31 (24%) no or inconclusive IHC was available, and eight carriers (6%) showed discordant IHC (presence of PMS2 or loss of both MLH1 and PMS2). Ten cases with isolated PMS2 loss (10%; 10/97) harbored MLH1 mutations. We confirmed that recently improved mutation analysis provides a high yield of PMS2 mutations in patients with isolated loss of PMS2 expression. Application of universal tumor pre-screening methods will however miss some PMS2 germline mutation carriers. This article is protected by copyright. All rights reserved.

A progressive accumulation of genetic alterations underlies the adenoma-carcinoma sequence of colorectal cancer. This accumulation of mutations is driven by genetic instability, of which there are different types. Microsatellite instability (MSI) is the predominant type present in the tumours of Lynch syndrome patients and in a subset of sporadic tumours. It is generally accepted that MSI can be found in the early stages of tumour progression, such as adenomas; however, the frequencies reported vary widely among studies. Moreover, data on the qualitative differences between adenomas and carcinomas, or between tumours of hereditary and sporadic origin, are scarce. We compared MSI in samples of colorectal adenoma and colorectal carcinoma in order to identify possible differences along the adenoma-carcinoma sequence. We compared germline mismatch repair (MMR) gene mutation carriers and non-carriers, to address possible differences of instability patterns between Lynch syndrome patients and patients with sporadic tumours. We found a comparable relative frequency of mono- and dinucleotide instability in sporadic colorectal adenomas and carcinomas, dinucleotide instability being observed most frequently in these sporadic tumours. In MMR gene truncating mutation carriers, the profile was different: colorectal adenomas showed predominantly mononucleotide instability and in colorectal carcinomas, also more mononucleotide than dinucleotide instability was detected. We conclude that MSI profiles differ between sporadic and Lynch syndrome tumours, and that mononucleotide marker instability precedes dinucleotide marker instability during colorectal tumour development in Lynch syndrome patients. As mononucleotide MSI proves to be highly sensitive for detecting mutation carriers, we propose the use of mononucleotide markers for the identification of possible Lynch syndrome patients. Copyright (C) 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Colorectal cancer (CC) is the secondary cause of death in the Western countries of which approximately 15% are considered to be hereditary. The hereditary forms are Familial Adenomatous Polyposis (FAP) and Hereditary Non Polyposis Colorectal Cancer (HNPCC) which is the commonest form. The detection of mutations in the MMR and apc related genes, allows the development of health prevention strategies. Different molecular diagnostic strategies are available for the detection of mutations in these genes, i.e. DGGE, SSCP and direct sequencing. However, deletions and duplications of one or more consecutive exons, which account for around 50% of the total alterations in MMR genes, cannot be detected by PCR based methodologies due to the non quantitative nature of these techniques. The aim of our work has been the standardization of a methodology, called Multiplex Ligation-Dependent Probe Amplification, which allows the detection of genomic deletions and duplications as primary analysis in HNPCC and FAP patients in Argentina. In this case, we inform that the application of MLPA allowed the detection of a missence mutation, without the need for direct sequencing of the complete genes involved. A PCR/RFLP strategy was afterwards designed to detect the C

This report focuses on low-penetrance genes that are associated with colorectal adenoma and/or cancer or that are in strong linkage disequilibrium with colorectal adenoma and/or cancer causing variants. A pooled analysis was performed for 30 polymorphisms in 20 different genes that have been reported in more than one colorectal adenoma or cancer study. An association with colorectal cancer was found for seven polymorphisms in seven genes reported in more than one study; no associations were found with colorectal adenoma. Four of the polymorphisms exhibited an increased colorectal cancer risk [GSTT1, NAT2 (phenotype), HRAS1, and ALDH2]. Two others [MTHFR, Tp53 (intron 3)] exhibited a decreased risk. For the tumor necrosis factor (TNF)a polymorphism of the TNF-alpha gene, one allele was associated with an increased risk (a2 allele) and two other TNFa alleles with decreased risks (a5 and a13 allele). No association with colorectal adenoma and/or cancer was detected for 23 other polymorphisms in 15 genes. However, of all 30 polymorphisms, only three pooled analyses had sufficiently large samples to confirm (MTHFR) or to exclude (GSTM1 and NAT2 genotype) the association with a P

Key points Hereditary non-polyposis colorectal cancer (HNPCC) is one of the most common cancer syndromes. The cancer susceptibility is dominantly inherited and associated with germline mutations in mismatch repair (MMR) genes. An inherited defect in one allele of a MMR gene and an acquired defect in the other allele leads to hypermutability associated with marked microsatellite instability (MSI) that accelerates tumour progression.1 To date, over 400 different mutations, affecting mostly the MMR genes MLH1 …

Contains fulltext : 137784.pdf (Publisher’s version ) (Closed access) PURPOSE: Dietary intake of B vitamins and methionine, essential components of DNA synthesis and methylation pathways, may influence colorectal tumor (CRT) development. The impact of B vitamins on colorectal carcinogenesis in individuals with Lynch syndrome (LS) is unknown but is important given their high lifetime risk of developing neoplasms. The role of MTHFR C677T genotype in modifying these relationships in LS individuals is also unclear. We investigated associations between dietary intakes of folate, vitamins B2, B6, B12, and methionine and CRT development in a prospective cohort study of 470 mismatch repair gene mutation carriers. METHODS: Dietary intakes were assessed by food frequency questionnaire. Cox regression models with robust sandwich covariance estimation, adjusted for age, sex, physical activity, number of colonoscopies during person-time, NSAID use, and mutual vitamins were used to calculate hazard ratios (HRs) and 95 % confidence intervals (95 % CIs). Analyses were also stratified by MTHFR C677T genotype. RESULTS: During a median person-time of 28.0 months, 131 persons developed a CRT. Fifty-one of these persons developed an incident colorectal adenoma, while there were four persons who developed an incident colorectal carcinoma. Compared to the lowest tertile of intake, adjusted HRs (95 % CIs) for CRT development in the highest tertile were 1.06 (0.59-1.91) for folate, 0.77 (0.39-1.51) for vitamin B2, 0.98 (0.59-1.62) for vitamin B6, 1.24 (0.77-2.00) for vitamin B12, and 1.36 (0.83-2.20) for methionine. Low vitamin B2 and low methionine intake were statistically significantly associated with an increased risk of CRT in MTHFR 677TT individuals compared to a combined reference of persons with low intake and CC genotype. CONCLUSIONS: There was no suggestion that intake of any dietary B vitamin or methionine was associated with CRT development among those with LS.

Hereditary non-polyposis colorectal cancer is an autosomal dominant inherited disorder that predisposes its carriers to an almost 100% lifetime risk of cancer, in particular colorectal and endometrial cancer. Germline mutations, resulting in a deficient DNA mismatch repair system. are responsible for the disease. Because of the lack of specific phenotypical features, clinical diagnosis in an individual patient is impossible and relies heavily on family history. Genetic diagnosis by mismatch detection is now possible in a substantial proportion of families. Thus there is a great need for reliable but simple criteria that will help clinicians to recognize patients and families who can be referred for genetic diagnostics. In this article the different criteria that have been formulated and published in recent years are reviewed and the results, in terms of the proportions of subjects satisfying the criteria who were found to have a germline mutation, are discussed. In most studies the criteria were evaluated in only a small number of subjects. A population-based study is currently being carried out in the north of The Netherlands that aims to include 400 patients fulfilling one of a few simple criteria. Mutation analysis will be performed in all patients, The results of this study will help in the formulation of accurate and simple criteria for use in clinical practice.

Replication errors (RER) are frequently seen in both sporadic and hereditary forms of colorectal cancer. In hereditary nonpolyposis colorectal cancer (HNPCC), RER is associated with defects in DNA mismatch repair genes. Two of these genes, MSH2 and MLH1, account for a major share of this cancer syndrome. In order to assess the role of these genes in sporadic RER+ colorectal carcinoma, we have carried out a mutation analysis of MSH2 and MLH1 by two-dimensional (2-D) DNA electrophoresis, including heteroduplexing and separation in a denaturing gradient. All exons were amplified using multiplex PCR and were separated on the basis of both size and base pair composition under a single set of experimental conditions. Exons showing a spot position different from normal were sequenced. In screening 33 unselected, sporadic RER+ colorectal tumors, a germline mutation accompanied by loss of heterozygosity in tumor tissue was found in two patients. They were among the 4 patients out of the 33 screened that were diagnosed before the age of 50 years. In 8 of the remaining 31 tumors (26%), presence of somatic mutations (9 in total) could be demonstrated. While suggesting involvement of other genes in a substantial part of sporadic RER+ colorectal carcinomas, our results also demonstrate a clear role of MSH2 and MLH1 in these sporadic tumors and show that young sporadic RER+ colorectal carcinoma patients have a high probability of germline mutations. This has important implications for genetic testing and management of young colorectal cancer patients and their families. (C) 1997 Wiley-Liss, Inc.

Hereditary non-polyposis colorectal cancer (HNPCC) is known to be associated with several extracolonic cancers, e.g., cancers of the endometrium, stomach, urinary tract, small bowel and ovary. An association between HNPCC and brain tumours has also been reported, although previous risk analysis did not reveal an excess of this type of tumour. To determine whether HNPCC predisposes patients to brain tumours, we used risk analysis to compare families with HNPCC to those in the general population. Of the 1,321 subjects from 50 HNPCC families (with 60,237 person-years of follow-up) in the Dutch HNPCC Registry which satisfy the Amsterdam Criteria, 312 had colorectal cancer. The registry revealed 14 brain tumours in the HNPCC-patients and their first-degree relatives: 5 astrocytomas, 3 oligodendrogliomas, 1 ependymoma and 5 tumours for which a pathological report was not available. The relative risk of brain tumour in patients with HNPCC and their first-degree relatives was 6 times greater than in the general population (95% confidence interval, 3.5 to 10.1). After exclusion of the cases based only on family history, the relative risk was 4.3 (95% confidence interval, 2.3 to 8.0). Although the relative risk of brain tumour was increased, the lifetime risk was low (3.35%). Because it is not certain whether an improvement of the overall prognosis can be achieved by early diagnosis and intervention, and in view of the low lifetime risk, we do not recommend screening for brain tumours in HNPCC families. (C) 1996 Wiley-Liss, Inc.

In certain circumstances, tumour tissue specimens are the only DNA resource available for forensic DNA analysis. However, cancer tissues can show microsatellite instability and loss of heterozygosity which, if concerning the short tandem repeats (STRs) used in the forensic field, can cause misinterpretation of the results. Moreover, though formalin-fixed paraffin-embedded tissues (FFPET) represent a large resource for these analyses, the quality of the DNA obtained from this kind of specimen can be an important limit. In this study, we evaluated the use of tumoural tissue as biological material for the determination of genetic profiles in the forensic field, highlighting which STR polymorphisms are more susceptible to tumour genetic alterations and which of the analysed tumours show a higher genetic variability. The analyses were conducted on samples of the same tissues conserved in different storage conditions, to compare genetic profiles obtained by frozen tissues and formalin-fixed paraffin-embedded tissues. The importance of this study is due to the large number of specimens analysed (122), the large number of polymorphisms analysed for each specimen (39), and the possibility to compare, many years after storage, the same tissue frozen and formalin-fixed paraffin-embedded. In the comparison between the genetic profiles of frozen tumour tissues and FFPET, the same genetic alterations have been reported in both kinds of specimens. However, FFPET showed new alterations. We conclude that the use of FFPET requires greater attention than frozen tissues in the results interpretation and great care in both pre-extraction and extraction processes.

A progressive accumulation of genetic alterations underlies the adenoma-carcinoma sequence of colorectal cancer. This accumulation of mutations is driven by genetic instability, of which there are different types. Microsatellite instability (MSI) is the predominant type present in the tumours of Lynch syndrome patients and in a subset of sporadic tumours. It is generally accepted that MSI can be found in the early stages of tumour progression, such as adenomas; however, the frequencies reported vary widely among studies. Moreover, data on the qualitative differences between adenomas and carcinomas, or between tumours of hereditary and sporadic origin, are scarce. We compared MSI in samples of colorectal adenoma and colorectal carcinoma in order to identify possible differences along the adenoma-carcinoma sequence. We compared germline mismatch repair (MMR) gene mutation carriers and non-carriers, to address possible differences of instability patterns between Lynch syndrome patients and patients with sporadic tumours. We found a comparable relative frequency of mono- and dinucleotide instability in sporadic colorectal adenomas and carcinomas, dinucleotide instability being observed most frequently in these sporadic tumours. In MMR gene truncating mutation carriers, the profile was different: colorectal adenomas showed predominantly mononucleotide instability and in colorectal carcinomas, also more mononucleotide than dinucleotide instability was detected. We conclude that MSI profiles differ between sporadic and Lynch syndrome tumours, and that mononucleotide marker instability precedes dinucleotide marker instability during colorectal tumour development in Lynch syndrome patients. As mononucleotide MSI proves to be highly sensitive for detecting mutation carriers, we propose the use of mononucleotide markers for the identification of possible Lynch syndrome patients. Copyright (C) 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Contains fulltext : 57104.pdf (Publisher’s version ) (Closed access) In sporadic colorectal tumours the BRAFV600E is associated with microsatellite instability (MSI-H) and inversely associated to KRAS mutations. Tumours from hereditary non-polyposis colorectal cancer (HNPCC) patients carrying germline mutations in hMSH2 or hMLH1 do not show BRAFV600E, however no consistent data exist regarding KRAS mutation frequency and spectrum in HNPCC tumours. We investigated KRAS in 158 HNPCC tumours from patients with germline hMLH1, hMSH2 or hMSH6 mutations, 166 MSI-H and 688 microsatellite stable (MSS) sporadic carcinomas. All tumours were characterized for MSI and 81 of 166 sporadic MSI-H colorectal cancer (CRCs) were analysed for hMLH1 promoter hypermethylation. KRAS mutations were observed in 40% of HNPCC tumours, and the mutation frequency varied upon the mismatch repair gene affected: 48% (29/61) in hMSH2, 32% (29/91) in hMLH1 and 83% (5/6) in hMSH6 (P = 0.01). KRAS mutation frequency was different between HNPCC, MSS and MSI-H CRCs (P = 0.002), and MSI-H with hMLH1 hypermethylation (P = 0.005). Furthermore, HNPCC CRCs had more G13D mutations than MSS (P < 0.0001), MSI-H (P = 0.02) or MSI-H tumours with hMLH1 hypermethylation (P = 0.03). HNPCC colorectal and sporadic MSI-H tumours without hMLH1 hypermethylation shared similar KRAS mutation frequency, in particular G13D. In conclusion, we show that depending on the genetic/epigenetic mechanism leading to MSI-H, the outcome in terms of oncogenic activation may be different, reinforcing the idea that HNPCC, sporadic MSI-H (depending on the hMLH1 status) and MSS CRCs, may target distinct kinases within the RAS/RAF/MAPK pathway.

This report focuses on low-penetrance genes that are associated with colorectal adenoma and/or cancer or that are in strong linkage disequilibrium with colorectal adenoma and/or cancer causing variants. A pooled analysis was performed for 30 polymorphisms in 20 different genes that have been reported in more than one colorectal adenoma or cancer study. An association with colorectal cancer was found for seven polymorphisms in seven genes reported in more than one study; no associations were found with colorectal adenoma. Four of the polymorphisms exhibited an increased colorectal cancer risk [GSTT1, NAT2 (phenotype), HRAS1, and ALDH2]. Two others [MTHFR, Tp53 (intron 3)] exhibited a decreased risk. For the tumor necrosis factor (TNF)a polymorphism of the TNF-alpha gene, one allele was associated with an increased risk (a2 allele) and two other TNFa alleles with decreased risks (a5 and a13 allele). No association with colorectal adenoma and/or cancer was detected for 23 other polymorphisms in 15 genes. However, of all 30 polymorphisms, only three pooled analyses had sufficiently large samples to confirm (MTHFR) or to exclude (GSTM1 and NAT2 genotype) the association with a P

To investigate whether cells from hereditary nonpolyposis colorectal cancer (HNPCC) patients, a genetic condition characterized by constitutional mutations in DNA mismatch repair genes and associated with predisposition to colorectal carcinoma (CRC), could present a higher G2 chromosomal radiosensitivity. It is generally hypothesized that cancer predisposition in HNPCC is associated with the loss of the wild-type allele in somatic cells, resulting in defective DNA mismatch repair but, to date, no data on G2 radiosensitivity have been reported for HNPCC.Lymphoblastoid cell lines derived from six HNPCC patients heterozygous for MLH1, one HNPCC patient carrying a mutant MSH2 allele and three healthy controls were treated with 50 cGy of X-rays and sampled at various harvesting times, monitoring cell-cycle progression by 5-bromo-2-deoxyuridine (BrdUrd) incorporation in order to analyse chromosomal damage in the homogeneous G2 population.There were no differences between lymphoblasts derived from patients in the frequency of G2 chromosomal aberrations induced by X-rays when compared with control cell lines. However, despite the absence of G2 radiosensitivity in HNPCC cells, lymphoblasts from patients heterozygous for MLH1 mutations showed a higher induction of chromatid exchanges.The observed possible incorrect rejoining of double-strand breaks in MLH1 heterozygotes would be an additional and important factor contributing to loss of heterozygosity in HNPCC patients.

Accumulation of mutations in tumour suppressor genes and oncogenes has been proposed to underlie the initiation and progression of sporadic colorectal cancer (CRC). Evidence is accumulating to suggest that the caudal homeobox gene CDX2 is implicated in the pathogenesis of CRC. The CDX2 transcription factor is expressed in intestinal epithelium and is markedly down-regulated in colon tumours. Furthermore, Cdx2 heterozygous null mice develop multiple intestinal tumours. In this present study, we have investigated CDX2 as a potential candidate gene for sporadic CRC by a thorough search of all exons and exon/intron boundaries for DNA polymorphisms and rare variants in a panel of CRC tumours. 6 polymorphisms were identified and the haplotypes determined. In addition two rare variants were found, one of which was only identified in DNA from a CRC case. Loss of heterozygosity was observed in 3 out of 28 informative CRC cases. A possible association between particular haplotypes and tumour progression was also suggested by the data. In addition a preliminary analysis of the relative expression of CDX2 alleles in tumour/normal tissue suggested some variation in the levels, however further analysis is required before any conclusions can be drawn. While CDX2 mutations predisposing to sporadic CRC have not been identified, this study has established that loss of CDX2 contributes towards the progression of some sporadic CRC tumours. © 2001 Cancer Research Campaign http://www.bjcancer.com

PURPOSE: The aim of this study was to define the prognostic role of microsatellite status in 65 stage I-II primary sporadic endometrioid endometrial adenocarcinoma (EEA) patients. PATIENTS AND METHODS: Familiarity for neoplasia was ascertained in all patients on the basis of a questionnaire. Microsatellite status was assessed by matching normal and tumoral DNA probed for five dinucleotide repeats and one mononucleotide repeat marker. Microsatellite status was analyzed in relation to clinicopathologic characteristics of the patients and length of disease-free survival (DFS). RESULTS: Eleven tumors (17%) of 65 had instability at two or more loci and were considered as unstable or microsatellite instability (MI). Tumors with no instability or instability at one locus were classified as microsatellite stable (MS). The percentage of MI was significantly higher in poorly than in well to moderately differentiated tumors (50% v 9%; P = .003). The 5-year DFS rate of MI patients was 63% (95% confidence interval [CI], 35% to 91%) versus 96% (95% CI, 91% to 101%) of MS patients (P = .0004). In multivariate analysis, only the presence of MI, stage II of disease, and depth of myometrial invasion greater than 50% retained independent prognostic roles. CONCLUSION: The assessment of microsatellite status may provide useful information for preoperative prognostic characterization of stage I-II primary sporadic EEA patients in which more individualized treatment options can be attempted.

Hereditary non-polyposis colorectal cancer is an autosomal dominant inherited disorder that predisposes its carriers to an almost 100% lifetime risk of cancer, in particular colorectal and endometrial cancer. Germline mutations, resulting in a deficient DNA mismatch repair system, are responsible for the disease. Because of the lack of specific phenotypical features, clinical diagnosis in an individual patient is impossible and relies heavily on family history. Genetic diagnosis by mismatch detection is now possible in a substantial proportion of families. Thus there is a great need for reliable but simple criteria that will help clinicians to recognize patients and families who can be referred for genetic diagnostics. In this article the different criteria that have been formulated and published in recent years are reviewed and the results, in terms of the proportions of subjects satisfying the criteria who were found to have a germline mutation, are discussed. In most studies the criteria were evaluated in only a small number of subjects. A population-based study is currently being carried out in the north of The Netherlands that aims to include 400 patients fulfilling one of a few simple criteria. Mutation analysis will be performed in all patients. The results of this study will help in the formulation of accurate and simple criteria for use in clinical practice.

BACKGROUND—Hereditary non-polyposis colorectal cancer (HNPCC) is one of the most common inherited disorders predisposing to cancer. The genes responsible for the disease have recently been cloned and characterised; their mutations induce a generalised genomic instability which is particularly evident at microsatellite loci (replication error (RER)+ phenotype). AIMS—To investigate how to select individuals and families in the general population who should be screened for constitutional mutations predisposing to colorectal cancer. PATIENTS/METHODS—Between 1984 and 1995, 1899 colorectal malignancies in 1831 patients were registered, and in 1721 of these (94%), family trees could be obtained. Patients and families were classified into five categories according to a more or less likely genetic basis: HNPCC; "suspected" HNPCC; juvenile cases; aspecific cancer aggregation; sporadic cases. In 18 families with HNPCC as well as in 18 with suspected HNPCC, microsatellite instability in tumour tissues and constitutional mutations of two DNA mismatch repair genes (MSH2 and MLH1) could be evaluated. RER status was studied with five markers (BAT40, D2S123, D18S57, D17S787, and BAT26) in paraffin embedded tissues. Germline mutations of MSH2 or MLH1 genes were assessed on DNA and RNA extracted from lymphomonocytic cells, using reverse transcription polymerase chain reaction, single strand conformation polymorphism analysis, and direct DNA sequencing. RESULTS—HNPCC represented 2.6% and suspected HNPCC 4.6% of all registered colorectal neoplasms. Eleven out of 18 HNPCC families (61%) showed microsatellite instability as opposed to four (of 18) suspected HNPCC (22%; p

Replication errors (RER) are frequently seen in both sporadic and hereditary forms of colorectal cancer. In hereditary nonpolyposis colorectal cancer (HNPCC), RER is associated with defects in DNA mismatch repair genes. Two of these genes, MSH2 and MLH1, account for a major share of this cancer syndrome. In order to assess the role of these genes in sporadic RER+ colorectal carcinoma, we have carried out a mutation analysis of MSH2 and MLH1 by two-dimensional (2-D) DNA electrophoresis, including heteroduplexing and separation in a denaturing gradient. All exons were amplified using multiplex PCR and were separated on the basis of both size and base pair composition under a single set of experimental conditions. Exons showing a spot position different from normal were sequenced. In screening 33 unselected, sporadic RER+ colorectal tumors, a germline mutation accompanied by loss of heterozygosity in tumor tissue was found in two patients. They were among the 4 patients out of the 33 screened that were diagnosed before the age of 50 years. In 8 of the remaining 31 tumors (26%), presence of somatic mutations (9 in total) could be demonstrated. While suggesting involvement of other genes in a substantial part of sporadic RER+ colorectal carcinomas, our results also demonstrate a clear role of MSH2 and MLH1 in these sporadic tumors and show that young sporadic RER+ colorectal carcinoma patients have a high probability of germline mutations. This has important implications for genetic testing and management of young colorectal cancer patients and their families. (C) 1997 Wiley-Liss, Inc.

Hereditary non-polyposis colorectal cancer (HNPCC) is known to be associated with several extracolonic cancers, e.g., cancers of the endometrium, stomach, urinary tract, small bowel and ovary. An association between HNPCC and brain tumours has also been reported, although previous risk analysis did not reveal an excess of this type of tumour. To determine whether HNPCC predisposes patients to brain tumours, we used risk analysis to compare families with HNPCC to those in the general population. Of the 1,321 subjects from 50 HNPCC families (with 60,237 person-years of follow-up) in the Dutch HNPCC Registry which satisfy the Amsterdam Criteria, 312 had colorectal cancer. The registry revealed 14 brain tumours in the HNPCC-patients and their first-degree relatives: 5 astrocytomas, 3 oligodendrogliomas, 1 ependymoma and 5 tumours for which a pathological report was not available. The relative risk of brain tumour in patients with HNPCC and their first-degree relatives was 6 times greater than in the general population (95% confidence interval, 3.5 to 10.1). After exclusion of the cases based only on family history, the relative risk was 4.3 (95% confidence interval, 2.3 to 8.0). Although the relative risk of brain tumour was increased, the lifetime risk was low (3.35%). Because it is not certain whether an improvement of the overall prognosis can be achieved by early diagnosis and intervention, and in view of the low lifetime risk, we do not recommend screening for brain tumours in HNPCC families. (C) 1996 Wiley-Liss, Inc.

The story of the molecular genetics of HNPCC is one of astonishingly rapid achievements. In just 16 months, from May 1993 to September 1994, four different genes, namely hMSH2, hMLH1, hPMS1 and hPMS2 have been identified and demonstrated to be associated with the disease. Their cloning was facilitated by the finding that tumor cells in HNPCC patients display a hypermutability of DNA short tandem repeats (microsatellite instability). In fact, HNPCC associated genes are the human counterparts of genetic elements known to control the fidelity of DNA replication in lower organisms. So far, more than 50 germline mutations of hMSH2 and hMLH1 genes have been reported in HNPCC kindreds. In addition, somatic mutations have been documented in hereditary as well as sporadic cancers. Unfortunately, the molecular diagnosis of HNPCC is hampered by the lack of mutational “hot spots” and of clearly defined genotype-phenotype correlations and different screening methods are to be employed for the analysis of affected and at-risk individuals.