Hereditary Nonpolyposis Colorectal Cancer Gene Research Articles

Genetic counseling for hereditary cancer

This paper provides an overview of the current approach to genetic counseling for cancer, using hereditary nonpolyposis colorectal cancer (HNPCC) as a prototype. Heretofore, when evaluating the possibility of an HNPCC diagnosis, physicians had to rely exclusively on a detailed family history of cancer in the context of an extended pedigree. Patients in the direct genetic lineage who had one or more first-degree relatives with an HNPCC syndrome cancer were told that they had a 50% likelihood of inheriting the deleterious gene. However, with the discovery of the HNPCC genes (hMSH2, hMLH1, hPMS1, hPMS2), genetic counseling can now provide a more precise determination of a patient's lifetime cancer destiny. Since these DNA findings are new, guidelines for sharing this information with patients remain preliminary. One must be certain that the patient wants to receive DNA information and that he or she is aware of potential discrimination by insurance companies and employers, as well as the possibility of psychological sequelae.

Frequency of mutations in mismatch repair genes in a population-based study of women with ovarian cancer

Background:Mutations in genes for hereditary non-polyposis colorectal cancer (HNPCC) in ovarian cancer patients remains poorly defined. We sought to estimate the frequency and characteristics of HNPCC gene mutations in a population-based sample of women with epithelial ovarian cancer.Methods:The analysis included 1893 women with epithelial ovarian cancer ascertained from three population-based studies. Full-germline DNA sequencing of the coding regions was performed on three HNPCC genes, MLH1, MSH2 and MSH6. Collection of demographic, clinical and family history information was attempted in all women.Results:Nine clearly pathogenic mutations were identified, including five in MSH6, two each in MLH1 and MSH2. In addition, 28 unique predicted pathogenic missense variants were identified in 55 patients. Pathogenic mutation carriers had an earlier mean age at diagnosis of ovarian cancer, overrepresentation of cancers with non-serous histologies and a higher number of relatives with HNPCC-related cancers.Conclusions:Our findings suggest that fewer than 1% of women with ovarian cancer harbour a germline mutation in the HNPCC genes, with overrepresentation of MSH6 mutations. This represents a lower-range estimate due to the large number of predicted pathogenic variants in which pathogenicity could not definitively be determined. Identification of mismatch repair gene mutations has the potential to impact screening and treatment decisions in these women.

Polypoid adenocarcinoma in the efferent jejunal loop after total gastrectomy in a Muir–Torre syndrome patient

Dear Editor: Once no loss of expression and no germline mutations of genes MLH1, MSH2, MSH6, and PMS2 were found, additional molecular analysis were done. Extensive deletions and insertions were also ruled out, but a compound biallelic MYH germline mutation (Y165C) was found. Moreover, a subcutaneous lesion in the forehead was removed and diagnosed of sebaceous adenoma. In summary, along a 15-year period, our patient developed one gastric adenocarcinoma, three colonic adenocarcinomas as well as several tubulo-villous adenomas, one small bowel adenocarcinoma, and one sebaceous adenoma. This clinical picture has led us up to the diagnosis of Muir–Torre syndrome (MTS). MTS is characterized by the association of sebaceous gland neoplasms or keratoacanthomas with visceral malignant diseases, most frequently colorectal carcinomas but also endometrial and urological neoplasms. Other neoplasms such as upper gastrointestinal carcinomas are also found but they develop more rarely. MTS is considered a clinical variant of hereditary non-polyposis colorectal cancer (HNPCC), and up to two thirds of MTS patients present germline mutations in HNPCC genes, predominantly in theMSH2 gene. In addition, other genetic alterations such as MYH germline mutations have also been described. The report of a polypoid small bowel adenocarcinoma arising in the efferent with jejunal loop, after a total gastrectomy performed 15 years before is exceptional. Just one case of synchronous jejunal carcinoma has been reported in a patient with an MYH-associated polyposis (MAP) syndrome. The full clinical spectrum of the recently described MAP syndrome is variable and yet to be elucidated. It often appears clinically similar to attenuated familial adenomatous polyposis (FAP), but some individuals may show a phenotype that overlaps from FAP to HNPCC syndrome, as it is shown in our patient. Small bowel carcinomas in MTS patients have been very rarely reported to date, most of them located at the duodenum. Whether it is beneficial or not to screen these patients for small bowel neoplasias is still unknown. The risk of small bowel cancer in HNPCC patients is estimated to be around 4%, and the localization is almost similar in the duodenum and the jejunum, but less frequent in the ileum. However, screening for small bowel cancer in HNPCC patients has not been included yet in the guidelines for surveillance, partly due to the fact that the possibility to explore the small bowel was limited until recently. Up to 25% of patients with MAP syndrome may present duodenal adenomatous polyposis and have shown to have a high relative risk of duodenal cancer, but the incidence of small bowel cancer is unknown in these patients. In the HNPCC and the MTS patients, the behavior of the visceral malignant diseases seems to be less aggressive and these patients tend to survive longer than their sporadic counterparts, so the prognosis might be improved by an early diagnosis. Then, a screening by a noninvasive procedure such as video capsule endoscopy may be advisable, although further studies are needed to show the real incidence of small bowel lesions in these patients. J. Ruiz-Tovar : J. Lacueva : I. Oliver :A. Martinez-Blasco : R. Calpena Department of General and Digestive Surgery, General University Hospital Elche, Alicante, Spain

S1542: Magnetic Resonance Colonography for Colorectal Cancer Screening in Hereditary Non-Polyposis Colorectal Cancer Gene Mutation Carriers

S1542: Magnetic Resonance Colonography for Colorectal Cancer Screening in Hereditary Non-Polyposis Colorectal Cancer Gene Mutation Carriers

Hereditary Nonpolyposis Colorectal Cancer (HNPCC): A Pilot Study Assessing Understanding and Attitudes Towards Prenatal Testing

Purpose: Hereditary Nonpolyposis Colorectal Cancer Syndrome (HNPCC) is the most common hereditary cancer syndrome accounting for 2-3% of colorectal cancer (CRC). Patients with HNPCC gene mutations have a 70-80% chance of developing CRC. Little is known about the attitudes of individuals with HNPCC towards prenatal diagnosis. We conducted a pilot study to evaluate HNPCC patients' understanding of their disease and assess their attitudes towards various modalities of prenatal testing. Methods: 12 individuals with HNPCC were educated on the currently available options for prenatal diagnosis of HNPCC including amniocentesis, chorionic villous sampling (CVS), and preimplantation genetic diagnosis (PGD). They were then given a 40-item survey on personal and family history related to HNPCC, demographics, and attitudes toward prenatal testing of their offspring. Results: Nine women and 3 men participated. Mean age at diagnosis was 42.8 years. 83% were Caucasian and 8% African American. 83% were married. 67% had children none of which were yet tested for HNPCC. 83% of the subjects knew there was a 50% risk of their offspring being affected with HNPCC. None were aware of prenatal testing options for HNPCC prior to the study. 100% were of the opinion that prenatal testing options should be discussed and offered to all with a HNPCC gene mutation. 58% would consider undergoing prenatal testing. Of these 100% would consider amniocentesis or PGD and 86% would consider CVS. More subjects were aware of amniocentesis (83%) than PGD or CVS (50%, 25% respectively). 83% felt that all modalities were ethically sound. 50% of the subjects felt that learning the fetus was unaffected with HNPCC was the greatest advantage of PGD. The possibility of complications (58%), or concerns regarding procedure success (33%), seemed to be the greatest disadvantage. 25% of the subjects felt that a HNPCC diagnosis influenced their reproductive decisions. The most important reason against prenatal testing was the difficulty in subsequent decisions making regarding termination. Religious or personal beliefs played little role in decision-making. Conclusion: The majority of HNPCC affected patients surveyed were aware of the autosomal dominant inheritance pattern of HNPCC. All patients felt prenatal testing options should be offered routinely. Though all patients in this study had seen genetic counselors in the past, none were aware of prenatal testing options for their disease prior to this study. This pilot study demonstrates the importance of addressing prenatal testing options in HNPCC patients. Future studies should be conducted to assess if prenatal counseling referral should be required as standard of care in all patients diagnosed with HNPCC.

Investigation on the role of nsSNPs in HNPCC genes – a bioinformatics approach

BackgroundA central focus of cancer genetics is the study of mutations that are causally implicated in tumorigenesis. The identification of such causal mutations not only provides insight into cancer biology but also presents anticancer therapeutic targets and diagnostic markers. Missense mutations are nucleotide substitutions that change an amino acid in a protein, the deleterious effects of these mutations are commonly attributed to their impact on primary amino acid sequence and protein structure.MethodsThe method to identify functional SNPs from a pool, containing both functional and neutral SNPs is challenging by experimental protocols. To explore possible relationships between genetic mutation and phenotypic variation, we employed different bioinformatics algorithms like Sorting Intolerant from Tolerant (SIFT), Polymorphism Phenotyping (PolyPhen), and PupaSuite to predict the impact of these amino acid substitutions on protein activity of mismatch repair (MMR) genes causing hereditary nonpolyposis colorectal cancer (HNPCC).ResultsSIFT classified 22 of 125 variants (18%) as 'Intolerant." PolyPhen classified 40 of 125 amino acid substitutions (32%) as "Probably or possibly damaging". The PupaSuite predicted the phenotypic effect of SNPs on the structure and function of the affected protein. Based on the PolyPhen scores and availability of three-dimensional structures, structure analysis was carried out with the major mutations that occurred in the native protein coded by MSH2 and MSH6 genes. The amino acid residues in the native and mutant model protein were further analyzed for solvent accessibility and secondary structure to check the stability of the proteins.ConclusionBased on this approach, we have shown that four nsSNPs, which were predicted to have functional consequences (MSH2-Y43C, MSH6-Y538S, MSH6-S580L, and MSH6-K854M), were already found to be associated with cancer risk. Our study demonstrates the presence of other deleterious mutations and also endorses with in vivo experimental studies.

Report on de-novo mutation in the MSH2 gene as a rare event in hereditary nonpolyposis colorectal cancer

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant predisposition for early-onset colorectal cancer and associated tumour types caused by mutations in DNA mismatch repair genes, mainly MLH1 and MSH2. The Amsterdam criteria, stressing familial tumour events, as well as the less stringent Bethesda criteria, help to raise suspicion of HNPCC. Mutation screening in a colon cancer patient of young age but negative family history revealed the MSH2 splice site mutation c.2006-2A>G. This mutation was present in all three germ cell layers in the patient, but absent in her biological parents, reporting the second case of de-novo germline mutation in MSH2. Our findings suggest that at least in approximately 1% of mutation-positive cases, a de-novo event might be involved. The identification of a newly evolved rare mutation calls for alertness and encourages the application of the Bethesda guidelines and certain clinical and histopathological features to define candidates for HNPCC gene mutation screening despite a negative family history.

A Prospective, Multicenter, Population-Based Study of BRAF Mutational Analysis for Lynch Syndrome Screening

Mismatch repair (MMR) deficiencies are the hallmark of tumors arising in Lynch syndrome, however, in approximately 15% of sporadic colorectal cancers (CRC) these deficiencies most often are associated with somatic methylation of the MMR gene MLH1. Recently, an oncogenic mutation in the BRAF gene has been involved in sporadic CRC showing MMR deficiencies as a result of MLH1 promoter methylation. The aim of this study was to evaluate the contribution of BRAF V600E mutation analysis in the identification of MSH2/MLH1 gene mutation carriers in newly diagnosed CRC patients. BRAF V600E mutation was analyzed in CRC patients with MMR deficiencies (microsatellite instability and/or lack of MLH1/MSH2 protein expression) in the EPICOLON population-based study. The effectiveness and efficiency of different strategies were evaluated with respect to the presence of MSH2/MLH1 germline mutations. MMR deficiencies were detected in 119 of the 1222 CRC patients with tumors showing either microsatellite instability (n = 111) or loss of protein expression (n = 81). BRAF mutation was detected in 22 (18.5%) of the patients. None of the patients with unambiguous germline mutation had BRAF mutation. Regardless of the strategy used to identify MSH2/MLH1 gene carriers, the introduction of BRAF analysis in these patients slightly improves their effectiveness. The introduction of BRAF mutation analysis as a step before germline genetic testing in patients with MMR deficiencies achieved a significant reduction in costs per mutation detected. Detection of BRAF V600E mutation could simplify and improve the cost effectiveness of genetic testing for hereditary nonpolyposis colorectal cancer, especially in patients whose family history is incomplete or unknown.

From Cancer Families to HNPCC: Henry Lynch and the Transformations of Hereditary Cancer, 1975-1999

Hereditary non-polyposis colorectal cancer (HNPCC) helps us understand how medical genetics has changed over the last forty years. The concept of the "cancer family" emerged from the realization that members of some families developed cancer more frequently than members of others, which led to a series of strategies by clinicians in the 1960s to persuade others of this. By the early 1990s molecular genetics had transformed the disease, from one that a few physicians believed ran in families, to one with precise genetic components that researchers generally accepted, and that could be detected through genetic tests. Nevertheless, a diagnosis of HNPCC still requires that the mutated genes be found within a kin group that is generally accepted as a cancer family. Moreover, the "cancer family" construct was crucial in the search for the HNPCC genes. HNPCC's trajectory can be mapped onto important debates about the complex relations between clinical and molecular genetics knowledge and practice.

No evidence for dual role of loss of heterozygosity in hereditary non-polyposis colorectal cancer

Hereditary non-polyposis colorectal cancer (HNPCC) is caused by germline mutations in mismatch repair (MMR) genes, mostly MLH1 and MSH2. Somatic inactivation of the wild-type allele of the respective MMR gene is required for tumor development. Unexpectedly, a recent study utilizing DNA from paraffin-embedded tissue material detected frequent loss of the mutant MMR gene allele in HNPCC tumors. Dual role for loss of heterozygosity (LOH) was proposed. If somatic loss of the wild-type MMR gene allele had occurred through point mutation or promoter hypermethylation, frequent somatic deletions at the region of the MMR gene locus, perhaps targeting other relevant cancer genes, could quite commonly lead to loss of the mutant allele. To test this hypothesis, we studied a population-based series of 25 fresh-frozen HNPCC tumors with a germline mutation in MLH1 or MSH2 for LOH. Fourteen of the 25 tumors (56%) showed LOH at the respective locus, and all 14 losses targeted the wild-type allele (P=0.00006). These results strongly support the traditional two-hit model of HNPCC gene inactivation.

Better Identification of HNPCC Gene Carriers

The Amsterdam and Bethesda criteria are often used to identify patients with hereditary nonpolyposis colorectal cancer (HNPCC), which is caused by a

Surveillance Colonoscopy in Individuals at Risk for Hereditary Nonpolyposis Colorectal Cancer: An Evidence-Based Review

Surveillance colonoscopy plays an important role in the management of asymptomatic patients known to carry and suspected of carrying hereditary nonpolyposis colorectal cancer gene mutations. Although the shortest interval between surveillance examinations may seem to offer the most benefit to patients, excessive use of this procedure may have unwanted consequences. This study was designed to evaluate the evidence and make recommendations regarding the optimal frequency of surveillance colonoscopy and the age at which to initiate surveillance based on the best available evidence. MEDLINE was searched for all articles assessing surveillance colonoscopy from 1966 to 2004 by using the MESH terms "hereditary nonpolyposis colorectal cancer" and "screening." The evidence was systematically reviewed and a critical appraisal of the evidence was performed. There are no randomized, controlled, clinical trials examining the frequency of surveillance colonoscopy in hereditary nonpolyposis colorectal cancer. Three cohort studies were identified for review. There is one cohort study of good quality that provides evidence that surveillance colonoscopy every three years in patients with hereditary nonpolyposis colorectal cancer reduces the risk of developing colorectal cancer and the risk of death. The two remaining cohort studies provide poor evidence on which to make a recommendation. The best available evidence supports surveillance with complete colonoscopy to the cecum every three years in patients with hereditary nonpolyposis colorectal cancer (B recommendation). There is no evidence to support or refute more frequent screening. Further research is required to examine the potential harms and benefits of more frequent screening. However, given the potential for rapid progression from adenoma to carcinoma and missing lesions at colonoscopy, there is consensus that screening more frequently than every three years is required.

Long Term Follow-up of HNPCC Gene Mutation Carriers: Compliance with Screening and Satisfaction with Counseling and Screening Procedures

Hereditary non polyposis colorectal cancer (HNPCC) is a hereditary predisposition to colorectal and endometrial cancer, caused by mutations of the mismatch repair (MMR) genes MSH2, MLH1 and MSH6. Regular colonoscopy reduces the incidence of colorectal cancer in mutation carriers dramatically. The aim of this study was to evaluate the use of colonoscopy by proven HNPCC mutation carriers. We also evaluated the satisfaction with the counseling and screening procedures at the long term. A questionnaire survey was performed among 94 proven MMR gene mutation carriers. Data were analyzed using univariate and multivariate analysis. The average time of follow-up was 3,5 years (range 0.5-8.5 years). The response rate was 74%. The proportion of unaffected mutation carriers under colonoscopic screening increased from 31 to 88% upon genetic testing, and for gynecological screening from 17 to 69%. However, more than half of the responders experienced colonoscopy as unpleasant or painful. About 97% felt well informed during counseling, and 88% felt sufficiently supported. Ten percent of the responders reported a high cancer worry that was significantly (P = 0.007) associated with a high perceived cancer risk. Six responders (9%) regretted being tested. Remarkably, of 4 of these 6 a close relative died recently of cancer. Problems with obtaining a disability or life insurance or mortgage were experienced by 4 out 10 healthy carriers opting for these services. In conclusion, genetic testing for HNPCC considerably improves compliance for screening, which will result in a reduction of HNPCC-related cancer morbidity and mortality in mutation carriers. Most HNPCC gene mutation carriers cope well with their cancer susceptibility on the long term.

Colorectal cancer at a young age

Colorectal cancer at a young age

Hereditary breast/ovarian and colorectal cancer genetics knowledge in a national sample of US physicians

Background: Clinically relevant genetics knowledge is essential for appropriate assessment and management of inherited cancer risk, and for effective communication with patients. This national physician survey assessed knowledge regarding basic...

Genetic testing for hereditary nonpolyposis colorectal cancer

Colorectal cancer remains a major cause of morbidity and mortality in United States. While most newly diagnosed cases are sporadic, a small percent of colorectal cancers are due to hereditary cancer syndromes, of which hereditary nonpolyposis colorectal cancer (HNPCC) is the most common. HNPCC is caused by mutations resulting in defective DNA mismatch repair gene function. Advances in molecular technology have enabled us to use genetic testing for HNPCC genes to identify high-risk families. Over the past several years, genetic testing for HNPCC has evolved from a research endeavor to a clinical test that often is an integral part of providing care for high-risk families. This article reviews the available genetic tests, genetic testing recommendations, interpretation of test results, and the clinical impact of genetic testing for HNPCC.

HNPCC mutations in the human DNA mismatch repair gene hMLH1 influence assembly of hMutLalpha and hMLH1-hEXO1 complexes.

Hereditary nonpolyposis colorectal cancer (HNPCC) is a common inherited form of neoplasia caused by germline mutations in DNA mismatch repair (MMR) genes. MMR proteins have been reported to associate with several proteins, including the human exonuclease 1 (hEXO1). We report here novel HNPCC-hMLH1 mutant proteins (T117M, Q426X and 1813insA) in Danish HNPCC patients. We demonstrate that these mutant HNPCC-hMLH1 proteins are unable to form complexes with hEXO1 and hPMS2 in vivo. The results indicate that mutations found in HNPCC gene carriers disrupt hMLH1-hEXO1 complex formation and hMutLalpha heterodimer assembly essential for MMR activity.

Efficient detection of hereditary nonpolyposis colorectal cancer gene carriers by screening for tumor microsatellite instability before germline genetic testing

The optimal strategy for the detection of hereditary nonpolyposis colorectal cancer (HNPCC) gene carriers remains uncertain. We evaluated whether microsatellite instability (MSI) analysis or MSH2 and MLH1 protein immunostaining of tumors will screen individuals efficiently for germline MSH2 and MLH1 testing. We performed a case-series study of 114 eligible families enrolled in our high-risk colorectal cancer (CRC) registry. Medical history data were collected on probands and relatives. MSI analysis was performed on proband tumors, and MSH2 and MLH1 protein immunostaining was assessed. Denaturing gradient gel electrophoresis was used to identify germline MSH2 or MLH1 mutations in probands found to have tumors with high-frequency MSI. Tumor tissue and adequate clinical data were available in 109 of the 114 families. Amsterdam criteria and Bethesda guidelines were met by 23% and 70% of the families, respectively. High-frequency MSI was identified in the proband tumors in 47 of the 109 families (43%). Germline MSH2 and MLH1 gene testing was carried out in the probands of 32 of 47 families with MSI-H tumors. Mutations were detected in 16 families (9 in MSH2 and 7 in MLH1) and sequence variants of uncertain significance in 5 families (1 in MSH2 and 4 in MLH1). Germline mutations or sequence variants of uncertain significance were detected in 15 of 19 (79%) of our Amsterdam families and in 6 of 13 (46%) of our non-Amsterdam families with MSI-H tumors. MSH2 and MLH1 protein immunostaining was assessed in 38 of the 47 MSI-H tumors. Unequivocal loss of hMLH1 expression was found in 20 tumors and loss of MSH2 expression in 9 tumors. Corresponding loss of protein expression was seen in 17 of 18 (94%) of tumors from probands with germline mutations or variants. The detection of high-frequency MSI or the loss of MSH2 or MLH1 immunostaining in CRCs are both useful criteria for selecting high-risk patients who should be tested for germline mutations in MSH2 or MLH1.

Prise en charge multi-disciplinaire du cancer colorectal héréditaire

The aim of this study was to assess the feasibility and success of multidisciplinary approach for the management of hereditary colorectal cancer. From November 1998 to November 2000, 32 individuals with putative familial/hereditary predisposition to colorectal cancer were investigated for adenomatous polyposis (attenuated or classical familial adenomatous polyposis coli, FAP) or for hereditary nonpolyposis colorectal cancer (HNPCC). Amsterdam criteria (I and II) and Bethesda guidelines were used to select putative HNPCC kindreds. Clinical data including endoscopy, pathological and operative reports as well as family history were collected. Pre- and post-test genetic counseling was offered to at-risk individuals. Genetic testing included microsatellite instability (MSI) and search for germline mutations in the APC, hMSH2 and hMLH1 genes. Immunohistochemistry (IHC) of hMSH2 and hMLH1 protein expression in tumour samples was also performed. 11 APC mutations were characterized, whereas four mutations in HNPCC genes were found in hMSH2 (2) and in hMLH1 (2). MSI and IHC correlated completely for cases with identified pathogenic mutation (100%). A thorough evaluation and management of hereditary colorectal requires a multidisciplinary approach. Thus, more mutation carriers can be identified and benefit from appropriate genetic counselling, while non-carrier individuals are relieved from unnecessary surveillance.

Germline and Somatic Mutation Analysis of MLH3 in MSI-Positive Colorectal Cancer

Microsatellite instability (MSI) is characteristic of hereditary nonpolyposis colorectal cancer, and occurs in a subset (10 to 15%) of unselected colorectal cancer cases. In hereditary nonpolyposis colorectal cancer, MSI is caused by defects in five mismatch repair genes, and in sporadic cases the main cause seems to be somatic MLH1 promoter methylation. Most likely additional hereditary nonpolyposis colorectal cancer genes remain to be discovered. Genes with simple repeats in their coding region are often targets for deletions in MSI-positive tumors. Several genes (TGFbeta RII, IGFIIR, MSH3, MSH6, BAX, MBD4) with significance in tumorigenesis harbor repeats in their coding regions and are often somatically inactivated because of deletions causing frameshifts. Recently, a novel human mismatch repair gene, MLH3, was cloned and shown to be involved in mammalian mismatch repair. To evaluate the possible role of MLH3 in hereditary cancer, we performed germline single-strand conformation polymorphism-analysis for 52 patients displaying features of inherited colorectal cancer. Forty-six of these had been diagnosed with MSI-positive tumors. No germline mutations were found. Similar to MSH3 and MSH6, MLH3 harbors mononucleotide repeats, ie, (A(6))-(A(9)), in its coding region, which makes it a putative target for somatic mutations in MSI-positive tumors. To evaluate its somatic inactivation we performed a deletion search focusing on eight exonic MLH3 mononucleotide repeats in a series of 93 MSI-positive tumors. Somatic deletions were found in 8.6% of the samples, a frequency similar to one detected in neutral noncoding mononucleotide repeats. No evidence of involvement of MLH3 in MSI tumorigenesis was obtained.