Frequency of hereditary non-polyposis colorectal cancer among unselected patients with colorectal cancer in Germany

INTRODUCTION

Hereditary non-polyposis colorectal cancer (HNPCC) is a major form of familial colorectal cancer (CRC). It is diagnosed when either the Amsterdam criteria (AC) are fulfilled or mutations in one of the mismatch repair (MMR) genes have been identified. This project aims at estimating the proportion of HNPCC among unselected patients with CRC.

PATIENTS AND METHODS

During a period of 2 years, a total of 351 non-selected patients with CRC were registered prospectively. 92 patients met the Bethesda criteria (9 of them fulfilled the AC) and 259 did not. 348 tumours were examined for microsatellite instability (MSI) and expression of MMR proteins.

RESULTS

MSI-H and MSI-L were identified in 17 and 6%, respectively. Loss of MSH2 or MLH1 was found in 1.5 and 8.8%, respectively. Based on the results of tumour tissue analyses, 80 patients with MSI and/or loss of MSH2 or MLH1 expression were identified as candidates for germline mutation screening. DNA of 40/80 patients was available. These patients were screened for MSH2 and MLH1 mutations; 19/40 patients with MSI and normal MSH2 or MLH1 expression were screened for mutations in MSH6. Three patients had relevant MMR gene mutations and six variants of unknown functional relevance were detected.

CONCLUSIONS

After adjusting for the cases not evaluable for germline mutations, 1.7% of the CRC patients had HNPCC proven by molecular genetics.

E-cadherin expression is homogeneously reduced in adenoma from patients with familial adenomatous polyposis: an immunohistochemical study of E-cadherin, beta-catenin and cyclooxygenase-2 expression

BACKGROUND AND AIMS

The adenomatous polyposis coli (APC) protein plays a crucial role in the regulation of beta-catenin, which is linked to the cell adhesion molecule E-cadherin. Furthermore, beta-catenin and cyclooxygenase-2 (COX-2) are both involved in the activation of nuclear transcription factors inducing cell proliferation. Germline mutations in the APC gene are the cause of familial adenomatous polyposis (FAP). To characterise the expression pattern of these proteins in FAP in comparison with sporadic adenomas, we studied 18 FAP-associated adenomas, 16 sporadic adenomas and seven normal colonic controls.

METHODS

E-cadherin, beta-catenin, COX-2 expression and the proliferative index (Ki67) were assessed by immunohistochemistry (index of expressing cells / total number of cells) in adenomatous mucosa, adjacent non-neoplastic tissue and normal colonic controls.

RESULTS

E-cadherin expression was significantly and homogeneously reduced in FAP adenomas (24%; 95%CI 16-32; sporadic adenomas 61%; 38-84; normal controls 98%; 96-100). Membraneous beta-catenin expression was significantly reduced in both FAP (30%; 11-49) and sporadic (42%; 19-65) adenomas (normal controls 96%; 88-104), whereas marked nuclear staining occurred in sporadic, but not in FAP adenomas. Stromal COX-2 expression and the proliferative index were increased only in sporadic adenomas (sporadic adenomas: COX-2 12%; 7-17, Ki67 24%; 15-33, FAP adenomas: COX-2 8%; 5-11, Ki67 5%; 2-9, normal controls: COX-2 4%; 2-7, Ki67 6%; 1-11).

CONCLUSION

Proteins involved in cell adhesion and cell proliferation, especially E-cadherin, are expressed differently in FAP and sporadic adenoma, pointing to possible differences in the molecular pathways to adenoma.

Can APC mutation analysis contribute to therapeutic decisions in familial adenomatous polyposis? Experience from 680 FAP families

BACKGROUND AND AIMS

In familial adenomatous polyposis (FAP), correlations between site of mutation in the adenomatous polyposis coli (APC) gene and severity of colonic polyposis or extracolonic manifestations are well known. While mutation analysis is important for predictive diagnosis in persons at risk, its relevance for clinical management of individual patients is open to question.

METHODS

We examined 680 unrelated FAP families for germline mutations in the APC gene. Clinical information was obtained from 1256 patients.

RESULTS

APC mutations were detected in 48% (327/680) of families. Age at diagnosis of FAP based on bowel symptoms and age at diagnosis of colorectal cancer in untreated patients were used as indicators of the severity of the natural course of the disease. A germline mutation was detected in 230 of 404 patients who were diagnosed after onset of bowel symptoms (rectal bleeding, abdominal pain, diarrhoea). When these patients were grouped according to the different sites of mutations, mean values for age at onset of disease differed significantly: patients carrying APC mutations at codon 1309 showed a disease onset 10 years earlier (mean age 20 years) compared with patients with mutations between codons 168 and 1580 (except codon 1309) (mean age 30 years), whereas patients with mutations at the 5' end of codon 168 or the 3' end of codon 1580 were diagnosed at a mean age of 52 years. Within each group of patients however large phenotypic variation was observed, even among patients with identical germline mutations. A higher incidence of desmoids was found in patients with mutations between codons 1445 and 1580 compared with mutations at other sites, while no correlation between site of mutation and presence of duodenal adenomas was observed.

CONCLUSIONS

As age at manifestation and course of the disease may be rather variable, even in carriers of identical germline mutations, therapeutic decisions should be based on colonoscopic findings in individual patients rather than on the site of mutation. However, in patients with mutations within codons 1445-1580, it may be advisable to postpone elective colectomy because desmoids may arise through surgical intervention.

DHPLC mutation analysis of the hereditary nonpolyposis colon cancer (HNPCC) genes hMLH1 and hMSH2

Denaturing high-performance liquid chromatography (DHPLC) is an efficient method for detection of mutations involving a single or few numbers of nucleotides, and it has been successfully used for mutation detection in disease-related genes. Colorectal cancer is one of the most common cancers, and mutations in the genes for hereditary nonpolyposis colon cancer (HNPCC), hMLH1 and hMSH2, also involve mainly point mutations. Sequence analysis is supposed to be a screening method with high sensitivity; however, it is time-consuming and expensive. We therefore decided to test sensitivity and reproducibility of DHPLC for 71 sequence variants in hMLH1 and hMSH2 initially found by sequence analysis in DNA samples of German HNPCC patients. DHPLC conditions of the PCR products were based on the melting pattern of the wild-type sequence of the corresponding PCR fragments. All but one of the 71 mutations was detected using DHPLC (sensitivity of 97%). Running time per sample averaged only 7 min, and the system is highly automated. Thus DHPLC is a rapid and sensitive method for the detection of hMLH1 and hMSH2 sequence variants.

[Hereditary carcinoma: pathogenesis and diagnosis]

Effective prevention of cancer in patients with a hereditary disposition to malignant tumours was made possible by intensive prevention programs and molecular diagnosis. Taken hereditary non-polyposis colorectal cancer (HNPCC) as an example this article deals with the pathogenesis and molecular diagnosis in hereditary dispositions to cancer. HNPCC is inherited in an autosomal-dominant fashion and caused by germline mutations in genes responsible for detection an removal of DNA-basepair-mismatches (DNA-mismatch-repair-genes). The error rate in DNA replication is reduced thousandfold by these genes. A defective DNA-mismatch-repair results in tumours if the increased mutation rate causes alterations of tumour-suppressor- or oncogenes. HNPCC patients develop colorectal cancer but also tumours of the renal pelvis, the ureter, the small bowel, the endometrium and less often in other organs. The clinical presentation of these tumours may be characteristic, the clinical diagnosis may be guided by different clinical criteria catalogues. The suspicion is proven by the identification of a germline mutation in DNA-mismatch-repair-genes. This laborious diagnostic procedure is often preceded by prescreening procedures as the detection of microsatellite instability or immunohistochemical tests. Once the germline mutation is identified in a affected family member, the first degree relatives may be tested for this mutation. If they have inherited the mutation, they harbour a extremely high risk for developing cancer and therefore may be included in prevention programs. This so called predictive testing must be preceded by genetic counseling.

Peutz-Jeghers syndrome: four novel inactivating germline mutations in the STK11 gene. Mutations in brief no. 227. Online

The diagnosis of Peutz-Jeghers syndrome is based on the occurrence of hamartomatous gastrointestinal polyps and perioral pigment spots. In view of the development of hamartomatous polyps in several syndromes and the variability of pigment spots in Peutz-Jeghers patients, identification of affected individuals is difficult. Recently, germline mutations in the STK11 gene have been reported as a molecular cause of Peutz-Jeghers syndrome. We present four novel inactivating mutations identified by direct sequencing of all 9 exons of the STK11 gene in 4 patients suggestive of Peutz-Jeghers syndrome: three frameshift mutations (125-137del; 474-480del; 516-517insT) and one nonsense mutation (Q220X). Our data obtained in these patients and in those reported previously emphasize the diagnostic value of histological discrimination between different types of hamartomatous polyps and of molecular analysis, particularly in cases with no family history of the disease.

Frequent 4-bp deletion in exon 9 of the SMAD4/MADH4 gene in familial juvenile polyposis patients

Familial juvenile polyposis (FJP) is a hamartomatous polyposis syndrome characterized by the appearance of juvenile polyps in the gastrointestinal tract. Patients with this syndrome are at an increased risk for cancer of the colon, stomach, and pancreas. Recently, germline mutations in the SMAD4/DPC4 gene (official symbol MADH4) have been found in the majority of patients suffering from FJP. We have examined 11 unrelated patients with FJP for MADH4 germline mutations by direct sequencing of genomic DNA encompassing all 11 exons of the gene. Besides a novel mutation (959-960delAC at codon 277, exon 6) in one patient, we observed a 4-bp deletion (1372-1375delACAG) in exon 9 in two unrelated patients. Examination with microsatellite markers flanking MADH4 supports an independent origin of the mutation in these two families. The same 4-bp deletion in exon 9 has previously been described in three out of nine patients examined for MADH4 mutations. Our results combined with these previous data demonstrate that a unique 4-bp deletion in exon 9 of MADH4 accounts for about 25% of all FJP cases and that other MADH4 mutations occur in an additional 15% of patients. Genes Chromosomes Cancer 25:403-406, 1999.

Peutz-Jeghers syndrome: four novel inactivating germline mutations in the STK11 gene. Mutations in brief no. 227. Online

The diagnosis of Peutz-Jeghers syndrome is based on the occurrence of hamartomatous gastrointestinal polyps and perioral pigment spots. In view of the development of hamartomatous polyps in several syndromes and the variability of pigment spots in Peutz-Jeghers patients, identification of affected individuals is difficult. Recently, germline mutations in the STK11 gene have been reported as a molecular cause of Peutz-Jeghers syndrome. We present four novel inactivating mutations identified by direct sequencing of all 9 exons of the STK11 gene in 4 patients suggestive of Peutz-Jeghers syndrome: three frameshift mutations (125-137del; 474-480del; 516-517insT) and one nonsense mutation (Q220X). Our data obtained in these patients and in those reported previously emphasize the diagnostic value of histological discrimination between different types of hamartomatous polyps and of molecular analysis, particularly in cases with no family history of the disease.

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.

Muir-Torre phenotype has a frequency of DNA mismatch-repair-gene mutations similar to that in hereditary nonpolyposis colorectal cancer families defined by the Amsterdam criteria

Muir-Torre syndrome (MTS) is an autosomal dominant disease defined by the coincidence of at least one sebaceous skin tumor and one internal malignancy. About half of MTS patients are affected by colorectal cancer. In a subgroup of MTS patients the disease has an underlying DNA mismatch-repair (MMR) defect and thus is allelic to hereditary nonpolyposis colorectal cancer (HNPCC). The purpose of this study was to examine to what extent germ-line mutations in DNA MMR genes are the underlying cause of the MTS phenotype. We ascertained 16 MTS patients with sebaceous skin tumors and colorectal cancer, and we examined their skin and visceral tumors for microsatellite instability. All the patients exhibited high genomic instability in at least one tumor. The search for germ-line mutations in the hMSH2 and hMLH1 genes in 13 of the MTS patients revealed truncating mutations in 9 (69%): eight mutations in the hMSH2 gene and one in the hMLH1 gene. This is the first systematic search for germ-line mutations in patients ascertained on the basis of sebaceous skin tumors. Our results indicate that (1) MTS patients exhibit significantly more mutations in the hMSH2 gene than in the hMLH1 gene; and (2) the subpopulation of MTS patients who are also affected by colorectal cancer, irrespective of family history and age at onset of tumors, may have a likelihood for an underlying DNA MMR defect similar to that for patients with a family history fulfilling the strict clinical criteria for HNPCC.