Bilateral versus unilateral botulinum toxin injections for chronic anal fissure: a randomised trial.

BACKGROUND: Botulinum toxin injected into the internal anal sphincter is used in the treatment of chronic anal fissure but there is no standardised technique for its administration. This randomised single centre trial compares bilateral (either side of fissure) to unilateral injection. METHODS: Participants were randomised to receive bilateral (50 + 50 units) or unilateral (100 units) Dysport® injections into the internal anal sphincter in an outpatient setting. Injection-related pain assessed by visual analogue scale was the primary outcome measure. Secondary outcomes were healing rate, fissure pain, incontinence, and global health scores. RESULTS: Between October 2008 and April 2012, 100 patients with chronic anal fissure were randomised to receive bilateral or unilateral injections. Injection-related pain was comparable in both groups. There was no difference in healing rate. Initially, there was greater improvement in fissure pain in the bilateral group but at 1 year the unilateral group showed greater improvement. Cleveland Clinic Incontinence score was lower in the unilateral group in the early post-treatment period and global health assessment (EuroQol EQ-VAS) was higher in the unilateral group at 1 year. CONCLUSIONS: Injection-related pain was similar in bilateral and unilateral injection groups. Unilateral injection was as effective as bilateral injections in healing and improving fissure pain without any deterioration in continence.

Early experience with laparoscopic extralevator abdominoperineal excision within an enhanced recovery setting: analysis of short-term outcomes and quality of life.

INTRODUCTION: Conventional abdominoperineal excision for low rectal cancer has a higher local recurrence and reduced survival compared to anterior resection. An extralevator abdominoperineal excision (ELAPE) may improve outcome through removal of increased tissue in the distal rectum. Experience with ELAPE is limited and no studies have reported on quality of life (QOL) following this procedure. We describe a minimally invasive approach to ELAPE within an enhanced recovery programme, and present short-term results and QOL analyses. METHODS: All laparoscopic ELAPEs were included in a prospective database. Demographics, intra-operative and post-operative outcomes were evaluated. Postoperative QOL was assessed using the European Organisation for Research and Treatment of Cancer (EORTC) questionnaires QLQ-C30 and QLQ-CR29. RESULTS: Thirteen laparoscopic ELAPEs were performed over a two-year period. All were enrolled in an enhanced recovery programme. The median age was 76. The median tumour height was 20 mm (range: 0-50 mm) from the dentate line and all patients received neoadjuvant treatment. The median duration of surgery was 300 minutes (range: 120-488 minutes), the mean blood loss was 150 ml and one procedure was converted to open surgery. There was no circumferential resection margin involvement or tumour perforation. The median duration of use of intravenous fluid, patient controlled analgesia and urinary catheterisation was 2, 2 and 2.5 days respectively and the median length of hospital stay was 7.5 days. Two patients developed perineal wound dehiscence. QOL analysis revealed high global health status (90.8), physical (91.3), emotional (98.3) and social functioning (100) scores, which compared favourably with EORTC reference values and published QOL scores following conventional abdominoperineal excision. CONCLUSIONS: Laparoscopic ELAPE within an enhanced recovery setting is a feasible and safe approach with acceptable short-term outcomes and post-operative quality of life.

An insight into the genetic pathway of adenocarcinoma of the small intestine.

BACKGROUND: Although the adenoma to carcinoma pathway in colorectal cancer is well described, the mechanisms of carcinogenesis in the small intestine remain unclear. AIMS: The aim of this study was to investigate candidate genes in the genetic pathway of adenocarcinoma of the small intestine. SUBJECTS AND METHODS: A total of 21 non-familial, non-ampullary adenocarcinomas of the small intestine were analysed. DNA was extracted from formalin fixed paraffin wax embedded tissue using standard techniques. The replication error (RER) status was determined by amplification of BAT26. The mutation cluster region (MCR) of the adenomatous polyposis coli (APC) gene was screened using polymerase chain reaction single strand conformational polymorphism and direct sequencing. Immunohistochemistry was performed on formalin fixed paraffin wax embedded tissue using monoclonal antibodies for hMLH1, hMSH2, beta-catenin, E-cadherin, and p53. RESULTS: Fourteen male and seven female patients with a median age of 64 years (range 21-85) presented with adenocarcinoma of the duodenum (10), jejunum (7), and ileum (4). One cancer (5%) was found to be RER+, and all tumours stained positive for hMLH1 and hMSH2. No mutations were detected in the MCR of the APC gene. beta-Catenin showed increased nuclear expression with loss of membranous staining in 10 cancers (48%). Absent or decreased membrane expression of E-cadherin was found in eight cancers (38%). Strong staining of p53 was found in the nucleus of five cancers (24%). CONCLUSION: We did not detect mutations in the MCR of the APC gene, and this suggests that adenocarcinoma of the small intestine may follow a different genetic pathway to colorectal cancer. Abnormal expression of E-cadherin and beta-catenin was common and reflects an early alternative to APC in this pathway in which mutations may be found in adenocarcinoma of the small intestine.

hMLH1 and hMSH2 mutations in families with familial clustering of gastric cancer and hereditary non-polyposis colorectal cancer.

The pattern of hMLHI and hMSH2 mutations was assessed to identify the genetic correlation between hereditary gastric and colorectal cancers. Four disease groups and their healthy family members were assembled according to the presentation of gastric cancer: FG, familial clustering of gastric cancer (n = 32); CG, family with one or more colorectal and gastric cancers in first-degree relatives (n = 22); HS, seven HNPCC families corresponding to the Amsterdam criteria (AMS+) and 12 suspected HNPCC families which did not satisfy one of the criteria (AMS-), but no gastric cancer among first- and second-degree relatives (n = 19); and SG, sporadic gastric cancer (n = 33). In the CG group, three were included in AMS + and six in AMS- criteria. Peripheral blood was obtained from them to detect hMLHI and hMLH2 mutations using PCR-SSCP analysis and direct sequencing. The incidence of mutations was 9.4% in the FG group, 54.5% in the CG group, 31.6% in the HS group, and none in the SG group. The incidence, type, and number of the mutation were not different between the CG and HS groups. Thirty-four different mutations included 19 in hMLH1 and 15 in hMSH2. Gastric cancer was the most common extracolonic malignancy in HNPCC and suspected HNPCC families (9/28, 32.1%). The hMLH1 or hMSH2 mutation occurred in seven of 10 families with AMS+, whereas it occurred in four of 18 with AMS- (70% vs. 22.2%, P = .013). Five mutations in the hMLH1 and six mutations in the hMSH2 were exclusively found in families with gastric cancer. All three mutations in the FG group were in hMLHI and there was no mutation in their healthy family members. This study demonstrates that some familial clustering type of gastric cancer appears to be associated with hMLHI mutations thereby indicating a difference from the hereditary gastric cancer studies previously reported. In addition, hMLHI and hMSH2 mutations may impact the gastric cancer carcinogenesis in HNPCC or suspected HNPCC.

The E-cadherin gene (CDH1) variants T340A and L599V in gastric and colorectal cancer patients in Korea.

INTRODUCTION: Germline mutations in E-cadherin (CDH1) have been reported in families with early onset, diffuse gastric cancer. More recently, mutations in CDH1 have been described in colorectal cancer cell lines. AIMS: We have investigated if germline mutations in CDH1 occur among different groups of Korean gastric and colorectal cancer patients, with and without a positive family history. METHODS: We studied 131 patients and 168 normal controls (88 Korean and 80 non-Korean). Patients were divided into five groups: group I, 20 gastric cancer patients with a family history; group II, 26 colorectal cancer patients with a family history of gastric cancer (those from familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC) kindred were excluded); group III, 16 HNPCC patients without identified germline mutations in hMLH1 and hMSH2; group IV, 35 gastric cancer patients without a family history; and group V, 34 colorectal cancer patients without a family history. Polymerase chain reaction, single strand conformational polymorphism analysis, direct sequencing, and genotyping for identified variants were performed. RESULTS: Several germline changes in CDH1 were found. In addition to previously described polymorphisms, we found three novel changes, two of which were missense changes (T340A and L599V). T340A was present in one patient in group III and one in group V. L599V was present in one patient in group II, in two in group III, and in one in group IV. T340A was not found in normal controls while L599V was present in two of 88 Korean controls. Patients with these variants may appear to have a tendency to early onset cancer with a positive family history, although differences in frequencies did not reach statistical significance. Genotyping results suggest that these variants might have a common origin, particularly T340A. CONCLUSION: We have described two new missense germline variants in CDH1 in various groups of Korean gastrointestinal cancer patients. Further work is required to assess if these variants increase the risk of gastrointestinal cancer.

Microsatellite instability in benign skin lesions in hereditary non-polyposis colorectal cancer syndrome.

The coexistence of cutaneous and extra-cutaneous malignancies within one family could be explained by shared genetic mechanisms such as common tumor suppressor gene mutations or oncogene activation, as well as mutations in DNA repair genes. Hereditary non-polyposis colorectal cancer syndrome (HNPCC) and its variant Muir-Torre syndrome (MTS) are caused by germline DNA mismatch repair gene mutations. Colonic and endometrial tumors from HNPCC patients exhibit microsatellite instability (MSI), as do sebaceous lesions in MTS. We recruited individuals from cancer prone families to determine if MSI is found in benign and malignant skin lesions and to assess whether MSI in the skin is predictive of genomic instability with susceptibility to tumors characteristic of HNPCC. One hundred and fifteen benign, dysplastic, and malignant skin lesions from 39 cancer prone families were analyzed. Thirteen benign skin lesions from three individuals belonging to two HNPCC pedigrees showed MSI. No mutations in hMSH2 and hMLH1 were found in two of the three individuals with RER + skin lesions. We found MSI in non-sebaceous non-dysplastic skin lesions in HNPCC pedigrees. MSI was not found in skin lesions within other family cancer syndromes. These results have important clinical implications as the detection of MSI in prevalent readily accessible skin lesions could form the basis of noninvasive screening for HNPCC families. It may also be a valuable tool in the search for new mismatch repair genes.

Somatic mutations of the first 14 exons of APC in hamartomatous polyps of the colon.

Although hamartomatous or hyperplastic polyps are rarely accompanied by adenomatous or carcinomatous foci, the role of APC (MIM# 175100) mutations in these polyps is not clear. The neoplastic potential of these polyps was assessed with regard to somatic mutation of the first 14 exons of APC. DNA from 14 hamartomatous polyps (12 patients with juvenile polyp, JP; two patients with Peutz-Jeghers syndrome, PJS) and 27 hyperplastic polyps was used. Exons 1-14 of APC were amplified using verified oligonucleotide primers, and PCR-SSCP analysis was performed. Translation-terminating mutation in exon 15 was also screened using the protein truncation test. All mutations found were transitions or transversions with heterozygous alleles of both wild-type and mutant APC in exons 2, 9, 10, and 11. Four hamartomatous polyps (three from JP and one from PJS) showed seven, new mutations and one common APC variant (codon 486), whereas no hyperplastic polyps demonstrated mutation. APC mutation was not correlated with previous history of colorectal carcinoma or number of polyps. Since all mutations were missense or silent mutations occurred in exons not previously known to have functionally relevant area, their phenotypic implication appeared to be limited.

Mechanisms of inactivation of mismatch repair genes in human colorectal cancer cell lines: the predominant role of hMLH1.

Fifteen to twenty-five percent of sporadic colorectal carcinomas are replication error (RER) positive. Because the frequency of mutations in the mismatch repair genes (hMLH1 and hMSH2) is low in these tumors, we have investigated the role of mutational inactivation, methylation of the promoter region, and loss of heterozygosity (LOH) as a possible explanation for the mutator phenotype of RER+ colorectal cancer cell lines. Genomic DNA was extracted from a panel of 49 human colorectal cancer cell lines. The RER status was determined by amplification of BAT-26. All exons of hMLH1 and hMSH2 were amplified with the PCR and screened by using single-strand conformational polymorphism and direct sequencing. The methylation status was ascertained by methylation-specific PCR after bisulfite modification of DNA. Western blotting for hMLH1 was performed on methylated cell lines before and after the addition of the demethylating agent 5-azacytidine. LOH was sought by GENESCAN analysis of amplified CA repeat markers and indirectly by determining the number of homozygotes in the cell lines and human random controls. Twelve cell lines from ten tumors (24%) were RER+. Hypermethylation of the hMLH1 promoter occurred in five of ten (50%) RER+ tumors, whereas three of thirty-two (6%) RER tumors showed partial methylation. None of the fully methylated cell lines expressed hMLH1, although all reexpressed hMLH1 after treatment with 5-azacytidine. There was no LOH in the RER+ tumors in either hMLH1 or hMSH2. Our results suggest that mutations of hMLH1 together with hypermethylation of the promoter region, but not LOH, are the cause of the mutator phenotype in the majority (70%) of RER+ tumors.

Suspected hereditary nonpolyposis colorectal cancer: International Collaborative Group on Hereditary Non-Polyposis Colorectal Cancer (ICG-HNPCC) criteria and results of genetic diagnosis.

PURPOSE: The aim of this study was to determine the frequency of mutations in the mismatch repair genes in families suspected of having hereditary nonpolyposis colorectal cancer. METHODS: We devised two criteria for families suspected of having hereditary nonpolyposis colorectal cancer (Criteria I and II). Criteria I consist of at least two first-degree relatives affected with colorectal cancer with at least one of the following: development of multiple colorectal tumors including adenomatous polyp, at least one colorectal cancer case diagnosed before the age of 50, and occurrence of a hereditary nonpolyposis colorectal cancer extracolonic cancer (endometrium, urinary tract, small intestine, stomach, hepatobiliary system, or ovary) in family members. Criteria II consist of one colorectal cancer patient with at least one of the following: early age of onset (<40 years); endometrial, urinary tract, or small intestine cancer in the index patient or a sibling (one aged <50 years); and two siblings with other integral hereditary nonpolyposis colorectal cancer extracolonic cancers (one aged <50 years). A questionnaire was mailed to members of the International Collaborative Group on Hereditary Non-Polyposis Colorectal Cancer to determine the mutation detection rate in mismatch repair genes from the families fulfilling these criteria. For comparison the mutation detection rate for families fulfilling the Amsterdam hereditary nonpolyposis colorectal cancer criteria in each institution was also obtained. RESULTS: Data were obtained from eight different institutions (in 7 different countries). In a total of 123 patients from 123 families (67 families fulfilling Criteria I and 56 families fulfilling Criteria II), genetic testing for germline mismatch repair gene variants was performed. Germline mutations of the hMLH1 or hMSH2 genes were identified in 24 families (20 percent). Of these, the mutation detection rate for families fulfilling Criteria I was 28 percent (19/67). The mutation detection rate for families fulfilling Criteria II was 9 percent (5/56). In these eight institutions, the overall mutation detection rate for families fulfilling the Amsterdam hereditary nonpolyposis colorectal cancer criteria was 50 percent (77/154). CONCLUSION: The Criteria I for suspected hereditary nonpolyposis colorectal cancer have the advantages that they can be applied to nuclear families and they can include extracolonic cancers. The results of this study suggest that families fulfilling Criteria I should be offered genetic testing. The relatively low mutation detection rate in those families fulfilling Criteria II suggests that, using current techniques, genetic testing in these families is not practical.

Mutated epithelial cadherin is associated with increased tumorigenicity and loss of adhesion and of responsiveness to the motogenic trefoil factor 2 in colon carcinoma cells.

Epithelial (E)-cadherin and its associated cytoplasmic proteins (alpha-, beta-, and gamma-catenins) are important mediators of epithelial cell-cell adhesion and intracellular signaling. Much evidence exists suggesting a tumor/invasion suppressor role for E-cadherin, and loss of expression, as well as mutations, has been described in a number of epithelial cancers. To investigate whether E-cadherin gene (CDH1) mutations occur in colorectal cancer, we screened 49 human colon carcinoma cell lines from 43 patients by single-strand conformation polymorphism (SSCP) analysis and direct sequencing. In addition to silent changes, polymorphisms, and intronic variants in a number of the cell lines, we detected frameshift single-base deletions in repeat regions of exon 3 (codons 120 and 126) causing premature truncations at codon 216 in four replication-error-positive (RER+) cell lines (LS174T, HCT116, GP2d, and GP5d) derived from 3 patients. In LS174T such a mutation inevitably contributes to its lack of E-cadherin protein expression and function. Transfection of full-length E-cadherin cDNA into LS174T cells enhanced intercellular adhesion, induced differentiation, retarded proliferation, inhibited tumorigenicity, and restored responsiveness to the migratory effects induced by the motogenic trefoil factor 2 (human spasmolytic polypeptide). These results indicate that, although inactivating E-cadherin mutations occur relatively infrequently in colorectal cancer cell lines overall (3/43 = 7%), they are more common in cells with an RER+ phenotype (3/10 = 30%) and may contribute to the dysfunction of the E-cadherin-catenin-mediated adhesion/signaling system commonly seen in these tumors. These results also indicate that normal E-cadherin-mediated cell adhesion can restore the ability of colonic tumor cells to respond to trefoil factor 2.

Detection of residual disease following breast-conserving surgery.

BACKGROUND: Assessment of completeness of tumour excision has become an integral part of breast-conserving surgery, but the accuracy of margin analysis has been questioned. This study compared the results of resection margin analysis with an examination of tumour bed biopsies and of the excised cavity wall. METHODS: One hundred and forty-four patients underwent breast-conserving surgery for T1-2 N0-1 breast cancer. Following wide local excision, four bed biopsies were taken from the cavity wall which was then completely excised. The presence of invasive and in situ disease at the inked resection margin (IRM) and in the adjacent bed biopsies and cavity wall was recorded. RESULTS: Positive margins and/or residual disease in either the bed biopsies or cavity wall was found in 62 (43 per cent) of 144 cases. Residual disease (invasive or in situ) was present at the IRM in 39 specimens (27 per cent) and was present in 25 bed biopsy (17 per cent) and 39 cavity wall (27 per cent) specimens. These comprised different but overlapping groups of patients. CONCLUSION: Margin analysis of wide local excision specimens is a poor predictor of completeness of excision. Routine resection and examination of the entire cavity wall increases the detection of residual disease compared with examination of bed biopsies alone and is a useful adjuvant to conventional margin evaluation.

The APC variants I1307K and E1317Q are associated with colorectal tumors, but not always with a family history.

Classical familial adenomatous polyposis (FAP) is a high-penetrance autosomal dominant disease that predisposes to hundreds or thousands of colorectal adenomas and carcinoma and that results from truncating mutations in the APC gene. A variant of FAP is attenuated adenomatous polyposis coli, which results from germ-line mutations in the 5' and 3' regions of the APC gene. Attenuated adenomatous polyposis coli patients have "multiple" colorectal adenomas (typically fewer than 100) without the florid phenotype of classical FAP. Another group of patients with multiple adenomas has no mutations in the APC gene, and their phenotype probably results from variation at a locus, or loci, elsewhere in the genome. Recently, however, a missense variant of APC (I1307K) was described that confers an increased risk of colorectal tumors, including multiple adenomas, in Ashkenazim. We have studied a set of 164 patients with multiple colorectal adenomas and/or carcinoma and analyzed codons 1263-1377 (exon 15G) of the APC gene for germ-line variants. Three patients with the I1307K allele were detected, each of Ashkenazi descent. Four patients had a germ-line E1317Q missense variant of APC that was not present in controls; one of these individuals had an unusually large number of metaplastic polyps of the colorectum. There is increasing evidence that there exist germ-line variants of the APC gene that predispose to the development of multiple colorectal adenomas and carcinoma, but without the florid phenotype of classical FAP, and possibly with importance for colorectal cancer risk in the general population.

Frequency of germline hereditary non-polyposis colorectal cancer gene mutations in patients with multiple or early onset colorectal adenomas.

BACKGROUND: The hereditary non-polyposis colorectal cancer (HNPCC) syndrome is caused by germline mutations in mismatch repair genes and predisposes individuals to cancers of the colon and other specific sites. On theoretical grounds, it is expected that patients with HNPCC also develop more colorectal adenomas than the general population. In essence, if the mutation rate is raised owing to mutations at a mismatch repair locus, more mutations are expected at loci such as APC (adenomatous polyposis coli) and more adenomas will start to grow. Not all data support this expectation, however. AIM: To search for germline mutations at HNPCC loci in patients with multiple adenomas. SUBJECTS: Twenty five patients (without known APC mutations) who have developed colorectal adenomas in unusually large numbers and, in some cases, at an early age. METHODS: Germline APC mutations were excluded using the protein truction test for exon 15 and mismatch chemical cleavage analysis for remaining exons. Germline HNPCC mutations were detected by using PCR and single strand conformation polymorphism analysis. RESULTS: Just one germline HNPCC mutation was found (4% of cases) and this was of uncertain functional effect. CONCLUSIONS: In general, germline HNPCC mutations are not responsible for the phenotype of patients with multiple colonic adenomas. It is possible that patients with HNPCC tend to develop adenomas more frequently and earlier than the general population, but that this effect is relatively subtle. These results suggest that individuals with colorectal adenomas only should not strictly be classified as "affected" in HNPCC families (although they should certainly not be classified as "unaffected" either and may warrant intensive screening). In the absence of a personal or strong family history of colorectal cancer, it is probably not worthwhile performing diagnostic or predictive genetic testing for HNPCC mutations in subjects with colorectal adenomas. Although undetected APC mutations may be responsible for some of the phenotypes in this sample, as yet uncharacterised adenoma predisposing genes probably exist.

Genetic testing is important in families with a history suggestive of hereditary non-polyposis colorectal cancer even if the Amsterdam criteria are not fulfilled.

BACKGROUND: Clinical screening is still the first-line approach to identification of families with hereditary non-polyposis colorectal cancer (HNPCC). The need for uniformity of diagnosis of the syndrome, particularly in multicentre studies, led to the establishment of a set of minimum diagnostic criteria, the 'Amsterdam criteria'. It is now known that HNPCC is caused by germline defects in the human mismatch repair genes and DNA predictive testing is possible. Defects in two of the known mismatch repair genes, namely hMSH2 and hMLH1, account for over 90 per cent of mutations found in HNPCC families. METHODS: Ten families were identified with pedigrees suggestive of HNPCC (that is with a possible dominant inheritance of HNPCC), but in which the Amsterdam criteria were not fulfilled. Using the technique of single-strand conformational polymorphism analysis, samples were screened from an affected member of each of these ten kindreds for germline mutations in the genes hMSH2 and hMLH1. RESULTS: Mutations were identified in six families. Of these, there were three missense, one nonsense, one frameshift and one putative splice-site mutation. Three of the mutations were in hMSH2 and three in hMLH1. CONCLUSION: This study demonstrates that all families with a pedigree suggestive of HNPCC should be referred to a geneticist even if the Amsterdam criteria are not fulfilled. A knowledge of the gene carrier status enables targeted surveillance and the possibility of early surgical intervention that could be curative.

Use of SSCP analysis to identify germline mutations in HNPCC families fulfilling the Amsterdam criteria.

Hereditary non-polyposis colorectal cancer (HNPCC) is a clinical syndrome characterised by an inherited predisposition to early onset colorectal and uterine cancers and an increased incidence of other cancers. It is caused by germline defects in the human mismatch repair genes. Defects in two of the known mismatch repair genes (namely hMSH2 and hMLH1) account for over 90% of mutations found in HNPCC families. In this study we have identified 14 families that fulfilled the clinical criteria for HNPCC and screened the hMSH2 and hMLH1 genes for germline mutations using single-strand conformational polymorphism (SSCP) analysis and DNA sequencing. Seven mutations were identified. Of these, there were five frameshifts, one missense mutation and a further novel mutation that involved separate transition and transversion changes in successive amino acid residues. Three of the mutations were in hMSH2 and four in hMLH1. The identification of germ-line mutations in an HNPCC family enables targeted surveillance and the possibility of early curative intervention. SSCP is a simple and effective method for identifying most mutations in the human mismatch repair genes using DNA from fresh, frozen or archival material.

Germline HNPCC gene variants have little influence on the risk for sporadic colorectal cancer.

Hereditary non-polyposis colorectal cancer (HNPCC) is a syndrome of inherited bowel and other cancers that has been said to account for up to 15% of all colorectal carcinomas (CRCs). HNPCC can now be diagnosed at the molecular level by detecting germline mutations in genes involved in mismatch repair. A current problem is to determine the prevalence of HNPCC mutations in colon cancer patients with limited or no family history, especially in cases of early onset. We have identified 50 cases of non-polyposis colorectal cancer without a family history of CRC or any other HNPCC cancer, who presented under the age of 45 years. Germline HNPCC variants (at the hMSH2 or hMLH1 loci) were detected in a small minority of cases (6%). The variants that we have found may be new or low penetrance mutations, or even polymorphisms. It remains possible that some of our sample have an inherited predisposition to CRC that is not caused by HNPCC mutations or by known polyposis syndromes. Our data suggest that most HNPCC mutations occur in families and have high or moderate penetrance. New or low penetrance HNPCC mutations probably do not contribute significantly to the risk of colorectal cancer in the general population and probably account for much fewer than 15% of all CRCs. Our results question whether mass population genetic screening programmes are worthwhile for diseases such as HNPCC using current technology.

Clinical features and molecular analysis of a family with multiple colon tumours and reduced plasminogen activator activity.

A family is reported in which a pair of brothers has developed recurrent venous thromboses, which have been shown in one brother (the proband) to result from a reduced level of tissue plasminogen activator (t-PA) activity. Both brothers have also developed multiple synchronous and metachronous colorectal adenomas. Other pedigree members have developed colon cancers, but not multiple colonic tumours. We have shown that HNPCC and FAP/AAPC are unlikely causes of the family's phenotypes. Previous studies have found low levels of t-PA in sporadic colon tumours. In this family, mutations in the t-PA gene, at a linked locus, or at a locus controlling t-PA activity/release may modify the colon tumour phenotype to cause multiple lesions.

Allele loss on chromosome 11q and microsatellite instability in malignant melanoma.

Loss of heterozygosity (allele loss, LOH) occurs frequently on the long arm of chromosome 11 in several types of cancer. We analysed 32 melanomas (almost all metastatic lesions) for allele loss at eight loci along the length of chromosome 11 (ptel-D11S922-D11S899-D11S1324-D11S1313-++ +D11S901-NCAM-D11S29-D11S968-qtel). The highest frequency of loss (38%) was at D11S29 (11q23.3). Of 13 melanomas which had lost an allele at one or more loci, all but one showed LOH at either D11S29 or NCAM (11q22). The region between these two loci is the most likely location of any tumour suppressor gene. Low frequencies of LOH occurred on 11p and there was little evidence for tumour suppressor loci outside the 11cen-q23.3 region. Unusually for melanomas, widespread microsatellite instability, with slippage of several repeat units, was observed in two of 32 tumours studied (and four other tumours showed new microsatellite alleles that differed by just one repeat unit from their normal counterparts). However, no mutations of the mismatch repair genes hMSH2 and hMLH1 were detected in these two tumours, and the observed replication errors may result from mutations in other genes involved in mismatch repair or DNA replication. LOH on 11q and replication errors appear to comprise part of the genetic pathways of several tumour types, including melanomas.