Clinical findings with implications for genetic testing in families with clustering of colorectal cancer

Prediction of the outcome of genetic testing in HNPCC kindreds using the revised Amsterdam criteria and immunohistochemistry

BACKGROUND AND AIMS

Hereditary non-polyposis colorectal cancer (HNPCC) may be caused by mutations in the mismatch repair (MMR) genes MLH1, MSH2 or MSH6. Family history (Amsterdam criteria) has traditionally been used to select patients for mutation testing. It has been demonstrated that germline mutations in the MMR genes are associated with lack of the corresponding gene product as assessed with immunohistochemistry (IHC) in tumour specimens. The aim of the study was to assess the value of the Amsterdam criteria II and IHC in predicting germline mutations.

METHODS

Fifty-six families that were previously tested for MLH1, MSH2 and MSH6 mutations were selected for this study. All pedigrees were extended and verified and the families were scored according to the original (I) and the revised Amsterdam criteria (II). The probabilities for MLH1 and MSH2 mutations were calculated by logistic regression. In addition, all available tumour material from indexed family members was examined by IHC for the presence of the three gene products.

RESULTS

Three out of seven (39%) families where the mutation could be identified complied with the Amsterdam criteria I, while all seven (100%) met the Amsterdam criteria II. All families carrying a MLH1 or MSH2 mutation had > 15% calculated probability of finding a mutation. Tumours from all seven mutation carriers lacked the immunohistochemical expression of the corresponding MMR gene.

CONCLUSION

The results indicate that the Amsterdam criteria II in combination with immunohistochemistry of the mismatch repair proteins in tumours may be a cost-effective approach to select families for mutation analysis.

Correlations between phenotype and microsatellite instability in HNPCC: implications for genetic testing

Hereditary nonpolyposis colorectal cancer (HNPCC) is widely considered to be a syndrome of defective mismatch repair (MMR). A major concern with genetic diagnosis of HNPCC is the variable, often low, percentage of pathogenic germline mutations that can be detected in MMR genes using common screening methods. The variable percentage of mutation detected is in part related to the sensitivity of conventional screening methods and may also depend on the heterogeneous genetics of HNPCC. Thus, identification of phenotypic criteria predictive of germline mutations in MMR genes may be helpful in efficient HNPCC genetic testing. Clinical diagnostic criteria, initially developed for HNPCC (e.g., Amsterdam I and II, or Bethesda criteria), can be used to clinically select patient candidates that carry germline mutations in MMR genes. More useful criteria were previously developed by analyzing families with germline MMR mutations. Using a complementary approach based on tumor microsatellite instability analysis, we confirm that the Amsterdam criteria are significantly better than the Bethesda criteria in predicting families with MSI-H tumors (P = 0.0227). Our results also suggest that a cutoff at < 50 years' mean age at diagnosis of HNPCC-related cancers (especially colorectal and endometrial cancer) may be an additional tool for the identification of families with defective MMR. Recent advances in MMR mutation screening are expected to improve detection of pathogenic MMR mutations in these families. Conversely, the high proportion of MSS tumors observed in our series of families with advanced age at cancer diagnosis is consistent with the low percentage of MMR mutations detected by previous studies in families with this phenotype. These families probably carry mutations in other genes that may or may not be related to MMR. Additional studies are necessary to clarify the molecular basis for HNPCC in families with MSS tumors.

The reliability of immunohistochemistry as a prescreening method for the diagnosis of hereditary nonpolyposis colorectal cancer (HNPCC)--results of an international collaborative study

Hereditary nonpolyposis colorectal cancer syndrome (HNPCC) is an autosomal dominant condition accounting for 2-5% of all colorectal carcinomas as well as a small subset of endometrial, upper urinary tract and other gastrointestinal cancers. An assay to detect the underlying defect in HNPCC, inactivation of a DNA mismatch repair enzyme, would be useful in identifying HNPCC probands. Monoclonal antibodies against hMLH1 and hMSH2, two DNA mismatch repair proteins which account for most HNPCC cancers, are commercially available. This study sought to investigate the potential utility of these antibodies in determining the expression status of these proteins in paraffin-embedded formalin-fixed tissue and to identify key technical protocol components associated with successful staining. A set of 20 colorectal carcinoma cases of known hMLH1 and hMSH2 mutation and expression status underwent immunoperoxidase staining at multiple institutions, each of which used their own technical protocol. Staining for hMSH2 was successful in most laboratories while staining for hMLH1 proved problematic in multiple labs. However, a significant minority of laboratories demonstrated excellent results including high discriminatory power with both monoclonal antibodies. These laboratories appropriately identified hMLH1 or hMSH2 inactivation with high sensitivity and specificity. The key protocol point associated with successful staining was an antigen retrieval step involving heat treatment and either EDTA or citrate buffer. This study demonstrates the potential utility of immunohistochemistry in detecting HNPCC probands and identifies key technical components for successful staining.

Does the occurrence of certain rare cancers indicate an inherited cancer susceptibility?

We sought to determine whether rare cancers indicate an increased risk of inherited cancer susceptibility. We ascertained 77 individuals with rare cancers which occur with increased relative risk in carriers of germline BRCA1/BRCA2 (fallopian, young-onset pancreatic) or HNPCC (biliary, small intestinal, urothelial, gallbladder, young-onset pancreatic) mutations. Individuals with two primary neoplasms (7), or with a first- or two second-degree relatives with breast/ovarian cancer were tested for BRCA1/BRCA2 mutations (18); those with two primary HNPCC cancers or one first degree relative with an HNPCC-related cancer were tested for mutations in MLH1/MSH2 (19). Of these 77 individuals with cancer (19 fallopian, 8 gallbladder, 17 biliary, 17 pancreatic, 11 urothelial, 5 small intestinal), 39 (50.6%) had at least one first degree relative with cancer (excluding lung and skin); two conformed to Bethesda HNPCC criteria. No definitely pathogenic germline MLH1 and MSH2 mutations were found in 19 individuals, although 2 MSH2 variants were detected. A family history of breast/ovarian, HNPCC or colon cancer in a first degree relative was found in 40% of fallopian, 20% of biliary, 35% of pancreatic, 27% of urothelial and 20% of small bowel cancer patients. A BRCA1 frameshift mutation was detected in a woman with fallopian (54 y) and breast (39 y) cancers, and a BRCA2 nonsense mutation in a woman with biliary (48 y) and breast (45 y) cancers. This study supports the premise that the occurrence of rare (especially double primary) cancers does indicate an increased cancer susceptibility, although the numbers of cases ascertained were too small to draw firm conclusions.

Mutations of the 'minor' mismatch repair gene MSH6 in typical and atypical hereditary nonpolyposis colorectal cancer

Mutations of the mismatch repair (MMR) genes MLH1 and MSH2 are associated with hereditary nonpolyposis colorectal cancer (HNPCC), a highly penetrant autosomal dominant condition characterized by hypermutability of short tandemly repeated sequences in tumor DNA. Mutations of another MMR gene, MSH6, seem to be less common than MLH1 and MSH2 defects, and have been mostly observed in atypical HNPCC families, characterized by a weaker tumor family history, higher age at disease onset, and low degrees of microsatellite instability (MSI), predominantly involving mononucleotide runs. We have investigated the MSH6 gene sequence in the peripheral blood of 4 HNPCC and 20 atypical HNPCC probands. Two frameshift mutations within exon 4 were detected in 2 patients. One mutation was found in a proband from a typical HNPCC family, who had developed a colorectal cancer (CRC), a gastric cancer and a rectal adenoma. The CRC and the adenoma showed mild MSI limited to mononucleotide tracts, while the gastric carcinoma was microsatellite stable. The other mutation was detected in an atypical HNPCC proband, whose CRC showed widespread MSI involving both mono- and dinucleotide repeats. The phenotypic variability associated with MSH6 constitutional mutations represents a complicating factor for the optimization of strategies aimed at identifying candidates to MSH6 genetic testing.

Hereditary nonpolyposis colorectal cancer: preventive management

Hereditary nonpolyposis colorectal cancer (HNPCC) is the most common form of hereditary colorectal cancer. Inherited mutations in the mismatch repair genes associated with this syndrome have an approximate 80% lifetime risk of colorectal cancer. Since there are no premonitory signs of susceptibility to HNPCC, family history is the initial method for identifying those at increased risk. At risk individuals should undergo genetic counseling and testing. Although an algorithmic indication for genetic testing in at risk HNPCC patients is yet to be determined, many advocate initial screening for microsatellite instability (MSI) of the cancer specimen in individuals suspected of carrying HNPCC mutations. Those who test positive for MSI can then undergo further testing for mutations in the associated germline mismatch repair genes. Techniques for detecting these mutations currently include in vitro synthesized-protein assay, single-strand conformational polymorphism, and DNA sequencing. Given the aggressive nature of HNPCC adenomas, individuals who test positive for HNPCC mutations are recommended to undergo yearly colonoscopic surveillance starting at the age of 25. A reasonable alternative to lifetime colonoscopic surveillance for the prevention of colorectal cancer in these individuals is prophylactic colectomy. The prevention of colorectal cancer through pharmacological means is under investigation as another option in the management of HNPCC patients. Specifically, chemoprevention trials are currently ongoing to evaluate the efficacy of COX-2 inhibitors in the prevention of colorectal cancer in HNPCC and familial adenomatous polyposis patients.

Comprehensive genetic counseling for families at risk for HNPCC: impact on distress and perceptions

The aim of the study was to explore distress and health beliefs before and after comprehensive interdisciplinary counseling in families at risk for hereditary non-polyposis colorectal cancer (HNPCC). Results reported here were derived from a consecutive sample of 65 counselees [31 patients with colorectal cancer (CRC) and 34 unaffected at-risk persons] who participated in interdisciplinary counseling provided by human geneticists, surgeons, and psycho-oncologists before genetic testing. Data were collected from self-administered questionnaires before, as well as 4-6 weeks after, counseling. Distress and perceptions specific to HNPCC were assessed at both timepoints using standardized as well as author-derived instruments. Distress declined after counseling, as did worries related to HNPCC. An increase was found in personal belief in control of cancer risk, for instance, in the perceived efficacy of early detection of CRC. We also observed a trend toward greater anticipated ability to cope with a positive gene test after counseling. Changes after counseling were generally more pronounced for persons at risk, as compared to patients with cancer. The decrease in distress was partly attributable to an increase in personal self-confidence. One-third of the sample reported enhanced communication specific to hereditary disease within the family after counseling. A substantial minority, however, said they experienced increased worry and physical symptoms after counseling. Overall, counselees demonstrated less stress and perceived cancer threat as well as enhanced beliefs regarding personal control over cancer, suggesting an overall beneficial impact of comprehensive counseling. Further research is needed to identify those individuals most at risk for increased fear and worry related to HNPCC so that they may be most appropriately counseled.

Genetic testing for high-risk colon cancer patients

Colorectal cancer is the third leading cause of cancer-related deaths in both men and women in the United States and is estimated to have affected 148,000 people in 2002. The cumulative lifetime risk for colon cancer is approximately 5%-6%, and this risk is influenced by hereditary and lifestyle factors. In fact, 20%-30% of all colon cancer cases have a potentially definable inherited cause, and 3%-5% of colon cancers occur in genetically defined high-risk colon cancer family syndromes. Although the genes responsible for the cases of moderate-risk colon cancer remain to be characterized, many of the genes responsible for the high-risk colon cancer cases have already been determined. These genetic discoveries have been translated into clinical practice and have led to improved risk assessment through the use of genetic testing. The introduction into clinical practice of genetic testing for the assessment of colon cancer risk has led to more effective management strategies for patients with potentially high-risk colon cancer and has presented new challenges to the clinician because of the unique issues involved with genetic testing. In this review, an overview of the colon cancer high-risk syndromes, with a focus on the availability and indications for genetic testing, is presented.

Molecular analysis of hereditary nonpolyposis colorectal cancer in the United States: high mutation detection rate among clinically selected families and characterization of an American founder genomic deletion of the MSH2 gene

The identification of germline mutations in families with HNPCC is hampered by genetic heterogeneity and clinical variability. In previous studies, MSH2 and MLH1 mutations were found in approximately two-thirds of the Amsterdam-criteria-positive families and in much lower percentages of the Amsterdam-criteria-negative families. Therefore, a considerable proportion of HNPCC seems not to be accounted for by the major mismatch repair (MMR) genes. Does the latter result from a lack of sensitivity of mutation detection techniques, or do additional genes underlie the remaining cases? In this study we address these questions by thoroughly investigating a cohort of clinically selected North American families with HNPCC. We analyzed 59 clinically well-defined U.S. families with HNPCC for MSH2, MLH1, and MSH6 mutations. To maximize mutation detection, different techniques were employed, including denaturing gradient gel electrophoresis, Southern analysis, microsatellite instability, immunohistochemistry, and monoallelic expression analysis. In 45 (92%) of the 49 Amsterdam-criteria-positive families and in 7 (70%) of the 10 Amsterdam-criteria-negative families, a mutation was detected in one of the three analyzed MMR genes. Forty-nine mutations were in MSH2 or MLH1, and only three were in MSH6. A considerable proportion (27%) of the mutations were genomic rearrangements (12 in MSH2 and 2 in MLH1). Notably, a deletion encompassing exons 1-6 of MSH2 was detected in seven apparently unrelated families (12% of the total cohort) and was subsequently proven to be a founder. Screening of a second U.S. cohort with HNPCC from Ohio allowed the identification of two additional kindreds with the identical founder deletion. In the present study, we show that optimal mutation detection in HNPCC is achieved by combining accurate and expert clinical selection with an extensive mutation detection strategy. Notably, we identified a common North American deletion in MSH2, accounting for approximately 10% of our cohort. Genealogical, molecular, and haplotype studies showed that this deletion represents a North American founder mutation that could be traced back to the 19th century.

Multiple primary cancer, including transitional cell carcinoma of the upper uroepithelial tract in a multigeneration HNPCC family: molecular genetic, diagnostic, and management implications

OBJECTIVE

We report a multigeneration family where colorectal cancer and cancer of multiple diverse anatomic sites, inclusive of transitional cell carcinoma of the upper uroepithelial tract, were manifested in several relatives.

METHODS

A specific pattern of cancer of the colorectum, endometrium, ovary, small bowel, and transitional cell carcinoma, with a vertical distribution of this cancer phenotype through multiple generations, was consonant with a diagnosis of hereditary nonpolyposis colorectal cancer.

RESULTS

Germline mutation testing identified the MSH2 mutation, which segregated with the cancer phenotype. This family study clearly demonstrates the value of genetic testing in the management and treatment decision process.

CONCLUSIONS

We document, perhaps for the first time, how molecular genetic testing in hereditary nonpolyposis colorectal cancer can aid in the identification of a potential renal transplant donor for a relative with the MSH2 mutation who is experiencing renal insufficiency secondary to transitional cell carcinoma.

A636P is associated with early-onset colon cancer in Ashkenazi Jews

BACKGROUND

Hereditary predisposition to colorectal cancer most often manifests itself as familial adenomatous polyposis from mutations of APC, or hereditary nonpolyposis colorectal cancer, resulting from mutations of MSH2, MLH1, MSH6, or other genes. Previously, we described a rare founder mutation MSH2*1906C > G in Ashkenazi Jews that was found in 8 of 1,345 individuals (0.6%) of Ashkenazi descent with colorectal cancer. This study seeks to characterize the proportion of individuals of Ashkenazi heritage with very early-onset colon cancer (diagnosed at age 40 or younger) that could be attributed to MSH2*1906C>G.

STUDY DESIGN

We analyzed the carrier frequency of MSH2*1906C>G in paraffin samples from 31 Jewish patients age 40 or less, diagnosed with colorectal cancer at Memorial Sloan-Kettering and lymphocyte-derived DNA from 10 patients. We did not select for family history. Genotyping for MSH2*1906C>G was performed by polymerase chain reaction and restriction enzyme digestion methods.

RESULTS

We detected the MSH2*1906G>C mutation in 3 of the 41 samples (7.14%) of patients who had colorectal cancer diagnosed at age 40 or younger. This incidence is significantly greater than the 8 in 1,345 (0.6%) we observed for cases of colorectal cancer in Ashkenazi Jews not selected for age (p = 0.004).

CONCLUSION

Although very rare in the population, MSH2*1906G>C is found at an increased frequency in young Jewish patients with colorectal cancer. These results suggest that testing for the MSH2*1906G>C mutation should be included in the evaluation of Ashkenazi Jewish individuals diagnosed with early-onset colon cancer.

A training course for oncology nurses in familial cancer risk assessment: evaluation of knowledge and practice

BACKGROUND

With the availability of genetic testing for cancer, a variety of health professionals are needed to counsel individuals seeking cancer risk information. To address the educational needs of oncology nurses, a training course in familial cancer risk assessment and counseling was developed at Fox Chase Cancer Center, Philadelphia, Pennsylvania.

METHODS

Four training sessions were conducted with 164 nurses. Knowledge was assessed from pretest to posttest using Wilcoxon's signed-rank test. Comparison of practice in cancer risk assessment (CRA) was measured at baseline and six months with McNemar's procedures.

RESULTS

There was statistically significant improvement in knowledge from pre to post test. There was self-reported improvement in collecting family histories and assessing cancer risk. Those reporting current practice in risk assessment post-training were more likely to collect required family history information and had greater confidence in skills.

CONCLUSIONS

With education and opportunity to practice, nurses can play key roles in CRA.

Genetic and epigenetic alterations in colon cancer

Colorectal cancer affected approximately 135,000 people in the United States in 2001, resulting in 57,000 deaths. Colorectal cancer develops as the result of the progressive accumulation of genetic and epigenetic alterations that lead to the transformation of normal colonic epithelium to colon adenocarcinoma. The loss of genomic stability is a key molecular and pathophysiologic step in this process and serves to create a permissive environment for the occurrence of alterations in tumor suppressor genes and oncogenes. Alterations in these genes, which include APC, CTNNB1, K-RAS, MADH4/SMAD4, and TGFBR2, appear to promote colon tumorigenesis by perturbing the function of signaling pathways, such as the TGF-ss signaling pathway, or by affecting genes that regulate genomic stability, such as the mutation mismatch repair genes.

After hMSH2 and hMLH1--what next? Analysis of three-generational, population-based, early-onset colorectal cancer families

The aim of our study was to examine the role of genetic factors on early-onset colorectal cancer after excluding the impact of germline mutations in the two major mismatch repair genes. A total of 131 incident probands, under 45 years at diagnosis of a first primary colorectal cancer selected from the Victorian Cancer Registry, and their first-and second-degree relatives, were interviewed. Germline DNA from all 12 probands with a family history meeting the modified Amsterdam Criteria for Hereditary Non-Polyposis Colorectal Cancer (HNPCC) and a random sample of 31 of the remaining probands was screened for mutations in hMSH2 and hMLH1 via manual sequencing. Germline mutations were identified in 6 of the 131 probands (5%), all from the "HNPCC" families. Of the remaining 125 probands, 51 (41%) reported at least one first-or second-degree relative with colorectal cancer with an excess of colorectal cancer in first-degree relatives (SMR = 2.7, 95% CI = 1.7-4.1, p < 0.001). The lifetime risk to age 70 for first-degree relatives was 8.0% (5.0-12.8%), compared to the Victorian population risk of 3.2% (p = 0.01). The best fitting major gene model was a recessively-inherited risk of 98% to age 70 (95% CI = 24-100%) carried by 0.17% of the population and would explain 15% of all colorectal cancer in cases with a diagnosis before age 45. Early-onset colorectal cancer is strongly familial even after excluding families found to be segregating a mutation in either of the 2 major mismatch repair genes. There is evidence for a role of yet to be identified genes associated with a high recessively-inherited risk of colorectal cancer.

Review article: genetic testing and counselling for hereditary colorectal cancer

Colorectal cancer is the second leading cause of cancer death, after lung cancer, in the USA. The great majority (80%) of patients with colorectal cancer have sporadic disease with no evidence of having inherited the disorder. In the remaining 20%, a potentially definable genetic component exists. With the discovery of gene mutations related to hereditary colorectal cancer, risk assessment based on genetic test results is now feasible. The following review focuses on the two well-described colorectal cancer genetic syndromes-familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, the process of genetic counselling, currently available genetic tests, and indications for their use.

Comparison of selection strategies for genetic testing of patients with hereditary nonpolyposis colorectal carcinoma: effectiveness and cost-effectiveness

BACKGROUND

Molecular testing for hereditary nonpolyposis colorectal carcinoma (HNPCC) is becoming standard care and it is cost-effective compared with no genetic testing. However, the best strategy for detection of HNPCC gene carriers is unknown.

METHODS

We use a decision analytic model to evaluate the effectiveness and incremental cost-effectiveness of four commonly used testing strategies to detect HNPCC gene carriers. The model starts with a population of colorectal carcinoma (CRC) patients and measures costs, the number of gene carriers detected, and incremental costs per gene carrier detected.

RESULTS

We found that germline testing on only those CRC probands who meet the Amsterdam criteria detects the fewest gene carriers and has the lowest cost whereas tumor microsatellite instability (MSI) testing of all CRC patients and families has the highest cost and detects the most gene carriers. When cost-effectiveness is considered, the mixed strategy (MSH2 and MLH1 testing on those who meet the Amsterdam criteria and germline testing for the remainder who meet less stringent modified criteria and are MSI-High) seems superior. The mixed strategy detects 59.6 mutation carriers per 1000 CRC cases and costs much less than the test all strategy, which has an incremental cost-effectiveness of $51,151. The mixed strategy often other strategies and when compared to the Amsterdam strategy, has a cost-effectiveness of only $6441 per gene carrier detected.

CONCLUSIONS

It is not very effective to limit genetic testing to only individuals who meet the Amsterdam criteria, as many gene carriers are missed. However, testing all CRC patients for tumor MSI-H, although effective, may be prohibitively expensive. A mixed strategy is the more cost-effective approach.

Genomic deletions of MSH2 and MLH1 in colorectal cancer families detected by a novel mutation detection approach

Hereditary non-polyposis colorectal cancer is an autosomal dominant condition due to germline mutations in DNA-mismatch-repair genes, in particular MLH1, MSH2 and MSH6. Here we describe the application of a novel technique for the detection of genomic deletions in MLH1 and MSH2. This method, called multiplex ligation-dependent probe amplification, is a quantitative multiplex PCR approach to determine the relative copy number of each MLH1 and MSH2 exon. Mutation screening of genes was performed in 126 colorectal cancer families selected on the basis of clinical criteria and in addition, for a subset of families, the presence of microsatellite instability (MSI-high) in tumours. Thirty-eight germline mutations were detected in 37 (29.4%) of these kindreds, 31 of which have a predicted pathogenic effect. Among families with MSI-high tumours 65.7% harboured germline gene defects. Genomic deletions accounted for 54.8% of the pathogenic mutations. A complete deletion of the MLH1 gene was detected in two families. The multiplex ligation-dependent probe amplification approach is a rapid method for the detection of genomic deletions in MLH1 and MSH2. In addition, it reveals alterations that might escape detection using conventional diagnostic techniques. Multiplex ligation-dependent probe amplification might be considered as an early step in the molecular diagnosis of hereditary non-polyposis colorectal cancer.

A 10-Mb paracentric inversion of chromosome arm 2p inactivates MSH2 and is responsible for hereditary nonpolyposis colorectal cancer in a North-American kindred

Genomic deletions of the MSH2 gene are a frequent cause of hereditary nonpolyposis colorectal cancer (HNPCC), a common hereditary predisposition to the development of tumors in several organs including the gastrointestinal and urinary tracts and endometrium. The mutation spectrum at the MSH2 gene is extremely heterogeneous because it includes nonsense and missense point mutations, small insertions and deletions leading to frameshifts, and larger genomic deletions, the latter representing approximately 25% of the total mutation burden. Here, we report the identification and molecular characterization of the first paracentric inversion of the MSH2 locus known to cause HNPCC. Southern blot analysis and inverse PCR showed that the centromeric and telomeric breakpoints of the paracentric inversion map within intron 7 and to a contig 10 Mb 3' of MSH2, respectively. Pathogenicity of the paracentric inversion was demonstrated by conversion analysis. The patient's lymphocytes were employed to generate somatic cell hybrids to analyze the expression of the inverted MSH2 allele in an Msh2-deficient rodent cellular background. The inversion was shown to abolish MSH2 expression by both northern and western analysis. This study confirms that Southern blot analysis still represents a useful and informative tool to screen for and identify complex genomic rearrangements in HNPCC. Moreover, monoallelic expression analysis represents an attractive approach to demonstrate pathogenicity of unusual mutations in autosomal dominant hereditary conditions.

Hereditary non-polyposis colorectal cancer (HNPCC): phenotype-genotype correlation between patients with and without identified mutation

Affected members of hereditary non-polyposis colorectal cancer (HNPCC) families develop colorectal cancer at an early age (mean 45 yr) and frequently get extracolonic cancers particularly in the uterus, urinary tract, and small intestine. They have a high risk of developing more than one primary colorectal cancer if not treated with subtotal colectomy at first operation and have more frequent right-sided colon cancers and less frequent rectum cancers, compared to patients with sporadic colorectal cancer. We have screened 31 families fulfilling the Amsterdam criteria and 54 families with a colorectal cancer clustering but not fulfilling the Amsterdam criteria for mutations in MLH1 and MSH2 by direct sequencing, and detected a mutation in 61% of the Amsterdam positive families but only in 15% of the Amsterdam negative families. Genotype-phenotype correlation was compared between 141 affected individuals with an identified mutation and 78 affected individuals from Amsterdam positive families in which a mutation was not identifiable in MLH1 or MSH2. In the affected persons with identified mutations, all expected phenotypic traits were represented, whereas affected persons in whom no mutation was detected fell into two clearly distinguishable subgroups. The minor subgroup, in which no mutation was identified, generally had the same characteristics as found in affected persons with identified mutations. The major subgroup differed significantly in clinical features and exhibited phenotypic traits similar to those found in late-onset families, including abundance of rectal cancer, few HNPCC-related cancers, lower frequency of multiple colorectal cancers, and later age at onset. Finally, for six missense mutations and one single codon deletion, the pathogenic potential was evaluated by domain localization, lod score calculation or segregation analysis when possible, and mutation-induced biochemical change. The results indicate that the majority of missense mutations are pathogenic, although further characterization by functional assays is necessary before implementation in predictive testing programs.

A population-based study of the extent of surgical resection of potentially curable colon cancer

BACKGROUND

We attempted to determine factors contributing to the extent of initial curative resection for colon cancer in a population-based cohort. Total abdominal colectomy with ileorectal anastomosis (TAC-IR) may be considered for young patients or those with a colorectal cancer family history to prevent metachronous lesions and facilitate surveillance.

METHODS

All Ontario patients newly diagnosed with colon cancer over 12 months beginning in July 1997 were staged at the time of surgery. The extent of resection was compared with variables, including familial risk obtained from the Ontario Familial Colon Cancer Registry.

RESULTS

Complete staging was possible for 86% of patients. A total of 1223 patients had a potentially curative resection: 17%, 46%, and 36% were stage I, II, and III, respectively. Patients were more likely to receive a TAC-IR if they were < or = 50 years old (odds ratio [OR], 3.5; 95% confidence interval [CI], 1.8-6.6), if they had a synchronous lesion (OR, 28.37; 95% CI, 12.2-61.2), or if they were at a teaching hospital (OR, 2.8; 95% CI, 1.6-4.7), but not if they had a family history (OR,.7; 95% CI,.3- 1.5).

CONCLUSIONS

Young age, teaching hospital, and multiple cancers but not family history were important factors for performing a TAC-IR.

High frequency of microsatellite instability and loss of mismatch-repair protein expression in patients with double primary tumors of the endometrium and colorectum

BACKGROUND

Patients with the familial syndrome hereditary nonpolyposis colorectal carcinoma (HNPCC) exhibit an increased risk for several tumor types, of which the greatest lifetime risk is for colorectal and endometrial carcinoma. HNPCC is caused by a germline mutation in one of several identified mismatch repair (MMR) genes and typically presents with microsatellite instability (MSI) and frequent loss of MMR protein expression in the tumor tissue. The objective of this study was to estimate the proportion of double primary tumors of the endometrium and colorectum that displays tumor characteristics suggestive of MMR deficiency.

METHODS

The authors used the southern Sweden regional population-based Cancer Registry to identify women who developed double primary tumors of the endometrium and colorectum. Of the 256 women who were diagnosed with carcinoma at both of these sites during the period 1958-1998, 39 women had developed their first tumor before age 50 years. The authors successfully retrieved 67 tumors from 36 of these patients and analyzed them for MSI and immunohistochemical expression of the MMR genes, MLH1, MSH2, and MSH6.

RESULTS

The MSI status of the 67 tumors was high MSI in 37 tumors, low MSI in 13 tumors, and microsatellite stable (MSS) in 17 tumors. Immunohistochemical loss of MMR protein expression was correlated with MSI status and was demonstrated in 29 high MSI tumors, in 1 low MSI tumor, and in 1 MSS tumor. A concordant loss of the same MMR protein in both tumors was found in 12 of 27 patients.

CONCLUSIONS

The authors demonstrated a high frequency of MSI (75%) in tumors from women with endometrial and colorectal carcinoma who had their first tumor diagnosed before age 50 years and observed concordant immunohistochemical loss of MMR protein expression, suggestive of a possible underlying germline mutation, in 12 of 27 patients (44%). They concluded that double primary malignancies of the colorectum and endometrium at a young age should make the clinician suspect HNPCC.

Cancer genetics and their application to individualised medicine

One of the great challenges of basic research is to translate scientific discoveries into the improved treatment of patients. For colorectal cancer, our increased understanding of the molecular aetiology of the disease has not yet been paralleled by an improvement in patient care. However, several new approaches are on the verge of clinical implementation. Technical advances such as real-time polymerase chain reaction (PCR) and microarray techniques coupled to insight in the molecular pathways in colorectal cancer makes it possible to develop new clinical tools for the diagnosis, classification and treatment of patients. The ultimate goal of the incorporation of cancer genetics into the clinical treatment of patients is individualised medicine; therapeutic strategies based on the molecular taxonomy of tumours and individually constructed for each patient.

Risk assessment & genetic testing

Ovarian cancer is the fifth most common cause of cancer death in women in Western countries and family history is one of the strongest known risk factors. Approximately 5 to 13% of all ovarian cancer cases are caused by the inheritance of cancer predisposing genes with an autosomal pattern of transmission. The inherited fraction of ovarian cancer may differ between populations. Based on analysis of familial ovarian cancer pedigrees and other epidemiological studies, three hereditary ovarian cancer syndromes have been defined. The identification of the genes responsible for most hereditary ovarian cancers has open a new area of early detection methods and preventive procedures specifically dedicated to women identified as carrying ovarian cancer predisposing genes. Predictive oncology is best performed by a dedicated unit with professionals aware of all the issues surrounding genetic testing.

Prevalence of germline mutations of MLH1 and MSH2 in hereditary nonpolyposis colorectal cancer families from Spain

HNPCC is an autosomal dominantly inherited cancer-susceptibility syndrome that confers an increased risk for colorectal cancer and endometrial cancer at a young age. It also entails an increased risk of a variety of other tumors, such as ovarian, gastric, uroepithelial and biliary tract cancers. The underlying pathogenic mutation lies in 1 of the 5 known DNA MMR genes (MSH2, MLH1, PMS1, PMS2 and MSH6). We screened a total of 140 individuals from 56 Spanish families with suspected HNPCC for mutations in the DNA mismatch repair genes MLH1 and MSH2, using DGGE and direct DNA sequencing. Families were selected on the basis of a history of HNPCC-related tumors or the occurrence of other associated tumors in members besides the index case affected with colorectal cancer. We detected 14 definite pathogenic germline mutations, 9 in MLH1 and 5 in MSH2 in 13 unrelated families selected by the Amsterdam criteria and Bethesda guidelines (1 family carries 2 mutations) and 3 missense mutations in 3 unrelated families selected by the Amsterdam criteria. Among the 17 germline mutations noted in the Spanish cohort, 10 are novel, 7 in MLH1 and 3 in MSH2, perhaps demonstrating different mutational spectra in the Spanish population, where no founder mutation has been identified. Based on our results, we suggest that in the Spanish population not only HNPCC families fulfilling the Amsterdam criteria but also those following Bethesda guidelines should undergo genetic testing for MSH2 and MLH1 mutations.

Methods of molecular analysis: mutation detection in solid tumours

Most mutation detection techniques are unsuitable for routine use on solid tumours. Important parameters include sensitivity, specificity, efficiency, use of existing resources, and cost. In the UK, < 0.2% of service genetics laboratory activity involves mutation analysis in tumours (usually for family studies), mainly because it is time consuming/labour intensive (thus expensive) and DNA extracted from formalin fixed, paraffin wax embedded tissue is of low quality and yield. The small size of DNA fragments obtained from tissue blocks limits the polymerase chain reaction, the basis of most mutation detection methods. Other, biological, factors include: (1) heterogeneity of mutations within and between tumours, (2) variation in type and site of mutations in any one gene, (3) normal tissue harbouring mutations, (4) few genes are mutated in most of any one tumour type, and (5) few clinically useful correlations with genetic changes have been found. Present research is centred on correlating single gene mutations with various clinicopathological features, but the pattern of mutations in a combination of genes will probably prove more useful. Microsatellite instability, however, appears to be worth testing for in both familial and sporadic tumours, particularly of the colorectum.

Family history and colorectal cancer screening: a survey of physician knowledge and practice patterns

OBJECTIVES

Risk stratification is essential to effective implementation of colorectal cancer (CRC) screening strategies. The objectives of this study were to assess and compare the current knowledge and practice patterns of gastroenterologists and primary care physicians regarding familial risk of CRC.

METHODS

We conducted a survey of regional gastroenterologists and a sample of university- and community-based primary care physicians. The survey instrument assessed physician knowledge of screening recommendations and current practices for individuals with family histories of CRC, adenomatous polyps (APs), familial adenomatous polyposis (FAP), and hereditary nonpolyposis cancer (HNPCC). The instrument also elicited data about familial risk assessment, documentation, and notification of at-risk family members.

RESULTS

Thirty-five gastroenterologists (65%) and 58 primary care physicians (92%) completed the survey. Most gastroenterologists and primary care physicians (85% vs 72%) chose age 40 as the appropriate age to begin screening for a family history of CRC, but relatively few (37% vs 36%) recommended screening at age 40 for a family history of APs. Gastroenterologists were significantly more likely to recommend screening for FAP at puberty (80% vs 27%, p < 0.001) and for HNPCC at age 25 (73% vs 50%, p = 0.04). Colonoscopy was the preferred screening strategy by both groups for family histories of CRC (97%), HNPCC (97%), and APs (77%); primary care physicians also preferred colonoscopy for family histories of CRC (72%) and HNPCC (76%) but flexible sigmoidoscopy plus fecal occult blood testing for a family history of APs (38%). Gastroenterologists were more likely to recommend genetic testing for persons at risk of FAP (91% vs 71%, p = 0.03) and HNPCC (72% vs 57%, p = 0.18), routinely inquire about a family history of CRC or APs (93% vs 63%, p < 0.001), and recommend notification of at-risk first-degree relatives with family histories of CRC (94% vs 55%, p < 0.001) or AP (53% v.s 6%, p < 0.001).

CONCLUSION

Although gastroenterologists are more likely than primary care physicians to elicit a family history of colorectal neoplasia and implement appropriate screening strategies, overall compliance with recommended guidelines and notification of at-risk relatives are suboptimal. Novel approaches for improving awareness of the available screening guidelines are needed.

Hereditary nonpolyposis colorectal cancer in young colorectal cancer patients: high-risk clinic versus population-based registry

BACKGROUND & AIMS

Early onset colorectal cancer (CRC) is an important feature of hereditary nonpolyposis colorectal cancer (HNPCC). We sought to compare rates of genetically defined HNPCC among individuals with early onset CRC drawn from a high-risk clinic and a population-based cancer registry.

METHODS

Probands with CRC diagnosed before 36 years of age were enrolled from a high-risk CRC clinic at the University of California, San Francisco (UCSF), and a population-based Kaiser Permanente (KP) Health Plan cancer registry. Probands provided cancer family histories and tumors for microsatellite instability (MSI) testing and MSH2/MLH1 protein immunostaining. Germline MSH2 and MLH1 mutational analysis was performed.

RESULTS

Forty-three probands were enrolled from UCSF and 23 from KP. The UCSF and KP probands had similar median age of onset of CRC (30 vs. 31 years) and the percentage with any personal or family history of another HNPCC-related cancer (70% vs. 74%). However, 28 of 40 (70%) of the UCSF tumors were MSI-H compared with 6 of 18 (33%) of KP tumors (P = 0.01), and 13 germline MSH2 or MLH1 mutations were found in the UCSF group compared with 0 in the KP group (P = 0.0001). In a multivariate analysis, institution (P = 0.002) and the total number of colorectal cancers in the family (P = 0.0001) were independent predictors of MSH2 or MLH1 mutation.

CONCLUSIONS

Family history of cancer is an important feature of HNPCC, even among individuals with early onset CRC. Caution must be undertaken when extrapolating data regarding HNPCC from high-risk clinic populations to the general population.

Papillary renal cell carcinoma: analysis of germline mutations in the MET proto-oncogene in a clinic-based population

Approximately 10% of all renal cell carcinomas (RCCs) present a distinctive papillary histology. Familial papillary RCC (PRCC) has been described, but the majority of cases appear to be sporadic. Recently, germline mutations in the MET proto-oncogene on chromosome 7 have been identified in families with hereditary PRCC. We evaluated 59 patients with PRCC for the frequency of MET germline mutations to determine the value of genetic screening of this patient population. Between 1976 and 1997, 165 patients were identified with PRCC by retrospective chart review. Fifty-nine of 133 surviving patients agreed to provide a family history, a blood specimen, and informed consent for genetic research. DNA was isolated from peripheral blood leukocytes. Denaturing high-performance liquid chromatography (DHPLC) followed by genomic sequencing was performed on eight exons of the MET proto-oncogene, including exons 5-7 of the extracellular domain, exon 14, and exons 16-19 of the tyrosine kinase domain. The 59 patients in this study included 49 men and 10 women with a mean age at diagnosis of 61 years. Bilateral and/or multifocal disease was present in 13 cases (22%). No germline mutations were detected in the studied exons of the MET proto-oncogene (exons previously reported to contain deleterious mutations in familial PRCC). No pathological MET proto-oncogene germline mutations were identified in 59 patients with PRCC. The germline mutation rate in this clinic-based population of individuals with PRCC approaches 0% (CI = 0-6.18). MET proto-oncogene germline mutation screening does not appear to be clinically indicated in patients with PRCC without additional evidence for a genetic predisposition (positive family history, unusual age at onset, bilateral disease).

Molecular and clinical characteristics of MSH6 variants: an analysis of 25 index carriers of a germline variant

The MSH6 gene is one of the mismatch-repair genes involved in hereditary nonpolyposis colorectal cancer (HNPCC). Three hundred sixteen individuals who were known or suspected to have HNPCC were analyzed for MSH6 germline mutations. For 25 index patients and 8 relatives with MSH6 variants, molecular and clinical features are described. For analysis of microsatellite instability (MSI), the five consensus markers were used. Immunohistochemical analysis of the MLH1, MSH2, and MSH6 proteins was performed. Five truncating MSH6 mutations, of which one was detected seven times, were found in 12 index patients, and 10 MSH6 variants with unknown pathogenicity were found in 13 index patients. Fourteen (54%) of 26 colorectal cancers (CRCs) and endometrial cancers showed no, or only weak, MSI. Twelve of 18 tumors of truncating-mutation carriers and 3 of 17 tumors of missense-mutation carriers showed loss of MSH6 staining. Six of the families that we studied fulfilled the original Amsterdam criteria; most families with MSH6, however, were only suspected to have HNPCC. In families that did not fulfill the revised Amsterdam criteria, the prevalence of MSH6 variants is about the same as the prevalence of those in MLH1/MSH2. Endometrial cancer and/or atypical hyperplasia were diagnosed in 8 of 12 female carriers of MSH6 truncating mutations. Most CRCs were localized distally in the colon. Although, molecularly, missense variants are labeled as doubtfully pathogenic, clinical data disclose a great resemblance between missense-variant carriers and truncating-mutation carriers. We conclude that, in all patients suspected to have HNPCC, MSH6-mutation analysis should be considered. Neither MSI nor immunohistochemistry should be a definitive selection criterion for MSH6-mutation analysis.

DNA mismatch repair defects: role in colorectal carcinogenesis

The inactivation of the DNA mismah repair (MMR) system, which is associated with the predisposition to the hereditary non-polyposis colorectal cancer (HNPCC), has also been documented in nearly 20% of the sporadic colorectal cancers. These tumors are characterized by a high frequency of microsatellite instability (MSI(+) phenotype), resulting from the accumulation of small insertions or deletions that frequently arise during replication of these short repeated sequences. A germline mutation of one of the two major MMR genes (hMSH2 or hMLH1) is found in half to two-thirds of the patients with HNPCC, whereas in sporadic cases hypermethylation of the hMLH1 promoter is the major cause of the MMR defect. Germline mutations in hMSH6 are rare and rather confer predisposition to late-onset familial colorectal cancer, and frequent extracolonic tumors. Yet, the genetic background of a number of HNPCC patients remains unexplained, indicating that other genes participate in MMR and play important roles in cancer susceptibility. The tumor-suppressor genes that are potential targets for the MSI-driven mutations because they contain hypermutable repeated sequences are likely to contribute to the etiology and tissue specificity of the MSI-associated carcinogenesis. Because the prognosis and the chemosensitivity of the MSI(+) colorectal tumors differ from those without instability, the determination of the MSI phenotype is expected to improve the clinical management of patients. This review gives an overview of various aspects of the biochemistry and genetics of the DNA mismah repair system, with particular emphasis in its role in colorectal carcinogenesis.

Cancer genetics fundamentals

It is often said that cancer is genetic. What exactly does that mean? This article is our answer to that question at the turn of the millennium. We present models of carcinogenesis, review basic cancer genetics terminology, and explain some of the fundamental genetic changes common to all types of cancer. These are organized into 6 sections of (1) self-sufficiency in growth signals, (2) insensitivity to growth-inhibitory signals, (3) evasion of programmed cell death, (4) limitless replicative potential, (5) sustained angiogenesis, and (6) tissue invasion and metastases. Underlying all of these changes are the even more fundamental enabling factors of genetic instability on both the chromosomal and the gene level. Finally, we look toward the future in a field where the future is now!

MSH2 mutation carriers are at higher risk of cancer than MLH1 mutation carriers: a study of hereditary nonpolyposis colorectal cancer families

PURPOSE

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant disease characterized by the clustering of colorectal cancer, endometrial cancer, and various other cancers. The disease is caused by mutations in DNA-mismatch-repair (MMR) genes, most frequently in MLH1, MSH2, and MSH6. The aims of the present study were to compare the risk of developing colorectal, endometrial, and other cancers between families with the various MMR-gene mutations.

PATIENTS AND METHODS

Clinical and pathologic data were collected from 138 families with HNPCC. Mutation analyses were performed for all families. Survival analysis was used to calculate the cumulative risk of developing cancer in the various subsets of relatives.

RESULTS

Mutations were identified in 79 families: 34 in MLH1, 40 in MSH2, and five in MSH6. The lifetime risk of developing cancer at any site was significantly higher for MSH2 mutation carriers than for MLH1 mutation carriers (P < .01). The risk of developing colorectal or endometrial cancer was higher in MSH2 mutation carriers than in MLH1 mutation carriers, but the difference was not significant (P = .13 and P = .057, respectively). MSH2 mutation carriers were found to have a significantly higher risk of developing cancer of the urinary tract (P < .05). The risk of developing cancer of the ovaries, stomach, and brain was also higher in the MSH2 mutation carriers than in the MLH1 mutation carriers, but the difference was not statistically significant.

CONCLUSION

Pending large prospective studies, the extension of the current surveillance program in MSH2 mutation carriers with the inclusion of the urinary tract should be considered.

RB1 genetic testing as a clinical service: a follow-up study

BACKGROUND

Genetic testing for inherited predisposition to diverse cancers has recently become available as a clinical service. We conducted a follow-up study of the initial series of US families who underwent RB1 genetic testing to evaluate long-term effects of the service.

PROCEDURE

We enrolled 52 of 71 eligible families who responded to a follow-up study questionnaire administered 3-10 years after receipt of their RB1 results. Each family had one proband with unilateral, non-familial retinoblastoma, which is associated with a 12% pre-test probability of hereditary retinoblastoma. RB1 testing identified germline RB1 mutations in five patients, lowered the carrier probability to 2% in 21 patients, and did not substantially modify the carrier probability in the remaining 26.

RESULTS

Diverse medical specialists offered and arranged for RB1 testing, and their recommendation was the most influential factor in the decision to be tested. Pre-test counseling was provided by ophthalmologists (30), oncologists (11), and geneticists and genetic counselors (11). Most respondents, regardless of test result, were satisfied and perceived gains from their genetic testing. Based on small numbers, families with reduced likelihood of hereditary retinoblastoma reported more positive outcomes. Parents of RB1 carriers were more likely to seek medical services, worry, and decide against having more children.

CONCLUSIONS

This study demonstrates the feasibility of follow-up studies of families who had genetic testing. Results from our small series suggest that genetic information and counseling are important components of RB1 clinical genetic testing, and long-term adverse effects of testing are uncommon.

Evaluation of Bethesda guidelines in relation to microsatellite instability

PURPOSE

The Bethesda guidelines were developed for selection of patients whose tumors should be tested for high microsatellite instability. This study examined the validity of the different Bethesda criteria in relation to microsatellite instability status to simplify their use in clinical practice.

METHODS

A total of 164 patients with colorectal or hereditary nonpolyposis colorectal cancer-associated cancers were registered on the basis of the Amsterdam criteria without age limitations (11 cases), multiple tumors (2 cases), the accumulation of colorectal cancer in the family (no first-degree relatives affected or the index patient's age up to 50 years; 45 cases), an early age at onset up to 50 years (13 cases), morphologic and histopathologic manifestations (right-sided colorectal cancer, mucinous undifferentiated histology; 1 case), and the Bethesda criteria (92 cases). The microsatellite instability status of tumors was determined using the International Collaborative Group on Hereditary Non-Polyposis Colorectal Cancer marker reference panel.

RESULTS

When applying all Bethesda criteria, high microsatellite instability tumors were identified in our hereditary nonpolyposis colorectal cancer registry with a sensitivity of 87 percent. Twenty-nine percent (27/92) of the Bethesda-positive patients displayed high microsatellite instability compared with 6 percent of patients (4/72) not meeting these criteria (P < 0.001). Only Bethesda Criteria 1, 3, and 4 showed a significantly different distribution of the microsatellite instability status when compared with those of the remaining patients registered (P < or = 0.001). These three criteria detected high microsatellite instability tumors in 48 percent (10/21), 50 percent (18/36), and 31 percent (21/67) of patients, respectively. When applying these criteria only, a cumulative detection rate of 77 percent of all (24/31) high microsatellite instability cases was found, thereby identifying 89 percent of high microsatellite instability tumors among the Bethesda-positive patients. Patients matching Criteria 1, 3, and 4 frequently showed hMSH2 or hMLH1 germline mutations and tumor-specific loss of protein expression.

CONCLUSION

In our hereditary nonpolyposis colorectal cancer registry the complete Bethesda criteria showed the highest sensitivity to identify patients with high microsatellite instability tumors. However, for general medical practice outside academic centers, three criteria are reasonably accurate for adequate high microsatellite instability tumor selection.

Common hereditary cancers and implications for primary care

The identification of genes that place individuals at high risk of breast, ovarian, and colorectal cancer has greatly advanced our understanding of cancer predisposition over the past decade. This knowledge has received much attention from the media, and referrals to geneticists and surgeons, and requests for genetic testing, have risen. We review the published evidence for the management of people at increased risk of hereditary cancers, to draw attention to areas of uncertainty and to discuss implications for primary care. We focus on common inherited cancers, since they will have the greatest effect on clinical practice over the next decade. Cancer genetics offers a model of how information on the genetics of other common diseases could affect primary care in the future. Strategies to support the integration of genetic medicine in primary care are needed to enable primary-care practitioners to identify individuals at raised genetic risk and to reassure patients for whom genetic testing and increased surveillance offer little benefit.

Causes of microsatellite instability in colorectal tumors: implications for hereditary non-polyposis colorectal cancer screening

Microsatellite instability (MSI) analysis was performed using a "reference panel" of microsatellite markers in 345 unselected primary colorectal cancers (CRC). Thirty-five (10%) tumors were classified as high MSI (MSI-H). We identified 6 (17%) MSI-H tumors with germline mutations in mismatch repair (MMR) genes (tumors from patients with hereditary non-polyposis colorectal cancer (HNPCC) syndrome) and 29 (83%) MSI-H tumors without germline MMR mutations (sporadic MSI-H tumors). Hypermethylation of the hMLH1 promoter was found in 26/29 (90%) sporadic MSI-H tumors but only in 1/6 (17%) HNPCC tumors (P<.001). Somatic alterations were identified in both MMR genes in HNPCC tumors but mainly in the hMSH2 gene in sporadic MSI-H tumors. LOH at MMR loci was detected in 3/6 (50%) HNPCC tumors and in 4/26 (15%) informative sporadic MSI-H tumors. These results together indicate different mode of inactivation of MMR genes in sporadic MSI-H tumors versus MSI-H tumors in HNPCC patients. We therefore propose that MSI analysis of newly diagnosed primary CRC followed by methylation analysis of hMLH1 promoter in MSI-H tumors and mutational analysis of MMR genes in MSI-H tumors lacking hMLH1 promoter methylation might be an efficient molecular genetic approach for HNPCC screening.

Tolerance of human MSH2+/- lymphoblastoid cells to the methylating agent temozolomide

Members of hereditary nonpolyposis colon cancer (HNPCC) families harboring heterozygous germline mutations in the DNA mismatch repair genes hMSH2 or hMLH1 present with tumors generally two to three decades earlier than individuals with nonfamilial sporadic colon cancer. We searched for phenotypic features that might predispose heterozygous cells from HNPCC kindreds to malignant transformation. hMSH2(+/-) lymphoblastoid cell lines were found to be on average about 4-fold more tolerant than wild-type cells to killing by the methylating agent temozolomide, a phenotype that is invariably linked with impairment of the mismatch repair system. This finding was associated with an average 2-fold decrease of the steady-state level of hMSH2 protein in hMSH2(+/-) cell lines. In contrast, hMLH1(+/-) heterozygous cells were indistinguishable from normal controls in these assays. Thus, despite the fact that HNPCC families harboring mutations in hMSH2 or hMLH1 cannot be distinguished clinically, the early stages of the carcinogenic process in hMSH2 and hMLH1 mutation carriers may be different. Should hMSH2(+/-) colonocytes and lymphoblasts harbor a similar phenotype, the increased tolerance of the former to DNA-damaging agents present in the human colon may play a key role in the initiation of the carcinogenic process.

Role of chance in familial aggregation of colorectal cancer

A prospective population-based study recorded family trees of 77 colorectal cancer patients younger than 50 years of age. Using mathematical modeling of population age-incidence data, we estimate that 1 (95% confidence limits 0 and 3) of these families is expected to meet the Amsterdam criteria I for HNPCC due to chance clustering of colorectal cancer.

Multiple primary malignancies: An epidemiological and pedigree analysis of 57 patients with at least three tumours

AIM AND METHODS

Data of our patients with at least three primary malignancies were retrospectively analysed to detect any remarkable patterns which might be of interest for follow-up or early tumour detection and to identify a possible hereditary cancer predisposition. From 1.1.1954 to 1.8.1995 57 patients (0.1%) among a grand total of 52 398 cancer patients had a minimum of three malignancies.

RESULTS

The 5-year survival rates after colorectal, bladder, prostate, uterine corpus and gastric cancer were higher than those seen in patients with the corresponding solitary tumours. In both sexes, the mean interval between the individual tumours was greater (4.0 years) between the first and second tumours than between the second and third (2.5 years). In women, the intervals were roughly twice as long (6.8 and 3.7 years) as in men (3.7 and 2.0 years). 40.4% (n=23/57) had a colorectal, 28.1% (n=16) a bladder, and 41.7% (n=15/36 men) had a prostate carcinoma. 66.7% (n=14/21 women) contracted at least one gynaecological tumour. In 24 families HNPCC, in one a Li-Fraumeni Syndrome, and in another Hereditary Diffuse Gastric Cancer was suspected.

Role of molecular diagnostic testing in familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer families

PURPOSE

Genetic tests are available for familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer. The goal of this review was to develop an algorithm for application of molecular diagnostic techniques to the management of hereditary colorectal carcinoma and to familiarize the clinician with the vocabulary of molecular genetic testing for hereditary colorectal carcinoma.

METHODS

Studies examining the clinical use of genetic testing for hereditary colorectal carcinoma syndromes are evaluated. Recent advances in molecular genetic technology are reviewed, and clinical management as practiced here and elsewhere is outlined.

RESULTS

This review is a guide to the most reliable molecular diagnostic techniques. Three key questions are answered: who, when, and how to test.

CONCLUSIONS

When integrated with existing testing protocols for colorectal carcinoma and when applied with appropriate caveats, particularly regarding interpretation of negative results, genetic testing can result in improved management of patients and families.

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

BACKGROUND & AIMS

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Hereditary nonpolyposis colorectal cancer in 95 families: differences and similarities between mutation-positive and mutation-negative kindreds

Hereditary nonpolyposis colorectal cancer (HNPCC) describes the condition of a disparate group of families that have in common a predisposition to colorectal cancer in the absence of a premalignant phenotype. The genetic basis of this disease has been linked to mutations in genes associated with DNA mismatch repair. A large proportion of families harbor changes in one of two genes, hMSH2 and hMLH1. Approximately 35% of families in which the diagnosis is based on the Amsterdam criteria do not appear to harbor mutations in DNA-mismatch-repair genes. In this report we present data from a large series of families with HNPCC and indicate that there are subtle differences between families that harbor germline changes in hMSH2 and families that harbor hMLH1 mutations. Furthermore, there are differences between the mutation-positive group (hMSH2 and hMLH1 combined) of families and the mutation-negative group of families. The major findings identified in this study focus primarily on the extracolonic disease profile observed between the mutation-positive families and the mutation-negative families. Breast cancer was not significantly overrepresented in the hMSH2 mutation-positive group but was overrepresented in the hMLH1 mutation-positive group and in the mutation-negative group. Prostate cancer was not overrepresented in the mutation-positive groups but was overrepresented in the mutation-negative group. In age at diagnosis of colorectal cancer, there was no difference between the hMSH2 mutation-positive group and the hMLH1 mutation-positive group, but there was a significant difference between these two groups and the mutation-negative group.

Linkage heterogeneity for the IBD1 locus in Crohn's disease pedigrees by disease onset and severity

BACKGROUND & AIMS

There is evidence for the IBD1 Crohn's disease (CD) susceptibility locus on chromosome 16 in several but not all populations studied. Genetic and phenotypic heterogeneity may underlie ability to replicate IBD1. We determined if age and severity stratification could identify a clinical subgroup at risk for IBD1.

METHODS

Linkage analysis at microsatellites spanning chromosome 16 was performed in 2 groups of CD pedigrees: group 1, 57 pedigrees with at least one affected relative classified as having "severe" disease, by history of surgical resection or immunomodulator therapy, and with disease diagnosed before age 22; and group 2, 33 pedigrees with no history of early-onset, severe CD.

RESULTS

Group 1 pedigrees demonstrated genomewide significant linkage evidence for the IBD1 locus (nonparametric multipoint logarithm of the odds [Mlod], 3.84; P = 1.3 x 10(-5)) with linkage evidence greater than all 90 pedigrees (Mlod, 2.12; P = 9.0 x 10(-4)). Group 2 pedigrees had near zero nonparametric 2-point and Mlod scores for the IBD1 region. Heterogeneity between groups 1 and 2 was significant (P = 0.002).

CONCLUSIONS

Presence of early-onset, more severe CD identifies pedigrees at high risk for IBD1. These pedigrees will have more power to refine the IBD1 locus and identify the causative gene.

Prediction of a mismatch repair gene defect by microsatellite instability and immunohistochemical analysis in endometrial tumours from HNPCC patients

Instability of microsatellite repeat sequences has been observed in colorectal carcinomas and in extracolonic malignancies, predominantly endometrial tumours, occurring in the context of hereditary non-polyposis colorectal cancer (HNPCC). Microsatellite instability (MSI) as a feature of human DNA mismatch repair (MMR)-driven tumourigenesis of the uterine mucosa has been studied primarily in sporadic tumours showing predominantly somatic hypermethylation of MLH1. The present study shows that all endometrial carcinomas (n=12) from carriers of MLH1 and MSH2 germline mutations demonstrate an MSI-high phenotype involving all types of repeat markers, while in endometrial carcinomas from MSH6 mutation carriers, only 36% (4 out of 11) demonstrate an MSI-high phenotype. Interestingly, an MSI-high phenotype was found in endometrial hyperplasias from MSH2 mutation carriers, in contrast to hyperplasias from MLH1 mutation carriers, which exhibited an MSI-stable phenotype. Instability of only mononucleotide repeat markers was found in both endometrial carcinomas and hyperplasias from MSH6 mutation carriers. In 29 out of 31 (94%) endometrial tumour foci, combined MSI and immunohistochemical analysis of MLH1, MSH2, and MSH6 could predict the identified germline mutation. The observation of MSI in endometrial hyperplasia and of altered protein staining for the MMR genes supports the idea that inactivation of MMR genes is an early event in endometrial tumourigenesis. A correlation was found between the variation in the extent and level of MSI and the age of onset of carcinoma, suggesting differences in the rate of tumour progression. A high frequency of MSI in hyperplasias, found only in MSH2 mutation carriers, might indicate a more rapid tumour progression, correlating with an earlier age of onset of carcinoma. The present study indicates that assessment of altered protein staining combined with MSI analysis of endometrial tumours might direct the mutational analysis of MMR genes.