Microsatellite instability as a predictor of a mutation in a DNA mismatch repair gene in familial colorectal cancer

Case report: Complete response to pembrolizumab in a liver metastatic colon adenocarcinoma patient with a novel likely pathogenic germline MSH2 mutation

Lynch syndrome (LS) is a genetic disorder mainly caused by germline mutations in mismatched repair (MMR) genes (MSH2, MLH1, MSH6, and PMS2) or deletions of the epithelial cell adhesion molecule gene (EPCAM). A 43-year-old Chinese male patient underwent radical surgery and was pathologically confirmed to have stage IIIB colon adenocarcinoma. After four cycles of standard adjuvant chemotherapy, the tumor reoccurred in situ with intestinal obstruction. The patient received secondary colectomy. Immunohistochemistry analysis revealed a loss of MSH2 protein expression in the surgical specimen. Noticing that the patient's mother and grandfather all were diagnosed with LS-related cancers, we collected the patient's and his mother's peripheral blood for genetic testing, and the result showed a six-base deletion of MSH2. Thus, we concluded that our patient had LS. Subsequently, the patient accepted pembrolizumab as the first-line systemic therapy after liver metastases. He achieved clinical complete response (cCR) within 2 months and remained progression-free for more than 2 years. The case report showed that MSH2 mutation (c.489_494deTGGGTA) is a likely pathogenic mutation, and immunotherapy (pembrolizumab) is effective for this patient.

Lynch syndrome for the gynaecologist

KEY CONTENT

Lynch syndrome is an autosomal dominant condition closely associated with colorectal, endometrial and ovarian cancer.Women with Lynch syndrome are at increased risk of both endometrial and ovarian cancer and should be offered personalised counselling regarding family planning, red flag symptoms and risk-reducing strategies.Surveillance for gynaecological cancer in women with Lynch syndrome remains controversial; more robust data are needed to determine its effectiveness.Universal testing for Lynch syndrome in endometrial cancer is being adopted by centres across Europe and is now recommended by the National Institute for Health and Care Excellence; thus, gynaecologists must become familiar with testing strategies and their results.Testing strategies involve risk stratification of cancers based on phenotypical features and definitive germline testing.

LEARNING OBJECTIVES

To define the pathogenesis of Lynch syndrome and its associated gynaecological cancers.To understand the testing strategies for Lynch syndrome in women with gynaecological cancer.To learn how best to counsel women with Lynch syndrome regarding gynaecological cancer and risk-reducing strategies to enable informed decision-making.

ETHICAL ISSUES

Offering gynaecological surveillance despite a lack of robust evidence for its clinical effectiveness may falsely reassure women and delay risk-reducing hysterectomy.Genetic testing may yield variants of unknown significance with ill-defined clinical implications, which can lead to confusion and anxiety.Genetic testing has implications not only for the individual, but also for the whole family, so expert counselling is crucial.

Assessment of cervical lymph node metastasis based on total RNA from saliva and tumor tissue in patients with oral squamous cell carcinoma: An observational study

BACKGROUND

In case of oral squamous cell carcinoma (OSCC) most patients die within first 2 years due to metastasis. To overcome the limitations and drawbacks of the present available methods of assessment of lymph nodes metastasis, the search for alternative method is needed.

AIM

The aim of the study is to evaluate the sensitivity, specificity and diagnostic accuracy of salivary and tumor tissue RNA for assessment of lymph node metastasis in patients with OSCC.

METHODOLOGY

Patients histologically diagnosed with OSCC were included as participants. The unstimulated saliva and tumor tissue were collected and stored at deep freeze before surgical therapy. The pretreatment lymph node metastasis assessment was done by radioimaging investigation. The posttreatment histopathological status of cervical lymph nodes was noted. The RNA was isolated and quantified from stored saliva sample and tumor tissue. The collected data were statistically analyzed for specificity and sensitivity and significance.

RESULTS

The area under curve for salivary RNA level is 0.647 and for tumor tissue RNA level is 0.628 with moderate predictability at 95% confidence interval. It was observed that the sensitivity was 63.50% and 71.40% and specificity was 62.70% and 58.80% for saliva and tumor tissue respectively with diagnostic accuracy of 63%-65%. The Kappa statistics showed moderate degree of agreement with high statistical significance (P ≤ 0.05).

CONCLUSION

Saliva and tumor tissue RNA can be a good marker for pretreatment assessment of lymph node metastasis in patients with OSCC. Although the diagnostic accuracy which range from 63% to 65%, further characterization and study of specific mRNA, siRNA and miRNA may come out with high diagnostic accuracy.

The Cancer Immunotherapy Biomarker Testing Landscape

CONTEXT.—

Cancer immunotherapy provides unprecedented rates of durable clinical benefit to late-stage cancer patients across many tumor types, but there remains a critical need for biomarkers to accurately predict clinical response. Although some cancer immunotherapy tests are associated with approved therapies and considered validated, other biomarkers are still emerging and at various states of clinical and translational exploration.

OBJECTIVE.—

To provide pathologists with a current and practical update on the evolving field of cancer immunotherapy testing. The scientific background, clinical data, and testing methodology for the following cancer immunotherapy biomarkers are reviewed: programmed death ligand-1 (PD-L1), mismatch repair, microsatellite instability, tumor mutational burden, polymerase δ and ε mutations, cancer neoantigens, tumor-infiltrating lymphocytes, transcriptional signatures of immune responsiveness, cancer immunotherapy resistance biomarkers, and the microbiome.

DATA SOURCES.—

Selected scientific publications and clinical trial data representing the current field of cancer immunotherapy.

CONCLUSIONS.—

The cancer immunotherapy field, including the use of biomarker testing to predict patient response, is still in evolution. PD-L1, mismatch repair, and microsatellite instability testing are helping to guide the use of US Food and Drug Administration-approved therapies, but there remains a need for better predictors of response and resistance. Several categories of tumor and patient characteristics underlying immune responsiveness are emerging and may represent the next generation of cancer immunotherapy predictive biomarkers. Pathologists have important roles and responsibilities as the field of cancer immunotherapy continues to develop, including leadership of translational studies, exploration of novel biomarkers, and the accurate and timely implementation of newly approved and validated companion diagnostics.

Gene mapping and molecular analysis of hereditarynon-polyposis colorectal cancer (Lynch Syndrome)using systems biological approaches

Hereditary non-polyposis colorectal cancer (HNPCC) also known as Lynch Syndrome (LS), is a hereditary form of colorectal cancer (CRC). LSis caused by mutations in the mismatch repair (MMR) genes, mostly in MLH1, MSH2, MSH6 and PMS2. Identification of these gene mutations is essential to diagnose CRC, especially at a young age to increase the survival rate. Using open target platform, we have performed genetic association studies to analyze the different genes involved in the LS and to obtain target for disease evidence. We have also analyzed upstream regulators as target molecules in the data sets. We discovered that MLH1, MSH2, MSH6, PMS2, MLH3, EPCAM, TGFBR2, FBXO11 and PRSS58 were showing most association in LS. Our findings may further enhance the understanding of the hereditaryform of CRC.

Low Incidence of Hereditary Nonpolyposis Colorectal Cancer Syndrome in a Selected Area of the Lombardy Cancer Registry

Aims and background

Epidemiological investigations on the frequency of hereditary nonpolyposis colorectal cancer (HNPCC) syndrome are few and have shown a variable worldwide incidence ranging from 1% to 7% of all colorectal cancers (CRCs). In Italy, relevant differences have been observed: 2.8-3% of all CRCs in northern regions and less than 1% in southern regions. The aim of the present study was to investigate the HNPCC incidence in a selected area of northern Italy belonging to the Lombardy Cancer Registry.

Methods and study design

We analyzed 197 consecutive patients with newly diagnosed CRCs, histologically verified, and resident in two areas of the Lombardy Cancer Registry. For each case, genetic counseling with at least three generations pedigree reconstruction, HNPCC classification according to Amsterdam criteria, molecular analysis for microsatellite instability and immunohistochemistry for hMLH1 and hMSH2 were performed.

Results

A very low frequency (0.5%) of HNPCC fulfilling the Amsterdam criteria was found in comparison to the other Italian areas. Such an incidence seems to be due to actual population differences and reflects a genetic heterogeneity.

Conclusions

The data underline the importance of a precise knowledge of actual HNPCC incidence in different populations in order to optimize effectiveness and efficiency of screening programs for the disease.

Expression of hMLH1 and hMSH2 proteins in ameloblastomas and tooth germs

BACKGROUND

Mismatch repair proteins (MMRPs) are a group of nuclear enzymes that participate in the repair of base mismatches that occur during DNA replication in all proliferating cells. The most studied MMRPs are hMSH2 and hMLH1, which are known to be highly expressed in normal tissues. A loss of MMRPs leads to the accumulation of DNA replication errors in proliferating cells. Ki-67 is a biomarker regarded to be the gold-standard tool for determining cell proliferation by immunohistochemical methods. The aim of this study was to investigate the immunohistochemical expression of hMLH1, hMSH2 and Ki-67 proteins in ameloblastomas and tooth germs, to contribute to the understanding of the development of this odontogenic neoplasm.

MATERIAL AND METHODS

Immunohistochemical assays to determine the presence of proteins hMSH2, hMLH1 and Ki-67 were performed in 80 ameloblastomas (40 solid and 40 unicystic) and five tooth germs.

RESULTS

Unicystic ameloblastomas showed higher MMRP expression (hMLH1: 62.5 ± 43.4; hMSH2: 83.3 ± 47.8) than did solid ameloblastomas (hMLH1: 59.4 ± 13.5; hMSH2: 75.8 ± 40.2). Additionally, the cell proliferation index assessed by Ki-67 was inversely proportional to the expression of MMRP. Comparison between tooth germs and ameloblastoma revealed significantly higher expression of hMLH1, hMSH2 and Ki-67 in tooth germs (p=0.02).

CONCLUSIONS

The differences of MMRP and Ki-67 immunoexpression between ameloblastomas and tooth germ suggest that alterations in the MMRP mechanisms could participate in the biological behavior of ameloblastomas.

Genetic Testing for Hereditary Nonpolyposis Colorectal Cancer (HNPCC)

Hereditary nonpolyposis colorectal cancer (HNPCC), also called Lynch syndrome, is an autosomal dominant cancer syndrome that confers an elevated risk of early-onset colorectal cancer (CRC) and increased lifetime risk for other cancers of the endometrium, stomach, small intestine, hepatobiliary system, kidney, ureter, and ovary. Lynch syndrome accounts for up to 3% of all CRC, making it the most common hereditary colorectal cancer syndrome. Germline mutations in methyl-directed mismatch repair (MMR) genes give rise to microsatellite instability (MSI) in tumor DNA. Lynch syndrome is most frequently caused by pathogrenic variants in the mismatch repair genes MLH1, MSH2, MSH6, and PMS2. Germline mutations in MLH1 and MSH2 account for approximately 90% of detected mutations in families with Lynch syndrome. Pathogenic vatiants in MSH6 have been reported in approximately 7-10% of families with Lynch syndrome. Pathogenic variants in PMS2 account for fewer than 5% of mutations in families with Lynch syndrome. This unit presents a comprehensive molecular genetic testing strategy for Lynch syndrome including MSI analysis, next generation sequencing (NGS)-based targeted sequence analysis, PCR-based Sanger sequencing and microarray-based comparative genomic hybridization (array-CGH). © 2017 by John Wiley & Sons, Inc.

Immunohistochemical staining for p16 and BRAFV600E is useful to distinguish between sporadic and hereditary (Lynch syndrome-related) microsatellite instable colorectal carcinomas

DNA mismatch repair (MMR) protein analysis by immunohistochemistry (IHC) can identify colorectal cancer (CRC) with microsatellite instability (MSI). As MLH1-deficient CRC can be hereditary or sporadic, markers to distinguish between them are needed. MLH1 promoter methylation assay is the reference method; however, sometimes, it is challenging on formalin-fixed paraffin-embedded tissue samples. We assessed by IHC the expression of BRAFV600E, p16, MGMT, and CDX2 in 55 MLH1-deficient MSI CRC samples (of which 8 had a germline MLH1 mutation) to determine whether this panel differentiates between sporadic and hereditary CRCs. We also analyzed MLH1 promoter methylation by methylation-specific PCR and pyrosequencing and BRAF status by genotyping. None of the hereditary CRCs showed MLH1 methylation, BRAF mutation, BRAFV600E-positive immunostaining, or loss of p16 expression. We detected MLH1 promoter methylation in 67 % and a BRAF mutation in 42 % of CRC, all showing MLH1 promoter methylation. BRAFV600E IHC and BRAF genotyping gave concordant results in all but two samples. Loss of expression of p16 was found in 30 % of CRC with methylation of the MLH1 promoter, but its expression was retained in all non-methylated and part of MLH1-methylated tumors (100 % specificity, 30 % sensitivity). CDX2 and MGMT expression was not associated with MLH1 status. Thus, BRAFV600E and p16 IHC may help in differentiating sporadic from hereditary MLH1-deficient CRC with MSI. Specifically, p16 IHC might be used as a surrogate marker for MLH1 promoter methylation, because all p16-negative CRCs displayed MLH1 methylation, whereas hereditary CRCs were all p16-positive.

Identification of tumour-related proteins as potential screening markers by proteome analysis-protein profiles of human saliva as a predictive and prognostic tool

The analysis of biomarkers in saliva as a clinical application offers an attractive, simple and rapid diagnostic tool for the short- and long-term monitoring of pathological disorders and drug therapy. The collection of saliva, either in the pure or in its fractionated form, is a relatively easy and non-invasive procedure that is not harmful to the patients and has no complications at all. However, the fluid collection must be clearly defined due to variations in saliva composition, flow rate and day-to-day variability. In order to minimise possible variations, saliva from five patients without squamous cell carcinoma (SCC) pathology and five with suspicion of oral squamous carcinoma (OSCC) were collected and matched at different days and analysed by two-dimensional polyacrylamide gel electrophoresis (2DE-PAGE). Approximately 800 spots were identified, corresponding to 151 different gene products. The list of identified proteins includes a large number of structural proteins like keratins, keratin subunits, enzymes and enzyme inhibitors, cytokines, immunoglobulins as well as amylase and other salivary specific glycoproteins. The majority of proteins that are localised in oral epithelia cells were found as unsolved debris in saliva. One of the identified proteins was significantly overexpressed in OSCC and was selected for further validation by Western blot analysis.

The genetic basis of Lynch syndrome and its implications for clinical practice and risk management

Lynch syndrome is the most common cause of hereditary colon cancer, and accounts for as much as 3% of all colon and endometrial cancers. The identification and management of individuals with Lynch syndrome have evolved over the past 20 years, yet the syndrome remains vastly underdiagnosed. It is important for clinicians to recognize individuals and families who are at risk in order to be able to manage them appropriately and reduce their morbidity and mortality from this condition. This review will touch on the history of Lynch syndrome, the current knowledge of genotype–phenotype correlations, the cancers associated with Lynch syndrome, and management of individuals who are gene carriers.

Revisiting an important component of plant genomes: microsatellites

Microsatellites are some of the most highly variable repetitive DNA tracts in genomes. Few studies focus on whether the characteristic instability of microsatellites is linked to phenotypic effects in plants. We summarise recent data to investigate how microsatellite variations affect gene expression and hence phenotype. We discuss how the basic characteristics of microsatellites may contribute to phenotypic effects. In summary, microsatellites in plants are universal and highly mutable, they coexist and coevolve with transposable elements, and are under selective pressure. The number of motif nucleotides, the type of motif and transposon activity all contribute to the nonrandom generation and decay of microsatellites, and to conservation and distribution biases. Although microsatellites are generated by accident, they mature through responses to environmental change before final decay. This process is mediated by organism adjustment mechanisms, which maintain a balance between birth versus death and growth versus decay in microsatellites. Close relationships also exist between the physical structure, variation and functionality of microsatellites: in most plant species, sequences containing microsatellites are associated with catalytic activity and binding functions, are expressed in the membrane and organelles, and participate in the developmental and metabolic processes. Microsatellites contribute to genome structure and functional plasticity, and may be considered to promote species evolution in plants in response to environmental changes. In conclusion, the generation, loss, functionality and evolution of microsatellites can be related to plant gene expression and functional alterations. The effect of microsatellites on phenotypic variation may be as significant in plants as it is in animals.

BRAF V600E-specific immunohistochemistry for the exclusion of Lynch syndrome in MSI-H colorectal cancer

The differentiation between hereditary and sporadic microsatellite-unstable (MSI-H) colorectal cancer is a crucial step in Lynch syndrome diagnostics. Within MSI-H colorectal cancers, the BRAF V600E mutation is strongly associated with sporadic origin. Here, we asked whether BRAF V600E-specific immunohistochemistry (clone VE1) is helpful in separating sporadic from Lynch syndrome-associated MSI-H colorectal cancers. To that end, we performed VE1 immunohistochemistry and BRAF sequencing in a series of 91 MSI-H colorectal cancer specimens from patients tested for Lynch syndrome. Concordance of VE1 immunohistochemistry and molecular BRAF mutation status was observed in 90 of 91 (98.9%) MSI-H samples. All 11 tumors classified as BRAF V600E mutation-positive by Sanger sequencing were immunopositive, and 79 (98.8%) of 80 tumors classified as BRAF wild type showed negative staining. All VE1-positive tumors were MLH1- and PMS2-negative by immunohistochemistry. None of the tumors from mismatch repair (MMR) gene germline mutation carriers (n = 28) displayed positive VE1 staining, indicating that BRAF V600E mutation-specific immunostaining has a low risk of excluding Lynch syndrome patients from germline mutation analysis. In conclusion, implementation of VE1 immunohistochemistry was able to detect BRAF-mutated MSI-H colorectal cancers with a sensitivity of 100% and a specificity of 98.8%. Among MLH1-negative colorectal cancers, the rate of VE1-positive lesions was 21%, offering the exclusion of these patients from MMR germline testing. Therefore, we suggest the integration of VE1 immunohistochemistry into the diagnostic panel of Lynch syndrome.

Risk of breast cancer in Lynch syndrome: a systematic review

Introduction

Lynch syndrome is an autosomal dominantly inherited disorder of cancer susceptibility caused by germline mutations in the DNA mismatch repair (MMR) genes. Mutation carriers have a substantial burden of increased risks of cancers of the colon, rectum, endometrium and several other organs which generally occur at younger ages than for the general population. The issue of whether breast cancer risk is increased for MMR gene mutation carriers has been debated with evidence for and against this association.

Methods

Using the PUBMED, we identified all relevant studies of breast cancer associated with Lynch syndrome that were published by 15 December 2012. In the review, we included: (i) molecular studies that reported microsatellite instability and/or immunohistochemistry in breast cancer tumors of MMR gene mutation carriers; and (ii) risk studies that investigated risk of breast cancer for confirmed MMR gene mutation carriers or families or clinically and/or pathologically defined Lynch syndrome families.

Results

We identified 15 molecular studies and, when combined, observed 62 of 122 (51%; 95% CI 42 to 60%) breast cancers in MMR gene mutation carriers were MMR-deficient. Of the 21 risk studies identified, 13 did not observe statistical evidence for an association of breast cancer risk with Lynch syndrome while 8 studies found an increased risk of breast cancer ranging from 2- to 18-fold compared with the general population (or non-carriers). There is only one prospective study demonstrating an elevated risk of breast cancer for MMR gene mutation carriers compared with the general population (standardized incidence ratio 3.95; 95% CI 1.59, 8.13).

Conclusions

Since breast cancer is a relatively common disease in the general population, more precise estimates of risk and gene-specific risks will need to utilize large prospective cohort studies with a long follow-up. While current data are inconclusive at a population level, individual tumor testing results suggest that MMR deficiency is involved with breast cancers in some individuals with Lynch syndrome.

Hereditary colon cancer syndromes

Colon cancer is associated with a family history in up to 25% of cases. As many as 5% are associated with an established hereditary syndrome, demonstrating the profound influence of inheritable genetic mechanisms in the development of this disease. These syndromes confer a diverse spectrum of risk, age of presentation, endoscopic and histological findings, extracolonic manifestations, and modes of inheritance. As the molecular characteristics of these disorders become better described, enhanced genotype-phenotype correlations may offer a more targeted approach to diagnosis, screening, and surveillance. While the strategies for diagnosis and management of familial adenomatous polyposis (FAP) and Lynch syndrome are more established, the approach to newly recognized syndromes such as MUTYH-associated polyposis (MAP) and hyperplastic polyposis syndromes continues to evolve. Effective cancer prevention in affected individuals and at-risk family members first requires timely recognition of these hereditary colon cancer syndromes followed by integration of genetic testing and clinical examinations.

Hereditary non-polyposis colorectal cancer: identification of mutation carriers and assessing pathogenicity of mutations

Hereditary non-polyposis colorectal cancer (HNPCC), also referred to as Lynch syndrome, is an autosomal dominantly inherited disorder that is characterized by susceptibility to colorectal cancer and extracolonic malignancies, in particular endometrial cancer. HNPCC is caused by pathogenic mutations in the mismatch repair (MMR) genes, which play an important role in maintaining genomic stability during DNA replication. Identification of MMR gene mutation carriers is important as this enables them to enrol in surveillance programmes, thus reducing their risk of cancer and increasing survival. Clinical criteria as well as non-clinical criteria have been formulated to select patients for mutation analysis. In this paper we review the approaches used to select patients for mutation analysis. Mutation analysis in the MMR genes may yield mutations of which the pathogenic nature is unclear. Criteria to determine the pathogenicity of such variants are discussed, as well as differences in design of functional assays to assess pathogenicity.

Optimizing the detection of hereditary non-polyposis colorectal cancer: An update

Hereditary non-polyposis colorectal cancer (HNPCC) is a dominant inherited disease and accounts for up to 5% of all colorectal cancer (CRC) patients. Despite the optimization of selection criteria and enhancements in molecular techniques for identifying more families with HNPCC, most cases are not recognized. Poor patient recollection of family history and inadequate family history-taking are main causative factors. We propose a new strategy for detecting HNPCC, one in which the pathologist selects patients for microsatellite instability (MSI) testing. Criteria for MSI analysis are: (1) CRC before the age of 50 years, (2) second CRC before 70 years, (3) CRC and HNPCC-associated cancer before 70 years, or (4) adenoma before 40 years. Additionally, patients with a positive MSI test and patients with a positive family history are offered referral for genetic counselling. With this strategy, at least twice the number of HNPCC patients will be identified among a population of CRC patients, and in a cost-effective, efficient and feasible way. The identification of patients with HNPCC is important because intensive surveillance can prevent death from CRC.

Genetic testing for hereditary nonpolyposis colorectal cancer (HNPCC)

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant cancer syndrome that confers an elevated risk of early-onset colorectal cancer (CRC) and increased lifetime risk for other cancers of the endometrium, stomach, small intestine, hepatobiliary system, kidney, ureter, and ovary. HNPCC accounts for up to 5% of all CRC, making it the most common hereditary colorectal cancer syndrome. Germline mutations in methyl-directed mismatch repair (MMR) genes give rise to microsatellite instability (MSI) in tumor DNA. HNPCC is most often associated with mutations in the MLH1 gene on 3p21, the MSH2 gene on 2p21, and to a lesser extent MSH6 on 2p16. This unit presents a comprehensive molecular and genetic screening strategy for HNPCC mutations in the MLH1, MSH2, and MSH6 genes, including analysis of MSI, mutation scanning by denaturing high-pressure liquid chromatography (DHPLC), and DNA sequencing analysis.

Somatic BRAF-V600E mutations in familial colorectal cancer

The BRAF gene is mutated in 4% to 12% of unselected colorectal cancers, particularly those with high microsatellite instability and in premalignant lesions, such as serrated adenomas and hyperplastic polyps. However, it has been shown that activating BRAF mutations are almost never found in tumors from hereditary nonpolyposis colorectal cancer patients. To evaluate the role of oncogenic BRAF mutations in non-hereditary nonpolyposis colorectal cancer/non-familial adenomatous polyposis familial colorectal cancer, we did a mutation screening of the most common BRAF mutation, the V600E mutation, in 194 colorectal tumors from patients with a positive family history of the disease. The BRAF-V600E mutation was identified in 100% (8 of 8) of microsatellite-unstable tumors and in 9.7% (18 of 186) of microsatellite-stable tumors. Interestingly, families with extracolonic tumors showed a much higher mutation frequency (17.5%) compared with families with colonic cancer only (3.5%; P = 0.009). In addition, we studied colonoscopic results from 448 family members who had been under colonoscopic surveillance for several years. Subjects from families where the V600E mutation was identified had less adenomas compared with those from families where no BRAF mutation had been found (odds ratio, 8.5; 95% confidence interval, 1.1-64.6). These findings indicate that adenomas might be less important in the cancer development in the group of families with BRAF-V600E mutations and indirectly support a previous hypothesis that tumors might develop through the hyperplastic polyp-serrated adenoma pathway. In conclusion, our results suggest that BRAF-V600E mutations are mainly involved in colorectal cancer families characterized by an increased risk of other common malignancies.

Lynch Syndrome (Hereditary Nonpolyposis Colorectal Cancer) Diagnostics

BACKGROUND

Preventive programs for individuals who have high lifetime risks of colorectal cancer may reduce disease morbidity and mortality. Thus, it is important to identify the factors that are associated with hereditary colorectal cancer and to monitor the effects of tailored surveillance. In particular, patients with Lynch syndrome, hereditary nonpolyposis colorectal cancer (HNPCC), have an increased risk to develop colorectal cancer at an early age. The syndrome is explained by germline mutations in DNA mismatch repair (MMR) genes, and there is a need for diagnostic tools to preselect patients for genetic testing to diagnose those with HNPCC.

METHODS

Patients (n = 112) from 285 families who were counseled between 1990 and 2005 at a clinic for patients at high risk for HNPCC were selected for screening to detect mutations in MMR genes MLH1, MSH2, MSH6, and PMS2 based on family history, microsatellite instability (MSI), and immunohistochemical analysis of MMR protein expression. Tumors were also screened for BRAF V600E mutations; patients with the mutation were considered as non-HNPCC.

RESULTS

Among the 112 patients who were selected for screening, 69 had germline MMR mutations (58 pathogenic and 11 of unknown biologic relevance). Sixteen of the 69 mutations (23%) were missense mutations. Among patients with MSI-positive tumors, pathogenic MMR mutations were found in 38 of 43 (88%) of patients in families who met Amsterdam criteria and in 13 of 22 (59%) of patients in families who did not. Among patients with MSI-negative tumors, pathogenic MMR mutations were found in 5 of 17 (29%) of families meeting Amsterdam criteria and in 1 of 30 (3%) of non-Amsterdam families with one patient younger than age 50 years. In three patients with MSI-negative tumors who had pathogenic mutations in MLH1 or MSH6, immunohistochemistry showed loss of the mutated protein.

CONCLUSION

Our findings suggest that missense MMR gene mutations are common in HNPCC and that germline MMR mutations are also found in patients with MSI-negative tumors.

Molecular testing for microsatellite instability and its value in tumor characterization

Molecular analysis of tumor tissue has become a rapidly expanding field in medical research, exploiting the advantages of new technologies adapted to high-throughput examination of genetic alterations, gene and protein expression patterns. Only exceptionally, these approaches have found their way into routine clinical diagnosis and therapy. Microsatellite instability testing has been established as a very powerful tool to identify patients with hereditary nonpolyposis colorectal cancer, one of the most common familial cancer syndromes. In addition, there is emerging evidence that microsatellite instability analysis may become increasingly important for the clinician, having considerable impact on patients' prognosis as well as therapeutic decisions, at least in colorectal cancer patients. A better understanding of the microsatellite instability phenotype, its pathogenesis and implications for the course of the disease will pave the way for novel diagnostic and therapeutic strategies specifically tailored to microsatellite-unstable tumors. This review summarizes the current significance of molecular testing for microsatellite instability in several tumor entities and provides prospects of future developments.

Some aspects of molecular diagnostics in Lynch syndrome

This manuscript is composed of five parts which summarize five publications in succession. Essentially, they are concerned with molecular diagnostics of Lynch syndrome and are based on studies in 238 families. The finding that young age at diagnosis is the key feature in patients with MSH2 and MLH1 mutations (Part 1) has helped to define simple criteria for the preliminary diagnosis of this syndrome. A cheaper method for the detection of mutations has been developed (Part 2) and applied to study the types of mutations and their prevalence in Poland (Part 3) and the Baltic States (Part 4). A specific feature of these mutations, i.e. presence of recurrent mutations in the majority of affected families with mutations, has suggested the feasibility of effective diagnostics with a single test disclosing all of them. An attempt to reveal other causes of familial aggregation of colorectal cancer has ruled out any association with C insertion in the NOD2 gene (Part 5).

Prediction of germline mutations and cancer risk in the Lynch syndrome

CONTEXT

Identifying families at high risk for the Lynch syndrome (ie, hereditary nonpolyposis colorectal cancer) is critical for both genetic counseling and cancer prevention. Current clinical guidelines are effective but limited by applicability and cost.

OBJECTIVE

To develop and validate a genetic counseling and risk prediction tool that estimates the probability of carrying a deleterious mutation in mismatch repair genes MLH1, MSH2, or MSH6 and the probability of developing colorectal or endometrial cancer.

DESIGN, SETTING, AND PATIENTS

External validation of the MMRpro model was conducted on 279 individuals from 226 clinic-based families in the United States, Canada, and Australia (referred between 1993-2005) by comparing model predictions with results of highly sensitive germline mutation detection techniques. MMRpro models the autosomal dominant inheritance of mismatch repair mutations, with parameters based on meta-analyses of the penetrance and prevalence of mutations and of the predictive values of tumor characteristics. The model's prediction is tailored to each individual's detailed family history information on colorectal and endometrial cancer and to tumor characteristics including microsatellite instability.

MAIN OUTCOME MEASURE

Ability of MMRpro to correctly predict mutation carrier status, as measured by operating characteristics, calibration, and overall accuracy.

RESULTS

In the independent validation, MMRpro provided a concordance index of 0.83 (95% confidence interval, 0.78-0.88) and a ratio of observed to predicted cases of 0.94 (95% confidence interval, 0.84-1.05). This results in higher accuracy than existing alternatives and current clinical guidelines.

CONCLUSIONS

MMRpro is a broadly applicable, accurate prediction model that can contribute to current screening and genetic counseling practices in a high-risk population. It is more sensitive and more specific than existing clinical guidelines for identifying individuals who may benefit from MMR germline testing. It is applicable to individuals for whom tumor samples are not available and to individuals in whom germline testing finds no mutation.

Germline mutations of the hMLH1 and hMSH2 mismatch repair genes in Belgian hereditary nonpolyposis colon cancer (HNPCC) patients

BACKGROUND

Hereditary nonpolyposis colon cancer (HNPCC-Lynch syndrome) is caused by mutations in genes involved in DNA mismatch repair (MMR), mostly in the hMLH1 and hMSH2 genes. The mutation spectrum in the Belgian population is still poorly documented.

AIM

To report our experience on the mutation screening in Belgian familial colorectal cancer (CRC) patients, including the investigation of the pathogenicity of the missense and splice mutations. To increase the mutation detection rate by selecting the target population.

METHODS

Two hundred and twenty five Belgian patients with familial clustering of CRC were genetically tested. Point mutations in the hMLH1 and hMSH2 genes were screened by denaturing gradient gel electrophoresis (DGGE) followed by direct sequencing. Genomic deletions and duplications were assessed by multiplex ligase dependent probe amplification (MLPA) and multiplex PCR. Missense mutations were examined for pathogenicity by means of cosegregation of the mutation with the disease, microsatellite instability (MSI) in tumors, immunohistochemical staining of tumors and determination of the population frequency of the particular mutation.

RESULTS

Twenty five pathogenic mutations were identified from which 16 were novel: 7 frameshifts, one in frame deletion, 5 genomic deletions, 5 splice defects, 4 nonsense (stop) mutations and 3 missense mutations which were classified as pathogenic (out of 10 missense mutations). In retrospect, a mutation detection rate of 71% was obtained if MSI was used as a supplementary selection criterion in addition to familial clustering.

CONCLUSION

Different types of pathogenic mutations in the hMLH1 and hMSH2 genes were identified in a Belgian CRC group with familial clustering. The mutation detection yield drastically increased by preliminar selection of those familial CRC patients with a microsatellite instable tumor. Considerable attention went to the assessment of the pathogenicity of the missense mutations. In practice, the cosegregation with the disease was the most relevant criterion.

Role of detection of microsatellite instability in Chinese with hereditary nonpolyposis colorectal cancer or ordinary hereditary colorectal cancer

AIM: To detect microsatellite instability (MSI) in patients with hereditary nonpolyposis colorectal cancer or ordinary hereditary colorectal cancer and to provide criteria for screening the kindreds with hereditary nonpolyposis colorectal cancer at molecular level.

METHODS: MSI was detected in the specimens from 20 cases with HNPCC, 20 cases with ordinary hereditary colorectal cancer and 20 cases with sporadic colorectal cancer by means of polymerase chain reaction-single strand conformation polymorphism.

RESULTS: The positive rate of MSI was 85% (17/20) in HNPCC group, 40% (8/20) in ordinary hereditary colorectal cancer group and 10% (2/20) in the sporadic colorectal cancer group respectively. The differences were significant. The mean ages of the three groups were 43.6, 52.2, and 61.8 years respectively, which increased gradually. The incidence of right hemicolon cancer was 64.7%, 37.5%, and 0% respectively, which decreased gradually and had significant difference. The expression ratio of BAT26 and BAT25 was 94.1% respectively, which was highest in the 5 gene sites studied. The incidence of poorly differentiated adenocarcinoma was 70.6% in HNPCC group among high frequency microsatellite instability (MSI-H), which was higher than the other two groups, which had 50% and 50% respectively.

CONCLUSION: The incidence of MSI-H is higher in HNPCC group. The detection of MSI is simple and economical and has high correlation with the clinicopathologic feature of HNPCC and can be used as a screening method to detect the germ line mutation of the mismatch repair gene.

[Identification and management of HNPCC syndrome (hereditary non polyposis colon cancer), hereditary predisposition to colorectal and endometrial adenocarcinomas]

BACKGROUND

The HNPCC syndrome (hereditary nonpolyposis colon cancer) is an inherited condition defined by clinical and genealogical information, known as Amsterdam criteria. In about 70% of cases, HNPCC syndrome is caused by germline mutations in MMR genes, leading to microsatellite instability of tumor DNA (MSI phenotype). Patients affected by the disease are at high risk for colorectal and endometrial carcinomas, but also for small intestine, urothelial, ovary, stomach and biliary tract carcinomas. HNPCC syndrome is responsible for 5% of colorectal cancers. Identification and management of this disease are part of a multidisciplinary procedure.

METHODS

Twelve experts have been mandated by the French Health Ministry to analyze and synthesize their consensus position, and the resulting document has been reviewed by an additional group of 4 independent experts.

MAIN RECOMMENDATIONS

The lack of sensitivity of Amsterdam criteria in recognizing patients carrying a MMR germline mutation led to an enlargement of these criteria for the recruitment of possible HNPCC patients, and to a 2-steps strategy, asking first for a tumor characterization according to MSI phenotype, especially in case of early-onset sporadic cases. The identification of germline MMR mutations has no major consequence on the cancer treatments, but influences markedly the long-term follow-up and the management of at-risk relatives. Gene carriers will enter a follow-up program regarding their colorectal and endometrial cancer risks, but other organs being at low lifetime risk, no specific surveillance will be proposed.

Microsatellite instability in colorectal cancer

BACKGROUND

Microsatellite instability (MSI) causes hereditary non-polyposis colorectal cancer (HNPCC), and occurs in about 15 per cent of sporadic colorectal cancers. Although the basic mechanisms are not clear, there is increased understanding of the clinicopathological consequences of MSI.

METHODS

Medline was searched for articles with a combination of keywords relating to MSI in colorectal cancer, focusing on molecular mechanisms, clinicopathological implications, and prognostic and predictive value. Emphasis was placed on articles from the past 5 years.

RESULTS

The genetic mechanisms differ in hereditary (germline mutation) and sporadic (epigenetic silencing) colorectal cancer. The MSI pathway frequently has altered transforming growth factor beta receptor II and BAX genes, often beta-catenin, and occasionally p16INK4A and PTEN. Changes in K-ras, adenomatous polyposis coli and p53 are rare. Polymerase chain reaction testing for MSI is superior to immunohistochemistry, but complicated by the number and types of nucleotide markers. The Bethesda panel guides HNPCC testing, but guidelines are lacking for general screening. The presence and role of low-frequency MSI remains controversial. Tumours with MSI tend to occur in the proximal colon and be large, but they have a good prognosis. Their reduced response to adjuvant chemotherapy requires confirmation.

CONCLUSION

Research on colorectal cancer needs to be stratified according to microsatellite status in order further to explore the molecular mechanisms and clinicopathological consequences of MSI.

Advances in molecular diagnostics and therapeutics in head and neck cancer

Extensive treatment-related morbidities and stagnant survival rates over the past few decades for patients with squamous cell cancer of the head and neck (SCCHN) emphasize the need for novel diagnostics and therapeutics based on the molecular characteristics of the tumor. The development of an early detection test remains largely preliminary. Much attention has recently been given to saliva-based early detection assays that use accepted tumor markers such as p53 and DNA methylation. Most of these studies have focused on feasibility as opposed to prospective clinical trials. To date, early detection saliva assays have failed to yield a high enough sensitivity and specificity for broad population-based screening. The use of saliva as a noninvasive, inexpensive, and accessible diagnostic substrate remains desirable. Unlike SCCHN diagnostics, molecular-targeted therapies for SCCHN will soon be a reality, with many more compounds in the pipeline. The most promising of these drugs target the epidermal growth factor receptor (EGFR), which is known to be overexpressed in squamous cell carcinomas. Cetuximab, a monoclonal EGFR antibody, has shown efficacy in combination with radiotherapy in advanced SCCHN in a recent phase III trial and is currently being petitioned for US Food and Drug Administration approval. Likewise, erlotinib, an EGFR tyrosine kinase inhibitor, has shown favorable results in phase II trials as monotherapy and in combination with chemotherapy. Gefitinib, another EGFR tyrosine kinase inhibitor, has shown efficacy as monotherapy, in combination with chemotherapy, and with chemoradiotherapy. At least two phase III trials of gefitinib in patients with advanced SCCHN are ongoing. Such low-toxicity, tumor-specific targeting strategies will soon be available for patients with head and neck cancer. The challenge is to establish assays to determine which patients are most likely to benefit from these agents.

Tumours from MSH2 mutation carriers show loss of MSH2 expression but many tumours from MLH1 mutation carriers exhibit weak positive MLH1 staining

Microsatellite analysis (MSA) in tumour tissue is useful for pre-selection of hereditary non-polyposis colorectal cancer (HNPCC) patients for mutation screening, but is time-consuming and cost-intensive. Immunohistochemistry (IHC) for expression of MLH1 and MSH2 proteins is simple, fast, and indicates the affected gene. IHC has therefore been proposed as an alternative pre-screening method. However, some authors report a lower sensitivity of IHC compared with MSA. The present study reports IHC results for MSH2 and MLH1 performed in 82 tumours with high microsatellite instability (MSI-H) from 81 carriers of pathogenic mutations in MSH2 or MLH1. One hundred per cent (38/38) of the tumours from MSH2 mutation carriers showed loss of MSH2 staining; in all cases, the affected MSH2 gene was predicted correctly by IHC. Complete loss of MLH1 expression was observed in 66% (29/44) of MLH1 mutation carriers. Weak positive MLH1 staining was observed in 14 (32%) cases and, in one case, normal MLH1 staining was seen. The pathologist was aware of the weak staining pattern as an indicator of an MLH1 mutation; 98% of the MLH1 mutations were predicted correctly. To evaluate whether weak positive MLH1 staining is observed more often with in-frame or missense mutations, IHC data from 23 MSI-H tumours from carriers of unspecified variants were added and mutations were grouped into truncating mutations, large non-truncating deletions, and small non-truncating mutations. Weak MLH1 staining was observed in all three categories and it is postulated that other factors, such as mutation of the second allele, also influence protein expression. In conclusion, IHC can be regarded as a very useful method for selecting HNPCC patients for mutation analysis, as long as it is interpreted by an experienced pathologist. The high specificity of IHC in terms of indicating the affected gene is useful for evaluating unspecified variants. However, the staining pattern does not predict whether the underlying germ-line mutation is truncating or not.

Novel strategy for optimal sequential application of clinical criteria, immunohistochemistry and microsatellite analysis in the diagnosis of hereditary nonpolyposis colorectal cancer

Clinical criteria, microsatellite analysis (MSA) and immunohistochemistry (IHC) are important diagnostic tools for identification of hereditary nonpolyposis colorectal cancer (HNPCC) patients who are likely to carry pathogenic germline mutations in mismatch repair genes. Based on MSA and IHC results and subsequent mutation analyses of 1,119 unrelated index patients meeting the Amsterdam II criteria or the classical Bethesda guidelines, we analyzed the value of these tools to predict MLH1 and MSH2 mutations with the aim of establishing optimal strategies for their most efficient sequential use. The overall prevalence of pathogenic germline mutations in our cohort was 20.6% (95% CI = 18.3-23.0%) and 61.8% (95% CI = 56.8-66.6%), respectively, after MSA/IHC-based preselection. IHC was highly predictive (99.1%) and specific (99.6%) with regard to MSA. However, 14 out of 230 mutations (6%) escaped detection by IHC. Thus, IHC cannot be recommended to substitute MSA fully. Nonetheless, IHC is important to indicate the gene that is likely to be affected. To combine both methods efficiently, we propose a novel screening strategy that provides 2 alternative ways of sequential IHC and MSA application, either using IHC or MSA in the first place. A logistic regression model based on the age of the index patient at first tumor diagnosis and the number of fulfilled HNPCC criteria is used to allocate individual patients to that alternative pathway that is expected to be least expensive. A cost analysis reveals that about 25% of the costs can be saved using this strategy.

Use of microsatellite instability and immunohistochemistry testing for the identification of individuals at risk for Lynch syndrome

It is now generally recognized that a specific subset of those patients clinically defined as having hereditary non polyposis colon cancer (HNPCC) have germline mutations in any one of several genes involved in DNA mismatch repair (MMR). This important subset of HNPCC families is now defined as having Lynch syndrome. A considerable amount of data has shown that tumors from patients with Lynch syndrome have characteristic features resulting from the underlying molecular involvement of defective MMR, that is, the presence of microsatellite instability (MSI) and the absence of MMR protein expression by immunohistochemistry (IHC). As a result, identifying patients with Lynch syndrome can now be accomplished by testing tumors for these tumor-related changes. Together, MSI and IHC are powerful tools that help identify individuals at risk for having Lynch syndrome and to distinguish these cases from HNPCC cases with other hereditary gene defects. Furthermore, IHC analysis provides valuable clues as to which MMR gene is mutated, allowing for comprehensive mutational analyses of that gene. Here, we discuss the current and historical perspectives regarding MSI and IHC analyses in tumors from sporadic colon cancer and from patients with Lynch syndrome. Given this background, we also provide a testing strategy for the identification of patients at risk for Lynch syndrome and subsequent gene testing.

Loss of mismatch repair protein immunostaining in colorectal adenomas from patients with hereditary nonpolyposis colorectal cancer

Colorectal adenomas occur at younger age, at increased frequency and have a greater tendency for malignant transformation in patients with hereditary nonpolyposis colorectal cancer (HNPCC). We performed immunostaining for the mismatch repair proteins MLH1, PMS2, MSH2 and MSH6 in 35 colorectal adenomas from 26 patients with HNPCC and identified loss of immunostaining in 23/35 (0.66) adenomas. Loss of mismatch repair protein immunostaining was particularly frequent in large (>5 mm) (14/16) and proximally located (13/15) adenomas, whereas the gene mutated--MLH1 or MSH2--and the type of mutation did not seem to affect the results. We conclude that loss of mismatch repair protein immunostaining is detected at a lower rate in adenomas than in carcinomas associated with HNPCC. Adenomatous tissue can thus be used for immunostaining of mismatch repair proteins in clinical investigations of HNPCC, but whereas loss of immunostaining may pinpoint the gene affected and thereby guide mutation analysis, retained staining cannot exclude that the adenoma developed as part of the syndrome due to reduced sensitivity. However, the analysis has a greater chance of being informative if large and proximally located adenomas are selected.

Inherited susceptibility to colorectal cancer

The principal Mendelian disorders predisposing to colorectal cancer are familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC). FAP is due to mutations in the APC gene. HNPCC is due to a mutation in one of at least five mismatch repair genes. Identification of individuals with these conditions is important because colon cancer will occur in approximately 80% and onset is early. For FAP, protein truncation testing will identify the vast majority of mutations. For HNPCC, 80%-95% can be identified by microsatellite instability testing. A current U.S. study reports that 12% of consecutive colorectal cancers have high microsatellite instability and that, of this 12%, 25% have detectable mutations of MLH1, MSH2, or MSH6. Potential benefits of identification include improved compliance with recommended surveillance, early detection of polyps, reduction in cancer mortality, offering of testing to relatives, and reassurance for relatives found to be negative with attendant savings in the time and expense of surveillance.

Genetic testing for inherited colon cancer

The genes associated with each of the inherited syndromes of colon cancer have now been identified, and genetic testing is available for diagnosis. These syndromes include familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer, Peutz-Jeghers syndrome, juvenile polyposis syndrome, and, possibly, Cowden's syndrome. Clinical genetic testing approaches have been developed for each of these syndromes and are now a part of accepted clinical care. Disease-causing mutations can be found in the majority of families affected with one of the inherited syndromes, and, most importantly, once a mutation is found in an index case of the family, relatives can be tested for the presence or absence of that mutation with near 100% accuracy. Cancer screening and management in syndrome families is then based on the results of genetic testing. For the physician to order and properly interpret genetic tests, a basic understanding of the types of mutations that lead to inherited disease and the methods for detecting them is vital. These issues will be presented. Additional clinical issues somewhat unique to genetic testing include genetic counseling and informed consent for genetic testing, both of which will also be reviewed. Often the most difficult aspect of genetic testing is deciding which patients and families should undergo the testing. Furthermore, this issue is quite specific for each of the syndromes. Thus, following presentation of general principles of selection for genetic testing, a detailed approach for identifying persons who should undergo testing for each of the individual syndromes will be given, together with relevant descriptions of the syndromes. Finally, the ongoing work to discover new and possibly more common but less penetrant colon cancer susceptibility genes that cause common familial colon cancer will be presented.

Accuracy of MSI testing in predicting germline mutations of MSH2 and MLH1: a case study in Bayesian meta-analysis of diagnostic tests without a gold standard

Microsatellite instability (MSI) testing is a common screening procedure used to identify families that may harbor mutations of a mismatch repair (MMR) gene and therefore may be at high risk for hereditary colorectal cancer. A reliable estimate of sensitivity and specificity of MSI for detecting germline mutations of MMR genes is critical in genetic counseling and colorectal cancer prevention. Several studies published results of both MSI and mutation analysis on the same subjects. In this article we perform a meta-analysis of these studies and obtain estimates that can be directly used in counseling and screening. In particular, we estimate the sensitivity of MSI for detecting mutations of MSH2 and MLH1 to be 0.81 (0.73-0.89). Statistically, challenges arise from the following: (a) traditional mutation analysis methods used in these studies cannot be considered a gold standard for the identification of mutations; (b) studies are heterogeneous in both the design and the populations considered; and (c) studies may include different patterns of missing data resulting from partial testing of the populations sampled. We address these challenges in the context of a Bayesian meta-analytic implementation of the Hui-Walter design, tailored to account for various forms of incomplete data. Posterior inference is handled via a Gibbs sampler.

Le syndrome HNPCC (hereditary non polyposis colon cancer) : identification et prise en charge

BACKGROUND

The hereditary non-polyposis colon cancer (HNPCC) syndrome is an inherited condition defined by clinical and genealogical information, known as Amsterdam criteria. In about 70% of cases, HNPCC syndrome is caused by germline mutations in MMR genes, leading to microsatellite instability of tumor DNA (MSI phenotype). Patients affected by the disease are at high risk for colorectal and endometrial carcinomas, but also for other organs tumors. HNPCC syndrome is responsible for 5% of colorectal cancers.

MAJOR ASPECTS

The lack of sensitivity of Amsterdam criteria in recognizing patients carrying a MMR germline mutation led to an enlargement of these criteria for the recruitment of possible HNPCC patients, and to a two-steps strategy, asking first for a tumor characterization according to MSI phenotype, especially in case of early-onset sporadic cases.

FURTHER DEVELOPMENTS

The identification of germline MMR mutations has no major consequence on the cancer treatments, but influences markedly the long-term follow-up and the management of at-risk relatives. Gene carriers will enter a follow-up program regarding their colorectal and endometrial cancer risks; other organs being at low lifetime risk, no specific surveillance will be proposed.

Refining the Amsterdam Criteria and Bethesda Guidelines: testing algorithms for the prediction of mismatch repair mutation status in the familial cancer clinic

PURPOSE

Hereditary nonpolyposis colon cancer (HNPCC) is a Mendelian dominant syndrome of bowel, endometrial, and other cancers and results from germline mutations in mismatch repair (MMR) genes. HNPCC is now best diagnosed on molecular grounds using MMR mutation screening, aided by microsatellite instability (MSI) and immunohistochemistry in tumors. Selection of families for molecular investigation of HNPCC is usually based on suboptimal methods (Amsterdam Criteria or Bethesda Guidelines), but these can be improved using additional clinical data (mean ages of affected persons and presence of endometrial cancer) in a quantitative model.

METHODS

We have verified the performance of the Wijnen model and have shown that it remains valid when HNPCC is diagnosed using mutation screening, MSI, and immunohistochemistry. We have also set up and verified our own models (Amsterdam-plus and Alternative), which perform at least as well as the Wijnen model.

RESULTS

The Amsterdam-plus model improves on the Amsterdam Criteria by using five extra variables (numbers of colorectal and endometrial cancers in the family, number of patients with five or more adenomas, number with more than one primary cancer of the colorectum or endometrium, and mean age of presentation) and performs better than the Wijnen model. The Alternative model avoids the need to evaluate the Amsterdam Criteria and performs nearly as well as the other models.

CONCLUSION

We believe that a quantitative model, such as the Amsterdam-plus model, should be the first choice for selecting families or patients for evaluation of HNPCC using molecular tests. We present an algorithm for this process.

What is the best way to assess microsatellite instability status in colorectal cancer? Study on a population base of 462 colorectal cancers

The assessment of the microsatellite instability (MSI) status in colorectal cancers is presently warranted for three reasons: 1) as a screening tool for hereditary nonpolyposis colorectal cancer, 2) as a prognostic marker, and 3) as a potential predictive factor of chemotherapy response. The aim of this study was to evaluate, on a large scale with tissue samples coming from a number of different sources, the difficulties met with routine use of immunohistochemistry (IHC) and to determine if it really does offer an accurate alternative to PCR genotyping. Colorectal carcinomas from 462 consecutive patients resected in public or private hospitals were assessed for MSI status by two methods: MSI testing (with BAT-26 microsatellite) and IHC detection of hMLH1, hMSH2, and hMSH6 proteins. Of the 398 cancers tested, immunohistochemistry was noncontributory in 42 (10.5%), focal in 9 (2.3%), and discordant with the PCR results in 36 (9%). For these 87 cases, complementary analyses were performed to explain discrepancy. After additional IHC assay with modified processing protocols, 8 cases remained noncontributory, 2 focal, and 28 discordant: 18 microsatellite stability IHC/MSI PCR and 10 MSI IHC/microsatellite stability PCR. For these discordant cases, we performed a multiplex PCR assay on DNA extracted from the frozen sample and BAT-26 was amplified from DNA extracted from the paraffin blocks used for IHC. Four discordant cases were reclassified after PCR multiplex assay (3 as MSI and 1 as microsatellite stability). Five other cases displayed intratumoral heterogeneity and 19 remained discordant. The discrepancy could be partly explained by variable technical protocols of fixation in the different laboratories, leading to variations in staining quality and difficulties in IHC interpretation. This population-based study is the first one to show that IHC is not sensitive and specific enough to be used routinely. Immunohistochemistry analysis of MMR proteins must be performed in standardized conditions and interpreted by confirmed pathologists. It cannot replace PCR as long as protocols are not optimized and harmonized.

Spectrum and frequencies of mutations inMSH2 andMLH1 identified in 1,721 German families suspected of hereditary nonpolyposis colorectal cancer

Mutations in DNA MMR genes, mainly MSH2 and MLH1, account for the majority of HNPCC, an autosomal dominant predisposition to colorectal cancer and other malignancies. The evaluation of many questions regarding HNPCC requires clinically and genetically well-characterized HNPCC patient cohorts of reasonable size. One main focus of this multicenter study is the evaluation of the mutation spectrum and mutation frequencies in a large HNPCC cohort in Germany; 1,721 unrelated patients, mainly of German descent, who met the Bethesda criteria were included in the study. In tumor samples of 1,377 patients, microsatellite analysis was successfully performed and the results were applied to select patients eligible for mutation analysis. In the patients meeting the strict Amsterdam criteria (AC) for HNPCC, 72% of the tumors exhibited high microsatellite instability (MSI-H) while only 37% of the tumors from patients fulfilling the less stringent criteria showed MSI-H; 454 index patients (406 MSI-H and 48 meeting the AC of whom no tumor samples were available) were screened for small mutations. In 134 index patients, a pathogenic MSH2 mutation, and in 118 patients, a pathogenic MLH1 mutation was identified (overall detection rate for pathogenic mutations 56%). One hundred sixty distinct mutations were detected, of which 86 are novel mutations. Noteworthy is that 2 mutations were over-represented in our patient series: MSH2,c.942+3A>T and MLH1,c.1489_1490insC, which account for 11% and 18% of the MSH2 and MLH1 mutations, respectively. A subset of 238 patients was screened for large genomic deletions. In 24 (10%) patients, a deletion was found. In 72 patients, only unspecified variants were found. Our findings demonstrate that preselection by microsatellite analysis substantially raises mutation detection rates in patients not meeting the AC. As a mutation detection strategy for German HNPCC patients, we recommend to start with screening for large genomic deletions and to continue by screening for common mutations in exon 5 of MSH2 and exon 13 of MLH1 before searching for small mutations in the remaining exons.

Salivary Transcriptome Diagnostics for Oral Cancer Detection

PURPOSE

Oral fluid (saliva) meets the demand for noninvasive, accessible, and highly efficient diagnostic medium. Recent discovery that a large panel of human RNA can be reliably detected in saliva gives rise to a novel clinical approach, salivary transcriptome diagnostics. The purpose of this study is to evaluate the diagnostic value of this new approach by using oral squamous cell carcinoma (OSCC) as the proof-of-principle disease.

EXPERIMENTAL DESIGN

Unstimulated saliva was collected from patients (n = 32) with primary T1/T2 OSCC and normal subjects (n = 32) with matched age, gender, and smoking history. RNA isolation was done from the saliva supernatant, followed by two-round linear amplification with T7 RNA polymerase. Human Genome U133A microarrays were applied for profiling human salivary transcriptome. The different gene expression patterns were analyzed by combining a t test comparison and a fold-change analysis on 10 matched cancer patients and controls. Quantitative polymerase chain reaction (qPCR) was used to validate the selected genes that showed significant difference (P < 0.01) by microarray. The predictive power of these salivary mRNA biomarkers was analyzed by receiver operating characteristic curve and classification models.

RESULTS

Microarray analysis showed there are 1,679 genes exhibited significantly different expression level in saliva between cancer patients and controls (P < 0.05). Seven cancer-related mRNA biomarkers that exhibited at least a 3.5-fold elevation in OSCC saliva (P < 0.01) were consistently validated by qPCR on saliva samples from OSCC patients (n = 32) and controls (n = 32). These potential salivary RNA biomarkers are transcripts of IL8, IL1B, DUSP1, HA3, OAZ1, S100P, and SAT. The combinations of these biomarkers yielded sensitivity (91%) and specificity (91%) in distinguishing OSCC from the controls.

CONCLUSIONS

The utility of salivary transcriptome diagnostics is successfully demonstrated in this study for oral cancer detection. This novel clinical approach could be exploited to a robust, high-throughput, and reproducible tool for early cancer detection. Salivary transcriptome profiling can be applied to evaluate its usefulness for other major disease applications as well as for normal health surveillance.

The utility of immunohistochemical detection of DNA mismatch repair gene proteins

Since the development of monoclonal antibodies against the MSH2 protein by Leach et al. in 1996, a series of investigations has been undertaken to determine the utility of immunohistochemical detection of DNA mismatch repair (MMR) gene proteins in the identification of hereditary or sporadic colorectal tumors with microsatellite instability. These studies, however, have been performed with different aims and on different patient populations. Interpretation of these immunohistochemical data relies on a thorough understanding of the biological and technical factors that affect the detection of MMR proteins. In this review, we analyze the data from the published research studies, pointing out the various factors affecting immunohistochemical detection of MMR proteins and projecting the utility of immunohistochemistry in different clinical settings.

Colorectal cancer as a complex disease: defining at-risk subjects in the general population - a preventive strategy

Over the last few decades it has become clear that highly penetrant disease genes are responsible for a minor proportion of colorectal cancer cases. Families with hereditary syndromes are today recognized and included in surveillance programs known to reduce morbidity and mortality in colorectal cancer. Colorectal cancer is preventable and screening strategies in whole populations are currently under debate. Colorectal cancer can be considered a complex disease, with a combination of predisposing genetic variants and environmental factors that contribute to the illness as a whole. The progress made in the genome project provides an opportunity to determine such genetic variants and environmental factors. This knowledge can be used to define a subpopulation at increased risk for colorectal cancer. It will be more feasible to design preventive strategies for this subgroup than for a whole population.

Current clinical selection strategies for identification of hereditary non-polyposis colorectal cancer families are inadequate: a meta-analysis

Present guidelines to identify hereditary non-polyposis colorectal cancer (HNPCC) families are criticized for limitations in accuracy. The Amsterdam criteria I and II (AC I and AC II) are used to predict a germline mutation in one of the mismatch repair genes. In families not fulfilling the AC I and AC II criteria, individual indications to test cancer specimens for microsatellite instability (MSI) are guided by the Bethesda Guidelines (BG). Germline mutation testing is then performed in patients who conform to the BG and show MSI. We investigated the sensitivity and specificity of AC I, AC II, and BG. A meta-analysis of studies on the value of the AC I and AC II criteria for predicting germline mutation, as well as a meta-analysis of BG for the detection of MSI was performed. For the AC I, sensitivity varied from 54 to 91% and specificity varied from 62 to 84%. For the AC II, the pooled sensitivity was 78% and specificity ranged between 46 and 68%. Post-test probabilities of a positive test result were 0.61 and 0.46 for the AC I and AC II, respectively. Post-test probabilities of a negative test result were 0.17 and 0.21 for the AC I and AC II, respectively. For the BG, the pooled sensitivity was 89% and pooled specificity was 53%. Post-test probability of a positive test result was 41%, and post-test probability of a negative test result was 9%. The sensitivity and specificity of the Amsterdam criteria for predicting a germline mutation that causes HNPCC is not sufficient. The BG are useful for the detection of MSI in a group of patients suspected of having familial colorectal cancer (CRC), but sensitivity is very low in the total group of newly diagnosed CRC patients. Therefore, a new strategy is needed for the identification of HNPCC.

Familial breast and bowel cancer: does it exist?

There is much debate in the literature about familial predispositions to breast and bowel cancers yet little evidence is forthcoming to suggest that there are susceptibility genes that can account for such kindreds. Within the context of known susceptibility genes the most controversial syndrome is hereditary non-polyposis colorectal cancer (HNPCC). In HNPCC, breast cancers do occur yet their incidence overall is no different to that of the general population yet when studied at the molecular level these tumours often display DNA microsatellite instability suggesting that they do indeed belong to this genetic entity. In this review we examine the relationship between breast and bowel cancer and suggest a possible explanation for the diverse points of view described in the literature.

Very low incidence of microsatellite instability in rectal cancers from families at risk for HNPCC

In families at risk for hereditary non-polyposis colorectal cancer (HNPCC) that do not fulfill all clinical criteria for HNPCC, additional evidence is sought by testing cancer specimens for microsatellite instability (MSI). We investigated whether the location of a colorectal cancer (CRC) predicts the result of MSI-testing in these families. One hundred and seven patients suspected for HNPCC were offered MSI-testing. MSI-testing was positive in 6/7 patients with endometrial carcinoma and in 22/100 patients with CRC. Only one out of 22 (4%) rectal cancers was MSI-positive, and in this patient no mismatch repair (MMR) gene mutation was found. Right-sided colon carcinomas were more likely to be MSI-positive (14/37 or 38%), followed by left-sided colon carcinomas (7/4 or 17%) (p < 0.05), with 6/14 and 4/7 MMR gene mutations, respectively. The likelihood that a tumor would be MSI-positive was 3.3 times greater for right-sided than for left-sided colon cancer (OR 3.3, p < 0.05). Microsatellite instability was 8.1 times more frequent in colon cancers than in rectal cancers (p < 0.05). The presence of MSI was independently related to fulfillment of the Bethesda criteria (OR 7.0, p = 0.01). In families with multiple cases of colorectal cancer, the rectal cancers are only rarely MSI-positive. This indicates that even in families with multiple colorectal cancers, rectal cancers are most commonly of sporadic origin.