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

Mixed and nonvaccine high risk HPV types are associated with higher mortality in Black women with cervical cancer

We studied the incidence of HPV genotypes in mostly Black women with cervical carcinoma and correlated histopathologic tumor characteristics, immune markers and clinical data with survival. Disease-free survival (DFS) and overall survival (OS) were recorded for 60 months post-diagnosis. Fifty four of the 60 (90%) patients were Black and 36 (60%) were < 55 years of age. Of the 40 patients with typeable HPV genotypes, 10 (25%) had 16/18 HPV genotypes, 30 (75%) had one of the non-16/18 HPV genotypes, and 20 (50%) had one of the 7 genotypes (35, 39, 51, 53, 56, 59 and 68) that are not included in the nonavalent vaccine. Mixed HPV infections (≥ 2 types) were found in 11/40 (27.5%) patients. Patients infected with non-16/18 genotypes, including the most common genotype, HPV 35, had significantly shorter DFS and OS. PD-L1 (p = 0.003), MMR expression (p = 0.01), clinical stage (p = 0.048), histologic grade (p = 0.015) and mixed HPV infection (p = 0.026) were independent predictors of DFS. A remarkably high proportion of cervical cancer cells in our patients expressed PD-L1 which opens the possibility of the use of immune checkpoint inhibitors to treat these cancers. Exclusion of the common HPV genotypes from the vaccine exacerbates mortality from cervical cancer in underserved Black patients.

Development of novel quality control material based on CRISPR/Cas9 editing and xenografts for MLH1 protein deficiency testing

BACKGROUND

Mismatch repair deficiency (dMMR) status induced by MLH1 protein deficiency plays a pivotal role in therapeutic decision-making for cancer patients. Appropriate quality control (QC) materials are necessary for monitoring the accuracy of MLH1 protein deficiency assays used in clinical laboratories.

METHODS

CRISPR/Cas9 technology was used to edit the MLH1 gene of GM12878Cas9 cells to establish MLH1 protein-deficient cell lines. The positive cell lines were screened and validated by Sanger sequencing, Western blot (WB), and next-generation sequencing (NGS) and were then used to prepare formalin-fixed, paraffin-embedded (FFPE) samples through xenografting. These FFPE samples were tested by hematoxylin and eosin (H&E) staining and immunohistochemistry (IHC) for suitability as novel QC materials for MLH1 protein deficiency testing.

RESULTS

We successfully cultured 358 monoclonal cells, with a survival rate of 37.3% (358/960) of the sorted monoclonal cells. Through Sanger sequencing, cell lines with MLH1 gene mutation were identified. Subsequently, two cell lines with MLH1 protein deficiency were identified by WB and named as GM12878Cas9_6 and GM12878Cas9_10. The NGS results further confirmed that the MLH1 gene mutation in these two cell lines would cause the formation of stop codons and terminate the expression of the MLH1 protein. The H&E staining and IHC results also verified the deficiency of the MLH1 protein, and FFPE samples from xenografts proved their similarity and consistency with clinical samples.

CONCLUSIONS

We successfully established MLH1 protein-deficient cell lines. Followed by xenografting, we developed novel FFPE QC materials with homogenous, sustainable, and typical histological structures advantages that are suitable for the standardization of clinical IHC methods.

Lynch Syndrome: Its Impact on Urothelial Carcinoma

Lynch syndrome, known as hereditary nonpolyposis colorectal cancer (HNPCC), is an autosomal-dominant familial cancer syndrome with an increased risk for urothelial cancer (UC). Mismatch repair (MMR) deficiency, due to pathogenic variants in MLH1, MSH2, MSH6, and PMS2, and microsatellite instability, are known for development of Lynch syndrome (LS) associated carcinogenesis. UC is the third most common cancer type in LS-associated tumors. The diversity of germline variants in the affected MMR genes and their following subsequent function loss might be responsible for the variation in cancer risk, suggesting an increased risk of developing UC in MSH2 mutation carriers. In this review, we will focus on LS-associated UC of the upper urinary tract (UUT) and bladder, their germline profiles, and outcomes compared to sporadic UC, the impact of genetic testing, as well as urological follow-up strategies in LS. In addition, we present a case of metastatic LS-associated UC of the UUT and bladder, achieving complete response during checkpoint inhibition since more than 2 years.

Shrestha T, Zilfalil BA. MLH1 and MSH2 mismatch repair protein profile using immunohistochemistry in Nepalese colorectal cancer patients

BACKGROUND Hereditary nonpolyposis colorectal cancer, or Lynch syndrome, caused by germline mutations or genetic defects in mismatch repair (MMR) genes (MLH1, MSH2, PMS2, MSH6, and epithelial cellular adhesion molecule), is an autosomal dominant condition accounting for 2–5% of all colorectal carcinomas (CRCs). Reports on MMR loss in many populations are available; however, there are no reports on the frequency of MMR protein expression in Nepalese cohorts. Therefore, this study was aimed to assess the expression profiles of MLH1 and MSH2 protein by immunohistochemistry (IHC) in Nepalese CRC patients. METHODS This retrospective study used archived formalin-fixed paraffin-embedded tissue blocks from 43 Nepalese CRC patients. IHC staining was performed using MLH1 and MSH2 antibodies. IHC scoring analysis was assessed using semiquantitative scoring. RESULTS Of the 43 CRC patients, 8 (18.6%) showed loss of staining for MLH1 antibody, 5 (11.6%) showed loss of staining for MSH2 antibody, and 4 (9.3%) showed loss of staining for both MLH1 and MSH2 antibodies. CONCLUSIONS IHC is a potential screening method of determining the MMR expression profile of Nepalese CRC patients. IHC can be performed in local clinical laboratories to find MMR protein defects in selected cases prior to expensive molecular tests.

Screening for Lynch Syndrome by Immunohistochemistry of Mismatch Repair Proteins: Significance of Indeterminate Result and Correlation With Mutational Studies

CONTEXT.—

Immunohistochemical expression of mismatch repair (MMR) protein is a well-accepted method for routine screening for Lynch syndrome with relatively high sensitivity and specificity. Occasionally, however, immunohistochemistry (IHC) can yield an equivocal result with poor reproducibility and the potential for misdiagnosis.

OBJECTIVE.—

To determine the frequency and significance of indeterminate MMR IHC expression in patients routinely screened for Lynch syndrome and correlation with germline mutation studies.

DESIGN.—

Semiquantitative scoring of MMR IHC was performed by image analysis in 479 cases, of which 380 were colorectal and 99 endometrial cancer. Scores of 10% or more, less than 10%, and 0% were used as cutoffs for retained, indeterminate, and loss of expression, respectively. Negative and indeterminate IHC results were confirmed by mutational studies.

RESULTS.—

Four hundred eighteen of 479 cases (87.2%) were reported as retained expression, 45 (9.3%) as loss of expression, and 16 (3.3%) as indeterminate expression. Fifteen of 45 (33.3%) and 8 of 16 (50%) with loss and indeterminate expression, respectively, were found to have Lynch syndrome by germline studies. The overall frequency of Lynch syndrome in our patient population was 4.8% (23 of 479), and 34.7% of these (8 of 23) were associated with indeterminate IHC expression. In the indeterminate group, MLH1 germline mutation was the most frequent (6 of 13; 46.2%), followed by MSH6 (4 of 13; 30.7%).

CONCLUSIONS.—

Our findings provide further evidence that indeterminate IHC should be further investigated for possible MMR germline mutation. Guidelines for interpretation of MMR IHC and the establishment of more objective criteria for defining indeterminate results are important to improve the sensitivity and specificity of the IHC assay.

Two-stain immunohistochemical screening for Lynch syndrome in colorectal cancer may fail to detect mismatch repair deficiency

Universal screening for Lynch syndrome in colorectal cancer is recommended, and immunohistochemistry for the mismatch repair proteins is commonly used. To reduce cost, some screen using only MSH6 and PMS2, with reflex to the partner stain if either are absent (two-stain method). An expression pattern revealing absent MSH2 and intact MSH6 is not expected, but could result in failed Lynch syndrome detection. We analyzed tumors with absent MSH2 but any degree of MSH6 expression to determine if the two-stain method could miss MSH2 mutations. One-thousand seven-hundred thirty colorectal cancer patients from the Ohio Colorectal Cancer Prevention Initiative underwent tumor screening using microsatellite instability and immunohistochemistry. The two-stain method was used for 1235 cases; staining for all four proteins was completed for 495 cases. The proportion of positive cells and staining intensity were reviewed for MSH6, as well as MSH2 when available. Patients with mismatch repair deficiency underwent next-generation sequencing of germline DNA for mismatch repair genes. If negative, tumor next-generation sequencing was performed to assess for somatic mutations. Overall, thirty-three (1.9%, 33/1730) MSH2-absent cases were identified. Of those, fourteen had no MSH6 expression but eight (0.5%, 8/1730) had ambiguous and eleven (0.6%, 11/1730) had convincing MSH6 expression that could have been interpreted as intact. Germline next-generation sequencing identified MSH2 mutations in 11/14 cases with absence of both stains, 7/8 cases with ambiguous MSH6 expression, and 9/11 cases with convincing MSH6 expression. All remaining cases, except one, had double somatic mutations. The two-stain method fails to detect some patients with Lynch syndrome: (1) significant staining weaker than the control may be incorrectly interpreted as intact MSH6, or (2) Weak or focal/patchy MSH6 can be retained with the absence of MSH2. Accordingly, we recommend the four-stain method be used for optimal Lynch syndrome screening detection.

Mouse Models of Brain Metastasis for Unravelling Tumour Progression

Secondary tumours in the brain account for 40 % of triple negative breast cancer patients, and the percentage may be higher at the time of autopsy. The use of in vivo models allow us to recapitulate the molecular mechanisms potentially used by circulating breast tumour cells to proliferate within the brain.Metastasis is a multistep process that depends on the success of several stages including cell evasion from the primary tumour, distribution and survival within the blood stream and cerebral microvasculature, penetration of the blood-brain barrier and proliferation within the brain microenvironment. Cellular adhesion molecules are key proteins involved in all of the steps in the metastatic process. Our group has developed two different in vivo models to encompass both seeding and colonisation stages of the metastatic process: (1) haematogenous dissemination of tumour cells by direct injection into the left ventricle of the heart, and (2) direct implantation of the tumour cells into the mouse brain.This chapter describes, in detail, the practical implementation of the intracerebral model, which can be used to analyse tumour proliferation within a specific area of the central nervous system and tumour-host cell interactions. We also describe the use of immunohistochemistry techniques to identify, at the molecular scale, tumour-host cell interactions, which may open new windows for brain metastasis therapy.

Discordant Mismatch Repair Protein Immunoreactivity in Lynch Syndrome-Associated Neoplasms: A Recommendation for Screening Synchronous/Metachronous Neoplasms

OBJECTIVES

Lynch syndrome (LS) predisposes individuals to developing synchronous and metachronous LS-associated neoplasms (LSANs). Mismatch repair protein (MMRP) immunohistochemistry (IHC) is widely used to identify LS, but its utility in patients with synchronous/metachronous lesions has not been studied. We studied MMRP IHC in patients with LS with more than one LSAN to provide screening recommendations in patients with synchronous/metachronous neoplasms.

METHODS

All patients with LS diagnosed at The Ohio State University Wexner Medical Center from 2009 through 2014 with more than one LSAN and available tumor tissue for immunostaining were identified. Tumors were stained for MLH1, MSH2, MSH6, and PMS-2 proteins, and immunoreactivity was scored as intact or lost.

RESULTS

Thirteen patients with LS with 29 synchronous and/or metachronous primary LSANs were identified. Neoplasms involved large and small intestine (n = 19), ampulla (n = 1), endometrium (n = 1), and skin (sebaceous neoplasms, n = 8). Nine (69%) of 13 patients showed concordant MMRP results in all tumors, and four (31%) showed discordant MMRP results.

CONCLUSIONS

LS diagnosis could have been missed in 31% of the study cases if only the LSAN exhibiting intact MMRP expression was screened. Accordingly, our findings support the recommendation to perform LS screening in all primary, synchronous, and metachronous intestinal and endometrial cancers if a previous tumor screened intact.

MutSα and MutLα immunoexpression analysis in diagnostic grading of oral epithelial dysplasia and squamous cell carcinoma

OBJECTIVES

This study explored the expression of DNA mismatch repair (MMR) proteins in a range of oral biopsies. We further evaluated the significance of MMR protein expression combined with basic demographic data in differentiating grades of oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC).

STUDY DESIGN

Immunohistochemical expression of MutSα (hMLH1 and hPMS2) and MutLα (hMSH2 and hMSH6) were compared in 98 formalin-fixed paraffin embedded oral biopsies: 21 normal, 24 mild-dysplasia (MD), 8 moderate-to-severe-dysplasia (SD), and 45 OSCC.

RESULTS

Expression of hMLH1, hPMS2, and hMSH2 was reduced in MD, SD, and OSCC compared with the normal. Reduced hMSH2 immunoreactivity discriminated poorly differentiated OSCC from well-differentiated OSCC. The diagnostic model correctly classified 71.4% of cases and revealed that hPMS2-negative biopsies were more likely to be cancerous (odds ratio [OR], 0.11; 95% confidence interval [CI], 0.000-0.813; P = .040).

CONCLUSION

The results suggested a diagnostic role for MMR proteins in OED and OSCC.

On the limits of genetic responsibility: Communication and consent for tumour testing for Lynch syndrome

Testing cancers for mismatch repair (MMR) gene defects assists selection of families for genetic testing for cancer predisposing Lynch syndrome. Performing MMR tumour testing without consent is debated, though little empirical work has been undertaken. We address this by examining the significance of testing for those who have consented without prior genetic counselling, particularly their ‘accounts’ of testing via displays of knowledge and responsibility. Semi-structured interviews were conducted with participants recruited from a UK genetics service. Participants had difficulties in formulating the benefits of testing when consent was facilitated by a relative or by mail. Discourse analysis revealed that in the absence of specific or accurate understandings of tumour testing, participants displayed responsibility towards themselves and others by generalising and diminishing the implications of testing. Within the framework of ‘genetic responsibility’, MMR tumour testing seems less important in participants’ accounts compared to more definitive genetic testing. If facilitating genetic knowledge and responsibility are goals of genetic testing then developing appropriate consent procedures for MMR tumour testing is an important consideration. Further research is required to differentiate whether genetic counselling is a precondition for enacting genetic responsibility or whether intrinsic differences between types of testing make the concept less relevant.

Lynch syndrome-associated neoplasms: a discussion on histopathology and immunohistochemistry

It was a century ago that Warthin, a pathologist, first described the clinical condition now known as Lynch syndrome. One hundred years later, our understanding of this syndrome has advanced significantly. Much of the progress took place over the last 25 years and was marked by a series of interacting developments from the disciplines of clinical oncology, pathology, and molecular genetics, with each development serving to guide or enhance the next. The advancement of our understanding about the pathology of Lynch syndrome associated tumors exemplifies such intimate interplay among disciplines. Today, accumulative knowledge has enabled surgical pathologists to detect tumors that are likely to be associated with Lynch syndrome, and the pathologist is playing an increasingly more important role in the care of these patients. The pathologist's ability is afforded primarily by information gained from tumor histopathology and by DNA mismatch repair protein immunohistochemistry. It is therefore pertinent both for the pathologists to accurately ascertain this morphologic information, and for all that are involved in the care of these patients to thoroughly understand the implications of such information. This article provides an overview of the development of histopathology and immunohistochemistry in Lynch syndrome-associated tumors, particularly in colorectal and endometrial cancers, and outlines the issues and current status of these specific pathologic aspects in not only the major tumors but also those less commonly seen or only newly reported in Lynch syndrome patients.

Mismatch repair protein expression in colorectal cancer

INTRODUCTION

Alterations in at least six of the genes that encode proteins involved in the mismatch repair (MMR) system have been identified in either HNPCC or sporadic colon cancer. We aimed to analyse the proportion of patients with colorectal cancer with loss of immunostaining for MMR proteins in order to determine the feasibility of molecular screening for the loss of MMR proteins through the study of unselected patients with colorectal cancer.

METHODS

A group of 33 patients with colorectal cancer was randomly selected from the department of surgery bio-bank to determine the expression of MMR proteins in their FFPE tumour tissues using immunohistochemistry techniques. Changes in protein expression following transfection of colorectal tissues were observed in stained cells using Olympus BX60 microscope and image analySIS software.

RESULTS

Of the tissue specimens in which acceptable immunostaining was achieved, three samples showed loss of one or more of the MMR proteins. Both hMLH1 and hPMS2 proteins were not expressed in a 36 years old woman with cancer of the caecum. The expression of hMSH6 protein was undetermined in tumour tissues retrieved from a 61 years old man with cancer of the proximal colon. The third case was a 77 years old man with no documented family history of cancer, who had carcinoma of the rectum. He showed loss of hMLH1 expression in the tumour tissues.

CONCLUSIONS

Our findings and the previous reports pointed out the importance of molecular screening of patients with colorectal cancer for MSI using immunohistochemistry. This strategy managed to identify mutations in patients otherwise would not have been detected.

Determining the functional significance of mismatch repair gene missense variants using biochemical and cellular assays

With the discovery that the hereditary cancer susceptibility disease Lynch syndrome (LS) is caused by deleterious germline mutations in the DNA mismatch repair (MMR) genes nearly 20 years ago, genetic testing can now be used to diagnose this disorder in patients. A definitive diagnosis of LS can direct how clinicians manage the disease as well as prevent future cancers for the patient and their families. A challenge emerges, however, when a germline missense variant is identified in a MMR gene in a suspected LS patient. The significance of a single amino acid change in these large repair proteins is not immediately obvious resulting in them being designated variants of uncertain significance (VUS). One important strategy for resolving this uncertainty is to determine whether the variant results in a non-functional protein. The ability to reconstitute the MMR reaction in vitro has provided an important experimental tool for studying the functional consequences of VUS. However, beyond this repair assay, a number of other experimental methods have been developed that allow us to test the effect of a VUS on discrete biochemical steps or other aspects of MMR function. Here, we describe some of these assays along with the challenges of using such assays to determine the functional consequences of MMR VUS which, in turn, can provide valuable insight into their clinical significance. With increased gene sequencing in patients, the number of identified VUS has expanded dramatically exacerbating this problem for clinicians. However, basic science research laboratories around the world continue to expand our knowledge of the overall MMR molecular mechanism providing new opportunities to understand the functional significance, and therefore pathogenic significance, of VUS.

Simplified identification of Lynch syndrome: a prospective, multicenter study

BACKGROUND

Recommended strategies to screen for Lynch syndrome in colorectal cancer are not applied in daily practice and most of Lynch cases remain undiagnosed.

AIMS

We investigated in routine conditions a strategy that uses simplified clinical criteria plus detection of MisMatch Repair deficiency in tumours to identify Lynch carriers.

METHODS

Colorectal cancer patients that met at least one of three clinical criteria were included: (1) colorectal cancer before 50 years, (2) personal history of colorectal or endometrial cancer, (3) first-degree relative history of colorectal or endometrial cancer. All tumours underwent an MisMatch Repair test combining microsatellite instability analysis and MisMatch Repair immunohistochemistry. Patients with an MisMatch Repair-deficient tumour were offered germline testing.

RESULTS

Of the 307 patients fulfilling the clinical criteria, 46 (15%) had a MisMatch Repair-deficient tumour. Amongst them 27 were identified as Lynch carriers (20 with germline mutation: 12 MLH1, 7 MSH2, 1 MSH6; 7 highly suspected cases despite failure of genetic testing). The simplified clinical criteria selected a population whose MisMatch Repair-deficient status was highly predictive (59%) of Lynch syndrome.

CONCLUSION

This bio-clinical strategy based on simplified clinical criteria combined with an MisMatch Repair test efficiently detected LS cases and is easy to use in clinical practice, outside expert centres.

Immunohistochemical testing of conventional adenomas for loss of expression of mismatch repair proteins in Lynch syndrome mutation carriers: a case series from the Australasian site of the colon cancer family registry

Debate continues as to the usefulness of assessing adenomas for loss of mismatch repair protein expression to identify individuals with suspected Lynch syndrome. We tested 109 polyps from 69 proven mutation carriers (35 females and 34 males) belonging to 49 Lynch syndrome families. All polyps were tested by immunohistochemistry for four mismatch repair proteins MLH1, MSH2, MSH6 and PMS2. Detailed pathology review was performed by specialist gastrointestinal pathologists. The majority of polyps (86%) were conventional adenomas (n=94), with 65 tubular and 28 tubulovillous adenomas and a single villous adenoma. The remaining 15 lesions (14%) were serrated polyps. Overall, loss of mismatch repair expression was noted for 78/109 (72%) of polyps. Loss of mismatch repair expression was seen in 74 of 94 (79%) conventional adenomas, and 4 of 15 (27%) serrated polyps from mismatch repair gene mutation carriers. In all instances, loss of expression was consistent with the underlying germline mutation. Mismatch repair protein expression was lost in 27 of 29 adenomas with a villous component compared with 47 of 65 adenomas without this feature (93 vs 73%; P=0.028). A strong trend was observed for high-grade dysplasia. Mismatch repair deficiency was observed in 12 of 12 conventional adenomas with high-grade dysplasia compared with 60 of 79 with low-grade dysplasia (100 vs 76%; P=0.065). We were unable to demonstrate a significant association between conventional adenoma size or site and mismatch repair deficiency. All (4/4 or 100%) of the serrated polyps demonstrating mismatch repair deficiency were traditional serrated adenomas from a single family. Diagnostic testing of adenomas in suspected Lynch syndrome families is a useful alternative in cases where cancers are unavailable. The overwhelming majority of conventional adenomas from mutation carriers show loss of mismatch repair protein expression concordant with the underlying germline mutation.

Lynch syndrome: clinical, pathological, and genetic insights

INTRODUCTION

Lynch syndrome as the most common hereditary colorectal cancer syndrome and the most common cause of hereditary endometrial cancer is characterized by an autosomal dominant inheritance with a penetrance of 85-90%. The molecular genetic underlying mechanism is a mutation in one of the mismatch repair genes.

METHODS

In order to identify patients with Lynch syndrome, a nuclear family history should be ascertained and matched with the Amsterdam criteria. A different approach for identification is the adherence to Bethesda criteria and subsequent testing for microsatellite instability. In patients with unstable tumors as an indicator for mismatch repair deficiency, genetic counseling and mutation analysis are warranted. For families fulfilling the Amsterdam criteria, intensified screening is recommended, even if a pathogenic mutation is not identified.

RESULTS

Individuals from families with a proven pathogenic mutation that are tested negative are at normal population risk for cancers and may be dismissed from intensified surveillance. Prophylactic surgery in high-risk individuals without neoplasia is not generally recommended. At the time of a colon primary, however, extended surgery should be discussed in the light of a high rate of metachronous cancers. The worries of impairing functional results have now been evaluated in the light of quality of life in a large international cohort. Interestingly, extended (prophylactic) surgery does not lead to inferior quality of life with equal perioperative risks.

CONCLUSIONS

Therefore, taking the risk reduction into account, extended surgery at the time of the first colon primary should at least be discussed, if not recommended. Also, prophylactic hysterectomy and bilateral oophorectomy at the time of a colorectal primary should be recommended if family planning has been completed.

Analysis of DNA mismatch repair proteins expression and BRAF V600E mutation in a subset of early- and late-onset colorectal carcinoma patients in Mexico

BACKGROUND AND AIMS

A third of colorectal carcinomas (CRC) affect patients <50 years of age. Fifteen percent of CRC cases with microsatellite instability are due to inherited germ-line mutations in DNA mismatch repair genes. The rest have an epigenetic hypermethylation of the MLH1 promoter in whom the BRAF V600E mutation is a common hallmark. Immunohistochemistry helps to classify colorectal cancers with 100% specificity and 92% sensitivity. We undertook this study to determine if age is a risk factor for defective MMR protein expression and BRAF mutations in our population and to compare these results with the histopathological tumor features.

METHODS

Immunohistochemistry for MLH1 and MSH2 and RT-PCR BRAF V600E mutation was performed on tissue specimens from 57 patients <50 years of age. Data on age, gender, tumor location, histology, depth of infiltration, and the presence of metastatic lymph nodes were collected. Forty eight patients >50 years of age were used as a control group. A statistical analysis using ANOVA, χ(2), and Spearman's rho test were performed.

RESULTS

Absent MMR protein expression was more prevalent in patients <50 years of age. No BRAF V600E mutations were detected in either group. Medullary and mucinous types were more prevalent among young patients, whereas intestinal type was more frequent in older patients (p = 0.0008). No differences were found regarding clinicopathological stages between groups.

CONCLUSIONS

We found an association between young age and defective MMR expression. No V600E BRAF mutations were detected in either group.

Frequency of deletions of EPCAM (TACSTD1) in MSH2-associated Lynch syndrome cases

Lynch syndrome is an autosomal dominant cancer predisposition syndrome characterized by loss of function of DNA mismatch repair enzyme MLH1, MSH2, MSH6, or PMS2. Mutations in MLH1 and MSH2 account for ∼80% of the inherited cases. However, in up to 20% of cases suspected of having a germline mutation in MSH2 due to loss of MSH2 expression, a germline mutation is not identified. Recent studies have shown that some Lynch syndrome cases are due to 3' EPCAM/TACSTD1 deletions that subsequently lead to MSH2 promoter hypermethylation. In this study, we examined the frequency of this novel mechanism for MSH2 inactivation in cases recruited through the Colon Cancer Family Registry and from the Mayo Clinic Molecular Diagnostics Laboratory. From the combined cohort, 58 cases were selected in which immunohistochemical staining suggested a mutation in MSH2 or MSH6, but no mutations were identified on follow-up testing. Of these 58 cases, 11 demonstrated a deletion of EPCAM/TACSTD1. Of cases with a deletion, the methylation status of the MSH2 promoter was confirmed in tumor tissue using methylation-sensitive PCR primers. One case showed MSH2 promoter hypermethylation in the absence of a detectable EPCAM/TACSTD1 deletion. These results indicate that approximately 20% to 25% of cases suspected of having a mutation in MSH2 but in which a germline mutation is not detected, can be accounted for by germline deletions in EPCAM/TACSTD1. These data also suggest the presence of other alterations leading to MSH2 promoter hypermethylation.

A comparative study of quantitative immunohistochemistry and quantum dot immunohistochemistry for mutation carrier identification in Lynch syndrome

Aims

Lynch Syndrome is caused by mutations in DNA mismatch repair (MMR) genes. Mutation carrier identification is facilitated by immunohistochemical detection of the MMR proteins MHL1 and MSH2 in tumour tissue and is desirable as colonoscopic screening reduces mortality. However, protein detection by conventional immunohistochemistry (IHC) is subjective, and quantitative techniques are required. Quantum dots (QDs) are novel fluorescent labels that enable quantitative multiplex staining. This study compared their use with quantitative 3,3′-diaminobenzidine (DAB) IHC for the diagnosis of Lynch Syndrome.

Methods

Tumour sections from 36 mutation carriers and six controls were obtained. These were stained with DAB on an automated platform using antibodies against MLH1 and MSH2. Multiplex QD immunofluorescent staining of the sections was performed using antibodies against MLH1, MSH2 and smooth muscle actin (SMA). Multispectral analysis of the slides was performed. The staining intensity of DAB and QDs was measured in multiple colonic crypts, and the mean intensity scores calculated. Receiver operating characteristic (ROC) curves of staining performance for the identification of mutation carriers were evaluated.

Results

For quantitative DAB IHC, the area under the MLH1 ROC curve was 0.872 (95% CI 0.763 to 0.981), and the area under the MSH2 ROC curve was 0.832 (95% CI 0.704 to 0.960). For quantitative QD IHC, the area under the MLH1 ROC curve was 0.812 (95% CI 0.681 to 0.943), and the area under the MSH2 ROC curve was 0.598 (95% CI 0.418 to 0.777).

Conclusions

Despite the advantage of QD staining to enable several markers to be measured simultaneously, it is of lower utility than DAB IHC for the identification of MMR mutation carriers. Automated DAB IHC staining and quantitative slide analysis may enable high-throughput IHC.

Genetic counseling considerations in the evaluation of families for Lynch syndrome--a review

Lynch syndrome is the most common hereditary colorectal cancer syndrome and the most common cause of hereditary endometrial cancer. Identifying and evaluating families for Lynch syndrome is increasing in complexity due to the recognition that: family history-based clinical criteria lack sensitivity and specificity; genetic testing for Lynch syndrome continues to evolve as understanding of the molecular mechanisms underlying it evolves; and the Lynch syndrome phenotype encompasses multiple organ systems and demonstrates overlap with other hereditary cancer syndromes. This document is a summary of considerations when evaluating individuals and families for Lynch syndrome, including information on cancer risks, diagnostic criteria, tumor and genetic testing strategies, and the management of individuals with this condition.

Semiquantitative assessment of immunohistochemistry for mismatch repair proteins in Lynch syndrome

AIMS

To assess semiquantitative immunohistochemistry as used in the diagnosis of Lynch syndrome.

METHODS AND RESULTS

Tumour sections from 51 mutation carriers and 17 controls were stained with antibodies against MLH1, MSH2, MSH6 and PMS2. Intensity of immunoreactivity and percentage positivity were recorded on scales of 0-3 and 0-4, respectively. These scores were multiplied for a score of 0-12 per slide. Receiver-operator characteristic (ROC) curves of staining performance for the identification of mutation carriers were evaluated, and optimum cut-offs calculated. The area under the MLH1 ROC curve was 0.981 [95% confidence interval (CI) 0.952, 1.000]. The area under the MSH2 ROC curve was 0.899 (95% CI 0.796, 1.000). For MLH1 staining, a score<or=4 gives a sensitivity of 100.0% (95% CI 84.0, 100.0) and a specificity of 91.5% (95% CI 79.6, 97.6) for identifying MLH1 mutation carriers. For MSH2 staining, a score<or=4 gives a sensitivity of 87.5% (95% CI 61.7, 98.4) and specificity of 88.5% (95% CI 76.5, 95.6) for identifying MSH2 mutation carriers.

CONCLUSIONS

This study supports a semiquantitative slide assessment method. Protein expression may occur in the context of known pathogenic mutations, a potential pitfall in the screening process.

Application of molecular diagnostics for the detection of Lynch syndrome

Lynch syndrome (LS), or hereditary nonpolyposis colorectal cancer, is the most common hereditary colorectal cancer (CRC) syndrome, accounting for approximately 2-5% of all newly diagnosed cases of CRC. Patients with LS have an increased lifetime risk of colorectal (52.2% in women and 68.7% in men) and endometrial cancer (15-70%), as well as certain extra-colonic cancers. Germline mutations in one of several DNA mismatch repair genes underlie LS. Molecular testing has emerged as an indispensable strategy for the diagnosis of LS. The diagnostic work-up of at-risk individuals includes a careful family history evaluation, microsatellite instability, immunohistochemistry and germline DNA analysis. A positive test result can guide clinicians in formulating the appropriate screening, surveillance and management strategies. However, because of the absence of an overt phenotype, such as a diffuse polyposis, it is not always straightforward to recognize LS clinically.

Interobserver variability in the evaluation of mismatch repair protein immunostaining

Immunohistochemical staining for mismatch repair proteins has during recent years been established as a routine analysis in many pathology laboratories with the aim to identify tumors linked to the hereditary nonpolyposis colorectal cancer syndrome. Despite widespread application, data on reliability are lacking. We therefore evaluated interobserver variability among 6 pathologists, 3 experienced gastrointestinal pathologists and 3 residents. In total, 225 immunohistochemically stained colorectal cancers were evaluated as having normal, weak, loss of, or nonevaluable mismatch repair protein staining. Full consensus was achieved in 51% of the stainings for MLH1, 61% for PMS2, 83% for MSH2, and 45% for MSH6. Weak stainings were the main cause of reduced consensus, whereas contradictory evaluations with normal as well as loss of staining were reported in 2% to 6% of the tumors. Interobserver variability was considerable, though experienced pathologists and residents reached the same level of consensus. Because results from immunohistochemical mismatch repair protein stainings are used for decisions on mutation analysis and as an aid in the interpretation of gene variants of unknown significance in hereditary nonpolyposis colorectal cancer, the interobserver variability identified highlights the need for quality assessment programs, including guidelines for classification of different expression patterns.

Absence of hMLH1 or hMSH2 expression as a stage-dependent prognostic factor in sporadic colorectal cancers

BACKGROUND

The predictive role of mismatch repair (MMR) status for survival after sporadic colorectal cancer remains a point of controversy. This study was designed to test the prognostic value of MMR status in sporadic colorectal cancers.

METHODS

The study included 318 patients with sporadic colorectal cancer who underwent primary tumor resection. MMR status was determined by the immunohistochemical analysis of hMLH1 and hMSH2 expression.

RESULTS

Thirty-six carcinomas (11.3%) showed abnormal MMR protein expression (22 hMLH1 negative and 14 hMSH2 negative) and were classified as MMR-defective tumors. An MMR defect was strongly associated with a reduced likelihood of lymph node (odds ratio, 0.32; 95% confidence interval [95% CI], 0.13-0.75) or distant organ metastases at diagnosis (odds ratio, 0.07; 95% CI, 0.01-0.62), independent of the clinicopathological features. Overall survival was significantly better in patients with MMR-defective tumors than in those with MMR-intact tumors (P = 0.013). In the subgroup analysis by stage, adjusted for other potential confounding variables, MMR status was not a statistically significant prognostic factor in stage I and II patients, while the MMR defect predicted a significantly better overall survival in stage III and IV patients (adjusted hazard ratio, 0.23; 95% CI, 0.06-0.97; P = 0.045).

CONCLUSIONS

At initial diagnosis, metastases were found at lower rates in MMR-defective tumors. MMR status may be a stage-dependent prognostic factor in patients with sporadic colorectal cancer.

Colorectal cancer in Iran: immunohistochemical profiles of four mismatch repair proteins

PURPOSE

The aim of the present study was to determine the profile of mismatch repair (MMR) defects in Iranian colorectal cancer patients by using immunohistochemical staining for products of four MMR genes: MLH1, MSH2, PMS2, and MSH6.

METHODS

Tissue samples of 343 patients were immunostained for MLH1, MSH2, PMS2, and MSH6. Clinical and family history and survival data were compared between normal and abnormal staining patterns.

RESULTS

Fourteen percent of the patients had abnormal nuclear staining for MMR proteins. MLH1 was absent in four, MLH1/PMS2 in 15, PMS2 in five, MSH2 in 12, and MSH2/MSH6 in 12 patients. These tumors were more proximal, had a nonsignificant better survival, and were more associated with positive family history. Estimation of this study of prevalence of hereditary nonpolyposis colorectal cancer in Iran was 5.5% of the total colorectal cancers.

CONCLUSIONS

Along with the recommendations of the National Institute of Cancer, we recommend immunohistochemistry staining for MLH1, MSH2, PMS2, and MSH6 for determining the eligibility of patients for mutation analysis of MMR genes.

Genetic testing for hereditary colorectal cancer

This article focuses on genetic testing for hereditary colorectal cancer syndromes. Genetic testing is now available in North America for all of the known hereditary colorectal cancer genes. In addition, most of these tests have improved significantly in the past few years with the inclusion of techniques to detect large rearrangements. As a result, clinicians are in a better position than ever to help families with these syndromes to identify the underlying genetic cause. This identification will ensure that they receive appropriate management, and will enable their relatives to determine their precise risks and to tailor their cancer surveillance.

A review on the molecular diagnostics of Lynch syndrome: a central role for the pathology laboratory

Lynch syndrome (LS) is caused by mutations in mismatch repair genes and is characterized by a high cumulative risk for the development of mainly colorectal carcinoma and endometrial carcinoma. Early detection of LS is important since surveillance can reduce morbidity and mortality. However, the diagnosis of LS is complicated by the absence of a pre-morbid phenotype and germline mutation analysis is expensive and time consuming. Therefore it is standard practice to precede germline mutation analysis by a molecular diagnostic work-up of tumours, guided by clinical and pathological criteria, to select patients for germline mutation analysis. In this review we address these molecular analyses, the central role for the pathologist in the selection of patients for germline diagnostics of LS, as well as the molecular basis of LS.

Immunohistochemistry as first-line screening for detecting colorectal cancer patients at risk for hereditary nonpolyposis colorectal cancer syndrome: a 2-antibody panel may be as predictive as a 4-antibody panel

The utility of immunohistochemical detection of DNA mismatch repair proteins in screening colorectal cancer for hereditary nonpolyposis colorectal cancer (HNPCC) is being widely investigated. Currently, in both research and clinical settings, a 4-antibody panel that includes the 4 most commonly affected proteins (MLH1, MSH2, MSH6, and PMS2) is being used generally. On the basis of the biochemical properties of these proteins, we hypothesized that a 2-antibody panel, comprising MSH6 and PMS2, would be sufficient to detect abnormalities in all 4 proteins. We tested this hypothesis on a series of 232 colorectal carcinoma samples derived from 2 patient cohorts: (1) a prospectively accrued series of patients who were judged to carry a higher-than-average risk for HNPCC based on the revised Bethesda guidelines (n=190); and (2) a retrospective series of patients who were 40 years of age or younger (n=42). Immunohistochemical stains were regarded as negative (protein lost), when there was no nuclear labeling in tumor cells (with positive internal control). Overall, 70 of the 232 tumors demonstrated loss of at least one protein. The most common abnormality was concurrent loss of MLH1 and PMS2 (observed in 17% of the cases), followed by concurrent loss of MSH2 and MSH6 (6%). All MLH1 and MSH2-abnormal cases were also abnormal for PMS2 and MSH6, respectively, whereas 9 of 50 (18%) PMS2 and 6 of 20 (30%) MSH6-abnormal cases showed only isolated loss of PMS2 or MSH6 (with normal staining for MLH1 and MSH2). As such, our findings provide evidence that a 2-antibody panel (PMS2 and MSH6) is as effective as the current 4-antibody panel in detecting DNA mismatch repair protein abnormalities. Such a cost-effective approach carries significant implication, as immunohistochemistry is being widely used as first-line screening for HNPCC.

Colorectal cancer due to deficiency in DNA mismatch repair function: a review

Lynch syndrome (LS) is an autosomal dominant cancer predisposition syndrome attributable to deleterious germline mutations in mismatch repair (MMR) genes. The syndrome is typified by early-onset, frequently right-sided colorectal cancers (CRCs) with characteristic histologic features and tendency for multiplicity and an increased risk for extracolonic tumors at particular sites; it accounts for 1% to 5% of CRC. Deficient mismatch repair (dMMR) function manifests as immunohistochemically detectable absence of one or more MMR proteins and microsatellite instability (MSI). Approximately 15% of sporadic, noninherited CRC are characterized by high-level MSI, nearly always owing to transcriptional silencing of MLH1; these sporadic and LS cases exhibit considerable phenotypic overlap. Identification of CRC with dMMR is desirable to identify LS and because MSI status is prognostic and potentially predictive. This review will discuss the history of LS, the principles of MMR and MSI, the clinicopathologic features of LS-associated and sporadic high-level MSI CRC, the fundamentals of clinical testing for dMMR CRC, and the results of the Columbus-area Lynch syndrome study. We conclude with our approach to population-based LS screening based on institutional experience with nearly 2000 cases.

Deficient DNA mismatch repair is common in Lynch syndrome-associated colorectal adenomas

Lynch syndrome is caused by germline mutations in DNA mismatch repair (MMR) genes. Both microsatellite instability (MSI) testing and immunohistochemical analyses (IHC) of colon cancers are valuable diagnostic strategies for Lynch syndrome. We sought to determine whether these markers of MMR deficiency were also detectable in pre-cancerous colorectal adenomas. Fifteen subjects with a germline MMR gene mutation who had 44 adenomas removed during surveillance colonoscopy were identified. MSI testing and IHC for MLH1, MSH2, and MSH6 were performed. MSI was detected in 23 adenomas. There was a significant association between MSI and high-grade dysplasia (P = 0.006) and distal location (P = 0.0008). Loss of MMR protein by IHC was detected in 31 adenomas. A significant association was observed between loss of staining by IHC and high-grade dysplasia (P = 0.04). Among the 40 adenomas in which both MSI tests and IHC were performed, the presence of a germline mutation correlated with an abnormal MSI result in 58% of cases, an abnormal IHC result in 70% of cases, and either an abnormal MSI or IHC result in 73% of cases. The combination of MSI and IHC testing in colorectal adenomas is a sensitive screen for the detection of Lynch syndrome and may be particularly useful when Lynch syndrome is suspected and adenomatous polyps are the only tissues available for analysis.

Differential up-regulation of erythropoietin and its receptor in benign and malignant prostatic tissue

PURPOSE

To investigate differential up-regulation of erythropoietin and its receptor in benign and malignant prostatic tissue.

MATERIALS AND METHODS

An immunohistochemical analysis of EPO and EPOR expression was performed on 30 cases of prostate carcinoma (PCa) with 16 high-grade prostate intraepithelial neoplasia (PIN), 50 cases of benign prostatic hyperplasia (BPH) lesions, and 30 normal prostatic tissue samples as control.

RESULTS

Over-expression of EPOR was only shown in PCa and high-grade PIN tissue but over-expression of EPO was also shown in BPH tissue. There was significant relationship between EPO and EPOR score in BPH, high-grade PIN, and PCa but no association between EPOR or EPO score and Gleason score in PCa.

CONCLUSIONS

Up-regulation of EPOR has a more important role in comparison with EPO in prostate carcinogenesis. Differential over-expression of EPOR and EPO in benign and malignant prostatic tissue is ascribed to different mechanisms involved in up-regulation between EPO and EPOR.

Feasibility of screening for Lynch syndrome among patients with colorectal cancer

PURPOSE

Identifying individuals with Lynch syndrome (LS) is highly beneficial. However, it is unclear whether microsatellite instability (MSI) or immunohistochemistry (IHC) should be used as the screening test and whether screening should target all patients with colorectal cancer (CRC) or those in high-risk subgroups.

PATIENTS AND METHODS

MSI testing and IHC for the four mismatch repair proteins was performed on 500 tumors from unselected patients with CRC. If either MSI or IHC was abnormal, complete mutation analysis for the mismatch repair genes was performed.

RESULTS

Among the 500 patients, 18 patients (3.6%) had LS. All 18 patients detected with LS (100%) had MSI-high tumors; 17 (94%) of 18 patients with LS were correctly predicted by IHC. Of the 18 probands, only eight patients (44%) were diagnosed at age younger than 50 years, and only 13 patients (72%) met the revised Bethesda guidelines. When these results were added to data on 1,066 previously studied patients, the entire study cohort (N = 1,566) showed an overall prevalence of 44 of 1,566 patients (2.8%; 95% CI, 2.1% to 3.8%) for LS. For each proband, on average, three additional family members carried MMR mutations.

CONCLUSION

One of every 35 patients with CRC has LS, and each has at least three relatives with LS; all of whom can benefit from increased cancer surveillance. For screening, IHC is almost equally sensitive as MSI, but IHC is more readily available and helps to direct gene testing. Limiting tumor analysis to patients who fulfill Bethesda criteria would fail to identify 28% (or one in four) cases of LS.

Reduced mRNA expression in paraffin-embedded tissue identifies MLH1- and MSH2-deficient colorectal tumours and potential mutation carriers

Based on the principle of nonsense-mediated mRNA decay, we sought to identify MLH1 or MSH2-deficient colorectal tumours through relative quantification of mRNA expression with real-time PCR (RT-PCR) analysis. MLH1 and MSH2 mRNAs were almost equally expressed as defined by MLH1 to MSH2 transcript ratio (mean 1.41) in microsatellite stable, mismatch repair (MMR) proficient tumours (n = 16). A close correlation between loss of protein expression and MMR-mRNA levels was found in highly microsatellite instable (MSI-H) tumours deficient of MLH1 or MSH2. MLH1/MSH2 ratio was low in 11 sporadic and nine hereditary MLH1-deficient carcinomas (mean 0.51), whereas the ratio was high in 17 MSH2-deficient hereditary non-polyposis colorectal cancer (HNPCC) associated carcinomas (mean 6.8). Notably, in the normal tissues of HNPCC patients with MSH2 mutations, the MLH1/MSH2 transcript ratios were significantly elevated (ratio > 2.0) as compared to the ratios of normal mucosa in patients with MMR-proficient tumours (27 of 32 ratio < 2.0; p = 0.00113). Analysis of B-lymphocytes of HNPCC patients with proven MMR gene mutation confirmed these findings. In conclusion, RT-PCR allows relative quantification of MMR gene mRNA expression in formalin-fixed and paraffin-embedded tissue. Furthermore, this approach enables quantification of haploinsufficiency due to nonsense-mediated mRNA decay in normal tissue and B-lymphocytes from patients carrying MSH2 germline mutations and may be useful for identification of asymptomatic carriers of pathogenic germline mutations.

Review article: Detection and management of hereditary non-polyposis colorectal cancer (Lynch syndrome)

BACKGROUND

The most common hereditary colorectal cancer syndrome is hereditary non-polyposis colorectal cancer (HNPCC), also known as Lynch syndrome. Diagnosis of this syndrome is difficult, because of lack of specific diagnostic features.

AIM

To discuss the diagnostic criteria and laboratory work up for HNPCC. Furthermore, surveillance programs for HNPCC and treatment of HNPCC associated colorectal cancer are discussed.

RESULTS

Current diagnostic criteria, including the Amsterdam II and Bethesda criteria, are suboptimal for the detection of HNPCC. Molecular screening by microsatellite instability (MSI) and immunohistochemistry (IHC) is useful in the diagnosis of HNPCC. Both techniques have a higher sensitivity compared to the Amsterdam II and Bethesda criteria. A combination of both MSI and IHC provides the most optimal selection for mutation analysis. After identification of a mutation in an affected individual, genetic counselling and presymptomatic mutation analysis should be offered to relatives. Furthermore, colonoscopic surveillance should be performed in proven mutation carriers.

CONCLUSIONS

Identification of HNPCC is a clinical challenge involving many clinicians. Identification of persons at risk can be achieved by a combination of a detailed family history, testing with molecular and mutation analysis.

Hereditary nonpolyposis colorectal cancer (Lynch Syndrome) in Argentina: report from a referral hospital register

PURPOSE

The first Argentine experience with epidemiologic, molecular, and genetic counseling data is reported.

METHODS

We analyzed 43 families fulfilling Amsterdam criteria identified from a prospective database with data from 779 relatives.

RESULTS

Eleven families (25.6 percent) presented as Lynch I, 29 (67.4 percent) as Lynch II, and 3 (7 percent) as Muir-Torre syndrome. Among the 306 affected members, 197 cases of colorectal cancer were identified (mean age at diagnosis, 52.1 (range, 21-90) years). The most frequent extracolonic tumors were gastric adenocarcinoma in males and endometrium adenocarcinoma in females. A high incidence of breast cancer was observed (16 cases among 155 females, crude rate: 11,594.20/100,000). Twenty-seven patients (8.8 percent) developed more than one tumor. These patients were younger than those with only one tumor (45 vs. 51 years; P = 0.001). In 5 of 11 patients who underwent molecular sequencing, a pathologic mutation was found. A novel C deletion at 1910 nucleotide, codon 637, exon 12 of MSH2 gene was identified in a family with a strong aggregation of breast cancer with lack of MSH2 immunohistochemical staining. For 78.2 percent of counseled individuals, this session represented the first time they received information, and 73.9 percent stated that their physicians were unaware of their family background.

CONCLUSIONS

Argentine families presented a high incidence of stomach cancer. The elevated incidence of breast cancer and its association with a novel hMSH2 mutation bring to consideration the inclusion of this malignancy as part of the syndrome. A lack of awareness by both physicians and persons at risk was observed.

Upregulation of erythropoietin receptor in human prostate carcinoma and high-grade prostatic intraepithelial neoplasia

The aim of the present study was to investigate the differential expression of erythropoietin receptor (EPOR) in prostate carcinoma (PCa), high-grade prostatic intraepithelial neoplasia (PIN), prostatic hyperplasia (BPH) lesions and normal prostatic tissues by immunohistochemistry; and to test the hypothesis that upregulation of EPOR is a specific event for prostate carcinogenesis. An immunohistochemical analysis of EPOR was performed on 30 PCa, 50 BPH with/without inflammation lesions and 30 normal prostatic tissue samples. EPOR staining was quantitated and classified into normal expression and overexpression. Totally 16 high-grade PIN lesions were found in this study. Overexpression of EPOR was shown only in PCa and high-grade PIN. Statistical analysis demonstrated that higher median EPOR staining score of PCa and high-grade PIN in comparison with BPH (P < 0.05) and higher median EPOR staining score of PCa compared with high-grade PIN (P < 0.05). Our data demonstrate that upregulation of EPOR is not uncommon for PCa and upregulated EPOR in high-grade PIN suggests upregulation of EPOR is an early event for prostate carcinogenesis. The role of upregulated EPOR and possibly enhanced EPOR signaling in prostate carcinogenesis warrants further studying.

Pathology of the hereditary colorectal carcinoma

Positive familial history (first or second degree relative) for colorectal carcinoma (CRC) can be found in approximately 30% of all newly diagnosed cases, but less than 5% will be due to a defined genetic category of hereditary CRC. Pathologic examination of the biopsy or resection specimen can help in identification of unsuspected cases of certain forms of hereditary CRC due to the characteristic morphologic findings. Additional immunohistochemical and molecular studies can then provide a definitive diagnosis. The most common form of hereditary CRC is Lynch syndrome (hereditary non-polyposis colorectal cancer, HNPCC) which is characterized by proximally located tumors frequently showing mucinous and medullary type histologic features. The syndrome results from a germline mutation in genes for mismatch repair (MMR) proteins leading to insufficient DNA repair and development of tumors characterized by high levels of instability in short tandem repeat DNA sequences (microsatellites) or "microsatellite instability-high" (MSI-H). The presence of intra-epithelial lymphocytes is single most helpful morphologic feature in identification of CRC caused by deficiency in MMR proteins, for which MSI-H status is a good marker but morphologic features and MSI-H do not differentiate tumors caused by germline mutations in one of the MMR genes (Lynch syndrome) from sporadic CRC due to inactivation of MLH-1 through promoter methylation. Hereditary CRC may also arise in various familial polyposis syndromes which include familial adenomatous polyposis (FAP), attenuated FAP and other multiple adenomas syndromes as well as various hamartomatous polyposis syndromes. All of these rare conditions have characteristic clinical presentation and histopathologic features of polyps and most of them have defined genetic abnormality. Furthermore, due to the germline nature of mutations in these syndromes, various extracolonic manifestations may be the first sign of the disease and knowledge of such associations can greatly improve the quality of care for these patients. The role of pathologist is to recognize these characteristics and initiate appropriate follow up with clinicians and genetic counselors.

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.

Reduced Pms2 expression in non-neoplastic flat mucosa from patients with colon cancer correlates with reduced apoptosis competence

Pms2 protein is a component of the DNA mismatch repair complex responsible both for post-replication correction of DNA nucleotide mispairs and for early steps in apoptosis. Germline mutations in DNA mismatch repair genes give rise to hereditary non-polyposis colon cancer, which accounts for about 4% of colon cancers. However, little is known about the expression of mismatch repair proteins in relation to sporadic colon cancer, which accounts for the great majority of colon cancers. Multiple samples were taken from the non-neoplastic flat mucosa of colon resections from patients with no colonic neoplasia, a tubulovillous adenoma, or an adenocarcinoma. Expression of Pms2 was assessed using semiquantitative immunohistochemistry. Apoptosis was assessed in polychrome-stained epoxy sections using morphologic criteria. Samples from patients without colonic neoplasia had moderate to strong staining for Pms2 in cell nuclei at the base of crypts, while samples from 2 of the 3 colons with a tubulovillous adenoma, and from 6 of the 10 colons with adenocarcinomas, showed reduced Pms2 expression. Samples from patients with an adenocarcinoma that had reduced Pms2 expression also exhibited reduced apoptosis capability in nearby tissue samples, evidenced when this paired tissue was stressed ex vivo with bile acid. Reduced Pms2 expression in the colonic mucosa may be an early step in progression to colon cancer. This reduction may cause decreased mismatch repair, increased genetic instability, and/or reduced apoptotic capability. Immunohistochemical determination of reduced Pms2 expression, upon further testing, may prove to be a promising early biomarker of risk of progression to malignancy.

Mismatch Repair Status Is a Predictive Factor of Tumour Response to 5-Fluorouracil and Irinotecan Chemotherapy in Patients with Advanced Colorectal Cancer

BACKGROUND AND AIMS

To determine the association between DNA mismatch repair (MMR) protein expression and response to chemotherapy in patients with advanced colorectal cancer (CRC).

METHODS

Using immunohistochemistry, tumour expression of 2 MMR genes, hMLH1 and hMSH2, was assessed in 86 patients with advanced CRC, who were treated with either irinotecan alone or in combination with 5-flurouracil/folinic acid.

RESULTS

Weak/negative staining in the tumours was associated with the presence of metastases at diagnosis (p = 0.026) and with the time for metastases to appear (p = 0.0001). An objective response to treatment was observed in 32/56 (57%) patients who had tumours with negative/weak MMR protein expression (p = 0.001), compared to 17% of patients with tumours with moderate/strong expression. Those who had tumours with weak/absent expression of either hMLH1 or hMSH2 who received the combination therapy were more likely to show an objective response (p = 0.0001).

CONCLUSION

Advanced CRC patients whose tumours have deficient MMR demonstrate a shorter time to metastasis than those with normal hMLH1/hMSH2 expression. Patients with MMR-deficient tumours are also more likely to benefit from combination chemotherapy (irinotecan plus 5-flurouracil/folinic acid).

Variability and inequity in testing of somatic tissue for hereditary cancer: a survey of UK clinical practice

A growing body of literature demonstrates the benefits of molecular pathological investigations of tumour material in the identification of individuals with hereditary non-polyposis colorectal cancer and debates the best detection strategies. This testing is novel as it is the first widespread use of somatic tissue testing to inform genetic analysis and requires the co-ordination of both histopathology and molecular genetics laboratories. However, the clinical use and experience of microsatellite instability (MSI) testing and immunohistochemical analysis have not been reported. A respondent from every cancer genetics centre in the UK (n= 24, response rate 100%) and laboratory performing MSI testing (n= 5, response rate 100%) was interviewed by telephone to ascertain test availability, testing methods, eligibility criteria and post-test management. Twenty centres (83%) offer eligible clients at least one form of tumour testing, and all use tumour testing to determine who should have access to germ line genetic testing. However, no two laboratories used the same testing methods, seven different testing strategies were applied and there was considerable variation in eligibility criteria. The implications of these variations are considered, and recommendations for the development of a consistent service for testing of somatic tissue offered.

Pathogenicity of MSH2 missense mutations is typically associated with impaired repair capability of the mutated protein

BACKGROUND & AIMS

Inherited deleterious mutations in mismatch repair genes MLH1, MSH2, and MSH6 predispose to hereditary nonpolyposis colorectal cancer. A major diagnostic challenge is the difficulty in evaluating the pathogenicity of missense mutations. Previously we showed that most missense variants in MSH6 do not impair MMR capability and are associated with no or low cancer susceptibility, whereas in MLH1, functional studies distinguished nontruncating mutations with severe defects from those not or slightly impaired in protein expression or function. The present study was undertaken to evaluate the pathogenicity of inherited missense mutations in MSH2.

METHODS

Fifteen mutated MSH2 proteins including 14 amino acid substitutions and one in-frame deletion were tested for expression/stability, MSH2/MSH6 interaction, and repair efficiency. The genetic and biochemical data were correlated with the clinical data. Comparative sequence analysis was performed to assess the value of sequence homology as a tool for predicting functional results.

RESULTS

None of the studied MSH2 mutations destroyed the protein or abolished MSH2/MSH6 interaction, whereas 12 mutations impaired the repair capability of the protein. Comparative sequence analysis correctly predicted functional studies for 13 of 14 amino acid substitutions.

CONCLUSIONS

Interpretation was pathogenic for 12, nonpathogenic for 2, and contradictory for 1 mutation. The pathogenicity could not be distinguished unambiguously by phenotypic characteristics, although correlation between the absence of staining for MSH2 and pathogenicity of the missense mutation was notable. Unlike in MSH6 and MLH1, the pathogenicity of missense mutations in MSH2 was always associated with impaired repair capability of the mutated protein.

Prevalence of the mismatch-repair-deficient phenotype in colonic adenomas arising in HNPCC patients: results of a 5-year follow-up study

In hereditary nonpolyposis colorectal cancer (HNPCC) syndrome, more than 90% of the carcinomas show microsatellite instability (MSI) due to a loss of mismatch repair (MMR) function. Although adenomas are very common in HNPCC and demonstrate an accelerated adenoma-carcinoma sequence, data about the prevalence and development of MSI in these early neoplastic lesions are lacking. To determine whether MSI and loss of MMR-protein expression are already present in early stages of tumorigenesis and could therefore be used as a screening tool to identify HNPCC patients before they develop an invasive carcinoma, we analyzed 71 adenomas of 36 HNPCC patients during a 5-year follow-up study. These 36 patients were part of a cohort of 122 HNPCC patients who were investigated at the Institute of Pathology, Klinikum Kassel, as part of the multicentric German HNPCC Consortium, which currently serves more than 2,880 registered families. The diagnosis of HNPCC was based either on the detection of a pathogenic germline mutation in the MSH2, MLH1, or MSH6 genes or in cases where a pathogenic mutation was not found; diagnosis of HNPCC was made, because all patients fulfilled the Amsterdam or Bethesda criteria and revealed a high degree of MSI (MSI-H) as well as loss of one of the MMR proteins by IHC in the cancer tissue. We found that most adenomas (58/71) were MSI-H and had loss of MMR-protein expression. Of the 71 adenomas, 3 were MSI-H with expression of all MMR proteins, and 3 out of 71 displayed loss of a MMR protein with the microsatellites being classified as microsatellite stable (MSS). However, 7 of the 31 adenomas that were located more than 5 cm away from the carcinoma revealed an MSS status (n=6) or low in MSI (n=1) and expressed all MMR proteins. In summary, a significant percentage of HNPCC-associated adenomas (7/31, 22.6%) developing at a distance of more than 5 cm from the corresponding carcinoma did not show the MSI-H MMR-deficient phenotype and expressed all MMR genes. To our knowledge, this is the first study that shows that in most HNPCC patients, the mutator pathway is already detectable in adenomas, but MMR-proficient adenomas can also be found. Therefore, screening for MMR deficiency should not be applied routinely in adenomas with the goal to identify HNPCC patients.

Identification of germline MLH1 alterations in familial prostate cancer

Several linkage and loss of heterozygosity (LOH) analyses suggest that the region 3p21-p26, which is a chromosomal location of MLH1, could harbour a susceptibility gene for prostate cancer (PRCA). Furthermore, in a recent candidate single nucleotide polymorphism (SNP) analysis the I219V variation of the MLH1 gene was associated with PRCA. Microsatellite instability (MSI) and germ-line MLH1 mutations were originally demonstrated in hereditary non-polyposis colorectal cancer (HNPCC) but MSI and loss of MLH1 function have also been detected in PRCA. To assess the contribution of MLH1 germline mutations to the development of PRCA in Finland different approaches were used. First, the samples from 11 PRCA-colon cancer patients were screened for MLH1, MSH2 and MSH6 protein expression by immunohistochemistry (IHC). IHC revealed one patient with a putative MLH1 aberration and sequencing of this sample revealed five sequence variants including two missense variants P434L and I219V. Second, the samples from Finnish hereditary prostate cancer (HPC) families were used for the screening of MLH1 mutations which produced twelve MLH1 sequence variants including two missense mutations, I219V, as in the PRCA-colon cancer patient, and V647M. P434L and V647 were both novel, rare variants. Carrier frequencies of the I219V mutation were compared between hereditary prostate cancer (HPC) patients, unselected PRCA cases, patients with benign prostate hyperplasia and controls, but no differences between the sample groups were found. P434L was not present in this study population and V647M was a very rare variant found only in one HPC family. According to the present results, MLH1 does not have a major role in PRCA causation in Finland.

The added value of PMS2 immunostaining in the diagnosis of hereditary nonpolyposis colorectal cancer

Identification and characterization of the genetic background in patients with the hereditary nonpolyposis colorectal cancer (HNPCC) syndrome is important since control programmes can in a cost-effective manner prevent cancer development in high-risk individuals. HNPCC is caused by germline mismatch repair (MMR) gene mutations and the genetic analysis of HNPCC therefore includes assessment of microsatellite instability (MSI) and immunohistochemical MMR protein expression in the tumor tissue. MSI is found in >95% of the HNPCC-associated tumors and immunostaining using antibodies against the MMR proteins MLH1, MSH2, and MSH6 has been found to correctly pinpoint the affected gene in about 90% of the cases. The PMS2 antibody was the most recently developed and we have in a clinical material assessed the added value of PMS2 immunostaining in 213 patients with suspected hereditary colorectal cancer. All 119 MSS tumors showed retained expression for all four antibodies and PMS2 did thus not identify any underlying MMR defect in these cases. However, PMS2 immunostaining contributed to the characterization of the MMR defect in a subset of the MSI tumors. Concomitant loss of MLH1 and PMS2, which functionally interact in the MutLalpha complex, was found in 98% of the tumors from patients with germline MLH1 mutations. Among the 12 MSI-high tumors with retained expression of MLH1, MSH2 and MSH6, 8 tumors showed loss of PMS2 staining, and mutations in MLH1 were identified in 2 and mutations in PMS2 in 3 of these individuals. In summary, isolated loss of PMS2 was found in 8% of the MSI-high tumors in our series, including 8/12 previously unexplained MSI-high tumors, in which mutations either in MLH1 or in PMS2 were identified in five cases.