The genetics of HNPCC: application to diagnosis and screening

Hereditary Colorectal Cancer: State of the Art in Lynch Syndrome

Hereditary non-polyposis colorectal cancer is also known as Lynch syndrome. Lynch syndrome is associated with pathogenetic variants in one of the mismatch repair (MMR) genes. In addition to colorectal cancer, the inefficiency of the MMR system leads to a greater predisposition to cancer of the endometrium and other cancers of the abdominal sphere. Molecular diagnosis is performed to identify pathogenetic variants in MMR genes. However, for many patients with clinically suspected Lynch syndrome, it is not possible to identify a pathogenic variant in MMR genes. Molecular diagnosis is essential for referring patients to specific surveillance to prevent the development of tumors related to Lynch syndrome. This review summarizes the main aspects of Lynch syndrome and recent advances in the field and, in particular, emphasizes the factors that can lead to the loss of expression of MMR genes.

Evaluation of Concordance Between Deficient Mismatch Repair and Microsatellite Instability Testing and Their Association with Clinicopathological Features in Colorectal Cancer

Background

Microsatellite instability (MSI) is one of the most important molecular characteristics of colorectal cancer (CRC), which mainly results from defective DNA mismatch repair (MMR). This study was performed to investigate the concordance between deficient MMR and MSI testing, and to evaluate the association of these two results with clinicopathological characteristics in Chinese CRC patients.

Methods

A total of 738 CRC patients were included. Tumor tissues and paired peripheral blood specimens were obtained. Screening for MMR was investigated using immunohistochemical (IHC) technique, and multiple polymerase chain reaction-capillary electrophoresis (PCR-CE) method was performed to detect the MSI status. All clinicopathological data, immunohistochemistry and microsatellite instability analyses were then statistically analyzed.

Results

Of the 738 (17.75%) CRC patients, 131 expressed as deficient mismatch repair (dMMR) status, and postmeiotic segregation increased 2 (PMS2) deficiency was the most frequent deficiency among these four MMR proteins. MSI-high (MSI-H) status occurred in 74 of the 738 (10.03%) CRC patients, 55 of whom showed instability at all six mononucleotides repeat markers. dMMR was significantly associated with MSI-H and moderate concordance was observed between IHC and PCR-CE in evaluating deficient MMR/MSI through Kappa test. Statistically, dMMR was significantly associated with younger age, right-sided colon and poor differentiation. MSI-H was associated with younger age, right-sided colon, poor differentiation, mucinous type and tumor, node, metastasis (TNM) stage II.

Conclusion

A moderate concordance between deficient MMR and MSI testing indicates that both IHC and PCR-CE methods should be routinely tested to provide reliable data for clinical treatment decisions.

[Hereditary colon cancer in Lynch syndrome/HNPCC syndrome in Germany]

BACKGROUND

Hereditary nonpolyposis colorectal cancer (Lynch/HNPCC syndrome) is based on a germline mutation inducing increased occurrence of colorectal cancer and extracolonic carcinomas in young age. The German HNPCC consortium aims to increase awareness for detection of hereditary colon cancer among patients and physicians.

OBJECTIVES

Reliable detection of HNPCC patients is based on a thorough documentation of patients' medical history and on further diagnostics delivered by human genetics and surgical pathology. This manuscript presents a standardized diagnostic concept.

METHODS

Relevant literature is reviewed and discussed and diagnostic parameters are outlined. In addition, operating figures of the German HNPCC consortium are presented.

RESULTS

The German HNPCC consortium is based on an efficient cooperation between clinical physicians, human geneticists, and surgical pathologists. After a funding period from the Deutsche Krebshilfe, HNPCC diagnostics and preventive medical examinations were transferred into standard care in Germany. In total, 5770 families (8873 patients) were included in HNPCC diagnostics. To date, in 1296 families, mutations of the MLH1-, MSH2-, MSH6-, PMS2-, or EPCAM-gene have been detected. Furthermore, 612 pathogenic variants and 325 variants of unknown significance were found.

CONCLUSIONS

Reliable detection of HNPCC patients is based on a standardized diagnostic concept, which has been established within the German HNPCC consortium.

Molecular Diagnostics in Colorectal Carcinoma: Advances and Applications for 2018

The molecular pathogenesis and classification of colorectal carcinoma are based on the traditional adenomaecarcinoma sequence, serrated polyp pathway, and microsatellite instability (MSI). The genetic basis for hereditary nonpolyposis colorectal cancer is the detection of mutations in the MLH1, MSH2, MSH6, PMS2, and EPCAM genes. Genetic testing for Lynch syndrome includes MSI testing, methylator phenotype testing, BRAF mutation testing, and molecular testing for germline mutations in MMR genes. Molecular makers with predictive and prognostic implications include quantitative multigene reverse transcriptase polymerase chain reaction assay and KRAS and BRAF mutation analysis. Mismatch repair-deficient tumors have higher rates of programmed death-ligand 1 expression. Cell-free DNA analysis in fluids are proving beneficial for diagnosis and prognosis in these disease states towards effective patient management.

Do alcoholic beverages, obesity and other nutritional factors modify the risk of familial colorectal cancer? A systematic review

PURPOSE

Individuals with family history of colorectal cancer are at higher risk of colorectal cancer than the general population. Until now, guidelines for familial colorectal cancer risk have only pointed at early diagnosis efforts via screening tests and surveillance, and payed scarce or no attention to lowering exposure to modifiable risk factors, notably nutritional factors.

METHODS

We conducted a systematic review of epidemiological studies investigating the associations between nutritional factors, family history of colorectal cancer, and colorectal cancer risk. From the 5312 abstracts identified until December 2016, 184 full text articles were examined for eligibility. Finally, 31 articles (21 from case-control studies, 9 from cohort studies and 1 from an intervention study) met inclusion criteria and were analyzed.

RESULTS

Mainly, the combinations of family history of colorectal cancer and higher consumptions of alcoholic beverages, red or processed meat, or overweight/obesity increase the risk of colorectal cancer. Consistently, a strong increase is observed with the combinations of family history of colorectal cancer and unhealthy dietary patterns/lifestyles. Statistically significant interactions between these nutritional factors, family history of colorectal cancer and colorectal cancer risk are reported. Other data are inconclusive and additional prospective studies are needed.

CONCLUSIONS

For the first time, our findings highlight that addressing high consumption of alcoholic beverages, red or processed meat, and overweight/obesity, and more largely the exposure to multiple unhealthy dietary/nutritional behaviors could offer new perspectives of prevention to individuals with family history of colorectal cancer. A better information of these patients and of health professionals on these nutritional modifiable risk factors is recommended.

The current value of determining the mismatch repair status of colorectal cancer: A rationale for routine testing. Crit Rev Oncol Hematol. 2017;116:38-57. [PMID: 28693799 DOI: 10.1016/j.critrevonc.2017.05.006]

Colorectal Cancer (CRC) is the third most prevalent cancer in men and women. Up to 15% of CRCs display microsatellite instability (MSI). MSI is reflective of a deficient mismatch repair (MMR) system and is most commonly caused by hypermethylation of the MLH1 promoter. However, it may also be due to autosomal dominant constitutional mutations in DNA MMR, termed Lynch Syndrome. MSI may be diagnosed via polymerase chain reaction (PCR) or alternatively, immunohistochemistry (IHC) can identify MMR deficiency (dMMR). Many institutions now advocate universal tumor screening of CRC via either PCR for MSI or IHC for dMMR to guide Lynch Syndrome testing. The association of sporadic MSI with methylation of the MLH1 promoter and an activating BRAF mutation may offer further exclusion criteria for genetic testing. Aside from screening for Lynch syndrome, MMR testing is important because of its prognostic and therapeutic implications. Several studies have shown MSI CRCs exhibit different clinicopathological features and prognosis compared to microsatellite-stable (MSS) CRCs. For example, response to conventional chemotherapy has been reported to be less in MSI tumours. More recently, MSI tumours have been shown to be responsive to immune-checkpoint inhibition providing a novel therapeutic strategy. This provides a rationale for routine testing for MSI or dMMR in CRC.

3'-UTR poly(T/U) repeat of EWSR1 is altered in microsatellite unstable colorectal cancer with nearly perfect sensitivity

Approximately 15% of colorectal cancers exhibit instability of short nucleotide repeat regions, microsatellites. These tumors display a unique clinicopathologic profile and the microsatellite instability status is increasingly used to guide clinical management as it is known to predict better prognosis as well as resistance to certain chemotherapeutics. A panel of five repeats determined by the National Cancer Institute, the Bethesda panel, is currently the standard for determining the microsatellite instability status in colorectal cancer. Recently, a quasimonomorphic mononucleotide repeat 16T/U at the 3' untranslated region of the Ewing sarcoma breakpoint region 1 gene was reported to show perfect sensitivity and specificity in detecting mismatch repair deficient colorectal, endometrial, and gastric cancers in two independent populations. To confirm this finding, we replicated the analysis in 213 microsatellite unstable colorectal cancers from two independent populations, 148 microsatellite stable colorectal cancers, and the respective normal samples by PCR and fragment analysis. The repeat showed nearly perfect sensitivity for microsatellite unstable colorectal cancer as it was altered in 212 of the 213 microsatellite unstable (99.5%) and none of the microsatellite stable colorectal tumors. This repeat thus represents the first potential single marker for detecting microsatellite instability.

Microsatellite instability: an update

Deficient DNA mismatch repair (MMR) results in a strong mutator phenotype known as microsatellite instability (MSI), which is a hallmark of Lynch syndrome-associated cancers. MSI is characterized by length alterations within simple repeated sequences that are called microsatellites. Lynch syndrome is primarily caused by mutations in the MMR genes, mainly MLH1 and MSH2, and less frequently in MSH6, and rarely PMS2, and large genomic rearrangements account for 5-20 % of all mutations. Germ line hemiallelic methylations of MLH1 or MSH2 are termed as epimutations and have been identified as causative of Lynch syndrome. Moreover, germ line 3' deletions of EPCAM gene is involved in MSH2 methylation. MSI is also observed in about 15 % of sporadic colorectal cancer (CRC), gastric cancer (GC), and endometrial cancer (EC), and at lower frequencies in other cancers, often in association with hypermethylation of the MLH1 gene. Trimethylation of histone H3 on Lys36 (H3K36 me3) is an epigenetic histone mark that was required for DNA MMR in vivo. Thus, mutations in the H3K36 trimethyltransferase SETD2 have been reported as a potential cause of MSI. Genetic, epigenetic, and transcriptomic differences have been identified between cancers with and without MSI. Recent comprehensive molecular characterizations of CRC, EC, and GC by The Cancer Genome Atlas indicate that MSI+ cancers are distinct biological entities. The BRAF V600E mutation is specifically associated with sporadic MSI+ CRCs with methylated MLH1, but is not associated with Lynch syndrome-related CRCs. Accumulating evidence indicates a role of interactions between MSI and microRNA (miRNA) in the pathogenesis of MSI-positive (MSI+) cancer. As another new mechanism underlying MSI, overexpression of miR-155 or miR-21 has been shown to downregulate the expression of the MMR genes. Gene targets of frameshift mutations caused by MSI are involved in various cellular functions, including DNA repair (MSH3 and MSH6), cell signaling (TGFBR2 and ACVR2A), apoptosis (BAX), epigenetic regulation (HDAC2 and ARID1A), and miRNA processing (TARBP2 and XPO5), and a subset of MSI+ CRCs reportedly shows the mutated miRNA machinery phenotype. Moreover, microsatellite repeats in miRNA genes, such as hsa-miR-1273c, may be novel MSI targets for CRC, and mutations in noncoding regulatory regions of MRE11, BAX (BaxΔ2), and HSP110 (HSP110ΔE9) may affect the efficiency of chemotherapy. Thus, analyses of MSI and its related molecular alterations in cancers are increasingly relevant in clinical settings, and MSI is a useful screening marker for identifying patients with Lynch syndrome and a prognostic factor for chemotherapeutic interventions. In this review, we summarize recent advances in the pathogenesis of MSI and focus on genome-wide analyses that indicate the potential use of MSI and related alterations as biomarkers and novel therapeutic targets.

A homozygous PMS2 founder mutation with an attenuated constitutional mismatch repair deficiency phenotype

BACKGROUND

Inherited mutations in DNA mismatch repair genes predispose to different cancer syndromes depending on whether they are mono-allelic or bi-allelic. This supports a causal relationship between expression level in the germline and phenotype variation. As a model to study this relationship, our study aimed to define the pathogenic characteristics of a recurrent homozygous coding variant in PMS2 displaying an attenuated phenotype identified by clinical genetic testing in seven Inuit families from Northern Quebec.

METHODS

Pathogenic characteristics of the PMS2 mutation NM_000535.5:c.2002A>G were studied using genotype-phenotype correlation, single-molecule expression detection and single genome microsatellite instability analysis.

RESULTS

This PMS2 mutation generates a de novo splice site that competes with the authentic site. In homozygotes, expression of the full-length protein is reduced to a level barely detectable by conventional diagnostics. Median age at primary cancer diagnosis is 22 years among 13 NM_000535.5:c.2002A>G homozygotes, versus 8 years in individuals carrying bi-allelic truncating mutations. Residual expression of full-length PMS2 transcript was detected in normal tissues from homozygotes with cancers in their 20s.

CONCLUSIONS

Our genotype-phenotype study of c.2002A>G illustrates that an extremely low level of PMS2 expression likely delays cancer onset, a feature that could be exploited in cancer preventive intervention.

Molecular diagnostics in colorectal carcinoma

Molecular pathogenesis and classification of colorectal carcinoma are based on the adenoma-carcinoma sequence in the Vogelstein model, serrated polyp pathway, and microsatellite instability. The genetic basis for hereditary nonpolyposis colorectal cancer is based on detection of genetic mutations. Genetic testing for Lynch syndrome includes microsatellite instability, methylator phenotyping, BRAF mutation, and molecular testing. Molecular makers include quantitative multigene reverse transcriptase-polymerase chain reaction assay and KRAS and BRAF mutation analysis. Potential biomarkers include one-step nucleic acid amplification and epigenetic inactivation of endothelin 2 and endothelin 3 in colon cancer. Molecular screening approaches in colorectal cancer using stool DNA are under investigation.

DNA mismatch repair MSH2 gene-based SNP associated with different populations

We screened for the major essential single-nucleotide polymorphism (SNP) variant that might be associated with the MSH2 gene based on the data available from three types of human tissue samples [156 lymphoblastoid cell variations (LCL), 160 epidermis, 166 fat]. An association analysis confirmed that the KCNK12 SNP variant (rs748780) was highly associated (p value 9 × 10(-4)) with the MSH2 gene for all three samples. Using SNP identification, we further found that the recognized SNP was also relevant among Hapmap populations. Techniques that display specific SNPs associated with the gene of interest or nearby genes provide more reliable genetic associations than techniques that rely on data from individual SNPs. We investigated the MSH2 gene regional linkage association with the determined SNP (rs748780), KCNK12 variant (Allele T>C) in the intronic region, in HapMap3 full dataset populations, Yoruba in Ibadan, Nigeria (YRI), Utah residents with ancestry from northern Europe (CEU), Han Chinese in Beijing, China (CHB), and a population of Mexican ancestry in Los Angeles, California (MEX). A gene-based SNP association analysis analyzes the combined impact of every variant within the gene while creating referrals to linkage disequilibrium or connections between markers. Our results indicated that among the four populations studied, this association was highest in the MEX population based on the r(2) value; a similar pattern was also observed in the other three populations. The relevant SNP rs748780 in KCNK12 is related to a superfamily of potassium channel pore-forming P-domain proteins as well as to other non-pore-forming proteins and has been shown to be relevant to neurological disorder predisposition in MEX as well as in other populations.

DNA content analysis of colorectal cancer defines a distinct 'microsatellite and chromosome stable' group but does not predict response to radiotherapy

Colorectal cancers (CRC) are thought to have genetic instability in the form of either microsatellite instability (MSI) or chromosomal instability (CIN). Recently, tumours have been described without either MSI or CIN, that is, microsatellite and chromosome stable (MACS) CRCs. We investigated the (i) frequency of the MACS-CRCs and (ii) whether this genotype predicted responsiveness to neoadjuvant chemoradiotherapy. To examine the frequency of MACS-CRCs, DNA content (ploidy) was examined in 89 sporadic microsatellite-stable CRCs using flow cytometry. The tumours were also screened for mutations in KRAS/BRAF/TP53/PIK3CA by QMC-PCR. To examine the value of tumour ploidy in predicting response to chemoradiotherapy, DNA content was tested in a separate group of 62 rectal cancers treated with neoadjuvant chemoradiotherapy. Fifty-one of 89 CRCs (57%) were aneuploid and 38 (43%) were diploid. There was no significant association between mutations in TP53/KRAS/BRAF/PIK3CA and ploidy. Testing of association between mutations revealed only mutual exclusivity of KRAS/BRAF mutation (P < 0.001). Of the 62 rectal cancers treated with neoadjuvant chemoradiotherapy, 22 had responded (Mandard tumour regression grade 1/2) and 40 failed to respond (Grade 3-5). Twenty-five of 62 (40%) tumours were diploid, but there was no association between ploidy and response to therapy. We conclude that MACS-CRCs form a significant proportion of microsatellite-stable CRCs with a mutation profile overlapping that of CRCs with CIN. A diploid genotype does not, however, predict the responsiveness to radiotherapy.

Toxicogenomics and cancer susceptibility: advances with next-generation sequencing

The aim of this review is to comprehensively summarize the recent achievements in the field of toxicogenomics and cancer research regarding genetic-environmental interactions in carcinogenesis and detection of genetic aberrations in cancer genomes by next-generation sequencing technology. Cancer is primarily a genetic disease in which genetic factors and environmental stimuli interact to cause genetic and epigenetic aberrations in human cells. Mutations in the germline act as either high-penetrance alleles that strongly increase the risk of cancer development, or as low-penetrance alleles that mildly change an individual's susceptibility to cancer. Somatic mutations, resulting from either DNA damage induced by exposure to environmental mutagens or from spontaneous errors in DNA replication or repair are involved in the development or progression of the cancer. Induced or spontaneous changes in the epigenome may also drive carcinogenesis. Advances in next-generation sequencing technology provide us opportunities to accurately, economically, and rapidly identify genetic variants, somatic mutations, gene expression profiles, and epigenetic alterations with single-base resolution. Whole genome sequencing, whole exome sequencing, and RNA sequencing of paired cancer and adjacent normal tissue present a comprehensive picture of the cancer genome. These new findings should benefit public health by providing insights in understanding cancer biology, and in improving cancer diagnosis and therapy.

Health behaviors in patients and families with hereditary colorectal cancer

It is estimated that 5 to 10% of all colorectal cancer (CRC) cases are attributed to a hereditary cause. The primary hereditary cancer syndromes that confer an increased risk for colorectal cancers are Lynch syndrome/hereditary nonpolyposis colorectal cancer (HNPCC) and familial adenomatous polyposis (FAP). Through genetic testing, health care providers can identify patients and families who carry gene mutations and subsequently are at a substantially greater risk for developing colorectal cancer than the general population. Genetic testing provides risk information not only about an individual patient, but also his or her biological relatives. A variety of risk-reduction behaviors (including screening, surgery, and health and lifestyle behaviors) have been examined in Lynch syndrome and FAP populations. The research indicates that screening behaviors are less than optimal, although the rates vary from study to study. Prophylactic colectomy is the primary course of treatment for individuals who test positive for a FAP mutation, but the results are inconclusive for cancer-unaffected Lynch syndrome mutation carriers. Although research suggests that the adoption of healthy lifestyles and behaviors (e.g., diet, physical activity, weight control, smoking cessation, limited alcohol consumption) could have a favorable impact on colon cancer burden, there is minimal data on how these behaviors may moderate cancer risk among those at risk of hereditary colon cancer. To date, we know very little about the actual health and lifestyle behaviors of those at risk of hereditary colon cancer. Genetic testing and counseling at risk individuals may resolve uncertainty about their personal and familial cancer risk and provide information to guide and personalize decisions about their future health care.

Uroepithelial and kidney carcinoma in Lynch syndrome

Increased risk for urological tumors has been observed in mutation carriers with Lynch syndrome (LS). In this study, we evaluated the clinical features of uroepithelial (bladder and ureter) and kidney cancers in 974 Finnish mutation carriers. Altogether 30 patients had a total of 34 urological tumors: 12 ureter, 12 bladder, and 10 kidney cancers. Urological tumor was the only tumor in 9 (30 %) patients, and metachronous other tumor occurred in 21 (70 %). The occurrence of uroepithelial cancers was significantly higher in MSH2 mutation carriers (6 %; 95 % CI, 2.7-11.0) than in MLH1 carriers (2 %; 95 % CI, 1.1-3.2) and MSH6 mutation carriers (0 %) (p = 0.014). The mean ages of patients at the time of diagnosis were: bladder cancer, 57 years; ureter cancer, 58 years; and kidney cancer, 64 years. Overall 5-year survival rates were 70 % (95 % CI, 0.32-0.89) in bladder cancer, 81 % (95 % CI, 0.45-0.95) in ureter cancer, and 75 % (95 % CI, 0.31-0.93) in kidney cancer. Cancer-specific 5-year survival rates were 70 % (95 % CI, 0.32-0.89) in bladder cancer, 91 % (95 % CI, 0.51-0.98) in ureter cancer, and 100 % in kidney cancer. In conclusion, early age of onset was observed in patients with uroepithelial tumors, but not in patients with kidney cancer. The frequency of uroepithelial tumors was significantly higher in MSH2 mutation carriers than in MLH1 carriers. Further studies with larger numbers of patients, however, are needed to evaluate the potential benefit of surveillance of urological tumors in LS.

A mobile colonoscopic unit for lynch syndrome: trends in surveillance uptake and patient experiences of screening in a developing country

The Genetic and Endoscopic Surveillance Clinic is an annual outreach service offering accessible colonoscopic surveillance to known families with Lynch syndrome living in remote areas of the Western and Northern Cape Province of South Africa. Unfortunately attendance at this outreach clinic has been declining over several years and fewer than a quarter of participants, attending for surveillance, have been adherent with all their recommended screening appointments. Concerns exist for non-adherent individuals as screening can prevent colorectal cancer by removing the precancerous lesion or enabling the treatment of a malignancy at an early stage. This study explored the experience of surveillance from both the non-adherers' and adherers' perspectives and identified unique factors affecting attendance at the outreach clinic. Rates of compliance are calculated for 191 mutation-positive cases of Lynch syndrome, using strict attendance criteria, and compared to figures obtained from self-reported attendance. Non-compliance was under-reported and compliance was exaggerated when basing data on self-reported adherence to recommendations. Specific characteristics of the outreach clinic affecting compliance are identified and recommendations are made to facilitate improvements to the service. These improvements can result in increased compliance with screening regimens and ultimately reduce cancer-related mortality.

Dietary patterns and colorectal adenomas in Lynch syndrome: the GEOLynch cohort study

BACKGROUND

Patients with Lynch syndrome (LS) have a high risk of developing colorectal cancer due to mutations in mismatch repair genes. Because dietary factors, alone and in combination, influence sporadic colorectal carcinogenesis, the association of dietary patterns with colorectal adenomas in LS patients was assessed.

METHODS

In the GEOLynch cohort of 486 persons with LS, dietary information was collected, using a food frequency questionnaire. Dietary pattern scores were obtained by principal components analysis. Hazard ratios (HR) between dietary patterns and colorectal adenomas were calculated using Cox regression models. Robust sandwich variance estimates were used to control for dependency within families. Final models were adjusted for age, sex, smoking habits, colorectal adenoma history, and extent of colon resection.

RESULTS

During a median follow-up of 20 months, colorectal adenomas were detected in 58 persons. Four dietary patterns were identified: a "Prudent," "Meat," "Snack," and "Cosmopolitan" pattern. Individuals within the highest tertile of the "Prudent" pattern had a HR of 0.73 (95% confidence interval [CI], 0.32-1.66) for colorectal adenomas, compared with the lowest tertile. Those with high "Meat" pattern scores had a HR of 1.70 (95% CI, 0.83-3.52). A high "Snack" pattern was associated with an increased risk of colorectal adenomas (HR, 2.16; 95% CI, 1.03-4.49). A HR of 1.25 (95% CI, 0.61-2.55) was observed for persons in the highest tertile of the "Cosmopolitan" pattern.

CONCLUSIONS

These findings suggest that dietary patterns may be associated with development of colorectal adenoma in patients with Lynch syndrome. The directions of these findings are corroborative with those observed in studies investigating sporadic colorectal cancer.

Clinicopathological features and management of cancers in lynch syndrome

Lynch syndrome (LS) is characterized by an autosomal dominant inheritance of the early onset of colorectal cancer (CRC) and endometrial cancer, as well as increased risk for several other cancers including gastric, urinary tract, ovarian, small bowel, biliary tract, and brain tumors. The syndrome is due to a mutation in one of the four DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6, or PMS2. The majority of LS patients and families can now be identified, and the underlying mutation detected using genetic diagnostics. Regular surveillance for CRC and endometrial cancer has proved beneficial for mutation carriers. However, screening for other tumors is also recommended even though experiences in the screening of these tumors is limited. Prophylactic colectomy, prophylactic hysterectomy, and bilateral salpingo-oophorectomy may be reasonable options for selected patients with LS. This paper describes the features and management of LS.

Polymorphisms of mismatch repair gene hMLH1 and hMSH2 and risk of gastric cancer in a Chinese population

The purpose of this study was to determine the genotype and allele frequencies of hMLH1 (-93G>A and I219V) and hMSH2 (-118T>C and IVS12-6T>C) polymorphisms in patients with gastric carcinoma and normal controls, and to evaluate the association between these polymorphisms and the risk of gastric cancer in a hospital-based Chinese population. Genomic DNA was extracted from peripheral blood lymphocytes. A TaqMan assay was used to determine the genotype and allele frequencies of hMLH1 and hMSH2 polymorphisms in data obtained from 554 gastric cancer cases and 592 controls. Unconditional logistic regression was used to assess the association between the four single nucleotide polymorphisms (SNPs) and gastric carcinoma risk. No evidence of an association among any of the four polymorphisms and the risk of gastric cancer was observed. However, when gastric cancer patients were further stratified by age, gender, smoking status, alcohol use and clinicopathological characteristics, and compared with the control populations, the combined variant genotype hMSH2 -118T>C (TC+CC) was not only associated with an increased risk of gastric cancer in subgroups of younger subjects [ages ≤63years; adjusted odds ratio (OR)=1.51, 95% confidence interval (CI), 1.05-2.16], but also with diffuse tumors (adjusted OR=1.41, 95% CI, 1.01-1.96). These data indicate that the polymorphisms of -93G>A, I219V and IVS12-6T>C are not associated with the risk of gastric cancer. However, hMSH2-118T>C combined with variant genotypes (TC+CC) may confer a potential risk of gastric cancer in the Chinese population.

MUTYH Associated Polyposis (MAP)

MUTYH Associated Polyposis (MAP), a Polyposis predisposition caused by biallelic mutations in the Base Excision Repair (BER) gene MUTYH, confers a marked risk of colorectal cancer (CRC). The MAP phenotype is difficult to distinguish from other hereditary CRC syndromes. Especially from Familial Adenomatous Polyposis (FAP) and to a lesser extend Lynch Syndrome, which are caused by germline mutations in the APC and Mismatch Repair (MMR) genes, respectively.

Here we review research findings regarding MUTYH interactions, genotypic and phenotypic characteristics of MAP, as well as surveillance and treatment of the disease. The applied papers, published between 1/1 2002- 1/2 2008, were found through PubMed.

The exact role of MUTYH in CRC tumorgenesis is still uncertain, although MAP tumors show distinct molecular features, including somatic G:C>T:A transversions in the APC gene. Furthermore, cooperation between the BER and the MMR systems exists, as MUTYH interacts with MMR gene-products. Possibly, monoallelic defects in both pathways are of significance to CRC development.

Specific MUTYH variants are found to be characteristic in distinct ethnic populations, which could facilitate future genetic screening. Knowledge concerning functional consequences of many MUTYH germline mutations remains sparse. Most thoroughly investigated are the two most common MUTYH variants, Y179C and G396D, both generating dysfunctional gene products.

Phenotypic features of MAP include: development of 10-100 colorectal adenomas, debuting at 46-47 years, often CRC at time of clinical diagnosis, and in some, development of extracolonic manifestations.

Genomic instability and carcinogenesis: an update

Cancers arise as a result of stepwise accumulation of mutations which may occur at the nucleotide level and/or the gross chromosomal level. Many cancers particularly those of the colon display a form of genomic instability which may facilitate and speed up tumor initiation and development. In few instances, a "mutator mutation" has been clearly implicated in driving the accumulation of other carcinogenic mutations. For example, the post-replicative DNA mismatch repair deficiency results in dramatic increase in insertion/deletion mutations giving rise to the microsatellite instability (MSI) phenotype and may predispose to a spectrum of tumours when it occurs in the germline. Although many sporadic cancers show multiple mutations suggesting unstable genome, the role of this instability in carcinogenesis, as opposed to the power of natural selection, has been a matter of controversy. This review gives an update of the latest data on these issues particularly recent data from genome-wide, high throughput techniques as well as mathematical modelling. Throughout this review, reference will be made to the relevance of genomic instability to the pathogenesis of colorectal carcinoma particularly its hereditary and familial subsets.

Molecular diagnostics of colorectal cancer

CONTEXT

Of all gastrointestinal tract epithelial malignancies, molecular diagnostics has impacted colorectal cancer the most. Molecular testing can detect sporadic and inherited colorectal cancers that arise through the microsatellite instability pathway and can determine the efficacy of targeted drug therapy.

OBJECTIVES

To review the microsatellite instability pathway of colorectal carcinoma carcinogenesis and to demonstrate the diagnostic utility of molecular testing in the detection of patients with Lynch syndrome, an inherited disorder of this pathway. Also, to review the significance of detection of KRAS and BRAF gene mutations in predicting the response to anti-epidermal growth factor receptor therapies.

DATA SOURCES

This article is based on original publications and review articles that are accessible through the PubMed biomedical database (US National Library of Medicine).

CONCLUSIONS

In modern pathology practice, molecular testing is a standard tool that is used to diagnose an inherited colorectal cancer predisposition syndrome (Lynch syndrome) and to help predict outcome and response to therapy for patients with advanced colorectal cancer.

Prevalence of alterations in DNA mismatch repair genes in patients with young-onset colorectal cancer

BACKGROUND & AIMS

Direct germline analysis could be used to screen high-risk patients for mutations in DNA mismatch repair genes associated with Lynch Syndrome. We examined the prevalence of mutations in MLH1, MSH2, and MSH6 in a population-based sample of patients with young-onset (age <50 years) colorectal cancer (CRC).

METHODS

Young-onset CRC cases were randomly selected from 3 Colon Cancer Family Registry sites. DNA was extracted from peripheral blood leukocytes; MLH1, MSH2, and MSH6 were sequenced, and duplication and deletion analyses was performed for MLH1 and MSH2. Results were reported as deleterious or suspected deleterious, likely neutral, variant of uncertain significance, or no alteration detected. Germline data were compared to Amsterdam II criteria (ACII) and immunohistochemistry results in secondary analyses.

RESULTS

Among 195 subjects, 11 had deleterious/suspected deleterious mutations (5.6%; 95% confidence interval [CI], 2.8%-9.9%), 12 had likely neutral alterations (6.2%; 95% CI, 3.2%-10.5%), 14 had variants of uncertain significance (7.2%; 95% CI, 4.0%-11.8%), 2 had a likely neutral alteration and a variant of uncertain significance (1.0%; 95% CI, 0.1%-3.7%), and 156 had no alteration detected (80.0%; 95% CI, 73.7%-85.4%). Sensitivity, specificity, and positive and negative predictive values for detecting deleterious/suspected deleterious mutations, based on ACII, were 36.4% (4/11), 96.7% (178/184), 40.0% (4/10), and 96.2% (178/185), respectively; based on immunohistochemistry these values were 85.7% (6/7), 91.9% (136/148), 33.3% (6/18), and 99.3% (136/137), respectively.

CONCLUSIONS

In a population-based sample of young-onset CRC cases, germline mutations in MLH1, MSH, and/or MSH6 were more prevalent than reported for CRC patients overall. Because only about 5% of young-onset CRC cases had confirmed deleterious or suspected deleterious mutations, further comparative effectiveness research is needed to determine the most appropriate screening strategy for Lynch Syndrome in this high-risk group.

Transgenic animal models in toxicology: historical perspectives and future outlook

Transgenic animal models are powerful tools for developing a more detailed understanding on the roles of specific genes in biological pathways and systems. Applications of these models have been made within the field of toxicology, most notably for the screening of mutagenic and carcinogenic potential and for the characterization of toxic mechanisms of action. It has long been a goal of research toxicologists to use the data from these models to refine hazard identification and characterization to better inform human health risk assessments. This review provides an overview on the applications of transgenic animal models in the assessment of mutagenicity and carcinogenicity, their use as reporter systems, and as tools for understanding the roles of xenobiotic-metabolizing enzymes and biological receptors in the etiology of chemical toxicity. Perspectives are also shared on the future outlook for these models in toxicology and risk assessment and how transgenic technologies are likely to be an integral tool for toxicity testing in the 21st century.

Bayesian mixture models for the incorporation of prior knowledge to inform genetic association studies

In the last decade, numerous genome-wide linkage and association studies of complex diseases have been completed. The critical question remains of how to best use this potentially valuable information to improve study design and statistical analysis in current and future genetic association studies. With genetic effect size for complex diseases being relatively small, the use of all available information is essential to untangle the genetic architecture of complex diseases. One promising approach to incorporating prior knowledge from linkage scans, or other information, is to up- or down-weight P-values resulting from genetic association study in either a frequentist or Bayesian manner. As an alternative to these methods, we propose a fully Bayesian mixture model to incorporate previous knowledge into on-going association analysis. In this approach, both the data and previous information collectively inform the association analysis, in contrast to modifying the association results (P-values) to conform to the prior knowledge. By using a Bayesian framework, one has flexibility in modeling, and is able to comprehensively assess the impact of model specification on posterior inferences. We illustrate the use of this method through a genome-wide linkage study of colorectal cancer, and a genome-wide association study of colorectal polyps.

When brachytherapy met genetic oncology. Can radiation oncologists improve the detection of hereditary non-polyposis colorectal cancer?

Between January 1994 and December 2004, 696 patients with localized endometrial carcinoma have been treated at the Institute Jean-Godinot. Patients were selected on the following criteria: histologically proven adenocarcinoma of the endometrium; age at onset under 60 years; patient not deceased at the time of the study. One hundred twelve patients met these criteria and received a mailed specific questionnaire to establish their pedigree. Thirty-one patients (35.5%) were eventually found eligible for a genetic counselling but only 13 patients agreed to be informed later on. According to the obtained pedigrees and MSI test results, 7 genetic tests have been carried out and so far, 3 MMR mutations were detected. This study suggested the feasibility of a step by step screening of endometrial cancers to select patients at risk for Lynch syndrome and for whom a genetic test would be recommended. Authors suggest that either Amsterdam or Bethesda criteria should be systematically used prospectively in every newly diagnosed endometrial cancer and retrospectively using clinical databases available on endometrial cancers.

Screening of the DNA mismatch repair genes MLH1, MSH2 and MSH6 in a Greek cohort of Lynch syndrome suspected families

Background

Germline mutations in the DNA mismatch repair genes predispose to Lynch syndrome, thus conferring a high relative risk of colorectal and endometrial cancer. The MLH1, MSH2 and MSH6 mutational spectrum reported so far involves minor alterations scattered throughout their coding regions as well as large genomic rearrangements. Therefore, a combination of complete sequencing and a specialized technique for the detection of genomic rearrangements should be conducted during a proper DNA-testing procedure. Our main goal was to successfully identify Lynch syndrome families and determine the spectrum of MLH1, MSH2 and MSH6 mutations in Greek Lynch families in order to develop an efficient screening protocol for the Greek colorectal cancer patients' cohort.

Methods

Forty-two samples from twenty-four families, out of which twenty two of Greek, one of Cypriot and one of Serbian origin, were screened for the presence of germline mutations in the major mismatch repair genes through direct sequencing and MLPA. Families were selected upon Amsterdam criteria or revised Bethesda guidelines.

Results

Ten deleterious alterations were detected in twelve out of the twenty-four families subjected to genetic testing, thus our detection rate is 50%. Four of the pathogenic point mutations, namely two nonsense, one missense and one splice site change, are novel, whereas the detected genomic deletion encompassing exon 6 of the MLH1 gene has been described repeatedly in the LOVD database. The average age of onset for the development of both colorectal and endometrial cancer among mutation positive families is 43.2 years.

Conclusion

The mutational spectrum of the MMR genes investigated as it has been shaped by our analysis is quite heterogeneous without any strong indication for the presence of a founder effect.

Body mass index increases risk of colorectal adenomas in men with Lynch syndrome: the GEOLynch cohort study

PURPOSE

High body mass index (BMI) is an established risk factor for sporadic colorectal cancer. Still, the influence of BMI on hereditary colorectal cancer (eg, Lynch syndrome [LS]), is unknown. The objective of this study was to assess whether BMI is associated with colorectal adenoma occurrence in persons with LS.

PATIENTS AND METHODS

A prospective cohort study of 486 patients with LS was conducted. Cox regression models with robust sandwich estimates controlling for age, sex, extent of colon surgery, smoking, and alcohol intake were used to evaluate associations between BMI, height, weight, weight change, and risk of colorectal adenomas. Analyses were performed separately for those without (incident cohort; n = 243) and those with (prevalent cohort; n = 243) a history of colorectal cancer neoplasms at baseline.

RESULTS

A statistically significant association between current overweight (≥ 25 kg/m(2)) and developing colorectal adenomas was seen among men in the incident cohort (overweight v normal weight hazard ratio [HR], 8.72; 95% CI, 2.06 to 36.96). This association was not observed among women (overweight v normal weight HR, 0.75; 95% CI, 0.19 to 3.07), nor was it observed in the prevalent cohort. In the incident cohort, height was statistically significantly associated with a decreased risk of adenomatous polyps among men (per 5 cm HR, 0.43; 95% CI, 0.23 to 0.83), but the association between weight and adenomatous polyps among men was of marginal significance (per 5 kg HR, 1.17; 95% CI, 1.00 to 1.37). No statistically significant associations were observed among women in either the incident cohort or the prevalent cohort.

CONCLUSION

Excess body weight increased the risk of incident colorectal adenomas in people with LS. This increased risk was seen only in men.

PMS1 from Arabidopsis thaliana: optimization of protein overexpression in Escherichia coli

One of the major limitations when attempting to obtain detailed biochemical, biophysical and immunological characterization of plant DNA mismatch repair proteins is their extremely low abundance in vivo under normal growth conditions. An initial analysis of PMS1 transcript level in various Arabidopsis thaliana tissues was carried out by quantitative real-time RT-PCR. For calli, flowers and seedlings, the corresponding cDNA copies per ng RNA were 66.9, 3.1 and 2.7, respectively. This suggests an important role of this gene in rapidly dividing tissues. In order to obtain a high level of PMS1 from Arabidopsis thaliana, the protein production was successfully optimized in an Escherichia coli host. The corresponding coding sequence of PMS1 was inserted into pET28a downstream a hexa-histidyl leader sequence. The pET28a-AtPMS1 plasmid was efficiently expressed in JM109(DE3)-pRIL strain probably due to the genotype features of the cells (endA1, recA1, relA1, Δ(lac-proAB), laqIqZΔM15) and the presence of extra copies of argU, ileY, and leuW tRNA genes, which encode the RIL codons. This strategy has allowed us to obtain His-tagged PMS1 at about 7% of the total soluble E. coli cell protein. The protein was purified by standard Ni(+) affinity chromatography procedures and the electrophoretically homogeneous preparation was used as an antigen for antibody generation in rabbits. This approach provides effective tools for a further reconstitution of plant mismatch repair (MMR) system in vitro and for the analysis of protein expression and distribution of AtPMS1 in various tissues after different treatments (e.g. DNA mutagens).

Microsatellite instability as a marker of prognosis and response to therapy: a meta-analysis of colorectal cancer survival data

BACKGROUND AND METHODS

We have reviewed and pooled data from published studies to evaluate the relationship between microsatellite instability (MSI) and colorectal cancer (CRC) prognosis. Thirty-one eligible studies reporting survival in 12782 patients characterised for MSI were pooled using a fixed- or random-effects model.

RESULTS

The summary odds ratio (OR) estimate for overall survival (OS) associated with MSI was 0.6 (95%CI 0.53-0.69, p<0.0001), with no evidence of heterogeneity. The effect was similar for disease-free survival (DFS) (OR=0.58, 95%CI 0.47-0.72, p<0.0001). In a subset of patients treated with 5-fluorouracil (5-FU)-based chemotherapy a significant improved prognosis was found for microsatellite stable (MSS) tumours (OR=0.52, 95%CI 0.4-0.6, p<0.0001) with no heterogeneity (p=0.53; I(2)=0%). By contrast a large heterogeneity characterised the data relative to 396 patients with MSI tumours (OR=0.69, 95%CI 0.3-1.5, p=0.1; heterogeneity: p=0.03; I(2)=58%).

CONCLUSIONS

This study confirmed the association between MSI and favourable prognosis as determined by both OS and DFS of CRC patients. A significant beneficial effect of 5-FU therapy was found for MSS tumours whilst no clear conclusion was reached for MSI tumours due to the high inter-study heterogeneity. We propose that this inconclusive result is due to the use of a single marker, such as MSI, that cannot account alone for the complexity of the mechanisms underlying 5-FU cytotoxicity. Future studies to predict response to 5-FU chemotherapy should include additional genome stability markers.

In Lynch syndrome adenomas, loss of mismatch repair proteins is related to an enhanced lymphocytic response

AIMS

Lynch syndrome-associated tumours are characterized by the presence of an increased number of tumour-infiltrating lymphocytes. This enhanced lymphocytic response may be elicited by genetically altered proteins that may arise as a result of a defective DNA mismatch repair system. The aim was to investigate this hypothesis by correlating loss of mismatch repair proteins and infiltration of lymphocytes in Lynch syndrome-associated adenomas and hyperplastic polyps.

METHODS AND RESULTS

Mismatch repair protein expression and the number of tumour-infiltrating lymphocytes were assessed in Lynch syndrome (41 adenomas and nine hyperplastic polyps) and in familial colorectal cancer (nine adenomas and one hyperplastic polyp). Nineteen sporadic adenomas were included as a control group. Twenty of 32 (63%) adenomas with loss of mismatch repair protein expression showed an increase in tumour-infiltrating lymphocytes. Eight adenomas (8/32; 25%) displayed many tumour-infiltrating lymphocytes, whereas most adenomas (12/32; 38%) showed a minor increase. In adenomas with mismatch repair protein expression, both sporadic and Lynch syndrome associated, not one showed an increased number of tumour-infiltrating lymphocytes. Hyperplastic polyps in Lynch syndrome patients showed neither loss of mismatch repair expression nor an increase in tumour-infiltrating lymphocytes.

CONCLUSIONS

There is a correlation between the loss of mismatch repair proteins and the infiltration of lymphocytes in Lynch syndrome-associated adenomas.

From bacteria to plants: a compendium of mismatch repair assays

Mismatch repair (MMR) system maintains genome integrity by correcting mispaired or unpaired bases which have escaped the proofreading activity of DNA polymerases. The basic features of the pathway have been highly conserved throughout evolution, although the nature and number of the proteins involved in the mechanism vary from prokaryotes to eukaryotes and even between humans and plants. Cells deficient in MMR genes have been observed to display a mutator phenotype characterized by an increased rate in spontaneous mutation, instability of microsatellite sequences and illegitimate recombination between diverged DNA sequences. Studies of the mutator phenotype have demonstrated a critical role for the MMR system in mutation avoidance and genetic stability. Here, we briefly review our current knowledge of the MMR mechanism and then focus on the in vivo biochemical and genetic assays used to investigate the function of the MMR proteins in processing DNA mismatches generated during replication and mitotic recombination in Escherichia coli, Saccharomyces cerevisiae, Homo sapiens and Arabidopsis thaliana. An overview of the biochemical assays developed to study mismatch correction in vitro is also provided.

Widespread mismatch repair protein expression in canine cutaneous mast cell tumors

Cutaneous mast cell tumors (MCTs) are common canine neoplasms. Some dog breeds more frequently develop MCTs, suggesting a genetically mediated predisposition. In humans, the most common inherited cancer predisposition is caused by germline defects in the mismatch repair (MMR) genes. To investigate whether inherited defects in the MMR genes predispose some dogs to MCT development, MMR expression in 22 MCTs from young and predisposed breed dogs was compared with MMR expression in 22 MCTs from old dogs of non-MCT-predisposed breeds. MMR expression was investigated immunohistochemically using antibodies against MLH1, MSH2, and MSH6. Mast cells within all MCTs expressed MLH1, MSH2, and MSH6. There were no significant differences in the intensity of immunoreactivity or the percentage of cells expressing MMR proteins between MCTs from the 2 groups of dogs. There were no significant differences in MMR protein expression between grade II and grade III MCTs. These results do not support the hypothesis that inherited MMR defects predispose some dogs to MCT development.

The molecular basis of cancer and the development of targeted therapy

The sequencing of the human genome and the ability to rapidly identify genes and proteins, both normal and mutant, that are involved in tumorigenesis and malignant phenotypes, have changed the ability to understand malignant cells. Understanding and applying this information to the diagnosis and treatment of cancer are facilitated best with a multidisciplinary team. The cancer surgeon plays a pivotal role in this team. This article briefly summarizes: (1) the clinically relevant applications of molecular biology to the cancer surgeon, (2) the current understanding of the molecular basis for cancer, and (3) the current targeted agents and their clinical applications.

A comparison of models used to predict MLH1, MSH2 and MSH6 mutation carriers

BACKGROUND

MMRpro, prediction of mutations in MLH1 and MLH2 (PREMM(1,2)) and MMRpredict are models which were developed to predict the probability that an individual carries a Lynch syndrome-causing mutation. Each model utilizes data from personal and family histories of cancer. To date, no studies have compared these models in a cancer genetics clinic. The purpose of this study was to determine each model's ability to predict the probability of carrying a Lynch syndrome-causing mutation in individuals with a family history of colorectal cancer and to determine their clinical applicability.

METHODS

We obtained family pedigrees from 81 individuals who presented for Lynch syndrome testing due to a personal and/or family history of cancer. Data from each pedigree were entered into the models and analyzed using SPSS.

RESULTS

We found that MMRpredict, PREMM(1,2) and MMRpro showed similar performances with areas under the receiver-operating characteristic curve of 0.731, 0.765 and 0.732, respectively. MMRpro showed the least dispersion of mutation probability estimates with a P value of 0.205, compared with 0.034 for PREMM(1,2) and 0.001 for MMRpredict.

CONCLUSION

We found all three carried out well in a cancer genetics setting, with PREMM(1,2) giving slightly better estimates. There were some significant discrepancies between the models in cases where the proband had endometrial cancer.

Report of a family segregating mutations in both the APC and MSH2 genes: juvenile onset of colorectal cancer in a double heterozygote

BACKGROUND AND AIMS

Mutations in DNA mismatch repair genes are associated with high risk of digestive malignancies [hereditary non-polyposis colorectal cancer (HNPCC); Lynch syndrome]; mutations of APC and MYH are associated with classic and attenuated familial adenomatous polyposis (FAP). Although the early onset of tumors in both syndromes is characteristic of their genetic origin, pediatric malignancies remain rare. Certain reports have found familial colorectal cancer (CRC) occurring in very young patients associated with mutations in more than one gene.

MATERIALS AND METHOD

A family corresponding to the Amsterdam criteria for HNPCC, including two cases of colorectal cancer before the age of 25 years, was analyzed for mutations in the MSH2 genes by sequencing. Because polyposis was observed in a patient who developed CRC at age 16, the APC gene was also sequenced.

RESULTS

A truncating mutation in the MSH2 gene, c.258_259delTG, was carried by patients developing cancer of the colon (two patients), uterus, kidney, bladder, and/or small intestine at ages 16, 24, 43, 44, 45, and 57, respectively. A patient with CRC at age 16 was found to carry the APC c.3183_3187del5 mutation as well as the MSH2 mutation, and it is inferred that her father, deceased of CRC at age 24, was also a double heterozygote.

INTERPRETATION

These results confirm that vigilance is required when interpreting molecular results for families with very young patients, as more than one gene may contribute to the genetic risk. Cancer screening measures must also be adapted to the earlier and more penetrant risk to double heterozygotes.

Denaturing high performance liquid chromatography for the detection of microsatellite instability using bethesda and pentaplex marker panels

Microsatellite instability (MSI) is a characteristic molecular phenotype of tumors from the hereditary nonpolyposis colorectal cancer (Lynch) syndrome. Routine MSI screening of tumors in younger patients is an efficient prescreening tool for the population-based detection of Lynch syndrome in the absence of family cancer history. We describe here the optimization of a denaturing high performance liquid chromatography (DHPLC) assay for MSI analysis with the "Bethesda" panel of markers recommended by the National Cancer Institute and with a more recently proposed "pentaplex" panel of 5 mononucleotide repeat markers. By using various polymerase chain reaction primers and tumor DNA samples with known MSI status, each of the 3 standard DHPLC formats tested could correctly identify the MSI status without the "stutter peaks" inherent in the capillary electrophoresis (CE) methods that are currently in use. Dilution experiments showed that the detection limit for MSI using DHPLC was at least 1:100, thus avoiding the need for tumor enrichment by microdissection before analysis. Concordance between CE and DHPLC for the detection of instability in the Bethesda panel markers was 95%. Optimal DHPLC running conditions for the pentaplex mononucleotide panel are also described. In conclusion, DHPLC provides a sensitive and specific alternative for routine MSI analysis that is free of the stutter peaks observed with CE and which can be used with either the Bethesda or pentaplex mononucleotide marker panels.