Lynch Syndrome - HNPCC


Lynch Syndrome or Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant disease characterised by early onset of colorectal cancer and increased risk of other malignancies including endometrial and renal cell carcinomas. HNPCC is associated with germline mutations of DNA mismatch repair genes, individuals who inherit HNPCC have an 80% lifetime risk of developing colorectal cancer.

In a study of 48 HNPCC kindreds (Liu et al, 1996) identified mutations in known mismatch repair genes;
31%: had mutations in the MSH2 gene
33%, had mutations in the MLH1 gene
2%, had mutations in the PMS1 gene
4% had mutations in the PMS2 gene

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

Tag cloud generated 29 August, 2019 using data from PubMed, MeSH and CancerIndex

Mutated Genes and Abnormal Protein Expression (17)

How to use this data tableClicking on the Gene or Topic will take you to a separate more detailed page. Sort this list by clicking on a column heading e.g. 'Gene' or 'Topic'.

MLH1 3p22.2 FCC2, COCA2, HNPCC, hMLH1, HNPCC2 Germline
-MLH1 and Lynch Syndrome
MSH2 2p21 FCC1, COCA1, HNPCC, LCFS2, HNPCC1 -MSH2 and Lynch Syndrome
MSH6 2p16 GTBP, HSAP, p160, GTMBP, HNPCC5 -MSH6 and Lynch Syndrome
PMS2 7p22.1 MLH4, PMSL2, HNPCC4, PMS2CL -PMS2 and Lynch Syndrome
PMS1 2q31.1 MLH2, PMSL1, hPMS1, HNPCC3 -PMS1 and Lynch Syndrome
MUTYH 1p34.1 MYH -MUTYH and Lynch Syndrome
MSH3 5q14.1 DUP, FAP4, MRP1 -MSH3 and Lynch Syndrome
TGFBR2 3p24.1 AAT3, FAA3, LDS2, MFS2, RIIC, LDS1B, LDS2B, TAAD2, TGFR-2, TGFbeta-RII -TGFBR2 and Lynch Syndrome
EPCAM 2p21 ESA, KSA, M4S1, MK-1, DIAR5, EGP-2, EGP40, KS1/4, MIC18, TROP1, EGP314, HNPCC8, TACSTD1 -EPCAM and Lynch Syndrome
MLH3 14q24.3 HNPCC7 -MLH3 and Lynch Syndrome
EXO1 1q43 HEX1, hExoI -EXO1 and Lynch Syndrome
BMPR1A 10q23.2 ALK3, SKR5, CD292, ACVRLK3, 10q23del -BMPR1A and Hereditary Nonpolyposis Colorectal Cancer (HNPCC)
POLD1 19q13.33 CDC2, MDPL, POLD, CRCS10 -POLD1 and Hereditary Nonpolyposis Colorectal Cancer (HNPCC)
PRINS 10p12.1 NCRNA00074 -PRINS and Lynch Syndrome
CASP5 11q22.3 ICH-3, ICEREL-III, ICE(rel)III -CASP5 and Lynch Syndrome
AIM2 1q23.1-q23.2 PYHIN4 -AIM2 and Lynch Syndrome
SEC63 6q21 ERdj2, SEC63L, DNAJC23, PRO2507 -SEC63 and Hereditary Nonpolyposis Colorectal Cancer (HNPCC)

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications

Gao XH, Zhang W, Liu LJ, Yan HL
[Comprehensive application of various screening strategies of Lynch syndrome].
Zhonghua Wei Chang Wai Ke Za Zhi. 2019; 22(7):684-688 [PubMed] Related Publications
Lynch syndrome (LS), which is the most common hereditary colorectal cancer, accounts for about 3% of all colorectal cancers. However, due to its various clinical manifestations, it is difficult to be diagnosed. The diagnosis of LS requires comprehensive application of various screening criteria (such as the Amsterdam criteria, Bethesda criteria), predictive models, risk factors, immunohistochemistry test of mismatch repair (MMR) protein, microsatellite instability (MSI) detection, MLH1 methylation detection, BRAF gene mutation detection, germline gene mutation detection, and so on. LS can be diagnosed only after the identification of pathogenic germline mutation of MMR gene. The first-degree and second-degree relatives of LS patients are recommended to be tested for the identified mutant gene. For LS patients and gene mutation carriers, LS associated cancer can be detected early or even prevented by monitoring and preventive surgery. Reproductive techniques can be used to prevent this disease from being passed down to the next generation.

Foretová L
Hereditary cancer syndromes, their testing and prevention.
Cas Lek Cesk. 2019; 158(1):15-21 [PubMed] Related Publications
About 5-10 % of cancer diseases may be caused by genetic predisposition, in ovarian cancer it could be almost 20 % of cases. The cause is mostly a pathogenic germline mutation in tumor suppressor genes, DNA repair genes, less frequently in oncogenes. So far, we know more than 200 hereditary cancer syndromes. The most frequently tested are hereditary breast and ovarian cancer syndrome, hereditary nonpolyposis colorectal cancer (Lynch syndrome), quite frequent are also hereditary gastrointestinal polyposes. Genetic counseling and testing are routinely available for patients or their relatives. Testing methods are changing; nowadays we use next generation sequencing methods (massive parallel sequencing) with testing of panels of high-risk genes. If the mutation is discovered, we may offer the testing to relatives. Genetic testing is indicated by medical geneticist after the genetic counseling session. High-risk individuals should be followed oncology clinics or by other specialists.

Liu Y, Wang M, Chen Q, et al.
A novel heterozygous large deletion of MSH6 gene in a Chinese family with Lynch syndrome.
Gene. 2019; 704:103-112 [PubMed] Related Publications
Lynch syndrome (LS) is a common cancer syndrome that is inherited in an autosomal dominant manner. Its pathogenesis is thought to be closely related to germline mutations of mismatch repair (MMR) genes such as the MLH1, MSH2, PMS2 and MSH6 genes. This study identifies a Chinese family with LS clinically diagnosed according to the Amsterdam II criteria. In these patients, immuno-histochemical staining showed negative MSH6 expressions but positive MLH1, MSH2, and PMS2 expressions. In order to further explore the molecular biology of this LS family, we used targeted next-generation sequencing (NGS) and Multiplex ligation dependent probe amplification (MLPA) to identify the mutation and verify the authenticity of the mutation in 15 family members. For NGS, two panels have been used, one is of MLH1, MSH2, PMS2 and MSH6 genes, the other one is of 139 cancer genetic susceptibility genes. And for the large deletions/duplications can also be identified by NGS panel, an adjusted data analysis strategy of NGS has been used. As a result, we identified a novel heterozygous large deletion in MSH6 gene that was found to be co-segregated among affected family members. This deletion results in the loss of a 3246 bp-sized fragment in MSH6 gene exons 5-9 which represents the coding regions of the MSH6 ATPase domain. This novel mutation has yet to be documented in the International Society for Gastrointestinal Hereditary Tumours (InSiGHT) database. This mutation resulted in MSH6 protein losing gene mismatch repair function, and further caused the microsatellite instable. We speculate that this mutation may significantly impact MMR function through impaired ATP domain function. Theoretically, this proband would likely benefit from PD-1 immune check-point blockade therapy, but conversely, we observed that tumors appeared to rapidly progress after 4 sessions of anti-PD-1 treatment. Further studies to validate the effectiveness of anti-PD-1 treatments in carriers of this mutation are necessary.

Cini G, Quaia M, Canzonieri V, et al.
Toward a better definition of EPCAM deletions in Lynch Syndrome: Report of new variants in Italy and the associated molecular phenotype.
Mol Genet Genomic Med. 2019; 7(5):e587 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Inherited epimutations of Mismatch Repair (MMR) genes are responsible for Lynch Syndrome (LS) in a small, but well defined, subset of patients. Methylation of the MSH2 promoter consequent to the deletion of the upstream EPCAM gene is found in about 1%-3% of the LS patients and represents a classical secondary, constitutional and tissue-specific epimutation. Several different EPCAM deletions have been reported worldwide, for the most part representing private variants caused by an Alu-mediated recombination.
METHODS: 712 patients with suspected LS were tested for MMR mutation in our Institute. EPCAM deletions were detected by multiplex ligation-dependent probe amplification (MLPA) and then defined by Long-Range polymerase chain reaction (PCR)/Sanger sequencing. A comprehensive molecular characterization of colorectal cancer (CRC) tissues was carried out by immunohistochemistry of MMR proteins, Microsatellite Instability (MSI) assay, methylation specific MLPA and transcript analyses. In addition, somatic deletions and/or variants were investigated by MLPA and next generation sequencing (NGS).
RESULTS: An EPCAM deletion was found in five unrelated probands in Italy: variants c.556-490_*8438del and c.858+1193_*5826del are novel; c.859-1430_*2033del and c.859-670_*530del were previously reported. All probands were affected by CRC at young age; tumors showed MSI and abnormal MSH2/MSH6 proteins expression. MSH2 promoter methylation, as well as aberrant in-frame or out-of-frame EPCAM/MSH2 fusion transcripts, were detected in CRCs and normal mucosae.
CONCLUSION: An EPCAM deletion was the causative variant in about 2% of our institutional series of 224 LS patients, consistent with previously estimated frequencies. Early age and multiple CRCs was the main clinical feature of this subset of patients.

Ito T, Yamaguchi T, Wakatsuki T, et al.
The single-base-pair deletion, MSH2 c.2635-3delC affecting intron 15 splicing can be a cause of Lynch syndrome.
Jpn J Clin Oncol. 2019; 49(5):477-480 [PubMed] Related Publications
The proband was a 62-year-old man with ureter cancer. He had a history of metachronous colorectal and gastric cancer. Immunohistochemical staining showed the absence of both MSH2 and MSH6 proteins in the ureter cancer and other available cancer tissue specimens. Genetic testing was conducted to identify the causative genes of hereditary gastrointestinal cancer syndromes including mismatch repair genes. We detected a germline variant, c.2635-3delC, within the splice acceptor site of exon 16, in the MSH2 gene. To investigate whether this variant affected splicing of the gene, RNA sequencing was performed using blood samples. We observed a substantial amount of the transcripts that lacked proper splicing of intron 15 in the indexed case, whereas, a very low amount of such aberrant transcripts was detected in the controls, strongly indicating an association between the variant and splicing defect. These results indicate that MSH2 c.2635-3delC affects normal splicing and might be a cause of Lynch syndrome.

Hajirawala L, Barton JS
Diagnosis and Management of Lynch Syndrome.
Dis Colon Rectum. 2019; 62(4):403-405 [PubMed] Related Publications
CASE SUMMARY: A 56-year-old man with a history of hypertension and hyperlipidemia was referred by gastroenterology for bleeding per rectum. Because of a family history of colon cancer, he had several prior colonoscopies, most recently 3 years ago, without evidence of pathology. His mother was diagnosed with colon cancer in her mid-40s. His current colonoscopy demonstrated a 2.4 × 1.5 cm cecal adenocarcinoma. Staging workup revealed no evidence of metastatic disease. Because of the patient's family history, the specimen was further evaluated and found to have high microsatellite instability (MSI-H). The patient was referred to a genetic counselor and found to have a germline pathogenic variant in MSH6 on gene panel testing. The patient did not have a family history of any extracolonic malignancies.The patient underwent an uncomplicated laparoscopic total abdominal colectomy with ileorectal anastomosis, which revealed a T2N0Mx adenocarcinoma with abundant peritumoral lymphocytes. He was discharged on postoperative day 2, and recuperated appropriately from surgery. Follow-up surveillance proctoscopy showed no evidence of disease. His sole offspring, a 25-year-old man, was negative for a pathogenic variant in MSH6 and had no polyps on colonoscopy. His siblings did demonstrate a pathogenic variant in MSH6 and are currently opting for annual surveillance colonoscopy.

Pandey AS, Shrestha S
A novel frameshift mutation in the
Indian J Cancer. 2018 Oct-Dec; 55(4):410-412 [PubMed] Related Publications
A novel mutation in the MLH1 gene likely to be pathogenic for Lynch syndrome was discovered in a proband with a family history of colon cancer. Immunohistochemistry showed negative expression of PMS2 and MLH1 in the resected tumor sample. The mutation lies at the highly conserved C-terminus of the MLH1 protein, the region through which it dimerizes with PMS2 to carry out its mismatch repair function.

Yamamoto A, Eguchi H, Suzuki O, et al.
[A Case of Cecal Cancer Associated with Preoperatively Diagnosed Lynch Syndrome Caused by EPCAM Deletion].
Gan To Kagaku Ryoho. 2018; 45(13):2202-2204 [PubMed] Related Publications
A 43-year-old woman underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy for endometrioid adenocarcinoma of the uterine body(Stage ⅢC)at 40 years of age. Screening of the adenocarcinoma samples for Lynch syndrome by immunohistochemistry for mismatch repair proteins indicated a loss of MSH2/MSH6 proteinexpression . A genetic test revealed a deletion of about 20 kb, including exons 8 and 9 of the EPCAM gene. Colonoscopy revealed a type 1 tumor in the cecum. The risk of developing metachronous colorectal cancer and postoperative survival according to the extent of colectomy(total colectomy versus segmental colectomy)and her marked obesity were considered collectively. The patient subsequently selected total colectomy with ileorectal anastomosis. Pathological findings revealed mucinous carcinoma(Stage Ⅱ). Patients with Lynch syndrome caused by deletion of EPCAM are not usually at a high risk of uterine body cancer, but the risk of developing uterine body cancer should be noted when the range of EPCAM deletion extends near to MSH2, as inthis case.

Sui QQ, Jiang W, Wu XD, et al.
A frameshift mutation in exon 19 of MLH1 in a Chinese Lynch syndrome family: a pedigree study.
J Zhejiang Univ Sci B. 2019 Jan.; 20(1):105-108 [PubMed] Free Access to Full Article Related Publications
Lynch syndrome (LS), an autosomal dominantly inherited disease previously known as hereditary non-polyposis colorectal cancer (HNPCC), leads to a high risk of colorectal cancer (CRC) as well as malignancy at certain sites including endometrium, ovary, stomach, and small bowel (Hampel et al., 2008; Lynch et al., 2009). Clinically, LS is considered the most common hereditary CRC-predisposing syndrome, accounting for about 3% of all CRC cases (Popat et al., 2005). LS is associated with mutations of DNA mismatch repair (MMR) genes such as MLH1, MSH2, MSH6, PMS2, and EPCAM (Ligtenberg et al., 2009; Lynch et al., 2009), which can trigger a high frequency of replication errors in both microsatellite regions and repetitive sequences in the coding regions of various cancer-related genes. Immunohistochemistry (IHC) tests followed by genetic analysis of these mutations play a significant role in diagnosis, treatment determination, and therapeutic response prediction of LS (Lynch et al., 2009; Alex et al., 2017; Ryan et al., 2017). Here, we report substitution of one base-pair in exon 1 of MLH3 (c.1397C>A) and a frameshift mutation in exon 19 of MLH1 (c.2250_2251ins AA) in a 43-year-old Chinese male with an LS pedigree.

Jin W, Wang LQ, Liu Y, Liu AJ
[Expression and clinical significance of MMR protein and MLH1 promoter methylation testing in endometrial cancer].
Zhonghua Fu Chan Ke Za Zhi. 2018; 53(12):823-830 [PubMed] Related Publications

Mäki-Nevala S, Valo S, Ristimäki A, et al.
DNA methylation changes and somatic mutations as tumorigenic events in Lynch syndrome-associated adenomas retaining mismatch repair protein expression.
EBioMedicine. 2019; 39:280-291 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: DNA mismatch repair (MMR) defects are a major factor in colorectal tumorigenesis in Lynch syndrome (LS) and 15% of sporadic cases. Some adenomas from carriers of inherited MMR gene mutations have intact MMR protein expression implying other mechanisms accelerating tumorigenesis. We determined roles of DNA methylation changes and somatic mutations in cancer-associated genes as tumorigenic events in LS-associated colorectal adenomas with intact MMR.
METHODS: We investigated 122 archival colorectal specimens of normal mucosae, adenomas and carcinomas from 57 LS patients. MMR-deficient (MMR-D, n = 49) and MMR-proficient (MMR-P, n = 18) adenomas were of particular interest and were interrogated by methylation-specific multiplex ligation-dependent probe amplification and Ion Torrent sequencing.
FINDINGS: Promoter methylation of CpG island methylator phenotype (CIMP)-associated marker genes and selected colorectal cancer (CRC)-associated tumor suppressor genes (TSGs) increased and LINE-1 methylation decreased from normal mucosa to MMR-P adenomas to MMR-D adenomas. Methylation differences were statistically significant when either adenoma group was compared with normal mucosa, but not between MMR-P and MMR-D adenomas. Significantly increased methylation was found in multiple CIMP marker genes (IGF2, NEUROG1, CRABP1, and CDKN2A) and TSGs (SFRP1 and SFRP2) in MMR-P adenomas already. Furthermore, certain CRC-associated somatic mutations, such as KRAS, were prevalent in MMR-P adenomas.
INTERPRETATION: We conclude that DNA methylation changes and somatic mutations of cancer-associated genes might serve as an alternative pathway accelerating LS-associated tumorigenesis in the presence of proficient MMR. FUND: Jane and Aatos Erkko Foundation, Academy of Finland, Cancer Foundation Finland, Sigrid Juselius Foundation, and HiLIFE.

Keränen A, Ghazi S, Carlson J, et al.
Testing strategies to reduce morbidity and mortality from Lynch syndrome.
Scand J Gastroenterol. 2018; 53(12):1535-1540 [PubMed] Related Publications
OBJECTIVE: Lynch syndrome (LS) has an autosomal dominant inheritance pattern and is associated with increased risk for colorectal cancer (CRC) and other cancers. Various strategies are used to identify patients at risk and offer surveillance and preventive programs, the cost effectiveness of which is much dependent on the prevalence of LS in a population. Universal testing (UT) is proposed as an effective measure, targeting all newly diagnosed CRC patients under a certain age.
MATERIALS AND METHODS: LS cases were identified in a cohort of 572 consecutive CRC patients. Immunohistochemistry was performed in 539 cases, using antibodies against mismatch repair proteins MLH1, PMS2, MSH2, and MSH6. Microsatellite instability and gene mutation screening were performed in 57 cases.
RESULTS: In total 11 pathogenic variants were detected, identifying LS in 1.9% of new CRC cases. Comparing the results with current clinical methods, 2 pathogenic variants were found with Amsterdam criteria and 9 when using either Bethesda guidelines or our institution's prior clinical criteria. Pathogenic variants in MSH6 were the most common in our series. We also found different outcomes using different age cut offs.
CONCLUSION: Our study demonstrates that UT of tumors before age on onset at 75 years would most likely be cost-efficient and essentially equivalent to applying the Bethesda guidelines or our institution's prior clinical criteria on all new CRC.

Adan F, Crijns MB, Dekker E, et al.
A squamous cell carcinoma in a young woman with Lynch syndrome.
Fam Cancer. 2019; 18(2):193-196 [PubMed] Related Publications
Lynch syndrome (LS) is an autosomal-dominant inherited disorder characterized by a predisposition to colorectal cancer and extracolonic cancers (particularly endometrium, ovary, stomach, small bowel, hepatobiliary tract, pancreas, urothelial tract, brain, and skin). Muir-Torre syndrome (MTS) is considered a phenotypical variant of LS, where patients develop sebaceous neoplasms and keratoacanthomas. Currently, only few studies and case reports suggest an association between LS and other skin cancers, such as Bowens' disease, melanoma and squamous cell carcinoma (SCC). In this case-report we describe the case of a 33-year-old woman with LS and a proven MSH2 germline mutation, presenting with a SCC on the right cheek. Immunohistochemistry lacked MSH2 and MSH6 protein staining. The tumor showed a discordance between immunohistochemistry and micro-satellite instability status, for which a clear explanation cannot be provided yet. To conclude whether this pattern is indicative for SCC occurring in LS patients, further analyses of other LS patients presenting with SCC should be carried out. Our patient's young age and skin type (Fitzpatrick phototype VI) suggest a possible link between LS and cutaneous SCC.

Buecher B, Le Mentec M, Doz F, et al.
[Constitutional MMR deficiency: Genetic bases and clinical implications].
Bull Cancer. 2019; 106(2):162-172 [PubMed] Related Publications
Inherited mono-allelic mutation in one of the 4 major MMR genes results in Lynch syndrome which predisposes, in adulthood, mainly to colorectal and endometrial tumors characterized by microsatellite instability (MSI phenotype). Individuals with bi-allelic mutations of one of these genes developed early and multiple malignancies, most often in childhood. This recessively inherited condition is named CMMRD for Constitutional Mismatch Repair Deficiency. The spectrum of tumors is distinct from Lynch syndrome. Malignant brain tumors are at least as frequent as gastrointestinal tumors and in more than a third of cases haematological malignancies were also reported. Patients also displayed clinical features similar of neurofibromatosis type 1, especially café au lait spots. The most commonly involved genes are PMS2 and MSH6 while bi-allelic MLH1 and MSH2 mutations are rare. The digestive tumors of these patients show MSI whereas the brain tumors can be "microsatellite stable". Because of variable clinical presentation and phenotypical overlaps with other cancer syndromes, CMMRD syndrome is frequently unrecognized by clinicians and its incidence is almost certainly underestimated. A better knowledge of clinical criteria and diagnosis methods should improve the identification of these patients at least at the time when they develop their first tumor or even before. This will allow adjusting treatment modalities and offering surveillance strategies of other tumor risks, not only for patients themselves but also for their relatives.

Battaglin F, Naseem M, Lenz HJ, Salem ME
Microsatellite instability in colorectal cancer: overview of its clinical significance and novel perspectives.
Clin Adv Hematol Oncol. 2018; 16(11):735-745 [PubMed] Related Publications
Microsatellite instability (MSI) is a key biomarker in colorectal cancer (CRC), with crucial diagnostic, prognostic, and predictive implications. Testing for mismatch repair deficiency (MMR-D)/MSI is recommended during screening for Lynch syndrome, an autosomal-dominant hereditary disease that is characterized by germline mutations in the MMR genes and associated with an increased risk for several types of cancer. Additionally, MSI-high (MSI-H) status is associated with a better prognosis in early-stage CRC and a lack of benefit from adjuvant treatment with 5-fluorouracil in stage II disease. More recently, MSI has emerged as a predictor of sensitivity to immunotherapy-based treatments. The groundbreaking success of checkpoint inhibitors in MMR-D metastatic CRC has opened a new therapeutic scenario for patients with these tumors. MSI-H CRC, in both the sporadic and hereditary settings, is characterized by distinctive molecular and clinicopathologic features and represents a unique subset of CRC that is the object of growing interest and fervent research efforts. This article, an overview of the expanding role of MSI in CRC, covers its clinical significance, the available data on molecular profiling, novel perspectives on MSI testing, biomarkers in MSI-H CRC, immunotherapy resistance, and novel immunotherapy strategies.

Kašubová I, Holubeková V, Janíková K, et al.
Next Generation Sequencing in Molecular Diagnosis of Lynch Syndrome - a Pilot Study Using New Stratification Criteria.
Acta Medica (Hradec Kralove). 2018; 61(3):98-102 [PubMed] Related Publications
The development of the new technologies such as the next-generation sequencing (NGS) makes more accessible the diagnosis of genetically heterogeneous diseases such as Lynch syndrome (LS). LS is one of the most common hereditary form of colorectal cancer. This autosomal dominant inherited disorder is caused by deleterious germline mutations in one of the mismatch repair (MMR) genes - MLH1, MSH2, MSH6 or PMS2, or the deletion in the EPCAM gene. These mutations eventually result in microsatellite instability (MSI), which can be easily tested in tumor tissue. According to the actual recommendations, all patients with CRC that are suspect to have LS, should be offered the MSI testing. When the MSI is positive, these patients should be recommended to genetic counseling. Here we report a pilot study about the application of NGS in the LS diagnosis in patients considered to have sporadic colorectal cancer. The inclusion criteria for the NGS testing were MSI positivity, BRAF V600E and MHL1 methylation negativity. We have used 5 gene amplicon based massive parallel sequencing on MiSeq platform. In one patient, we have identified a new pathogenic mutation in the exon 4 of the MSH6 gene that was previously not described in ClinVar, Human Gene Mutation Database, Ensembl and InSight databases. This mutation was confirmed by the Sanger method. We have shown that the implementation of new criteria for colorectal patients screening are important in clinical praxis and the NGS gene panel testing is suitable for routine laboratory settings.

Castro-Mujica MDC, Barletta-Carrillo C
[Lynch syndrome: genetic, clinical and diagnostic aspects].
Rev Gastroenterol Peru. 2018 Jul-Sep; 38(3):265-279 [PubMed] Related Publications
This review aims to present the genetic, clinical and diagnostic aspects of Lynch syndrome, as well as providing the most relevant information about genetic counseling in these patients and the current recommendations for their surveillance.

Pellat A, Netter J, Perkins G, et al.
[Lynch syndrome: What is new?]
Bull Cancer. 2019 Jul - Aug; 106(7-8):647-655 [PubMed] Related Publications
Lynch syndrome is a genetic condition defined by a germline mutation of an MMR (MisMatch Repair) gene leading to a defective DNA MMR system. Therefore, it is characterized by the predisposition to a spectrum of cancers, primarily colorectal cancer (CRC) and endometrial cancer (EC). Lynch syndrome-related CRC accounts for 3% of all CRC. Lynch syndrome also accounts for 2% of all EC. In case of Lynch syndrome, there is usually a familial history of cancer defined by the Amsterdam and Bethesda criteria. Diagnosis is made by tumor testing with (i) MMR immunohistochemistry and (ii) PCR for MSI (microsatellite instability), a genetic phenotype that characterizes these tumors. MSI can also be detected in sporadic tumors, through epigenetic events inactivating the MMR system. Progress in diagnosis and molecular biology has allowed for better identification of Lynch patients but also other rare genetic syndromes. MSI tumors can now benefit from new treatments such as immunotherapy which underlines the importance of their diagnosis. Finally, patients with Lynch syndrome as well as their relatives, undergo specific surveillance in order to prevent development of other cancers. This review will summarize the different aspects of Lynch syndrome and also focus on recent progress on the topic.

Jiang W, Cai MY, Li SY, et al.
Universal screening for Lynch syndrome in a large consecutive cohort of Chinese colorectal cancer patients: High prevalence and unique molecular features.
Int J Cancer. 2019; 144(9):2161-2168 [PubMed] Related Publications
The prevalence of Lynch syndrome (LS) varies significantly in different populations, suggesting that ethnic features might play an important role. We enrolled 3330 consecutive Chinese patients who had surgical resection for newly diagnosed colorectal cancer. Universal screening for LS was implemented, including immunohistochemistry for mismatch repair (MMR) proteins, BRAF

Dušek M, Hadravský L, Stehlík J, et al.
Results of morphological screening for Lynch syndrome during the period 2013-2016.
Cesk Patol. Summer 2018; 54(2):86-92 [PubMed] Related Publications
The introduction of a screening system for Lynch syndrome in pathology laboratories in Plzen yielded 24 diagnoses of Lynch syndrome during the period of 2013-2016, 20 of them presenting with colorectal cancer. In 8 of those 24 cases germline mutations of MMR genes, previously not recognized as pathogenic with certainty, were detected. Although the frequency of Lynch syndrome in patients with colorectal cancer was only 0.34 % in total, following introduction of the universal immunohistochemical investigation of MMR (mismatch repair) proteins expression in all colorectal cancers examined in Sikl´s Institute of Pathology the frequency per year in this department reached 2.4 %. The results favor universal immunohistochemical screening for Lynch syndrome in colorectal and endometrial cancer cases over a selective approach based on a combination of clinical and morphological criteria. Increased effectiveness of the universal approach is not brought about only by higher sensitivity of the immunohistochemical examination per se, but also by the possibility of automation of the process leading to increased adherence even of pathologists not directly engaged in Lynch syndrome management. However, the introduction of a nation-wide universal screening system requires support from the government and health insurance companies. Keywords: colorectal cancer - endometrial cancer - immunohistochemistry - Lynch syndrome - MMR - screening.

Moufid FZ, Bouguenouch L, El Bouchikhi I, et al.
Molecular and presymptomatic analysis of a Moroccan Lynch syndrome family revealed a novel frameshift MLH1 germline mutation.
Turk J Gastroenterol. 2018; 29(6):701-704 [PubMed] Free Access to Full Article Related Publications
Lynch syndrome (LS) is an autosomal dominant disorder characterized by an increased risk of extracolonic cancers and early age of onset. It is associated with germline mutations in the DNA mismatch repair (MMR) genes. We report a case of a patient with colorectal cancer referred to our medical genetics department for molecular analysis and genetic counseling. The proband is a 64-year-old woman diagnosed with a tumor of the cecum. Histopathological examination showed a moderately differentiated mucinous adenocarcinoma categorized by pT3 N0. Analysis of her pedigree revealed three siblings who had colon cancer, as well as one relative with brain cancer. Based on these findings, molecular genetic investigation was found to be necessary in order to identify the disease-causing mutation. Immunohistochemistry staining of MMR proteins was performed on the tumor sample of the index proband. Mutational analysis of the MLH1/MSH2 genes was carried out. Analysis was extended to the family members and the general population. This led to the identification of a heterozygous frameshift duplication in the MLH1 gene at position 910 (c.910dupG). Three siblings had inherited the mutation from their mother, two of whom were asymptomatic at the time of diagnosis. To the best of our knowledge, this is a novel pathogenic duplication that has not been reported in the databases and literature. The outcome of the present case suggests that this mutation was the primary cause of LS in the family.

Kamiza AB, Wang WC, You JF, et al.
Anticancer Res. 2018; 38(10):5983-5990 [PubMed] Related Publications
BACKGROUND/AIM: Epidermal growth factor receptor (EGFR), mothers against decapentaplegic homolog 7 (SMAD7) and transforming growth factor betta (TGFB) are crucial for colorectal cancer (CRC) tumorigenesis. This study investigated whether polymorphisms in EGFR, SMAD7, and TGFB are associated with CRC risk in patients with Lynch syndrome.
MATERIALS AND METHODS: Genotyping was performed using Sequenom iPLEX MassArray. Association between genetic polymorphisms and CRC was assessed using a weighted Cox proportional hazard model.
RESULTS: Patients carrying the AA genotype of EGFR rs2227983 had a significantly higher CRC risk than those carrying the G allele (HR=2.55, 95% CI=1.25-5.17). The dominant model of SMAD7 rs12953717 (CT + TT genotypes) significantly increased CRC risk (HR=2.17, 95% CI=1.12-4.16) when compared to the wild-type CC genotype. Similarly, the GG genotype of TGFBR2 rs6785358 significantly increased the risk of CRC (HR=21.1, 95% CI=5.06-88.1) compared to the AA genotype.
CONCLUSION: EGFR, SMAD7, and TGFBR2 are associated with CRC risk in patients with Lynch syndrome.

Gould GM, Grauman PV, Theilmann MR, et al.
Detecting clinically actionable variants in the 3' exons of PMS2 via a reflex workflow based on equivalent hybrid capture of the gene and its pseudogene.
BMC Med Genet. 2018; 19(1):176 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Hereditary cancer screening (HCS) for germline variants in the 3' exons of PMS2, a mismatch repair gene implicated in Lynch syndrome, is technically challenging due to homology with its pseudogene PMS2CL. Sequences of PMS2 and PMS2CL are so similar that next-generation sequencing (NGS) of short fragments-common practice in multigene HCS panels-may identify the presence of a variant but fail to disambiguate whether its origin is the gene or the pseudogene. Molecular approaches utilizing longer DNA fragments, such as long-range PCR (LR-PCR), can definitively localize variants in PMS2, yet applying such testing to all samples can have logistical and economic drawbacks.
METHODS: To address these drawbacks, we propose and characterize a reflex workflow for variant discovery in the 3' exons of PMS2. We cataloged the natural variation in PMS2 and PMS2CL in 707 samples and designed hybrid-capture probes to enrich the gene and pseudogene with equal efficiency. For PMS2 exon 11, NGS reads were aligned, filtered using gene-specific variants, and subject to standard diploid variant calling. For PMS2 exons 12-15, the NGS reads were permissively aligned to PMS2, and variant calling was performed with the expectation of observing four alleles (i.e., tetraploid calling). In this reflex workflow, short-read NGS identifies potentially reportable variants that are then subject to disambiguation via LR-PCR-based testing.
RESULTS: Applying short-read NGS screening to 299 HCS samples and cell lines demonstrated >99% analytical sensitivity and >99% analytical specificity for single-nucleotide variants (SNVs) and short insertions and deletions (indels), as well as >96% analytical sensitivity and >99% analytical specificity for copy-number variants. Importantly, 92% of samples had resolved genotypes from short-read NGS alone, with the remaining 8% requiring LR-PCR reflex.
CONCLUSION: Our reflex workflow mitigates the challenges of screening in PMS2 and serves as a guide for clinical laboratories performing multigene HCS. To facilitate future exploration and testing of PMS2 variants, we share the raw and processed LR-PCR data from commercially available cell lines, as well as variant frequencies from a diverse patient cohort.

Özdemir TR, Alan M, Sancı M, Koç A
Targeted Next-Generation Sequencing of
Balkan Med J. 2019; 36(1):37-42 [PubMed] Free Access to Full Article Related Publications
Background: Lynch syndrome is an inherited cancer disorder that causes an increased lifetime risk of various types of cancers. Endometrial cancer is the most common extracolonic cancer in Lynch syndrome. Guidelines recommend that patients with endometrial cancer younger than 50 years of age should be evaluated for Lynch syndrome. Molecular analysis of the mismatch repair genes and
Aims: To report the mutation analysis of mismatch repair genes using targeted next-generation sequencing in endometrial cancer diagnosed patients <50 years of age.
Study Design: Retrospective cross-sectional study.
Methods: Seventy-nine endometrial cancer diagnosed patients <50 years of age underwent genetic counseling. They were selected among 1094 consecutive endometrial cancer patients between 2006 and 2017. Molecular analysis of
Results: Germline testing of mismatch repair genes was performed in 79 endometrial cancer patients. Lynch syndrome was confirmed in 4 patients (5%; 4/79). A total of 14 variants (6 in
Conclusion: Lynch syndrome should be investigated in patients diagnosed with endometrial cancer that are less than 50 years of age due to the increased lifetime risk of developing cancer.

Buckley AR, Ideker T, Carter H, et al.
Exome-wide analysis of bi-allelic alterations identifies a Lynch phenotype in The Cancer Genome Atlas.
Genome Med. 2018; 10(1):69 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Cancer susceptibility germline variants generally require somatic alteration of the remaining allele to drive oncogenesis and, in some cases, tumor mutational profiles. Whether combined germline and somatic bi-allelic alterations are universally required for germline variation to influence tumor mutational profile is unclear. Here, we performed an exome-wide analysis of the frequency and functional effect of bi-allelic alterations in The Cancer Genome Atlas (TCGA).
METHODS: We integrated germline variant, somatic mutation, somatic methylation, and somatic copy number loss data from 7790 individuals from TCGA to identify germline and somatic bi-allelic alterations in all coding genes. We used linear models to test for association between mono- and bi-allelic alterations and somatic microsatellite instability (MSI) and somatic mutational signatures.
RESULTS: We discovered significant enrichment of bi-allelic alterations in mismatch repair (MMR) genes and identified six bi-allelic carriers with elevated MSI, consistent with Lynch syndrome. In contrast, we find little evidence of an effect of mono-allelic germline variation on MSI. Using MSI burden and bi-allelic alteration status, we reclassify two variants of unknown significance in MSH6 as potentially pathogenic for Lynch syndrome. Extending our analysis of MSI to a set of 127 DNA damage repair (DDR) genes, we identified a novel association between methylation of SHPRH and MSI burden.
CONCLUSIONS: We find that bi-allelic alterations are infrequent in TCGA but most frequently occur in BRCA1/2 and MMR genes. Our results support the idea that bi-allelic alteration is required for germline variation to influence tumor mutational profile. Overall, we demonstrate that integrating germline, somatic, and epigenetic alterations provides new understanding of somatic mutational profiles.

Signoroni S, Tibiletti MG, Ricci MT, et al.
Performance of tumor testing for Lynch syndrome identification in patients with colorectal cancer: A retrospective single-center study.
Tumori. 2019; 105(1):76-83 [PubMed] Related Publications
OBJECTIVE:: To investigate the performance of tumor testing approaches in the identification of Lynch syndrome (LS) in a single-center cohort of people with colorectal cancer (CRC).
METHODS:: A retrospective analysis of data stored in a dedicated database was carried out to identify patients with CRC suspected for LS who were referred to Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy, between 1999 and 2014. The sensitivity and specificity of immunohistochemistry (IHC) for mismatch repair (MMR) proteins and microsatellite instability (MSI) analysis (alone or combined) were calculated with respect to the presence of causative MMR germline variants.
RESULTS:: A total of 683 patients with CRC suspected for LS were identified. IHC results of MMR protein analysis and MSI were assessed in 593 and 525 CRCs, respectively, while germline analysis was performed in 418 patients based on the IHC or MSI test result and/or clinical features. Univariate and multivariate analysis revealed a significant correlation of pathogenic MMR germline variants with all clinicopathologic features including Amsterdam criteria, presence of endometrial cancer, CRC site, age at onset, stage, and grade. The highest odds ratio values were observed for IHC and MSI (17.1 and 8.8, respectively). The receiver operating characteristic curve and area under the curve values demonstrated that IHC alone or combined with other clinicopathologic parameters was an excellent test for LS identification.
CONCLUSIONS:: This study confirms the effectiveness of tumor testing to identify LS among patients with CRC. Although IHC and MSI analysis were similarly effective, IHC could be a better strategy for LS identification as it is less expensive and more feasible.

Goverde A, Wagner A, Bruno MJ, et al.
Routine Molecular Analysis for Lynch Syndrome Among Adenomas or Colorectal Cancer Within a National Screening Program.
Gastroenterology. 2018; 155(5):1410-1415 [PubMed] Related Publications
BACKGROUND & AIMS: It is important to identify individuals with Lynch syndrome because surveillance programs can reduce their morbidity and mortality from colorectal cancer (CRC). We assessed the diagnostic yield of immunohistochemistry to detect Lynch syndrome in patients with advanced and multiple adenomas within our national CRC screening program.
METHODS: We performed a prospective study of all participants (n = 1101; 55% male; median age, 66 years; interquartile range, 61-70 years) referred to the Erasmus MC in The Netherlands after a positive result from a fecal immunohistochemical test, from December 2013 to December 2016. Colon tissues were collected from patients with advanced adenomas, ≥4 nonadvanced adenomas, or CRC, and analyzed by immunohistochemistry to identify patients with loss of mismatch repair (MMR) proteins (MLH1, MSH2, MSH6, or PMS2): a marker of Lynch syndrome. Specimens from patients with loss of MLH1 were analyzed for MLH1 promoter hypermethylation. Patients with an MMR-deficient tumor or adenoma without MLH1 promoter hypermethylation were referred for genetic analysis.
RESULTS: At colonoscopy, 456 patients (41%) (65% male; mean age, 67 years; interquartile range, 63-71 years) were found to have CRC and/or an adenoma eligible for analysis by immunohistochemistry. Of 56 CRCs, 7 (13%) had lost an MMR protein and 5 had hypermethylation of the MLH1 promoter. Analyses of tumor DNA revealed that 2 patients without MLH1 promoter hypermethylation had developed sporadic tumors. In total, 400 patients with adenomas were analyzed. Of the examined adenomas, 208 (52%) had a villous component and/or high-grade dysplasia: 186 (47%) had a villous component and 41 (10%) had high-grade dysplasia. Only 1 adenoma had lost an MMR protein. This adenoma was found to have 2 somatic mutations in MSH6.
CONCLUSIONS: In a CRC screening program in The Netherlands for individuals aged 55 to 75 years, routine screening for Lynch syndrome by immunohistochemistry analysis of colon tissues from patients with advanced and multiple adenomas identified no individuals with this genetic disorder.

Arakawa K, Hata K, Kawai K, et al.
Predictors for High Microsatellite Instability in Patients with Colorectal Cancer Fulfilling the Revised Bethesda Guidelines.
Anticancer Res. 2018; 38(8):4871-4876 [PubMed] Related Publications
BACKGROUND: The revised Bethesda guidelines (rBG) are generally used for screening of Lynch syndrome, and few researchers have investigated the associations between microsatellite instability (MSI) status and each item of the rBG.
PATIENTS AND METHODS: This retrospective study included patients with colorectal cancer who were classified into those fulfilling the rBG (Bethesda group) and those not (control group). The breakdown of each item in the rBG and predictors of high MSI (MSI-H) were determined in the Bethesda group.
RESULTS: Of 809 consecutive patients, 161 (19.9%) were found to fulfil the rBG criteria. As a predictor of MSI-H, items 2 or 5 of the rBG showed a sensitivity of 93.3%. Item 5 and right-sided tumour location were independent predictors of MSI-H in patients fulfilling the rBG (odds ratio(OR)=4.49 and 25.1; p=0.0260 and <0.0001, respectively).
CONCLUSION: Item 5 of the rBG and right-sided tumour location are significant predictors of MSI-H.

Kayser K, Degenhardt F, Holzapfel S, et al.
Copy number variation analysis and targeted NGS in 77 families with suspected Lynch syndrome reveals novel potential causative genes.
Int J Cancer. 2018; 143(11):2800-2813 [PubMed] Related Publications
In many families with suspected Lynch syndrome (LS), no germline mutation in the causative mismatch repair (MMR) genes is detected during routine diagnostics. To identify novel causative genes for LS, the present study investigated 77 unrelated, mutation-negative patients with clinically suspected LS and a loss of MSH2 in tumor tissue. An analysis for genomic copy number variants (CNV) was performed, with subsequent next generation sequencing (NGS) of selected candidate genes in a subgroup of the cohort. Genomic DNA was genotyped using Illumina's HumanOmniExpress Bead Array. After quality control and filtering, 25 deletions and 16 duplications encompassing 73 genes were identified in 28 patients. No recurrent CNV was detected, and none of the CNVs affected the regulatory regions of MSH2. A total of 49 candidate genes from genomic regions implicated by the present CNV analysis and 30 known or assumed risk genes for colorectal cancer (CRC) were then sequenced in a subset of 38 patients using a customized NGS gene panel and Sanger sequencing. Single nucleotide variants were identified in 14 candidate genes from the CNV analysis. The most promising of these candidate genes were: (i) PRKCA, PRKDC, and MCM4, as a functional relation to MSH2 is predicted by network analysis, and (ii) CSMD1, as this is commonly mutated in CRC. Furthermore, six patients harbored POLE variants outside the exonuclease domain, suggesting that these might be implicated in hereditary CRC. Analyses in larger cohorts of suspected LS patients recruited via international collaborations are warranted to verify the present findings.

Hissong E, Crowe EP, Yantiss RK, Chen YT
Assessing colorectal cancer mismatch repair status in the modern era: a survey of current practices and re-evaluation of the role of microsatellite instability testing.
Mod Pathol. 2018; 31(11):1756-1766 [PubMed] Related Publications
Results of DNA mismatch repair testing are used to detect Lynch syndrome and have prognostic and therapeutic implications among patients with sporadic colorectal carcinomas. Immunohistochemistry for mismatch repair proteins (MLH1, PMS2, MSH2, MSH6) and PCR for microsatellite instability are two established methods for assessing mismatch repair function. Older literature suggested a discordance rate of approximately 5% between these assays, leading some institutions to perform dual testing on all cases. Although universal mismatch repair testing is now recommended by multiple professional organizations, none provide guidelines regarding preferred assays. We surveyed 96 academic and nonacademic institutions to assess Lynch syndrome screening practices and evaluated discordance rates between immunohistochemistry and PCR among 809 colorectal cancers tested in our own institution. Our survey demonstrated no significant differences between academic and nonacademic practices with respect to testing strategies. Eighty six percent performed universal screening, and usually (76%) employed immunohistochemistry on initial biopsy samples. Only 20% employed PCR; these were mostly academic practices that used both immunohistochemistry and PCR (p < 0.01 compared with the nonacademic groups). Loss of MLH1/PMS2 staining was often (90%) followed by either BRAF mutational analysis or MLH1 methylation assays. Only 24% adhered to WHO recommendations to assign histologic grade based on mismatch repair status. We found only 3 cases (0.4%) with discordant immunohistochemistry and PCR results in our own practice: 1 reflected decreased MSH-6 staining in a neoadjuvantly treated microsatellite stable tumor, 1 MLH1-deficient tumor showed diminished MLH1/PMS2 in the tumor compared with internal control, and 1 case reflected an error in the molecular laboratory. Overall, our results showed extremely low discordance between methods assessing mismatch repair status and would suggest immunohistochemistry as the preferred single screening test. PCR can be reserved for cases that show equivocal immunostaining patterns.

Further References

Lynch HT, Lynch PM
The cancer-family syndrome: a pragmatic basis for syndrome identification.
Dis Colon Rectum. 1979; 22(2):106-10 [PubMed] Related Publications
We report a family manifesting the cancer-family syndrome in which 11 family members had colonic carcinomas (predominantly involving the proximal colon, in the absence of polyposis), with an average age at onset of 35 years. Three women had endometrial or endocervical cancers. The kindred is notable in that its full evaluation was predicated upon the recognition of features consistent with the cancer-family syndrome in only two sisters. The ascertainment and evaluation of the kindred demonstrates the clinical utility of regarding such criteria (early cancer onset, multiple primary cancers, proximal colonic involvement) as a basis for selecting cases for more thorough family-history evaluation. Although such selection criteria are not pathognomonic for the syndrome, identification of a more extensive family cancer history sometimes enables the initiation of a highly specific cancer surveillance program. Specific attention has been given to the problems of screening patients at risk for the development of proximal colonic cancer, an important feature of the cancer-family syndrome. Innovative operative management is also indicated, such as total colectomy for initial colonic cancer, and consideration of prophylactic hysterectomy for women with colonic cancer (because of the high risk of development of endometrial carcinoma).

Lynch HT, Lynch J
Lynch syndrome: genetics, natural history, genetic counseling, and prevention.
J Clin Oncol. 2000; 18(21 Suppl):19S-31S [PubMed] Related Publications
Lynch syndrome is the most common hereditary form of colorectal cancer (CRC). Its natural history has been investigated extensively, so that highly targeted surveillance and management strategies, melded to its natural history, have proven effective in cancer control. Most important is the early age of onset of cancer (approximately 44 years), involving CRC and the several extracolonic cancers that are integral to the syndrome. With respect to CRC, approximately 70% of cases occur proximal to the splenic flexure. Synchronous and metachronous CRCs are extremely common. Full colonoscopy should be initiated when the patient is between the ages of 20 and 25, and because of the accelerated carcinogenesis of CRC, it should be performed every 1 to 2 years. The presence of initial CRC requires subtotal colectomy, given the mentioned increased frequency of metachronous cancer. Options available for germ-line mutation carriers, in addition to cancer screening, include prophylactic colectomy as well as prophylactic total abdominal hysterectomy and bilateral salpingo-oophorectomy. The discovery of mismatch repair germ-line mutations (most commonly MSH2 or MLH1) has added significantly to the recognition of this disease as well as to the search for high-risk individuals throughout families who, with genetic counseling, may become candidates for germ-line mutation testing. Clearly, hereditary nonpolyposis colorectal cancer provides an excellent opportunity for learning about the etio-pathogenesis of cancer at the molecular and clinical levels and how this knowledge might ultimately be exploited for cancer control. A search for chemoprevention agents, such as cyclo-oxygenase 2 inhibitors, as well as for putative environmental effects and how they may interact with the genetic component in CRC etiology should abet this entire cancer control process.

Lynch HT, Lynch JF
Hereditary nonpolyposis colorectal cancer.
Semin Surg Oncol. 2000; 18(4):305-13 [PubMed] Related Publications
Hereditary nonpolyposis colorectal cancer (HNPCC), or Lynch syndrome, is the most common form of hereditary colorectal cancer (CRC). A well-orchestrated cancer family history is essential for its diagnosis since, unlike its familial adenomatous polyposis (FAP) hereditary cancer counterpart, HNPCC lacks distinguishing clinical stigmata of its cancer genetic risk. Discoveries in the 1990s of germ-line mutations, the most common of which are hMSH2 and hMLH1, have added enormous power to the diagnosis of Lynch syndrome. Its medical management is contingent upon its natural history. For example, approximately 70% of CRCs occur proximal to the splenic flexure, with one-third of the cancers occurring in the cecum, thereby mandating full colonoscopy. A high rate of metachronous CRCs indicates the need for no less than a subtotal colectomy for the management of initial CRC. Genetic counseling is essential prior to DNA testing, and at the time of disclosure of the results. Education of patients as well as physicians about all facets of this disorder is extremely important. If patients are to show compliance with germ-line testing, screening, and management options, they must understand the natural history and the significance of their genetic risk status. Physicians must also be aware of clinical nuances of this disorder to provide the necessary care.

Liu B, Parsons R, Papadopoulos N, et al.
Analysis of mismatch repair genes in hereditary non-polyposis colorectal cancer patients.
Nat Med. 1996; 2(2):169-74 [PubMed] Related Publications
Hereditary non-polyposis colorectal cancer (HNPCC) is an autosomal dominant disorder characterized by the early onset of colorectal cancer and linked to germline defects in at least four mismatch repair genes. Although much has been learned about the molecular pathogenesis of this disease, questions related to effective presymptomatic diagnosis are largely unanswered because of its genetic complexity. In this study, we evaluated tumors from 74 HNPCC kindreds for genomic instability characteristic of a mismatch repair deficiency and found such instability in 92% of the kindreds. The entire coding regions of the five known human mismatch repair genes were evaluated in 48 kindreds with instability, and mutations were identified in 70%. This study demonstrates that a combination of techniques can be used to genetically diagnose tumor susceptibility in the majority of HNPCC kindreds and lays the foundation for genetic testing of this relatively common disease.

Wang Q, Lasset C, Desseigne F, et al.
Prevalence of germline mutations of hMLH1, hMSH2, hPMS1, hPMS2, and hMSH6 genes in 75 French kindreds with nonpolyposis colorectal cancer.
Hum Genet. 1999 Jul-Aug; 105(1-2):79-85 [PubMed] Related Publications
Hereditary nonpolyposis colorectal cancer (HNPCC) is a syndrome characterized by familial predisposition to colorectal carcinoma and extracolonic cancers of the gastrointestinal, urological, and female reproductive tracts. This dominant disorder is caused by germline defects in one of at least five DNA mismatch repair (MMR) genes: hMLH1, hMSH2, hPMS1, hPMS2, and hMSH6 (GTBP). Germline mutations of hMSH2 and hMLH1 are also frequently identified in families not fulfilling all the Amsterdam criteria, thereby demonstrating that the involvement of these genes is not confined to typical HNPCC. To evaluate the respective involvement of the various MMR genes in typical and incomplete HNPCC syndromes, we have performed an analysis of the hMLH1, hMSH2, hPMS1, hPMS2, and hMSH6 genes in a large series of French kindreds (n=75) with colorectal tumors and/or aggregation of extracolonic cancers belonging to the HNPCC spectrum. Mutational analysis has been performed in all families, without preselection for the tumor phenotype. We have detected 26 pathogenic germline mutations of the hMLH1 and hMSH2 genes and several novel variants of the hPMS1, hPMS2, and hMSH6 genes. Our data confirm that, regardless of the type of families and the tumor phenotype, hPMS1, hPMS2, and hMSH6 germline mutations are rare in familial aggregation of colorectal cancers. Furthermore, they suggest that the presence of multiple primary malignancies in a single individual and the observation of extracolonic tumors in relatives of a colorectal cancer patient should be included among the guidelines for referring patients for genetic testing.

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