Prognostic impact of mismatch repair genes germline defects in colorectal cancer patients: are all mutations equal?

Background

Lynch syndrome (LS) is the most common hereditary colorectal cancer (CRC) syndrome, caused by germline mutations in MisMatch Repair (MMR) genes, particularly in MLH1, MSH2 and MSH6. Patients with LS seem to have a more favourable prognosis than those with sporadic CRC, although the prognostic impact of different mutation types is unknown.Aim of our study is to compare survival outcomes of different types of MMR mutations in patients with LS-related CRC.

Methods

302 CRC patients were prospectively selected on the basis of Amsterdam or Revised Bethesda criteria to undergo genetic testing: direct sequencing of DNA and MLPA were used to examine the entire MLH1, MSH2 and MSH6 coding sequence.Patients were classified as mutation-positive or negative according to the genetic testing result.

Results

A deleterious MMR mutation was found in 38/302 patients. Median overall survival (OS) was significantly higher in mutation-positive vs mutation-negative patients (102.6 vs 77.7 months, HR:0.63, 95%CI:0.46–0.89, p = 0.0083). Different types of mutation were significantly related with OS: missense or splicing-site mutations were associated with better OS compared with rearrangement, frameshift or non-sense mutations (132.5 vs 82.5 months, HR:0.46, 95%CI:0.16–0.82, p = 0.0153).

Conclusions

Our study confirms improved OS for LS-patients compared with mutation-negative CRC patients. In addition, not all mutations could be considered equal: the better prognosis in CRC patients with MMR pathogenic missense or splicing site mutation could be due to different functional activity of the encoded MMR protein. This matter should be investigated by use of functional assays in the future.     

Cancer risk in MLH1, MSH2 and MSH6 mutation carriers; different risk profiles may influence clinical management

Background

Lynch syndrome (LS) is associated with a high risk for colorectal cancer (CRC) and extracolonic malignancies, such as endometrial carcinoma (EC). The risk is dependent of the affected mismatch repair gene. The aim of the present study was to calculate the cumulative risk of LS related cancers in proven MLH1, MSH2 and MSH6 mutation carriers.

Methods

The studypopulation consisted out of 67 proven LS families. Clinical information including mutation status and tumour diagnosis was collected. Cumulative risks were calculated and compared using Kaplan Meier survival analysis.

Results

MSH6 mutation carriers, both males and females had the lowest risk for developing CRC at age 70 years, 54% and 30% respectively and the age of onset was delayed by 3-5 years in males. With respect to endometrial carcinoma, female MSH6 mutation carriers had the highest risk at age 70 years (61%) compared to MLH1 (25%) and MSH2 (49%). Also, the age of EC onset was delayed by 5-10 years in comparison with MLH1 and MSH2.

Conclusions

Although the cumulative lifetime risk of LS related cancer is similar, MLH1, MSH2 and MSH6 mutations seem to cause distinguishable cancer risk profiles. Female MSH6 mutation carriers have a lower CRC risk and a higher risk for developing endometrial carcinoma. As a consequence, surveillance colonoscopy starting at age 30 years instead of 20-25 years is more suitable. Also, prophylactic hysterectomy may be more indicated in female MSH6 mutation carriers compared to MLH1 and MSH2 mutation carriers.     

Target gene mutational pattern in Lynch syndrome colorectal carcinomas according to tumour location and germline mutation

Background:

We previously reported that the target genes in sporadic mismatch repair (MMR)-deficient colorectal carcinomas (CRCs) in the distal colon differ from those occurring elsewhere in the colon. This study aimed to compare the target gene mutational pattern in microsatellite instability (MSI) CRC from Lynch syndrome patients stratified by tumour location and germline mutation, as well as with that of sporadic disease.

Methods:

A series of CRC from Lynch syndrome patients was analysed for MSI in genes predicted to be selective MSI targets and known to be involved in several pathways of colorectal carcinogenesis.

Results:

The most frequently mutated genes belong to the TGF-β superfamily pathway, namely ACVR2A and TGFBR2. A significantly higher frequency of target gene mutations was observed in CRC from patients with germline mutations in MLH1 or MSH2 when compared with MSH6. Mutations in microsatellite sequences (A)7 of BMPR2 and (A)8 of MSH3 were significantly more frequent in the distal CRC. Additionally, we observed differences in MSH3 and TGFBR2 mutational frequency between Lynch syndrome and sporadic MSI CRC regarding tumour location.

Conclusions:

Our results indicate that the pattern of genetic changes differs in CRC depending on tumour location and between Lynch syndrome and sporadic MSI CRC, suggesting that carcinogenesis can occur by different pathways even if driven by generalised MSI.     

Microsatellite instability, immunohistochemistry, and additional PMS2 staining in suspected hereditary nonpolyposis colorectal cancer.

PURPOSE: Immunohistochemistry (IHC) and microsatellite instability (MSI) analysis can be used to identify patients with a possible DNA mismatch repair defect [hereditary nonpolyposis colorectal carcinoma (HNPCC)]. The Bethesda criteria have been proposed to select families for determination of MSI. The aims of this study were to assess the yield of MSI analysis in families suspected for HNPCC, to compare the results of immunohistochemical staining and MSI analysis, and to assess the additional value of PMS2 staining. EXPERIMENTAL DESIGN: Clinical data and tumors were collected from 725 individuals from 631 families with suspected HNPCC. MSI analysis was performed using eight markers including the 5 National Cancer Institute markers. Four immunohistochemical staining antibodies were used (MLH1, MSH2, MSH6 and PMS2). RESULTS: A MSI-H (tumors with instability for >30% of the markers) phenotype in colorectal cancers (CRCs) was observed in 21-49% of families that met the various Bethesda criteria. In families with three cases of CRC diagnosed at age > 50 years, families with a solitary case of CRC diagnosed between ages 45 and 50 years, and families with one CRC case and a first-degree relative with a HNPCC-related cancer, one diagnosed between ages 45 and 50 years (all Bethesda-negative families), the yield of MSI-H was 10-26%. Immunohistochemical staining confirmed the MSI results in 93% of the cases. With IHC, adding PMS2 staining led to the identification of an additional 23% of subjects with an hMLH1 germ-line mutation (35 carriers were tested). CONCLUSIONS: The Bethesda guidelines for MSI analysis should include families with three or more cases of CRC diagnosed at age > 50 years. The age at diagnosis of CRC in the original guidelines should be raised to 50 years. Routine IHC diagnostics for HNPCC should include PMS2 staining.     

Detection of DNA mismatch repair proteins in fresh human blood lymphocytes - towards a novel method for hereditary non-polyposis colorectal cancer (Lynch syndrome) screening

Background

A broad population-based assay to detect individuals with Lynch Syndrome (LS) before they develop cancer would save lives and healthcare dollars via cancer prevention. LS is caused by a germline mutation in a DNA mismatch repair (MMR) gene, especially protein truncation-causing mutations involving MSH2 or MLH1. We showed that immortalized lymphocytes from LS patients have reduced levels of full-length MLH1 or MSH2 proteins. Thus, it may be feasible to identify LS patients in a broad population-based assay by detecting reduced levels of MMR proteins in lymphocytes.

Methods

Accordingly, we determined whether MSH2 and MLH1 proteins can also be detected in fresh lymphocytes. A quantitative western blot assay was developed using two commercially available monoclonal antibodies that we showed are specific for detecting full-length MLH1 or MSH2. To directly determine the ratio of the levels of these MMR proteins, we used both antibodies in a multiplex-type western blot.

Results

MLH1 and MSH2 levels were often not detectable in fresh lymphocytes, but were readily detectable if fresh lymphocytes were first stimulated with PHA. In fresh lymphocytes from normal controls, the MMR ratio was ~1.0. In fresh lymphocytes from patients (N > 50) at elevated risk for LS, there was a bimodal distribution of MMR ratios (range: 0.3-1.0).

Conclusions

Finding that MMR protein levels can be measured in fresh lymphocytes, and given that cells with heterozygote MMR mutations have reduced levels of full-length MMR proteins, suggests that our immunoassay could be advanced to a quantitative test for screening populations at high risk for LS.     

Tumours with loss of MSH6 expression are MSI-H when screened with a pentaplex of five mononucleotide repeats

Background:

Microsatellite instability (MSI) is commonly screened using a panel of two mononucleotide and three dinucleotide repeats as recommended by a consensus meeting on MSI tumours held at the National Cancer Institute (Bethesda, MD, USA). According to these recommendations, tumours are classified as MSI-H when at least two of the five microsatellite markers show instability, MSI-L when only one marker shows instability and MSS when none of the markers show instability. Almost all MSI-H tumours are characterised by alterations in one of the four major proteins of the mismatch repair (MMR) system (MLH1, MSH2, MSH6 or PMS2) that renders them MMR deficient, whereas MSI-L and MSS tumours are generally MMR proficient. However, tumours from patients with a pathogenic germline mutation in MSH6 can sometimes present an MSI-L phenotype with the NCI panel. The MSH6 protein is not involved in the repair of mismatches of two nucleotides in length and consequently the three dinucleotide repeats of the NCI panel often show stability in MSH6-deficient tumours.

Methods:

A pentaplex panel comprising five mononucleotide repeats has been recommended as an alternative to the NCI panel to determine tumour MSI status. Several studies have confirmed the sensitivity, specificity and ease of use of the pentaplex panel; however, its sensitivity for the detection of MSH6-deficient tumours is so far unknown. Here, we used the pentaplex panel to evaluate MSI status in 29 tumours known to harbour an MSH6 defect.

Results:

MSI-H status was confirmed in 15 out of 15 (100%) cases where matching normal DNA was available and in 28 out of 29 (97%) cases where matching DNA was not available or was not analysed.

Conclusion:

These results show that the pentaplex assay efficiently discriminates the MSI status of tumours with an MSH6 defect.     

筛查结直肠癌DNA错配修复基因缺失的方法分析

目的:通过对筛查结直肠癌DNA错配修复(mismatch repair,MMR)基因缺失两种最常用的检测方法的分析,寻找更为经济有效的检测策略。方法:分析新疆医科大学第一附属医院2018年9月至2019年9月收治并行手术的结直肠癌患者的肿瘤组织223例,采用免疫组织化学法检测平台检测MLH1、MSH2、PMS2、MSH6的表达缺失情况,PCR-毛细管电泳法检测肿瘤微卫星不稳定(microstatellites instability,MSI)状态。结果:在223例结直肠癌中,27例(12.1%)MMR蛋白表达缺失(MMR deficiency,dMMR),196例(87.9%)MMR蛋白表达完整(MMR proficient,pMMR)。MLH1、MSH2、MSH6和PMS2的缺失率分别为9.0%(20/223)、1.8%(4/223)、2.7%(6/223)和9.4%(21/223)。包含PMS2和MSH6的2种抗体试验筛查dMMR结直肠癌的灵敏度和特异度与4种抗体试验(MLH1、MSH2、PMS2、MSH6)的灵敏度和特异度均相同。微卫星高度不稳定(MSI-high,MSI-H)27例(12.1%),微卫星稳定(microsatellite stable,MSS)196例(87.9%),无微卫星低度不稳定(MSI-low,MSI-L)。BAT-25、BAT-26、NR-21、NR-24、NR-27、MONO-27共6个位点的灵敏度分别为88.9%、92.6%、96.3%、70.4%、92.6%、77.8%。将MSI定义为3种标记(NR-21、NR-27、BAT-26)至少有1处不稳定时,得出的结果与6种标记组(BAT-25、BAT-26、NR-21、NR-24、NR-27、MONO-27)完全相同。结论:简化的两种检测方案为结直肠癌dMMR/MSI的鉴定提供了更为简便、可靠、价格低廉的方法。     

Simplified MSI marker panel for diagnosis of colorectal cancer

Background: Colorectal cancers (CRCs) tumors are diagnosed by microsatellite instability (MSI) due to accumulation of insertion/deletion mutations in tandem repeats of short DNA motifs (1–6 bp) called microsatellites. Microsatellite instability (MSI) is not only a hallmark marker for screening of hereditary nonpolyposis colorectal cancer (HNPCC), but also a prognostic and predictive marker for sporadic colorectal cancer. Our objective was to determine and study of five mononucleotide microsatellite markers status among Iranian patients with HNPCC and sporadic colorectal cancer. Material and Methods: In the current investigation 80 sporadic CRC and 80 HNPCC patients were evaluated for MSI. The pentaplex panel including 5 quasimonomorphic mononucleotide repeats (NR-21, BAT-26, BAT-25, NR-27 and NR-24) was used. Results: Our findings showed that the NR-21 was the most frequent instable marker among the other markers. 53% and 25.6% specimens had instability in sporadic CRC and HNPCC, respectively. Furthermore, the frequencies of instability BAT-25 was determined in 20% sporadic CRC and 23% HNPCC samples. Interestingly our results demonstrated that the frequency of instability NR-24 was similar 20% sporadic CRC and 20.5% HNPCC. Moreover, percentage of NR-27 in HNPCC was 19.2 and 0% in sporadic CRC. Finally, BAT-26 was instable in 21.8% HNPCC patients while we could find 6.6% instability for BAT-26 in sporadic cases. Conclusion: It seems that among 5 mononucleotides markers NR-21 was the most useful marker for diagnosis HNPCC and sporadic cancer. Following NR-21, BAT-25 and NR-24 are the most reliable markers. Therefore using a triplex panel including 3 aforementioned MSI markers should be more promising markers for identifying MSI status in both patients with HNPCC and/or sporadic colorectal cancer.     

Performance of clinical guidelines compared with molecular tumour screening methods in identifying possible Lynch syndrome among colorectal cancer patients: a Norwegian population-based study

Background:

The aim of this study was to assess the performance of the Revised Bethesda Guidelines (RBG) and the accuracy of the Amsterdam II criteria (AM II) in identifying possible Lynch syndrome (LS) compared with the results of molecular tumour testing.

Methods:

Tumours from 336 unselected colorectal cancer patients were analysed by three molecular tests (namely microsatellite instability (MSI), BRAF mutation and methylation of mismatch-repair genes), and patients were classified according to the RBG and AM II criteria.

Results:

A total of 87 (25.9%) patients fulfilled the RBG for molecular tumour analyses (MSI and/or immunohistochemistry), and the AM II identified 8 (2.4%) patients as having possible LS. Molecular tests identified 12 tumours (3.6%) as probable LS. The RBG identified 6 of the 12 patients (sensitivity 50%), whereas 5 of the 8 patients who fulfilled the AM II criteria were not likely to be LS, based on molecular tests (predictive value of positive test, 38%).

Interpretation:

Assuming a fairly high accuracy of molecular testing, the performance of the RBG in identifying patients with possible LS was poor, and the AM II criteria falsely identified a large proportion as having possible LS. This favours the use of molecular testing in the diagnosis of possible LS.     

The Norwegian <Emphasis Type="Italic">PMS2</Emphasis> founder mutation c.989-1G &gt; T shows high penetrance of microsatellite instable cancers with normal immunohistochemistry

Background

Using immunohistochemistry (IHC) to select cases for mismatch repair (MMR) genetic testing, we failed to identify a large kindred with the deleterious PMS2 mutation c.989-1G > T. The purpose of the study was to examine the sensitivity of IHC and microsatellite instability-analysis (MSI) to identify carriers of the mutation, and to estimate its penetrance and expressions.

Methods

All carriers and obligate carriers of the mutation were identified. All cancer diagnoses were confirmed. IHC and MSI-analysis were performed on available tumours. Penetrances of cancers included in the Amsterdam and the Bethesda Criteria, for MSI-high tumours and MSI-high and low tumours were calculated by the Kaplan-Meier algorithm.

Results

Probability for co-segregation of the mutation and cancers by chance was 0.000004. Fifty-six carriers or obligate carriers were identified. There was normal staining for PMS2 in 15/18 (83.3%) of tumours included in the AMS1/AMS2/Bethesda criteria. MSI-analysis showed that 15/21 (71.4%) of tumours were MSI-high and 4/21 (19.0%) were MSI-low. Penetrance at 70 years was 30.6% for AMS1 cancers (colorectal cancers), 42.8% for AMS2 cancers, 47.2% for Bethesda cancers, 55.6% for MSI-high and MSI-low cancers and 52.2% for MSI-high cancers.

Conclusions

The mutation met class 5 criteria for pathogenicity. IHC was insensitive in detecting tumours caused by the mutation. Penetrance of cancers that displayed MSI was 56% at 70 years. Besides colorectal cancers, the most frequent expressions were carcinoma of the endometrium and breast in females and stomach and prostate in males.     

Screening for Lynch Syndrome in Young Colorectal Cancer Patients from Saudi Arabia Using Microsatellite Instability as the Initial Test

Background: Lynch Syndrome (LS) is a familial cancer condition caused by germline mutations in DNA mismatch repair genes. Individuals with LS have a greatly increased risk of developing colorectal cancer (CRC) and it is therefore important to identify mutation carriers so they can undergo regular surveillance. Tumor DNA from LS patients characteristically shows microsatellite instability (MSI). Our aim here was to screen young CRC patients for MSI as a first step in the identification of unrecognized cases of LS in the Saudi population. Materials and Methods: Archival tumor tissue was obtained from 284 CRC patients treated at 4 institutes in Dammam and Riyadh between 2006 and 2015 and aged less than 60 years at diagnosis. MSI screening was performed using the BAT-26 microsatellite marker and positive cases confirmed using the pentaplex MSI analysis system. Positive cases were screened for BRAF mutations to exclude sporadic CRC and were evaluated for loss of expression of 4 DNA mismatch repair proteins using immunohistochemistry. Results: MSI was found in 33/284 (11.6%) cases, of which only one showed a BRAF mutation. Saudi MSI cases showed similar instability in the BAT-26 and BAT-25 markers to Australian MSI cases, but significantly lower frequencies of instability in 3 other microsatellite markers. Conclusions: MSI screening of young Saudi CRC patients reveals that approximately 1 in 9 are candidates for LS. Patients with MSI are strongly recommended to undergo genetic counselling and germline mutation testing for LS. Other affected family members can then be identified and offered regular surveillance for early detection of LS-associated cancers.     

Early-onset colorectal cancer patients without family history are “at very low risk” for lynch syndrome

Introduction

Several studies evaluated the prevalence of Lynch Syndrome (LS) in young onset colorectal cancer (CRC) patients and the results were extremely variable (5%-20%). Immunohistochemistry (IHC) for MMR proteins and/or MSI analysis are screening tests that are done, either by themselves or in conjunction, on colon cancer tissue to identify individuals at risk for LS. The primary aim of our study was to evaluate the prevalence of LS in a large series of early-onset CRC without family history compared with those with family history. The secondary aim was to assess the diagnostic accuracy of IHC and MSI analysis as pre-screening tools for LS.

Methods

Early-onset CRC patients (≤ 50 years) were prospectively recruited in the study. IHC and MSI analysis were performed in all the patients. Germ-line mutation analysis (GMA) was carried out in all MMR deficient tumors. A logistic regression model was performed to identify clinical features predictive of MSI-H.

Results

117 early onset CRC cases were categorized in three groups (A, B, C) according with family history of CRC. IHC and MSI analysis showed MMR deficiency in 6/70 patients (8.6%) of group A, 24/40 patients (60%) of group B and none of group C. GMA showed a deleterious mutation in 19 (47.5%) patients of group B. MSI analysis had a diagnostic accuracy of 95.7% (CI 92.1-99.4) and IHC of 83.8% (CI 77.1-90.4). The logistic regression model revealed that by using a combination of the two features “No Amsterdam Criteria” and ”left sided CRC” to exclude MSI-H, accuracy was 89.7% (84.2-95.2).

Conclusions

Early-onset CRC patients, with left sided CRC and without family history are “at very low risk” for Lynch syndrome. The two simple criteria of family history and CRC site could be used as a pre-screening tool to evaluate whether or not patients should undergo tissue molecular screening. In the few cases of suspected LS (right sided CRC and/or Amsterdam Criteria), a reasonable approach could be to perform MSI analysis first and IHC afterwards only in MSI-H patients.     

Van-Gogh-like 2 antagonises the canonical WNT pathway and is methylated in colorectal cancers

Background:

Aberrant activation of the canonical WNT signaling is a feature of colorectal cancer (CRC). Van-Gogh-like 2 (VANGL2) belongs to the non-canonical WNT pathway whose activation inhibits canonical WNT signaling. In this study, we investigated the role of VANGL2 and its epigenetic regulation in CRC.

Methods:

Van-Gogh-like 2 expression and promoter methylation after 5-aza-2′-deoxycytidine (5-aza) treatment were evaluated in CRC cells. DNA samples from 418 sporadic CRCs were tested for VANGL2 promoter methylation and microsatellite instability (MSI). Proliferation, colony formation and activation of the WNT pathway were tested in cells after VANGL2 overexpression.

Results:

Van-Gogh-like 2 mRNA was significantly higher in 5-aza-treated RKO, LOVO and SW48, whereas no differences were found in SW480. Van-Gogh-like 2 was fully methylated in RKO, SW48, HCT116, DLD1 and Caco2; partially methylated in LOVO, LS174T and SW837; and unmethylated in SW480, SW620 and HT29. Higher expression of VANGL2 mRNA was found in the unmethylated cell lines. In CRC specimens (8.93% MSI), methylated VANGL2 was associated with MSI, higher grade, proximal colon location and BRAF mutation. Van-Gogh-like 2 overexpression in SW480 significantly decreased proliferation, colony formation and β-catenin levels.

Conclusion:

Van-Gogh-like 2 is frequently methylated in MSI-CRCs with BRAF mutation and may act as a tumour suppressor gene, counteracting WNT/β-catenin signaling.     

Clinical and molecular detection of inherited colorectal cancers in northeast Italy: a first prospective study of incidence of Lynch syndrome and MUTYH-related colorectal cancer in Italy

The reported incidence of hereditary colorectal cancers (CRCs) is widely variable. The principal aim of the study was to prospectively evaluate the incidence of familial CRCs in a region of northern Italy using a standardized method. Consecutive CRC patients were prospectively enrolled from October 2002 to December 2003. Patients underwent a structured family history, the microsatellite instability (MSI) test and a screen for MUTYH mutations. Following family history patients were classified as belonging to high, moderate and mild risk families. Immunohistochemistry for MLH1, MSH2, MSH6 and PMS2 proteins and investigation for MLH1/MSH2 mutations, for MLH1 promoter methylation and for the V600E hotspot BRAF mutation were performed in high MSI (MSI-H) cases. Of the 430 patients enrolled, 17 (4%) were high risk [4 hereditary non-polyposis colorectal cancer (HNPCC), 12 suspected HNPCC and 1 MUTYH-associated adenomatous polyposis coli (MAP)], 53 moderate risk and 360 mild risk cases. The MSI test was performed on 393 tumours, and 46 (12%) of them showed MSI-H. In these patients, one MLH1 pathogenetic mutations and two MSH2 pathogenetic mutations were found. Thirty-two (70%) MSI-H cases demonstrated MLH1 methylation and/or BRAF mutation: None of them showed MLH1/MSH2 mutation. Two biallelic germline MUTYH mutations were found, one with clinical features of MAP. A strong family history of CRC was present in 4% of the enrolled cases; incidence of MLH1/MSH2 or MUTHY mutations was 1.3% and of MSI-H phenotype was 12%. MLH1 methylation and BRAF mutation can exclude 70% of MSI-H cases from gene sequencing.     

Synchronous gynecologic malignancy and preliminary results of Lynch syndrome

Objective

Lynch syndrome is a hereditary cancer syndrome that increases the risks of colorectal and gynecologic malignancies such as endometrial and ovarian cancer. Studies have shown that mutations in mismatch repair genes (MSH2, MSH6, and MLH1) are associated with Lynch syndrome. The aim of our study was to estimate the value of MSH2, MSH6, and MLH1 immunohistochemistry based on family history in a Korean sample.

Methods

Thirty six women with synchronous gynecologic tumors of endometrial and ovarian cancer were identified among patients being treated at our institution. Among them, 32 patients had tumor blocks (total 62 slides) available for analysis. According to a diagnostic algorithm, we performed immunohistochemistry analyses. Staining was scored based on intensity and proportion (negative or 0: intensity undetectable or minimal, proportion <5%; weak or 1+: intensity mild, proportion 5-30%; strong or 2+: intensity moderate to marked, proportion 30-99%).

Results

Among 32 eligible patients, 9 (28%) had a family history of cancer. Six patients (19%) were negative for MLH1; among them, four (4/6) were negative at both sites. Nine patients (28%) were negative for MSH2 or MSH6 at both sites or negative for both MSH2 and MSH6. Among these three patients showed negative staining for both sites. The three patients showing negative staining for MLH1, MSH2, and MSH6 at both sites with family history were considered to be the screening positive groups of Lynch syndrome.

Conclusion

In this study, the frequency of Lynch syndrome associated immunohistochemical staining (MLH1, MSH2, and MSH6) group was estimated as 9% (3/32) among Korean women with synchronous gynecologic tumors.     

Hereditary nonpolyposis colorectal cancer in endometrial cancer patients

Endometrial cancer is the second most common cancer in hereditary nonpolyposis colorectal cancer (HNPCC). It has often been overlooked to explore the possibility of HNPCC in endometrial cancer patients. Our study was to investigate how many HNPCC patients existed among endometrial cancer patients. Among patients who underwent hysterectomy for endometrial cancer at Seoul National University Hospital from 1996 to 2004, 113 patients were included, whose family history and clinical data could be obtained and tumor specimens were available for microsatellite instability (MSI) testing and immunohistochemical (IHC) staining of MLH1, MSH2 and MSH6 proteins. There were 4 (3.5%) clinical HNPCC patients fulfilling the Amsterdam criteria II, and 2 (2/4, 50%) of them carried MSH2 germline mutations. There were also 8 (7.1%) suspected HNPCC (s-HNPCC) patients fulfilling the revised criteria for s-HNPCC, and one (1/8, 12.5%) of them revealed MLH1 germline mutation. In 101 patients, who were not clinical HNPCC or s-HNPCC, 11 patients showed both MSI-high and loss of expression of MLH1, MSH2 or MSH6 proteins, and 2 (2/11, 18.2%) of them showed MSH6 germline mutations. In 113 patients with endometrial cancer, we could find 5 (4.4%) HNPCC patients with MMR germline mutation and 2 (1.8%) clinical HNPCC patients without identified MMR gene mutation. Family history was critical in detecting 3 HNPCC patients with MMR germline mutation, and MSI testing with IHC staining for MLH1, MSH2 and MSH6 proteins was needed in the diagnosis of 2 HNPCC patients who were not clinical HNPCC or s-HNPCC, especially for MSH6 germline mutation.     

Mismatch repair gene defects in sporadic colorectal cancer enhance immune surveillance

Background

There is evidence that colorectal cancers (CRC) with DNA mismatch repair deficiency (MMR-D) are associated with a better prognosis than the generality of large bowel malignancies. Since an active immune surveillance process has been demonstrated to influence CRC outcome, we investigated whether MMR-D can enhance the immune response in CRC.

Patients and Methods

A group of 113 consecutive patients operated for CRC (42 stage I or II and 71 with stage III or IV) was retrospectively analyzed. The expression of MMR genes (MSH2, MLH1, MSH6 and PSM2) and co-stimulatory molecule CD80 was assessed by tissue microarray immunohistochemistry. In addition, tumor infiltrating mononuclear cells (TIMC) and T cell subpopulations (CD4, CD8, T-bet and FoxP-3) were quantified. The effect of specific siRNA (siMSH2, siMLH1, siMSH6 and siPSM2) transfection in HT29 on CD80 expression was quantified by flow cytometry. Non parametric statistics and survival analysis were used.

Results

Patients with MMR-D showed a higher T-bet/CD4 ratio (p = 0.02), a higher rate of CD80 expression and CD8 lymphocyte infiltration compared to those with no MMR-D. Moreover, in the MMR-D group, the Treg marker FoxP-3 was not expressed (p = 0.05). MMR-D patients with stage I or II and T-bet expression had a significant better survival (p = 0.009). Silencing of MSH2, MLH1 and MSH6, but not PSM2, significantly increased the rate of CD80+ HT29 cells (p = 0.007, p = 0.023 and p = 0.015, respectively).

Conclusions

CRC with MMR-D showed a higher CD80 expression, and CD8+ and Th1 T-cell infiltration. In vitro silencing of MSH2, MLH1 and MSH6 significantly increased CD80+ cell rate. These results suggest an enhanced immune surveillance mechanism in presence of MMR-D.     

A state-wide population-based program for detection of lynch syndrome based upon immunohistochemical and molecular testing of colorectal tumours

We have previously established in a large retrospective study that testing for microsatellite instability (MSI) in colorectal cancer (CRC) from patients aged <60 years was an effective first screen to identify individuals with Lynch syndrome (LS). From these findings, MSI and/or immunohistochemical (IHC) screening was recommended for all newly diagnosed CRC patients aged <60 years in Western Australia, regardless of family history of cancer. In the current study we evaluated the utility of routine MSI/IHC screening by diagnostic pathology laboratories for the detection of previously undiagnosed individuals and families with LS. From January 2009 to December 2010, 270 tumours were tested for MSI and for expression of MLH1, PMS2, MSH2 and MSH6 using IHC. Cases showing MSI and/or loss of expression were also tested for the BRAF V600E hotspot mutation. Seventy cases were found to have MSI, of which 25 were excluded from further investigation as possible LS cases due to presence of the BRAF V600E mutation. The remaining 45 “red flag” cases were eligible for germline testing based on their MSI, IHC and BRAF status. From 31 cases tested to date, 15 germline mutations have been found. Thirteen were from individuals not previously recognized as LS and two were untested members from known LS families. Extrapolation of the mutation incidence (15/31, 48%) to all red flag cases (n = 45) suggests that approximately 22 mutation carriers exist in this cohort. This value approximates the number of CRC cases due to LS that could be expected to arise in the Western Australian population over a two-year period (n = 24), assuming that 1% of all CRCs are due to LS. Although further improvements in workflow can be made, our preliminary findings following the implementation of state-wide routine MSI and IHC testing in Western Australia indicate that the majority of LS cases are being identified.     

Microsatellite instability and mutation analysis among southern Italian patients with colorectal carcinoma: detection of different alterations accounting for MLH1 and MSH2 inactivation in familial cases.

BACKGROUND: Microsatellite instability (MSI) is due to defective DNA mismatch repair (MMR) and has been detected at various rates in colorectal carcinoma (CRC). The role of MSI in colorectal tumorigenesis was assessed further in this study by both microsatellite analysis of two CRC subsets [unselected patients (n = 215) and patients <50 years of age (n = 95)], and mutation screening of the two major MMR genes MLH1 and MSH2 among familial CRC cases. PATIENTS AND METHODS: PCR-based microsatellite analysis was performed on paraffin-embedded tissues. In CRC families, MLH1/MSH2 mutation analysis and MLH1/MSH2 immunostaining were performed on germline DNA and MSI+ tumour tissues, respectively. RESULTS: The MSI+ phenotype was detected in 75 (24%) patients, with higher incidence in early-onset or proximally located tumours. Among 220 patients investigated for family cancer history, MSI frequency was markedly higher in familial [18/27 (67%)] than in sporadic [32/193 (17%)] cases. Three MLH1 and six MSH2 germline mutations were identified in 14 out of 36 (39%) CRC families. Prevalence of MLH1/MSH2 mutations in CRC families was significantly increased by the presence of: (i) fulfilled Amsterdam criteria; (ii) four or more CRCs; or (iii) one or more endometrial cancer. While MSH2 was found mostly mutated, almost all [8/9 (89%)] familial MSI+ cases with loss of the MLH1 protein were negative for MLH1 germline mutations. CONCLUSIONS: Both genetic (for MSH2) and gene-silencing (for MLH1) alterations seem to be involved in CRC pathogenesis.     

Constitutional mismatch repair deficiency and Lynch syndrome among consecutive Arab Bedouins with colorectal cancer in Israel

We assessed the molecular characteristics and the frequency of mutations in mismatch-repair genes among Bedouin patients with colorectal cancer (CRC) in Israel. Bedouin patients with a diagnosis of CRC at a major hospital in the southern part of Israel were deemed eligible for this study. The primary screening method was immunohistochemical staining for mismatch-repair proteins (MLH1, MSH2, MSH6, and PMS2). For subjects with abnormal immunohistochemical staining, we performed microsatellite instability (MSI) analyses, and for tumors with a loss of MLH1 expression we also performed BRAF testing. In MSI high cases we searched further for germline mutations. Of the 24 patients enrolled, four subjects (16.7%) had MSI high tumors: one subject was found to harbor a biallelic PMS2 mutation, one subject had Lynch syndrome (LS) with MSH6 mutation and two subjects had a loss of MLH1/PMS2 proteins/BRAF ^{wild type}/normal MLH1 sequence. Ten patients (41.7%) were younger than 50 at the time of diagnosis and none had first degree relatives with CRC. In conclusion, in this cohort of 24 consecutive Arab Bedouins with CRC, one patient was found to harbor a constitutional mismatch repair deficiency, one patient had LS with MSH6 mutation, and two patients had unresolved loss of MLH1/PMS2 proteins/BRAF ^{wild type} phenotype.