Methylation‐induced loss of miR‐484 in microsatellite‐unstable colorectal cancer promotes both viability and IL‐8 production via CD137L

Colorectal cancer (CRC) exhibiting MSI (microsatellite instability) represents a well‐defined subtype characterized by a deficient mismatch repair pathway and typical clinico‐pathological features. Our objective was to identify the entire miRNome and its molecular pathological roles in MSI CRCs. We profiled miRNA expression in MSI CRCs and compared it with MSS counterparts. Microarray and qRT‐PCR analysis identified eight miRNAs that could distinguish the MSI status of CRCs. MiR‐484 was the most significantly decreased miRNA in MSI CRCs, primarily mediated by the CpG island methylator phenotype. MiR‐484 functions as a tumour suppressor to inhibit MSI CRC cell viability in vitro and in vivo. Moreover, miR‐484 repressed CD137L expression and thereby attenuated IL‐8 production by MSI CRC cells. Our results contribute to a better understanding of the roles of dysregulated miRNAs in the distinct phenotypic features of MSI CRCs and indicate an option for early diagnosis and gene therapy for these patients. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Single‐molecule detection of cancer mutations using a novel PCR‐LDR‐qPCR assay

Detection of low‐abundance mutations in cell‐free DNA is being used to identify early cancer and early cancer recurrence. Here, we report a new PCR‐LDR‐qPCR assay capable of detecting point mutations at a single‐molecule resolution in the presence of an excess of wild‐type DNA. Major features of the assay include selective amplification and detection of mutant DNA employing multiple nested primer‐binding regions as well as wild‐type sequence blocking oligonucleotides, prevention of carryover contamination, spatial sample dilution, and detection of multiple mutations in the same position. Our method was tested to interrogate the following common cancer somatic mutations: BRAF:c.1799T>A (p.Val600Glu), TP53:c.743G>A (p.Arg248Gln), KRAS:c.35G>C (p.Gly12Ala), KRAS:c.35G>T (p.Gly12Val), KRAS:c.35G>A (p.Gly12Asp), KRAS:c.34G>T (p.Gly12Cys), and KRAS:c.34G>A (p.Gly12Ser). The single‐well version of the assay detected 2–5 copies of these mutations, when diluted with 10,000 genome equivalents (GE) of wild‐type human genomic DNA (hgDNA) from buffy coat. A 12‐well (pixel) version of the assay was capable of single‐molecule detection of the aforementioned mutations at TP53, BRAF, and KRAS (specifically p.Gly12Val and p.Gly12Cys), mixed with 1,000–2,250 GE of wild‐type hgDNA from plasma or buffy coat. The assay described herein is highly sensitive, specific, and robust, and potentially useful in liquid biopsies.     

Major improvement in the detection of microsatellite instability in colorectal cancer using HSP110 T17 E‐ice‐COLD‐PCR

Every colorectal cancer (CRC) patient should be tested for microsatellite instability (MSI) to screen for Lynch syndrome. Evaluation of MSI status involves screening tumor DNA for the presence of somatic deletions in DNA repeats using PCR followed by fragment analysis. While this method may lack sensitivity due to the presence of a high level of germline DNA, which frequently contaminates the core of primary colon tumors, no other method developed to date is capable of modifying the standard PCR protocol to achieve improvement of MSI detection. Here, we describe a new approach developed for the ultra‐sensitive detection of MSI in CRC based on E‐ice‐COLD‐PCR, using HSP110 T17, a mononucleotide DNA repeat previously proposed as an optimal marker to detect MSI in tumor DNA, and an oligo(dT)₁₆ LNA blocker probe complementary to wild‐type genotypes. The HT17 E‐ice‐COLD‐PCR assay improved MSI detection by 20–200‐fold compared with standard PCR using HT17 alone. It presents an analytical sensitivity of 0.1%–0.05% of mutant alleles in wild‐type background, thus greatly improving MSI detection in CRC samples highly contaminated with normal DNA. HT17 E‐ice‐COLD‐PCR is a rapid, cost‐effective, easy‐to‐implement, and highly sensitive method, which could significantly improve the detection of MSI in routine clinical testing.     

Somatic mutations and losses of expression of microRNA regulation‐related genes AGO2 and TNRC6A in gastric and colorectal cancers

Mounting evidence indicates that deregulation of microRNAs (miRNAs) are involved in development of many human diseases, including cancers. Regulation of miRNA is a complicated process and some components in the regulation are known to be altered in human cancers. Among the miRNA regulation‐related genes, we found that AGO1, AGO2, TNRC6A, TNRC6C, TARBP2 and EXPORTIN5 genes have mononucleotide repeats in their coding sequences. To see whether these genes are mutated in cancers with microsatellite instability (MSI), we analysed the mononucleotide repeats in 27 gastric cancers (GCs) with high MSI (MSI‐H), 18 GC with low MSI (MSI‐L), 45 GC with stable MSI (MSS), 41 colorectal cancers (CRCs) with MSI‐H, 14 CRCs with MSI‐L and 45 CRCs with stable MSI (MSS) by single‐strand conformation polymorphism (SSCP) analysis and DNA sequencing. We found AGO2, TNRC6A, TARBP2, TNRC6C and EXPORTIN5 mutations in 10, six, one, one and one cancer(s), respectively. They were detected in MSI‐H but not in MSI‐L or MSS cancers. The GCs and CRCs with MSI‐H harboured one or more mutations of the genes in 22% and 27%, respectively. We also analysed Ago2 and TNRC6A protein expressions in GCs and CRCs with MSI‐H. In cancers with MSI‐H, loss of Ago2 expression was observed in 40% of GCs and 35% of CRCs, while loss of TNRC6A was observed in 52% of the GCs and 54% of the CRCs. Our data indicate that frameshift mutations in AGO2 and TNRC6A and their losses of expression are common in GCs and CRCs with MSI‐H, and suggest that these alterations may contribute to the cancer development by deregulating miRNA regulation. Copyright © 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Dominant high expression of wild‐type HSP110 defines a poor prognostic subgroup of colorectal carcinomas with microsatellite instability: a whole‐section immunohistochemical analysis

The aim of this study is to establish heat shock protein 110 (HSP110) as a prognostic biomarker of colorectal carcinomas (CRCs) with microsatellite instability‐high (MSI‐H) by considering the intratumoral heterogeneity of HSP110 expression. We performed whole‐section immunohistochemistry (IHC) for wild‐type HSP110 (HSP110wt) in 164 MSI‐H CRCs. The intensity of the HSP110wt expression in tumor cells was semiquantitatively scored (0/1/2/3), and the HSP110wt expression status of each tumor was classified as low or high using the following four scoring criteria: H‐score, dominant intensity score, lowest intensity score, and highest intensity score. Among the four criteria, only the dominant intensity score‐based dichotomous classification of HSP110wt expression was significantly associated with a difference in disease‐free survival (log‐rank p = 0.035) in 164 MSI‐H CRCs. The HSP110wt‐low MSI‐H CRCs were significantly correlated with larger deletions in the HSP110 T₁₇ mononucleotide repeat (≥4 bp; p < 0.001). In conclusion, the dominant intensity score‐based assessment of HSP110wt IHC can be a simple and useful method for the prognostic stratification of MSI‐H CRCs. It is expected that HSP110wt IHC may be used to identify a subgroup of MSI‐H CRCs with poor prognosis and/or candidates for further treatment, such as immunotherapy using immune checkpoint inhibitors in MSI‐H CRCs.     

A population‐based study of hereditary non‐polyposis colorectal cancer: evidence of pathologic and genetic heterogeneity

Hereditary non‐polyposis colorectal cancer (HNPCC) may be the result of Lynch syndrome (LS) caused by mutations in mismatch repair (MMR) genes, a syndrome of unknown etiology called familial colorectal cancer type‐X (FCCTX), or familial serrated neoplasia associated with the colorectal cancer (CRC) somatic BRAF mutation. To determine the cause of HNPCC in the founder population of the island of Newfoundland, we studied 37 families with LS and 29 families without LS who fulfilled the Amsterdam I criteria. In non‐LS, four index CRCs were BRAF mutation positive, one of which was microsatellite instable. Geographic clustering of LS families caused by three different founder mutations in MSH2 was observed. Nine unique MMR mutations in four MMR genes were identified in single families distributed in different geographic isolates. The geographic distribution of non‐LS was similar to LS. The coefficient of relatedness using genotype data was significantly higher for non‐LS than for all CRC. Extensive genealogic investigation failed to connect non‐LS families and in some clusters pathologic CRC heterogeneity was observed. We conclude that non‐LS HNPCC may be a heterogeneous disorder with different pathogenic pathways, and that the geographic distribution is consistent with multiple different mutations in unknown CRC susceptibility gene(s).     

Prognostic implications of CpG island hypermethylator phenotype in colorectal cancers

CpG island methylator phenotype (CIMP) refers to a subset of colorectal cancers (CRCs) that are characterized by concordant hypermethylation of multiple CpG island loci. CIMP+ CRCs have peculiar clinicopathological features. However, controversy exists over prognostic implications of CIMP in CRCs. We analyzed 320 cases of CRCs for their CIMP status using the MethyLight assay and determined clinicopathological features and prognostic implications of CIMP alone or in combination with microsatellite instability (MSI). With methylation of five or more markers among eight markers examined, CIMP+ tumors were significantly associated with female gender, proximal tumor location, poor differentiation, nodal metastasis, more advanced cancer, BRAF mutations, MSI, and poor prognosis (all P values <0.05). Ogino’s combined eight-marker panel outperformed the Ogino and the Laird five-marker panels in detecting these features. Of the four molecular subtypes generated by the combination of CIMP and MSI status, the CIMP+/MSI? subtype showed the worst clinical outcome (P?=?0.0003). However, poor prognosis of CIMP+/MSI? subtype was found to be attributed to BRAF mutation. In conclusion, the CIMP+/MSI? subtype tends to present with distinct clinicopathological and molecular features and shows the worst clinical outcome among the four molecular subtypes of CRCs.     

DNA mismatch repair deficiency in sporadic colorectal cancer and Lynch syndrome

Poulogiannis G, Frayling I M & Arends M J
(2010) Histopathology 56, 167–179 DNA mismatch repair deficiency in sporadic colorectal cancer and Lynch syndrome DNA mismatch repair (MMR) deficiency is one of the best understood forms of genetic instability in colorectal cancer (CRC), and is characterized by the loss of function of the MMR pathway. Failure to repair replication‐associated errors due to a defective MMR system allows persistence of mismatch mutations all over the genome, but especially in regions of repetitive DNA known as microsatellites, giving rise to the phenomenon of microsatellite instability (MSI). A high frequency of instability at microsatellites (MSI‐H) is the hallmark of the most common form of hereditary susceptibility to CRC, known as Lynch syndrome (LS) (previously known as hereditary non‐polyposis colorectal cancer syndrome), but is also observed in ～15–20% of sporadic colonic cancers (and rarely in rectal cancers). Tumour analysis by both MMR protein immunohistochemistry and DNA testing for MSI is necessary to provide a comprehensive picture of molecular abnormality, for use in conjunction with family history data and other clinicopathological features, in order to distinguish LS from sporadic MMR‐deficient CRC. Identification of the gene targets that become mutated in MMR‐deficient tumours may explain, at least in part, some of the clinical, pathological and biological features of MSI‐H CRCs and holds promise for developing novel therapeutics.     

Development of a fluorescent multiplex assay for detection of MSI-High tumors

Determining whether a tumor exhibits microsatellite instability (MSI) is useful in identifying patients with hereditary non-polyposis colorectal cancer and sporadic gastrointestinal cancers with defective DNA mismatch repair (MMR). The assessment of MSI status aids in establishing a clinical prognosis and may be predictive of tumor response to chemotherapy. A reference panel of five markers was suggested for MSI analysis by a National Cancer Institute (NCI) workshop in 1997 that has helped to standardize testing. But this panel of markers has limitations resulting from the inclusion of dinucleotide markers, which are less sensitive and specific for detection of tumors with MMR deficiencies compared to other types of markers that are currently available. This study demonstrates that mononucleotides are the most sensitive and specific markers for detection of tumors with defects in MMR and identifies an optimal panel of markers for detection of MSI-H tumors. A set of 266 mono-, di-, tetra- and penta-nucleotide repeat microsatellite markers were used to screen for MSI in colorectal tumors. The best markers for detection of MSI-H tumors were selected for a MSI Multiplex System, which included five mononucleotide markers: BAT-25, BAT-26, NR-21, NR-24 and MONO-27. In addition, two pentanucleotide markers were added to identify sample mix-ups and/or contamination. We classified 153 colorectal tumors using the new MSI Multiplex System and compared the results to those obtained with a panel of 10 microsatellite markers combined with immunohistochemical (IHC) analysis. We observed 99% concordance between the two methods with nearly 100% accuracy in detection of MSI-H tumors. Approximately 5% of the MSI-H tumors had normal levels of four MMR proteins and as a result would have been misclassified based solely on IHC analysis, emphasizing the importance of performing MSI testing. The new MSI Multiplex System offers several distinct advantages over other methods of MSI testing in that it is both extremely sensitive and specific and amenable to high-throughput analysis. The MSI Multiplex System meets the new recommendations proposed at the recent 2002 NCI workshop on HNPCC and MSI testing and overcomes problems inherent to the original five-marker panel. The use of a single multiplex fluorescent MSI assay reduces the time and costs involved in MSI testing with increased reliability and accuracy and thus should facilitate widespread screening for microsatellite instability in tumors of patients with gastrointestinal cancers.     

Diagnostic efficacy of anti‐SARS‐CoV‐2 IgG/IgM test for COVID‐19: A meta‐analysis

The serological testing of anti‐SARS‐CoV‐2 immunoglobulin G (IgG) and/or IgM is widely used in the diagnosis of COVID‐19. However, its diagnostic efficacy remains unclear. In this study, we searched for diagnostic studies from the Web of Science, PubMed, Embase, CNKI, and Wanfang databases to calculate the pooled diagnostic accuracy measures using bivariate random‐effects model meta‐analysis. As a result, 22 from a total of 1613 articles, including 2282 patients with SARS‐CoV‐2 and 1485 healthy persons or patients without SARS‐CoV‐2, were selected for a meta‐analysis. Pooled sensitivity, specificity, and area under curve of the summary receiver operator curve (SROC) were: (a) 0.85 (95% confidence interval [CI]: 0.79‐0.90), 0.99 (95% CI: 0.98‐1.00), and 0.99 (95% CI: 0.97‐0.99) for anti‐SARS‐CoV‐2 IgG and (b) 0.74 (95% CI: 0.65‐0.81), 0.99 (95% CI: 0.97‐1.00), and 0.95 (95% CI: 0.93‐0.97) for IgM. A subgroup analysis among detection methods indicated the sensitivity of IgG and IgM using enzyme‐linked immunosorbent assay were slightly lower than those using gold immunochromatography assay (GICA) and chemiluminescence immunoassay (P > .05). These results showed that the detection of anti‐SARS‐CoV‐2 IgG and IgM had high diagnostic efficiency to assist the diagnosis of SARS‐CoV‐2 infection. And, GICA might be used as the preferred method for its accuracy and simplicity.     

Genetic and expressional alterations of CHD genes in gastric and colorectal cancers

Kim M S, Chung N G, Kang M R, Yoo N J & Lee S H
(2011) Histopathology 58 , 660–668
Genetic and expressional alterations of CHD genes in gastric and colorectal cancers Aims: Chromodomain helicase DNA‐binding protein (CHD) is a regulator of the chromatin remodelling process. The aim was to determine the CHD1, CHD2, CHD3, CHD4, CHD7, CHD8 and CHD9mutational status of mononucleotide repeats in gastric and colorectal cancers with microsatellite instability (MSI). Methods and Results: The repeats were determined in 28 gastric cancers (GCs) with high MSI (MSI‐H), 45 GCs with low MSI (MSI‐L)/stable MSI (MSS), 35 colorectal cancers (CRCs) with MSI‐H and 45 CRCs with MSI‐L/MSS by single‐strand conformation polymorphism analysis. CHD4 and CHD8 expressionwas also examined in GCs and CRCs by immunohistochemistry. CHD1, CHD2, CHD3, CHD4, CHD7, CHD8 and CHD9 mutations were found in five, 19, three, five, seven, 10 and seven cancers, respectively. They were detected in MSI‐H cancers, but not in MSI‐L/MSS cancers. Loss of CHD4 expression was observed in 56.4% of the GCs and 55.7% of the CRCs, and loss of CHD8 was observed in 35.7% of the GCs and 28.6% of the CRCs. The cancers with CHD4 and CHD8 mutations showed loss of CHD4 and CHD8 expression, respectively. Conclusions: Frameshift mutation and loss of expression of CHD genes are common in GCs and CRCs with MSI‐H.These alterations might contribute to cancer pathogenesis by deregulating CHD‐mediated chromatin remodelling.     

The spectrum of Lynch syndrome-associated germ-line mutations in Russia

Hereditary non-polyposis colorectal cancer (HNPCC), also known as Lynch syndrome (LS), is a common cancer-predisposing syndrome. This study aimed to investigate the spectrum of germ-line mutations in Russian LS patients. LS-related mismatch repair (MMR) genes were analyzed in 16 patients, who were forwarded to genetic testing due to strong clinical features of LS and had high-level microsatellite instability (MSI-H) in the tumor (n = 14) or unknown MSI status (n = 2). In addition, 672 consecutive colorectal cancer (CRC) cases were screened for family history; 15 patients were younger than 50 years and reported 2 or more instances of LS-related cancers in 1st- or 2nd-degree relatives. Seven of these cases demonstrated MSI-H and therefore were subjected to DNA germ-line testing. Overall, 17/23 (74%) subjects carried LS-associated gene variants (MLH1: 10; MSH2: 4; MSH6: 2; PMS2: 1), with 2 alleles (MLH1 c.677G > T and MSH2 с.1906G > C) detected twice. Testing for recurrent mutations of 30 consecutive MSI-H CRCs led to the identification of 2 additional subjects with LS. The analysis of all relevant publications identified 28 unrelated LS patients presented in Russian medical literature and 3 unrelated Russian LS subjects described in international journals. Overall, 15/49 (31%) genetic defects revealed in Russian LS patients were represented by six recurrent alleles (MLH1: c.350C > T, c.677G > T, c.1852_1854del; MSH2: c.942+3A > T, c.1861C > T, с.1906G > C). We conclude that the founder effect for LS in Russia is seemingly less pronounced than the one for hereditary breast-ovarian cancer syndrome, however testing for recurrent LS mutations may be considered feasible in some circumstances.     

Differential clinicopathological features in microsatellite instability-positive colorectal cancers depending on CIMP status

Microsatellite instability-positive (MSI+) colorectal cancers (CRCs) are divided into CpG island methylator phenotype-positive (CIMP+) and CpG island methylator phenotype-negative (CIMP−) tumors. The repertoire of inactivated genes in CIMP+/MSI+ CRCs overlaps with but is likely to differ from that of CIMP−/MSI+ CRCs. Because epigenotypic differences are likely to be manifested as phenotypic differences, CIMP+/MSI+ CRCs are expected to differ from CIMP−/MSI+ CRCs in some clinicopathological features. This study aimed to characterize both common and different features between the two subtypes. A total of 72 MSI+ CRCs were analyzed for their methylation status in eight CIMP panel markers using MethyLight assay. CIMP+/MSI+ and CIMP−/MSI+ CRCs were compared regarding clinicopathologic features and mutation in KRAS/BRAF. An independent set of MSI+ CRCs (n = 97) was analyzed for their relationship of CIMP+ status with clinical outcome. Eighteen cases (25%) were CIMP+, and this CIMP+ subtype was highly correlated with older age (P < 0.001). Polypoid gross appearance without ulceration was observed only in CIMP−/MSI+ CRCs (18.5%, P = 0.057). CIMP+/MSI+ CRCs were closely associated with poor differentiation, medullary appearance, signet ring cell appearance, and acinar-form appearance, whereas the CIMP−/MSI+ subtype was closely associated with intraglandular eosinophilic mucin and stratified nuclei (all P values <0.05). Patients with CIMP+/MSI+ CRCs showed worse overall survival than patients with CIMP−/MSI+ CRCs. Our results demonstrate heterogeneity in the clinicopathological features of MSI+ CRCs depending on CIMP status. The observation that CIMP+ and CIMP− subtypes showed different clinical behaviors may provide a clue for establishing subtype-specific therapeutic strategies for these two subtypes.     

Yield of routine molecular analyses in colorectal cancer patients ≤70 years to detect underlying Lynch syndrome

Although early detection of Lynch syndrome (LS) is important, a considerable proportion of patients with LS remains unrecognized. We aimed to study the yield of LS detection by routine molecular analyses in colorectal cancer (CRC) patients until 70 years of age. We prospectively included consecutive CRC patients ≤70 years. Tumour specimens were analysed for microsatellite instability (MSI), immunohistochemical mismatch-repair protein expression and MLH1-promoter methylation. Tumours were classified as either: (a) likely caused by LS; (b) sporadic microsatellite-unstable (MSI-H); or (c) microsatellite-stable (MSS). Predictors of LS were determined by multivariable logistic regression. A total of 1117 CRC patients (57% males, median age 61 years) were included. Fifty patients (4.5%, 95% CI 3.4-5.9) were likely to have LS, and 71 had a sporadic MSI-H tumour (6.4%, 95% CI 5.1-8.0). Thirty-five patients likely to have LS (70%) were aged > 50 years. A molecular profile compatible with LS was detected in 10% (15/144) of patients aged ≤50, in 4% (15/377) of those aged 51-60 and in 3% (20/596) of patients > 61 years. Compared to MSS cases, patients likely to have LS were significantly younger (OR 3.9, 95% CI 1.7-8.7) and more often had right-sided CRCs (OR 14, 95% CI 6.0-34). In conclusion, molecular screening for LS in CRC patients ≤70 years leads to identification of a molecular profile compatible with LS in 4.5% of patients, with most of them not fulfilling the age criterion (≤50 years) routinely used for LS assessment. Routine use of MSI testing may be considered in CRC patients up to the age of 70 years, with a central role for the pathologist in the selection of patients.     

Functional interrogation of Lynch syndrome‐associated MSH2 missense variants via CRISPR‐Cas9 gene editing in human embryonic stem cells

Lynch syndrome (LS) predisposes patients to cancer and is caused by germline mutations in the DNA mismatch repair (MMR) genes. Identifying the deleterious mutation, such as a frameshift or nonsense mutation, is important for confirming an LS diagnosis. However, discovery of a missense variant is often inconclusive. The effects of these variants of uncertain significance (VUS) on disease pathogenesis are unclear, though understanding their impact on protein function can help determine their significance. Laboratory functional studies performed to date have been limited by their artificial nature. We report here an in‐cellulo functional assay in which we engineered site‐specific MSH2 VUS using clustered regularly interspaced short palindromic repeats‐Cas9 gene editing in human embryonic stem cells. This approach introduces the variant into the endogenous MSH2 loci, while simultaneously eliminating the wild‐type gene. We characterized the impact of the variants on cellular MMR functions including DNA damage response signaling and the repair of DNA microsatellites. We classified the MMR functional capability of eight of 10 VUS providing valuable information for determining their likelihood of being bona fide pathogenic LS variants. This human cell‐based assay system for functional testing of MMR gene VUS will facilitate the identification of high‐risk LS patients.     

BAT-26 identifies sporadic colorectal cancers with mutator phenotype: a correlative study with clinico-pathological features and mutations in mismatch repair genes

Microsatellite instability (MSI) is present in most colorectal cancers (CRC) associated with hereditary nonpolyposis colorectal cancer (HNPCC). MSI testing in so-called sporadic forms of CRC may become a useful tool in identifying new HNPCC kindred. The aim of this study was to analyse the utility of BAT-26 as a marker to identify CRCs with MSI and to investigate whether sporadic CRCs with MSI have a phenotypic expression similar to HNPCC cases. MSI was detected using two methods, an association of 7 poly(CA) repeats and a poly(A) repeat alone, BAT-26, in a series of 62 patients with apparently sporadic forms of CRC. Germ-line and somatic mutations in the hMSH2, hMLH1, and hMSH6 genes were analysed in patients with MSI+ tumours. Patients with MSI+ at poly(CA) loci and at BAT-26 were younger (p = 0·024 and p = 0·002), had tumours more frequently right sided (p = 0·017 and p = 0·0001) and more often mucinous (p = 0·037 and p = 0·005, respectively) than patients with MSI negative tumours. Mutation analysis allowed the identification of two patients carrying germ-line mutations in the hMLH1 gene (both were BAT-26+) and two other patients who had somatic mutation in the hMSH2 and in hMLH1 genes. In conclusion, the detection of MSI using poly(CA) repeats or BAT-26 alone allowed the identification of a subset of patients with clinico-pathological characteristics similar to those associated to HNPCC. BAT-26 has the advantage of being a simple and less expensive method that might be used as a screening procedure before mutation analysis. Copyright © 1999 John Wiley & Sons, Ltd.     

Annexin A10 expression correlates with serrated pathway features in colorectal carcinoma with microsatellite instability

Annexin A10 (ANXA10) has recently been identified as a marker of sessile serrated adenomas/polyps of the colorectum. Although the serrated neoplasia pathway is thought to be involved in the majority of microsatellite instability‐high (MSI‐H) sporadic colorectal carcinomas (CRCs), the clinicopathological implications of ANXA10 expression in CRC are unknown. Here, we evaluated ANXA10 expression status in 168 MSI‐H CRCs by immunohistochemistry. Among 168 MSI‐H CRCs, nuclear staining for ANXA10 in tumor cells revealed 28 cases (17%) with ANXA10‐positive (ANXA10+) tumors. Most of the ANXA10+ tumors were located in the proximal colon (96%, p < 0.001). The ANXA10+ phenotype in MSI‐H CRC was significantly associated with female gender (68%, p = 0.016), CpG island methylator phenotype‐high (CIMP‐H) (68%, p < 0.001), MLH1 promoter hypermethylation (61%, p < 0.001), loss of MLH1 expression (82%, p = 0.019), and wild‐type KRAS status (96%, p = 0.023). Survival analysis revealed no prognostic significance of ANXA10 expression in MSI‐H CRC. In conclusion, ANXA10+ MSI‐H colon carcinomas are characterized by serrated pathway features, including proximal location, female predominance, and high frequencies of CIMP‐H status and MLH1 methylation.     

L'instabilité des microsatellites dans les cancers du côlon

Characteristics of microsatellites instability (MSI) is abnormal variation of the number of repeated sequences in DNA from the tumor compared to DNA of healthy tissue from the same individual. MSI has been first described in a rare hereditary colon cancer Lynch syndrome or HNPCC syndrome (hereditary nonpolyposis colon cancer) caused by MMR (mismatch repair) genes defects. Later, MSI was described in 15% of sporadic colon cancer. To confirm the diagnosis of MSI, a panel of five markers are used, amplified by multiplex PCR. MSI associated with clinical criteria (Amsterdam or Bethesda criteria) are recommended for MMR genes molecular testing to confirm HNPCC. Genetic counselling, familial investigation and possibly prophylactic measures are then taken. In sporadic cancers, MSI is the consequence of MLH1 silencing by epimutation in the promotor and is correlated with a better prognosis and maybe a resistance to fluorouracile, an adjuvant chemotherapy of colon cancer.     

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.