Microsatellite mutator phenotype (MMP) tumors were reported in a subset of gastrointestinal carcinomas. The molecular pathogenesis of MMP tumors shows defects in the DNA mismatch repair genes, and also many germline and somatic mutations were reported in the MMP tumors. However, the detection of genetic defects in the MMP tumors is very difficult, mainly because many genes are included in the DNA mismatch repair genes. This study was undertaken to determine the best strategy for detecting defects in the DNA mismatch repair genes in gastrointestinal carcinomas. One of the effective ways for detecting defects in DNA mismatch repair genes is to screen the MMP tumors and evaluate the products of DNA mismatch repair genes by performing the multiplex RT-PCR method. We have screened the MMP tumors by using 5 microsatellite markers in the 12 cancer cell lines, 120 colon carcinomas and 99 gastric carcinomas and found 6 MMP cell lines, 10 MMP colon cancers, and 9 MMP gastric carcinomas. In addition, we evaluated 6 DNA mismatch repair gene products (hMSH2, hMSH3, hMSH6, hMLH1, hPMS1 and hPMS2) by multiplex RT-PCR analysis and found decreased expression of the DNA mismatch repair genes in 5 (hMSH6 in DLD-1 and HCT-15; hMSH2 in LoVo; hMLH1 and hMSH3 in HCT-116; hMLH1 in SNU-638) out of 6 MMP cell lines. We also found a decreased expression of hMLH1 in 3 out of 10 MMP colon carcinomas, and in 6 out of 9 MMP gastric carcinomas. Our results indicate that the expression analysis of the DNA mismatch repair genes by multiplex RT-PCR method can reduce the number of genes subjected to mutational analysis and is convenient for screening the responsible DNA mismatch repair genes.
Cell Line ; Colon ; Colonic Neoplasms ; DNA Mismatch Repair* ; DNA* ; Mass Screening ; Microsatellite Repeats* ; Phenotype*

Objective: To investigate the relationship between the expression of four mismatch repair proteins (MLH1, MSH2, MSH6 and PMS2) and NTRK genetic fusions in colorectal cancer. Methods: The paraffin-embedded tissue blocks of 830 cases of colorectal cancer were collected at the Affiliated Drum Tower Hospital, Nanjing University Medical School, China, from 2015 to 2019. Immunohistochemical and fluorescence in situ hybridization(FISH) method were used respectively to detect the expression of mismatch repair proteins and the break-apart of NTRKs; and the relationship between the expression of mismatch repair proteins and the NTRK genetic fusions was analyzed. Results: The overall mismatch repair protein deficiency (dMMR) rate was 9.88% (82/830), the mismatch repair proteins proficiency (pMMR) rate was 90.12%(748/830). The total deficiency rate of MLH1 protein was 9.04% (75/830), hPMS2 protein deficiency rate was 9.04% (75/830), MSH2 protein deficiency rate was 2.53% (21/830), MSH6 protein deficiency rate was 4.10% (34/830), the deficiency rate of synchronous MLH1 and PMS2 were 8.67% (72/830) and the deficiency rate of synchronous MSH2 and MSH6 were 2.17% (18/830). The dMMR group was associated with tumor location, different histological subgroups, tumor differentiation, AJCC stage and N stage (P<0.05). There were six cases (7.32%) carrying NTRK fusion by FISH among the 82 cases of dMMR, but only seven cases (0.94%) carrying NTRK fusion among the 748 cases of PMMR. The NTRKs translocation by FISH in all 13 cases were further confirmed by next generation sequencing. Among the clinicopathological characteristics, only differentiation showed significant difference between NTRK fusion positive and negative groups (P<0.05). More importantly, NTRK fusion was enriched in dMMR group (7.32% vs. 0.94%). Conclusion: In dMMR colorectal cancer group, the prevalence of NTRK fusion is higher than that in pMMR group.
Colonic Neoplasms ; Colorectal Neoplasms/genetics* ; DNA Mismatch Repair/genetics* ; Humans ; In Situ Hybridization, Fluorescence ; Mismatch Repair Endonuclease PMS2/metabolism* ; MutL Protein Homolog 1/metabolism* ; MutS Homolog 2 Protein/metabolism*

OBJECTIVE: Women with Lynch syndrome have an increased risk of developing colorectal and gynecologic malignancies such as endometrial cancer. Complex hyperplasia has about a 30% risk of developing into endometrial cancer. The aim of this study was to determine the genetic risk for developing endometrial cancer by immunohistochemical staining of premalignant lesions for mutL homolog 1, mutS homolog 2, mutS homolog 6, and postmeiotic segregation increased 2. METHODS: Twenty cases (n=20) were selected from among patients with available sample blocks for analysis. Clinical information was obtained from medical chart review. Immunohistochemical staining was performed for all of the tumor blocks. Staining was scored based on the intensity (intensity score 0-3) . RESULTS: Among the 20 cases of complex endometrial hyperplasia, 11 (55%) patients showed loss of expression of at least one of the following proteins: mutL homolog 1, mutS homolog 2, mutS homolog 6, or postmeiotic segregation increased 2. Seven (35%) patients were negative for the expression of two or more proteins, and one patient (5%) was negative for the expression of all four proteins. CONCLUSION: More than half of the patients showed loss of expression of at least one mismatch repair protein in our study population. Genetic risk counseling and further tests are recommended for these patients.
Colorectal Neoplasms, Hereditary Nonpolyposis ; Counseling ; DNA Mismatch Repair* ; Endometrial Hyperplasia* ; Endometrial Neoplasms ; Female ; Humans ; Hyperplasia

The major risk factor for ovarian cancer (OC) is mutation of the BRCA1 or BRCA2 DNA mismatch repair genes, which occurs in approximately 10% of OC cases. Most previous studies have demonstrated that BRCA1- and BRCA2-mutated OCs are associated with better prognosis than sporadic OCs. However, information about the patterns and clinical course of the metastatic spread of BRCA-mutated OCs is limited. Herein, we describe a case of OC with a BRCA1 mutation and skin metastases in a 49-year-old patient, which to the best of our knowledge has not been reported previously.
DNA Mismatch Repair ; Humans ; Middle Aged ; Neoplasm Metastasis* ; Ovarian Neoplasms* ; Prognosis ; Risk Factors ; Skin*

Muir-Torre syndrome is defined by concurrent or sequential development of internal malignancy - most commonly colorectal cancer - and sebaceous neoplasm or multiple keratoacanthomas. Recent studies revealed it was caused by mutations in DNA mismatch repair genes, and suggested screening for mismatch repair gene defects may be of value for patients with Muir-Torre syndrome. We, herein, report a patient with Muir-Torre syndrome, who developed breast cancer and extra-ocular sebaceous carcinoma. In addition, we discussed our experience of immunohistochemical staining for mismatch repair protein with a review of the literature.
Breast ; Breast Neoplasms ; Colorectal Neoplasms ; DNA Mismatch Repair ; Humans ; Keratoacanthoma ; Mass Screening ; Muir-Torre Syndrome

BACKGROUND: To clarify the role of the mismatch repair (MMR) system in the carcinogenesis of intrahepatic cholangiocarcinoma (ICC), we investigated the microsatellite instability (MSI) status and MMR protein expression in ICC. METHODS: Thirty-six cases of ICCs were examined by microsatellite analysis for 55 markers that encompassed all of the chromosomal arms and BAT26. An immunohistochemical study for hMLH1 and hMSH2 was also performed. RESULTS: Widespread MSI (MSI-H) accompanied with a loss of hMLH1 expression was found in one case (2.8%). This MSI-H case was an adenosquamous carcinoma showing intraductal tubulopapillary adenocarcinoma and invasive adenosquamous carcinoma component. Loss of hMLH1 was noted in both components while the frequency and shifted band patterns of MSI were not identical between the components. Another 10 ICCs (27.8%) revealed low level MSI with preserved MMR gene expression. CONCLUSIONS: Our data suggested that a genetic defect in the MMR system and MSI is not a major pathway in the carcinogenesis of ICC.
Adenocarcinoma ; Arm ; Carcinogenesis ; Carcinoma, Adenosquamous ; Cholangiocarcinoma* ; DNA Mismatch Repair* ; Gene Expression ; Immunohistochemistry ; Microsatellite Instability* ; Microsatellite Repeats*

BACKGROUND/AIMS: A subset of patients may develop colorectal cancer after a colonoscopy that is negative for malignancy. These missed or de novo lesions are referred to as interval cancers. The aim of this study was to determine whether interval colon cancers are more likely to result from the loss of function of mismatch repair genes than sporadic cancers and to demonstrate microsatellite instability (MSI). METHODS: Interval cancer was defined as a cancer that was diagnosed within 5 years of a negative colonoscopy. Among the patients who underwent an operation for colorectal cancer from January 2013 to December 2014, archived cancer specimens were evaluated for MSI by sequencing microsatellite loci. RESULTS: Of the 286 colon cancers diagnosed during the study period, 25 (8.7%) represented interval cancer. MSI was found in eight of the 25 patients (32%) that presented interval cancers compared with 22 of the 261 patients (8.4%) that presented sporadic cancers (p=0.002). In the multivariable logistic regression model, MSI was associated with interval cancer (OR, 3.91; 95% confidence interval, 1.38 to 11.05). CONCLUSIONS: Interval cancers were approximately four times more likely to show high MSI than sporadic cancers. Our findings indicate that certain interval cancers may occur because of distinct biological features.
Colonic Neoplasms ; Colonoscopy ; Colorectal Neoplasms* ; DNA Mismatch Repair ; Humans ; Logistic Models ; Microsatellite Instability* ; Microsatellite Repeats*

BACKGROUND/AIMS: Serrated adenoma of the colorectum is a recently proposed entity that is characterized by a saw-toothed structure of hyperplastic polyp and also the cytologic atypia of conventional adenoma. In contrast to conventional adenomas, the molecular features of serrated adenomas have been poorly studied. METHODS: The expression of beta-catenin and the DNA mismatch repair protein hMLH1, apoptosis regulating protein Bcl-2, Bax, p53 and COX-2 were analyzed in 28 serrated adenoma specimens and 28 tubular adenoma specimens. RESULTS: No differences were observed in the frequency of beta-catenin loss in the cell membrane between the serrated and tubular adenoma specimens. The frequency of hMLH1 loss was significantly higher in the serrated adenomas than in tubular adenomas (p < 0.05). The frequency of p53 overexpression was not significantly different between the serrated and tubular adenoma specimens. The frequencies of the Bax and Bcl-2 overexpressions were significantly lower in the serrated adenomas than in the tubular adenomas. The COX-2 levels were not different between the serrated and tubular adenomas. In the serrated adenoma specimens, the frequency of Bax overexpression was reduced in the older age group (> 60 years old). In the tubular adenoma specimens, the frequency of p53 overexpression was increased in the dysplastic epithelium. CONCLUSIONS: The expressions of hMLH1, Bax and Bcl-2 were decreased in the serrated adenoma than in the tubular adenoma. Our data suggest that the serrated adenoma and tubular adenoma may have different pathway in their development. However, further studies including normal mucosa, hyperplastic polyp and cancer specimens are needed.
Adenoma* ; Apoptosis ; beta Catenin* ; Cell Membrane ; Colon* ; DNA Mismatch Repair ; Epithelium ; Humans ; Mucous Membrane ; Polyps

Hereditary non-polyposis colorectal cancer (HNPCC) is an autosomal dominantly inherited disease associated with germ-line mutations in mismatch repair genes and microsatellite instability. This article reviews the molecular biology and clinical pathology of HNPCC.
Colorectal Neoplasms, Hereditary Nonpolyposis ; diagnosis ; genetics ; pathology ; DNA Mismatch Repair ; Humans ; Microsatellite Instability

OBJECTIVEThe assay of DNA mismatch repair (MMR) activity can be used as a biomarker for environmental condition detection and human disease diagnosis. Radioactive ³²P-endlabeled DNA containing mismatch is extensively used as the substrate for MMR activity analyses. The aim of the present study is to develop a simple non-radioactive, but equally specific and sensitive method for the MMR activity assay.

METHODSA fluorescent label was chosen to replace the radioactive isotope label. Sensitive evaluation of the fluorescent label was carried out for the first time, and then the fluorescent label was compared with the isotope label in the MMR activity and DNA binding assays.

RESULTLOD (limit of detection) of the fluorescent label was about 0.1 fmol and the relative signal strength displayed a pretty good linear relationship. Moreover, the fluorescent label method has equivalent sensitivity and performance as compared with the classical radioactive method in experiments.

CONCLUSIONIn light of the sensitivity, reproducibility, safety, rapidity and long lifespan of the fluorescent label, this improved method can be applied to evaluation of biologic and toxic effects of environmental pollutants on man and other forms of life.