PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “DNA MICROSATELLITE INSTABILITY”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35Linked to original sources
PubMed2004

Analytical and statistical methods to evaluate microsatellite allelic imbalance in small amounts of DNA.

Microsatellite analysis is a powerful tool for the assessment of genetic instability and loss of heterozygosity in cancer cells. However, most human tumors harbor significant numbers of normal cells, which may contribute to false-negative results. Recent techniques based on fluorescently labeled primers and semiautomated capillary electrophoresis of polymerase chain reaction (PCR) products allow a reliable quantitative assessment of (PCR) products while requiring very small numbers of cells. We report a highly sensitive protocol for the semiautomated analysis of allelic imbalance based on time-release PCR and capillary electrophoresis. With this protocol, as few as 100 cells can be used to reliably assess allelic imbalance (AI) in DNA samples. Using a panel of seven microsatellite markers, we determined allelic variation in a large set of heterozygous lymphocyte DNA samples and examined the use of different statistical analysis techniques. Using these statistical approaches, we describe a calibration method to evaluate AI from microsatellite results. Using a simple formula, cutoff points at preset confidence levels are used to decide whether allelic imbalance exists in a given sample at the loci under investigation. Our method allows the reliable detection of AI with very small amounts of DNA, and is sufficiently quantitative to assess allelic ratios in nonclonal tissue specimens.

Allelic Imbalance↗
PubMed2000

Patterns of allelic loss at the BRCA1 locus in Arabic women with breast cancer.

Loss of heterozygosity (LOH) of BRCA1, a tumor suppressor gene, is one mechanism of genetic inactivation in both sporadic and familial forms of breast cancer. Studies reported in breast cancers from women of Northern European descent have shown LOH in 30-50% of sporadic tumors. Microsatellite instability (MSI) has served as evidence for involvement of DNA repair genes. This study investigates the extent of allelic imbalance at the BRCA1 region in Arabic women with breast cancer. Paired normal and tumor tissue were available for DNA analysis in 13 cases. Results using fluorescent tagged primers to microsatellite markers D17S1323, D17S1325 and D17S855 intragenic to BRCA1 were analyzed using an ABI 310 DNA sequencer. As compared to normal DNA, MSI and LOH were recognized as a gain and a loss, respectively, of one signal in one allele in the tumor DNA. Microsatellite analyses showed 12 of 13 (92%) cases with LOH or MSI or both. Three cases demonstrated LOH alone, 3 cases with MSI alone. Six cases indicated both LOH and MSI; 2 cases with either LOH or MSI in separate markers. The combined finding of LOH and MSI in the same marker was detected only with D17S1325 in 4/6 cases. The proportion of aberrant findings of the BRCA1 locus in breast cancer appears to be higher in Arabic women than in other populations studied to date.

Adult↗
PubMed2005

Colorectal cancer "methylator phenotype": fact or artifact?

It has been proposed that human colorectal tumors can be classified into two groups: one in which methylation is rare, and another with methylation of several loci associated with a "CpG island methylated phenotype (CIMP)," characterized by preferential proximal location in the colon, but otherwise poorly defined. There is considerable overlap between this putative methylator phenotype and the well-known mutator phenotype associated with microsatellite instability (MSI). We have examined hypermethylation of the promoter region of five genes (DAPK, MGMT, hMLH1, p16INK4a, and p14ARF) in 106 primary colorectal cancers. A graph depicting the frequency of methylated loci in the series of tumors showed a continuous, monotonically decreasing distribution quite different from the previously claimed discontinuity. We observed a significant association between the presence of three or more methylated loci and the proximal location of the tumors. However, if we remove from analysis the tumors with hMLH1 methylation or those with MSI, the significance vanishes, suggesting that the association between multiple methylations and proximal location was indirect due to the correlation with MSI. Thus, our data do not support the independent existence of the so-called methylator phenotype and suggest that it rather may represent a statistical artifact caused by confounding of associations.

Adaptor Proteins, Signal Transducing↗
PubMed1997

[Analysis of microsatellite regions and DNA ploidy pattern in signet ring cell carcinomas of the stomach].

We examined microsatellite instability (MSI) and loss of heterozygosity (LOH) in regions of several important genes in 25 signet-ring cell carcinomas of the stomach. The relationship between microsatellite analysis and DNA ploidy pattern was also investigated. MSI was observed in 15% (2/13) of early carcinomas and in 17% (2/12) of advanced carcinomas. Although LOH in the region of APC gene was found in 16% (4/25) and LOH of p53 was found in 12% (3/25), 15% (2/13) of early carcinomas and 33% (4/12) of advanced carcinomas showed LOH in regions of E-cadherin gene. Cyto-fluorometrical study revealed that 85% (11/13) of early carcinomas were diploid pattern, and aneuploid components were demonstrated in 50% (6/12) of advanced carcinomas. However, no MSI-positive cases contained aneuploid components, and in contrast, all p53-LOH cases contained aneuploid components. Our results suggest that gene abnormalities which have been frequently reported in differentiated adenocarcinomas are rare events in signet-ring cell carcinomas other than those associated with cell adhesion, and that MSI is not related to the occurrence of aneuploid cells.

Adult↗
PubMed1999

Detecting tumor-related alterations in plasma or serum DNA of patients diagnosed with breast cancer.

Chromosomal abnormalities are associated with the development of breast cancer, and widespread allelic loss or imbalance is frequently found in tumor tissues taken from patients with this disease. Using different markers, we studied a total of 61 patients (divided into three groups) for the presence of microsatellite instability and loss of heterozygosity (LOH) in plasma or serum DNA. Of the initial 27 patients, 35% of the tumor samples displayed LOH, whereas 15% had identical alterations in the corresponding plasma samples. In addition, the adjacent normal breast tissue of two patients also displayed LOH. In a second group of 11 patients, 45% of the tumors displayed LOH, and 27% displayed identical plasma DNA alterations; one case displayed an identical LOH in adjacent nontumor tissue. In a third series of 23 patients also studied with tetranucleotide repeats, 81% of the tumor samples displayed LOH, whereas 48% had LOH in the corresponding serum samples. The fact that small tumors (T1) of histoprognostic grade 1 or in situ carcinomas could present DNA alterations in the plasma/serum at an early stage, allied to the widely increased range of available microsatellite markers, suggests that plasma or serum DNA may become a useful diagnostic tool for early and potentially curable breast cancer.

Adenocarcinoma↗
PubMed2001

Microsatellite instability, MLH-1 promoter hypermethylation, and frameshift mutations at coding mononucleotide repeat microsatellites in ovarian tumors.

BACKGROUND: Microsatellite instability (MI) is frequent in endometrial carcinomas (ECs), but its occurrence in ovarian tumors is uncertain. Microsatellite instability positive ECs frequently are associated with frameshift mutations in coding mononucleotide tracts in IGFIIR, BAX, hMSH6, and hMSH3. METHODS: DNA from 52 consecutive patients with ovarian tumors (10 benign, 7 borderline, and 35 malignant) was obtained from neoplastic and normal tissue. After preliminary results, the series was expanded by including 41 additional, previously selected, endometrioid and clear cell carcinomas. Microsatellite instability analysis was assessed by evaluating three (CA)n dinucleotide repeats (D2S123, D5S346, D17S250) and two mononucleotide tracts (BAT 25 and BAT 26). Frameshift mutations at coding mononucleotide repeats (IGFIIR, TGF beta II, BAX, hMSH6, and hMSH3) were investigated by single-strand conformation polymorphism analysis and DNA sequencing. MLH-1 methylation was assessed by methylation specific PCR. RESULTS: Microsatellite instability was identified in only 2 of the 52 (3.8%) tumors of the initial series (1 endometrioid and 1 clear cell carcinoma). After expanding the initial series of 15 endometrioid and clear cell carcinomas with 41 additional endometrioid and clear cell carcinomas, MI was found in 7 of the total series of 56 endometrioid and clear cell carcinomas (12.5%). Frameshift mutations in coding mononucleotide tracts were detected in BAX (6 of 7), IGFIIR (1 of 7), and MSH3 (2 of 7). MLH-1 promoter hypermethylation was identified in three of six MI positive tumors. CONCLUSIONS: Microsatellite instability was infrequent in this series of ovarian tumors, and it was limited to endometrioid and clear cell carcinomas. Like EC, many ovarian carcinomas with MI follow the same process of MLH-1 promoter methylation and accumulation of mutations in coding mononucleotide tracts.

Adaptor Proteins, Signal Transducing↗
PubMed1998

No evidence of replication error phenotype in primary gastric lymphoma of mucosa-associated lymphoid tissue.

Replication error (RER) phenotype, caused by deficiency of DNA mismatch repair genes and revealed by widespread microsatellite instability, has been detected in subsets of a wide variety of solid tumors, but rarely in lymphomas in general. So far, the involvement of RER phenotype in the pathogenesis of gastric lymphoma of mucosa-associated lymphoid tissue (MALT) type has not been conclusively established. We therefore examined 9 microsatellite loci on 5 chromosomes [D2S123, D3S11, D3S1261, D3S1262, D3S1265, D6S262, D18S559, a CTTT(T) repeat in intron 20 of RBI gene and a CA repeat in p53 locus] in 33 cases of primary gastric MALT lymphoma for evidence of microsatellite instability by polymerase chain reaction using primers end-labeled with [gamma-33P] ATP. Although novel-length allele was observed in 7 of 33 cases (21.2%), none of these 7 cases showed changes in more than one locus. RER phenotype was scored as positive in a case when more than 1 of the 9 examined microsatellite loci showed length alterations. Accordingly, none of the 33 cases had a RER phenotype. This result suggests that the pathogenesis of gastric MALT lymphoma does not involve RER phenotype. It is consistent with the general observations in lymphomas, but is highly in contrast to a previous report showing more than 50% of MALT lymphomas with the RER phenotype.

DNA Ligases↗
PubMed1999

Microsatellite instability in gastric MALT lymphomas and other associated neoplasms.

BACKGROUND: Microsatellite instability (MSI), caused by a reduced efficacy of the DNA mismatch repair (MMR) machinery, represents a type of genomic instability frequently detected in HNPCC spectrum cancers and in a subset of sporadic carcinomas. The involvement of MSI in the pathogenesis of gastric lymphoma of mucosa-associated lymphoid tissue (MALT) has never been conclusively investigated. In this study, we tested the presence of MSI in tumor samples of patients harboring both MALT lymphomas and other types of malignancies. MATERIALS AND METHODS: We examined 10 microsatellite loci (D3S11, D3S1261, D3S1265, D6S262, D6S193, BAT-26, BAT-25, D17S250, APC, D2S123) out of a total of 34 primary tumors from 14 patients with MALT lymphomas and one or more additional neoplasms. The patients' MSI results were also tested for an association with a positive family history of cancer. RESULTS: MSI, defined by the presence of microsatellite alterations in more than 40% of the examined loci, was scored negative in all tumors studied, and pedigree analysis failed to identify any condition of familial cancer among the patients examined. CONCLUSIONS: The present study suggests that defects in DNA mismatch repair do not contribute significantly to the molecular pathogenesis of MALT lymphomas and associated neoplasms.

Colorectal Neoplasms, Hereditary Nonpolyposis↗
PubMed2000

Multiple tumors and a novel E2F-4 mutation. A case report.

Defects in the DNA mismatch-repair are known to cause microsatellite instability (MSI) in hereditary nonpolyposis colorectal cancer (HNPCC) as well as sporadic colorectal cancer (CRC). We previously reported that the E2F-4 gene, which encodes an important transcription factor in cell cycle control, had frequent tumor-specific mutations at the trinucleotide coding region microsatellite (CAG)n in a subset of human sporadic CRC with MSI. We report a 65-year-old man with triple tumors in the abdomen, including colon cancer, stomach cancer, and lipoma of the retroperitoneum, with the analysis of E2F-4 mutation. We report the first case of colon cancer with a homozygous E2F-4 mutation along with a detailed analysis of other cancer related genes as well as a prognosis.

Adult↗
PubMed1997

Genomic instability, as measured by microsatellite alterations, is not associated with liver tumor development in the genetically susceptible B6C3F1 mouse.

Certain human heritable forms of colon cancer have characteristically high frequencies of microsatellite alterations. These microsatellite changes are markers of genomic instability and the direct consequence of mutations in genes involved with DNA mismatch repair processes, which are in part responsible for maintaining the sequence integrity of the genome. Given that the B6C3F1 mouse is genetically predisposed to develop liver tumors we were interested in determining whether tumors derived in this strain of mouse may contain alterations in microsatellite sequences. The analysis of 48 tumors at 24 different microsatellite loci revealed that microsatellite alterations were detected in 12 of 48 tumors (25%). Although this frequency is relatively high, 11 of the 12 tumors exhibited only a single alteration and in 10 of those tumors this change was at the same microsatellite locus. Microsatellite alterations were also detected in the DNA isolated from 6 of 22 (27%) normal liver tissues with 4 of the 6 occurring at the same locus where the majority of changes were observed in the tumors. Based on these results, we conclude that the microsatellite alterations present in the mouse liver tumor tissue are most likely the result of spontaneous mutational events. Consequently, the genomic instability operational in a particular type of hereditary human colon cancer does not appear to be operational in the genetically predisposed B6C3F1 mouse liver. In addition, we demonstrated that the activation of the H-ras gene, which causes some forms of genetic instability in vitro, does not contribute to genetic instability within liver tumors as measured by microsatellite alterations.

Animals↗
PubMed2000

[beta-Catenine as a genomic target of high-grade microsatellite instability in colorectal cancer].

AIMS: Various inherited and acquired alterations affecting the genes and gene products of the WNT pathway appear to be involved in the different molecular routes leading to colorectal cancer (CRC). This study was initiated to investigate the prevalence of somatic mutations in the beta-catenin gene (CTNNB1) and the associated pathology in CRC with defective DNA mismatch repair. METHODS: Paraffin and/or frozen sections of 33 primary CRC (including any liver and lymph node metastases present) with high-grade microsatellite instability (MSI-H; i.e. with > or = 5 unstable microsatellite markers of 10 tested) were polytopically fractionated by microdissection. Genomic and c-DNA samples were sequenced across exons 2-4 of CTNNB1 and the expression patterns of beta-catenin (beta-C) analyzed by immunohistology and Western blotting. RESULTS: Seven somatic mutations affecting phosphorylation sites of exon 3 (2 deletions also encompassing parts of either intron 2 or exon 4 [delta X2/3 bzw. delta X3/4] and 5 missense mutations [2 x T41A, 2 x S45F, S45P]) were identified. Two mutations (delta X3/4 and S45F) were concordantly present in CRC primaries and their respective metastases whereas the S45P mutation was restricted to a hepatic metastasis. In the delta X2/3 CRC primary only a shortened 66 kD CTNNB1 gene product was present while its associated liver metastasis showed a total loss of beta-C expression. CONCLUSIONS: Both exon 3 and the entire locus coding for beta-C are somatically altered in approximately 20% of CRC with MSI-H at different stages of tumor progression. Thus CTNNB1 appears to be a genomic target for complex oncogenic mutations and deletional processes in a substantial fraction of this molecular subset of CRC.

Cadherins↗
PubMed2005

Prognostic and predictive relevance of microsatellite instability in colorectal cancer.

Microsatellite instability (MSI) is the phenotypic hallmark of a deficient DNA mismatch-repair system, observed in 10-20% of sporadic colorectal cancers (CRC). Since the prognostic and predictive value of this genetic alteration has been assessed mainly in non-randomised, uncontrolled studies, we investigated the potential of MSI to predict patient survival and response to adjuvant chemotherapy in tumour specimens from a randomised trial of the Swiss Group for Clinical Cancer Research (SAKK) that tested the value of 5-fluorouracil/mitomycin adjuvant chemotherapy. MSI status was determined in matched normal and tumour tissue samples from 160 patients using a panel of 9 microsatellite markers. There was no correlation between high frequency MSI (MSI-H) and overall (OS) or disease-free survival (DFS) in the untreated control group of patients (HR=1.13, p=0.80; and HR=0.89, p=0.81, respectively). Furthermore, MSI-H phenotype did not predict for a larger benefit of adjuvant chemotherapy on OS or DFS (HR=0.49, p=0.41; HR=0.49, p=0.41, respectively), making a potential value of this molecular marker as a predictive factor in CRC unlikely. Our data do not confirm the prognostic relevance of MSI-H status in colorectal cancer patients found in some other studies. In addition, microsatellite instability did not correlate with the extent of chemotherapy benefit, although we observed a statistically non-significant favourable impact of 5-FU-based treatment in the MSI-H group compared to MSI-L/MSS patients. Larger prospective randomised trials are required to conclusively establish a potential clinical significance of MSI in colorectal cancer.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

Genomic instability in the type II TGF-beta1 receptor gene in atherosclerotic and restenotic vascular cells.

Cells proliferating from human atherosclerotic lesions are resistant to the antiproliferative effect of TGF-beta1, a key factor in wound repair. DNA from human atherosclerotic and restenotic lesions was used to test the hypothesis that microsatellite instability leads to specific loss of the Type II receptor for TGF-beta1 (TbetaR-II), causing acquired resistance to TGF-beta1. High fidelity PCR and restriction analysis was adapted to analyze deletions in an A10 microsatellite within TbetaR-II. DNA from lesions, and cells grown from lesions, showed acquired 1 and 2 bp deletions in TbetaR-II, while microsatellites in the hMSH3 and hMSH6 genes, and hypermutable regions of p53 were unaffected. Sequencing confirmed that these deletions occurred principally in the replication error-prone A10 microsatellite region, though nonmicrosatellite mutations were observed. The mutations could be identified within specific patches of the lesion, while the surrounding tissue, or unaffected arteries, exhibited the wild-type genotype. This microsatellite deletion causes frameshift loss of receptor function, and thus, resistance to the antiproliferative and apoptotic effects of TGF-beta1. We propose that microsatellite instability in TbetaR-II disables growth inhibitory pathways, allowing monoclonal selection of a disease-prone cell type within some vascular lesions.

Arteriosclerosis↗
PubMed1999

Microsatellite instability is infrequent in azoxymethane-induced rat intestinal tumors: An assessment by capillary electrophoresis.

A rat model of colon cancer in which tumors are induced by azoxymethane (AOM) is frequently used to study putative environmental agents that may modify the risk of human colon cancer development. In order to evaluate the usefulness of this model for human risk assessment, a comparison of the molecular changes associated with tumorigenesis in the rat model with those in human colon cancer is desirable. Microsatellite instability (MSI), an alteration in length of short repetitive DNA sequences associated with defective DNA mismatch repair, is an important molecular characteristic of many human colon tumors. Intestinal tumors were induced in male Fischer 344 rats injected with 15 mg/kg body wt AOM in four weekly doses. Thirteen intestinal tumors were examined for MSI at 10 different microsatellite loci, using a capillary electrophoresis (CE) method for accurate assessment of DNA length. This method was shown to have a resolution of 1 bp for a 140-bp PCR product and to be capable of detecting one mutant sequence within a background of 10 wild-type sequences. The CE method also readily distinguished a known MSI-positive human tumor sample from its matching control sample. Among the 13 rat intestinal tumors examined, only one had MSI, which was present at only a single locus. We conclude that, unlike sporadic human colon tumors in which 15-30% of tumors have MSI (usually at multiple loci), MSI is very rare in AOM-induced rat intestinal tumors.

Animals↗
PubMed2000

Implications of low COX-2 expression in colorectal neoplasms with defective DNA mismatch repair.

Most colorectal adenomas and carcinomas arise in the setting of chromosomal instability and progressive loss of heterozygosity. Approximately 15-20% of colorectal neoplasms arise through a distinct genetic pathway characterized by microsatellite instability (MSI) and frequent loss of expression of one of the DNA mismatch repair enzymes, most often hMLH1 or hMSH2. These distinct genetic pathways are reflected by differences in tumor histopathology, distribution in the colon, prognosis, and dwell time required for progression from adenoma to carcinoma. The molecular and clinical distinctions between these tumors suggest that they are biologically distinct and may respond differently to therapeutic and chemopreventive agents. Recently, we showed that expression of a putative chemopreventive target, COX-2, is significantly reduced in colorectal cancers with defective mismatch repair as assessed by MSI and absent staining for hMLH1 and/or hMSH2. The mechanisms responsible for low COX-2 expression in tumors with MSI remain unknown, but they may be linked to molecular events giving rise to MSI tumors. Although the clinical implications of these observations are unknown, the presence of MSI should be considered an important variable when assessing the efficacy of COX-2 inhibitors in chemoprevention trials.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Repeated sequences in CASPASE-5 and FANCD2 but not NF1 are targets for mutation in microsatellite-unstable acute leukemia/myelodysplastic syndrome.

Microsatellite instability (MSI) in tumors is diagnostic for inactive DNA mismatch repair. It is widespread among some tumor types, such as colorectal or endometrial carcinoma, but is rarely found in leukemia. Therapy-related acute myeloid leukemia/myelodysplastic syndrome (tAML/MDS) is an exception, and MSI is frequent in tAML/MDS following cancer chemotherapy or organ transplantation. The development of MSI+ tumors is associated with an accumulation of insertion/deletion mutations in repetitive sequences. These events can cause inactivating frameshifts or loss of expression of key growth control proteins. We examined established MSI+ cell lines and tAML/MDS cases for frameshift-like mutations of repetitive sequences in several genes that have known, or suspected, relevance to leukemia. CASPASE-5, an acknowledged frameshift target in MSI+ gastrointestinal tract tumors, was frequently mutated in MSI+ cell lines (67%) and in tAML/MDS (29%). Frameshift-like mutations were also observed in the NF1 and FANCD2 genes that are associated with genetic conditions conferring a predisposition to leukemia. Both genes were frequent targets for mutation in MSI+ cell lines and colorectal carcinomas. FANCD2 mutations were also common in MSI+ tAML/MDS, although NF1 mutations were not observed. A novel FANCD2 polymorphism was also identified.

Alleles↗
PubMed1998

Clear cell sarcoma or malignant melanoma of soft parts: molecular analysis of microsatellite instability with clinical correlation.

Malignant melanoma of soft parts, also termed clear cell sarcoma (CCS), is a rare malignancy of neural crest origin which is different from cutaneous malignant melanoma. Although a translocation involving chromosomes 12 and 22 is characteristic of clear cell sarcoma and not malignant melanoma, there are a paucity of methods to differentiate the two. Therefore, a study of microsatellite instability (MIN) was undertaken to determine if mechanisms of DNA mismatch repair can differentiate these malignancies. MIN has been described in a variety of malignancies including 25% of malignant melanomas. Paraffin-embedded neoplastic and non-neoplastic cells were obtained from 11 individuals (five males; six females; age range from seven to 60 years) with CCS. Isolated DNA was PCR amplified at 17 separate microsatellite loci using radioactive-labeled primers. Tumor tissue was compared to normal tissue for each analysis. No MIN was detected. Loss of heterozygosity was detected in only one patient at a single locus (IFNA). The lack of MIN in clear cell sarcoma further defines the distinction between this tumor and malignant melanoma. Clinically, local recurrence and metastasis were indicators of poor outcome. The size of the tumor was not a significant prognostic indicator. Local recurrence, satellitosis, or nodal metastasis was not proven to be uniformly fatal. Utilization of chemotherapy and/or radiation demonstrated no obvious survival advantage. The histologic parameters of mitotic rate and the presence of necrosis were not prognostic. Limb-preserving surgical procedures were as effective as amputation for local disease control. The actuarial survival rate was calculated to be 48% at five years.

Adolescent↗