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Results for “DNA MICROSATELLITE INSTABILITY”

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PubMed2006

In vitro analysis of genomic instability triggered by BRCA1 missense mutations.

The BRCA1 tumor suppressor gene encodes a phosphoprotein involved in many cellular key functions including DNA repair, transcription regulation, cell-cycle control and apoptosis. Most of these functions are strictly related to the ability of BRCA1 to interact with the other partners of a multimeric complex called BASC. Among these components, an important role is played by the human homolog of the bacterial MutL, MLH1. In this study, we have identified the BRCA1 binding domains to MLH1 and demonstrated that three distinct mutations in one of these interaction domains can produce, in vitro, a microsatellite instability phenotype, one of the hallmarks of an imbalance in the mismatch DNA repair machinery. These data support a model in which a structural modification in a critical domain of the BRCA1 gene product secondary to single amino acid mutations, may be able, per se, to impair the DNA damage response pathway, inducing genomic instability and eventually leading to breast carcinogenesis.

Adaptor Proteins, Signal Transducing↗

PubMed2000

Metachronous carcinoma of the vulva and fallopian tube.

BACKGROUND: Metachronous carcinoma of the vulva and fallopian tube is an unusual co-occurrence of gynecological malignancies. A report of such a case that developed and recurred over a 7-year period is presented. CASE: A 53-year-old G3P3 female presented with a verrucous carcinoma of the vulva and a serous papillary adenocarcinoma of the left fallopian tube metachronously. To investigate a possible association between the co-occurrence of the rare neoplasms and factors associated with multiple gynecological malignancies, we analyzed the status of human papillomavirus infection and DNA mismatch repair deficiency as indicated by microsatellite instability. All samples analyzed were negative for these factors. CONCLUSION: The present results support the possibility that metachronous carcinomas of the vulva and fallopian tube involve unknown etiological factors or arise independently.

Adenocarcinoma, Papillary↗

PubMed2005

Microsatellite instability testing in colorectal carcinoma: choice of markers affects sensitivity of detection of mismatch repair-deficient tumors.

PURPOSE: Microsatellite instability (MSI) is found in 10% to 15% of sporadic colorectal tumors and is usually caused by defects in DNA mismatch repair (MMR). In 1997, a panel of microsatellite markers including mononucleotide and dinucleotide repeats was recommended by a National Cancer Institute workshop on MSI. We investigated the relationship between instability of these markers and MMR protein expression in a cohort of sporadic colorectal cancer patients. EXPERIMENTAL DESIGN: Paraffin sections of normal and tumor tissue from 262 colorectal cancer patients were examined for MSI status by PCR amplification and for MMR protein expression using antibodies against hMLH1, hPMS2, hMSH2, and hMSH6. RESULTS: Twenty-six (10%) of the patients studied had tumors with a high level of MSI (MSI-H). The frequencies of MSI were the same in African-American and Caucasian patients. Each of the MSI-H tumors had mutations in both mononucleotide and dinucleotide repeats and had loss of MMR protein expression, as did two tumors that had low levels of MSI (MSI-L). These two MSI-L tumors exhibited mutations in mononucleotide repeats only, whereas eight of the other nine MSI-L tumors had mutations in just a single dinucleotide repeat. There was not a statistically significant difference in outcomes between patients whose tumors were MMR-positive or MMR-negative, although there was a slight trend toward improved survival among those with MMR-deficient tumors. CONCLUSIONS: The choice of microsatellite markers is important for MSI testing. Examination of mononucleotide repeats is sufficient for detection of tumors with MMR defects, whereas instability only in dinucleotides is characteristic of MSI-L/MMR-positive tumors.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Extensive somatic microsatellite mutations in normal human tissue.

Microsatellite (MS) instability occurs in tumors with DNA mismatch repair (MMR) deficiencies but is typically absent in adjacent normal tissue. However, MS mutations have been observed in normal tissues from rare individuals with congenital MMR deficiencies. Autopsy tissues from a 4-year-old with congenital MMR deficiency (MLH1-/-) were examined for MS mutations. Insertions and deletions were observed in CA-repeat MS loci. Approximately 0.26 to 1.4 mutations per MS locus per cell were estimated to be present in normal heart, lymph node, kidney, and bladder epithelium. These findings illustrate that phenotypically normal MMR-deficient cells commonly accumulate MS mutations. Loss of MMR and the accumulation of some MS mutations may occur early in MMR-deficient tumor progression, even before a gatekeeper mutation.

Adaptor Proteins, Signal Transducing↗

PubMed1997

The insulin-like growth factor II receptor gene is mutated in genetically unstable cancers of the endometrium, stomach, and colorectum.

Disruption of the DNA mismatch repair system, characterized by microsatellite instability (MI), plays an important role in the course of human carcinogenesis. Repetitive sequences constitute targets for mutation in MI+ cells, and frequent mutations have indeed been reported in such regions within the transforming growth factor beta receptor II (RII) gene in genetically unstable colorectal and gastric cancers. However, other genes that are targets for mutations in MI+ cells during the course of carcinogenesis have proven elusive. Because the insulin-like growth factor II receptor (IGFIIR) gene contains several repetitive sequences within its coding region, we examined mutations of this gene in MI+ cancers occurring at various primary sites. We found frameshift mutations in the poly(G)8 tract of IGFIIR in eight tumors, all of which were MI+: 4 of 26 (15%) MI+ endometrial cancers, 3 of 12 (25%) MI+ gastric cancers, and 1 of 18 (6%) MI+ colorectal cancers. In contrast, no mutation was found in 51 pancreatic cancers, 7 of which (14%) were MI+. These results implicate abnormal IGFIIR-mediated growth control in carcinogenesis involving the endometrium, stomach, and colorectum but not the pancreas.

Breast Neoplasms↗

PubMed2000

Microsatellite instability is a favorable prognostic indicator in patients with colorectal cancer receiving chemotherapy.

BACKGROUND & AIMS: Adjuvant 5-fluorouracil (5-FU)-based chemotherapy is standard treatment for stage C colorectal cancer (CRC). Approximately 12% of CRCs are characterized by microsatellite instability (MSI), a hallmark of a DNA mismatch repair defect. We investigated the safety of adjuvant 5-FU-based chemotherapy for MSI(+) CRC and compared the prognosis of MSI(+) and MSI(-) CRC patients receiving adjuvant therapy. METHODS: Previously, a prospective series consisting of 1044 consecutive CRCs has been collected and the MSI status of each sample determined. Patients with stage C cancer who had received adjuvant chemotherapy (n = 95) were followed up for 7-63 months (median, 31 months) after surgery. RESULTS: No unexpected or serious adverse effects were observed when 5-FU-based chemotherapy was used as adjuvant treatment for MSI(+) CRC. Three- year recurrence-free survival was 90% and 43% in the MSI(+) (n = 11) and MSI(-) (n = 84) groups, respectively (P = 0.020). CONCLUSIONS: Adjuvant 5-FU-based chemotherapy is feasible for both MSI(+) and MSI(-) CRCs, and patients with MSI(+) CRC who receive adjuvant therapy have an excellent prognosis.

Adult↗

PubMed1998

Genomic loci susceptible to replication errors in cancer cells.

Microsatellite instability due to a deficiency in DNA mismatch repair is characteristic of a replication error (RER) phenotype. This widespread genomic instability is well documented in hereditary non-polyposis colon cancer (HNPCC) as well as subsets of sporadic carcinomas. Features of the RER phenotype such as the early appearance in tumour development and better prognosis of RER+ colorectal tumours render its examination important for cancer patients. Recently, we identified four loci that were shown to be highly susceptible to RER in cancer cells. Here, we used these loci to detect the RER phenotype in sporadic carcinomas of colon, breast, lung, endometrium and ovary. Replication errors revealed by these four markers followed the same tumour specificity as observed in HNPCC patients. In particular, 24% (6/25) of colorectal, 33% (4/12) of endometrial and 17% (2/12) of ovarian cancers displayed the RER phenotype characterized by an increased allelic mobility, whereas none of the breast (n = 22) and the lung (n = 27) carcinomas were found to be unstable. Assaying RERs sensitive loci provides us with a useful diagnostic tool for HNPCC-like sporadic tumours.

Colonic Neoplasms↗

PubMed2005

Microsatellite instability: an indirect assay to detect defects in the cellular mismatch repair machinery.

The DNA mismatch repair (MMR) pathway plays a prominent role in the correction of errors made during DNA replication and genetic recombination and in the repair of small deletions and loops in DNA. Mismatched nucleotides can occur by replication error, damage to nucleotide precursors, damage to DNA, or during heteroduplex formation between two homologous DNA molecules in the process of genetic recombination. Defects in MMR can precipitate instability in simple sequence repeats (SSRs), also referred to as microsatellite instability (MSI), which appears to be important in certain types of cancers, both spontaneous and hereditary. Variation in the highly polymorphic alleles of specific microsatellite repeats can be identified using PCR with primers derived from the unique flanking sequences. These PCR products are analyzed on denaturing polyacrylamide gels to resolve differences in allele sizes of more than 2 bp. Although (CA)n repeats are the most abundant class among dinucleotide SSRs, trinucleotide and tetranucleotide repeats are also frequent. These polymorphic repeats have the advantage of producing band patterns that are easy to analyze and can be used as an indication of a possible MMR defect in a cell. The presumed association between such allelic variation and an MMR defect should be confirmed by molecular analysis of the structure and/or expression of MMR genes.

Animals↗

PubMed2003

High throughput detection of microsatellite instability by denaturing high-performance liquid chromatography.

Microsatellite instability (MSI) is a hallmark of the DNA replication error phenotype, due to the inactivation of mismatch repair genes. MSI has been implicated in colon and many other gastrointestinal cancers. MSI usually can be analyzed by PCR amplification of microsatellite markers followed by electrophoresis and detected using autoradiography or fluorescence techniques. We report here a novel method for high-throughput detection of MSI using denaturing high performance liquid chromatography (DHPLC). Amplification of two mononucleotide markers (BAT25 and BAT26) by polymerase chain reaction (PCR) is followed by DHPLC analysis to display alteration in the length of repetitive sequences. These two markers were tested in 84 colorectal cancer samples confirmed to be 44 MSI-H and 40 MSI-L or MSS, previously defined by multiple microsatellite markers and/or by immunohistochemical analyses of MLH1 and MSH2 proteins. Among 44 MSI-H samples, sequence variations in BAT26 and BAT25 were detected in 44 (100%) and 43 (98%), respectively, while no sequence variation in the two markers was detected in 40 MSI-L or MSS samples. A total of 96 gastric cancers and their matched normal tissues were then analyzed for MSI-H using this method. Sequence variations in BAT26 and BAT25 were detected in nine (9.4%) samples. Seven of the nine cases were shown unstable at both BAT26 and BAT25; one each was unstable at BAT26 or BAT25. These results were confirmed by autoradiography analyses. Together, our results demonstrate high sensitivity and specificity of DHPLC in the analysis of sequence variations in BAT25 and BAT26 to determine MSI status. This simple, efficient, and high-throughput approach will facilitate analysis of MSI in large sample sets of any cancers.

Chromatography, High Pressure Liquid↗

PubMed2004

Quasimonomorphic mononucleotide repeats for high-level microsatellite instability analysis.

Microsatellite instability (MSI) analysis is becoming more and more important to detect sporadic primary tumors of the MSI phenotype as well as in helping to determine Hereditary Non-Polyposis Colorectal Cancer (HNPCC) cases. After some years of conflicting data due to the absence of consensus markers for the MSI phenotype, a meeting held in Bethesda to clarify the situation proposed a set of 5 microsatellites (2 mononucleotide repeats and 3 dinucleotide repeats) to determine MSI tumors. A second Bethesda consensus meeting was held at the end of 2002. It was discussed here that the 1998 microsatellite panel could underestimate high-level MSI tumors and overestimate low-level MSI tumors. Amongst the suggested changes was the exclusive use of mononucleotide repeats in place of dinucleotide repeats. We have already proposed a pentaplex MSI screening test comprising 5 quasimonomorphic mononucleotide repeats. This article compares the advantages of mono or dinucleotide repeats in determining microsatellite instability.

Alleles↗

PubMed1997

Mutator phenotype in Msh2-deficient murine embryonic fibroblasts.

Embryonic fibroblast cell lines were established from mice deficient, heterozygous, or proficient for Msh2, one of the three known DNA mismatch repair genes involved in hereditary nonpolyposis colon cancer (HNPCC). Cell lines were established by transfection of primary mouse embryo fibroblasts with E7 and Ras oncogenes or mutant p53. Spontaneously immortalized cells derived from the primary cultures were also studied. To determine whether these cells developed a mutator phenotype similar to that found in colon cancer cells deficient in mismatch repair, we measured mutation rates, microsatellite instability, and sensitivities to a range of DNA-damaging agents. The mutator phenotype detected in the E7 and Ras or mutant p53-immortalized Msh2-/- mouse cells was similar to that found in human mismatch repair-deficient colorectal carcinoma cell lines. Mutation rates to ouabain resistance were increased 8-12-fold relative to lines from Msh2+/+ mice, and microsatellite instability was detectable in 12-18% of subclones derived from the Msh2-/- line but was undetectable in subclones developed from the Msh2+/+ line. Furthermore, E7 and Ras or spontaneously immortalized Msh2-/- cells were significantly more resistant to the cytotoxic effects of 6-thioguanine relative to Msh2+/+ cells. In contrast, these lines showed various responses to UV light and cis-platinum, suggesting that mismatch repair deficiency was not the sole determinant for sensitivity to these DNA-damaging agents. Particular attention was paid to the properties of cells heterozygous for the Msh2 mutant gene, which would mimic the situation of an HNPCC carrier. However, our studies failed to reveal any properties of these cells that might provide a growth advantage or predispose them for the acquisition of further mutations. This observation is consistent with the model that inactivation of the wild-type Msh2 allele is a critical step for tumorigenesis in HNPCC patients.

Animals↗

PubMed2003

Drug treatment in the development of mismatch repair defective acute leukemia and myelodysplastic syndrome.

DNA from therapy-related acute leukemia/myelodysplastic syndrome cases (tAL/MDS) from the GIMEMA [Gruppo Italiano Malattie Ematologiche Maligne dell'Adulto] Archive was examined for the microsatellite instability (MSI(+)) phenotype that is diagnostic for defective DNA mismatch repair. More than 60% (16/25) of tAL/MDS cases were MSI(+) in contrast to <4% (0/28) of de novo cases. hMLH1 gene silencing was rare and evidence of promoter methylation was found in less than one-third of the MSI(+) cases. Among the GIMEMA patients who had been treated for breast cancer there was an apparent trend towards early onset primary breast disease. This suggests that there might be common predisposing factors for breast cancer and tAL/MDS. There were also three examples of mutations in the MRE11 gene among the 25 tAL/MDS cases suggesting that defective recombinational DNA repair may promote the development of secondary malignancy. MSI(+) tAL/MDS was significantly associated with previous chemotherapy and the frequency of MSI(+) among radiotherapy patients was considerably lower. In view of the established relationship between drug resistance and mismatch repair defects, we suggest that selection for therapeutic drug resistance may contribute to the incidence of MSI(+) tAL/MDS.

Acute Disease↗

PubMed2002

Frequent microsatellite instability in sporadic tumors of the upper urinary tract.

Urothelial carcinoma of the renal pelvis and ureter may develop sporadically or as a manifestation of hereditary nonpolyposis colorectal cancer. The majority of hereditary nonpolyposis colorectal cancer is caused by mutation of the human DNA mismatch repair (MMR) genes and is detected by associated microsatellite instability (MSI). Seventy-three unselected urothelial carcinomas of the ureter and/or renal pelvis were screened for MSI using the National Cancer Institute-designated reference panel (plus BAT40). Instability of at least two microsatellite markers (MSI-high) was detected in 15 samples (21%). Immunohistochemical staining of the MMR proteins (hMSH2, hMLH1, or hMSH6) was absent in 13 of 15 (87%) MSI tumors, and alteration of coding sequence microsatellites (TGFbetaRII, Bax, hMSH3, and hMSH6) was found at frequencies of 7-33% in these samples. Tumors with MSI had significantly different clinical and histopathological features including higher prevalence in female patients, low tumor stage and grade, and a papillary and frequently inverted growth pattern. Our results suggest a molecular pathway of tumorigenesis that is similar to MMR-deficient colorectal cancers and consistent with the notion that the site distributions of hereditary or sporadic MSI-high tumors may reflect tissue-specific susceptibility to lesions processed by the MMR machinery.

Adaptor Proteins, Signal Transducing↗

PubMed1999

Microsatellite instability in lymphoid leukemia and lymphoma cell lines but not in myeloid leukemia cell lines.

Microsatellite instability (MSI) represents a defect in the DNA mismatch repair system and has been shown to take part in the genesis and/or progression of several human malignancies. In hematological malignancies, the relevance of MSI has been a matter of controversy. Therefore, 29 microsatellite loci were examined for MSI in 57 leukemia and lymphoma cell lines by PCR analysis. Ladder formation of bands representing MSI was observed at multiple loci in 6 of 24 lymphoid leukemia/lymphoma cell lines and in 0 of 33 myeloid leukemia cell lines. Analysis for the BAT-26 and BAT-25 loci confirmed the presence of MSI in five of six lymphoid cell lines exhibiting ladder formation of bands. Thus, at least 5 out of 24 (21%) lymphoid leukemia/lymphoma cell lines were considered as being MSI-positive. These results indicate that MSI contributes to the development of lymphoid but not to myeloid malignancies.

Humans↗

PubMed2003

Assessment of microsatellite instability in bladder and thyroid malignancies.

Microsatellite instability (MSI) is an indicator of a defective DNA mismatch repair system (MMR) that results from somatic mutations. The present work has been planned to investigate MSI and its clinical significance in human urinary bladder and thyroid cancers in Indian patients. Tumor tissues of histologically confirmed cases of urinary bladder and thyroid cancers, respectively, were obtained. Clinical data on tumor stage and histopathological grades were recorded. Corresponding matched peripheral blood was taken as a control. Genomic DNA was isolated from the tumor tissues and blood using a standard phenol-chloroform extraction method. Polymerase chain reaction was done to amplify mononucleotide microsatellite markers, BAT-26, BAT-40, TGFbetaRII, IGFIIR, hMSH3, and Bax by using specific primer sequences. For analysis of allelic patterns, the PCR products were run on 8% denaturing Polyacrylamide gel and sizing was done using a pUC18 sequencing ladder. The instability with BAT-26 and BAT-40 was found to be 20% and 45% in urinary bladder and 33% and 19% in thyroid cancers, respectively. However, no instability was observed with the other four-mononucleotide markers in either of the cancers studied. Eighty-three percent of the unstable urinary bladder cancers were found to have a high grade in a superficial group, whereas only 27% MSI+ve were muscle invasive cancers. Forty percent of unstable thyroid lesions were found to be at high risk of developing metastasis. Association of BAT-26 and BAT-40 instabilities with high grade tumors as well as risk tumors may help in choosing a more definite therapy at the outset.

Base Pair Mismatch↗

PubMed2000

Induction of microsatellite mutations by oxidative agents in human lung cancer cell lines.

Genomic instability has been associated with cancer development. Oxidative DNA damage seems to contribute to genetic instability observed in cancer. We have used human lung cancer cell lines carrying a plasmid vector containing a (CA)(13) microsatellite sequence to study frameshift mutations mediated by ROS-generating chemicals paraquat and hydrogen peroxide. Exposure of the cells to both paraquat and hydrogen peroxide resulted in significantly higher mutation frequencies compared with untreated control cells. Mutation frequencies up to 27-fold higher than the spontaneous mutation frequencies were obtained. The majority of the reversion mutants contained frameshift mutations within the target sequence. However, the pattern of deletions and additions was significantly different in the two cell lines. These results indicate that oxidative damage may play a role in instability of microsatellite sequences in vivo.

Cinnamates↗

PubMed2001

[Hereditary nonpolyposis colorectal carcinoma (HNPCC). Current review of etiology, clinical aspects, diagnosis and therapy].

ETIOLOGY: The hereditary non-polyposis colorectal carcinoma (HNPCC) is the most common monogenic colon cancer syndrome. It is characterized by autosomal dominant inherited cancers of the colon, rectum, and the endometrium. Less frequently, cancer of the upper gastrointestinal tract, the hepatobiliary system and the urogenital tract may occur. Typical characteristics are an early onset, usually before the age of 50, manifestation of colorectal cancer proximal of the splenic flexure, and often poorly differentiated carcinomas. GENETICS: Recently, germline mutations in several DNA mismatch repair genes have been identified as the molecular basis of HNPCC, resulting in deficient DNA repair and genetic instability, indicated by microsatellite instability in tumor specimens. DIAGNOSIS: New insights into pathogenesis, clinical features, and diagnosis of HNPCC have improved the identification of HNPCC patients and persons at risk. Diagnosis of HNPCC is primarily based on family history and is complemented by molecular findings. After detection of the underlying germline mutation in families with HNPCC, screening procedures can be restricted to mutation carriers. TREATMENT: Recommendations for therapy and prevention are in part controversial and are under investigation in several studies.

Adult↗

PubMed2025

The protective role of γδ T cells in endometrial cancer.

Γδ T cells are non-conventional T cells that are not MHC restricted and have T cell receptors (TCRs) that are stimulated by phosphoantigens, stress-induced proteins, lipids, and other antigens. These cells are prognostic across cancer types in The Cancer Genome Atlas (TCGA) but have not been well studied in endometrial cancer, which has a rising incidence and mortality rate. Endometrial cancer patients have variable responses to checkpoint inhibitors which are related to the molecular subtype of their cancer. As such, there is a pressing need to understand the immune microenvironment in endometrial cancer. This study addresses this gap in knowledge by investigating γδ T cell repertoires and transcriptomes in this disease site. γδ T cell repertoires were obtained for 543 endometrial cancer patients within the TCGA and from 5 endometrial cancer patients in the single cell dataset SRP349751 using TRUST4. GLIPH2 was used to identify TCRs predicted to bind the same antigen. Transcriptomes were investigated in the single cell dataset. DNA Polymerase Epsilon Exonuclease (POLE) and Microsatellite Instability High (MSI-H) endometrial cancer subtypes had the most γδ T cell infiltration. Vδ1 and Vδ3 γδ T cell infiltration was prognostic independent of stage and molecular subtype. GLIPH2 analysis revealed TCRδ motifs for TDK, YTD, and GEL were public across all four molecular subtypes and were present in the single cell data set. Vδ1 γδ T cell transcriptomes were associated with cytotoxicity and recent TCR stimulation. These data support further investigation of immunotherapies targeting γδ T cells in endometrial cancer.

Humans↗