Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Desmoplastic small round cell tumor is a recently described entity associated with fusion of the EWS and WT1 genes and with expression of a chimeric transcript. To investigate the structure and potential diagnostic utility of the detection of EWS-WT1 chimeric RNA in desmoplastic small round cell tumor, 12 examples of this entity and 49 other tumors that enter in its differential diagnosis were studied by reverse transcriptase polymerase chain reaction for the presence of EWS-WT1, EWS-FLI-1, PAX3-FKHR, and PAX7-FKHR chimeric transcripts. EWS-WT1 was detected in 11 of 12 desmoplastic small round cell tumors but not in any other tumor type studied, including 17 Wilms' tumors, 10 Ewing's sarcomas/primitive neuroectodermal tumors, 13 alveolar rhabdomyosarcomas, and 9 embryonal rhabdomyosarcomas. One desmoplastic small round cell tumor was found to have a variant EWS-WT1 chimeric product that included exon 8 of EWS EWS-FLI-1 chimeric RNA was present in all Ewing's sarcoma/primitive neuroectodermal tumor and not identified in any other tumor types, including desmoplastic small round cell tumor. PAX3/PAX7-FKHR chimeras were present in 9 of 13 alveolar rhabdomyosarcomas but not in any other tumors. Detection of chimeric transcripts by reverse transcriptase polymerase chain reaction is a very specific aid in differential diagnosis of developmental tumors and further establishes desmoplastic small round cell tumor as a distinct entity.
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PMID:Detection of chimeric transcripts in desmoplastic small round cell tumor and related developmental tumors by reverse transcriptase polymerase chain reaction. A specific diagnostic assay. 749 83

The WT 1 gene has been isolated as a tumor suppressor gene of Wilms' tumor. Using reverse transcriptase-polymerase chain reaction (RT-PCR), relative levels of the WT 1 gene expression was examined in 87 patients with acute leukemia, 25 with chronic myelogenous leukemia (CML), and 24 with non-Hodgkin's lymphoma (NHL). Significant levels of the WT 1 gene were expressed in all leukemia patients, and for CML the levels increased as the clinical phase progressed. No point mutations were found in the WT 1 gene when samples from 15 acute leukemia patients were subjected to PCR single-strand conformation polymorphism analysis. In striking contrast to acute leukemia, the levels of WT1 gene expression for NHL were significantly low or even undetectable. The levels of WT 1 gene expression inversely correlated with the prognosis of acute leukemia. The quantification of the WT 1 gene expression made it possible to detect minimal residual disease (MRD) in acute leukemia regardless of the presence of absence of tumor-specific DNA markers. Simultaneous monitoring of MRD by RT-PCR using primers for specific DNA markers in four patients (two AML-M3 with PML/RAR-alpha, one AML-M2 with AML1/ETO, and one CML with bcr/abl) detected MRD comparable to that obtained from quantitation of WT 1 gene expression. In a patient with acute promyelocytic leukemia, the limits of leukemic cell detection by RT-PCR using either WT 1 or PML/RAR-alpha gene primers were 10(-3)-10(-4) and 10(-4) for bone marrow, and 10(-5) and 10(-4) for peripheral blood, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[WT 1 and leukemia]. 764 50

The desmoplastic small round cell tumor (DSRCT) is a recently recognized type of primitive sarcoma defined by a predilection for young males, aggressive clinical behavior, widespread abdominal serosal involvement, and a primitive histological appearance with prominent desmoplasia and striking divergent, multilineage differentiation. Previous cytogenetic case reports have identified a recurrent translocation, t(11;22) (p13;q12). We have characterized this translocation at the molecular level in a panel of five DSRCTs using a candidate gene approach. Southern blot analysis revealed recurrent rearrangement of both EWS, located at 22q12, and rearranged in other tumor-specific translocations in Ewing's sarcoma and clear cell sarcoma, and of WT1, the gene at 11p13 involved in a subset of Wilms' tumor. Consistent comigration of the rearranged EWS and WT1 bands in multiple enzyme digests indicated fusion of the genomic sequences, presumably due to the translocation t(11;22) (p13;q12). Northern blotting showed aberrant EWS and WT1 transcripts of the same size, suggesting the presence of a chimeric messenger RNA. This was confirmed by reverse transcriptase polymerase chain reaction using an EWS exon 7 primer and WT1 exon 8 or 9 primers, which revealed single polymerase chain reaction products consistent with a junction of EWS exon 7 to WT1 exon 8. DSRCT thus represents the third primitive sarcoma in which the EWS gene is involved and the first instance of recurrent rearrangement of a tumor suppressor gene, WT1, in a specific tumor type. The different translocation partners of the EWS gene, all of which are putative or definite transcription factor genes, may be responsible for the biological differences between DSRCT, Ewing's sarcoma, and clear cell sarcoma.
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PMID:Fusion of the EWS and WT1 genes in the desmoplastic small round cell tumor. 818 63

We report two cases of intra-abdominal desmoplastic small round cell tumor with characteristic clinical, histological, immunohistochemical, and ultrastructural features. Fusion of the EWS gene on chromosome 22 and the WT1 gene on chromosome 11, resulting from the chromosomal translocation t(11;22)(p13;q12), was detected by reverse transcriptase polymerase chain reaction (RT-PCR) in both cases. This translocation has been previously reported in this type of tumor using either cytogenetic or molecular biological techniques. Tumor tissue from both cases revealed no chimeric fusion transcripts characteristic of the Ewing sarcoma family of peripheral primitive neuroectodermal tumors or of alveolar rhabdomyosarcoma, two tumors in the differential diagnosis of intra-abdominal desmoplastic small round cell tumor. This report demonstrates the utility of molecular studies as an adjunct in the diagnosis of this rare and aggressive tumor.
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PMID:Detection of the EWS/WT1 gene fusion by reverse transcriptase-polymerase chain reaction in the diagnosis of intra-abdominal desmoplastic small round cell tumor. 860 6

Using a reverse transcriptase polymerase chain reaction to examine alternate splicing at site I (exon 5) and site II (exon 9) in the Wilms' tumour suppressor gene, WT1, we found that in seven of the 10 Wilms' tumours examined, splicing at site I was disrupted. This is predicted to result in isoform imbalance in Wilms' tumours, with an increase in isoforms in which the 17 amino acids encoded by exon 5 are missing. These observations could not be explained by mutations or rearrangements in flanking introns. Disrupted alternate splicing of exon 5 may play a role in the aetiology of Wilms' tumour.
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PMID:Splicing of exon 5 in the WT1 gene is disrupted in Wilms' tumour. 865 31

Thirty-one patients (27 with acute myeloid leukemia [AML], 2 with acute lymphocytic leukemia [ALL], and 2 with acute mixed lineage leukemia [AMLL]) treated with conventional chemotherapy (CHT) and 23 patients (13 AML, 5 ALL, and 5 with chronic myeloid leukemia [CML]) treated with allogeneic bone marrow transplantation (BMT) were monitored for WT1 expression levels in BM and peripheral blood (PB) by reverse transcriptase-polymerase chain reaction over a long-term period (mean, 29 months for CHT and 24 months for BMT). Sixteen of the patients in the CHT group and 3 in the BMT group who had achieved complete remission suffered clinical relapse. In 10 of these patients, WT1 expression that had returned to normal BM levels (< 10(-3); the WT1 expression level of K562 cells was defined as 1.0) after complete remission (CR) either gradually or rapidly increased again to abnormal levels 1 to 18 months (mean, 7 months) before clinical relapse became apparent. In another 9 patients, WT1 expression never returned to normal BM levels even after CR and the subsequent relapse was accompanied by a rapid increase in WT1 expression to levels higher than 10(-2) (10(-3) levels in PB). On the other hand, the remaining 35 patients (15 CHT and 20 BMT) maintained their CR. In 29 of these patients (11 CHT and 18 BMT), WT1 expression either gradually or rapidly decreased to normal BM levels, whereas in the other 6 (4 CHT and 2 BMT), low or very low levels of WT1 mRNAs (10(-3) to 10(-2) in BM and 10(-5) to 10(-3) in PB) remain detectable, but without any clinical signs of relapse. A clear correlation was found to exist between the minimal residual disease (MRD) detected in the paired BM and PB samples for all types of leukemias (AML, ALL, and CML), with MRD in PB being approximately one-tenth of that in BM. WT1 quantitation of 168 paired BM and PB samples showed that PB samples were superior to BM samples for the detection of MRD. We conclude that monitoring of WT1 expression levels in BM and PB makes it possible to rapidly assess the effectiveness of individual treatment and diagnose clinical relapse in the early stage for all leukemia patients regardless of the presence or absence of tumor-specific DNA markers.
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PMID:Long-term follow-up of minimal residual disease in leukemia patients by monitoring WT1 (Wilms tumor gene) expression levels. 882 48

To clarify whether the expression of the WT1 gene in leukemic cells is aberrant or merely reflects that in normal counterparts, the expression levels of the WT1 gene were quantitated for normal hematopoietic progenitor cells. Bone marrow (BM) and umbilical cord blood (CB) cells were fluorescence-activated cell sorting (FACS)-sorted into CD34+ and CD34- cell populations, and the CD34+ cells into nine subsets (CD34+ CD33-, CD34+ CD33+, CD34+ CD38-, CD34+ CD38+, CD34+ HLA-DR-, CD34+ HLA-DR+, CD34+ c-kit(high), CD34+ c-kit(low), and CD34+ c-kit-) according to the expression levels of CD34, CD33, CD38, HLA-DR, and c-kit. Moreover, acute myeloid leukemic cells were also FACS-sorted into four populations (CD34+ CD33-, CD34+ CD33+, CD34- CD33+, and CD34- CD33-). FACS-sorted normal hematopoietic progenitor and leukemic cells and FACS-unsorted leukemic cells were examined for the WT1 expression by quantitative reverse transcriptase-polymerase chain reaction. The WT1 expression in the CD34+ and CD34- cell populations and in the nine CD34+ subsets of BM and CB was at either very low (1.0 to 2.4 x 10(-2)) or undetectable (< 10(-2)) levels (the WT1 expression level of K562 cells was defined as 1.0), whereas the average levels of WT1 expression in FACS-sorted and -unsorted leukemic cells were 2.4 to 9.3 x 10(-1). Thus, the WT1 expression levels in normal hematopoietic progenitor cells were at least 10 times less than those in leukemic cells. Therefore, we could not find any normal counterparts of BM or CB that expressed the WT1 at levels comparable with those in leukemic cells. These results indicate an aberrant overexpression of the WT1 gene in leukemic cells and imply the involvement of this gene in human leukemogenesis.
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PMID:Aberrant overexpression of the Wilms tumor gene (WT1) in human leukemia. 902 64

The Wilms tumor suppressor gene (WT1) is mutated in a number of cases of Wilms' tumor as well as in mesothelioma and leukemia. It encodes a transcription factor derived from any one of four alternate transcripts. WT1 has a restricted pattern of expression within the body and within the hemopoietic system its expression is limited to primitive leukemias and a number of leukemic cell lines. Given the overexpression of WT1 in leukemias, we have addressed the question of whether this gene is expressed within the normal hemopoietic system. Mononuclear bone marrow (BM) cells obtained from normal donors were separated by fluorescence-activated cell sorting (FACS) into "primitive" (CD34+) and "mature" (CD34-) cell populations. Total RNA extracted from these cells was subjected to reverse transcriptase polymerase chain reaction (RT-PCR) using primers based on the WT1 sequence, to examine the expression of this gene within the hemopoietic system. Phenotypic purity of cells was guaranteed by performing single-cell sorting followed by RT-PCR to define the precise cellular phenotypes that express WT1. Expression of WT1 was detected in cells bearing the CD34+ phenotype but not in those cells lacking expression of CD34. In addition, single-cell analysis revealed that expression of WT1 occurred in the candidate stem cell-containing population of hemopoietic cells which have the phenotype CD34+ CD38-. Moreover, the single-cell RT-PCR analysis also demonstrated that differential expression of alternate transcripts of WT1 occurs between hemopoietic progenitor cells with the same phenotype. In conclusion, expression of WT1 is limited to early progenitors of the blood system, which suggests that this gene plays a critical role in hemopoietic development.
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PMID:Expression of the Wilms' tumor gene (WT1) in normal hemopoiesis. 940 89

We previously demonstrated maternal monoallelic expression of the Wilms tumor suppressor gene, WT1, in about half of pre-term placental villus and fetal brain tissues examined. There were two alternative explanations for this pattern of the WT1 expression, i.e., an imprinting polymorphism vs. a developmental stage-dependent switching from monoallelic to biallelic expression of the gene. To investigate these possibilities, we examined WT1 expression in a larger number of villus samples (46 samples) with gestational ages ranging from 4 to 21 weeks, using reverse transcriptase-based polymerase chain reaction (RT-PCR) to amplify the sequences for polymorphic sites in the 3'-untranslated region (UTR) of WT1. Maternal monoallelic expression was observed in 7 (39%) of 18 samples informative for the polymorphism, while the expression of the remaining 11 samples was biallelic. In addition, there was no correlation between expression patterns and gestational ages of the samples. The results indicate that the pattern of expression (monoallelic vs. biallelic) is polymorphic. The expression patterns were also studied in five different organs from a 21-week-old fetus, showing monoallelic expression only in the placenta and biallelic expression in other organs (heart, lung, liver and intestine). The finding supports the tissue specificity of the WT1 monoallelic expression.
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PMID:Polymorphic and tissue-specific imprinting of the human Wilms tumor gene, WT1. 918

WT1 (Wilms tumor gene) expression is a new tumor marker of leukemic blast cells of AML, ALL, and CML. Minimal residual disease (MRD) of leukemia can be detected at frequencies as low as 1 in 10(3) to 10(4) normal bone marrow (BM) cells and 1 in 10(5) normal peripheral blood (PB) cells by means of the quantitation of expression levels of the WT1 gene using reverse transcriptase-polymerase chain reaction (RT-PCR). This is regardless of the types of leukemia or the presence or absence of tumor-specific DNA markers. Thus, the WT1 assay makes it possible to rapidly assess the effectiveness of treatment and to evaluate the degree of eradication of leukemic cells in individual leukemia patients. Moreover, molecular relapse using PCR can be diagnosed by the monitoring of WT1 expression levels in BM or PB 1-24 months (means, 7 months for BM and 8 months for PB) before the clinical relapse became apparent. In case of rapid or gradual increase in WT1 expression levels to or over 10(-2) after return to normal BM levels during CR; or retention of the WTI expression at levels near or over 10(-2) in BM without return to normal BM levels even in CR (WT1 expression level in K562 cells was defined as 1.0), it seems that clinical relapse is impending. Since WT1 antisense oligomers inhibit the growth of leukemic cells, it is apparent that the WT1 gene plays an important role in leukemogenesis.
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PMID:Wilms tumor gene (WT1) as a new marker for the detection of minimal residual disease in leukemia. 966 76


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