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)

Detection of characteristic chromosomal translocations has aided diagnosis of the small round cell tumors of childhood and may help to stratify patients into clinical groups. The detection of the abnormalities by classical cytogenetic techniques has been supplemented by fluorescent in situ hybridization and reverse transcriptase polymerase chain reaction (RT-PCR). These techniques allow diagnoses to be made using only very small amounts of tumor tissue. We here describe a technique for the rapid and specific detection by modified reverse transcriptase polymerase chain reaction of characteristic chromosomal translocations of alveolar rhabdomyosarcoma with small amounts of formalin-fixed tissue as the starting material. Of 27 samples studied, 4 cases are described in which the detection of translocations by this method cast doubt on the original histopathological diagnosis. These cases demonstrate the critical diagnostic importance of the detection of these translocations in rhabdomyosarcoma.
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PMID:Amplification of the t(2; 13) and t(1; 13) translocations of alveolar rhabdomyosarcoma in small formalin-fixed biopsies using a modified reverse transcriptase polymerase chain reaction. 903 64

Alveolar rhabdomyosarcoma is a pediatric soft-tissue tumor that is often difficult to distinguish from other small round-cell tumors. The PAX3-FKHR and PAX7-FKHR gene fusions that result from chromosomal translocations in this tumor provide potential molecular diagnostic markers. To apply these molecular markers to commonly available archival material, we used reverse transcriptase-polymerase chain reaction and oligonucleotide hybridization methodology to develop an assay capable of identifying PAX3-FKHR and PAX7-FKHR fusion transcripts in formalin-fixed, paraffin-embedded tissue. Use of a control assay for wild-type FKHR mRNA indicated that RNA was successfully isolated, reverse-transcribed, and amplified in 15 of 16 archival cases. Comparison of assay results for the PAX3-FKHR and PAX7-FKHR fusions with standard molecular assays of paired frozen material revealed that all eight cases of known fusion-positive rhabdomyosarcoma were correctly identified and distinguished as PAX3-FKHR or PAX7-FKHR. The seven cases of known fusion-negative rhabdomyosarcoma showed no evidence of either product. These results indicate that we have developed a molecular assay that accurately identifies the fusion transcripts characteristic of alveolar rhabdomyosarcoma in archival samples. This assay will be useful for diagnosis and for retrospective clinicopathologic correlative studies.
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PMID:Detection of gene fusions in rhabdomyosarcoma by reverse transcriptase-polymerase chain reaction assay of archival samples. 909 47

We report a case of a 13-year-old girl with soft tissue sarcoma of the hand, which showed muscle and neuroectodermal immunophenotypes. Molecular studies were performed on RNA collected from fine-needle aspiration (FNA) cytology and peripheral blood samples by nested reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern blot analysis. This biphenotypic tumor showed simultaneous expression of EWS-FLI1 and PAX3-FKHR transcripts, specific of Ewing family tumors and alveolar rhabdomyosarcoma, respectively. Although childhood sarcomas with simultaneous muscle and neural differentiation have been described to have EWS-FLI1 transcripts, there are no reports of tumors with both transcripts. Cytological specimens are a good source of RNA for molecular studies.
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PMID:Molecular features in a biphenotypic small cell sarcoma with neuroectodermal and muscle differentiation. 949 Feb 79

PAX3, a member of the PAX-gene family, encodes a nuclear transcription factor that is transiently expressed in the neural tube and in muscle progenitor cells and regulates embryonal development in the mouse. Together with the FKHR gene it is involved in the t(2;13)(q35;q14), a specific translocation associated with alveolar rhabdomyosarcoma (ARMS). As a consequence of the rearrangement two chimeric transcripts originate: FKHR-PAX3 and PAX3-FKHR. We studied the expression of wild type PAX3 and the chimeric transcripts originating from the t(2;13) in a series of 23 rhabdomyosarcomas (RMS) of childhood, by reverse transcriptase polymerase chain reaction (RT-PCR). Wild type PAX3 was detected in 48% of the RMS, whereas another 39% were positive only after nested PCR. Normal adult-skeletal muscle showed a very weak expression of PAX3, but fetal muscle did not express PAX3. PAX3-FKHR was found in 11 of 15 alveolar RMS, 7 of which were positive also for the reciprocal transcript, whereas no RMS expressed FKHR-PAX3 alone. These results confirm that the PAX3-FKHR transcript is specifically associated with the alveolar RMS and that it is a more sensitive marker of the t(2;13) than the reciprocal product FKHR-PAX3. Furthermore, the finding of PAX3 expression with or without PAX3-FKHR transcript in the great majority of the cases raises the question of whether PAX3 expression could play a role in the pathogenesis of RMS.
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PMID:Normal and rearranged PAX3 expression in human rhabdomyosarcoma. 954 61

We reviewed six cases of rhabdomyosarcoma as a rare second primary malignancy in children with bilateral retinoblastoma after irradiation treatment. The patients comprised four females and two males (age range 1 year 4 months-7 years 11 months). Second tumors arose in the temporal muscle inside or close to the previously irradiated fields. All the children were alive and well 24-72 months after diagnosis. Microscopic examination showed proliferation of closely packed, small round cells with scanty cytoplasm, coarse nuclear chromatin, and increased mitotic activity without a myxoid background nor obvious alveolar architecture. The most characteristic feature was the presence of rosette-like structures in four tumors. Immunoreactivity for many skeletal muscle markers was evident, including desmin (six of six), muscle-specific actin (HHF35) (six of six), sarcomeric actin (six of six), myogenin (six of six), vimentin (six of six), and myoglobin (three of six). On reverse transcriptase-polymerase chain reaction examination, three second tumors lacked specific chimeric transcripts for alveolar rhabdomyosarcoma and Ewing's sarcoma. Unexpectedly, variable reactivity for neurofilament (150 kd) was identified in six of six second tumors as well as 15 of 20 sporadic primary rhabdomyosarcomas (75%) examined as controls, the result being confirmed by Western blot analysis. In addition, staining for retinoblastoma-susceptibility gene protein was negative in all second tumors, in contrast to positivity in 14 of 17 sporadic primary tumors (82%). This finding suggests that retinoblastoma-susceptibility gene abnormalities could be associated with the development of second primary rhabdomyosarcoma. We consider that knowledge of the occurrence of rhabdomyosarcoma and appropriate immunohistochemical study are helpful for avoiding a misdiagnosis of recurrent retinoblastoma or Ewing's sarcoma when encountering patients with a history of bilateral retinoblastoma who developed second small round cell neoplasms.
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PMID:Second primary rhabdomyosarcomas in patients with bilateral retinoblastoma: a clinicopathologic and immunohistochemical study. 980 27

Rhabdomyosarcomas are a heterogeneous group of tumors with respect to their molecular basis, degree of differentiation, histology, and clinical behavior. Because of the wide variation of tumor morphology, it is often difficult to distinguish between the distinct subtypes of rhabdomyosarcomas. By using cryosections of tumor specimens and immunohistochemistry, in the present study we show that strong expression of myogenin in rhabdomyosarcoma is associated with alveolar histology (P = <0.0001, Fisher's exact test). Although staining for myogenin was observed in 22 of 26 rhabdomyosarcomas, all alveolar rhabdomyosarcomas (nine of nine) showed high levels of staining for myogenin, as defined by the frequency and intensity of staining of the tumor cells. The staining pattern suggests that the tumor cells are clonally derived from myogenin-positive progenitor cells. In contrast, most embryonal rhabdomyosarcomas (13 of 15) were either negative or showed a low level of staining for myogenin. In these tumors a larger proportion of tumor cells were distinctly negative for myogenin. Six of seven alveolar rhabdomyosarcomas that strongly stained for myogenin were also positive for Pax3-7/Forkhead (FKHR) by polymerase chain reaction/reverse transcriptase-polymerase chain reaction. One of two embryonal rhabdomyosarcomas that strongly stained for myogenin was retrospectively found to be positive for Pax3/FKHR transcripts. Quantitative analysis for myogenin by Western blotting using a smaller subset of rhabdomyosarcomas revealed that in general there was a good correlation between immunohistochemical staining and Western blotting (P = 0.01, Pearson Correlation), although the former technique was more sensitive for detecting tumors with low levels of the protein. On average, alveolar rhabdomyosarcomas expressed at least threefold more myogenin than embryonal rhabdomyosarcomas. Our data show that staining for myogenin will be a simple, rapid, and accurate adjunct for distinguishing between alveolar and embryonal rhabdomyosarcomas. We propose that embryonal rhabdomyosarcomas result from an early block in myogenesis, before the expression of myogenin. In contrast, we propose that alveolar rhabdomyosarcomas either originate from a late block in myogenesis (after expression of myogenin) or that the pathological mechanisms involved in these neoplasms also induce strong expression of this protein.
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PMID:Strong immunostaining for myogenin in rhabdomyosarcoma is significantly associated with tumors of the alveolar subclass. 1066 68

Rhabdomyosarcoma may be divided into three subtypes--embryonal, alveolar, and undifferentiated sarcoma--which can be distinguished by molecular analysis. The authors applied reverse transcriptase-polymerase chain reaction analysis (RT-PCR) to analyze tumor samples from 14 children with rhabdomyosarcoma for the presence of the chimeric PAX3-FKHR transcript resulting from the translocation t(2;13)(q35,q14). Both fresh and paraffin-embedded tissues were used. In only nine specimens was the RNA intact for the analysis. The chimeric transcript was identified in seven samples: four alveolar type, one embryonal type, and two undifferentiated sarcoma. Histologic review was performed in the three samples with discordance between the molecular and histologic findings. A sample from a patient with a diagnosis of embryonal rhabdomyosarcoma on presentation and expression of PAX3-FKHR fusion transcript yielded a small focus of alveolar rhabdomyosarcoma and was reclassified as alveolar rhabdomyosarcoma. One of the samples from a patient with undifferentiated sarcoma was redefined as alveolar subtype; the diagnosis of the second undifferentiated sarcoma remained unchanged, in accordance with the histologic diagnosis. These findings further support the recommendation that molecular analysis be included in the diagnostic workup of childhood small round cell tumors to reach a more accurate diagnosis for tailoring of specific treatment.
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PMID:Clinical relevance of molecular diagnosis in childhood rhabdomyosarcoma. 1071 7

Alveolar rhabdomyosarcoma (ARMS) is associated with the specific chromosomal translocation (2;13)(q35;q14) or its rarer variant t(1;13)(p36;q14), which produces the fusion gene PAX7-FKHR. Here we describe the human cell line RC2, derived from an ARMS, which harbors a cryptic t(1;13)(p36;q14) and concomitantly shows amplification of the PAX7-FKHR fusion gene and of the MYCN oncogene. The t(1;13) and MYCN oncogene were studied by standard cytogenetic analysis and molecular techniques. The reverse transcriptase polymerase chain reaction demonstrated the expression of PAX7-FKHR mRNA in RC2 cells, although karyotype analysis failed to demonstrate a t(1;13)(p36;q14) chromosomal translocation or a derivative 13 chromosome. Double minute chromosomes were detected in all the metaphases studied. Fluorescence in situ hybridization analysis revealed multiple copies of the PAX7-FKHR fusion gene localized exclusively on a subset of double minutes, whereas multiple copies of MYCN were identified on other double minute chromosomes. Southern-blot analysis demonstrated that RC2 cells contain approximately 20 copies of the MYCN oncogene. So far no continuous RMS cell line carrying the t(1;13)(p36;q14) has been described, and PAX7-FKHR and MYCN amplifications have always been reported to occur separately in rhabdomyosarcoma (RMS). The availability of an ARMS cell line that harbors the t(1;13)(p36;q14) constitutes a useful tool for further understanding the role of the PAX7-FKHR fusion gene in RMS oncogenesis and may improve knowledge of the possible relation between PAX7-FKHR and MYCN amplification.
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PMID:Concomitant amplification and expression of PAX7-FKHR and MYCN in a human rhabdomyosarcoma cell line carrying a cryptic t(1;13)(p36;q14). 1106 97

Previous findings of low levels of reverse transcriptase (RT) activity in chick cell-derived measles and mumps vaccines showed this activity to be associated with virus particles containing RNA of both subgroup E endogenous avian leukosis viruses (ALV-E) and endogenous avian viruses (EAV). These particles originate from chicken embryonic fibroblast (CEF) substrates used for propagating vaccine strains. To better characterize vaccine-associated ALV-E, we examined the endogenous ALV proviruses (ev loci) present in a White Leghorn CEF substrate pool by restriction fragment length polymorphism. Five ev loci were detected, ev-1, ev-3, ev-6, ev-18, andev-19. Both ev-18 and ev-19 can express infectious ALV-E, while ev-1, ev-3, and ev-6 are defective. We analyzed the full-length sequence of ev-1 and identified an adenosine insertion within the pol RT-beta region at position 5026, which results in a truncated RT-beta and integrase. We defined the 1,692-bp deletion in the gag-pol region of ev-3, and we found that in ev-6, sequences from the 5' long terminal repeat to the 5' pol region were absent. Based on the sequences of the ev loci, RT-PCR assays were developed to examine expression of ALV-E particles (EV) in CEF supernatants. Both ev-1- and ev-3-like RNA sequences were identified, as well as two other RNA sequences with intact pol regions, presumably of ev-18 and ev-19 origin. Inoculation of susceptible quail fibroblasts with CEF culture supernatants from both 5-azacytidine-induced and noninduced CEF led to ALV infection, confirming the presence of infectious ALV-E. Our data demonstrate that both defective and nondefective ev loci can be present in CEF vaccine substrates and suggest that both ev classes may contribute to the ALV present in vaccines.
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PMID:Characterization of endogenous avian leukosis viruses in chicken embryonic fibroblast substrates used in production of measles and mumps vaccines. 1126 50

The reverse transcriptase polymerase chain reaction (RT-PCR) provides a technique to diagnose a group of sarcomas and small round cell tumors that contain specific chromosomal translocations and chimeric gene fusion products. We adapted real-time qualitative RT-PCR to utilize dual-labeled, fluorogenic, TaqMan probes, which hybridize to targets that overlap the junction of the chimeric gene fusions in alveolar rhabdomyosarcoma (ARMS), synovial sarcoma (SS), and desmoplastic small round cell tumor (DSRCT). Assays were confirmed on cell lines and tissue samples; appropriate negative amplification assays were obtained when each tumor-specific probe and primer set was used on different neoplasms and cell lines that were not expected to harbor the specific translocations and chimeric gene fusions. Although our cases are few, we speculate that as more molecular variants of ARMS, SS, and DSRCT are discovered, clinical correlations based on precise molecular features will be required and fusion site specificity will be assured by the use of junction-based TaqMan probes.
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PMID:TaqMan junction probes and the reverse transcriptase polymerase chain reaction: detection of alveolar rhabdomyosarcoma, synovial sarcoma, and desmoplastic small round cell tumor. 1217 83


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