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)

One of the diagnostic criteria of essential thrombocythemia (ET) is the absence of the Philadelphia chromosome (Ph-neg). On the molecular level, Ph-neg ET patients may carry BCR-ABL transcript. The natural history of BCR-ABL positive Ph-neg ET patients is undetermined. We examined the BCR-ABL status by reverse transcriptase two-step nested polymerase chain reaction in bone marrow aspirates of 25 Ph-neg ET patients. We found 12 BCR-ABL positive and 13 BCR-ABL negative patients in the study group. The comparison showed that the two groups had similar clinical and laboratory characteristics, except for a significant increased patients' age and decreased polymorphonuclear cell count in the BCR-ABL positive group. During a median follow-up of 20 and 22.5 months for the BCR-ABL negative and positive groups, respectively, there was neither blastic transformation nor unrelated death in both groups. We conclude that it is important to look for BCR-ABL transcript in Ph-neg ET patients and to follow them closely to investigate the nature of this translocation in this group of patients.
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PMID:BCR-ABL transcripts in bone marrow aspirates of Philadelphia-negative essential thrombocytopenia patients: clinical presentation. 1156 40

We present the case of a two-year-old child with an atypical presentation of chronic myeloid leukemia. At diagnosis, he showed clinical and biological features of juvenile chronic myeloid leukemia (CML). However, eosinophilia was observed in blood and bone marrow. The bone marrow karyotype did not demonstrate the Philadelphia chromosome but BCR-ABL rearrangement was shown to be present by reverse transcriptase polymerase chain reaction (RT-PCR) analysis and confirmed by fluorescent in situ hybridization (FISH) analysis. Discussion centres on the differentiation between juvenile CML and childhood chronic myelogenous Leukemia and the importance of carrying out RT PCR for all juvenile CML cases.
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PMID:Philadelphia negative BCR-ABL positive chronic myeloid leukemia mimicking juvenile chronic myeloid leukemia in a 2-year-old child. 938 69

Approximately 5% of patients with chronic myelogenous leukemia (CML) do not reveal the Philadelphia (Ph) chromosome cytogenetically and are termed Ph-negative CML cases. We report one such case, which appeared normal by routine banding techniques. The BCR/ABL rearrangement was detected by reverse transcriptase-polymerase chain reaction and Southern blotting analysis, which suggested a b3-a2 splice junction. Dual color fluorescence in situ hybridization (FISH) with BCR and ABL DNA probes showed that the chimeric fusion gene was localized on chromosome 9q34, rather than at the typical location on chromosome 22q11. The BCR/ABL rearrangement was detected in 75% of the patient's bone-marrow population, whereas the remaining 25% of the cells appeared normal. The use of dual color FISH in the diagnosis of CML is extremely valuable not only in identifying cases of Ph-negative CML, but also in quantifying the proportion of transformed cell populations. This information ultimately results in an enhancement of our ability to monitor therapy, follow disease progression, and determine transplant eligibility.
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PMID:A Philadelphia negative chronic myelogenous leukemia with the chimeric BCR/ABL gene on chromosome 9 and a b3-a2 splice junction. 949 17

There is a need for fast and sensitive methods to evaluate the response of patients with chronic myeloid leukaemia (CML) to interferon-alpha (IFN-alpha) therapy to complement cytogenetic analysis of Philadelphia (Ph) chromosome-positive metaphases. We have used interphase FISH (fluorescence in situ hybridization) and competitive RT-PCR (reverse transcriptase-polymerase chain reaction) techniques for detection of BCR-ABL-positive cells to measure suppression of leukaemic clone in a series of 51 follow-up samples from 24 CML patients undergoing IFN-alpha treatment. Interphase FISH analysis of the malignant clone in bone marrow using BCR and ABL probes was found to be highly correlated to conventional G-banding metaphase examination (r = 0.98). RT-PCR quantification of BCR-ABL mRNA transcripts in blood also showed a high degree of concordance with the proportion of Ph-positive metaphases (r = 0.93). In addition, the degree of cytogenetic response did not influence the equivalence between karyotype analysis and molecular methods. We concluded that interphase FISH and competitive RT-PCR provide reliable information on residual tumour burden and response to IFN-alpha in CML patients. These molecular methods may significantly improve the efficiency of residual disease monitoring during IFN-alpha therapy of CML.
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PMID:Interphase cytogenetics and competitive RT-PCR for residual disease monitoring in patients with chronic myeloid leukaemia during interferon-alpha therapy. 963 1

Approximately 2-5% of children with newly diagnosed acute lymphoblastic leukemia (ALL) have a Philadelphia (Ph) chromosome detectable on cytogenetic analysis, which is associated with a poor prognosis. In rare ALL cases the Ph chromosome may appear in leukemic cells during the course of the disease. We report here the case of a 5.5-year-old male patient with T-ALL who was found to have the b2a2 BCR-ABL mRNA transcript by reverse transcriptase-polymerase chain reaction (RT-PCR) at first marrow relapse. At the time of initial diagnosis, no BCR-ABL transcripts had been detected by PCR in the patient's blood and marrow samples. Further studies were performed using a competitive PCR titration assay and the fluorescence in situ hybridization (FISH) method to monitor the leukemic clone. Progression of the disease was associated with a higher BCR-ABL transcript level and an increasing proportion of BCR-ABL-positive cells. Metaphase FISH analysis identified the presence of the BCR-ABL fusion gene on a normal chromosome 22. This study shows that a late-appearing Ph translocation in ALL may be cytogenetically invisible. Quantitative RT-PCR and FISH techniques are appropriate and efficient methods for detecting these rare ALL variants expressing the BCR-ABL fusion gene and for estimating the level of residual disease following treatment.
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PMID:Molecular detection of a late-appearing BCR-ABL gene in a child with T-cell acute lymphoblastic leukemia. 976 Jan 54

The number of genetic lesions necessary to generate leukemia in humans is unknown, but it is possible that certain specific abnormalities, eg, fusion genes, known to be associated with acute and chronic leukemia are produced relatively frequently in human cells but require other events to occur before the leukemia becomes manifest. We investigated this possibility by studying peripheral blood leukocytes from normal individuals and various hematopoietic cell lines for the presence and expression of the p210 and the p190 types of the BCR-ABL gene associated with chronic myeloid leukemia (CML) and acute lymphoblastic leukemia. We used two-step reverse transcriptase-polymerase chain reaction (RT-PCR) assays in which batches of 10(8) cells per sample were tested in 40 replicate reactions. We estimate that this assay is 1.5 logs more sensitive than the two-step RT-PCR assays that we use routinely to assess minimal residual disease. BCR-ABL fusion gene transcripts of various configurations were found in circulating leukocytes from 12 of the 16 healthy adults analyzed. Transcripts with an e1a2 junction (p190 BCR-ABL) were present in 11 and p210-type transcripts with b2a2 and/or b3a2 junctions were detected in 4 individuals. The same RT-PCR assays in non-CML cell lines showed the presence of classical or aberrant p210-type mRNA in 3 of 7 lines and of p190-type transcripts in all 7 lines of hematopoietic origin (HL60, KG1, U937, Kasumi, Jurkat, JVM13, and JVM25), whereas the NIH3T3 murine fibroblast line was reproducibly negative for these fusion genes. These findings confirm and extend previous reports on the detection of leukemia-associated genes in normal leukocytes and suggest that certain fusion genes are generated relatively frequently in hematopoietic cells, but only infrequently do the cells acquire the additional changes necessary to produce leukemia in humans. Although there is only a small probability that such innocent BCR-ABL-carrying leukocytes are detected by conventional RT-PCR assays, they may be the source of some sporadically positive tests in leukemia patients in long-term remission.
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PMID:The presence of typical and atypical BCR-ABL fusion genes in leukocytes of normal individuals: biologic significance and implications for the assessment of minimal residual disease. 978 74

Modern therapy for pediatric acute lymphoblastic leukemia (ALL) is based on the principle of risk stratification. One of the most important laboratory features used to accurately risk stratify patients is the presence of specific chromosomal translocation within the leukemic blasts. In this paper, we describe a multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) assay for the accurate, sensitive, and rapid identification of chimeric transcripts encoded by the major risk-stratifying translocations of pediatric ALL. This assay will identify both the CML- and ALL-type BCR-ABL transcripts encoded by the t(9;22), all described variants of the E2A-PBX1 transcripts encoded by the t(1;19), the MLL-AF4 transcripts encoded by the t(4;11), and all variants of TEL-AML1 encoded by the t(12;21). In addition, we have developed a reverse dot-blot detection system as an alternative to traditional post-PCR Southern blot analysis. Application of this combined assay to the analysis of 70 leukemic samples and five cell lines resulted in a complete concordance between this multiplex assay and individual PCR reactions. The characteristics of the multiplex assay suggest that its application to routine clinical screening will significantly improve the ability of clinical laboratories to accurate risk stratify pediatric ALL patients.
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PMID:A multiplex RT-PCR assay for the detection of chimeric transcripts encoded by the risk-stratifying translocations of pediatric acute lymphoblastic leukemia. 984 30

We report a case of chronic neutrophilic leukemia (CNL) in a 68-year-old man. Karyotype showed a clonal abnormality, never described before in CNL: 46,XY,del(11)(q23). Southern blot analysis of the MLL gene did not reveal any rearrangement, and reverse transcriptase polymerase chain reaction (RT-PCR) analysis did not show any fusion of BCR-ABL. Treatment with hydroxyurea and cytosine arabisonide was ineffective.
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PMID:A case of chronic neutrophilic leukemia with deletion (11)(q23). 1019 27

Methods of minimal residual disease (MRD) detection in chronic myelogenous leukemia (CML) include chromosome analysis, reverse transcriptase polymerase chain reaction (RT-PCR) and fluorescence in situ hybridization (FISH) techniques. We report a novel method to detect intracellular BCR-ABL messenger on single cells using in situ RT-PCR, which can be performed on blood and marrow slides, without extraction of the nucleic acid. After cellular permeabilization and fixation, the mRNA BCR-ABL was reverse transcribed and amplified by PCR using digoxigenin-labelled dUTP. The reaction was revealed with the anti-digoxigenin FITC antibody. On the fluorescent microscope, a strong positive green fluorescence signal was observed in 98-99% cells in Ph1-positive cell lines. A faint signal was detected in 1.5% and 2% of negative cell lines. Likewise, a faint signal was found in 1.6-2.8% of the cells in five normal controls (mean 2.2 +/- 1.1%). The positive threshold for in situ RT-PCR was therefore determined as mean + 2 s.d. = 4.4% cells. We used in situ RT-PCR by comparison to cytogenetics (at least 30 mitoses examined), and two-step RT-PCR (10(-6) sensitivity in our hands) in bone marrow samples from 13 CML patients: two patients at diagnosis and 11 patients in hematological remission after alpha interferon (three patients), hydroxyurea (one patient) autologous bone marrow transplantation (BMT) (one patient) and allogeneic BMT (six patients). In the two diagnostic patients, 90 and 95% cells were respectively strongly positive by in situ RT-PCR. In the six patients treated by allogeneic BMT, the median percentage of positive cells was 2.4% (range 1.8-3.2). All six patients had normal karyotype and negative two-step RT-PCR results. In the five other patients, two were treated by hydroxyurea alone or autologous BMT, and 11 and 13% of the cells were strongly positive; three were treated with interferon and 14-62% of the cells were positive, generally weakly. All five patients had persistence of Ph1 (in 9-56% mitoses), and positive RT-PCR results after one round. In conclusion, in situ RT-PCR can specifically identify cells with BCR-ABL transcript and its results are concordant with those of karyotype and RT-PCR. Because of its limited sensitivity and specificity, however, it appears to have limited value in the analysis of MRD. On the other hand, it can evaluate the presence and intensity of BCR-ABL fusion transcript at the single cell level, and this could be useful in treatment monitoring.
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PMID:Detection of BCR-ABL transcripts in chronic myeloid leukemia (CML) using an in situ RT-PCR assay. 1037 89

Chronic myeloid leukemia (CML) is characterized by an increased proliferative activity of the leukemic progenitors that produce an elevated number of mature granulocytes. Nevertheless, cell cycle-active agents, even in very high doses, are alone unable to eradicate the leukemic clone, suggesting the presence of a rare subset of quiescent leukemic stem cells. To isolate such cells, we first used Hoechst 33342 and Pyronin Y staining to obtain viable G(0) and G(1)/S/G(2)/M fractions of CD34(+) cells by fluorescence-activated cell sorting (FACS) from 6 chronic-phase CML patients' samples and confirmed the quiescent and cycling status of the 2 fractions by demonstration of expected patterns of Ki-67 and D cyclin expression. Leukemic (Ph(+)/BCR-ABL(+)) cells with in vitro progenitor activity and capable of engrafting immunodeficient mice were identified in the directly isolated G(0) cells. Single-cell reverse transcriptase-polymerase chain reaction (RT-PCR) analysis showed that many leukemic CD34(+) G(0) cells also expressed BCR-ABL mRNA. CD34(+) from 8 CML patients were also labeled with carboxyfluorescein diacetate succinimidyl diester (CFSE) before being cultured (with and without added growth factors) to allow viable cells that had remained quiescent (ie, CFSE(+)) after 4 days to be retrieved by FACS. Leukemic progenitors were again detected in all quiescent populations isolated by this second strategy, including those exposed to a combination of flt3-ligand, Steel factor, interleukin-3, interleukin-6, and granulocyte colony-stimulating factor. These findings provide the first direct and definitive evidence of a deeply but reversibly quiescent subpopulation of leukemic cells in patients with CML with both in vitro and in vivo stem cell properties.
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PMID:Isolation of a highly quiescent subpopulation of primitive leukemic cells in chronic myeloid leukemia. 1047 35


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