Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Polymerase chain reaction (PCR) is a novel tool for the in vitro amplification of DNA segments up to several kb. Repeated cycles of DNA synthesis by heat-stable Taq DNA polymerase enables to obtain more than 10(5) copies of the target sequence. Recently its enormous attitude of amplification has been applied for the detection of tumor-specific gene alterations. Examples include the detection of point mutation of RAS oncogenes at codons 12, 13, and 61 and the detection of minimal residual neoplastic cells in patients in complete clinical remission. Among many kinds of tumor specific gene translocations, BCR-ABL gene in t(9;22)(q34;q11) and BCL-2-IgH gene in t(14:18)(q32;q21) have been successfully PCR-amplified around their fused regions. In lymphoid malignancies gene rearrangements of T cell receptor chain or immunoglobulin heavy chain can be used as clonal markers for leukemic cells. PCR technique permits the detection of leukemia DNA at dilution of 10(-4) to 10(-6). Although further investigation of patients' follow-up in large scale is needed, this technique seems to hold promise for the monitoring of residual neoplastic cells.
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PMID:[Polymerase chain reaction (PCR)--a novel tool for the molecular diagnosis of neoplasms]. 220 61

Chronic myelogenous leukemia (CML) is characterized by the Philadelphia chromosome resulting from the translocation t(9-22) producing the chimeric 190 and 210 kDa BCR-ABL fusion proteins. Evolution of the CML to the more agressive acute myelogenous leukemia (AML) is accompanied by increased cellular proliferation and genomic instability at the cytogenetic level. We hypothezised that genomic instability at the nucleotide level and spontaneous error in DNA replication may also contribute to the evolution of CML to AML. Murine Ba/F3 cell line was transfected with the p190 and p210-encoding BCR-ABL oncogenes, and spontaneous mutation frequency at the Na-K-ATPase and the hypoxanthine guanine phosphoribosyl transferase (HPRT) loci were measured. A significant 3-5-fold increase in mutation frequency for the transfected cells relative to the untransfected control cells was found. Furthermore, we observed that BCR-ABL transfection induced an overexpression of DNA polymerase beta, the most inaccurate of the mammalian DNA polymerases, as well as an increase in its activity, suggesting that inaccuracy of DNA replication may account for the observed mutator phenotype. These data suggest that the Philadelphia abnormality confers a mutator phenotype and may have implications for the potential role of DNA polymerase beta in this process.
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PMID:Mutator phenotype of BCR--ABL transfected Ba/F3 cell lines and its association with enhanced expression of DNA polymerase beta. 1034 41

Quantitative competitive RT-PCR techniques have been developed to detect BCR-ABL fusion transcripts in CML but they are hardly reproducible. In this work, we have developed BCR-ABL quantification by real time RT-PCR using the ABI PRISM 7700 (Perkin Elmer), a new technique which allows simple and rapid quantification of a target sequence during the extension phase of PCR amplifications. A fluorogenic probe labeled with both a reporter dye at the 5' end and a quencher-dye at the 3' end hybridizes to the target sequence on the third exon of the ABL gene. The exonuclease activity of the Taq DNA polymerase cleaves the probe and releases the reporter dye, resulting in an increase in the fluorescence signal. The absolute copy number of the target sequence (BCR-ABL) or a control gene (ABL) in an unknown sample can then be calculated using a calibration curve prepared from a set of BCR-ABL RNA standards, and results are expressed as a BCR-ABL/ABL ratio. In our hands, the sensitivity of a serial dilution of total RNA from a positive cell line (K562) in a negative cell line (HL60) was 10(-4). Fifteen CML patients in cytogenetic CR, including 11 allografted patients, two autografted patients and two patients treated by IFN were studied sequentially by this new real time quantitative RT-PCR technique in parallel with conventional qualitative two round nested RT-PCR. The two autografted patients showed high BCR-ABL/ABL ratio in all samples. The two patients treated by IFN showed a progressive decrease in the ratio. In the 11 allografted patients, four were sequentially studied 2 years or more after allo-BMT, and all ratios were below 10(-4). The four patients remained in clinical and cytogenetic CR. The seven other allografted patients were studied immediately after the procedure. Three of them showed a progressive decrease in the BCR-ABL/ABL ratio which reached 10(-4) 7 months after allo-BMT. The three patients remained in hematologic and cytogenetic CR. The remaining four allografted patients had progressive increase of BCR-ABL ratio; three developed cytogenetic relapse 9, 11, 28 months after allo-BMT, and the last patient remained in cytogenetic CR in the bone marrow but developed granulocytic sarcoma. Results of real-time quantitative RT-PCR were in agreement with those of qualitative two round nested PCR. However, evolution changes in the results of real-time quantitative RT-PCR often preceded those of the conventional technique: a decrease of the BCR-ABL/ABL ratio preceded progression from first round to second round positivity and then negativity with the classical technique; conversely, an increase in the ratio preceded evolution with the classical technique. Thus, real-time quantitative RT-PCR may show better correlation with clinical and cytogenetic evolution than conventional qualitative techniques and may help in making early therapeutic decisions in CML, especially after molecular relapse.
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PMID:Detection of BCR-ABL transcripts in chronic myeloid leukemia (CML) using a 'real time' quantitative RT-PCR assay. 1036 Mar 86