Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.3 (topoisomerase)
 9,911 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Many viral oncogenes encode protein-tyrosine kinase activities. However, important in vivo substrates of these enzymes have yet to be identified. Recently, type I topoisomerases were shown to be in vitro substrates for two tyrosine kinases. Following tyrosine phosphorylation, topoisomerase I activity was reduced 10-fold (Tse-Dinh et al. Nature 312: 785-786, 1984). To determine whether topoisomerase I activity was modulated by tyrosine phosphorylation in vivo, we have measured topoisomerase I activity in nuclear lysates prepared from both normal fibroblasts and cells transformed by two different viral oncogenes (v-abl, v-src). Under a variety of experimental conditions, we have found no evidence to support the notion that type I topoisomerase activity is modulated by tyrosine phosphorylation in vivo.
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PMID:A comparison of topoisomerase I activity in normal and transformed cells. 301 75

The diagnosis of 'ALL with maturation' (ALLm) is proposed. One hundred and one patients with untreated ALL were entered into this study. The diagnosis of ALLm was made when more than 20% of all nucleated elements in the bone marrow showed maturation beyond prolymphocytes by light microscopic examination. The mature-appearing leukemic cells showed the same immunophenotype to remaining lymphoblasts. The number of ALLm cases was 19 (18.8%). The mean age at presentation of ALLm was 29 +/- 18, older than that of 18 +/- 16 of the remaining typical ALL (ALLt) (P = 0.015). Remission was induced with daunorubicin, vincristine, prednisone and L-asparaginase. Only two of 19 ALLm patients achieved CR after 4 weeks induction chemotherapy. In contrast, 57 of 82 (69.5%) ALLt patients achieved CR after the same induction chemotherapy. There was no significant difference in immunophenotype of ALLm compared with ALLt. Labeling index of DNA topoisomerase IIalpha (TopoLI) was studied by immunohistochemistry. Initial TopoLI of ALLm (221 +/- 147) was much lower than that of ALLt (609 +/- 262, P = 0.005). Furthermore, the remaining leukemic cells after chemotherapy were not labeled with anti-DNA topoisomerase IIalpha. The P53 protein was expressed in nine of 18 ALLm cases (50.0%) and P-glycoprotein was not expressed in ALLm cases. Twelve of 19 ALLm cases were studied for carrying bcr/abl fusion by karyotyping and/or fluorescent in situ hybridization. Only two cases revealed bcr/abl fusion. In conclusion, ALLm is a separate entity of ALL which has a very poor clinical course and is independent of other prognostic factors. The morphologically mature leukemic cells are in resting GO phase.
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PMID:Acute lymphoblastic leukemia with maturation--a new entity with clinical significance. 963 14

The cell line K-562, which carries bcr/abl rearrangement of type b3a2 is resistant to apoptosis induced by topoisomerase II inhibitors. K-562 cells were treated with complexes of cationic liposomes (DMRIE-DOPE and Dcchol-DOPE) and antisense oligonucleotides (AS-ODNs) directed against the b3a2 type of bcr/abl mRNA and non sense oligonucleotides (NS-ODNs), in a 3:1 lipid/DNA ratio during 72 hours, then they were incubated for a further 24 hours with idarubicin (IDA), 0.5 microgram/ml, to induce apoptosis. It was evaluated by morphology to the microscope of fluorescence. Cells treated with the complexes DMRIE-DOPE and Dcchol/DOPE with the specific AS-ODN showed a higher apoptosis percentage induced by IDA (mean +/- SD: 14.74 +/- 2.07 and 20.43 +/- 4.58, respectively) compared with controls not treated with ODNs (mean +/- SD: 8.08 +/- 0.82); (p < 0.05). These data indicate that the AS-ODNs directed against the b3a2 type of bcr-abl mRNA renders the cell line K-562 sensitive to IDA at the mentioned concentration.
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PMID:[Antisense oligonucleotides increase the apoptotic effect of idarubicin in K-562 cell line]. 1083 12

Therapy-related myelodysplastic syndrome and acute myelogenous leukemia are increasingly being recognized as treatment complications in patients receiving chemotherapy or radiotherapy for previous neoplasms. However, therapy-related chronic myelogenous leukemia is relatively rare. A 61-year-old woman with a history of radiation therapy for breast cancer had previously, in 2007, received 4 courses of chemotherapy (RFM: rituximab, fludarabine, and mitoxantrone) for follicular lymphoma. In 2010, she was diagnosed with chronic-phase chronic myelogenous leukemia (CML) with Philadelphia chromosome but no other cytogenetic anomalies. Although a complete cytogenetic response (CCyR) was achieved with imatinib therapy, she developed leukocytosis with lymphoblasts and lymphoid crisis was diagnosed in January 2013. G-banded karyotyping showed 45, XX, -7, t, (9;22)(q33;q11.2). Unrelated bone marrow stem cell transplantation was performed after she had achieved a CCyR with dasatinib therapy. Polymerase chain reaction detected no major bcr/abl transcript in her bone marrow 42 days after transplantation. The majority of secondary leukemias resulting from the use of cytotoxic drugs can be divided into two well-defined groups depending on whether the patient has received alkylating agents or topoisomerase II inhibitors. However, concerns regarding the leukemogenic potential of fludarabine-based chemotherapy are growing. The potential risk of therapy-related leukemias including CML needs to be considered following fludarabine-based chemotherapy.
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PMID:[Therapy-related chronic myelogenous leukemia following RFM therapy in a patient with follicular lymphoma]. 2518 88