Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.2 (topoisomerase)
 9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The epipodophyllotoxins, etoposide and teniposide, have been used in leukemias and malignant lymphomas for the past 15 years. Although etoposide has acquired a place in many first-line protocols for lymphomas and, more recently, for leukemias, the role of teniposide has remained limited. Teniposide is a more potent inhibitor of topoisomerase II than etoposide, and has a less toxic effect on hematopoietic progenitor cells. Both drugs have been regarded as equitoxic and cross-resistant. The role of teniposide in front-line treatment of leukemias has only been established in childhood acute lymphoblastic leukemia (ALL). Some promising results have been obtained in small numbers of patients with refractory adult ALL and acute monoblastic leukemia. However, the remission rates and remission duration were not significantly different from those of other combination regimens. Data on teniposide in untreated acute nonlymphoblastic leukemia are very scarce. In non-Hodgkin's lymphoma, the antineoplastic activity of teniposide has been demonstrated in studies by the European Organization for Research and Treatment of Cancer and in two large studies conducted by the Australian and New Zealand Lymphoma Co-operative Chemotherapy Study Group. In these studies, teniposide had comparable but not significantly better activity than vincristine. The dose-dependent antineoplastic activity of teniposide has led to its use in several conditioning regimens in bone marrow transplantation for leukemias and lymphomas. The limited clinical data currently available on teniposide seem to warrant further clinical trials with this agent in leukemias and lymphomas.
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PMID:Teniposide in lymphomas and leukemias. 141 40

The role of high-dose etoposide in the initial treatment of newly diagnosed adult ALL was assessed in a combined clinical and laboratory study. Therapy on protocol JH8802 consisted of two induction modules, module 1 containing prednisone, vincristine, high-dose etoposide and L-asparaginase (L-asp), followed by module 2 containing cytarabine (Ara-C) and daunorubicin (DNR). Patients achieving a complete remission (CR) underwent bone marrow transplantation (BMT) or intensive maintenance therapy. Results were compared to the preceding protocol (JH8302), which was similar except for omission of etoposide and L-asp. The CR rate following module 1 was 45% on protocol JH8802 and 9% on protocol JH8302 (p < 0.0002). Nonetheless, the two protocols had similar CR rates following module 2 (69% on protocol JH8302; 77% on JH8802) and indistinguishable survivals. Laboratory investigations performed on blasts harvested prior to chemotherapy revealed two factors that could potentially contribute to decreased etoposide sensitivity in ALL blasts. A flow microfluorimetry-based assay of nuclear DNR accumulation detected small P-glycoprotein (Pgp)-mediated decreases in drug accumulation in a quarter of the samples. Western blotting demonstrated that topoisomerase II was present in all samples but was diminished in amount compared to the Molt3 human ALL cell line. Immunoperoxidase staining with affinity-purified antibodies revealed that topo II alpha, the target for etoposide, was detectable in only a minority of the blasts (median 7.5%, range < 1-35%) at diagnosis. These observations raise the possibility that alterations in drug accumulation and diminished target enzyme levels might both limit the long-term efficacy of a single course of high dose etoposide administered early in the treatment of adult ALL.
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PMID:Addition of etoposide to initial therapy of adult acute lymphoblastic leukemia: a combined clinical and laboratory study. 902 88