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

Western blotting, indirect immunolocalization, flow cytometry, and a functional assay for drug-induced strand breakage were utilized to examine topoisomerase (topo) II levels during granulocytic maturation in HL-60 human progranulocytic leukemia cells and in samples of normal human marrow. Indirect immunofluorescence revealed that the intensity of the signal for topo II in unsynchronized log phase HL-60 cells varied widely. Indirect immunolabeling combined with propidium iodide staining and two-parameter flow cytometry revealed that topo II levels increased an average of 2-fold as cells progressed from G1 to G2/M. When HL-60 cells were induced to mature toward granulocytes, topo II levels progressively decreased and became undetectable by functional assays, by indirect immunoperoxidase staining, and by Western blotting with an antibody which identified Mr 170,000 and Mr 180,000 forms of topo II. Similar changes were detected during normal granulocytic maturation in human marrow in vivo. Western blotting revealed that levels of the Mr 170,000 (proliferation-associated) isoform of topo II were highest in marrow fractions enriched in progranulocytes and myelocytes, intermediate in unfractionated marrow from normal volunteers, and undetectable in mature granulocytes. The Mr 180,000 topo II polypeptide was also diminished or absent from mature granulocytes. In further experiments, marrow samples from normal volunteers were subjected to flow cytometry after labeling of topo II and various cell surface markers. Levels of the Mr 170,000 topo II polypeptide in CD34-positive cells (multipotent and committed progenitors from several hematopoietic lineages) were indistinguishable from levels observed in the HL-60 leukemia cell line. These results suggest that topo II levels in highly proliferative normal human myeloid cells in vivo approach levels found in corresponding neoplastic cell lines in vitro. Conversely, as the same cells mature into granulocytes in vivo or in vitro, levels of both molecular weight forms of topo II diminish. These results provide a framework for the further investigation of topo II levels and drug sensitivity in human leukemia.
Cancer Res 1991 Jul 01
PMID:Topoisomerase II levels during granulocytic maturation in vitro and in vivo. 164 69

We have isolated two etoposide (VP16)-resistant cell lines, KB/VP-1 and KB/VP-2, from human cancer KB cells after stepwise exposure to increasing doses of VP16. KB/VP-1 and KB/VP-2 showed 30- and 50-fold higher resistance to VP16 and also 20- and 30-fold higher resistance to teniposide than the parent cell line. Furthermore, both resistant cell lines showed more than 2-fold cross-resistance to Adriamycin and daunomycin than KB cells. The levels of accumulation and outward transport of radioactive VP16 were similar in KB/VP-1, KB/VP-2, and KB. The activity of nuclear extracts of DNA topoisomerase II for both KB/VP-1 and KB/VP-2 assayed by decatenation of kinetoplast DNA was consistently similar to that of KB. However, in both immunoblot assay with specific anti-topoisomerase II antibody and Northern blot analysis with specific human DNA topoisomerase II complementary DNA, cellular levels of topoisomerase II in both resistant cell lines were less than one-tenth the level in KB. The cellular levels of DNA topoisomerase I, however, were similar between the mutants and their parent. A quantitative precipitation assay of covalent DNA-topoisomerase II complexes showed greatly reduced VP16-induced cleavages of 3'-32P-DNA by nuclear extracts of KB/VP-1 or KB/VP-2 cells in comparison with KB cells. The relative specific phosphorylation of DNA topoisomerase II was about 14- to 18-fold higher in the mutants than in the parental cells. Phosphoamino acid analysis of DNA topoisomerase II showed that serine was the phosphorylated amino acid in all three cell lines, KB, KB/VP-1, and KB/VP-2. These data suggest that reduced expression of DNA-topoisomerase II might account for the acquired VP16 resistance and reduced VP16-induced cleavages of DNA-topoisomerase II complexes in both VP16-resistant variants.
Cancer Res 1991 Aug 01
PMID:Increased phosphorylation of DNA topoisomerase II in etoposide-resistant mutants of human cancer KB cells. 164 96

CPT-11, a derivative of camptothecin, has drawn attention to cancer chemotherapy because of the specific mode of action, and the clinical study is now under progress. Liu et al. proved that camptothecin was a DNA topoisomerase I inhibitor, and some kinds of antitumor agents have been recognized as DNA topoisomerase II inhibitors. Based on these findings, DNA topoisomerases have emerged as target enzymes of antitumor agents in cancer chemotherapy. This paper dealt with investigation on the cytotoxic effects induced by combined use of DNA topoisomerase targeting antitumor agents, especially using CPT-11 as a core antitumor agent. Synchronous administration of CPT-11 with other antitumor agents induced cytotoxic effects less than metachronous administration of CPT-11 with other antitumor agents, especially preceding use of CPT-11. Dose of antitumor agents was not necessarily correlated to the cytotoxic effects. In some instances, small doses of the agents showed better therapeutic effects than large doses. The cytotoxic effects of vincristine, vindesine, and hydroxyurea were reduced by combination with CPT-11. On the other hand, non-cytotoxic agents such as aphidicolin, novobiocin, propentofylline, pentoxifylline, norfloxacin, and tosufloxacin enhanced the cytotoxic effects of CPT-11. Hypothetical consideration of cell killing and acquisition of drug resistance was proposed.
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PMID:[Combination cancer chemotherapy using a DNA topoisomerase inhibitor CPT-11, as a core agent--the in vitro evaluation]. 165 82

HL-60/AMSA is a human leukemia cell line that is 50- to 100-fold more resistant to the cytotoxic actions of the topoisomerase II-reactive intercalator amsacrine than is its drug-sensitive HL-60 parent line. Previously, we have shown that the topoisomerase II from HL-60/AMSA is also resistant to inhibition by amsacrine and other intercalating agents. We therefore sought the molecular basis for the resistance of the topoisomerase II of HL-60/AMSA and, by inference, of the HL-60/AMSA line itself. We report the cloning and sequencing of the topoisomerase II genes from both the sensitive and resistant leukemia cell lines using polymerase chain reaction technology. We have identified a single base change associated with the drug-resistant form of topoisomerase II. This mutation is present in both cloned HL-60/AMSA complementary DNA and extracted HL-60/AMSA genomic DNA. A rapid assay for this mutation in clinical samples has been developed and applied to the DNA of cells from both normal volunteers and leukemia patients. Thus far, the HL-60/AMSA genotype has not been identified in the cells from any individual, suggesting that this genotype is indeed a mutation and not an allelic form of topoisomerase II. The novel assay developed will allow a rapid search for the prevalence of this mutation in clinical samples from patients with leukemia who have relapsed following intercalator therapy.
Cancer Res 1991 Sep 01
PMID:Identification of a point mutation in the topoisomerase II gene from a human leukemia cell line containing an amsacrine-resistant form of topoisomerase II. 165 12

The nuclear matrix of eukaryotic cells comprises a dynamic framework on which DNA is organized into discrete functional units of replication and transcription. There is growing evidence that matrix-associated DNA and proteins are direct targets of a wide range of clinically active anticancer agents. DNA associated with matrix-bound replication and transcription sites has a relatively open conformation and is preferentially damaged by ionizing radiation and certain alkylating agents. Fludarabine phosphate, a purine antimetabolite, inhibits DNA replication by blocking the synthesis of matrix-associated primer RNA and RNA-primed Okazaki fragments. VM-26 and m-AMSA appear to interact specifically with nuclear matrix topoisomerase II, and one mechanism of cellular resistance to these agents is associated with depletion of the matrix enzyme. Studies of the interactions of anticancer agents with targets in the nuclear matrix should provide further insight into the mechanisms by which these agents exert their therapeutic effects.
Cancer Cells 1991 Apr
PMID:Nuclear matrix targets for anticancer agents. 165 99

Several recently developed derivatives of bis(2,6-dioxopiperazine) have been shown to be new antitumor agents and are currently under clinical trials. We found that the mother compound of the bis(2,6-dioxopiperazine)s, ICRF-154, and its derivatives, ICRF-159, ICRF-193, and MST-16, are all inhibitors of mammalian type II DNA topoisomerase. By decatenation assay using kinetoplast DNA from Crithidia fasciculata, inhibition of purified calf thymus topoisomerase II by these compounds was investigated. Potency of inhibition was in the following order: ICRF-193 greater than ICRF-154 = ICRF-159 greater than MST-16. The doses giving 50% inhibition were 2, 13, 30 and 300 microM, respectively, for these compounds. ICRF-193, the most potent inhibitor, however, did not inhibit topoisomerase I at concentrations up to 300 microM. Addition of excess enzyme, but not of the substrate DNA, overcame the inhibition by ICRF-193. The drug did not stimulate the formation of cleavable complex between DNA and the enzyme. Furthermore, ICRF-193 even inhibited the formation of enzyme-mediated DNA cleavage induced by etoposide or 4'-[9-acridinylamino)methanesulfon-m-anisidide. These observations, together with the finding that ICRF-193 did not intercalate into DNA, suggest that ICRF-154 and related compounds are specific inhibitors of topoisomerase II with different modes of action: i.e., they interfere with some step(s) before the formation of the intermediate cleavable complex in the catalytic cycle. This is a property quite distinct from previously known cleavable complex-forming type topoisomerase II-targeting antitumor agents such as acridines, anthracyclines, and epipodophyllotoxins, but rather, mechanistically similar to the recently reported group of inhibitors that includes merbarone, aclarubicin, and fostriecin.
Cancer Res 1991 Sep 15
PMID:Inhibition of topoisomerase II by antitumor agents bis(2,6-dioxopiperazine) derivatives. 165 4

In the accompanying paper (K. Tanabe, Y. Ikegami, R. Ishida, and T. Andoh, Cancer Res., 51: 4903-4908, 1991), we showed that ICRF-154 and -193, dioxopiperazine derivatives, inhibited the activity of purified topoisomerase II, without formation of a cleavable DNA-protein complex. In order to see whether ICRF-154 and ICRF-193 affect cellular topoisomerase II in situ or not, we examined the effect of these drugs on etoposide (VP-16)-induced, topoisomerase II-mediated DNA breaks in RPMI 8402 cells by alkaline sedimentation analysis. When RPMI 8402 cells were exposed to VP-16 in the presence of ICRF-154 or ICRF-193 for 1 h, VP-16-induced DNA strand breaks were greatly inhibited by both ICRF compounds. In parallel with this observation, VP-16-induced growth inhibition was also reversed by ICRF-193. Exposure of cells to ICRF-154 resulted in a progressive accumulation of cells with 4C DNA content. Although mitotic index did not significantly increase, mitotic abnormalities were seen in cells exposed to ICRF-193 or ICRF-154: all mitotic cells exhibited early mitotic figures with fewer condensed and entangled chromosomes. The most sensitive phase of the cell cycle to ICRF-154 was the G2-M. ICRF-154 did not affect the spindle formation. However, abnormally oriented spindles were observed in drug-treated cells in parallel with the appearance of multinucleated cells. The results suggest that ICRF-154 and -193 inhibit topoisomerase II activity in RPMI 8402 cells, and this effect resulted in the appearance of cells in G2 and early M phase with fewer condensed and entangled chromosomes and of cells with multilobed nuclei.
Cancer Res 1991 Sep 15
PMID:Inhibition of intracellular topoisomerase II by antitumor bis(2,6-dioxopiperazine) derivatives: mode of cell growth inhibition distinct from that of cleavable complex-forming type inhibitors. 165 5

DNA topoisomerases are essential nuclear enzymes that are involved in DNA replication. Clinically useful antitumor drugs such as doxorubicin, daunorubicin (anthracyclines), etoposide, teniposide (epipodophyllotoxins), and amsacrine (an aminoacridine) interfere with the function of topoisomerase II and camptothecin and its analogs inhibit topoisomerase I. Some mammalian tumor cells that express resistance to drugs that interfere with topoisomerase I or topoisomerase II have alterations in their respective topoisomerases. In this paper, we review the functions of the topoisomerases, discuss aspects of their cellular regulation, ask how interference with topoisomerase function can lead to tumor cell death, discuss the biochemical features of tumor cells that are resistant to these anti-topoisomerase drugs, and, in the context of drug resistance, we raise questions about how these drugs exert their cytotoxicity.
Semin Cancer Biol 1991 Aug
PMID:Mechanisms of resistance to drugs that inhibit DNA topoisomerases. 165 18

Two different classes of therapy-related acute myeloid leukemia (t-AML) seem to emerge. One class follows therapy with alkylating agents, increases in frequency with age, often presents with myelodysplasia (MDS), responds poorly to chemotherapy, and shows monosomy 7(-7), monosomy 5(-5), or loss of various parts of the long arms of these chromosomes (5q- and 7q-). The other class is related to therapy with cytostatic drugs targeting at DNA-topoisomerase II, often presents with overt leukemia, responds more favorably to chemotherapy, and shows balanced chromosome aberrations, primarily translocations involving chromosome bands 11q23 and 21q22. These two classes of t-AML may have their counterparts in de-novo acute myeloid leukemia (de-novo AML).
Cancer Genet Cytogenet 1991 Aug
PMID:Two different classes of therapy-related and de-novo acute myeloid leukemia? 165 39

The effect of combinations of the anthracyclines aclarubicin and daunorubicin was investigated in a clonogenic assay using the human small cell lung cancer cell line OC-NYH and a multidrug-resistant (MDR) murine subline of Ehrlich ascites tumor (EHR2/DNR+). It was found that the cytotoxicity of daunorubicin in OC-NYH cells was antagonized by simultaneous exposure to nontoxic concentrations of aclarubicin. Coordinately, aclarubicin inhibited the formation of daunorubicin-induced protein-concealed DNA single-strand breaks and DNA-protein cross-links in OC-NYH cells when assayed by the alkaline elution technique. Aclarubicin had no influence on the accumulation of daunorubicin in these cells. In contrast, the accumulation of daunorubicin in EHR2/DNR+ cells was enhanced by more than 300% when the cells were simultaneously incubated with the MDR modulator verapamil, aclarubicin, or the two agents combined. Yet the cytotoxicity of daunorubicin was potentiated significantly only by verapamil. The increased cytotoxicity of daunorubicin in the presence of verapamil was completely antagonized when aclarubicin was used together with the MDR modulator. Finally, the effect of daunorubicin on the DNA cleavage activity of purified topoisomerase II in the presence and absence of aclarubicin was examined. It was found that daunorubicin stimulated DNA cleavage by topoisomerase II at specific DNA sites. The addition of aclarubicin completely inhibited the daunorubicin-induced stimulation of DNA cleavage. Taken together, these data indicate that aclarubicin-mediated inhibition of daunorubicin-induced cytotoxicity is due mainly to a drug interaction with the nuclear enzyme topoisomerase II. This antagonism at the nuclear level explains why aclarubicin is a poor modulator of daunorubicin resistance even though aclarubicin is able to increase the intracellular accumulation of daunorubicin in a MDR cell line.
Cancer Res 1991 Oct 01
PMID:Antagonistic effect of aclarubicin on daunorubicin-induced cytotoxicity in human small cell lung cancer cells: relationship to DNA integrity and topoisomerase II. 165 44


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