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 antitrypanosomal and antifiliarial drug suramin is currently under investigation for treatment of advanced malignancies including prostatic cancer, adrenocortical cancer, and some lymphomas and sarcomas. Here we show that suramin is a potent inhibitor of the nuclear enzyme DNA topoisomerase II. Suramin inhibited purified yeast topoisomerase II with an IC50 of about 5 microM, as measured by decatenation or relaxation assays. Suramin did not stabilize the covalent DNA-topoisomerase II reaction intermediate ("cleavable complex"), whereas other inhibitors of this enzyme, such as amsacrine, etoposide, and the ellipticines, are known to stabilize the intermediate. In contrast, the presence of suramin strongly inhibited the cleavable-complex formation induced by amsacrine or etoposide. Accumulation of the endogenous cleavable complex was also inhibited. Suramin entered the nucleus of DC-3F Chinese hamster fibrosarcoma cells exposed to radiolabeled suramin for 24 hr as shown by both optic and electron microscopy. The suramin present in the nucleus seemed to interact with topoisomerase II, since suramin reduced the number of amsacrine-induced protein-associated DNA strand breaks in DC-3F cells and protected these cells from the cytotoxic action of amsacrine. Cells resistant to 9-hydroxyellipticine, which have been shown to have an altered topoisomerase II activity, are about 7-fold more resistant to suramin than the sensitive parental cells as shown by 72-hr growth inhibition assay. Our results suggest that DNA topoisomerase II is a target of suramin action and that this action may play a role in the cytotoxic activity of suramin.
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PMID:Suramin is an inhibitor of DNA topoisomerase II in vitro and in Chinese hamster fibrosarcoma cells. 131 77

Suramin cytotoxicity was studied in a panel of human lung cancer cell lines by the MTT assay. The concentrations of suramin which induced 50% growth inhibition (IC50) ranged from 130 to 3715 microM for the cell lines growing in medium containing 10% fetal calf serum (FCS). In only one cell line was the IC50 at a concentration that can be reached in plasma of patients treated with suramin. Suramin was 18 and 3.3 times more cytotoxic on NCI-N417 cells growing in 2% FCS and in HITES serum-free medium, respectively, than growing in 10% FCS. No difference in suramin cytotoxicity was observed between small and non-small cell lung cancer cell lines. At the lower concentrations tested, suramin stimulated proliferation of the two small cell lung cancer cell lines, NCI-H187 and NCI-N417. Of several growth factors tested, none induced stimulation of growth in NCI-H187 and NCI-N417 cell lines, nor did they in any way alter the stimulatory effect of suramin. Cell counting, DNA flow cytometric analysis and Ki-67 staining confirmed a higher proliferative state in suramin-exposed NCI-H187 cells as compared with untreated cells. However, topoisomerase II-alpha gene expression remained unchanged, as assessed by northern blot analysis and immunostaining. Suramin had an inhibitory effect on topoisomerase II activity, as assessed by the kDNA decatenation assay, with an IC50 of approximately 40 microM. In conclusion, suramin has significant cytotoxic activity in a minority of human lung cancer cell lines, and it stimulates proliferation in some instances. The pleiotropic action of suramin observed should caution on the possibility of tumour acceleration in patients being treated with this drug.
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PMID:Effects of suramin on human lung cancer cell lines. 771 32

Suramin, a hexasulphonated naphthylurea with activity in prostatic cancer, possesses a wide variety of antitumour mechanisms of action, one of which is the inhibition of topoisomerase II. In this in vitro study, suramin was combined with the topoisomerase I inhibitor, camptothecin. Several suramin concentrations (0.2-3000 microM) were combined with camptothecin (0.4 pM-20 microM) in MCF-7 and PC3 human cancer cell line cultures. In addition, we studied the topoisomerase II and I gene expression by northern blot analysis, and the cell cycle distribution by flow cytometry, after exposure to suramin. While there was only an additive effect when suramin and camptothecin were added simultaneously, a remarkable synergism was obtained when camptothecin was added after a 3-day exposure to suramin. Topoisomerase II and I gene expression and the number of cells in S phase were significantly reduced after exposure to suramin. In conclusion, interaction of suramin with camptothecin is schedule-dependent and can be synergistic. These findings might help in identifying optimal combinations of suramin or other topoisomerase II inhibitors, with topoisomerase I inhibitors.
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PMID:In vitro sequence-dependent synergistic effect of suramin and camptothecin. 783 42

Suramin, a highly sulfonated drug, has been reported to be effective against several human malignancies in vitro and in vivo, and currently is undergoing clinical trials against prostate tumors. The biochemical and molecular mechanisms for suramin's antiproliferative activity are not clear. In order to define the biochemical basis for its antitumor activity and to enhance suramin's chemotherapeutic potential while decreasing its toxicity, we have examined interactions of suramin with topoisomerase I and II and several clinically active anticancer drugs against the human prostate (PC3 and LNCaP) cancer cell line. While etoposide, m-AMSA, camptothecin, and SN-38 (the active metabolite of CPT-11) were active in killing prostate cells as single agents, combinations of suramin and these agents were antagonistic against these cells. We found that suramin inhibited activities of purified topoisomerase I and II in vitro as measured by relaxation and cleavage assays. Further studies indicated that suramin also inhibited the drug-induced DNA damage in vitro and in isolated nuclei. These findings indicate that combinations of suramin with topoisomerase inhibitors, for example, VP-16, m-AMSA, or CPT, may not be beneficial to patients receiving suramin-containing chemotherapy.
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PMID:Suramin inhibits DNA damage in human prostate cancer cells treated with topoisomerase inhibitors in vitro. 839 91

We show herein that human DNA topoisomerase II beta is functional in yeast. It can complement a yeast temperature-sensitive mutation in topoisomerase II. The effect on human topoisomerase II beta of a number of topoisomerase II inhibitors was analysed in a yeast in vivo system and compared with that of human topoisomerase II alpha and wild-type yeast topoisomerase II. A drug permeable yeast strain (JN394 top2-4) was used to analyse the in vivo effects of known anti-topoisomerase II agents on human topoisomerase II beta transformants. A parallel analysis on human topoisomerase II alpha transformants provides the first in vivo analysis of the responses of yeast bearing the individual isoforms to these drugs. The strain was analysed at 35 degrees C, a non-permissive temperature at which only plasmid-borne topoisomerase II is active. A shuttle vector with either human topoisomerase II beta, human topoisomerase II alpha or yeast topoisomerase II under the control of a GAL1 promoter was used. The key findings were that amsacrine produced comparable levels of cell killing with both alpha and beta, whilst etoposide, doxorubicin and mitoxantrone produced higher degrees of cell killing with alpha than with beta or yeast topoisomerase II. Merbarone had the greatest effect on the yeast strain bearing plasmid-borne yeast topoisomerase II. Suramin, quercetin and genistein showed little cell killing in this system. This yeast in vivo system provides a powerful way to analyse the effects of anti-topoisomerase II agents on transformants bearing the individual human isoforms. This system also provides a means of analysing putative drug-resistance mutations in human topoisomerase II beta or to select for drug-resistance mutations in human topoisomerase II beta.
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PMID:Complementation of temperature-sensitive topoisomerase II mutations in Saccharomyces cerevisiae by a human TOP2 beta construct allows the study of topoisomerase II beta inhibitors in yeast. 902 79

Ribosomal protein L3 (L3) has been demonstrated to participate in formation of the peptidyltransferase center and is essential for its catalytic activity. In the present study we show that L3 is able to bind nucleotide triphosphates with high and specific affinity in vitro. L3 was serendipitously identified by screening of a genomic phage library from a primitive kinetoplastid flagellate Trypanoplasma borreli with the ATPase domain of the topoisomerase II gene as a probe. The cloned gene was overexpressed and purified as a his-tag fusion protein in E. coli. Radioligand binding experiments, using [gamma-35S]ATP, showed that L3 is able to bind ATP but also GTP and UTP with similar high affinity (IC50 50-100 nM), while it has no ATPase activity. Furthermore, we showed that L3 has more than 500-fold higher affinity for nucleotide triphosphates compared to the corresponding nucleotide monophosphates and diphosphates. Molecular genetic and biochemical analyses allowed us to localize the NTP binding domain of L3 to the N-terminal 296 residues. Suramin, a polysulfonated naphthylamine derivative of urea, known for its chemotherapeutic effects completely inhibited the binding of [gamma-35S]ATP at subclinical levels. Results obtained with surface plasmon resonance technology showed that suramin both forms weak multimolecular complexes with L3 and binds strongly to L3 in nearly stoichiometric amounts.
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PMID:Suramin blocks nucleotide triphosphate binding to ribosomal protein L3 from Trypanoplasma borreli. 1071 4

Suramin has shown promising antitumour activity against several tumour types, both in vitro and in vivo, but the clinical utility of this compound is hampered by its unfavourable toxicity profile. In the present study, the semi-automated fluorometric microculture cytotoxicity assay (FMCA) was employed for evaluation of the cytotoxicity of seven suramin analogues in vitro in a panel of human tumour cell lines and in primary cultures of tumour cells from patients. Like suramin, the analogues showed little sensitivity to resistance mechanisms involving P-glycoprotein, topoisomerase II, multidrug resistance associated protein and glutathione-mediated drug resistance. In the cell line panel, NF067 and FCE 26644 showed activity comparable with suramin. All analogues were less potent than suramin in patient cells except for FCE 26644. Correlation to suramin activity patterns in the cell line panel was highest for NF037 and low to moderate for the remaining analogues. In patient cells, high correlation coefficients were obtained for FCE 26644, NF110, NF031 and NF037. The results indicate that the cytotoxic activity of suramin on patient tumour cells is shared by the analogues with FCE 26644 being the most active. The pharmacophore for cytotoxicity in patient cells may be different from that observed in the cell lines.
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PMID:Antitumour activity of suramin analogues in human tumour cell lines and primary cultures of tumour cells from patients. 1076 55