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)

We established a drug sensitivity panel consisting of 24 human lung cancer cell lines. Using this panel, we evaluated 26 anti-cancer agents: three alkylators, three platinum compounds, four antimetabolites, one topoisomerase I inhibitor, five topoisomerase II inhibitors, seven antimitotic agents and three tyrosine kinase inhibitors. This panel showed the following: a) Drug sensitivity patterns reflected their clinically-established patterns of action. For example, doxorubicin and etoposide were shown to be active against small cell lung cancer cell lines and mitomycin-C and 5-fluorouracil were active against non-small cell lung cancer cell lines, in agreement with clinical data. b) Correlation analysis of the mean graphs derived from the logarithm of IC50 values of the drugs gave insight into the mechanism of each drug's action. Thus, two drug combinations with reverse or no correlation, such as the combination of cisplatin and vinorelbine, might be good candidates for the ideal two drug combination in the treatment of lung cancer, as is being confirmed in clinical trials. c) Using cluster analysis of the cell lines in the panel with their drug sensitivity patterns, we could classify the cell lines into four groups depending on the drug sensitivity similarity. This classification will be useful to elucidate the cellular mechanism of action and drug resistance. Thus, our drug sensitivity panel will be helpful to explore new drugs or to develop a new combination of anti-cancer agents for the treatment of lung cancer.
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PMID:Establishment of a drug sensitivity panel using human lung cancer cell lines. 1035 21

Bisdioxopiperazine drugs such as ICRF-187 are catalytic inhibitors of DNA topoisomerase II, with at least two effects on the enzyme: namely, locking it in a closed-clamp form and inhibiting its ATPase activity. This is in contrast to topoisomerase II poisons as etoposide and amsacrine (m-AMSA), which act by stabilizing enzyme-DNA-drug complexes at a stage in which the DNA gate strand is cleaved and the protein is covalently attached to DNA. Human small cell lung cancer NYH cells selected for resistance to ICRF-187 (NYH/187) showed a 25% increase in topoisomerase IIalpha level and no change in expression of the beta isoform. Sequencing of the entire topoisomerase IIalpha cDNA from NYH/187 cells demonstrated a homozygous G-->A point mutation at nucleotide 485, leading to a R162Q conversion in the Walker A consensus ATP binding site (residues 161-165 in the alpha isoform), this being the first drug-selected mutation described at this site. Western blotting after incubation with ICRF-187 showed no depletion of the alpha isoform in NYH/187 cells in contrast to wild-type (wt) cells, whereas equal depletion of the beta isoform was observed in the two sublines. Alkaline elution assay demonstrated a lack of inhibition of etoposide-induced DNA single-stranded breaks in NYH/187 cells, whereas this inhibition was readily apparent in NYH cells. Site-directed mutagenesis in human topoisomerase IIalpha introduced into a yeast Saccharomyces cerevisiae strain with a temperature-conditional yeast TOP2 mutant demonstrated that R162Q conferred resistance to the bisdioxopiperazines ICRF-187 and -193 but not to etoposide or m-AMSA. Both etoposide and m-AMSA induced more DNA cleavage with purified R162Q enzyme than with the wt. The R162Q enzyme has a 20-25% decreased catalytic capacity compared to the wt and was almost inactive at <0.25 mM ATP compared to the wt. Kinetoplast DNA decatenation by the R162Q enzyme at 1 mM ATP was not resistant to ICRF-187 compared to wt, whereas it was clearly less sensitive than wt to ICRF-187 at low ATP concentrations. This suggests that it is a shift in the equilibrium to an open-clamp state in the enzyme's catalytic cycle caused by a decreased ATP binding by the mutated enzyme that is responsible for bisdioxopiperazine resistance.
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PMID:Human small cell lung cancer NYH cells selected for resistance to the bisdioxopiperazine topoisomerase II catalytic inhibitor ICRF-187 demonstrate a functional R162Q mutation in the Walker A consensus ATP binding domain of the alpha isoform. 1041 8

Drug resistance is a major problem in patients with small cell lung cancer; in fact, most die of resistant disease, despite an initial response. Several markers of drug resistance have been described in preclinical models, but the mechanism of drug resistance in lung cancer patients remains unknown. The objective of this study was to evaluate the role of the expression of a number of markers of drug resistance, proliferation, and apoptosis in relation to response to chemotherapy and survival in patients with small cell lung cancer. Tumor samples were derived from 93 previously untreated patients who were randomized in a Phase III study to receive cyclophosphamide, epirubicine, and etoposide or cyclophosphamide, epirubicine and vincristine alternating with carboplatin and etoposide. Paraffin-embedded samples, derived from the primary tumor site prior to chemotherapy, were analyzed by immunohistochemistry for expression of markers implicated in drug resistance [topoisomerase (topo) IIalpha, topo IIbeta, and multidrug resistance-associated protein], apoptosis (p53, p21, and bcl-2), or proliferation (Ki67). Response prediction was analyzed by chi2 test and logistic regression analysis; overall and disease-free survival curves were compared by log-rank test and Cox regression analysis. Shorter survival was observed in patients with extensive disease (P = 0.037) and poorer performance status (P = 0.028) and in patients whose tumors expressed high topo IIalpha levels (P = 0.01) and high Ki67 (P = 0.024). By multivariate analysis, the following factors were found to be predictive for worse survival: high expression levels of topo IIalpha, Ki67, and bcl-2; male sex; and extensive disease. High topo IIbeta expression was found to be predictive for lower overall and complete response rate. No relationship between apoptotic pathway markers or MRP and response to chemotherapy was observed. In conclusion, high expression of topo IIalpha was predictive of worse survival, and high expression of topo IIbeta was predictive of lower response rates. Furthermore, lower survival probability was observed in patients with bcl-2-positive tumors. Immunohistochemical assessment of these markers in diagnostic biopsies may give important prognostic information and may help selecting patients in the worse prognostic categories for new therapeutic strategies.
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PMID:Expression of DNA topoisomerase IIalpha and topoisomerase IIbeta genes predicts survival and response to chemotherapy in patients with small cell lung cancer. 1047 85

Inhibitors of topoisomerases are widely used in the treatment of cancer, including inhibitors of topoisomerase I (camptothecin analogs such as irinotecan and topotecan) and topoisomerase II (etoposide and doxorubicin). The novel bis-phenazine, XR5944, is a joint inhibitor of topoisomerase I and II as shown by the stabilization of topoisomerase-dependent cleavable complexes. XR5944 demonstrated exceptional activity against human and murine tumor cells in vitro and in vivo. In a range of cell lines XR5944 (IC50 0.04-0.4 nM) was significantly more potent than TAS-103, originally proposed as a joint topoisomerase I and II inhibitor, as well as agents specific for topoisomerase I or II (topotecan, doxorubicin and etoposide). In addition, XR5944 was unaffected by atypical drug resistance and retained significant activity in cells overexpressing P-glycoprotein or multidrug resistance-associated protein. Antitumor efficacy of XR5944 was demonstrated in human carcinoma xenograft models (H69 small cell lung cancer and HT29 colon). In the HT29 model, which is relatively unresponsive to chemotherapy, XR5944 (15 mg/kg i.v., q4dx3) induced tumor regression in the majority of animals (six of eight), whereas TAS-103, dosed at its maximum tolerated dose (45 mg/kg i.v., q7dx3), only induced a delay in tumor growth compared with control animals. In the H69 model, low doses of XR5944 (5 mg/kg i.v., qdx5/week for 2 weeks or 10-15 mg/kg i.v., q4dx3), induced complete tumor regression in the majority of animals. In contrast, topotecan (20 mg/kg i.v., q4dx3) or etoposide (30 mg/kg i.v., q5dx5) only slowed the tumor growth rate. These studies show that XR5944 is a highly active novel anticancer agent that is well tolerated at efficacious doses.
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PMID:Antitumor activity of XR5944, a novel and potent topoisomerase poison. 1133 93

Y box-binding protein-1 (YB-1), a member of the DNA binding protein family, interacts with inverted CCAAT boxes (Y-boxes). Y-boxes are located on the promoter of numerous genes, such as DNA topoisomerase IIalpha (Topo IIalpha), proliferating cell nuclear antigen (PCNA) and multidrug resistance 1 (MDR1). In this study, we used immunohistochemical (IHC) staining to detect YB-1 expression in 59 lung cancer tissues and to evaluate whether YB-1 expression was associated with the expression of YB-1 target genes such as Topo IIalpha, PCNA and MDR1 in human lung carcinoma. Twenty-eight out of 59 cases (47.5%) were stained positive for YB-1 in the cytoplasm, while 30 out of 59 cases (50.8%) were positive for PCNA in the nuclei. Topo IIalpha-positive cells were detected in 16 out of 59 cases (27.1%). Eight out of 59 cases (13.6%) had greater than 5% P-gp positive cells expression. There was a significant correlation between the YB-1 and Topo IIalpha expression in small cell lung cancer (SCLC) (p=0.0242). YB-1 expression also correlated with PCNA expression in non-small cell lung cancer (NSCLC) (p=0.0001). Higher levels of YB-1 expression were associated with T3-4 and Stage III-IV tumors in adenocarcinomas (p=0.0072; p=0.0168). In contrast, no relationship was found between YB-1 expression and P-gp expression. Our study suggests that YB-1 expression correlates with Topo IIalpha and PCNA expression in lung cancer.
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PMID:Expression of Y box-binding protein-1 correlates with DNA topoisomerase IIalpha and proliferating cell nuclear antigen expression in lung cancer. 1172 93

XR11576, a novel phenazine, was developed as an inhibitor of both topoisomerase I and II. This study characterized the ability of XR11576 to inhibit both enzymes, and determined its in vitro and in vivo antitumor efficacy against a number of murine and human tumor models. XR11576 was a potent inhibitor of purified topoisomerase I and IIalpha, and exhibited similar potency for both enzymes. The compound stabilized enzyme-DNA cleavable complexes indicating that it acted as a topoisomerase poison. The DNA cleavage patterns obtained with XR11576 were different from those induced by camptothecin and etoposide, which are topoisomerase I and II poisons, respectively. XR11576 demonstrated potent cytotoxic activity against a variety of human and murine tumor cell lines (IC50=6-47 nM). Its activity profile was comparable to or better than that of many widely used anticancer drugs. Moreover, XR11576 was unaffected by multidrug resistance (MDR) mediated by overexpression of either P-glycoprotein or MDR-associated protein, or by down-regulation of topoisomerase II. The latter property supports the dual inhibitory mechanism of action of the compound. XR11576 exhibited a similar pharmacokinetic profile in mice and rats after either i.v. or p.o. administration. In vivo XR11576 showed marked efficacy against a number of tumors including sensitive (H69/P) and multidrug-resistant (H69/LX4) small cell lung cancer and the relatively refractory MC26 and HT29 colon carcinomas following i.v. and p.o. administration. The efficacy of XR11576 was at least comparable to that of TAS-103, originally proposed as a dual inhibitor of topoisomerase I and II. These results suggest that XR11576 is a promising new antitumor agent with oral and i.v. activity, and warrants further development.
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PMID:In vitro and in vivo characterization of XR11576, a novel, orally active, dual inhibitor of topoisomerase I and II. 1191 37

Several studies have shown that extracellular matrix reduces chemotherapeutic drugs-induced apoptosis in small cell lung cancer cells, myelomas and gliomas. We have investigated the protective effect of defined extracellular matrix components and of extracellular matrix from different cell types (fibroblasts, hepatocytes and intestinal epithelial cells) on the toxicity of three types of chemotherapeutic drugs on colon cancer cells. Human colon cancer cell lines LS174T and LiM6 were plated on plastic, on hepatocyte-derived ECM or on stromal ECM and in the presence of the antimetabolite 5-fluorouracil (5-FU). the topoisomerase I inhibitor camptothecin and the topoisomerase II inhibitor etoposide. We determined IC50 for the drugs for each of these culture conditions. We also determined the expression of the anti-apoptotic proteins bcl-2 and bcl-x (L) under these culture conditions. We found that stromal ECM protected LiM6 cells from the toxicity of etoposide and LS174T, but not LiM6 cells, from the toxicity of camptothecin. Collagen 1, fibronectin and fibroblast-derived ECM rendered LiM6 cells, but not LS174T, more sensitive to the harmful effect of 5-FU. Both colon cell lines had increased expression of anti-apoptotic proteins bcl-2 and bcl-x(L) when cultured on the various ECMs and with the drugs, but there was no correlation between a protective ECM effect and expression of the anti-apoptotic proteins. Stromal-derived ECM may protect colon cancer cells from etoposide and camptothecin-induced apotosis, through a mechanism that is not bcl-2 or bcl-x(L) dependant.
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PMID:Stromal extracellular matrix reduces chemotherapy-induced apoptosis in colon cancer cell lines. 1191 83

Topotecan is a topoisomerase-I inhibitor, a drug that stabilizes a covalent complex of enzymes and causes strand cleavage of DNA. 5-Fluorouracil (5FU) is an antimetabolite that interferes with DNA synthesis. Preclinical studies using human cancer cell line models have shown potential therapeutic synergy between these two drugs by showing the maximum cytolytic effect using sequential 5FU followed by topotecan. In the current study, 5FU was used at a fixed dose of 375 mg/m2 given intravenously for five consecutive days on a 28 day cycle. Topotecan was dose-escalated in cohorts of patients from 0.5 to 1.0 mg/m2 given intravenously for 5 days after the 5FU dose. Eleven patients were entered at different dose levels. Both hematological and gastrointestinal toxicity were dose limiting. Diarrhea was the dose-limiting toxicity at the dose of 0.75 mg/m2 of topotecan. Two cases of grade 4 neutropenia were also observed at this dose level. One patient with small cell lung cancer had a complete response, while one patient with metastatic colorectal cancer had a partial remission. Three other patients had stable disease, lasting between 6 and 8 months. Overall, the regimen was well tolerated. A phase II study using a dose of 5FU at 375 mg/m2 followed by topotecan at 0.75 mg/m2 intravenously over 5 days every 28 days is recommended.
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PMID:Phase I study of sequential administration of topotecan and 5-fluorouracil in patients with advanced malignancies. 1219 19

Tirapazamine (TPZ), a hypoxia-selective cytotoxin, has demonstrated activity in cancer clinical trials. Under hypoxic conditions, TPZ is reduced to a radical that leads to DNA double-strand breaks (DSBs), single-strand breaks, and base damage. A previous finding of an association of the DSBs with protein led us to investigate the involvement of topoisomerase II (topo II) in their formation. Nuclear extracts from human lung cancer cells treated with either the topo II poison etoposide or TPZ under hypoxic conditions had markedly reduced topo II activity as judged by an inability to convert kinetoplast DNA from the catenated to the decatenated form. Because topo II poisons, such as etoposide, cause DNA DSBs, we hypothesized that pretreatment of cells with merbarone or aclarubicin, known catalytic inhibitors of topo II, would abrogate DNA DSBs caused by topo II. Cells pretreated with these catalytic inhibitors abrogated both DNA DSBs and cell kill induced by etoposide or by TPZ. Etoposide- and TPZ-mediated DSBs were also greatly reduced in a small cell lung cancer cell line with low levels of nuclear topo IIalpha. We also showed that topo IIalpha becomes covalently bound to DNA after TPZ treatment under hypoxic conditions, and that the cleavable complexes formed by TPZ are more stable over time than those formed by etoposide. Taken together, these data suggest that TPZ exerts its cytotoxic effect at least in part through poisoning topo II. Because TPZ is activated only under hypoxic conditions, which are characteristic of solid tumors, these data implicate TPZ as a tumor-specific topo II poison.
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PMID:Tirapazamine: a hypoxia-activated topoisomerase II poison. 1223 92

Amrubicin (AMR) is a novel, completely synthetic 9-aminoanthracycline derivative. Amrubicinol, the C-13 alcohol metabolite of AMR, inhibits purified human topoisomerase II (topo II). We examined the effect of the combination of cisplatin (CDDP) and amrubicinol in vitro using a small cell lung cancer cell line (SBC-3) and an adenocarcinoma cell line (Ma-1), by WST-1 assay and isobologram analysis. When the two drugs were used together either simultaneously or sequentially, their combined effects were additive. A high concentration of CDDP (300 microM) enhanced the topo II inhibitory activity of amrubicinol as determined by kinetoplast-DNA decatenation assay. On the other hand, amrubicinol increased formation of DNA interstrand cross-links (ICL) in the cells, as determined using ethidium bromide fluorescence binding assay (EBFA), for simultaneous exposure to CDDP (0-300 microM) and amrubicinol (2 microM) compared with CDDP alone. These biological interactions might result in additive interaction between amrubicinol and CDDP.
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PMID:Additive effects of amrubicin with cisplatin on human lung cancer cell lines. 1237 99


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