Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:5.99.1.3 (topoisomerase)
9,911 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

New drug development requires simple in vitro models that resemble the in vivo situation more in order to select active drugs against solid tumours and to decrease the use of experimental animals. In this paper, we review the characteristics and scope of a relatively simple cell-culture system with a three-dimensional organisation pattern - the multilayered postconfluent cell culture model. Solid tumour cell lines from diverse origins when grown in V-bottomed microtiter plates reach confluence in 3-5 days and then start to form multilayers. The initial exponential growth of the culture is followed by a plateau phase when cells reach confluence. This produces changes in the morphology of the cells. For some cell lines, it is possible to observe cell differentiation. A substantial advantage of the system is the use of the sulforodamine B (SRB) assay to determine relative cell growth or viability, which allows semiautomation of the experiments. Several experiments were performed to assess the differences and similarities between cells cultured as monolayers and multilayers, and eventually, compared with the results for solid tumours and some other models such as spheroids. Cell-cycle analysis for multilayers showed a lower S-phase arrest, which is accompanied by a decrease in the expression of cell-cycle-related proteins and a decrease in cellular nucleotide pools. Gene and protein expression of topoisomerase I, topoisomerase II and thymidylate synthase expression were lower for multilayers, but no substantial changes were observed for the expression of DT-diaphorase. P53 expression increased. Multilayer cultures present distinctive properties for drug transport across the membrane, drug accumulation and retention. In fact, the transport of antifolates across the membrane, accumulation of topotecan and gemcitabine-triphosphate are reduced in multilayers when compared with monolayers, which may be related to a decrease in drug penetration to the inner regions of the multilayers. Alteration of these pharmacodynamic parameters is directly related to a decrease in drug activity. The most powerful application of multilayers is in the assessment of cytotoxicity. Solid tumour cell lines from different origins have been treated with several conventional and investigational anticancer drugs. The data show that multilayers are more resistant to the drugs than the corresponding monolayers, but there are substantial differences between the drugs depending on culture conditions, e.g. the difference was rather small for a drug such as cisplatin, miltefosine and EO9, a drug, which is activated under hypoxic conditions. Gemcitabine was active against ovarian cancer but not against colon cancer, resembling the in vivo situation. This observation was not evident with monolayer experiments. Another interesting application is the possibility to perform drug combination studies. The combination of gemcitabine and cisplatin proved to produce selective cell kill in H322 cells (non-small cell lung cancer cell line). Neither of the drugs was independently able to produce similar effects. In summary, multilayer cultures are relatively simple three-dimensional systems to study the effect of microenvironmental conditions on anticancer drug activity. The model might serve as a base for a more rigorous secondary in vitro screening.
...
PMID:The multilayered postconfluent cell culture as a model for drug screening. 1103 3

KILLER/DR5 is a death-domain-containing proapoptotic receptor that binds to the cytotoxic ligand TRAIL. It was originally reported that induction of KILLER/DR5 mRNA following DNA damage was p53-dependent, but some drugs that induce apoptosis can upregulate KILLER/DR5 mRNA expression in cell lines with mutated p53. We further extend those findings by classifying the capability of various apoptosis-inducing drugs to increase the expression of KILLER/DR5 mRNA in a p53-independent manner. beta-Lapachone, a topoisomerase inhibitor, increased KILLER/DR5 mRNA in colon cancer cell lines with wild-type p53 but not with mutant p53. In contrast, betulinic acid, a novel chemotherapeutic compound, induced apoptosis and KILLER/DR5 mRNA in melanoma and glioblastoma cells through a p53-independent mechanism. The synthetic glucocorticoid dexamethasone elevated KILLER/DR5 mRNA in glioblastoma, ovarian cancer, and colon cancer cell lines with mutant p53 undergoing apoptosis, and this induction was inhibited by the transcriptional inhibitor actinomycin D. Although another glucocorticoid, prednisolone, also induced apoptosis, it did not increase KILLER/DR5 mRNA. Finally, the cytokine interferon-gamma (IFN-gamma) induced apoptosis and KILLER/DR5 in cell lines with mutant p53, and the induction of KILLER/DR5 mRNA by IFN-gamma was delayed in cells lacking wild-type STAT1, a transcription factor implicated in IFN-gamma signaling. Similarly, the induction of KILLER/DR5 mRNA by the cytokine TNF-alpha was also delayed in cell lines with mutated STAT1. These findings suggest that KILLER/DR5 may play a role in p53-independent apoptosis induced by specific drugs and warrants further investigation as a novel target for chemotherapy of tumors lacking wild-type p53.
...
PMID:p53-independent upregulation of KILLER/DR5 TRAIL receptor expression by glucocorticoids and interferon-gamma. 1113 40

DNA topoisomerases I and II are essential for cell survival and play critical roles in DNA metabolism and structure. Inhibitors of topoisomerase constitute a novel family of antitumor agents with demonstrated clinical activity in human malignancies. The clinical use of these agents is limited due to severe toxic effects on normal cells. Therefore, there is a need to develop novel, nontoxic topoisomerase inhibitors that have the ability to spare normal cells. Recent studies have shown that green tea and its major polyphenolic constituent, epigallocatechin-3-gallate (EGCG), impart growth inhibitory responses to cancer cells but not to normal cells. Based on the knowledge that EGCG induces DNA damage, cell cycle arrest, and apoptosis, we considered the possibility of the involvement of topoisomerase in the antiproliferative response of EGCG. Here, for the first time, we show that EGCG inhibits topoisomerase I, but not topoisomerase II in several human colon carcinoma cell lines. Based on this study it is tempting to suggest that combination of EGCG with other conventional topoisomerase inhibitors could be an improved strategy for treatment of colon cancer. The possible role of EGCG as a chemotherapeutic agent needs to be investigated.
...
PMID:Green tea constituent (--)-epigallocatechin-3-gallate inhibits topoisomerase I activity in human colon carcinoma cells. 1159 58

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.
...
PMID:Stromal extracellular matrix reduces chemotherapy-induced apoptosis in colon cancer cell lines. 1191 83

Numerous studies demonstrate that the chemopreventive effect of non-steroidal anti-inflammatory drugs on colon cancer is mediated through inhibition of cell growth and induction of apoptosis. For these effects non-steroidal anti-inflammatory drugs have been recently employed as sensitising agents in chemotherapy. We have shown previously that treatments with aspirin and NS-398, a cyclo-oxygenase-2 selective inhibitor, affect proliferation, differentiation and apoptosis of the human colon adenocarcinoma Caco-2 cells. In the present study, we have evaluated the effects of aspirin and NS-398 non-steroidal anti-inflammatory drugs on sensitivity of Caco-2 cells to irinotecan (CPT 11) and etoposide (Vp-16) topoisomerase poisons. We find that aspirin co-treatment is able to prevent anticancer drug-induced toxicity, whereas NS-398 co-treatment poorly affects anticancer drug-induced apoptosis. These effects correlate with the different ability of aspirin and NS-398 to interfere with cell cycle during anticancer drug co-treatment. Furthermore, aspirin treatment is associated with an increase in bcl-2 expression, which persists in the presence of the anticancer drugs. Our data indicate that aspirin, but not NS-398, determines a cell cycle arrest associated with death suppression. This provides a plausible mechanism for the inhibition of apoptosis and increase in survival observed in anticancer drug and aspirin co-treatment.
...
PMID:Effect of non-steroidal anti-inflammatory drugs on colon carcinoma Caco-2 cell responsiveness to topoisomerase inhibitor drugs. 1198 87

12,13-Dihydro-5-[2-(dimethylamino)ethyl]-4H-benzo[c] pyrimido[5,6,1-jk] carbazole-4,6,10(5H,11H)-trione hydrochloride (ER-37328) is a novel topoisomerase II poison with potent tumoricidal activity against solid tumor cells both in vitro and in vivo. Here, we describe studies on the effects of ER-37328 on the primary tumor, liver metastasis, and survival in a murine Colon 38 orthotopic transplantation model. When ER-37328 (10 mg/kg) was administered i.v. at 11 days or 20 days after transplantation, strong regression of the primary tumor was observed on both administration schedules. On the later schedule, ER-37328 completely blocked liver metastasis, whereas the mean number of metastases in the control group was 23.9. To examine the antitumor activity against Colon 38 at the liver in more detail, ER-37328 was administered to mice that had received an inoculation of Colon 38 tumor into the liver. ER-37328 showed strong tumor-regression activity against Colon 38 growing in the liver. In addition, administration of ER-37328 on a schedule of every 7 days four times caused a significant increase of 79% in life span in the orthotopic transplantation model, calculated by using mean survival times. Pharmacokinetic study revealed that ER-37328 was highly distributed to the tumor and organs. The ratios of the area under the concentration-time curves of ER-37328 in the tumor, lung, liver, and kidney versus plasma were 81, 77, 47, and 40, respectively. This high distribution to the tumor and liver may explain the potent antitumor activity of ER-37328 against Colon 38 tumor in the liver. In conclusion, the topoisomerase II poison ER-37328 is a promising candidate for clinical application against colon cancer.
...
PMID:Effects of ER-37328 on primary tumor, liver metastasis, and life span in a murine colon 38 orthotopic transplantation model. 1253 73

In addition to its action as a topoisomerase II poison, mitoxantrone is activated by formaldehyde to bind DNA, forming DNA-adducts specifically at 5'CpG and CpA sequences, with an enhancement of adducts at methylated CpG sites. The butyric acid prodrug, AN-9 (pivaloyloxymethyl butyrate), releases formaldehyde upon cellular hydrolysis and our previous studies have shown that mitoxantrone acts synergistically with AN-9 in cytotoxicity assays. In this paper, we investigated the impact of methylation levels in the cell on mitoxantrone-induced cytotoxicity using the colon cancer cell line HCT116 and its derived DNA methyltransferase (DNMT) 1 and DNMT 3a knockout (DKO8) cell line. We found that decreased methylation levels in the DNMT-null cells led to at least a 2-fold reduction in mitoxantrone-induced cytotoxicity. Next, we studied the impact of mitox-antrone alone, and in combination with AN-9, on hypermethylated genes and their mRNA expression in breast cancer cells. Using methylation-specific PCR and RT-PCR, we found that mitoxantrone treatment of breast cancer cell lines resulted in demethylation of the 14.3.3s, Cyclin D2 and ERa genes, followed by re-expression of their mRNA. The effect of mitoxantrone on re-expression of key genes involved in cell cycle regulation, and ensuing death of the cells may be an additional, previously undiscovered mechanism of action of mitoxantrone.
...
PMID:Mitoxantrone mediates demethylation and reexpression of cyclin d2, estrogen receptor and 14.3.3sigma in breast cancer cells. 1287 62

A series of benz[f]indole-4,9-diones, based on the antitumor activity of 1,4-naphthoquinone, were synthesized and evaluated for their cytotoxic activity in cultured human cancer cell lines A549 (lung cancer), Col2 (colon cancer), and SNU-638 (stomach cancer), and also for the inhibition of human DNA topoisomerases I and II activity in vitro. Several compounds including 2-amino-3-ethoxycarbonyl-N-methyl-benz[f]indole-4,9-dione showed a potential cytotoxic activity judged by IC50<20.0 microg/ml in the panel of cancer cell lines. Especially, 2-hydroxy-3-ethoxycarbonyl-N-(3,4-dimethylphenyl)-benz[f]indole-4,9-dione had potential selective cytotoxicity against lung cancer cells (IC50=0.4 microg/ml)) compared to colon (IC50>20.0 microg/ml) and stomach (IC50>20.0 microg/ml) cancer cells. To further investigate the cytotoxic mechanism, the effects of test compounds on DNA topoisomerase I and II activities were used. In a topoisomerase I-mediated relaxation assay using human placenta DNA topoisomerase I and supercoiled pHOTI plasmid DNA, 2-amino-3-ethoxycarbonyl-N-(4-fluorophenyl)-benz[f]indole-4,9-dione had the most potent inhibitory activity among the compounds tested. However, most of the compounds showed only weak inhibition of the DNA topoisomerase II-mediated KDNA (Kinetoplast DNA) decatenation assay, except for 2-amino-3-ethoxycarbonyl-N-(4-methylphenyl)-benz[f]indole-4,9-dione and 2-amino-3-ethoxycarbonyl-N-(2-bromoehtyl)-benz[f]indole-4,9-dione with a moderate inhibitory activity. These results suggest that several active compounds had relatively selective inhibitory activity against toposiomearse I compared to toposiomerase II. No obvious correlation was observed between the cytotoxicity of the individual compound and the inhibitory activity of DNA relaxation and decatenation by topoisomerase I and II, respectively, in vitro.
...
PMID:Cytotoxicity and DNA topoisomerase inhibitory activity of benz[f]indole-4,9-dione analogs. 1451 80

Daylilies (Hemerocallis) are used medicinally in eastern Asia and extracts of the plant had been shown to inhibit cell proliferation and induce cancer cells to undergo differentiation. In our studies of the constituents of Hemerocallis fulva var. 'Kwanzo' roots, we isolated a series of new [kwanzoquinones A (1), B (2), C (4), D (5), E (6), F (7), G (9)] and known [2-hydroxychrysophanol (3) and rhein (8)] anthraquinones. These compounds were tested in order to determine their potential roles as cancer cell growth inhibitors. Kwanzoquinones A-C and E, kwanzoquinone A and B monoacetates (1a and 2a), 2-hydroxychrysophanol, and rhein inhibited the proliferation of human breast, CNS, colon, and lung cancer cells with GI50 values between 1.8 to 21.1 microg/mL. However, upon exposure of the cancer cells to the GI50 concentrations of the bioactive anthraquinones, most of the cancer cell lines exhibited higher than anticipated levels of cell viability. Co-incubation of the anthraquinones with vitamins C and E increased the viability of breast cancer cells. In contrast, vitamins C and E potentiated the cytotoxic effects of the anthraquinones against the colon cancer cells. None of the anthraquinones inhibited the activity of topoisomerase.
...
PMID:Inhibition of human tumor cell proliferation by novel anthraquinones from daylilies. 1474 36

Solid tumors with disorganized, insufficient blood supply contain hypoxic cells that are resistant to radiotherapy and chemotherapy. Drug resistance, an obstacle to curative treatment of solid tumors, can occur via suppression of apoptosis, a process controlled by pro- and antiapoptotic members of the Bcl-2 protein family. Oxygen deprivation of human colon cancer cells in vitro provoked decreased mRNA and protein levels of proapoptotic Bid and Bad. Hypoxia-inducible factor 1 (HIF-1) was dispensable for the down-regulation of Bad but required for that of Bid, consistent with the binding of HIF-1alpha to a hypoxia-responsive element (positions -8484 to -8475) in the bid promoter. Oxygen deprivation resulted in proteosome-independent decreased expression of Bax in vitro, consistent with a reduction in global translation efficiency. The physiological relevance of Bid and Bax down-regulation was confirmed in tumors in vivo. Oxygen deprivation resulted in decreased drug-induced apoptosis and clonogenic resistance to agents with different mechanisms of action. The contribution of Bid and/or Bax down-regulation to drug responsiveness was demonstrated by the relative resistance of normoxic cells that had no or reduced expression of Bid and/or Bax and by the finding that forced expression of Bid in hypoxic cells resulted in increased sensitivity to the topoisomerase II inhibitor etoposide.
...
PMID:Hypoxia-mediated down-regulation of Bid and Bax in tumors occurs via hypoxia-inducible factor 1-dependent and -independent mechanisms and contributes to drug resistance. 1502 76


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---