Search results for "topoisomerase II"
showing 10 items of 25 documents
Endoreduplication induced in cultured Chinese hamster cells by different anti-topoisomerase II chemicals. Evidence for the essential contribution of …
2004
With the ultimate purpose of testing the hypothesis that, as shown in yeast mutants, any malfunction of DNA topoisomerase II might result in aberrant mitosis due to defective chromosome segregation, we have chosen three chemicals of different nature, recently reported to catalytically inhibit the enzyme. The endpoint selected to assess any negative effect on the ability of topoisomerase II to properly carry out decatenation of fully replicated chromosomes in the G2/M phase of the cell cycle was the presence of metaphases showing diplochromosomes as a result of endoreduplication, i.e. two successive rounds of DNA replication without intervening mitosis. The anti-topoisomerase drugs selected …
Specific phosphorylation of proteins in pore complex-laminae from the sponge Geodia cydonium by the homologous aggregation factor and phorbol ester. …
1987
We have recently shown that the aggregation factor (AF) from the sponge Geodia cydonium stimulates DNA synthesis in quiescent, dissociated cells from the same organism; this event was correlated with the release of the two second messengers: inositol trisphosphate and diacylglycerol. Here we describe that after binding of the AF to the plasma membrane-bound aggregation receptor, a rapid and drastic increase in the incorporation of 32Pi into a series of proteins in the pore complex-lamina fraction occurs. Addition of the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate, to quiescent cells resulted in a similar stimulation of phosphorylation of nuclear proteins. Among them we have selecte…
Topoisomerase II inhibition and high yield of endoreduplication induced by the flavonoids luteolin and quercetin
2006
Luteolin and quercetin are widely distributed plant flavonoids that possess a variety of chemical and biological activities, including free-radical scavenging and antioxidant activity. Recently, both flavonoids have been reported to inhibit DNA topoisomerases I and II (topo I and topo II), a property that, together with their ability to induce DNA and chromosome damage, has made them candidate anticancer compounds. In the present study, we confirmed that both compounds are topo II inhibitors by conducting a comparative study of their effect on topo II activity from Chinese hamster ovary AA8 cells. Because interference with the function of topo II to resolve DNA entanglement at the end of re…
Photochemical electrocyclisation of 3-vinylindoles to pyrido[2,3-a]-, pyrido[4,3-a]- and thieno[2,3-a]-carbazoles: Design, synthesis, DNA binding and…
2009
In the context of the design and synthesis of DNA ligands, some new hetarene annelated carbazoles were synthesized. As lead structure the intercalating tetracyclic systems pyrido[2,3-a]- and pyrido[4,3-a]-carbazoles and in one case a thieno[2,3-a]-carbazole were taken into account. A dialkyl amino amidic chain was introduced to the planar chromophoric system with the intent to generate minor groove binding properties. The cytotoxicity of some compounds was examined by the NCI antitumor screening. Furthermore, biophysical as well as biochemical studies were performed in order to get some information about the DNA-binding properties and inhibition of DNA related functional enzymes of this new…
[Apoptosis of human leukemic cells induced by topoisomerase I and II inhibitors].
1996
International audience; Comparison between five human leukemic lines (BV173, HL60, U937, K562, KCL22) suggest that the main determinant of their sensitivity to topoisomerase I (camptothecin) and II (VP-16) inhibitors is their ability to regulate cell cycle progression in response to specific DNA damage, then to die through apoptosis: the more the cells inhibit cell cycle progression, the less sensitive they are. The final pathway of apoptosis induction involves a cytoplasmic signal, active at neutral pH, needing magnesium, sensitive to various protease inhibitors and activated directly by staurosporine. Modulators of intracellular signaling (calcium chelators, calmodulin inhibitors, PKC mod…
Rac1 GTPase, a multifunctional player in the regulation of genotoxic stress response
2013
The Ras-related C3 botulinum toxin substrate 1 (Rac1) belongs to the Ras-homologous (Rho) family of small GTPases, which transduce signals from the outside to the inside of a cell. Rac1 becomes activated upon ligand binding of a variety of receptors, including receptor tyrosine kinases and heterotrimeric G-protein-coupled receptors. After GTP loading by guanine exchange factors (GEFs), GTP-bound Rac1 engages numerous effector proteins, thereby eventually regulating cell motility and adhesion, cell cycle progression through G1, mitosis and meiosis, as well as cell death and metastasis.1 Besides, Rac1 adjusts cellular responses to genotoxic agents, such as UV light and alkylating agents, by r…
3,5-bis(3'-indolyl)pyrazoles, analogues of marine alkaloid nortopsentin: synthesis and antitumor properties.
2007
A series of 10 bis-indolylpyrazoles of type 9, 10 were obtained by cyclization of diketones 8 using hydrazine monohydrate or methylhydrazine in refluxing acetic acid/THF. Derivatives 9a,c,d were selected, by the National Cancer Institute (NCI, Bethesda, USA), to be evaluated against the full panel of about 60 human tumor cell lines derived from nine human cancer cell types and showed antiproliferative activity in the micromolar range. In particular, 9d, the most active compound was effective against all the tested cell lines with a GI(50) mean value of 3.23 microM; TGI and LC(50) values were 14.5 and 58.9 microM having positive response on 91% and 41% of the tested cell lines, respectively.
Nalidixic acid-resistant V79 cells with reduced DNA topoisomerase II activity and amplification prone phenotype
1992
Spontaneously nalidixic acid-resistant lines (NAr lines) were selected from a V79 Chinese hamster cell line and phenotypically characterized. NAr lines showed an increased doubling time, a higher number of spontaneous SCE, and more interestingly, decreased DNA topoisomerase II activity. These lines were also cross-resistant to the eukaryotic topoisomerase II inhibitors etoposide and adriamycin, but showed the same level of sensitivity as the parental line to the DNA topoisomerase I inhibitor camptothecin. NAr lines were cross-resistant to other drugs, such as PALA, MTX and MPA, resistance to which has been shown to arise by amplification of the target genes. This last feature, together with…
Biochemical approaches to characterize targets responsible for acrylamide-induced inhibition of topoisomerase II
2006
Vinyl monomer acrylamide (AA), generally used in numerous industrial applications, has been classified by the International Agency for Research on Cancer (IARC) as “probably carcinogenic to humans” (group 2A), but the molecular mechanism underlying its genotoxicity has not fully known. Previously, we observed that Acrylamide (AA) was able to antagonize in vivo the citotoxicity of well know poison etoposide suggesting that topoisomerase II (Topo II) activity was affected by AA. In the current studies we investigated the inhibitory activity of acrylamide toward topoisomerase II by performing tests in vitro.
In vivo and in vitro inhibitory effects of acrylamide on DNA topoisomerase II
2006
Acrylamide (AA), a chemical produced in several foodstuffs when cooked at a high temperature, is considered a probable human carcinogen, but the molecular mechanism underlying its genotoxicity has not fully known. Numerous authors have reported the induction by AA of DNA double strand breaks and sister chromatid exchange (SCE); we here confirmed the acrylamide capability of damaging DNA by utilizing Comet assay, which showed a dose-dependent increase of tail lenght, in metabolically non competent V79 Chinese hamster cells. Moreover, we observed that Acrylamide (AA) was able to antagonize in vivo the citotoxicity of well know poison etoposide; this suggested that topoisomerase II activity wa…