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)

To improve resolution for physical ordering of adjacent DNA loci, prophase chromosomes were used for multi-color fluorescent in situ hybridization (FISH). The prophase chromosomes were prepared from cultured lymphocytes by a thymidine synchronization, bromodeoxyuridine release technique and then treating the synchronized cultures with topoisomerase II inhibitors ICRF154 or ICRF193. Almost all mitotic figures exhibited highly elongated prophase chromosomes without significant reduction of the mitotic index. Using multi-color FISH with these prophase chromosomes, we were able to distinguish signals for loci separated by as little as 50 kb, and determine their orientation. Furthermore, using this prophase ordering system, we confirmed the linear order and defined the orientation of seven cosmid markers within a 360-kb region surrounding D10S102, a locus that is closely linked to the disease locus in families segregating an allele causing multiple endocrine neoplasia IIA (MEN2A). This prophase FISH system, by rapidly and precisely providing the linear order of loci that are very close, can expedite construction of fine cytogenetic maps and contribute to positional-cloning studies in which the precise ordering of DNA loci in a target region is critical.
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PMID:High resolution ordering of DNA markers by multi-color fluorescent in situ hybridization of prophase chromosomes. 840 66

Phospholipase Cbeta3 (PLCB3) is located to chromosome 11q13 in the vicinity of the multiple endocrine neoplasia type1 (MEN1) gene and shows loss of expression in some neuroendocrine tumors. Transfection of PLCB3 to neuroendocrine cell lines induces growth suppression and phenotypic alterations, but the mechanisms remain unclear. To investigate the underlying events behind this tumor suppression, we performed an RT-Differential cDNA Display of total RNA from BON-1 (human endocrine pancreatic tumor cell line) transfected with PLCB3 and compared to wild type and BON-1 transfected with vector without insert. PLCB3 transfection resulted in increased expression of 4 genes and decreased of 2. The two inhibited were homologous to S100A3 and Chromogranin A. One of the four activated cDNAs could be identified as human mismatch repair protein 3 mRNA (hMSH3), and another was homologous to TIS/MA-3 mRNA (mouse topoisomerase suppressor inhibited gene/mouse apoptosis gene-3). Differential expression of these genes may contribute to the PLCB3-induced tumor suppression of neuroendocrine tumor cell lines.
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PMID:Differentially expressed cDNAs in PLCbeta3-induced tumor suppression in a human endocrine pancreatic tumor cell line: activation of the human mismatch repair protein 3 gene. 1117 84

MEN 10755 is a disaccharide anthracycline endowed with a broader spectrum of antitumour activity than doxorubicin (DOX). To investigate the cellular and molecular basis of its action, cytotoxic activity, drug uptake, subcellular localisation, induction of DNA damage, and apoptosis were assessed in the human A2780 ovarian carcinoma cell line. Experiments with radiolabelled anthracyclines indicated that MEN 10755 exhibited reduced cellular accumulation and a different subcellular distribution (higher cytoplasmic/nuclear ratio) than DOX. In spite of the lower nuclear concentration, MEN 10755 was as potent as DOX in eliciting DNA single- and double-strand breaks, G2/M cell arrest, and apoptosis. Sequencing of drug-induced topoisomerase II cleavage sites showed a common DNA cleavage pattern for MEN 10755 and DOX. Cleavage sites were always characterised by the presence of adenine in -1 position. However, the extent of DNA cleavage stimulation induced by MEN 10755 was greater than that produced by DOX. Reversibility studies showed that MEN 10755-stimulated DNA cleavage sites were more persistent than those induced by DOX, thus suggesting a more stable interaction of the drug in the ternary complex. As a whole, the study indicated that the cellular pharmacokinetics of MEN 10755 substantially differs from that of DOX, showing a lower uptake and a different subcellular disposition. In spite of the apparently unfavourable cellular pharmacokinetics, MEN 10755 was still as potent as DOX in inducing topoisomerase-mediated DNA damage. Although the extent and persistence of protein-associated DNA breaks may contribute to the cytotoxic effects, the drug's efficacy as apoptosis inducer and antitumour agent could not be adequately explained on the basis of DNA damage mediated by the known target (i.e. topoisomerase II), thus supporting additional cellular effects that may be relevant in cellular response.
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PMID:A comparative study of cellular and molecular pharmacology of doxorubicin and MEN 10755, a disaccharide analogue. 1137 97

The crystal structure of the complex formed between the anthracycline antibiotic 3'-deamino-3'- hydroxy-4'-(O-L-daunosaminyl)-4-demethoxydoxo rubicin (MEN 10755), an active disaccharide analogue of doxorubicin, and the DNA hexamer d(CGATCG) has been solved to a resolution of 2.1 A. MEN 10755 exhibits a broad spectrum of antitumor activities, comparable with that of the parent compound, but there are differences in the mechanism of action as it is active in doxorubicin-resistant tumors and is more effective in stimulating topoisomerase DNA cleavage. The structure is similar to previously crystallised anthracycline- DNA complexes. However, two different binding sites arise from drug intercalation so that the two halves of the self-complementary duplex are no longer equivalent. In one site both sugar rings lie in the minor groove. In the other site the second sugar protrudes out from the DNA helix and is linked, through hydrogen bonds, to guanine of a symmetry-related DNA molecule. This is the first structure of an anthracycline-DNA complex where an interaction of the drug with a second DNA helix is observed. We discuss the present findings with respect to the relevance of the amino group for DNA binding and to the potential role played by the second sugar in the interactions with topoisomerases or other cellular targets.
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PMID:The crystal structure of the complex between a disaccharide anthracycline and the DNA hexamer d(CGATCG) reveals two different binding sites involving two DNA duplexes. 1259 54

There has been much recent investigation of the cyclooxygenase (Cox) enzymes in tumor biology, but, to our knowledge, no study has yet been published describing Cox activity in medullary carcinoma of the thyroid (MTC). Nine cases of MTC from the past 10 yr were retrieved from our hospital archives. Slides cut from formalin-fixed paraffin-embedded tumor tissue from these cases were assessed for the activities of Cox-1 and Cox-2 enzymes by immunohistochemistry as well as by a battery of immunohistochemical stains for intermediate filaments, peptide hormone, and proliferation and promoter antigens. The staining reactions were semiquantitatively assessed and scored for comparison with each other as well as with each patient s clinical presentation and course. Staining for Cox-1 and Cox-2 enzymes was present only in tumorous tissue, not in nontumorous thyroid tissue or C-cells. Cox-2 staining was not consistently increased over Cox-1 staining; however, Cox-2 staining bore statistically significant correlations with the expression of low molecular weight keratin, thyroid-transforming factor-1, topoisomerase, and MIB1. Hyperplastic C-cells from patients with diverse physiologic conditions and from three patients with C-cell hyperplasia accompanying medullary carcinoma or multiple endocrine neoplasia type IIa showed no reactivity for the Cox antibodies. It appears that Cox enzyme immunoreactivity is present only in the neoplastic C-cells of medullary carcinoma, but with variable expression. A practical application of the preceding finding might involve the use of Cox staining to distinguish invasive medullary carcinoma cells from hyperplastic C-cells.
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PMID:An immunohistochemical survey of nine cases of medullary carcinoma of thyroid including reactivity for Cox-1 and Cox-2 enzymes. 1266 51

The development of chemoresistance is a major obstacle for successful anticancer therapy. Understanding the molecular mechanisms leading to chemoresistance is a rational step to improve the therapeutic efficacy of cytotoxic drugs. Since anthracyclines play an important role in cancer chemotherapy, we have generated a human ovarian tumor cell line resistant to sabarubicin (MEN 10755), the newest anthracycline molecule in clinical development. Expression of the transporter protein MRP that affected sabarubicin uptake, and a reduced DNA topoisomerase II content in A2780/saba cells was observed. Since the poisoning of DNA topoisomerase II results in DNA damage, which is a critical signal for NF-kappaB activation, we explored if this transcription factor has a role in the chemoresistance to anthracyclines. We showed a reduced NF-kappaB activation in the resistant cell line. Moreover, qualitative changes in NF-kappaB dimer formation between the two cell lines were observed. In agreement with the hypothesis of a role of NF-kappaB in mediating drug resistance, we showed that the pharmacological inhibition of NF-kappaB activation attenuated drug resistance in A2780/saba cells whereas it had no effect in A2780 cells. Altogether, these findings show that anthracycline resistance in A2780 cell lines is due to the coexpression of several molecular mechanisms.
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PMID:NF-kappaB activation contributes to anthracycline resistance pathway in human ovarian carcinoma cell line A2780. 1607 31