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

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Query: EC:5.99.1.2 (topoisomerase)
9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Combined modalities are currently used for cancer therapy, although their mechanisms of activity remain incompletely deciphered. The design of new drug combinations suffers from our inability to anticipate accurately their efficacy or toxicity. They can be evaluated in vivo, using human tumors grafted into immunodeficient mice, as we did here with combined protocols used in the clinical setting. Xenografts of small cell lung carcinoma (SCLC) from eight patients were used to test the tumor sensitivity to etoposide (VP16; 12-16 mg/kg/days, days 1, 2, and 3), cisplatin (CDDP; 6-9 mg/kg/day, day 1) and ifosfamide (IFO; 90-210 mg/kg/day, days 1, 2, and 3) as single agents and to evaluate the efficacy of the two-drug or three-drug combinations. Five xenografts came from untreated patients (SCLC-61, SCLC-6, SCLC-10, SCLC-41, and SCLC-96) and three after treatment (SCLC-74, SCLC-101, and SCLC-108). p53 was inactivated in all of them. Tumor growth inhibition, growth delay, and the survival rate of tumor-bearing mice reflected individual SCLC chemosensitivity. As single agents, IFO inhibited tumor growth in a dose-dependent manner, whereas CDDP and VP16 had little or no effect. Both CDDP and IFO potentiated VP16, inducing complete regressions in the most sensitive SCLCs; VP16-IFO was more effective than VP16-CDDP, with complete regressions in six versus three of the eight tumors tested, respectively. CDDP-IFO was less effective than VP16-IFO, with three of eight SCLCs giving complete regressions. The three-drug combination led to modest improvement over the best two-drug combination but only for sensitive SCLCs. Because drug-responses distinguished two classes of SCLCs, as sensitive or refractory, MDR1, glutathione S-transferase pi, lung-related multidrug resistance protein, multidrug resistance protein, and topoisomerase IIalpha mRNA expression was studied by semiquantitative reverse transcription. There was no correlation with SCLC sensitivity; topoisomerase IIalpha and multidrug resistance protein was expressed in all cases, lung-related multidrug resistance protein and glutathione S-transferase pie in seven of eight, and MDR1 gene in four of eight. In conclusion, these SCLC xenografts displayed a pattern of chemotherapy response close to that observed in patients. This model confirmed that in two-drug combinations, each component potentiated the effects of the other, with VP16-IFO tending to be the best two-drug combination, both of which were more effective than VP16-CDDP and better tolerated than CDDP-IFO. The addition of a third agent gave a modest, if any, therapeutic benefit in the responders but none in refractory SCLCs. There was no correlation between the extent of response and resistance markers.
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PMID:Distinctive potentiating effects of cisplatin and/or ifosfamide combined with etoposide in human small cell lung carcinoma xenografts. 1081 35

KAI1 is a metastasis suppressor gene which is capable of inhibiting the processes of tumor metastasis without affecting tumorigenicity per se. We found that etoposide, a topoisomerase II inhibitor, is able to activate the expression of the KAI1 gene in a dose-dependent manner in human prostate cancer cell lines, ALVA, DU145, and PC-3 as well as in human lung carcinoma cell A549. The activation of the KAI1 gene was mainly mediated by the c-Jun gene in the PC-3 and DU145 cell lines, while it was mediated by both p53 and c-Jun genes in the A549 cell line. These results suggest that the augmentation of the KAI1 gene expression is independently controlled by p53 and c-Jun at the transcriptional level in the human cancer cell lines. Furthermore, treatment of these cell lines with etoposide resulted in significant reduction of cellular invasion measured by the Matrigel invasion chamber. Because etoposide has been shown to be effective on advanced prostate cancer when used in combination with other regimens, our results provide further rationale to use this drug as an antimetastatic agent.
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PMID:Activation of the tumor metastasis suppressor gene, KAI1, by etoposide is mediated by p53 and c-Jun genes. 1091 45

Quantitative structure-activity relationships have been formulated for two sets of DNA binding topoisomerase agents (bis-acridines and bis-phenazines) acting on murine P388 leukemia cells, murine Lewis lung carcinoma (LL(C)) cells and human Jurkat leukemia wild-type (JL(C)) cells. For the acridines, all three QSARs (1-3) show only a (small negative) hydrophobic effect. In sharp contrast, the phenazines in all three studies (4-6) show a strong hydrophobic effect, with the optimum ClogP being near 7.3 for all examples. This suggests that, despite the structural similarity of the compounds, different modes of enzyme and/or DNA binding may be involved.
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PMID:Comparative QSAR studies on substituted bis-(acridines) and bis-(phenazines)-carboxamides: a new class of anticancer agents. 1097 32

Deoxynybomycin was identified as an inducer of p21the/WAF1 gene following screening using a reporter, p21/luciferase. The present study examined its anti-proliferative effect on human tumor cell lines. Deoxynybomycin selectively inhibited growth of human osteoblastic sarcoma Saos-2, gastric cancer TMK-1, and monocytic leukemia THP-1 cells, but did not affect survival of normal human fibroblasts at doses up to 5 microg/ml. Results from an assay system using a panel of 39 human cancer cell lines indicated that deoxynybomycin has selective cytotoxic activity against lung carcinoma cell lines. Deoxynybomycin induced apoptosis in Saos-2, TMK-1, and THP-1 cells as revealed by DNA fragmentation and TUNEL assays. It inhibited topoisomerase I but not topoisomerase II. These results suggest that deoxynybomycin may be useful in cancer chemotherapy.
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PMID:Deoxynybomycin is a selective anti-tumor agent inducing apoptosis and inhibiting topoisomerase I. 1099

The lignan family of natural products includes compounds with important antineoplastic and antiviral properties such as podophyllotoxin and two of their semisynthetic derivatives, etoposide and teniposide. The latter are included in a wide variety of cancer chemotherapy protocols. Due to these biological activities, lignans, and especially cyclolignans, have been the objective of numerous studies focused to prepare better and safer anticancer drugs. The mechanism by which podophyllotoxin blocks cell division is related to its inhibition of microtubule assembly in the mitotic apparatus. However, etoposide and teniposide were shown not to be inhibitors of microtubule assembly which suggested that their antitumor properties were due to another mechanism of action, via their interaction with DNA and inhibition of DNA topoisomerase II. Other podophyllotoxin derivatives has also been reported which retained or even improved the cytotoxic activity, but these were weak inhibitors of topoisomerase II in vitro; the data revealed that such analogs exhibit a different, as yet unknown, mechanism of action. The main deficiency of these compounds is their cytotoxicity for normal cells and hence side effects derived from their lack of selectivity against tumoral cells. In this regard it is necessary to investigate and prepare new more potent and less toxic analogs, that is, with better therapeutic indices. It is well accepted from structure-activity studies in this field that the trans-lactones are more potent as antineoplastics than the cis-lactones. Not only the configuration of the D ring is an important factor for high cytotoxic activity, but also a quasi-axial arrangement of the E ring is necessary. On this basis, studies on lignans have been addressed to modify the lactone moiety and prepare analogs with heteroatoms at different positions of the cyclolignan skeleton. Our group has been working during the last few years on chemical transformations of podophyllotoxin and analogs and we have prepared a large number of cyclolignan derivatives some of which display potent antiviral, immunosuppressive and cytotoxic activities. We have reported several new cytotoxic agents with nitrogen atoms at C-7 or C-9 or at both C-7 and C-9: imine derivatives, oxime derivatives, pyrazoline-, pyrazo- and isoxazoline-fused cyclolignans. At present, we are preparing mainly new compounds by modifications of the A and E cyclolignan-rings. They are being tested on cultures of different tumoral cell lines (P-388 murine leukemia, A-549 human lung carcinoma, HT-29 human colon carcinoma and MEL-28 human melanoma) and some of them have shown an interesting and selective cytotoxicity.
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PMID:Antitumor properties of podophyllotoxin and related compounds. 1110 64

Activation of signaling pathways after DNA damage induced by topoisomerase (topo) poisons can lead to cell death by apoptosis. Treatment of human nonsmall cell lung carcinoma (NSCLC-3 or NSCLC-5) cells with the topo I poison SN-38 or the topo II poison etoposide (VP-16) leads to activation of NF-kappaB before induction of apoptosis. Inhibiting the degradation of IkappaBalpha by pretreatment with the proteasome inhibitor MG-132 significantly inhibited NF-kappaB activation and apoptosis but not DNA damage induced by SN-38 or VP-16. Transfection of NSCLC-3 or NSCLC-5 cells with dominant negative mutant IkappaBalpha (mIkappaBalpha) inhibited SN-38 or VP-16 induced transcription and DNA binding activity of NF-kappaB without altering drug-induced apoptosis. Regulation of apoptosis by mitochondrial release of cytochrome c and activation of pro-caspase 9 followed by cleavage of poly(ADP-ribose) polymerase by effector caspases 3 and 7 was similar in neo and mIkappaBalpha cells treated with SN-38 or VP-16. In contrast to pretreatment with MG-132, exposure to MG-132 after SN-38 or VP-16 treatment of neo or mIkappaBalpha cells decreased cell cycle arrest in the S/G2 + M fraction and enhanced apoptosis compared with drug alone. In summary, apoptosis induced by topoisomerase poisons in NSCLC cells is not mediated by NF-kappaB but can be manipulated by proteasome inhibitors.
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PMID:Roles of NF-kappaB and 26 S proteasome in apoptotic cell death induced by topoisomerase I and II poisons in human nonsmall cell lung carcinoma. 1111 10

We have previously reported that the antibiotic novobiocin enhanced the toxicity of the anticancer agent etoposide (VP-16) to several drug-sensitive and -resistant tumor cell lines. The increase in VP-16 cytotoxicity produced by novobiocin was not due to the combined effects of these agents on topoisomerase II, but to inhibition by novobiocin of VP-16 efflux, which in turn led to increased accumulation of VP-16 and increased formation of potentially lethal VP-16-stabilized topoisomerase II-DNA covalent complexes. We have now identified novobiocin analogs that are essentially equivalent to novobiocin as inhibitors of the activity of topoisomerase II, but that are more potent than novobiocin (a) as modulators of the cytotoxicity of VP-16 to WEHI-3B leukemia and A549 lung carcinoma cells and (b) in increasing VP-16 accumulation in these cell lines. Thus, removal of the sugar moiety of novobiocin to form novobiocic acid enhanced the potency of the antibiotic as a modulator of VP-16, whereas the substituted coumarin ring alone (U-7587) was devoid of VP-16 modulatory activity. Modifications of the side chain of novobiocin significantly influenced modulatory activity, with cyclonovobiocic acid, which was formed from novobiocic acid by acid-catalyzed cycloaddition, being the most active in enhancing the cytotoxicity of VP-16. The increased potency of novobiocic acid and cyclonovobiocic acid as modulators of VP-16 activity was achieved with no change from novobiocin in the capacity of these analogs to inhibit the catalytic activity of mammalian topoisomerase II, indicating a change in the specificity of these analogs.
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PMID:Structure-activity studies of novobiocin analogs as modulators of the cytotoxicity of etoposide (VP-16). 1121 69

We have recently identified a novel CCAAT box binding protein (ICBP90) involved in the regulation of topoisomerase IIalpha gene expression. We have observed that it is expressed in non-tumoral proliferating human lung fibroblast cells whereas in HeLa cells, a tumoral cell line, ICBP90 was still present even when cells were at confluence. In the present study, we have determined the ICBP90 gene structure by screening of a human placenta genomic library and PCR analysis. We report that the ICBP90 gene spans about 35.8 kb and contains six coding exons named A to F. In the 5' upstream sequence of the region containing the coding exons, two additional exons (I and II) were found. Additionally, an internal splicing site was found in exon A. A promoter region, including three putative Sp1 binding sites between exons I and A, was identified by transient transfection. Northern blot analysis of several cancer cell lines revealed the existence of two ICBP90 mRNA species of 5.1 and 4.3 kb that are transcribed from the gene. The relative amounts of these mRNAs depended on the cell type. In MOLT-4 cells and Burkitt's lymphoma Raji cells, the 4.3 kb or the 5.1 kb transcripts were mainly observed, respectively. In other cell lines, such as HL-60 cells, chronic myelogenous leukaemia K-562, lung carcinoma A549, HeLa or colorectal SW480, both 4.3 and 5.1 kb forms of ICBP90 mRNA could be detected. Interestingly, western blot analysis showed several ICBP90 protein bands in HeLa but only a single band in MOLT-4 cell extracts. Taken together our results are consistent with the ICBP90 gene exhibiting alternative splicing and promoter usage in a cell-specific manner.
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PMID:Genomic structure and chromosomal mapping of the gene coding for ICBP90, a protein involved in the regulation of the topoisomerase IIalpha gene expression. 1129 Apr 15

Bis(9-methylphenazine-1-carboxamides) joined by a variety of dicationic (CH(2))(n)()NR(CH(2))(m)NR(CH(2))(n) linkers of varying length (carboxamide N-N distances from 11.0 to 18.4 A) and rigidity were prepared by reaction of 9-methylphenazine-1-carboxylic acid imidazolide with the appropriate polyamines. The compounds were evaluated for growth inhibitory properties in P388 leukemia, Lewis lung carcinoma, and wild-type (JL(C)) and mutant (JL(A) and JL(D)) forms of human Jurkat leukemia with low levels of topoisomerase II (topo II). The compounds all had IC(50) ratios of <1 in the resistant Jurkat lines, consistent with topo II inhibition not being the primary mechanism of action. Analogues joined by an (CH(2))(2)NR(CH(2))(2)NR(CH(2))(2) linker were extremely potent cytotoxins, with selectivity toward the human cell lines, but absolute potencies declined sharply from R = H through R = Me to R = Pr and Bu. In contrast, (CH(2))(2)NR(CH(2))(3)NR(CH(2))(2) compounds showed reverse effects, with the R = Me analogue being more potent than the R = H one as well as being the most potent in the series [IC(50) in JL(C) cells 0.08 nM; superior to that for the clinical bis(naphthalimide) LU 79553]. Overall, the IC(50)s of analogues with linker chains (CH(2))(n)NH(CH(2))(m)NH(CH(2))(n) were inversely proportional to linker length. Constraining the rigidity of the linker chain by incorporating a piperazine ring did not decrease potency significantly. A representative compound bound tightly to DNA with high selectivity for GC sites, compatible with recent work suggesting that compounds of this type place their side chains in the major groove, making specific contacts with guanine bases. Representative compounds were susceptible to transport mediated resistance, being much less effective in cells that overexpressed P-glycoprotein. Overall the results suggest these compounds have a similar mode of action, mediated primarily by poisoning of topo I (possibly with some involvement of topo II). The bis(9-methylphenazine-1-carboxamides) show very high in vitro growth inhibitory potencies compared to their monomeric analogues. Two compounds showed in vivo activity in murine colon 38 syngeneic and HT29 human colon tumor xenograft models using intraperitoneal dosing.
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PMID:Dicationic bis(9-methylphenazine-1-carboxamides): relationships between biological activity and linker chain structure for a series of potent topoisomerase targeted anticancer drugs. 1131 Oct 63

Resistance to chemotherapy is common in non-small cell lung cancer. The aim of this study was to investigate the prognostic impact of in vitro established drug resistance markers on the response to chemotherapy in patients with advanced non-small cell lung cancer. Samples of 38 patients were analyzed by immunohistochemical staining, for topoisomerase IIalpha and IIbeta, Ki-67, MRP and LRP. In addition, mutation analysis of the topoisomerase IIalpha gene, the B/DNBS and the Tyr804 region, was performed. Lung tumor biopsies were taken prior for treatment with one of the following regimens; cisplatin/paclitaxel, cisplatin/VM26 or VP16, or carboplatin/VP16/ifosfamide. Seventeen patients obtained a partial response, 12 had stable disease and nine patients had progressive disease. None of the investigated markers was related with overall response rate. In one sample a point mutation in the B/DNBS region of the topo IIalpha gene was detected which substitutes IIe(510) with Val. This tumor had a partial response to four courses of cisplatin/VP16 treatment. The survival analysis showed that the patients with high topo IIalpha expressing tumors had a significantly worse survival compared with the patients with low or intermediate topo IIalpha expressing tumors. In conclusion, no relation was observed between expression of topoisomerase IIalpha, IIbeta, Ki-67, MRP or LRP and response rate. Furthermore, worse survival was seen in patients with high topoisomerase IIalpha expressing tumors. In one tumor sample, a newly described mutation in the B/DNBS region of the topo IIalpha gene was detected, which does not appear to be related to drug resistance.
Lung Cancer 2001 May
PMID:Topoisomerase IIalpha and other drug resistance markers in advanced non-small cell lung cancer. 1132 82


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