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

Characteristics of multiple-drug resistance of rat ascites hepatoma AH66, a cell line induced by dimethylaminoazobenzene and established as a transplantable tumor, were compared with those of AH66F, a drug sensitive line obtained from AH66. The AH66 cell line was resistant to vinblastine, adriamycin, SN-38 an active form of camptothesine, etoposide, and clorambucil by 10-fold or more than the AH66F cell line. The resistance of AH66 cells to vinblastine, adriamycin, and SN-38 was closely related to P-glycoprotein overexpression in the plasma membrane, because the resistance was significantly inhibited by verapamil. AH66 cells contained much glutahione and had a high activity of glutathione S-transferase P-form (GST-P), compared with AH66F cells, and resistance to clorambucil was decreased by treatment with buthionine sulfoximine, an inhibitor of glutathione synthesis. AH66 cells have a similar topoisomerase I activity, but about 6 times lower topoisomerase II activity than AH66F cells. Therefore, the resistance to etoposide and a part of the resistance to adriamycin of AH66 cells seems to depend upon this low topoisomerase II activity. These results, show that the AH66 cell line has high multiple-drug resistance compared with the AH66F cell line, by several mechanisms. Consequently, the AH66 and AH66F cell lines are useful to study naturally acquired multiple-drug resistance of hepatomas.
...
PMID:Characterization of naturally acquired multiple-drug resistance of Yoshida rat ascites hepatoma AH66 cell line. 870 43

We have established a cisplatin resistant subline, MKN/CDDP, from the MKN-45 human stomach adenocarcinoma cell line. MKN/CDDP was 10.7 fold more resistant to cisplatin, 5.4 fold resistant to carboplatin, 2.7 fold resistant to 5-fluorouracil and only 1.4 fold resistant to adriamycin. To investigate the mechanism of the cisplatin resistance in the MKN/CDDP subline, we performed the biochemical characterization of MKN-45 and MKN/CDDP. MKN/CDDP cells showed no induction in p-glycoprotein and topoisomerase II. The level of glutathione S-transferase-pi was higher in MKN/CDDP than the parent line, but a similar level of glutathione S-transferase-L isoform was observed. Superoxide dismutase activity was 1.67 fold higher in the MKN/CDDP subline than the parent line, but 60 kDa catalase was much lower in the MKN/CDDP subline. In addition to those changes. MKN/CDDP was not able to attach to the culture dish, which is probably due to the lack of fibronectin association on the cell surface. The MKN/CDDP subline revealed a variety of biochemical changes which are related to drug inactivation and to cell substratum adhesion. The significance of each modification in the development of the cisplatin resistance will be evaluated in future studies.
...
PMID:Biochemical characterization of cisplatin-resistance in MKN-45 human stomach adenocarcinoma cell line. 891 23

In order to simulate drug resistance observed in the clinic, two cisplatin-resistant cell lines were produced from a murine ovarian reticulosarcoma, M5076 (M5), by pulse (M5/CDDP) and continuous (M5/CDDPc) treatment with cis-diamminedichloroplatinum(II)(CDDP). These cell lines showed a similar stable low level of resistance (approximately 3-fold) to CDDP and cross-resistance to carboplatin, iproplatin and the new alkylating agent tallimustine, but not to L-PAM (L-phenylalanine mustard) and BCNU (1,3-bis(2-chloroethyl)-1-nitrosourea). Collateral sensitivity to two inhibitors of topoisomerase II, VP16 (etoposide) and doxorubicin (Dox), but cross-resistance to the topoisomerase I inhibitor, camptothecin, were observed. The two cell lines were also sensitive to 5-fluorouracil. No increase in the level of glutathione or activity of glutathione S-transferase could be observed in resistant cells compared with the parental M5 cells. Total DNA platination immediately after treatment was similar in the parental and resistant cell lines. Repair of total DNA platination, measured after 24 h of recovery, was undetectable in M5 and M5/CDDP cells, but was 33% in M5/ CDDPc cells. Initial DNA-interstrand cross-links (DNA-ISC) were six times higher in M5 than in M5/CDDP cells, but 24 h after treatment, both lines had completely repaired this damage. M5/ CDDPc cells did not show formation of DNA-ISC at any time after treatment. The two resistant cell lines were tumorigenic when implanted in mice and resistant to CDDP treatment in vivo. The CDDP resistant tumours were not cross-resistant in vivo to L-PAM, BCNU and Dox, which had been active in vitro, nor to tallimustine, which had been cross-resistant in vitro. Mechanisms of resistance in M5/CDDP and M5-CDDPc seem to be based on a lower formation of DNA-ISC combined, for the latter cell line, with a higher repair capacity for total DNA platination.
...
PMID:In vitro and in vivo characterisation of low-resistant mouse reticulosarcoma (M5076) sublines obtained after pulse and continuous exposure to cisplatin. 894 89

The p53 tumour suppressor protein plays a key role in the integration of stress signals. Multi-site phosphorylation of p53 may play an integral part in the transmission of these signals and is catalysed by many different protein kinases including an unidentified p53-N-terminus-targeted protein kinase (p53NK) which phosphorylates a group of sites at the N-terminus of the protein. In this paper, we present evidence that the delta and epsilon isoforms of casein kinase 1 (CK1delta and CK1epsilon) show identical features to p53NK and can phosphorylate p53 both in vitro and in vivo. Recombinant, purified glutathione S-transferase (GST)-CK1delta and GST-CK1epsilon fusion proteins each phosphorylate p53 in vitro at serines 4, 6 and 9, the sites recognised by p53NK. Furthermore, p53NK (i) co-purifies with CK1delta/epsilon, (ii) shares identical kinetic properties to CK1delta/epsilon, and (iii) is inhibited by a CK1delta/epsilon-specific inhibitor (IC261). In addition, CK1delta is also present in purified preparations of p53NK as judged by immunoanalysis using a CK1delta-specific monoclonal antibody. Treatment of murine SV3T3 cells with IC261 specifically blocked phosphorylation in vivo of the CK1delta/epsilon phosphorylation sites in p53, indicating that p53 interacts physiologically with CK1delta and/or CK1epsilon. Similarly, over-expression of a green fluorescent protein (GFP)-CK1delta fusion protein led to hyper-phosphorylation of p53 at its N-terminus. Treatment of MethAp53ts cells with the topoisomerase-directed drugs etoposide or camptothecin led to increases in both CK1delta-mRNA and -protein levels in a manner dependent on the integrity of p53. These data suggest that p53 is phosphorylated by CK1delta and CK1epsilon and additionally that there may be a regulatory feedback loop involving p53 and CK1delta.
...
PMID:p53 is phosphorylated in vitro and in vivo by the delta and epsilon isoforms of casein kinase 1 and enhances the level of casein kinase 1 delta in response to topoisomerase-directed drugs. 934 7

A cisplatin-resistant cell line, SBC-3/CDDP, was established from a human small-cell lung cancer cell line, SBC-3. The SBC-3/CDDP cells were 13.1-fold more resistant to cisplatin than the parent SBC-3 cells. We investigated the cellular changes of this cell line with regard to the development of resistance to cisplatin. The SBC-3/CDDP cells showed various characteristics as follows: a) increased intracellular glutathione and glutathione S-transferase content b) decreased intracellular accumulation of cisplatin, c) increased topoisomerase I activity and the same topoisomerase II activity as the parent SBC-3 cells, and 4) strong cross-resistance to the platinum analogues and mitomycin C, moderate cross-resistance to 7-ethyl-10-hydroxy-camptothecin (SN-38), 4-hydroperoxy cyclophosphamide, etoposide, Adriamycin and methotrexate, and collateral sensitivity to vinca alkaloids and 5-fluorouracil. From these observations, the SBC-3/CDDP cells could be useful as a well characterized cisplatin-resistant cell line, and the resistance pattem in this cell line will give us much information for eradication of cisplatin-resistant tumor cells.
...
PMID:Cisplatin-resistant human small cell lung cancer cell line shows collateral sensitivity to vinca alkaloids. 961 43

Cross-resistance between different cytostatic agents which are structurally and functionally dissimilar is a common phenomenon called multidrug resistance (MDR). The best characterized mechanism of MDR involves P-glycoprotein. However, this does not completely explain MDR. Within the last few years, two new genes that can confer MDR have been identified (MRP and LRP). Furthermore, topoisomerase II has been associated with a special form of MDR. During the past several years, considerable interest has been shown in strategies to reverse MDR by using pharmacological compounds, monoclonal antibodies, immunotoxins, bispecific antibodies, antisense oligodeoxynucleotides, ribozymes, and albumin-conjugated drugs in in vitro and in vivo assays. All these experimental assays demonstrated that MDR can be circumvented. Two agents that have received the most attention in the clinic are verapamil and cyclosporin A. Despite some promising results (especially in hematological malignancies), the results obtained in the treatment of solid tumors with modulators have so far been quite disappointing. This may be explained by the fact that the MDR phenotype alone does not completely account for the resistance of human cancer. Several other resistance-related proteins (e.g., glutathione S-transferase, metallothionein, O6-alkylguanine-DNA-alkyltransferase, thymidylate synthase, dihydrofolate reductase, heat shock proteins) can be also expressed in resistant tumors. Additionally, cell proliferation, vascularization and apoptosis are involved in resistance.
...
PMID:Multidrug resistance and its reversal. 971 85

To study the development of drug resistance in childhood hepatoblastoma (HB) using a model closely related to in vivo conditions, we cultivated HB xenografts from 3 patients into mice and treated these tumors with either adriamycin (ADR) or cisplatin (CIS). Determination of the relative expression levels of various resistance associated genes by a cDNA-PCR approach showed: a) Significantly enhanced MDR1 gene expression levels after treatment with ADR in each case. b) Significantly enhanced glutathione S-transferase mu (GST mu) gene expression levels after treatment with CIS in 2/3 xenografts. c) Significantly decreased levels of topoisomerase IIa (TOPO IIa) in tumors of the same two patients after treatment with either ADR or CIS. These findings give evidence that the MDR1-, GST mu- and TOPO IIa-gene products may contribute to drug resistance in HB.
...
PMID:Altered expression of resistance associated genes in hepatoblastoma xenografts incorporated into mice following treatment with adriamycin or cisplatin. 971 21

We have established ten transplantable human soft-tissue sarcoma (STS) xenografts grown as subcutaneous tumours in the nude mouse. Nine xenografts originated from patients that needed chemotherapy in the course of their disease. The xenografts were tested for their sensitivity to maximum tolerated doses of five anti-cancer agents. Growth of treated tumours was expressed as a percentage of control tumour growth and a growth inhibition > 75% was measured for doxorubicin in 20% of the STS xenografts, for cyclophosphamide in 30%, for ifosfamide in 20%, for vincristine in 20%, whereas etoposide was not effective in the STS xenografts. In three out of ten STS xenografts MDR1 mRNA was detectable, but this was not related to the resistance against doxorubicin, vincristine or etoposide. Topoisomerase IIalpha mRNA expression levels did not reflect sensitivity to doxorubicin or etoposide. In all STS tissues, however, these levels were lower than topoisomerase IIalpha mRNA in a drug-sensitive human ovarian cancer xenograft. Glutathione concentrations and the activities of glutathione S-transferase, glutathione peroxidase and glutathione reductase were not related to resistance against the alkylating agents or doxorubicin. Of interest, in all STS tissues, glutathione S-transferase pi was the predominant isoenzyme present. In conclusion, chemosensitivity of the STS xenografts reflects clinical response rates in phase II trials on the same compounds in adult STS patients. Relatively low levels of topoisomerase IIalpha mRNA may partly account for intrinsic resistance against, for example, doxorubicin. Additional factors must contribute to moderate responsiveness to alkylating agents.
...
PMID:Characterization of human soft-tissue sarcoma xenografts for use in secondary drug screening. 986 68

Malignant melanoma is considered to be a chemotherapy-refractory tumour and the commonly used anticancer drugs do not seem to modify the prognosis of metastatic disease. The cellular resistance mechanisms involved in melanoma chemoresistance have not yet been elucidated. Melanoma-derived cell lines are often markedly chemoresistant. Using the in vitro soft agar culture system to predict tumour cell sensitivity in well-established human melanoma cell lines, a high degree of resistance against all the cytostatic agents studied has been reported, suggesting the presence of intrinsic cellular resistance mechanisms. The relevance of the well-defined resistance mechanisms mediated by P-glycoprotein, multidrug resistance-associated protein (MRP), the glutathione/glutathione S-transferase system and topoisomerase II enzyme are reviewed. Mutated N-Ras oncogene has recently been implicated in melanoma resistance to cisplatin, both in vitro and in vivo, and the role of two other oncogenes, Bcl-2 and p53, which are already involved in the chemoresistance of haematological and solid malignancies, is beginning to be better elucidated. The finding that many chemotherapeutic agents can kill susceptible cells through the apoptosis pathway provides new molecular insight into chemoresistance mechanisms and suggests that apoptosis and/or resistance to apoptosis of melanoma cells should be investigated to better clarify the mechanism of melanoma chemoresistance.
...
PMID:The chemoresistance of human malignant melanoma: an update. 1033 34

DNA topoisomerase II-an essential nuclear enzyme in DNA replication and transcription, chromatin segregation, and cell cycle progression-is also a target of clinically useful anticancer drugs. Preliminary observations of a positive correlation between the expression of topoisomerase (topo) IIalpha and the retinoblastoma protein (Rb) in a series of rhabdomyosarcoma cells prompted us to ask whether these two proteins interact in vivo. Using human rhabdomyosarcoma and leukemic cell lines, we found a physical association between topo IIalpha and Rb protein by reciprocal immunoprecipitation and immunoblotting, in which topo IIalpha appeared to interact primarily with the underphosphorylated form of Rb. Experiments with truncated glutathione S-transferase-Rb fusion proteins and nuclear extracts of Rh1 rhabdomyosarcoma cells indicated that topo IIalpha binds avidly to the A/B pocket domain of Rb, which contains the intact spacer amino acid sequence. To determine whether this interaction has functional consequences in vivo, we expressed wild-type and mutant Rb in human cervical carcinoma cells lacking functional Rb. Wild-type, but not mutant, Rb inhibited topo II activity in nuclear extracts of these transfected cells. Moreover, purified wild-type Rb inhibited the activity of purified human topo IIalpha, indicating a direct interaction between these two proteins. We conclude that topo IIalpha associates physically with Rb in interactions that appear to have functional significance.
...
PMID:Functional interaction between human topoisomerase IIalpha and retinoblastoma protein. 1039 12


<< Previous 1 2 3 4 Next >>

---