Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.2 (topoisomerase)
 9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Melanoma cells often display a multidrug-resistant phenotype, but the mechanisms involved are largely unknown. In order to establish a reproducable model system for studying the exact mechanisms conferring chemoresistance, we selected drug-resistant sublines in vitro derived from one parental human melanoma (MeWo) cell line. Four commonly used chemotherapeutic drugs (vindesine, etoposide, fotemustine, cisplatin) with different modes of action were choosen and stable sublines exhibiting four different levels of resistance against each drug were selected by continuous exposure over two years. Analysis of the drug-resistant sublines regarding their pharmacological characteristics and cross-resistance pattern revealed an up to 26-fold increased relative resistance against the alkylating agent fotemustine (MeWoFOTE) and an up to 35.7-fold increased relative resistance against topoisomerase-II-inhibiting etoposide (MeWoETO). Cisplatin selection (MeWoCIS) resulted in a 6-fold higher resistance compared to parental MeWo cells, whereas vindesine exposure (MeWoVIND) increased relative resistance up to 10.2-fold. Sublines selected separately for resistance to the DNA-damaging agents fotemustine, cisplatin and etoposide demonstrated strong cross-resistance. In comparison to the parental cell line drug-resistant sublines showed altered expression patterns of proto-oncogenes. Levels of p53 mRNA decreased with increasing resistance to vindesine, etoposide and fotemustine. Expression of bcl-2 family members (bax, bcl-x) was modulated by fotemustine, etoposide and cisplatin. In addition the expression of members of the fos (c-fos) and jun (c-jun, jun-D) gene family encoding transcription factors of the AP-1 complex was altered in all drug-resistant sublines. The pattern of expression varied with the inducing stimulus and this was paralleled by changes in the transactivation potential of AP-1. Our results reinforce the central role of AP-l in drug resistance probably through its participation in a programmed cellular stress response.
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PMID:Human melanoma cell lines selected in vitro displaying various levels of drug resistance against cisplatin, fotemustine, vindesine or etoposide: modulation of proto-oncogene expression. 949 34

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.
Melanoma Res 1999 Feb
PMID:The chemoresistance of human malignant melanoma: an update. 1033 34

Melanoma has proven to be resistant to conventional chemotherapy; however,the mechanism of chemoresistance is still unclear. Recent reports show that the transcription factor, E2F-1, may play a role in mediating cytotoxicity of certain chemotherapeutic agents. We have shown in a previous study that adenovirus-mediated overexpression of E2F-1 can efficiently induce apoptosis in melanoma cells. In the present study, the effect of E2F-1 expression on drug sensitivity of melanoma cells was evaluated. Two human melanoma cell lines, SK-MEL-28 and SK-MEL-2, were treated with drugs (etoposide, Adriamycin, roscovitine, cisplatin, 5-fluorouracil, or cycloheximide), alone or in combination with adenoviral vectors expressing beta-galactosidase (Ad-LacZ) or E2F-1 (Ad-E2F-1) at a multiplicity of infection of 1 in vitro. E2F-1 expression was confirmed by Western blot analysis. Sublethal concentrations of each drug alone or infection with Ad-E2F-1 alone produced <5% apoptosis by 3 days posttreatment. Conversely, cotreatment with Ad-E2F-1 and low concentrations of etoposide or Adriamycin markedly sensitized melanoma cells to apoptotic cell death. A slight enhancement of the cytotoxicity of roscovitine was demonstrated in combination with E2F-1 overexpression, but not to cisplatin, 5-fluorouracil, or cycloheximide. Ad-LacZ infection showed no obvious effects on drug sensitivity. Overexpression of p21 can block apoptosis induced by the combination chemogene therapy of Ad-E2F-1 and topoisomerase II poisons and does not require its proliferating cell nuclear antigen-binding ability. The protein synthesis inhibitor cycloheximide also has a cytotoxicity-protective effect against topoisomerase II inhibitor/E2F-1-induced apoptosis and suggests that new protein synthesis is required for this process. Topoisomerase II inhibitors also cooperated with Ad-E2F-1 to enhance antitumor activity in an in vivo model using xenografts in nude mice. When combined with Adriamycin or etoposide, E2F-1 adenovirus therapy resulted in an 87% or 91% decrease in tumor size, respectively, compared with controls (P < 0.002). Our results show that adenovirus-mediated E2F-1 gene transfer can sensitize melanoma cells to some chemotherapeutic agents, particularly topoisomerase II poisons, in vitro and in vivo. These results suggest a new chemosensitization strategy for melanoma gene therapy.
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PMID:Adenovirus-mediated E2F-1 gene transfer sensitizes melanoma cells to apoptosis induced by topoisomerase II inhibitors. 1191 54

Apoptotic deficiency is one of the mechanisms leading to chemoresistance due to the potential of many chemotherapeutic drugs to induce apoptosis. We have examined drug-induced apoptosis in the chemosensitive human melanoma cell line MeWo, as well as in its resistant sublines, which were selected by continuous exposure to etoposide (MeWo(Eto1)) and cisplatin (MeWo(Cis1)). In former studies, activation of the mitochondrial pro-apoptotic pathway could not be demonstrated in etoposide-resistant cells after exposure to etoposide. A significant reduction of PARP [poly (ADP-ribose) polymerase] cleavage and caspase activation, but unimpaired DNA fragmentation, was seen in cisplatin-resistant cells after treatment with cisplatin. In the current study, we investigated effects of chemotherapeutic drugs different from the selecting agents cisplatin and etoposide on the observed modulations of the mitochondrial apoptotic pathway. We analysed dose-dependent release of cytochrome c, caspase-9 activation, cleavage of PARP and activation of effector caspases in etoposide and cisplatin-resistant cells after exposure to etoposide, teniposide, cisplatin or fotemustine. In analogy to etoposide exposure, we could not demonstrate any activation of the apoptotic pathway in etoposide-resistant cells after exposure to teniposide, another topoisomerase-II inhibitor. In contrast, exposure to cisplatin and fotemustine led to apoptotic cell death in these cells. This suggests that the deficiency of apoptosis in etoposide-resistant cells is dependent on the trigger by topoisomerase-II inhibitors. Analysis of cisplatin-resistant cells after etoposide and fotemustine exposure revealed an increased activity of the apoptotic pathway when compared with cisplatin exposure at corresponding survival rates in these cells. These results suggest that the observed modulations of the apoptotic pathway in resistant melanoma cell lines are specific for an anti-neoplastic drug and are not fixed at the molecular level, as different chemotherapeutic drugs are capable of overcoming these alterations.
Melanoma Res 2006 Dec
PMID:The altered apoptotic pathways in cisplatin and etoposide-resistant melanoma cells are drug specific. 1711 54

Neural stem cells (NSCs) have been investigated in preclinical models as delivery vehicles for therapeutic genes for treatment of tumors in the central nervous system and other organs. Melanoma at early stages is effectively treated with surgery and radiotherapy, however metastatic disease is almost universally fatal, thus novel therapeutic approaches are needed. We studied the use of HB1.F3.CD therapeutic NSCs, a well-characterized clonal cell line derived from human fetal telencephalon, for their potential of secreting prodrug-activating enzyme. HB1.F3.CD cells were transduced by adenovirus encoding rabbit carboxylesterase (rCE), which converts CPT-11 into SN-38, a potent topoisomerase 1 inhibitor. In vitro cell migration assays revealed robust migration of NSCs to conditioned media from melanoma cells. Cytokine profiles showed that IL-6, IL-8, MCP-1 and TIMP-2, known chemoattractants for stem cells, were highly expressed by melanoma cells. Exposure of melanoma cells to conditioned media from the HB1.F3.CD.rCE cells in the presence of CPT-11 increased the tumor cell-killing effect by approximately 100-fold when compared to CPT-11 alone. Our data demonstrate the rational for NSC-based enzyme/prodrug therapeutic approach to target metastatic melanoma. Future experiments will evaluate the therapeutic efficacy of NSC-mediated melanoma therapy in animal models, which will provide the basis for targeted therapy in patients with advanced melanoma.
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PMID:Therapeutic targeting of melanoma cells using neural stem cells expressing carboxylesterase, a CPT-11 activating enzyme. 1995 Dec 51