Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017638 (glioma)
 30,880 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Reverse transcription (RT)/polymerase chain reaction (PCR) was used to detect the expression of six isoforms of cytochrome P450 which belong to five P450 subfamilies in rat glioma C6 cell line. P450 1A2, 2A1, 2C7, 2E1 were identified by RT-PCR in all samples, including untreated cells as well as cells treated with phenobarbital (PB) or benzo(a)anthracene (BA). P450 3A and 2C11 were not detected in our glioma samples although they were detected in liver tissues in our previous study. To confirm proper PCR products, various restriction enzymes were used to digest the PCR fragments and the expected digestion patterns were obtained. These results demonstrate for the first time that glioma C6 cells, representing a single cell type of rat central nervous system (CNS), contain a P450-dependent metabolism system which seems important for understanding drug metabolism, neurotransmission as well as tumor etiology and chemotherapy in brain.
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PMID:Identification of cytochromes P450 1A2, 2A1, 2C7, 2E1 in rat glioma C6 cell line by RT-PCR and specific restriction enzyme digestion. 750 39

The mixed function oxidase system consists of NADPH-cytochrome P450 reductase (P450 reductase) and various isoforms of cytochrome P450 (P450), which can catalyze the oxidation of a broad range of endogenous and exogenous compounds. In this study, we examined the rat glioma C6 cell line for the presence of P450 reductase and three isozymes of cytochrome P450, 1A1, 2B1, and 2B2, by reverse transcription followed by PCR (RT-PCR). Rat glioma C6 cells were treated with hepatic P450 inducers phenobarbital (PB) or benzo(a)anthracene (BA). Cytochromes P450 1A1, P450 2B1, and P450 2B2, and P450 reductase, were detected in all the different treatment groups. Restriction digestion was used to confirm the PCR fragments and the expected digestion products were obtained. The induction of P450 1A1 and 2B was quantified using competitive PCR. Ten- and five-fold inductions of P450 1A and 2B mRNA after BA or PB treatments, respectively, were detected by competitive PCR. Microsomes prepared from rat glioma C6 cells showed cytochrome P450 spectra with absorption at 450 nm. Ethoxyresorufin O-deethylase activity (11.5 +/- 1.7 pmol/min/mg of microsomal protein) and pentoxyresorufin O-dealkylation activity (8.9 +/- 1.4 pmol/min/mg of microsomal protein) confirmed the induction of P450 1A and 2B at the protein level in response to BA or PB treatments, respectively. These experiments provide further evidence that the rat glioma C6 cell line contains an active mixed function oxidase system that can be induced by hepatic P450 inducers.
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PMID:Identification of inducible mixed function oxidase system in rat glioma C6 cell line. 761 9

Most malignant tumors of the central nervous system do not respond well to chemotherapy. The anticancer drug cyclophosphamide (CPA) is largely ineffective against these neoplasms as its conversion to DNA-alkylating, cytotoxic metabolites is restricted primarily to the liver and these metabolites do not readily cross the blood-brain barrier. Here, we show that brain tumor cells can be sensitized to the cytotoxic effects of CPA, both in culture and in vivo, by introduction of the hepatic enzyme responsible for the activation of CPA, cytochrome P450 2B1. Stable transfection of rat C6 glioma cells with the P450 2B1 gene rendered the cultured tumor cells sensitive to CPA. Further, C6 cells bearing this gene were more sensitive than parental cells to the cytotoxic action of CPA when grown subcutaneously in the flanks of athymic mice. Murine fibroblasts producing a retrovirus vector encoding P450 2B1 and expressing this enzyme were then prepared and grafted into the brains of athymic mice seeded with rat C6 gliomas. Intrathecal administration of CPA prevented the development of meningeal neoplasia and led to partial regression of the parenchymal tumor mass. By contrast, C6 glioma-bearing mice receiving fibroblasts expressing the Escherichia coli lacZ gene and CPA exhibited extensive meningeal tumors and parenchymal solid brain tumors. The in situ activation of CPA by cytochrome P450 2B1 provides a novel approach not only for brain tumor gene therapy, but also for negative, drug-conditional selection of other defined cell populations.
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PMID:Experimental tumor therapy in mice using the cyclophosphamide-activating cytochrome P450 2B1 gene. 794 46

Incubation of C6 glioma cells in the presence of aminoglutethimide, an inhibitor of cholesterol metabolism, together with either adenosine 3',5'-cyclic monophosphate (cAMP) analogues or agents that increase cAMP synthesis, such as cholera toxin, forskolin, and isoproterenol, stimulated the rate of pregnenolone formation by their isolated mitochondria. This effect of cAMP was blocked by the antagonist (Rp)-cAMPS. The incorporation rate of mevalonolactone into pregnenolone was also increased by the stimulation of adenylyl cyclase activity in intact C6 cells. It is concluded that cAMP stimulates glial cell steroidogenesis by increasing the movement of the substrate, cholesterol, to the mitochondria, where it will be metabolized to pregnenolone by the side chain cleavage cytochrome P450 enzyme.
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PMID:Regulation of C6 glioma cell steroidogenesis by adenosine 3',5'-cyclic monophosphate. 830 Jan 94

Malignant astrocytomas are frequently resistant to cytotoxic chemotherapy. A possible mechanism of chemoresistance is drug inactivation within malignant astrocytes by detoxifying enzymes (glutathione transferases (GST) and cytochrome P450's). The aim of this study was to assess whether there was differential expression of these detoxifying enzymes in the central nervous system and any relationship to histological grade (WHO) of the tumours. Immunostaining was performed in 30 consecutive glioma samples, using class specific polyclonal antibodies to subtypes of GST (pi, alpha, mu) and to human cytochrome P450 reductase. GST immunostaining was evident in astrocytes and endothelium but not neurones or oligodendrocytes in normal brain. Immunostaining for GST increased in intensity from well differentiated tumours to glioblastoma. Staining was least evident in surrounding normal brain, strong in reactive astrocytes and astrocytic tumour cells and very intense in gemistocytic and giant tumour cells. Small anaplastic tumour cells had very little GST staining. Where endothelial proliferation was evident, GST staining in endothelial cells was increased. Pi was always the predominant subclass, although GST alpha and mu were also expressed in some tumours. Cytochrome P450 reductase immunostaining was present in normal neurones and malignant astrocytes. Gemistocytic astrocytic tumour cells stained intensely. Further work is necessary to see if there is any correlation between immunostaining intensity survival or response to chemotherapy.
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PMID:Glutathione S-transferases and cytochrome P450 detoxifying enzyme distribution in human cerebral glioma. 852 85

Multiple forms of cytochrome P450 (P450) in brain tissue have been demonstrated to be expressible in brain tissue using polymerase chain reaction (PCR) techniques, Northern blotting, hydroxylation activity assessment and cloning approaches. The antidepressant drug imipramine is metabolized by brain microsomes to multiple products by pathways inhibitable by quinidine, 7,8-benzoflavone, and ketoconazole, well-known inhibitors of P450-catalyzed reactions. Moreover, PCR studies revealed that a number of P450s are expressible in brain tissue and in glioma C6 cells. Quantitative PCR studies further demonstrated the response of many of these forms to induction in agreement with hydroxylation activity results.
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PMID:Expression of multiple forms of brain cytochrome P450. 859 21

Cyclophosphamide is an inactive prodrug which is converted by hepatic cytochrome P450 2B1 to cytotoxic metabolites which produce interstrand DNA cross-linking in a cell cycle-independent fashion. The limited ability of these metabolites to cross the blood-brain barrier contributes to the poor activity of cyclophosphamide against brain tumors. In this study we demonstrate that replication deficient retroviral and adenoviral vector-mediated gene transfer of cytochrome P450 2B1 into 9L glioma cells significantly increases the sensitivity of these tumor cells to cyclophosphamide in vitro, and prolongs the survival of animals bearing intracerebral 9L tumors treated with cyclophosphamide in vivo. Attempts to improve the effectiveness of retrovirally mediated transduction of the P450 2B1 gene by increasing the concentration of cyclophosphamide delivered to the tumors using intracarotid and intratumoral injections did not prolong animal survival, although survival was increased when a second treatment with P450-expressing retroviral vectors and cyclophosphamide was administered. These results suggest that in situ transduction of tumor cells with the P450 2B1 gene using retroviral and adenoviral vectors increases their sensitivity to cyclophosphamide and may have a potential role in the therapy of malignant gliomas.
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PMID:Gene therapy for malignant gliomas using replication incompetent retroviral and adenoviral vectors encoding the cytochrome P450 2B1 gene together with cyclophosphamide. 878 1

Five different isoforms of cytochrome P450 including 1A1, 1A2, 2E1, 2A and 2B6 have been identified in human glioma Hs 683 cell line using RT-PCR reaction. These isoforms belong to four distinct subfamilies. The effect of benzanthracene (Ba) as inducer was tested on the mRNA level of cytochrome P450 1A1. Northern blot analysis clearly showed an induction response from these cells to Ba in a proportion that is comparable to the induction seen in rat glioma cells.
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PMID:Identification of cytochrome P450s in human glioma cell line. 959 88

Although the prognosis of childhood cancers has dramatically improved over the last three decades, new active drugs are needed. Camptothecins represent a very attractive new class of anticancer drugs to develop in paediatric oncology. The preclinical and clinical development of two of these DNA-topoisomerase I inhibitors, i.e. topotecan and irinotecan, is ongoing in paediatric malignancies. Here we review the currently available results of this evaluation. Topotecan proved to be active against several paediatric tumour xenografts. In paediatric phase I studies exploring several administration schedules, myelosuppression was dose-limiting. The preliminary results of topotecan evaluation in phase II study showed antitumour activity in neuroblastoma (response rate: 15% at relapse and 37% in newly diagnosed patients with disseminated disease) and in metastatic rhabdomyosarcoma (40% in untreated patients). Topotecan-containing drug combinations are currently investigated. Irinotecan displayed a broad spectrum of activity in paediatric solid tumour xenografts, including rhabdo-myosarcoma, neuroblastoma, peripheral primitive neuroectodermal tumour, medulloblastoma, ependymoma, malignant glioma and juvenile colon cancer. For several of these histology types, tumour-free survivors have been observed among animals bearing an advanced-stage tumour at time of treatment. The clinical evaluation of irinotecan in children is ongoing. Irinotecan undergoes a complex in vivo biotransformation involving several enzyme systems, such as carboxylesterase, UDPGT and cytochrome P450, in children as well as in adults. Preclinical studies of both drugs have shown that their activity was schedule-dependent. The optimal schedule of administration is an issue that needs to be addressed in children. In conclusion, the preliminary results of the paediatric evaluation of camptothecin derivatives show very encouraging results in childhood malignancies. The potential place of camptothecins in the treatment of paediatric malignant tumours is discussed.
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PMID:Preclinical development of camptothecin derivatives and clinical trials in pediatric oncology. 961 66

Vector-mediated transfer of prodrug-activating genes provides a promising means of cancer gene therapy. In a search for more selective and more potent bioactivating enzymes for gene therapy of malignant brain tumors, the toxicity-generating capacity of the rabbit cytochrome P450 isozyme CYP4B1 was investigated. Rabbit CYP4B1, but not rat or human isozymes, efficiently converts the inert prodrugs, 2-aminoanthracene (2-AA) and 4-ipomeanol (4-IM), into highly toxic alkylating metabolites. Toxicity of these two prodrugs was evaluated in culture in parental and genetically modified rodent (9L) and human (U87) glioma cell lines stably expressing CYP4B1, and in vivo in a subcutaneous 9L tumor model in nude mice. The most sensitive CYP4B1-expressing glioma clone, 9L4B1-60, displayed an LD50 of 2.5 microM for 2-AA and 4-IM after 48 h of prodrug incubation, whereas 20 times higher prodrug concentrations did not cause any significant toxicity to control cells. Substantial killing of control tumor cells by 2-AA was achieved by co-culturing these cells with CYP4B1-expressing cells at a ratio of 100:1, and toxic metabolites could be transferred through medium. In both CYP4B1-expressing cells and co-cultured control cells, prodrug bioactivation was associated with DNA fragmentation, as assayed by fluorescent TUNEL assays and by annexin V staining. Alkaline elution of cellular DNA after exposure to 4-IM revealed extensive protein-DNA crosslinking with single-strand breakage. Growth of 9L-4B1 tumors in nude mice was inhibited by intraperitoneal injection of 4-IM with minimal side effects. Potential advantages of the CYP4B1 gene therapy paradigm include: the low concentrations of prodrug needed to kill sensitized tumor cells; low prodrug conversion by human isozymes, thus reducing toxicity to normal cells; a tumor-killing bystander effect that can occur even without cell-to-cell contact; and the utilization of lipophilic prodrugs that can penetrate the blood-brain barrier.
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PMID:New prodrug activation gene therapy for cancer using cytochrome P450 4B1 and 2-aminoanthracene/4-ipomeanol. 965 Jun 11


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