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

Despite innovations in imaging, surgery, and radiation therapy, local failure remains the principle clinical problem in most CNS malignancies. To date, chemotherapy has not major impact in the treatment of most adult CNS tumors. The inroads made by chemotherapy in pediatric CNS malignancies suggest that novel drugs, or drug combinations, may improve therapy. Topoisomerase I (Topo I) inhibitors are a relatively new group of chemotherapy drugs with a novel mechanism of action. Drugs in this group currently undergoing clinical trials are the Camptothecin analogues Topotecan, CPT-11, and 9-aminocamptothecin. There is substantial preclinical and some clinical evidence to suggest that these drugs could be useful in the treatment of CNS malignancies. Preclinical studies with the water soluble Topo I inhibitor, Topotecan, demonstrate antineoplastic activity in a variety of CNS malignancies. In addition, Topotecan has good CNS penetration in primates, and recent preliminary phase I and II clinical trials of Topotecan in pediatric and adult CNS malignancies have been promising. In this paper, we describe the unique mechanism of action, antineoplastic activity, and radiosensitizing properties of Topo I inhibitors. We present the first report demonstrating potentiation of radiation lethality by Topotecan in a human glioma (D54) cell line. The dose enhancement ratio was 3.2 at 10% survival. Thus, there is evidence to suggest that Topo I inhibitors may be beneficial in the treatment of CNS neoplasms on the basis of their antineoplastic activity alone, as well as their radiosensitizing effects. Two clinical trials which utilize concurrent Topotecan and radiation in the treatment of pediatric and adult CNS malignancies are discussed.
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PMID:The potential of topoisomerase I inhibitors in the treatment of CNS malignancies: report of a synergistic effect between topotecan and radiation. 886 97

The overexpression of the multidrug resistance (mdr1) gene and its product, P-glycoprotein (P-gp), is thought to limit the successful chemotherapy of human tumors. Recent studies demonstrate that SN-38, a metabolite of the camptothecin (CPT) derivative CPT-11, has antitumor effects on several tumors, but the mechanisms responsible for its cytotoxicity remain unclear. We therefore determined whether SN-38 has cytotoxic effects on MDR human glioblastoma GB-1 cells and non-MDR human glioblastoma U87-MG cells. Furthermore, we determined what role SN-38 plays in the induction of cytotoxicity in these tumor cells. In this study, we demonstrated that SN-38 had significantly stronger antitumor effects on GB-1 and U-87MG cells than did CPT (P < 0.01 and P < 0.05, respectively). In addition, findings obtained using a DNA fragmentation assay, Hoechst 33258 staining, in situ end-labeling and cell cycle analysis demonstrated that SN-38 induced apoptosis in these tumors. Our results suggest that SN-38 has a stronger antitumor effect on malignant glioma cells regardless of MDR expression than does CPT, and therefore can be considered a new chemotherapeutic agent potentially effective in the treatment of human primary or recurrent malignant gliomas resistant to chemotherapy.
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PMID:Induction of apoptosis in multi-drug resistant (MDR) human glioblastoma cells by SN-38, a metabolite of the camptothecin derivative CPT-11. 905 55

Busulfan is an alkylating agent commonly used in the treatment of chronic myelogenous leukemia and in combination with cyclophosphamide in preparation for allogeneic bone marrow transplantation. Serial treatment of a childhood high-grade glioma xenograft (D-456 MG) with busulfan resulted in a busulfan-resistant xenograft, D-456 MG(BR). Cross-resistance to 1,3-bis(2-chloroethyl)-1-nitrosourea was seen but not resistance to cyclophosphamide or CPT-11. Cytoplasmic levels of glutathione in D-456 MG(BR) were approximately one-half those found in D-456 MG. This depletion could not be explained by levels of glutathione-S-transferase, or by amplification, rearrangement, or increased levels of transcript of gamma-glutamylcysteine synthetase. Furthermore, depletion of glutathione in D-456 MG did not alter busulfan activity. Quantitation of busulfan levels in D-456 MG and D-456 MG(BR) xenografts following treatment of mice at the dose lethal to 10% of the animals demonstrated that significantly lower levels of drug were achieved in D-456 MG(BR). These studies suggest that alterations in drug transport or metabolism of busulfan may play a role in the resistance of D-456 MG(BR) to this alkylator.
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PMID:Characterization of the mechanisms of busulfan resistance in a human glioblastoma multiforme xenograft. 927 17

Oxaliplatin is a new platinum analog of the DACH family. Recent preclinical data have confirmed its non overlapping spectrum of activity with cisplatin, including acquired and intrinsic platinum resistant cell lines (as KB-CP, A 2780, HT29, CaCo2 colon cancer). When combined with other cytotoxic agents (5FU, SN38, CDDP, carboplatin), oxaliplatin has additive and/or synergistic antitumoral effects on various in vitro and in vivo models (colon, breast, ovarian and epidermoid tumors). Phase II trials have confirmed a sensorial peripherical neuropathy as its limiting toxicity while neither ototoxicity nor renal toxicities and only limited myelotoxicity were noted. Available phase II studies have established its antitumoral activity as single agent in 5FU refractory colon carcinoma while preliminary results suggest efficacy in cisplatin resistant ovarian cancer, in non small cell lung cancer, non Hodgkin lymphoma. Antitumoral activity has been observed during phases 1 in melanoma, glioma, breast and oesophageal cancers. A high response rate (28-65%) with the triple association (FU/folinic acid/oxaliplatin) has been reported in advanced colon cancer treated in first and second line settings. The results of two randomized phase III studies (FU/folinic acid +/- oxaliplatin) are expected. The oxaliplatin/cisplatin combination as salvage regimen had produced significant antitumoral activity (response rate: 45%) in resistant/refractory ovarian cancer. Finally, recent experimental and clinical data have outlined the potential interest in the development of this new original platinum compound. New single agent phases II are expected in other tumor types as well as new oxaliplatin combinations are ongoing (phase I trials of oxaliplatin/CPT-11 and of oxaliplatin/carboplatin, phase II study of oxaliplatin-vinorelbine in lung cancer.
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PMID:[Oxaliplatin: the first DACH platinum in clinical practice]. 929 71

We have isolated a cDNA encoding a rabbit carboxylesterase (CE; EC 3.1.1.1) that converts the camptothecin-derived prodrug irinotecan (CPT-11) to the potent topoisomerase I inhibitor 7-ethyl-10-hydroxycamptothecin. NH2-terminal amino acid sequencing of a purified rabbit CE allowed the design of redundant oligonucleotides to perform PCR from rabbit liver cDNA. DNA sequencing of the PCR product confirmed the identity of the clone, and after both 5' and 3' rapid amplification of cDNA ends, oligonucleotide primers were designed to amplify the entire cDNA. The 1698-bp open reading frame encoded a 565-amino acid protein containing the characteristic CE B-1 and B-2 motifs, a hydrophobic NH2-terminal leader sequence, and the COOH-terminal residues HIEL that are thought to be responsible for protein localization in the endoplasmic reticulum. Transient expression of the cDNA in COS-7 cells resulted in CE activity in cell extracts and increased the sensitivity of cells to CPT-11. Additionally, stable expression of the rabbit liver CE cDNA in the human glioma U-373 MG cell line resulted in a 56-fold decrease in the IC50 value for CPT-11, whereas the expression of a human alveolar macrophage cDNA encoding a highly homologous CE produced no change in drug sensitivity.
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PMID:Isolation and partial characterization of a cDNA encoding a rabbit liver carboxylesterase that activates the prodrug irinotecan (CPT-11). 963 92

Although topoisomerase inhibitors, such as camptothecin and topotecan, have been widely used in the treatment of nonglial tumors, their application for gliomas has been limited by poor efficacy relative to toxicity that may in part reflect limited bioavailability and blood stability of these agents. However, the potential promise of this class of agents has fostered efforts to develop new, more potent, and less toxic inhibitors that may be clinically relevant. Using a cascade radical annulation route to the camptothecin family, we developed a series of novel camptothecin analogues, 7-silylcamptothecins ("silatecans"), that exhibited potent inhibition of topoisomerase I, dramatically improved blood stability, and sufficient lipophilicity to favor blood-brain barrier transit. We explored the efficacy of a series of these agents against a panel of five high-grade glioma cell lines to identify a promising compound for further preclinical testing. One of the most active agents in our systems (DB67) inhibited tumor growth in vitro with an ED50 ranging between 2 and 40 ng/ml, at least 10-fold more potent than the effects observed with topotecan, and at least comparable with those of SN-38, the active metabolite of CPT-11. Because DB67 also exhibited the highest human blood stability of any of the agents examined, this agent was then selected for in vivo studies. A dose-escalation study of this agent in a nude mouse U87 glioma model system demonstrated a concentration-dependent effect, with tumor growth inhibition at day 28 postimplantation (the day control animals began to require sacrifice because of large tumor size) of 61 +/- 7% and 73 +/- 3% after administration of DB67 doses of 3 and 10 mg/kg/day, respectively, for 5 days beginning on postimplantation day 7. Animals that continued treatment with 10 mg/kg/day in three additional 21-day cycles all remained progression free after >90 days of follow-up but later developed enlarging tumors after treatment was stopped. However, a slightly higher dose (30 mg/kg/day) induced complete tumor regression after only two cycles in all study animals and was effective even if treatment was delayed until large, bulky tumors had developed. Application of the 30 mg/kg/day dose to treat established intracranial glioma xenografts led to long-term (>90 day) survival in six of six animals, whereas all controls died of progressive disease (P < 0.00001). No apparent toxicity was encountered in any of the treated animals. In summary, the present studies indicate that silatecans may hold significant promise for the treatment of high-grade gliomas and provide a rationale for proceeding with further preclinical evaluation of their efficacy and safety versus commercially available camptothecin derivatives.
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PMID:Potent topoisomerase I inhibition by novel silatecans eliminates glioma proliferation in vitro and in vivo. 1051 2

Temozolomide, an imidazole tetrazinone, and CPT-11, a camptothecin derivative, have previously been shown to have anti-central nervous system tumor activity in laboratory and clinical studies. The current experiments were designed to evaluate the activity of temozolomide plus CPT-11 against a malignant glioma-derived xenograft, D-54 MG, growing s.c. in athymic nude mice. The initial schedule of i.p. drug administration was temozolomide at 0.1 LD10 on day 1 and CPT-11 at 0.1 LD10 on days 1-5 and 8-14. The combination of these two agents produced greater than additive activity against D-54 MG. This enhanced activity was maintained when the initial administration of CPT-11 was delayed to day 3 or day 5. However, when CPT-11 was administered first on day 1 using 0.5 LD10 (for the single dose schedule) followed by temozolomide (0.1 LD10) 5 h, 3 days, or 5 days later, the enhancement of activity was substantially reduced. These results demonstrate that the combination of temozolomide plus CPT-11 displays a schedule-dependent enhancement of antitumor activity, suggest a mechanistic explanation for the enhanced activity, and provide the rationale for a Phase I trial of this regimen.
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PMID:Schedule-dependent activity of temozolomide plus CPT-11 against a human central nervous system tumor-derived xenograft. 1105 Dec 70

Temozolomide (Temodar in the United States, Temodal globally; Schering Corporation, Kenilworth, NJ) has several characteristics that make it appealing for combination therapies: broad-spectrum antitumor activity, the ability to cross the blood-brain barrier, a good safety profile with nonoverlapping toxicities, an oral formulation, and the ability to overcome resistance to nitrosoureas. Preclinical and phase I trials have shown the additive or synergistic activity of temozolomide combined with carmustine against solid tumors, including malignant glioma, and the sequence-dependent effects of the combination. Toxicity is lower and the maximum tolerated dose is higher when carmustine is given before temozolomide. Studies also have examined the combination of temozolomide with the topoisomerase I inhibitor irinotecan (CPT-11), an alkaloid derivative of camptothecin that has shown activity against malignant glioma. Temozolomide followed by CPT-11 was more effective than either agent alone. A major issue facing investigators now is determining which of the several schedules of temozolomide and CPT-11 are optimal. Completed and ongoing studies of temozolomide in combination with carmustine, including polifeprosan carmustine implant (Gliadel wafers; Aventis Pharmaceuticals, Parsippany, NJ), and CPT-11 are described.
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PMID:Temozolomide in combination with other cytotoxic agents. 1155 Jan 36

A phase II study of irinotecan (CPT-11) was conducted at Duke University Medical Center, Durham, NC, to evaluate the activity of this agent in children with high-risk malignant brain tumors. A total of 22 children were enrolled in this study, including 13 with histologically verified recurrent malignant brain tumors (glioblastoma multiforme [GBM] 4, anaplastic astrocytoma 1, ependymoma 5, and medulloblastoma/primitive neuroectodermal tumor 3), 5 with recurrent diffuse pontine glioma, and 4 with newly diagnosed GBM. All patients with recurrent tumor had prior chemotherapy and/or irradiation. Each course of CPT-11 consisted of 125 mg/m ( 2 ) per week given i.v. for 4 weeks followed by a 2-week rest period. Patients with recurrent tumors received therapy until disease progression or unacceptable toxicity. Patients with newly diagnosed tumors initially received 3 cycles of treatment to assess tumor response and then were allowed radiotherapy at physician's choice; patients who demonstrated a response to CPT-11 prior to radiotherapy were allowed to continue the drug after radiation until disease progression or unacceptable toxicity. A 25% to 50% dose reduction was made for grade III-IV toxicity. Responses were assessed after every course by gadolinium-enhanced MRI of the brain and spine. Twenty-two patients received a median of 2 courses of CPT-11 (range, 1-16). Responses were seen in 4 of 9 patients with GBM or anaplastic astrocytoma (44%; 95% confidence interval, 11%-82%) (complete response in 2 patients with recurrent GBM lasting 9 months and 48+ months; partial response in one patient with a newly diagnosed midbrain GBM lasting 18 months prior to radiotherapy; and partial response lasting 11 months in 1 patient with recurrent anaplastic astrocytoma), 1 of 5 patients with recurrent ependymoma (partial response initially followed by stable disease lasting 11 months), and none of 5 patients with recurrent diffuse pontine glioma. Two of 3 patients with medulloblastoma/primitive neuroectodermal tumor had stable disease for 9 and 13 months. Toxicity was mainly myelosuppression, with 12 of 22 patients (50%) suffering grade II-IV neutropenia. Seven patients required dose reduction secondary to neutropenia. CPT-11, given in this schedule, appears to be active in children with malignant glioma, medulloblastoma, and ependymoma with acceptable toxicity. Ongoing studies will demonstrate if activity of CPT-11 can be enhanced when combined with alkylating agents, including carmustine and temozolomide.
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PMID:Phase II study of irinotecan (CPT-11) in children with high-risk malignant brain tumors: the Duke experience. 1191 1

This phase II study was designed to evaluate the safety, tolerability, and efficacy of irinotecan (CPT-11) in the treatment of adults with malignant glioma. Patients with progressive or recurrent malignant gliomas were enrolled. CPT-11 was administered as a 90-minute intravenous infusion at a dose of 300 mg/m(2) once a week every 3 weeks. After 2 treatments, doses were increased to 350 mg/m(2) in those patients without grade III/IV toxicities. Dose modifications were made for toxicities. All 14 patients who enrolled (11 males and 3 females) were treated with CPT-11 and were assessable for survival, response, and toxicity. The majority of patients (86%) had prior surgery. Two patients had a confirmed partial response and 2 patients (14%) had stable disease. Median survival was 24 weeks. Median time to tumor progression was 6 weeks. The primary hematologic toxicity was grade III/IV neutropenia, which was observed in 14% of patients. Infrequent grade III/IV nonhematologic toxicity was observed, possibly because of the concomitant use of anticonvulsants, which may have altered pharmacokinetics. These results suggest that CPT-11 has activity against recurrent malignant glioma using a dosing regimen of 300 mg/m(2) every 3 weeks showing limited toxicity. The concurrent use of anticonvulsant medications may have played a role in altering pharmacokinetics and thus the maximum tolerated dose in this patient population.
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PMID:Irinotecan treatment for recurrent malignant glioma using an every-3-week regimen. 1194 4


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