Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

L-Asparaginase (l-ASP), a bacterial enzyme used since the 1970s to treat acute lymphoblastic leukemia, selectively starves cells that cannot synthesize sufficient asparagine for their own needs. Molecular profiling of the NCI-60 cancer cell lines using five different microarray platforms showed strong negative correlations of asparagine synthetase (ASNS) expression and DNA copy number with sensitivity to l-ASP in the leukemia and ovarian cancer cell subsets. To assess whether the ovarian relationship is causal, we used RNA interference to silence ASNS in three ovarian lines and observed 4- to 5-fold potentiation of sensitivity to l-ASP with two of the lines. For OVCAR-8, the line that expresses the least ASNS, the potentiation was >500-fold. Significantly, that potentiation was >700-fold in the multidrug-resistant derivative OVCAR-8/ADR, showing that the causal relationship between ASNS expression and l-ASP activity survives development of classical multidrug resistance. Tissue microarrays confirmed low ASNS expression in a subset of clinical ovarian cancers as well as other tumor types. Overall, this pharmacogenomic/pharmacoproteomic study suggests the use of l-ASP for treatment of a subset of ovarian cancers (and perhaps other tumor types), with ASNS as a biomarker for patient selection.
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PMID:Asparagine synthetase as a causal, predictive biomarker for L-asparaginase activity in ovarian cancer cells. 1708 36

Drug resistance in lymphoblastic and myeloblastic leukemia cells is poorly understood, with several lines of evidence suggesting that resistance can be correlated with upregulation of human asparagine synthetase (hASNS) expression, although this hypothesis is controversial. New tools are needed to investigate this clinically important question, including potent hASNS inhibitors. In vitro experiments show an adenylated sulfoximine to be a slow-onset, tight-binding inhibitor of hASNS with nanomolar affinity. This binding affinity represents a 10-fold improvement over that reported for the only other well-characterized hASNS inhibitor. The adenylated sulfoximine has a cytostatic effect on L-asparaginase-resistant MOLT-4 cells cultured in the presence of L-asparaginase, an enzyme that depletes L-asparagine in the growth medium. These observations represent direct evidence that potent hASNS inhibitors may prove to be effective agents for the clinical treatment of acute lymphoblastic leukemia.
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PMID:An inhibitor of human asparagine synthetase suppresses proliferation of an L-asparaginase-resistant leukemia cell line. 1718 29

Bacterial L-ASNases (L-asparaginases) catalyse the conversion of L-asparagine into L-aspartate and ammonia, and are widely used for the treatment of ALL (acute lymphoblastic leukaemia). In the present paper, we describe an efficient approach, based on protein chemistry and protein engineering studies, for the construction of trypsin-resistant PEGylated L-ASNase from Erwinia carotovora (EcaL-ASNase). Limited proteolysis of EcaL-ASNase with trypsin was found to be associated with a first cleavage of the peptide bond between Lys53 and Gly54, and then a second cleavage at Arg206-Ser207 of the C-terminal fragment, peptide 54-327, showing that the initial recognition sites for trypsin are Lys53 and Arg206. Site-directed mutagenesis of Arg206 to histidine followed by covalent coupling of mPEG-SNHS [methoxypoly(ethylene glycol) succinate N-hydroxysuccinimide ester] to the mutant enzyme resulted in an improved modified form of EcaL-ASNase that retains 82% of the original catalytic activity, exhibits enhanced resistance to trypsin degradation, and has higher thermal stability compared with the wild-type enzyme.
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PMID:Tailoring structure-function properties of L-asparaginase: engineering resistance to trypsin cleavage. 1731 68

The present work aims at the development of a novel, diagnostic biosensor for monitoring asparagine levels in leukemia. Various immobilization strategies have been applied to improve the stability of the biocomponent (asparaginase). Response time studies have been carried out for different immobilization methods. Phenol Red indicator has been coimmobilized with asparaginase and color visualization approach has been optimized for various asparagine ranges. The detection limit of asparagine achieved with nitrocellulose membrane is 10(-1) M, with silicon gel is 10(-10)-10(-1) M, and with calcium alginate beads is 10(-9)-10(-1) M. Furthermore, the calcium alginate bead system of immobilization has been applied for the asparagine range detection in normal and leukemia serum samples.
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PMID:E. coli K-12 asparaginase-based asparagine biosensor for leukemia. 1770 90

The cure rate for children with acute lymphoblastic leukaemia (ALL) has increased to approximately 70%, in part related to the use of the protein synthesis inhibitor drug asparaginase in multiagent chemotherapy regimens. Its lack of haematological toxicity allows its incorporation into phases of therapy in which myelosuppression would be expected either from the disease itself (induction therapy) or secondary to other chemotherapeutic agents (consolidation, intensification or reinduction phases of therapy). Its antileukaemic effect is related to the degree and duration of asparagine depletion. The 2 native forms of L-asparaginase are derived from Escherichia coli and Erwinia chrysanthemi. The half-lives (t((1/2))) of these forms are approximately 1.2 and 0.6 days, respectively. In order to increase the biological t((1/2)), pegaspargase was synthesised by the covalent attachment of monomethoxypolyethylene glycol (PEG) to native E. coli L-asparaginase: it has a t((1/2)) of approximately 5.7 days. The duration of asparagine depletion, the substrate amino acid of the drug, is directly related to asparaginase t((1/2)). Asparaginase is associated with several unique toxicities, including hyperglycaemia, hypolipoproteinaemia, hypoalbuminaemia, coagulation factor deficiencies, hepatotoxicity and pancreatitis. Since asparaginase is a protein, it may induce hypersensitivity reactions. The incidence of these reactions increases with use. In addition, silent hypersensitivity, i.e. the development of IgG antibodies without clinical reactions, results in a decreased t((1/2)) of asparaginase, shortened duration of asparagine depletion, and probably decreased efficacy. The use of pegaspargase allows continued treatment with asparaginase in patients with clinical hypersensitivity reactions. In addition, its use in patients with silent hypersensitivity may maintain the efficacy of asparaginase. So far, the optimal use of the 3 forms of asparaginase has not been determined in children with ALL, partly due to the lack of appropriate pharmacokinetic monitoring methods. As the technology has become available, it has been demonstrated that there is little rationale for the dosage and administration schedules presently in use. Studies are required to determine appropriate dosages and administration methods (intravenous or intramuscular) and schedules for each form of asparaginase, based upon pharmacokinetic parameters. The incidence and time to onset of hypersensitivity (clinical or silent) reactions and the appropriate means of continuing asparaginase therapy with therapeutic effect needs to be evaluated. Pharmacokinetic studies are now available as a research tool. These will allow further investigation to determine if failure to maintain asparagine depletion is a remediable cause of treatment failure.
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PMID:Acute lymphoblastic leukaemia: a guide to asparaginase and pegaspargase therapy. 1803 Oct 78

The appearance of asparaginase-resistant acute lymphoblastic leukemia (ALL) in transformed cell lines has been correlated with increased expression of asparagine synthetase (ASNS). Recent measurements using mRNA-based assays have raised doubts, however, as to the importance of ASNS protein in the cellular mechanisms that confer drug resistance upon the leukemic cells. Studies aimed at determining the concentration of ASNS protein in human leukemias are therefore needed to resolve this issue. A mass spectrometry (MS)-based procedure is presented for the direct quantification of ASNS protein concentration in complex sample mixtures. This assay is able to distinguish samples from transformed cell lines that express ASNS over a wide dynamic range of concentration. Importantly, this method directly detects ASNS protein, the functional entity that may be synthesizing sufficient asparagine to render leukemia cells resistant to asparaginase-treatment. We also report the successful use of this MS method, which has lower limits of detection and quantification of 30 and 100 attomoles, respectively, for the first direct measurements of ASNS protein concentrations in four patient blast samples.
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PMID:Mass spectrometric quantification of asparagine synthetase in circulating leukemia cells from acute lymphoblastic leukemia patients. 1854 74

L-asparaginase is an effective drug for treatment of children with acute lymphoblastic leukemia (ALL). The effectiveness is thought to result from depletion of asparagine in serum and cells. We investigated the clinical response in vivo of 1000 IU/m(2) pegylated (PEG)-asparaginase and its pharmacokinetic, pharmacodynamic and intracellular effects in children with newly diagnosed ALL before start of combination chemotherapy. The in vivo window response was significantly related to immunophenotype and genotype: 26/38 common/pre B-ALL cases, especially those with hyperdiploidy and TELAML1 rearrangement, demonstrated a good clinical response compared to 8/17 T-ALL (P=0.01) and BCRABL-positive ALL (P=0.04). A poor in vivo clinical window response was related to in vitro resistance to L-asparaginase (P=0.02) and both were prognostic factors for long-term event-free survival (hazard ratio 6.4, P=0.004; hazard ratio 3.7, P=0.01). After administration of one in vivo dose of PEG-asparaginase no changes in apoptotic parameters or in intracellular levels of twenty amino acids in leukemic cells could be measured, in contradiction to the changes found after in vitro exposure. This may be explained by the rapid removal of apoptotic cells from the circulation in vivo. One additional dose of PEG-asparaginase upfront ALL treatment did not lead to other severe toxicities.
Leukemia 2008 Sep
PMID:Pharmacokinetic, pharmacodynamic and intracellular effects of PEG-asparaginase in newly diagnosed childhood acute lymphoblastic leukemia: results from a single agent window study. 1858 Sep 55

Bacterial L-asparaginases are enzymes that catalyze the hydrolysis of l-asparagine to aspartic acid. For the past 30 years, these enzymes have been used as therapeutic agents in the treatment of acute childhood lymphoblastic leukemia. Their intrinsic low-rate glutaminase activity, however, causes serious side-effects, including neurotoxicity, hepatitis, coagulopathy, and other dysfunctions. Erwinia carotovora asparaginase shows decreased glutaminase activity, so it is believed to have fewer side-effects in leukemia therapy. To gain detailed insights into the properties of E. carotovora asparaginase, combined crystallographic, thermal stability and cytotoxic experiments were performed. The crystal structure of E. carotovoral-asparaginase in the presence of L-Asp was determined at 2.5 A resolution and refined to an R cryst of 19.2 (R free = 26.6%) with good stereochemistry. Cytotoxicity measurements revealed that E. carotovora asparaginase is 30 times less toxic than the Escherichia coli enzyme against human leukemia cell lines. Moreover, denaturing experiments showed that E. carotovora asparaginase has decreased thermodynamic stability as compared to the E. coli enzyme and is rapidly inactivated in the presence of urea. On the basis of these results, we propose that E. carotovora asparaginase has limited potential as an antileukemic drug, despite its promising low glutaminase activity. Our analysis may be applicable to the therapeutic evaluation of other asparaginases as well.
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PMID:Structural and functional insights into Erwinia carotovora L-asparaginase. 1864 44

The L-asparaginases from Escherichia coli and Erwinia chrysanthemi are effective drugs that have been used in the treatment of acute childhood lymphoblastic leukaemia for over 30 years. However, despite their therapeutic potential, they can cause serious side effects as a consequence of their intrinsic glutaminase activity, which leads to L-glutamine depletion in the blood. Consequently, new asparaginases with low glutaminase activity, fewer side effects and high activity towards L-asparagine are highly desirable as better alternatives in cancer therapy. L-Asparaginase from Helicobacter pylori was overexpressed in E. coli and purified for structural studies. The enzyme was crystallized at pH 7.0 in the presence of 16-19%(w/v) PEG 4000 and 0.1 M magnesium formate. Data were collected to 1.6 A resolution at 100 K from a single crystal at a synchrotron-radiation source. The crystals belong to space group I222, with unit-cell parameters a = 63.6, b = 94.9, c = 100.2 A and one molecule of L-asparaginase in the asymmetric unit. Elucidation of the crystal structure will provide insight into the active site of the enzyme and a better understanding of the structure-activity relationship in L-asparaginases.
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PMID:Expression, purification and crystallization of Helicobacter pylori L-asparaginase. 1867 46

Asparaginase (ASNase) is an enzyme drug presently approved for the induction of remission in the treatment of patients with acute lymphoblastic leukemia (ALL). The cytotoxic effect of ASNase is derived from its ability to deplete asparagine, an essential amino acid required by certain types of leukemia cells for protein synthesis and survival. Despite its efficacy in enhancing disease remission rate and prolonging complete remission duration in ALL patients, ASNase therapy is nevertheless confounded by a number of serious toxic effects, particularly to organs associated with high protein production (e.g., liver, pancreas), due to the systemic depletion of asparagine. Presented herein is a modified version of our previously established ATTEMPTS protein delivery system that carries the potential to permit a tumor specific, intracellular delivery of ASNase, thereby allowing for a significant reduction of ASNase-induced systemic toxicity. In a previous paper, we already demonstrated the in vitro feasibility of this heparin/protamine-regulated, TAT-mediated system in delivering ASNase directly into ASNase-sensitive murine lymphoma cells. In this article, we further validated the in vivo applicability of this system in animals harboring ASNase-encapsulated L5178Y lymphoma cells. Preliminary results showed that animals inoculated with L5178Y cells containing TAT-ASNase exhibited an extended survival rate of approximately 13% over those harboring L5178Y cells without the encapsulation of ASNase. Furthermore, the TAT-ASNase-treated mice also displayed a significantly improved hematological and liver histological status than the control groups. These findings bring promise to the use of the modified ATTEMPTS delivery system in achieving enhanced ASNase therapy.
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PMID:Preliminary in vivo evaluation of the protein transduction domain-modified ATTEMPTS approach in enhancing asparaginase therapy. 1881 76


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