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)

Through the use of drug-adapted tissue culture cells, correlations have been observed between the level of specific enzymes and drug resistance. Drug resistance, however, may be due to multiple factors. To test whether the activity of daunorubicin reductase or NADPH diaphorase independently influences in vitro daunorubicin-induced cytotoxicity, we developed somatic cell hybrid clones to partially isolate these factors. This was accomplished by fusing daunorubicin-resistant myeloblast cells obtained from a patient with monosomy 7 leukemia to a daunorubicin-sensitive Chinese hamster cell line. The in vitro cytotoxicity of daunorubicin was compared in hybrid clones having variable enzyme activities; the concentrations of daunorubicin that inhibited the growth of clones by 50% did not differ by more than 2-fold, whereas daunorubicin reductase activities and NADPH diaphorase isozyme activities differed by more than 100- and 15-fold, respectively. These large differences in enzymatic activity were obtained in part by the suppression of specific hamster genes, indicating a regulatory control mechanism for xenobiotic enzymes. Our findings suggest that in this system substantial intercellular variation in the activity of these xenobiotic enzymes does not independently influence cellular resistance to daunorubicin.
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PMID:Use of somatic cell hybrids to analyze role of specific enzymes in daunorubicin cytotoxicity. 354 57

The Ah locus represents a complex "cluster" of genese controlling the induction of numerous drug-metabolizing enzyme "activities" by polycyclic aromatic compounds. Allelic differences at the Ah locus are reflected in the large differences in inducibility of cytochrome P1-450 and benzo[a]pyrene metabolism in numerous tissues when the mice receive the chemical daily in their diet. This experimental model system offers to the hematologist and clinical pharmacologist a means to study genetic differences in toxic chemical depression of the bone marrow, as well as a potential model to study aplastic anemia and leukemia explainable on a single-gene basis. The genetically "responsive" individual who is at increased risk for cancer caused by subcutaneous or topical or intratracheal polycyclic hydrocarbons is at decreased risk for toxicity of the bone marrow and leukemia caused by oral benzo[a]pyrene (when compared with the genetically "nonresponsive" individual receiving the same dose of the same xenobiotic). In other words, tissue sites in direct contact with the carcinogen develop cancer in responsive animals because of induced P1-450; tissues in distant sites of the body may develop malignancy in nonresponsive animals because more carcinogen reaches that tissue due to decreased P1-450 induction all over the body and therefore decreased detoxication. Not only the dct with the carcinogen develop cancer in responsive animals because of induced P1-450; tissues in distant sites of the body may develop malignancy in nonresponsive animals because more carcinogen reaches that tissue due to decreased P1-450 induction all over the body and therefore decreased detoxication. Not only the dct with the carcinogen develop cancer in responsive animals because of induced P1-450; tissues in distant sites of the body may develop malignancy in nonresponsive animals because more carcinogen reaches that tissue due to decreased P1-450 induction all over the body and therefore decreased detoxication. Not only the dose but the route of administration and the tissue in which the malignancy or toxicity develops are therefore very important in the interpretation of data from tumorigenesis or toxicity experiments involving P1-450 inducers such as polycyclic hydrocarbons. There exists sufficient evidence that heritable variation of the Ah locus occurs in man. Growing evidence indicates that persons with higher aryl hydrocarbon hydroxylase inducibility in their cultured mitogen-activated lymphocytes may have a statistically significantly increased risk for certain types of cancer and drug toxicity. It remains to be determined at the present time, however, whether this genotype can be used as a biochemical marker in the individual patient for predicting increased susceptibility to certain types of environmentally caused cancers or toxicity in man.
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PMID:Genetic differences in susceptibility to chemically induced myelotoxicity and leukemia. 701 19

A relationship was proved between constitutive activity of leukemic cell c-jun-N-terminal kinase (JNK) and treatment failure in AML. Specifically, early treatment failure was predicted by the presence of constitutive JNK activity. The mechanistic origins of this association was sought. A multidrug resistant leukemic cell line, HL-60/ADR, characterized by hyperexpression of c-jun and JNK activity, was transfected with a mutant c-jun vector, whose substrate N-terminal c-jun serines were mutated. Down-regulated expression occurred of c-jun/AP-1-dependent genes, catalase and glutathione-S-transferase (GST) pi, which participate in cellular homeostasis to oxidative stress and xenobiotic exposure. MRP-efflux was abrogated in HL-60/ADR cells with dominant-negative c-jun, perhaps because MRP1 protein expression was also lost. Heightened sensitivity to daunorubicin resulted in cells subjected to this change. Biochemical analysis in 67 primary adult AML samples established a statistical correlation between cellular expression of c-jun and JNK activity, JNK activity with hyperleukocytosis at presentation of disease, and with exuberant MRP efflux. These findings reflect the survival role for c-jun/AP-1 and its regulatory kinase previously demonstrated for yeast in homeostatic response to oxidative stress and in operation of ATP-binding cassette efflux pumps, and may support evolutionary conservation of such function. Thus, JNK and c-jun may be salient drug targets in multidrug resistant AML.
Leukemia 2002 May
PMID:Role for c-jun N-terminal kinase in treatment-refractory acute myeloid leukemia (AML): signaling to multidrug-efflux and hyperproliferation. 1198 40

Genetic approaches to understanding the etiology of the acute leukemias are beginning to deliver meaningful insights. Polymorphic variants in xenobiotic metabolizer loci were a natural starting point to study the relevance of these changes. The finding that glutathione S-transferase (GST) T1 null variants increase leukemia risk has implicated oxidative stress in hematopoietic stem cells as an important etiological factor in acute myeloid leukemia (AML). The importance of these enzyme systems in handling specific substrates has also been confirmed by the finding of an increased risk of therapy-related leukemia in individuals with underactive variants of GSTP1 who have been exposed to a chemotherapeutic agent metabolized by this enzyme. Benzene is a well-recognized leukemogen, and genetic variants in its metabolic pathway can modulate the risk of leukemia following exposure. In particular, underactive variants of the NAD(P)H:quinone oxidoreductase 1 gene (NQO1) seem to increase the risk of AML. Other enzymes within the pathway are proving more difficult to study because of the absence of variants that significantly affect the biological activity of the enzyme under study. No effect of the myeloperoxidase (MPO) gene variants in altering the risk of AML has been seen in our studies. Another pathway recently shown to be important in determining leukemia risk is folic acid metabolism, particularly important in predisposition to acute lymphocytic leukemia (ALL). Polymorphic variants of the methylenetetrahydrofolate reductase gene (MTHFR) which impair its activity have been shown to be associated with a protective effect. This is thought to be due to an increased availability of nucleotide precursors for incorporation into DNA. This finding implicates misincorporation of uracil into DNA as an important mechanism of leukemic change in lymphoid precursors. Future studies will extend these observations but will require biological material collected from large well-controlled epidemiological studies. The technological challenges imposed by the high throughput of samples required by these studies are currently being addressed.
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PMID:Metabolic enzyme polymorphisms and susceptibility to acute leukemia in adults. 1208 44

The case records of 99 consecutive children with acute lymphoblastic leukaemia who received either 6-thioguanine (6-TG) or 6-mercaptopurine (6-MP) as maintenance therapy for at least 1 year were reviewed for hepatic veno-occlusive disease (VOD). Overall, 12% of those on 6-TG developed VOD (all boys). Isolated persistent thrombocytopenia appeared to be the earliest indicator of incipient VOD. Multivariate analysis identified male sex and 6-TG as risk factors. In all cases, VOD was mild and reversible on withdrawing 6-TG or replacing it with 6-MP. The data implicate a sex-linked polymorphic variation in xenobiotic pathways of thiopurine metabolism in the pathogenesis of VOD.
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PMID:Veno-occlusive disease in patients receiving thiopurines during maintenance therapy for childhood acute lymphoblastic leukaemia. 1508 28

The generation, transmission (e.g. power lines, transformers, service wires, and electrical panels), and use (e.g. home appliances, such as electric blankets, shavers, and televisions) of electrical energy is associated with the production of weak electric and magnetic fields (EMF) which oscillate 50 (Europe) or 60 (USA) times per second (power-line frequency), falling in the extremely-low frequency (ELF) region of the electromagnetic spectrum. Epidemiological reports suggest a possible association between exposure to ELF-EMF and an increased risk of cancer (e.g. childhood acute leukaemia). Benzene is an established human leukomogen. This xenobiotic, which is unlikely to be the ultimate carcinogen, is metabolized in the liver to its primary metabolite phenol, which is hydroxylated to hydroquinone (1,4-benzenediol) and 1,2,4-benzenetriol. In this in vitro approach, to test the genotoxic and / or co-genotoxic potency of ELF-EMF, the cytokinesis block micronucleus (MN) method with Jurkat cells has been used. A 50 Hz magnetic field (MF) of 5 mT field strength was applied for different length of time (from 1 to 24 h), either alone or with benzene, 1,4-benzenediol, or 1,2,4-benzenetriol. Our preliminary results show that, after 24 h exposure, the frequency of micronucleated cells in MF-exposed cultures is 1.9 fold higher than in sham-exposed (control) cultures. Benzene exposure does not show any cytogenetic activity, whereas 1,4-benzenediol or 1,2,4-benzenetriol alone significantly affect the number of MN in Jurkat cells, as compared to untreated cultures. Moreover, co-exposure to ELF-MF does not seem to affect the frequency of micronuclei induced by benzene, 1,4-benzenediol, or 1,2,4-benzenetriol.
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PMID:Micronucleus induction in cells co-exposed in vitro to 50 Hz magnetic field and benzene, 1,4-benzenediol (hydroquinone) or 1,2,4-benzenetriol. 1459 48

Multidrug resistance (MDR) is a naturally occurring defense phenomenon by which cells battle against chemically foreign substances (xenobiotics), including some cytotoxic drugs. Membrane transporter hyperactivity is a major contributor to MDR and is the primary target of both diagnostic and therapeutic interventions. Multi-xenobiotic resistance can be exploited as several fluorescent indicator probes are extruded by the same drug transporters, making it possible to quantitatively measure MDR activity in cell lines and clinical samples by flow cytometry. The literature on MDR is reported in a number of different formats, making it difficult to compare data from various groups. This article will briefly review the pathomechanism, then focus upon the diagnostic approach, the interpretation of results from clinical samples and correlations with other variables. The authors believe that a standardized MDR assay, as well as a suitable monitoring test, may become a prognostic marker in several types of leukemia.
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PMID:Progress in defining multidrug resistance in leukemia. 1499 7

Leukemia is the most common malignancy in children. The inter-individual variation in the capacity of xenobiotic metabolizing and DNA repair was shown to modify somatic mutation burden in the context of environmental exposure and determine genetic susceptibility to malignancies. In this paper, studies on polymorphisms of metabolic enzymes and DNA repair and, susceptibility to childhood leukemia are reviewed.
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PMID:[Study on polymorphisms in metabolic enzyme genes, DNA repair genes and individual susceptibility to childhood leukemia]. 1561

The present work focused on the study of the secretory activity of pre-B acute lymphoblastic leukaemia (ALL) cells harvested from bone marrow (BM) and peripheral blood (PB) in 16 children. The basal and cytokine (SDF-1, GM-CSF, bFGF, VEGF)-stimulated secretions of gelatinases 2 and 9 (MMPs-2 and -9) and expression of their genes were monitored by zymography and RT-PCR, respectively. A wide heterogeneity was found in the secretory capacities of these cells. The basal secretion of MMP-9 was more frequently observed than that of MMP-2 in both cell types. The cytokines VEGF and bFGF were found to induce predominant stimulatory effects on the MMP-2 secretion. In contrast, GM-CSF was shown to exert a more pronounced activation of the MMP-9 production. Experiments using inhibitors of metabolic pathways (U0126, LY294002 and SN50) revealed that the secretion of MMP-9 was mediated through PI3/MEK1 kinases. The MMP-2 secretion appeared to be however, stimulated through a different metabolic pathway. The microfluorimetric approach showed that the basal and stimulated secretions of MMPs-2 and -9 depended on the extracellular calcium pool. The cytokines VEGF and bFGF represent potent factors increasing the intracellular calcium concentration with similar kinetics. In contrast, GM-CSF was found to activate a verapamil-sensitive efflux of indo-1 from cytosol suggesting that this cytokine could be responsible for the activation of xenobiotic membrane transporters. Experiments using the trypan blue exclusion test demonstrated that bFGF, in contrast to VEGF and GM-CSF, markedly augmented pre-B ALL cell survival. Further investigations into a possible correlation between the plasma concentrations of MMP-2 and -9, VEGF, bFGF and GM-CSF, and the poor evolution of pre-B ALL in children could have valuable diagnostic implications.
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PMID:Spontaneous and cytokine-evoked production of matrix metalloproteinases by bone marrow and peripheral blood pre-B cells in childhood acute lymphoblastic leukaemia. 1626 64

Cancer affects 1 in every 500 children before the age of 14. Little is known about the etiology of this heterogeneous group of diseases despite the fact that they constitute the major cause of death by disease among this population. Because of its relatively higher prevalence, most of the work done in pediatric oncogenetics has been focused on leukemias, particularly acute lymphoblastic leukemia (ALL). Although it is now well accepted that genetic variations play a significant role in determining individual's cancer susceptibility, few studies have explored genetic susceptibility to childhood leukemia with respect to polymorphisms. The main biological mechanisms contributing to cancer susceptibility can be grouped into broad categories : (1) cellular growth and differentiation, (2) DNA replication and repair, (3) xenobiotic metabolism, (4) apoptosis, (5) oxidative stress response and (6) cell cycle. To evaluate whether candidate genes in these pathways are involved in childhood leukemogenesis, we conducted association studies. We showed that leukemogenesis in children may be associated with genetic variants and that the combination of genotypes seems to be more predictive of risk than either of them independently. These results indicate that the genetic investigation of several enzymes (or metabolic pathways) is needed to explain the physiopathology of childhood leukemia because of the complexity of the environment and that of the inter-individual variability in cancer susceptibility.
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PMID:[Childhood leukemia: a genetic disease!]. 1802 9


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