72 results on '"Elford HL"'
Search Results
2. Synergistic growth inhibitory and differentiating effects of trimidox and tiazofurin in human promyelocytic leukemia HL-60 cells
- Author
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Szekeres, T, primary, Fritzer, M, additional, Strobl, H, additional, Gharehbaghi, K, additional, Findenig, G, additional, Elford, HL, additional, Lhotka, C, additional, Schoen, HJ, additional, and Jayaram, HN, additional
- Published
- 1994
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3. A phase I and pharmacokinetic study of didox administered by 36 hour infusion. The Cancer Research Campaign Phase I/II Clinical Trials Committee.
- Author
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Carmichael, J, Cantwell, BMJ, Mannix, KA, Veale, D, Elford, HL, Blackie, R, Kerr, DJ, Kaye, SB, Harris, AL, Cantwell, B M, Mannix, K A, Elford, H L, Kerr, D J, Kaye, S B, and Harris, A L
- Published
- 1990
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4. A phase 1 and pharmacokinetic study of didox: a ribonucleotide reductase inhibitor.
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Veale, D, Carmichael, J, Cantwell, BM, Elford, HL, Blackie, R, Kerr, DJ, Kaye, SB, Harris, AL, Cantwell, B M, Elford, H L, Kerr, D J, Kaye, S B, and Harris, A L
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- 1988
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5. Targeting the Cell Cycle, RRM2 and NF-κB for the Treatment of Breast Cancers.
- Author
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Sultana N, Elford HL, and Faridi JS
- Abstract
A hallmark of cancer is the dysregulation of the cell cycle. The CDK4/6 inhibitor palbociclib is approved for treating advanced estrogen-receptor-positive breast cancer, but its success is limited by the development of acquired resistance owing to long-term therapy despite promising clinical outcomes. This situation necessitates the development of potential combination strategies. Here, we report that didox, an inhibitor of ribonucleotide reductase in combination with palbociclib, can overcome palbociclib resistance in ER-positive and ER-negative breast cancers. This study shows didox downregulates an element of the cell cycle checkpoint, cyclin D1, accompanied by a reduction in NF-κB activity in vitro and tumor growth inhibition of palbociclib-resistant ER positive breast cancer tumor growth in vivo. Furthermore, didox induces cell cycle arrest at G1 as well as reduces ROS generated by on-target effects of palbociclib on the cell cycle. Our current study also reports that the CCND1 and RRM2 upregulation associated with palbociclib-resistant breast cancers decreases upon ribonucleotide reductase inhibition. Our data present a novel and promising biomarker-driven combination therapeutic approach for the treatment of ER-positive and ER-negative breast cancers that involves the inhibition of the CDK4/6-cyclinD1/pRb cell cycle axis that merits further clinical investigation in human models.
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- 2024
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6. Molecular Targeting of RRM2, NF-κB, and Mutant TP53 for the Treatment of Triple-Negative Breast Cancer.
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Wilson EA, Sultana N, Shah KN, Elford HL, and Faridi JS
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- Animals, Apoptosis, Cell Proliferation, Female, Humans, Mice, Mice, Nude, Signal Transduction, Triple Negative Breast Neoplasms pathology, Molecular Targeted Therapy methods, NF-kappa B metabolism, Ribonucleoside Diphosphate Reductase metabolism, Triple Negative Breast Neoplasms genetics, Tumor Suppressor Protein p53 metabolism
- Abstract
Doxorubicin and other anthracycline derivatives are frequently used as part of the adjuvant chemotherapy regimen for triple-negative breast cancer (TNBC). Although effective, doxorubicin is known for its off-target and toxic side effect profile, particularly with respect to the myocardium, often resulting in left ventricular (LV) dysfunction and congestive heart failure when used at cumulative doses exceeding 400 mg/m
2 Previously, we have observed that the ribonucleotide reductase subunit M2 (RRM2) is significantly overexpressed in estrogen receptor (ER)-negative cells as compared with ER-positive breast cancer cells. Here, we inhibited RRM2 in ER-negative breast cancer cells as a target for therapy in this difficult-to-treat population. We observed that through the use of didox, a ribonucleotide reductase inhibitor, the reduction in RRM2 was accompanied by reduced NF-κB activity in vitro When didox was used in combination with doxorubicin, we observed significant downregulation of NF-κB proteins accompanied by reduced TNBC cell proliferation. As well, we observed that protein levels of mutant p53 were significantly reduced by didox or combination therapy in vitro Xenograft studies showed that combination therapy was found to be synergistic in vivo , resulting in a significantly reduced tumor volume as compared with doxorubicin monotherapy. In addition, the use of didox was also found to ameliorate the toxic myocardial effects of doxorubicin in vivo as measured by heart mass, LV diameter, and serum troponin T levels. The data present a novel and promising approach for the treatment of TNBC that merits further clinical evaluation in humans., (©2021 American Association for Cancer Research.)- Published
- 2021
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7. Didox (3,4-dihydroxybenzohydroxamic acid) reduces the vascular inflammation induced by acute intravascular hemolysis.
- Author
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Silva JAF, Gotardo ÉMF, Chweih H, Miguel LI, Ferreira WA Jr, Hedlund B, Elford HL, Leonardo FC, Costa FF, and Conran N
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- Humans, Inflammation etiology, Blood Vessels pathology, Hemolysis, Hydroxamic Acids therapeutic use, Inflammation drug therapy
- Abstract
Competing Interests: Declaration of competing interest Howard L. Elford, Ph.D.: Equity ownership in Molecules for Health Inc. (Didox).
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- 2020
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8. Didox (3,4-dihydroxybenzohydroxamic acid) suppresses IgE-mediated mast cell activation through attenuation of NFκB and AP-1 transcription.
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McLeod JJA, Caslin HL, Spence AJ, Kolawole EM, Qayum AA, Paranjape A, Taruselli M, Haque TT, Kiwanuka KN, Elford HL, and Ryan JJ
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- Acetylcysteine pharmacology, Animals, Bone Marrow Cells immunology, Catalase biosynthesis, Cell Degranulation drug effects, Cells, Cultured, Chemokine CCL3 biosynthesis, Hypersensitivity immunology, Interleukin-13 biosynthesis, Interleukin-6 biosynthesis, Mast Cells drug effects, Mice, Mice, Inbred C57BL, Oxidative Stress drug effects, Oxidative Stress immunology, Reactive Oxygen Species metabolism, Superoxide Dismutase biosynthesis, Transcription, Genetic drug effects, Tumor Necrosis Factor-alpha biosynthesis, Anti-Inflammatory Agents pharmacology, Antioxidants pharmacology, Hydroxamic Acids pharmacology, Hypersensitivity drug therapy, Immunoglobulin E immunology, Mast Cells immunology, NF-kappa B genetics, Transcription Factor AP-1 genetics
- Abstract
Mast cell activation via the high-affinity IgE receptor (FcεRI) elicits production of inflammatory mediators central to allergic disease. As a synthetic antioxidant and a potent ribonucleotide reductase (RNR) inhibitor, Didox (3,4-dihyroxybenzohydroxamic acid) has been tested in clinical trials for cancer and is an attractive therapeutic for inflammatory disease. We found that Didox treatment of mouse bone marrow-derived mast cells (BMMC) reduced IgE-stimulated degranulation and cytokine production, including IL-6, IL-13, TNF and MIP-1a (CCL3). These effects were consistent using BMMC of different genetic backgrounds and peritoneal mast cells. While the RNR inhibitor hydroxyurea had little or no effect on IgE-mediated function, high concentrations of the antioxidant N-acetylcysteine mimicked Didox-mediated suppression. Furthermore, Didox increased expression of the antioxidant genes superoxide dismutase and catalase, and suppressed DCFH-DA fluorescence, indicating reduced reactive oxygen species production. Didox effects were not due to changes in FcεRI expression or cell viability, suggesting it inhibits signaling required for inflammatory cytokine production. In support of this, we found that Didox reduced FcεRI-mediated AP-1 and NFκB transcriptional activity. Finally, Didox suppressed mast cell-dependent, IgE-mediated passive systemic anaphylaxis in vivo. These data demonstrate the potential use for Didox asa means of antagonizing mast cell responses in allergic disease., (Copyright © 2017 Elsevier Inc. All rights reserved.)
- Published
- 2017
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9. Didox (3,4-dihydroxybenzohydroxamic acid) suppresses IL-33-induced cytokine production in primary mouse mast cells.
- Author
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Caslin HL, McLeod JJA, Spence AJ, Qayum AA, Kolawole EM, Taruselli MT, Paranjape A, Elford HL, and Ryan JJ
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- Acetylcysteine pharmacology, Animals, Bone Marrow Cells cytology, Bone Marrow Cells drug effects, Bone Marrow Cells immunology, Chemokine CCL3 antagonists & inhibitors, Chemokine CCL3 genetics, Chemokine CCL3 immunology, Female, Gene Expression Regulation immunology, Genes, Reporter, Hydroxyurea pharmacology, Interleukin-13 antagonists & inhibitors, Interleukin-13 genetics, Interleukin-13 immunology, Interleukin-33 antagonists & inhibitors, Lipopolysaccharides pharmacology, Luciferases genetics, Luciferases immunology, Male, Mast Cells cytology, Mast Cells immunology, Mice, Mice, Inbred C57BL, NF-kappa B antagonists & inhibitors, NF-kappa B genetics, NF-kappa B immunology, Primary Cell Culture, Signal Transduction, Transcription Factor AP-1 antagonists & inhibitors, Transcription Factor AP-1 genetics, Transcription Factor AP-1 immunology, Tumor Necrosis Factor-alpha antagonists & inhibitors, Tumor Necrosis Factor-alpha genetics, Tumor Necrosis Factor-alpha immunology, Gene Expression Regulation drug effects, Hydroxamic Acids pharmacology, Immunosuppressive Agents pharmacology, Interleukin-33 pharmacology, Mast Cells drug effects
- Abstract
While IgE is considered the primary mediator of mast cell activation, IL-33 contributes substantially in asthma, allergic rhinitis, and atopic dermatitis. To develop effective treatments for allergic disease, it is important to understand the role of therapeutic agents on IL-33 activation. We examined the effect of Didox (3,4-dihydroxybenzohydroxamic acid), an antioxidant and ribonucleotide reductase (RNR) inhibitor, on IL-33-mediated mast cell activation. Didox suppressed IL-6, IL-13, TNF, and MIP-1α (CCL3) production in bone marrow derived mast cells following IL-33 activation. This suppression was observed in different genetic backgrounds and extended to peritoneal mast cells. The antioxidant N-acetylcysteine mimicked the suppression of Didox, albeit at a much higher dose, while the RNR inhibitor hydroxyurea had no effect. Didox substantially suppressed IL-33-mediated NFκB and AP-1 transcriptional activities. These results suggest that Didox attenuates IL-33-induced mast cell activation and should be further studied as a potential therapeutic agent for inflammatory diseases involving IL-33., (Copyright © 2017 Elsevier Inc. All rights reserved.)
- Published
- 2017
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10. Targeting Ribonucleotide Reductase M2 and NF-κB Activation with Didox to Circumvent Tamoxifen Resistance in Breast Cancer.
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Shah KN, Wilson EA, Malla R, Elford HL, and Faridi JS
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- Animals, Antineoplastic Agents pharmacology, Blotting, Western, Breast Neoplasms genetics, Breast Neoplasms metabolism, Cell Line, Tumor, Cell Movement drug effects, Cell Movement genetics, Cell Proliferation drug effects, Cell Proliferation genetics, Drug Synergism, ErbB Receptors metabolism, Estrogen Receptor alpha genetics, Estrogen Receptor alpha metabolism, Humans, Kaplan-Meier Estimate, MCF-7 Cells, Mice, Nude, NF-kappa B metabolism, RNA Interference, Reverse Transcriptase Polymerase Chain Reaction, Ribonucleoside Diphosphate Reductase genetics, Ribonucleoside Diphosphate Reductase metabolism, Signal Transduction drug effects, Xenograft Model Antitumor Assays, Breast Neoplasms drug therapy, Drug Resistance, Neoplasm drug effects, Hydroxamic Acids pharmacology, NF-kappa B antagonists & inhibitors, Ribonucleoside Diphosphate Reductase antagonists & inhibitors, Tamoxifen pharmacology
- Abstract
Tamoxifen is widely used as an adjuvant therapy for patients with estrogen receptor (ERα)-positive tumors. However, the clinical benefit is often limited because of the emergence of drug resistance. In this study, overexpression of ribonucleotide reductase M2 (RRM2) in MCF-7 breast cancer cells resulted in a reduction in the effectiveness of tamoxifen, through downregulation of ERα66 and upregulation of the 36-kDa variant of ER (ERα36). We identified that NF-κB, HIF1α, and MAPK/JNK are the major pathways that are affected by RRM2 overexpression and result in increased NF-κB activity and increased protein levels of EGFR, HER2, IKKs, Bcl-2, RelB, and p50. RRM2-overexpressing cells also exhibited higher migratory and invasive properties. Through time-lapse microscopy and protein profiling studies of tamoxifen-treated MCF-7 and T-47D cells, we have identified that RRM2, along with other key proteins, is altered during the emergence of acquired tamoxifen resistance. Inhibition of RRM2 using siRRM2 or the ribonucleotide reductase (RR) inhibitor didox not only eradicated and effectively prevented the emergence of tamoxifen-resistant populations but also led to the reversal of many of the proteins altered during the process of acquired tamoxifen resistance. Because didox also appears to be a potent inhibitor of NF-κB activation, combining didox with tamoxifen treatment cooperatively reverses ER-α alterations and inhibits NF-κB activation. Finally, inhibition of RRM2 by didox reversed tamoxifen-resistant in vivo tumor growth and decreased in vitro migratory and invasive properties, revealing a beneficial effect of combination therapy that includes RRM2 inhibition to delay or abrogate tamoxifen resistance., (©2015 American Association for Cancer Research.)
- Published
- 2015
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11. The efficacy of the ribonucleotide reductase inhibitor Didox in preclinical models of AML.
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Cook GJ, Caudell DL, Elford HL, and Pardee TS
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- Adult, Aged, Aged, 80 and over, Animals, Antineoplastic Agents administration & dosage, Antineoplastic Agents pharmacology, Apoptosis drug effects, DNA Damage drug effects, Disease Models, Animal, Drug Evaluation, Preclinical, Drug Resistance, Neoplasm, Enzyme Inhibitors administration & dosage, Female, Hematopoietic Stem Cells drug effects, Hematopoietic Stem Cells metabolism, Humans, Hydroxamic Acids administration & dosage, Karyotype, Leukemia, Myeloid, Acute genetics, Leukemia, Myeloid, Acute metabolism, Leukemia, Myeloid, Acute mortality, Male, Mice, Mice, Inbred C57BL, Middle Aged, Ribonucleotide Reductases antagonists & inhibitors, Signal Transduction drug effects, Tumor Stem Cell Assay, Tumor Suppressor Protein p53 metabolism, Enzyme Inhibitors pharmacology, Hydroxamic Acids pharmacology, Leukemia, Myeloid, Acute drug therapy
- Abstract
Acute Myeloid Leukemia (AML) is an aggressive malignancy which leads to marrow failure, and ultimately death. There is a desperate need for new therapeutics for these patients. Ribonucleotide reductase (RR) is the rate limiting enzyme in DNA synthesis. Didox (3,4-Dihydroxybenzohydroxamic acid) is a novel RR inhibitor noted to be more potent than hydroxyurea. In this report we detail the activity and toxicity of Didox in preclinical models of AML. RR was present in all AML cell lines and primary patient samples tested. Didox was active against all human and murine AML lines tested with IC50 values in the low micromolar range (mean IC50 37 µM [range 25.89-52.70 µM]). It was active against primary patient samples at concentrations that did not affect normal hematopoietic stem cells (HSCs). Didox exposure resulted in DNA damage and p53 induction culminating in apoptosis. In syngeneic, therapy-resistant AML models, single agent Didox treatment resulted in a significant reduction in leukemia burden and a survival benefit. Didox was well tolerated, as marrow from treated animals was morphologically indistinguishable from controls. Didox exposure at levels that impaired leukemia growth did not inhibit normal HSC engraftment. In summary, Didox was well tolerated and effective against preclinical models of AML.
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- 2014
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12. Paradoxical response to prophylactic Didox (N-3, 4 trihydroxybenzamide) treatment in murine cytomegalovirus-infected mice.
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Go V, Tang-Feldman YJ, Lochhead SR, Lochhead GR, Yu CQ, Elford HL, Inayat MS, Oakley OR, and Pomeroy C
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- Animals, Antineoplastic Agents, Antiviral Agents pharmacology, Cell Proliferation drug effects, Cells, Cultured, Cytokines, Enzyme-Linked Immunosorbent Assay, Female, Fibroblasts immunology, Fibroblasts virology, Herpesviridae Infections immunology, Herpesviridae Infections virology, Hydroxamic Acids, Liver cytology, Liver immunology, Liver virology, Lymphocyte Activation drug effects, Lymphocyte Activation immunology, Mice, Mice, Inbred BALB C, Muromegalovirus growth & development, Muromegalovirus immunology, Real-Time Polymerase Chain Reaction, Spleen cytology, Spleen immunology, Spleen virology, Treatment Failure, Viral Load, Viral Plaque Assay, Virus Replication, Fibroblasts drug effects, Herpesviridae Infections drug therapy, Liver drug effects, Muromegalovirus drug effects, Spleen drug effects
- Abstract
Background: In this study, we investigated the effect of Didox (DX) on the pathogenicity of and host responses to murine cytomegalovirus (MCMV) infection., Methods: In vitro efficacy of DX against MCMV was determined using plaque reduction assays. For in vivo studies, mice infected with a sublethal dose (10(4) PFU) of MCMV were treated daily with DX (200 mg/kg) using either a prophylactic or delayed protocol. At predetermined intervals, target organs were removed for histopathology. Cytokine transcription and viral load were performed using real-time PCR. Serum cytokine levels were determined by ELISA, and T-cell markers by real-time PCR., Results: DX (0.5-50 μM) inhibited MCMV plaque formation in vitro. However, in vivo, prophylactic DX treatment did not decrease viral load and prolonged hepatic proinflammatory cytokine transcription at days 3 and 5 post-infection, which corresponded with more severe histopathological changes observed in the liver. Significant CD8(+) T-cell marker suppression was seen, in accordance with DX-induced inhibition of lymphocyte proliferation observed in vitro. DX prolonged the recovery of MCMV-infected mice when given after infection was established., Conclusions: Despite promising MCMV inhibition in vitro, DX had no beneficial effect on MCMV disease in our model and paradoxically had adverse effects when administered prophylactically. The lack of correlation between in vitro activity and in vivo efficacy emphasizes the importance of selecting appropriate antiviral targets and of using animal models when testing new drugs.
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- 2011
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13. Inhibition of allogeneic inflammatory responses by the Ribonucleotide Reductase Inhibitors, Didox and Trimidox.
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Inayat MS, El-Amouri IS, Bani-Ahmad M, Elford HL, Gallicchio VS, and Oakley OR
- Abstract
Background: Graft-versus-host disease is the single most important obstacle facing successful allogeneic stem cell transplantation (SCT). Even with current immunosuppressive therapies, morbidity and mortality rates are high. Current therapies including cyclosporine A (CyA) and related compounds target IL-2 signaling. However, although these compounds offer great benefit, they are also associated with multiple toxicities. Therefore, new compounds with a greater efficacy and reduced toxicity are needed to enable us to overcome this hurdle., Methods: The allogeneic mixed lymphocyte reaction (MLR) is a unique ex vivo method to study a drug's action on the initial events resulting in T-cell activation and proliferation, synonymous to the initial stages of tissue and organ destruction by T-cell responses in organ rejection and Graft-versus-host disease. Using this approach, we examined the effectiveness of two ribonucleotide reductase inhibitors (RRI), Didox and Trimidox, to inhibit T-cell activation and proliferation., Results: The compounds caused a marked reduction in the proliferative responses of T-cells, which is also accompanied by decreased secretion of cytokines IL-6, IFN-gamma, TNF-alpha, IL-2, IL-13, IL-10 and IL-4., Conclusions: In conclusion, these data provide critical information to justify further investigation into the potential use of these compounds post allogeneic bone marrow transplantation to alleviate graft-versus-host disease thereby achieving better outcomes.
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- 2010
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14. Ribonucleotide reductase inhibitors reduce atherosclerosis in a double-injury rabbit model.
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Gallaugher LD, Henry JC, Kearns PN, Elford HL, Bergdall VK, and Cardounel AJ
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- Animals, Rabbits, Atherosclerosis prevention & control, Disease Models, Animal, Enzyme Inhibitors pharmacology, Hydroxamic Acids pharmacology, Hydroxyurea pharmacology, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Atheroproliferative disorders such as atherosclerosis are an important health problem and one of the leading causes of morbidity and mortality in the United States. Minimally invasive therapeutic procedures, including angioplasty with stent deployment, are used frequently for obstructive coronary artery disease. However, restenosis, a proliferative vascular response, is a common sequela to this procedure. The current study investigated the effect of inhibiting ribonucleotide reductase (RR), an enzyme necessary for cellular proliferation, in an attempt to ameliorate the proliferative response. Two RR inhibitors, didox and hydroxyurea, were chosen for their potent antiproliferative properties. Studies were carried out by using a double-injury rabbit model, in which endothelial denudation was followed by the administration of a high-fat diet. At 4 wk after initial endothelial denudation, the developing atherosclerotic lesion was subjected to transluminal balloon dilation to simulate clinical intervention with percutaneous transluminal angioplasty. The degree of restenosis and atheroproliferation was assessed at 8 wk. Histologic evaluation of the lesion demonstrated that treatment with didox and hydroxyurea significantly decreased lesion area and lumen loss. These results suggest that RR inhibition may be an effective new tool for the treatment of atheroproliferative disorders.
- Published
- 2009
15. Gallic acid inhibits ribonucleotide reductase and cyclooxygenases in human HL-60 promyelocytic leukemia cells.
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Madlener S, Illmer C, Horvath Z, Saiko P, Losert A, Herbacek I, Grusch M, Elford HL, Krupitza G, Bernhaus A, Fritzer-Szekeres M, and Szekeres T
- Subjects
- Adenosine Triphosphate metabolism, Apoptosis drug effects, Benzamidines chemistry, Benzamidines pharmacology, Cell Cycle drug effects, Cell Proliferation drug effects, Cell Survival drug effects, Cytidine Triphosphate metabolism, Dose-Response Relationship, Drug, Enzyme Inhibitors chemistry, Enzyme Inhibitors pharmacology, Gallic Acid chemistry, Guanosine Triphosphate metabolism, HL-60 Cells, Humans, Leukemia, Promyelocytic, Acute enzymology, Leukemia, Promyelocytic, Acute metabolism, Leukemia, Promyelocytic, Acute pathology, Molecular Structure, Ribonucleotide Reductases metabolism, Thymine Nucleotides metabolism, Cyclooxygenase Inhibitors pharmacology, Gallic Acid pharmacology, Prostaglandin-Endoperoxide Synthases metabolism, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Gallic acid (GA) is a naturally occurring polyhydroxyphenolic compound and an excellent free radical scavenger. In this study, we examined its cytotoxic and biochemical effects on the human HL-60 promyelocytic leukemia cell line. GA caused a significant imbalance of deoxynucleosidetriphosphate (dNTP) pool sizes, indicating ribonucleotide reductase inhibition. Moreover, GA induced dose-dependent apoptosis in HL-60 cells (80microM GA led to the induction of apoptosis in 39% of cells) and attenuated progression from G0/G1 to the S phase of the cell cycle (60microM GA doubled the number of cells in G0/G1 phase from 22 to 44% when compared to untreated controls). We further determined IC(50) values of 3.5 and 4.4nM for the inhibition of cyclooxygenases I and II, respectively. When cells were simultaneously treated with GA and trimidox, another inhibitor of RR, highly synergistic growth inhibitory effects could be observed. Taken together, we identified novel biochemical effects of GA which could be the basis for further preclinical and in vivo studies.
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- 2007
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16. Didox, a ribonucleotide reductase inhibitor, induces apoptosis and inhibits DNA repair in multiple myeloma cells.
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Raje N, Kumar S, Hideshima T, Ishitsuka K, Yasui H, Chhetri S, Vallet S, Vonescu E, Shiraishi N, Kiziltepe T, Elford HL, Munshi NC, and Anderson KC
- Subjects
- Antineoplastic Agents, Alkylating pharmacology, Caspases physiology, Cell Cycle drug effects, Cell Survival drug effects, DNA Repair genetics, Dose-Response Relationship, Drug, Down-Regulation drug effects, Drug Evaluation, Preclinical, Drug Synergism, Enzyme Inhibitors pharmacology, Gene Expression Regulation, Neoplastic drug effects, Humans, Melphalan pharmacology, Multiple Myeloma genetics, Multiple Myeloma metabolism, Neoplasm Proteins metabolism, Proto-Oncogene Proteins c-bcl-2 metabolism, Ribonucleotide Reductases antagonists & inhibitors, Tumor Cells, Cultured, Antineoplastic Agents pharmacology, Apoptosis drug effects, DNA Repair drug effects, Hydroxamic Acids pharmacology, Multiple Myeloma pathology
- Abstract
Ribonucleotide reductase (RR) is the enzyme that catalyses the rate-limiting step in DNA synthesis, the production of deoxynucleotides. RR activity is markedly elevated in tumour tissue and is crucial for cell division. It is therefore an excellent target for cancer chemotherapy. This study examined the anti-myeloma activity of Didox (3,4-Dihydroxybenzohydroxamic acid), a novel RR inhibitor (RRI). Our data showed that Didox induced caspase-dependent multiple myeloma (MM) cell apoptosis. Didox, unlike other RRIs that mainly target the pyrimidine metabolism pathway, targets both purine and pyrimidine metabolism pathways in MM, as demonstrated by transcriptional profiling using the Affymetrix U133A 2.0 gene chip. Specifically, a >or=2-fold downregulation of genes in these anabolic pathways was shown as early as 12 h after exposure to Didox. Furthermore, apoptosis was accompanied by downregulation of bcl family proteins including bcl-2, bcl(xl), and XIAP. Importantly, RR M1 component transcript was also downregulated, associated with decreased protein expression. Genes involved in DNA repair mechanisms, specifically RAD 51 homologue, were also downregulated. As Didox acts on MM cells by inhibiting DNA synthesis and repair, combination studies with melphalan, an agent commonly used in MM, were performed. A strong in vitro synergism was shown, with combination indices of <0.7 as determined by the Chou-Talalay method. These studies therefore provide the preclinical rationale for evaluation of Didox, alone and in combination with DNA-damaging agents, to improve patient outcome in MM.
- Published
- 2006
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17. Potentiation of the activity of cisplatin and cyclophosphamide by trimidox, a novel ribonucleotide reductase inhibitor, in leukemia-bearing mice.
- Author
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Novotny L, Rauko P, Liska J, Elford HL, and Szekeres T
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- Animals, Cisplatin administration & dosage, Cyclophosphamide administration & dosage, Drug Synergism, Male, Mice, Mice, Inbred DBA, Antineoplastic Combined Chemotherapy Protocols therapeutic use, Benzamidines administration & dosage, Enzyme Inhibitors administration & dosage, Leukemia L1210 drug therapy, Leukemia P388 drug therapy, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
We describe the use of the new ribonucleotide reductase inhibitor, trimidox (TDX), in combination chemotherapy under in vitro and in vivo conditions with cisplatin and cyclophosphamide. In vitro, the combination of TDX and cisplatin was tested in L1210 cells. The combination caused concentration dependent antagonistic or additive effects. However, the combination of TDX-cisplatin-cyclophosphamide in vivo is highly synergistic in both, the L1210 and P388D1 leukemia mouse models. Both combinations, TDX with cisplatin or TDX with cyclophosphamide were also synergistic in the L1210 and P388D1 leukemia animal models.
- Published
- 2006
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18. Oxygen carriers: a selected review.
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Inayat MS, Bernard AC, Gallicchio VS, Garvy BA, Elford HL, and Oakley OR
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- Bacterial Infections, Blood microbiology, Blood Banks, Blood Component Transfusion, Blood Preservation methods, Blood Specimen Collection, Blood Substitutes pharmacology, Drug Design, Hemoglobins, Humans, Models, Chemical, Blood Substitutes chemistry, Blood Transfusion methods, Oxygen metabolism
- Abstract
The most common and widely transplanted tissue world wide is blood, which in 2000 resulted in the transfusion of 12.5 million units of blood in the US alone [Goodnough LT, Shander A, Brecher ME. Transfusion medicine: looking to the future. Lancet 2003;361:161-9]. The current use of donated blood products is relatively safe; however, there are inherent problems with allogeneic blood transfusions. The wide spread use of blood in procedures results in problems involving inadequate supply exacerbated in times of war and disasters and by the limited storage life of blood donations (30-42 days). Blood contamination due to patient pre-disposition, poor collection, sterilization, or storage is the second most common cause of death from transfusion in the US [Hillyer CD, Josephson CD, Blajchman MA, Vostal JG, Epstein JS, Goodman JL. Bacterial contamination of blood components: risks, strategies, and regulation: joint ASH and AABB educational session in transfusion medicine. Hematology (Am Soc Hematol Educ Program) 2003:575-89]. Blood is a complex tissue involved in a plethora of homeostatic roles, including immunity, wound healing and the transport of nourishment, electrolytes, hormones, vitamins, heat, oxygen and the removal of metabolic waste products. However, by far the principle role of blood transfusions is the replacement of red cell volume and the maintenance of oxygen levels within the circulation. Creation of investigational new drugs (INDs) which would function as oxygen carriers and prolong shelf life is now a very active arena of scientific research. Several such IND products are now in clinical trials. This article gives an easy to follow concise evaluation of major areas of focus and current testing for each type of blood substitution molecule.
- Published
- 2006
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19. Inhibition of ribonucleotide reductase reduces neointimal formation following balloon injury.
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Henry JC, Bonar MM, Kearns PN, Cui H, Mutchler MM, Martin MV, Orsini AR, Elford HL, Bush CA, Zweier JL, and Cardounel AJ
- Subjects
- Animals, Catheterization, Cell Movement drug effects, Cell Proliferation drug effects, Coronary Restenosis pathology, Flow Cytometry, Hydroxamic Acids pharmacology, Hydroxyurea pharmacology, Male, Muscle, Smooth, Vascular cytology, Muscle, Smooth, Vascular drug effects, Rats, Rats, Wistar, Coronary Restenosis prevention & control, Coronary Vessels injuries, Enzyme Inhibitors pharmacology, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Percutaneous transluminal coronary angioplasty (PTCA) has greatly benefited patients with occluded coronary arteries, but its benefits have been undermined by a high incidence of restenosis. The introduction of coronary stents has significantly improved the short and long term outcome but restenosis still occurs in approximately 15 to 30% of patients within 6 months. Research efforts are now being directed toward combination stenting and drug delivery. Among the therapeutic targets being pursued are agents that can impede smooth muscle cell migration and proliferation, as these processes are critical components of restenosis injury. We propose that inhibiting the conversion of ribonucleotides to deoxyribonucleotides will impede cell proliferation and, as such, limit the degree of restenosis. Therefore, we tested whether the potent ribonucleotide reductase inhibitors Didox (3,4-dihydroxybenzohydraxamic acid) and Imidate (ethyl-3,4,5-hydroxybenzimidate) can limit the neointimal proliferation associated with restenosis using a rat carotid model of balloon dilatation injury. Results demonstrated that both Didox and Imidate significantly reduced intimal thickening, resulting in a 71 and 62% decrease in the intima/media ratio, respectively. Similar efficacy was seen with the commercially available ribonucleotide reductase inhibitor hydroxyurea, demonstrating the importance of this enzyme in vascular remodeling. Results from cell proliferation studies suggest that the mechanism of protection is inhibition of smooth muscle cell (SMC) proliferation. In addition, Didox and Imidate (100 microM) are potent inhibitors of SMC migration, which may also contribute to their vascular protective effects. These results suggest that inhibition of ribonucleotide reductase may provide a potent strategy to prevent post-PTCA restenosis.
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- 2005
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20. Combination of inhibitors of lymphocyte activation (hydroxyurea, trimidox, and didox) and reverse transcriptase (didanosine) suppresses development of murine retrovirus-induced lymphoproliferative disease.
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Mayhew CN, Sumpter R, Inayat M, Cibull M, Phillips JD, Elford HL, and Gallicchio VS
- Subjects
- Animals, Antiviral Agents administration & dosage, B-Lymphocytes immunology, Benzamidines administration & dosage, Drug Therapy, Combination, Enzyme Inhibitors administration & dosage, Enzyme Inhibitors therapeutic use, Female, Hydroxamic Acids administration & dosage, Hydroxyurea administration & dosage, Leukemia Virus, Murine drug effects, Leukemia, Experimental drug therapy, Leukemia, Experimental virology, Lymphocyte Activation drug effects, Mice, Mice, Inbred C57BL, Murine Acquired Immunodeficiency Syndrome virology, Retroviridae Infections drug therapy, Retroviridae Infections virology, Ribonucleotide Reductases antagonists & inhibitors, Treatment Outcome, Tumor Virus Infections drug therapy, Tumor Virus Infections virology, Antiviral Agents therapeutic use, Benzamidines therapeutic use, Didanosine therapeutic use, Hydroxamic Acids therapeutic use, Hydroxyurea therapeutic use, Murine Acquired Immunodeficiency Syndrome drug therapy, Reverse Transcriptase Inhibitors therapeutic use
- Abstract
The ribonucleotide reductase inhibitor hydroxyurea (HU) has demonstrated some benefit as a component of drug cocktails for the treatment of HIV-1 infection. However, HU is notoriously myelosuppressive and often administered only as salvage therapy to patients with late-stage disease, potentially exacerbating the bone marrow toxicity of HU. In this report we have compared the antiviral effects of HU and two novel RR inhibitors trimidox (3,4,5-trihydroxybenzamidoxime) and didox (3,4-dihydroxybenzohydroxamic acid) in combination with didanosine (2,3-didoxyinosine; ddI) in the LPBM5 MuLV retrovirus model (murine AIDS). We also evaluated the effects of these drug combinations on the hematopoietic tissues of LPBM5 MuLV-infected animals. The combination of RR inhibitors and ddI was extremely effective (DX>TX>HU) in inhibiting development of retrovirus-induced disease (splenomegaly, hypergammaglobulinemia, activated B-splenocytes and loss of splenic architecture). In addition, relative levels of proviral DNA were significantly lower in combination drug-treated animals compared to infected controls. Evaluation of femur cellularity, numbers of marrow-derived myeloid progenitor cells (CFU-GM and BFU-E) and peripheral blood indices revealed that TX and DX in combination with ddI were well-tolerated. However, treatment with HU and ddI induced moderate myelosuppression. These data demonstrate that RR inhibitors in combination with ddI provide significant protection against retroviral disease in murine AIDS. Moreover, the novel RR inhibitors TX and DX appear to be more effective and less myelosuppressive than HU when administered with ddI in this model.
- Published
- 2005
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21. Synergistic cytotoxicity of the ribonucleotide reductase inhibitor didox (3,4-dihydroxy-benzohydroxamic acid) and the alkylating agent carmustine (BCNU) in 9L rat gliosarcoma cells and DAOY human medulloblastoma cells.
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Horvath Z, Höchtl T, Bauer W, Fritzer-Szekeres M, Elford HL, Szekeres T, and Tihan T
- Subjects
- Animals, Drug Interactions, Humans, Rats, Tumor Cells, Cultured, Antineoplastic Agents pharmacology, Antineoplastic Agents toxicity, Antineoplastic Agents, Alkylating pharmacology, Antineoplastic Agents, Alkylating toxicity, Brain Neoplasms pathology, Carmustine pharmacology, Carmustine toxicity, Cerebellar Neoplasms pathology, Gliosarcoma pathology, Hydroxamic Acids pharmacology, Hydroxamic Acids toxicity, Medulloblastoma pathology
- Abstract
Purpose: Ribonucleotide reductase (RR) is the rate-limiting enzyme of de novo DNA synthesis and has been shown to be upregulated linked with proliferation and malignant transformation. It was therefore identified as an excellent target for antitumor therapy. In the present study we investigated the biochemical and cytotoxic effects of didox, an inhibitor of RR, as a single agent and in combination with BCNU, an alkylating anticancer drug, in 9L rat gliosarcoma cells and DAOY human medulloblastoma cells., Methods: The effect of didox on the intracellular concentrations of deoxynucleosidetriphosphates (dNTPs) was studied in 9L cells. Pool sizes were determined by HPLC. In addition, the cytotoxic effects of didox and BCNU as single drugs and in equimolar combination were tested in 9L and in DAOY cells. Combination effects were determined according to the equation of Chou and Talalay. The expression of DNA repair-related genes was determined after exposure of 9L cells to BCNU, didox and a combination of the two compounds, using a cDNA array., Results: Incubation of 9L cells with 30 microM didox for 24 h significantly decreased the intracellular concentrations of the DNA precursors dCTP (61% of control) and dGTP (17% of control), and significantly increased the concentration of dATP (155% of control). This dNTP imbalance compromised DNA synthesis and repair and might therefore have been, at least in part, responsible for the highly synergistic cytotoxic effects seen when BCNU was used simultaneously with didox in 9L and in DAOY cells. With almost all combinations tested, highly synergistic effects were seen, as indicated by combination indices of <1 according to the equation of Chou and Talalay. In 9L cells, BCNU upregulated the expression of DNA repair-associated genes, whereas coincubation of the cells with didox reduced overexpression of some of these repair-related genes., Conclusion: A combination of BCNU and didox was proven to act in a synergistic manner in two cell lines, 9L rat gliosarcoma and DAOY human medulloblastoma cells. Further in vivo tests using these two compounds systemically and/or locally at the tumor site might be warranted.
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- 2004
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22. In vivo examination of hydroxyurea and the novel ribonucleotide reductase inhibitors trimidox and didox in combination with the reverse transcriptase inhibitor abacavir: suppression of retrovirus-induced immunodeficiency disease.
- Author
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Sumpter LR, Inayat MS, Yost EE, Duvall W, Hagan E, Mayhew CN, Elford HL, and Gallicchio VS
- Subjects
- Animals, Antiviral Agents pharmacology, Benzamidines therapeutic use, Dideoxynucleosides therapeutic use, Disease Models, Animal, Drug Therapy, Combination, Hematopoietic Stem Cells drug effects, Hydroxamic Acids therapeutic use, Hydroxyurea adverse effects, Hydroxyurea chemistry, Mice, Mice, Inbred C57BL, Murine Acquired Immunodeficiency Syndrome blood, Murine Acquired Immunodeficiency Syndrome immunology, Murine Acquired Immunodeficiency Syndrome pathology, Spleen pathology, Splenomegaly, Antiviral Agents therapeutic use, Bone Marrow Cells drug effects, Hydroxyurea therapeutic use, Murine Acquired Immunodeficiency Syndrome drug therapy, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Inhibition of ribonucleotide reductase (RR) has gained attention as a potential strategy for HIV-1 therapy through the success of hydroxyurea (HU) to potentiate the activity of the nucleoside reverse transcriptase inhibitor (NRTI) didanosine (ddI) in clinical trials. However, the use of HU has been limited by its development of hematopoietic toxicity. In this study, the novel RR inhibitors didox (DX; 3,4-dihydroxybenzohydroxamic acid), and trimidox (TX; 3,4,5-trihydroxybenzamidoxime) were evaluated along with HU for anti-retroviral efficacy in LPBM5-induced retro-viral disease (MAIDS) both as monotherapeutic regimens and in combination with the guanine containing NRTI abacavir (ABC). Anti-retroviral drug efficacy was determined by measuring inhibition of splenomegaly, hypergammaglobulinemia, and splenic levels of proviral DNA. In this study, all RRIs tested showed the ability to improve the efficacy of ABC in the MAIDS model by reducing splenomegaly, hypergammaglobulinemia, and splenic proviral DNA levels.
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- 2004
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23. Biochemical modulation of Ara-C effects by amidox, an inhibitor of ribonucleotide reductase in HL-60 promyelocytic human leukemia cells.
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Höchtl T, Horvath Z, Bauer W, Karl D, Saiko P, Elford HL, Fritzer-Szekeres M, and Szekeres T
- Subjects
- Arabinofuranosylcytosine Triphosphate metabolism, Cell Division drug effects, Colony-Forming Units Assay, Deoxyribonucleotides metabolism, Growth Inhibitors metabolism, HL-60 Cells, Humans, Antimetabolites, Antineoplastic pharmacology, Cytarabine pharmacology, Oximes pharmacology, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Amidox, a new polyhydroxy-substituted benzoic acid derivative, is a potent inhibitor of the enzyme ribonucleotide reductase (RR), which catalyses the de novo synthesis of DNA. RR is considered to be an excellent target for anti cancer chemotherapy. We investigated the biochemical and antineoplastic effects of amidox as a single agent and in combination with Ara-C in human HL-60 promyelocytic leukemia cells. Amidox inhibited the growth of HL-60 cells in a growth inhibition assay with an IC50 of 25 microM. In a soft agar colony forming assay, amidox yielded a 50% inhibition of colony formation at 13 microM. We also investigated the effects of amidox treatment on the formation of deoxynucleosidetriphosphates. Amidox (50 and 75 microM for 24 hours) could significantly decrease intracellular concentrations of dCTP, dATP and dGTP pools, whereas dTTP levels increased. We then tested the combination effects of amidox with Ara-C; this combination yielded additive cytotoxic effects both in growth inhibition and in soft agar colony formation assays. This effect was due to the increased formation of Ara-CTP, the active metabolite of Ara-C, after preincubation with amidox. Preincubation of HL-60 cells with 75 and 100 microM amidox for 24 hours caused an increase in the intracellular Ara-CTP concentrations by 576% and 1143%, respectively. Therefore amidox might offer an additional option for the treatment of leukemia and thus be further investigated in in vivo studies as a single agent and in combination with Ara-C.
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- 2004
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24. Suppression of retrovirus-induced immunodeficiency disease (murine AIDS) by trimidox and didox: novel ribonucleotide reductase inhibitors with less bone marrow toxicity than hydroxyurea.
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Mayhew CN, Mampuru LJ, Chendil D, Ahmed MM, Phillips JD, Greenberg RN, Elford HL, and Gallicchio VS
- Subjects
- Animals, Benzamidines chemistry, Benzamidines therapeutic use, DNA, Viral, Female, Femur cytology, Femur drug effects, Free Radical Scavengers chemistry, Free Radical Scavengers therapeutic use, Hematopoietic Stem Cells drug effects, Hydroxamic Acids chemistry, Hydroxamic Acids therapeutic use, Hydroxyurea chemistry, Hydroxyurea therapeutic use, Hypergammaglobulinemia drug therapy, Leukemia Virus, Murine genetics, Leukemia, Experimental blood, Leukemia, Experimental drug therapy, Leukemia, Experimental immunology, Mice, Mice, Inbred C57BL, Murine Acquired Immunodeficiency Syndrome blood, Murine Acquired Immunodeficiency Syndrome drug therapy, Murine Acquired Immunodeficiency Syndrome immunology, Proviruses genetics, Retroviridae Infections blood, Retroviridae Infections drug therapy, Retroviridae Infections immunology, Spleen pathology, Splenomegaly, Tumor Virus Infections blood, Tumor Virus Infections drug therapy, Tumor Virus Infections immunology, Benzamidines adverse effects, Bone Marrow Cells drug effects, Free Radical Scavengers adverse effects, Hydroxamic Acids adverse effects, Hydroxyurea adverse effects, Leukemia Virus, Murine drug effects, Leukemia, Experimental pathology, Murine Acquired Immunodeficiency Syndrome pathology, Retroviridae Infections pathology, Ribonucleotide Reductases antagonists & inhibitors, Tumor Virus Infections pathology
- Abstract
Recently, the use of the ribonucleotide reductase (RR) inhibitor hydroxyurea (HU) in combination with nucleoside analogs has gained attention as a potential strategy for anti-HIV-1 therapy. However, appeal for the long-term use of HU in HIV-1 infection may be limited by its propensity to induce hematopoietic toxicity. We report a comparison of the efficacy and bone marrow toxicity of HU (400 and 200 mg/kg/day) with the novel RR inhibitors and free radical-scavenging compounds didox (DX; 3,4-dihydroxybenzohydroxamic acid; 350 mg/kg/day) and trimidox (TX; 3,4,5-trihydroxybenzamidoxime; 175 mg/kg/day) in the murine AIDS (LPBM5 MuLV) model of retrovirus infection. Infected mice received daily drug treatment for 8 weeks. Efficacy was determined by measuring drug effects on retroviral-induced disease progression (i.e. development of splenomegaly and hypergammaglobulinemia) and by evaluating splenic levels of proviral DNA. Bone marrow toxicity was evaluated by measuring peripheral blood indices (WBC, hematocrit and reticulocyte counts), femoral cellularity and by determining the numbers of hematopoietic progenitor cells (CFU-GM, BFU-E) per femur and spleen. Compared to infected controls receiving no drug treatment, disease progression was significantly suppressed by TX, DX and HU. However, HU was associated with mortality and induced significant hematopoietic toxicity in a time- and dose-dependent manner. Conversely, TX and DX effectively inhibited retrovirus-induced disease but did not induce hematopoietic toxicity. These results suggest that due to their reduced hematopoietic toxicity and ability to inhibit disease progression in murine AIDS, TX and DX may offer effective alternatives to HU therapy in HIV-1 infection., (Copyright 2002 Elsevier Science B.V.)
- Published
- 2002
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25. Didox (a novel ribonucleotide reductase inhibitor) overcomes Bcl-2 mediated radiation resistance in prostate cancer cell line PC-3.
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Inayat MS, Chendil D, Mohiuddin M, Elford HL, Gallicchio VS, and Ahmed MM
- Subjects
- Apoptosis radiation effects, Cell Line, Cell Survival radiation effects, Combined Modality Therapy, Dose-Response Relationship, Drug, Dose-Response Relationship, Radiation, Gene Expression Regulation, Neoplastic radiation effects, Genetic Vectors, Humans, Male, Mitosis drug effects, Mitosis radiation effects, NF-kappa B drug effects, NF-kappa B radiation effects, Prostatic Neoplasms genetics, Prostatic Neoplasms metabolism, Proto-Oncogene Proteins drug effects, Proto-Oncogene Proteins radiation effects, Proto-Oncogene Proteins c-bcl-2 radiation effects, Radiation, Ionizing, Transfection, Tumor Cells, Cultured, bcl-2-Associated X Protein, Antineoplastic Agents therapeutic use, Hydroxamic Acids therapeutic use, Prostatic Neoplasms radiotherapy, Proto-Oncogene Proteins c-bcl-2 antagonists & inhibitors, Radiation Tolerance
- Abstract
In this study, we investigated the influence of Bcl-2 overexpression on the radiosensitizing potential of Didox (DX; 3,4-Dihydroxybenzohydroxamic acid), a novel ribonucleotide reductase inhibitor, in p53-null prostate cancer cell line PC-3. The PC-3 cells were transfected with vector alone or ectopically overexpressed with CMV-Bcl-2 construct. The effect of radiation (IR) or DX alone and in combination (pre and post IR exposure of DX) on cell survival was determined by colony-forming assay. The impact of these two treatments on the cell cycle was determined by flow cytometry. To further understand the molecular mechanism of DX-mediated radiosensitization, induction of pro-survival and pro-apoptotic factors were determined by Western blot and gel-shift assays respectively. When compared to PC-3/Bcl-2 cells (SF(2)=0.84; D(0)=437cGy), the PC-3/vector cells (SF(2)=0.4; D(0)=235cGy) were significantly sensitive to ionizing radiation (p<0.001). Exposure of DX at 5 microM concentration prior or post to radiation in both PC-3/vector and PC-3/Bcl-2 transfectants caused an increase in radiation enhancement ratios. A significant reduction in G(2)M phase was observed in cells exposed to DX post IR when compared to cells exposed to IR alone. Exposure to DX after radiation in PC-3/vector significantly abrogated radiation-induced Bcl-2 upregulation, with a concomitant induction of bax protein. In PC-3/Bcl-2 transfectants, DX exposure after IR caused an induction of bax protein. Gel shift assays indicated that in PC-3/vector cells when exposed to IR caused an induction of NFkappa-B activity however, DX down regulated the NFkappa-B activity. Radiation-induced NFkappa-B activity was abrogated in pre and post DX exposure in combination with IR. These findings indicate that DX mediates a potent radiosensitizing effect in p53 null prostate cancer cells by overcoming radiation induced NFkappa-B activity and Bcl-2 expression.
- Published
- 2002
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26. Trimidox, an inhibitor of ribonucleotide reductase, synergistically enhances the inhibition of colony formation by Ara-C in HL-60 human promyelocytic leukemia cells.
- Author
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Fritzer-Szekeres M, Salamon A, Grusch M, Horvath Z, Höchtl T, Steinbrugger R, Jäger W, Krupitza G, Elford HL, and Szekeres T
- Subjects
- Apoptosis, Arabinofuranosylcytosine Triphosphate metabolism, Cell Division drug effects, Cytarabine metabolism, DNA drug effects, DNA metabolism, Drug Screening Assays, Antitumor, Drug Synergism, HL-60 Cells, Humans, Leukemia, Promyelocytic, Acute, Nucleic Acid Synthesis Inhibitors metabolism, Benzamidines pharmacology, Cytarabine pharmacology, Enzyme Inhibitors pharmacology, Nucleic Acid Synthesis Inhibitors pharmacology, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Ribonucleotide reductase is the rate-limiting enzyme for the de novo synthesis of deoxynucleoside triphosphates and therefore represents a good target for cancer chemotherapy. Trimidox (3,4,5-trihydroxybenzamidoxime) was identified as a potent inhibitor of this enzyme and was shown to significantly decrease deoxycytidine triphosphate (dCTP) pools in HL-60 leukemia cells. We now investigated the ability of trimidox to increase the antitumor effect of 1-beta-D-arabinofuranosyl cytosine (Ara-C). Ara-C is phosphorylated by deoxycytidine kinase, which is subject to negative allosteric regulation by dCTP. Therefore, a decrease of dCTP may cause increased Ara-C phosphorylation and enhanced incorporation of Ara-C into DNA. Ara-C incorporation indeed increased 1.51- and 1.89-fold after preincubation with 75 and 100 microM trimidox, respectively. This was due to the significantly increased 1-beta-D-arabinofuranosyl cytosine triphosphate pools (1.9- and 2.5-fold) after preincubation with trimidox. We also investigated the effects of a combination of trimidox and Ara-C on the colony formation of HL-60 cells. A synergistic potentiation of the effect of Ara-C could be observed, when trimidox was added. Trimidox, which decreases intracellular deoxynucleoside triphosphate concentrations thus leading to apoptosis, enhanced the induction of apoptosis caused by Ara-C. We conclude, that trimidox is capable of synergistically enhancing the effects of Ara-C and therefore this drug combination might be further tested in animals.
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- 2002
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27. Activation of caspases and induction of apoptosis by novel ribonucleotide reductase inhibitors amidox and didox.
- Author
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Grusch M, Fritzer-Szekeres M, Fuhrmann G, Rosenberger G, Luxbacher C, Elford HL, Smid K, Peters GJ, Szekeres T, and Krupitza G
- Subjects
- Annexin A5 metabolism, Caspase 8, Caspase 9, DNA Fragmentation, Dose-Response Relationship, Drug, Enzyme Activation drug effects, Gelsolin metabolism, HL-60 Cells drug effects, HL-60 Cells enzymology, Humans, K562 Cells drug effects, K562 Cells enzymology, Phosphatidylserines metabolism, Pilot Projects, Poly(ADP-ribose) Polymerases metabolism, Apoptosis drug effects, Caspase Inhibitors, Caspases drug effects, Enzyme Inhibitors pharmacology, Hydroxamic Acids pharmacology, Neoplasm Proteins antagonists & inhibitors, Oximes pharmacology, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Objective: Amidox and didox are two polyhydroxy-substituted benzohydroxamic acid derivatives that belong to a new class of ribonucleotide reductase (RR) inhibitors. RR is the rate-limiting enzyme for de novo deoxyribonucleotide synthesis, and its activity is significantly increased in tumor cells in proportion to the proliferation rate. Therefore, RR is a target for antitumor therapy., Materials and Methods: HL-60 and K562 leukemia cells were treated with increasing doses of amidox and didox. Thereafter, the mode of cytotoxic drug action was determined by Hoechst 33258/propidium iodide (HO/PI) double staining, annexin binding, DNA fragmentation, and caspase activation. This was correlated to the decrease in dNTP levels. Staining with HO/PI and binding of fluorescein isothiocyanate-conjugated annexin V to externalized phosphatidylserine were used to quantify apoptosis., Results: Low doses of amidox or didox resulted in an increase of apoptotic HL-60 cells within 48 hours. Higher doses (50 microM amidox or 250 microM didox) led to rapid induction of apoptosis, which could be detected as early as 4 hours after treatment. After 48 hours with these concentrations, almost 100% of the HL-60 cells died by apoptosis without an increase in necrosis. K562 cells were found to be resistant to amidox but not to didox. In HL-60 cells, upstream caspase 8 is processed in response to didox, whereas caspases 8 and 9 are processed upon amidox treatment. Didox-induced apoptosis, but not amidox-induced apoptosis, can be correlated with the decrease in dNTP levels. The results suggests that amidox induces several apoptosis mechanisms in HL-60 cells. In contrast, only caspase 9 is activated by didox in K562 cells, and because amidox hardly induces apoptosis in this cell line, no caspase cleavage is observed., Conclusions: Didox triggers distinct apoptosis pathways in HL-60 and K562 cells.
- Published
- 2001
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28. The ribonucleotide reductase inhibitor trimidox induces c-myc and apoptosis of human ovarian carcinoma cells.
- Author
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Rosenberger G, Fuhrmann G, Grusch M, Fassl S, Elford HL, Smid K, Peters GJ, Szekeres T, and Krupitza G
- Subjects
- Cyclin D1 biosynthesis, Deoxyribonucleotides metabolism, Drug Screening Assays, Antitumor, Female, Gene Expression drug effects, Genes, cdc drug effects, HL-60 Cells, Humans, Ribonucleotide Reductases antagonists & inhibitors, Tumor Cells, Cultured, Urokinase-Type Plasminogen Activator biosynthesis, cdc25 Phosphatases biosynthesis, Antineoplastic Agents pharmacology, Apoptosis genetics, Benzamidines pharmacology, Enzyme Inhibitors pharmacology, Genes, myc, Ovarian Neoplasms drug therapy
- Abstract
Trimidox (3,4,5-trihydroxybenzohydroxamidoxime), a recently synthesized inhibitor of ribonucleotide reductase (RR), was shown to exert anti-proliferative activities in HL-60 and K562 human leukemia cell lines and to prolong the life span of mice inoculated with L1210 mouse leukemia cells. Here we test whether trimidox also exhibits anti-neoplastic properties in ovarian carcinoma cells. Since the mode of action of trimidox on cell fate has not been investigated so far, we addressed this unresolved item and find that this polyhydroxybenzoic acid derivative induces apoptosis of N.1 human ovarian carcinoma cells when tested in growth factor deprived medium. Utilizing an improved analysis, based on Hoechst 33258/propidium iodide double staining, apoptosis is quantified and discriminated from necrosis. Trimidox induces c-myc expression, which is indispensible for apoptosis of N.1 cells, and expression of plasminogen activator/urokinase type (upa), which supports the apoptotic process under more physiological conditions. Surprisingly, trimidox does not block dNTP synthesis in N.1 cells at the concentrations tested and, therefore, trimidox induces apoptosis independent of RR-inhibition. Like TNFalpha or benzamide riboside, which are also inducers of apoptosis of N.1 cells, trimidox also down-regulates the G1 cell cycle phosphatase cdc25A, whereas cyclin D1 becomes up-regulated. This report shows that trimidox destroys human ovarian carcinoma cells by inducing them to undergo apoptosis as well as corroborating previous investigations which demonstrated that apoptosis of these cells depends on c-myc over-expression when survival factors are withdrawn.
- Published
- 2000
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29. Trimidox, an inhibitor of ribonucleotide reductase, induces apoptosis and activates caspases in HL-60 promyelocytic leukemia cells.
- Author
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Fritzer-Szekeres M, Grusch M, Luxbacher C, Horvath S, Krupitza G, Elford HL, and Szekeres T
- Subjects
- Antineoplastic Agents pharmacology, Bisbenzimidazole, DNA Fragmentation, Enzyme Activation drug effects, Fas Ligand Protein, Fluorescent Dyes, Gelsolin metabolism, Gene Expression drug effects, Genes, myc, HL-60 Cells, Humans, Membrane Glycoproteins analysis, Poly(ADP-ribose) Polymerases metabolism, Propidium, fas Receptor analysis, Apoptosis drug effects, Benzamidines pharmacology, Caspases metabolism, Enzyme Inhibitors pharmacology, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Ribonucleotide reductase (RR) is the rate-limiting enzyme for the de novo synthesis of deoxyribonucleotides. Its activity is significantly increased in tumor cells related to the proliferation rate. Therefore, the enzyme is considered to be an excellent target for cancer chemotherapy. In the present study, we investigated whether the antineoplastic effects of trimidox (3,4, 5-trihydroxybenzamidoxime), a novel inhibitor of RR, were due to induction of apoptosis.HL-60 cells were incubated with various concentrations of trimidox. Consequently, cell morphology, DNA condensation, annexin binding, DNA fragmentation, and signature type cleavage of poly(ADP-ribose)polymerase and gelsolin were determined. We also tested the involvement of CD95 and CD95 ligand in apoptosis induction. Furthermore, we examined the c-myc expression of HL-60 cells after incubation with trimidox in order to elucidate a possible association between c-myc expression and induction of apoptosis in the case of trimidox. Trimidox incubation caused a time-dependent increase of c-myc RNA expression and this was accompanied by the induction of apoptosis. Apoptosis was triggered independently of CD95 by the activation of caspases and PARP cleavage. We conclude that trimidox is able to induce programmed cell death. The induction of apoptosis was demonstrated by various biochemical and morphological methods and seems to be associated with the induction of c-myc. Apoptosis was induced by the activation of caspases and without change of the CD95 and CD95 ligand expression.
- Published
- 2000
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30. Enhancement of hemoglobin and F-cell production by targeting growth inhibition and differentiation of K562 cells with ribonucleotide reductase inhibitors (didox and trimidox) in combination with streptozotocin.
- Author
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Iyamu WE, Adunyah SE, Fasold H, Horiuchi K, Elford HL, Asakura T, and Turner EA
- Subjects
- Antineoplastic Agents therapeutic use, Benzamidines therapeutic use, Cell Differentiation drug effects, Cell Division drug effects, Drug Therapy, Combination, Humans, Hydroxamic Acids therapeutic use, K562 Cells metabolism, Ribonucleotide Reductases antagonists & inhibitors, Benzamidines pharmacology, Enzyme Inhibitors pharmacology, Fetal Hemoglobin biosynthesis, Hemoglobin, Sickle biosynthesis, Hydroxamic Acids pharmacology, K562 Cells cytology, Streptozocin therapeutic use
- Abstract
Upon appropriate drug treatment, the human erythroleukemic K562 cells have been shown to produce hemoglobin and F-cells. Fetal hemoglobin (Hb F) inhibits the polymerization events of sickle hemoglobin (Hb S), thereby ameliorating the clinical symptoms of sickle cell disease. Ribonucleotide reductase inhibitors (RRIs) have been shown to inhibit the growth of myeloid leukemia cells leading to the production of Hb F upon differentiation. Of the RRIs currently in use, hydroxyurea is the most effective agent for Hb F induction. We have examined the capacity of two novel RRIs, didox (DI) and trimidox (TRI), in combination with streptozotocin (STZ), to induce hemoglobin and F-cell production. The K562 cells were cultured with different concentrations of didox-STZ or trimidox-STZ at a fixed molar ratio of 3:1 and 1:5 for 96 hr, respectively. At pre-determined time intervals, aliquots of cells were obtained and total hemoglobin (benzidine positive) levels, number of F-cells, and Hb F were determined by the differential staining technique, fetal hemoglobin assay kit, and fluorescence cytometry respectively. The effect of combined drug treatment on the growth of K562 cells was examined by isobologram analysis. Our results indicate that a synergistic growth-inhibitory differentiation effect occurred when didox or trimidox was used in combination with STZ on K562 cells. There was an increase in the number of both benzidine-positive normoblasts and F-cells, accompanied by morphologic appearances typical of erythroid maturation. On day 4, the number of benzidine-positive cells showed a 6-9-fold increase and the number of F-cells was between 2.5- and 5.7-fold higher than the respective controls. Based upon these results, treatment with a ribonucleotide reductase inhibitor, such as didox or trimidox, in combination with STZ, might offer an additional promising option in sickle cell disease therapy., (Copyright 2000 Wiley-Liss, Inc.)
- Published
- 2000
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31. Apoptosis-inducing cleavage of caspases by trimidox, an inhibitor of ribonucleotide reductase.
- Author
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Fritzer-Szekeres M, Luxbacher C, Horvath Z, Grusch M, Krupitza G, Elford HL, and Szekeres T
- Subjects
- Caspase 3, DNA Fragmentation, Gene Expression drug effects, HL-60 Cells, Humans, Poly(ADP-ribose) Polymerases metabolism, Proto-Oncogene Proteins c-myc genetics, Apoptosis, Benzamidines pharmacology, Caspase Inhibitors, Enzyme Inhibitors pharmacology, Ribonucleotide Reductases antagonists & inhibitors
- Published
- 2000
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32. A combination of hydroxyurea and isobutyramide to induce fetal hemoglobin in transgenic mice is more hematotoxic than the individual agents.
- Author
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Buller AM, Elford HL, DuBois CC, Meyer J, and Lloyd JA
- Subjects
- Animals, Disease Models, Animal, Drug Therapy, Combination, Fetal Hemoglobin analysis, Fetal Hemoglobin biosynthesis, Fetal Hemoglobin drug effects, Hemoglobinopathies drug therapy, Humans, Mice, Mice, Transgenic, RNA, Messenger analysis, Reticulocytes chemistry, Reticulocytes metabolism, gamma-Globulins drug effects, gamma-Globulins genetics, Amides therapeutic use, Amides toxicity, Fetal Hemoglobin metabolism, Hydroxyurea therapeutic use, Hydroxyurea toxicity
- Abstract
Pharmacologic agents such as hydroxyurea (HU), N, 3-4 trihydroxybenzamide (didox), and isobutyramide (ISB) can elevate gamma-globin as a potential treatment for the beta-hemoglobinopathies. In these experiments, transgenic mice with 5'HS2 from the human beta-globin locus control region, the fetal (A gamma), and adult (beta s) globin genes were used. Mice were treated with HU, didox, or ISB individually, or with combinations of HU or didox with ISB. The aim was to determine whether these drugs have synergistic effects on the induction of fetal hemoglobin (HbF) and whether the combination regimens are more hematotoxic. In the combination regimens, injections of HU or didox for five weeks were concomitant with ISB treatment every other day for the final three weeks of treatment. The combination of HU + ISB was more hematotoxic than the individual drugs based on significantly increased percentages of reticulocytes and reduced hemoglobin, indicating that caution should be taken in treatments involving combinations of these types of drugs. The didox + ISB combination was not more hematotoxic than the individual drugs. HbF was not induced in the groups treated with the combinations of HU or didox with ISB compared to the individual agents. There was a negligible effect on the percentage of HbF and an unexpected negative effect on the percentage of F cells. The results also have implications for future testing of HbF-inducing drugs in mouse models. In control mice that were phlebotomized but not treated with any drugs, increased percentages of F cells were observed, indicating that blood sampling can cause this effect. In addition, increases in the percentage of F cells did not correlate with increases in the percentage of HbF, indicating that monitoring F cells alone is not a sufficient measure of HbF induction.
- Published
- 1999
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33. In vivo and in vitro comparison of the short-term hematopoietic toxicity between hydroxyurea and trimidox or didox, novel ribonucleotide reductase inhibitors with potential anti-HIV-1 activity.
- Author
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Mayhew CN, Phillips JD, Greenberg RN, Birch NJ, Elford HL, and Gallicchio VS
- Subjects
- Acquired Immunodeficiency Syndrome drug therapy, Anemia chemically induced, Animals, Cells, Cultured, Colony-Forming Units Assay, Female, Femur, Hematopoiesis drug effects, Humans, In Vitro Techniques, Lymphocytes cytology, Lymphocytes drug effects, Macrophages cytology, Macrophages drug effects, Mice, Mice, Inbred C57BL, Neutrophils cytology, Neutrophils drug effects, Organ Size, Spleen cytology, Anti-HIV Agents toxicity, Benzamidines toxicity, Enzyme Inhibitors toxicity, Hematopoietic Stem Cells drug effects, Hydroxamic Acids toxicity, Hydroxyurea toxicity, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Inhibitors of the cellular enzyme ribonucleotide reductase (hydroxyurea, [HU]) have been proposed as a new therapeutic strategy for the treatment of HIV type-1 (HIV-1) infection. However, HU use may be limited by the frequent development of hematopoietic toxicity. We report here short-term hematopoietic toxicity in mice receiving HU when compared to either of two more potent enzyme inhibitors, didox (DX) and trimidox (TX). High dose HU, DX, and TX monotherapy (500, 460, and 220 mg/kg/day respectively) was administered by daily i.p. injection (Monday-Friday) to C57BL/6 mice for 10 weeks. Effects on hematopoiesis were established by quantitating peripheral blood indices (hematocrit, hemoglobin, mean corpuscular volume, mean cell hemoglobin, mean corpuscular hemoglobin concentration, RBC, and WBC) and numbers of colony-forming units-granulocyte-macrophage (CFU-GM) and BFU-E from bone marrow and spleen. HU produced rapid induction of a macrocytic hypochromic anemia and altered white blood cell kinetics associated with myelosuppression defined as reduced marrow organ cellularity and induction of splenic extramedullary hematopoiesis. Compared to HU, TX and DX induced fewer changes in peripheral blood indices and CFU-GM and BFU-E per hematopoietic organ. In vitro human and murine marrow CFU-GM and BFU-E colony formations were assayed in the presence of dose escalation HU, DX, or TX (0, 1, 10, 50, 100, and 200 microM). HU inhibited colony formation more than either DX or TX. These in vivo and in vitro studies suggest that novel ribonucleotide reductase inhibitors TX and DX may provide an effective alternative to HU in HIV-1 therapy because they demonstrate reduced hematopoietic toxicity.
- Published
- 1999
- Full Text
- View/download PDF
34. Antimalarial activities of polyhydroxyphenyl and hydroxamic acid derivatives.
- Author
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Holland KP, Elford HL, Bracchi V, Annis CG, Schuster SM, and Chakrabarti D
- Subjects
- Animals, Hydroxyurea pharmacology, Plasmodium falciparum drug effects, Structure-Activity Relationship, Antimalarials pharmacology, Hydroxamic Acids pharmacology, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Several known mammalian ribonucleotide reductase inhibitors featuring a polyhydroxyphenyl and/or hydroxamate moiety as the active group were screened for potency in inhibiting growth of the malaria parasite Plasmodium falciparum. Compounds containing a 2,3- or 3,4-dihydroxyphenyl group as well as benzohydroxamate appear to be the most effective inhibitors of the malaria parasite.
- Published
- 1998
- Full Text
- View/download PDF
35. Interaction of gallium nitrate with other inhibitors of ribonucleotide reductase: effects on the proliferation of human leukemic cells.
- Author
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Myette MS, Elford HL, and Chitambar CR
- Subjects
- Antineoplastic Agents pharmacology, Benzamidines pharmacology, Cell Division drug effects, Deoxycytidine analogs & derivatives, Deoxycytidine pharmacology, Drug Synergism, Enzyme Inhibitors pharmacology, Humans, Hydroxamic Acids pharmacology, Hydroxyurea pharmacology, Oximes pharmacology, Tumor Cells, Cultured, Gemcitabine, Gallium pharmacology, Precursor Cell Lymphoblastic Leukemia-Lymphoma pathology, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Ribonucleotide reductase, a key enzyme in deoxyribonucleotide synthesis, is an important target for cancer chemotherapy. Drugs that inhibit its individual components may act synergistically to block DNA synthesis. Prior work has established that gallium inhibits the R2 subunit of ribonucleotide reductase. We show that gallium acts synergistically with the ribonucleotide reductase inhibitors gemcitabine and hydroxyurea to inhibit the proliferation of CCRF-CEM cells. In contrast, combinations of gallium with the ribonucleotide reductase inhibitors amidox, didox, or trimidox produced antagonistic effects on cell growth. Spectroscopy analysis revealed that as a result of their metal-binding properties, amidox, didox and trimidox formed complexes with gallium, thus negating potential synergistic actions. Our results have important implications in the design of clinical trials using these ribonucleotide reductase inhibitors in combination.
- Published
- 1998
- Full Text
- View/download PDF
36. Trimidox-mediated morphological changes during erythroid differentiation is associated with the stimulation of hemoglobin and F-cell production in human K562 cells.
- Author
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Iyamu EW, Adunyah SE, Elford HL, Fasold H, and Turner EA
- Subjects
- Cell Division drug effects, Enzyme Inhibitors, Erythroid Precursor Cells cytology, Erythroid Precursor Cells drug effects, Fetal Hemoglobin metabolism, Histocytochemistry, Humans, Leukemia, Erythroblastic, Acute metabolism, Tumor Cells, Cultured, Benzamidines pharmacology, Cell Differentiation drug effects, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Trimidox (3,4,5-trihdroxybenzamidoxime) has been shown to reduce the activity of ribonucleotide reductase with accompanied growth inhibition and differentiation of mammalian cells. Hydroxyurea (HU) is the only ribonucleotide reductase inhibitor in clinical use for the treatment and management of sickle cell anemia, since this compound increases fetal hemoglobin (Hb F) production: a potent inhibitor of sickle hemoglobin (Hb SS) polymerization. However, the main limitations of HU is its lack of potency, myelosuppression and short half life. These studies investigated the effects of trimidox on the induction of hemoglobin and F-cells production in K562 erythroleukemia cells. Our study reveals that trimidox exhibits concentration dependent inhibitory effect on K562 cells with increase in benzidine positive normoblasts and F-cells production as well as morphological changes typical of erythroid differentiation. These findings provide the first evidence that the growth inhibitory differentiation of cells induced by trimidox enhance hemoglobin and F-cells production.
- Published
- 1998
- Full Text
- View/download PDF
37. Iron binding capacity of didox (3,4 dihydroxybenzohydroxamic acid) and amidox (3,4 dihydroxybenzamidoxime) two inhibitors of the enzyme ribonucleotide reductase.
- Author
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Fritzer-Szekeres M, Novotny L, Vachalkova A, Göbl R, Elford HL, and Szekeres T
- Subjects
- Animals, Antineoplastic Agents toxicity, Cell Division drug effects, Enzyme Inhibitors toxicity, Humans, Hydroxamic Acids toxicity, Iron pharmacology, Leukemia L1210, Mice, Oximes toxicity, Polarography, Tumor Cells, Cultured, Antineoplastic Agents chemistry, Enzyme Inhibitors chemistry, Hydroxamic Acids chemistry, Iron chemistry, Oximes chemistry, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Ribonucleotide reductase is the rate limiting enzyme of deoxynucleoside triphosphate synthesis and is considered to be an excellent target of cancer chemotherapy. Didox and amidox are newly synthesized compounds, which inhibit this enzyme and have in vitro and in vivo antitumor activity. We have now investigated the capability of didox and amidox to interfere with the iron metabolism. We show by photometric and polarographic methods, that didox and amidox are capable of forming an iron complex. However, their cytotoxic action cannot be circumvented by addition of Fe-ammoniumcitrate, indicating the iron complexing capacity not to be responsible for the mechanism of action of these compounds. When L1210 leukemia cells were incubated with the didox-iron or amidox-iron complex itself, only slight changes of the 50% growth inhibitory capacity of the complex in comparison with didox or amidox alone could be shown. We conclude, that didox and amidox are capable of forming an iron complex, but in contrast to other agents, the anticancer activity cannot be contributed to this effect alone. Further studies will have to elucidate the molecular mechanism of action of these new and promising anticancer agents.
- Published
- 1998
- Full Text
- View/download PDF
38. Enhanced effects of adriamycin by combination with a new ribonucleotide reductase inhibitor, trimidox, in murine leukemia.
- Author
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Fritzer-Szekeres M, Novotny L, Romanova D, Göbl R, Sedlak J, Vachalkova A, Rauko P, Elford HL, and Szekeres T
- Subjects
- Animals, Mice, Mice, Inbred DBA, Neoplasm Transplantation, Antineoplastic Combined Chemotherapy Protocols therapeutic use, Benzamidines therapeutic use, Doxorubicin therapeutic use, Enzyme Inhibitors therapeutic use, Leukemia L1210 drug therapy, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Ribonucleotide reductase is the rate limiting enzyme of de novo DNA synthesis; its activity is significantly increased in tumor cells related to the proliferation rate. Therefore the enzyme is considered to be an excellent target for cancer chemotherapy. In the present study we tested the in vitro and in vivo antitumor effects of a drug combination using trimidox (3,4,5-trihydroxybenzamidoxime), a novel inhibitor of ribonucleotide reductase with adriamycin, a widely used anticancer drug. This combination was selected because adriamycin generates free radicals being responsible for cardiotoxic side effects; trimidox has been shown to be a good free radical scavenger. The in vitro cytotoxic effect of the drug combination was examined in L1210 mouse leukemia cells employing a MTT chemosensitivity assay. Incubation of these cells with adriamycin and trimidox together yielded less than additive cytotoxic effects compared to either drug alone. These effects were not caused by the involvement of p-glycoprotein mediated drug efflux. However, when the effect of trimidox and adriamycin in combination was examined in L1210 leukemia bearing mice antitumor effects of adriamycin could be enhanced by the presence of trimidox. Our data indicate, that the in vivo combination of adriamycin together with trimidox might be beneficial for the treatment of malignancies.
- Published
- 1998
- Full Text
- View/download PDF
39. Effective use of ribonucleotide reductase inhibitors (Didox and Trimidox) alone or in combination with didanosine (ddI) to suppress disease progression and increase survival in murine acquired immunodeficiency syndrome (MAIDS).
- Author
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Mayhew C, Oakley O, Piper J, Hughes NK, Phillips J, Birch NJ, Elford HL, and Gallicchio VS
- Subjects
- Animals, Benzamidines pharmacology, Biomarkers, Didanosine pharmacology, Disease Progression, Drug Therapy, Combination, Female, Hydroxamic Acids pharmacology, Leukemia Virus, Murine drug effects, Mice, Mice, Inbred C57BL, Murine Acquired Immunodeficiency Syndrome mortality, Murine Acquired Immunodeficiency Syndrome physiopathology, Murine Acquired Immunodeficiency Syndrome virology, Survival Rate, Antiviral Agents pharmacology, Murine Acquired Immunodeficiency Syndrome drug therapy, Ribonucleotide Reductases antagonists & inhibitors, Ribonucleotide Reductases pharmacology
- Abstract
Ribonucleotide reductase inhibitors (RRIs) have been recently shown to inhibit retroviral replication. We examined a new series of RRIs, 3,4-dihydroxybenzohydroxamic acid (Didox) and 3,4,5-trihydroxybenzohydroxamidoxime (Trimidox) for their ability to alter disease progression in murine acquired immunodeficiency syndrome (MAIDS), both alone and in combination with 2',3'-dideoxyinosine (ddI). MAIDS disease was induced by inoculation of female C57BL/6 mice with the LP-BM5 murine leukemia virus (MuLV) and disease progression characterized by extensive peripheral lymphadenopathy and splenomegaly. Efficacy of treatment with these drugs was based upon their ability to influence survival and disease pathophysiology by monitoring the development of splenomegaly. Toxicity was determined by changes in body weight, total peripheral white blood cell count and hematocrit. Didox or trimidox monotherapy was associated with increased survival and decreased disease pathophysiology, with no apparent toxicity. Combined with ddI, their ability to reduce development of viral induced splenomegaly was enhanced compared to trimidox, didox or ddI alone. These results demonstrate RRIs have potent activity in reversing the disease manifestations characteristic of MAIDS. Further studies are warranted to determine human clinical efficacy.
- Published
- 1997
40. DNA-protective activity of new ribonucleotide reductase inhibitors.
- Author
-
Rauko P, Romanova D, Miadokova E, Macakova K, Novotny L, Elford HL, and Szekeres T
- Subjects
- Antineoplastic Agents pharmacology, Benzamidines pharmacology, DNA Damage drug effects, DNA, Superhelical drug effects, Enzyme Inhibitors pharmacology, Free Radicals, Hydrogen Peroxide, Hydroxamic Acids pharmacology, Hydroxyurea pharmacology, Oximes pharmacology, Plasmids, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
The DNA-protective activity of hydroxyurea (HU) and novel ribonucleotide reductase (RR) inhibitors amidox (AX), didox (DX) and trimidox (TX) was examined using hydrogen peroxide as the DNA-damaging agent. The exposure of superspiralized plasmid DNA molecules (pBR 322) to H2O2 under precisely defined in vitro conditions initiates a change in DNA topology (DNA from I relaxes to DNA form II). This electrophoretically monitored change in the plasmid DNA topology is related to the induction of ss-DNA breaks and corresponds with DNA exposition to free radicals. The inhibition of DNA relaxation (the prevention of DNA damage induced by hydrogen peroxide) depended on the free radical scavenging capacity of the drugs investigated. HU exerted DNA protective activity at a concentration of 4 mM, AX at concentration of 1 microM, TX at a concentration of 5 microM and DX at a concentration of 25 microM (the free radical scavenging activity increases from HU to AX in following manner: HU << DX < TX < AX). It can be concluded that the new synthetic RR-inhibitor AX which is being investigated at the preclinical level as a potential anti-cancer drug possess the highest capacity for scavenging of free radicals.
- Published
- 1997
41. The new inhibitors of ribonucleotide reductase--comparison of some physico-chemical properties.
- Author
-
Romanova D, Vachalkova A, Szekeres T, Elford HL, and Novotny L
- Subjects
- Benzamidines pharmacology, Chromatography, High Pressure Liquid, Enzyme Inhibitors pharmacology, Hydrogen-Ion Concentration, Hydroxamic Acids pharmacology, Oximes pharmacology, Polarography, Spectrophotometry, Ultraviolet, Benzamidines chemistry, Enzyme Inhibitors chemistry, Hydroxamic Acids chemistry, Oximes chemistry, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Amidox (AX), didox (DX) and trimidox (TX), compounds synthetized as new ribonucleotide reductase inhibitors, have been investigated by ultraviolet (UV) spectrophotometry, polarography and high performance liquid chromatography (HPLC). The experiments have been performed at various pH values. The changes in UV absorption of the compounds studied were recorded and it was demonstrated that these changes are related to the pH and to structural features of the investigated molecules. From the compounds included in our series of experiments, only amidox and trimidox are reduced during polarographic experiments in Britton-Robinson buffer. The reduction of both compounds proceeded in two one-electron steps in acidic pH. One two-electron diffuse irreversible wave was observed at basic pH. The values of the half-wave potential became more negative in accordance with the increasing pH. HPLC assay also showed changes in the retention of compounds investigated, particularly when the pH of the mobile phase was close to the dissociation constant of the particular drug. The changes of physico-chemical properties detected by the all used methods are related to different chemical structures (the most significant changes were observed in alkaline pH).
- Published
- 1997
- Full Text
- View/download PDF
42. The enzyme ribonucleotide reductase: target for antitumor and anti-HIV therapy.
- Author
-
Szekeres T, Fritzer-Szekeres M, and Elford HL
- Subjects
- HIV growth & development, Humans, Hydroxamic Acids chemical synthesis, Hydroxamic Acids pharmacology, Hydroxamic Acids therapeutic use, Hydroxyurea therapeutic use, Virus Replication drug effects, Antineoplastic Agents, Antiviral Agents, Enzyme Inhibitors therapeutic use, HIV drug effects, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Ribonucleotide reductase is the rate-limiting enzyme of DNA synthesis, and it has been shown to be linked with malignant transformation and tumor cell proliferation. It was therefore considered as an excellent target for cancer chemotherapy. This article reviews the in vitro and in vivo effects of hydroxyurea the first inhibitor of the enzyme, which is currently used in general clinical practice. In addition, we summarize the results obtained with other inhibitors of the enzyme; for instance, polyhydroxy-substituted benzohydroxamic acid derivatives, a promising group of inhibitors of ribonucleotide reductase that was synthesized by Bart van'T Riet and investigated by our group. In vitro as well as animal data and pharmacokinetic results are reviewed and possible implications for an improvement in the management of various patient groups are outlined.
- Published
- 1997
- Full Text
- View/download PDF
43. Iron binding capacity of didox (3,4-dihydroxybenzohydroxamic acid) and amidox (3,4-dihydroxybenzamidoxime) new inhibitors of the enzyme ribonucleotide reductase.
- Author
-
Fritzer-Szekeres M, Novotny L, Vachalkova A, Findenig G, Elford HL, and Szekeres T
- Subjects
- Animals, Antineoplastic Agents toxicity, Enzyme Inhibitors toxicity, Humans, Hydroxamic Acids toxicity, Leukemia L1210 drug therapy, Leukemia, Erythroblastic, Acute drug therapy, Mice, Oxidation-Reduction, Oximes toxicity, Polarography, Tumor Cells, Cultured, Antineoplastic Agents metabolism, Antineoplastic Agents pharmacology, Enzyme Inhibitors metabolism, Enzyme Inhibitors pharmacology, Hydroxamic Acids metabolism, Hydroxamic Acids pharmacology, Iron Compounds metabolism, Oximes metabolism, Oximes pharmacology, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Ribonucleotide reductase is the rate limiting enzyme of deoxynucleoside triphosphate synthesis and is considered to be an excellent target of cancer chemotherapy. Didox and amidox are newly synthesized compounds, which inhibit this enzyme and have in vitro and in vivo antitumor activity. We have now investigated the capability of didox and amidox to interfere with the iron metabolism. We show by photometric and polarographic methods, that didox and amidox are capable of forming an iron complex. However, their cytotoxic action cannot be completely circumvented by addition of Fe-ammoniumcitrate, indicating that the iron complexing capacity may not be responsible for the mechanism of action of these compounds. When L1210 leukemia cells were incubated with the didox-iron or amidox-iron complex itself, changes of the 50% growth inhibitory capacity of the complex in comparison with didox or amidox alone could be shown. We conclude, that didox and amidox are capable of forming iron complexes, but in contrast to other agents, the anticancer activity cannot be contributed to this effect alone. Future studies will have to elucidate the molecular mechanism of action of these new and promising anticancer agents.
- Published
- 1997
- Full Text
- View/download PDF
44. Iron binding capacity of trimidox (3,4,5-trihydroxybenzamidoxime), a new inhibitor of the enzyme ribonucleotide reductase.
- Author
-
Szekeres T, Vielnascher E, Novotny L, Vachalkova A, Fritzer M, Findenig G, Göbl R, Elford HL, and Goldenberg H
- Subjects
- Cell Division drug effects, Cell Survival drug effects, Dose-Response Relationship, Drug, HL-60 Cells, Humans, Kinetics, Oxidation-Reduction, Polarography, Benzamidines chemistry, Benzamidines toxicity, Enzyme Inhibitors chemistry, Enzyme Inhibitors toxicity, Iron pharmacology, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Ribonucleotide reductase is the rate limiting enzyme of deoxynucleoside triphosphate synthesis and is considered to be an excellent target of cancer chemotherapy. Trimidox, a newly synthesized compound, inhibits this enzyme and has in vitro and in vivo antitumour activity. As trimidox was able to upregulate the expression of the transferrin receptor in HL-60 human promyelocytic leukaemia cells, we have now investigated the capability of trimidox to interfere with iron metabolism. We show by photometric and polarographic methods that trimidox is able for form an iron complex. However, its cytotoxic action cannot be circumvented by addition of iron-saturated transferrin or iron-ammonium citrate, indicating that the iron complexing capacity is not responsible for the mechanism of action of this compound. When HL-60, K562 or L1210 leukaemia cells were incubated with the trimidox-iron complex itself, we could observe increases of the 50% growth inhibitory capacity of the complex in comparison with trimidox alone. We conclude that trimidox is able to form an iron complex, but in contrast to other agents, the anticancer activity cannot be contributed to this effect alone. Further studies will have to elucidate the molecular mechanism of action of this new and promising anticancer agent.
- Published
- 1995
- Full Text
- View/download PDF
45. Transgenic mouse model of pharmacologic induction of fetal hemoglobin: studies using a new ribonucleotide reductase inhibitor, Didox.
- Author
-
Pace BS, Elford HL, and Stamatoyannopoulos G
- Subjects
- Anemia chemically induced, Animals, Chemical and Drug Induced Liver Injury, Erythropoietin therapeutic use, Gene Expression drug effects, Humans, Hydroxamic Acids adverse effects, Hydroxamic Acids toxicity, Leukopenia chemically induced, Mice, Mice, Transgenic, Recombinant Proteins therapeutic use, Reticulocytes metabolism, Thrombocytopenia chemically induced, Fetal Hemoglobin biosynthesis, Hydroxamic Acids pharmacology, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Evaluation of pharmacologic agents that stimulate fetal hemoglobin production has been done mainly in baboons and macaques. We investigated whether results in transgenic mice can predict the stimulation of fetal hemoglobin in primates, by testing gamma globin induction in response to a new ribonucleotide reductase inhibitor, Didox. A transgenic mouse line carrying the human A gamma gene linked to a locus control region cassette was used. Treatment of transgenic mice with Didox resulted in induction of gamma gene expression as documented by an increase in F reticulocytes and F cells and an elevation of gamma/gamma + beta biosynthetic ratio. Similarly, administration of Didox to a baboon in the nonanemic and chronically anemic state resulted in induction of gamma gene expression as shown by increases in F reticulocytes, F cells, and Hb F. These results suggest that the muLCR-A gamma transgenic mice can be used to screen new pharmacologic compounds for gamma globin inducibility.
- Published
- 1994
- Full Text
- View/download PDF
46. Biochemical and antitumor activity of trimidox, a new inhibitor of ribonucleotide reductase.
- Author
-
Szekeres T, Gharehbaghi K, Fritzer M, Woody M, Srivastava A, van't Riet B, Jayaram HN, and Elford HL
- Subjects
- Animals, Drug Screening Assays, Antitumor, Female, Leukemia, Experimental enzymology, Male, Mice, Mice, Inbred Strains, Neoplasm Transplantation, Ribonucleotide Reductases analysis, Tumor Cells, Cultured, Antineoplastic Agents pharmacology, Benzamidines pharmacology, Leukemia, Experimental drug therapy, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Trimidox (3,4,5-trihydroxybenzamidoxime), a newly synthesized analog of didox (N,3,4-trihydroxybenzamide) reduced the activity of ribonucleotide reductase (EC 1.17.4.1) in extracts of L1210 cells by 50% (50% growth-inhibitory concentration, IC50) at 5 microM, whereas hydroxyurea, the only ribonucleotide reductase inhibitor in clinical use, exhibited an IC50 of 500 microM. Ribonucleotide reductase activity was also measured in situ by incubating L1210 cells for 24 h with trimidox at 7.5 microM, a concentration that inhibits cell proliferation by 50% (IC50) or at 100 microM for 2 h; these concentrations resulted in a decrease in enzyme activity to 22% and 50% of the control value, respectively. Trimidox and hydroxyurea were cytotoxic to L1210 cells with IC50 values of 7.5 and 50 microM, respectively. Versus ribonucleotide reductase, trimidox and hydroxyurea yielded IC50 values of 12 and 87 microM, respectively. A dose-dependent increase in life span was observed in mice bearing intraperitoneally transplanted L1210 tumors. Trimidox treatment (200 mg/kg; q1dx9) significantly increased the life span of mice bearing L1210 leukemia (by 82% in male mice and 112% in female mice). The anti-tumor activity appeared more pronounced in female mice than in male mice. Viewed in concert, these findings suggest that trimidox is a new and potent inhibitor of ribonucleotide reductase and that it is a promising candidate for the chemotherapy of cancer in humans.
- Published
- 1994
- Full Text
- View/download PDF
47. Studies on the mechanisms of inhibition of L1210 cell growth by 3,4-dihydroxybenzohydroxamic acid and 3,4-dihydroxybenzamidoxime.
- Author
-
Tihan T, Elford HL, and Cory JG
- Subjects
- Animals, Cell Line, Cytidine metabolism, Deoxyribonucleotides metabolism, Hydroxyurea pharmacology, Kinetics, Mice, Antineoplastic Agents pharmacology, Cell Division drug effects, Hydroxamic Acids pharmacology, Leukemia L1210 metabolism, Oximes pharmacology, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
Didox and Amidox inhibit L1210 cell growth in culture. At least one of the mechanisms in the mode(s) of action of the compounds is directed at the ribonucleotide reductase site. Partially purified preparations of ribonucleotide reductase activity are inhibited by Amidox and Didox. The formation of deoxycytidine nucleotides from [14C]cytidine in intact L1210 cells is also blocked. Didox and Amidox cause the decrease in the intracellular pools of the four dNTPs. Hydroxyurea-resistant L1210 cells are not cross-resistant to either Didox or Amidox. These data suggest that Didox and Amidox are not inhibiting ribonucleotide reductase through a mechanism similar to hydroxyurea.
- Published
- 1991
- Full Text
- View/download PDF
48. Modulation of cytarabine metabolism in the human promyelocytic leukemia cell line HL-60 by polyhydroxy-substituted benzohydroxamic acids.
- Author
-
Howell SB, Gill S, and Elford HL
- Subjects
- Cell Line, DNA metabolism, Humans, Time Factors, Cytarabine metabolism, Hydroxamic Acids pharmacology, Leukemia, Myeloid metabolism
- Abstract
Two potent new ribonucleotide reductase inhibitors, 3,4,5-trihydroxybenzohydroxamic acid (VF 122) and 3,4-dihydroxybenzohydroxamic acid (VF 147), were investigated for their ability to modulate the cellular pharmacology of cytarabine (ara-C) in HL-60 cells. VF 122 and VF 147 increased the total cellular uptake of ara-C by a mean (+/- SE) of 8% +/- 3% and 29% +/- 3%, respectively, when measured 2 hours after the start of exposure to 0.1 microM ara-C. This effect was evident after only 10 minutes of exposure to the riboNucleotide reductase inhibitor and did not vary significantly over the concentration range of 10-100 microM for either agent. VF 122 enhanced the incorporation of ara-CTP into DNA by 3.6-fold; VF 147 produced a 5.6-fold increase. In comparison, the maximum enhancement achievable with hydroxyurea was 2.1-fold, and with thymidine was 1.8-fold. These results provide a biochemical rationale for further investigation of these agents in combination with ara-C.
- Published
- 1982
49. Structure-activity relationships of benzohydroxamic acid inhibitors of ribonucleotide reductase.
- Author
-
van't Riet B, Kier LB, and Elford HL
- Subjects
- Chemical Phenomena, Chemistry, Hydroxamic Acids chemical synthesis, Structure-Activity Relationship, Hydroxamic Acids pharmacology, Ribonucleotide Reductases antagonists & inhibitors
- Abstract
A structure-activity relationship study of 28 substituted benzohydroxamic acids that inhibit ribonucleotide reductase was undertaken to discern the structural features of the molecule contributing to the inhibitory potency of these compounds. An equation containing three molecular connectivity indexes, but not including Hammett sigma values, was developed which gives close correlation with observed values for ribonucleotide reductase inhibition. It is postulated that the inhibitory potency involves two parts of the benzohydroxamic acid molecule. One is the hydroxamic portion, which complexes with the metal component of the enzyme, providing a qualitative effect. The other is an interaction involving the benzene ring and its substituents and may provide the quantitative aspect of the observed inhibition values.
- Published
- 1980
- Full Text
- View/download PDF
50. Effect of methotrexate and 5-fluorodeoxyuridine on ribonucleotide reductase activity in mammalian cells.
- Author
-
Elford HL, Bonner EL, Kerr BH, Hanna SD, and Smulson M
- Subjects
- Animals, DNA biosynthesis, Enzyme Induction drug effects, HeLa Cells drug effects, Liver drug effects, Liver Regeneration, Male, Protein Biosynthesis, Rats, Thymine Nucleotides metabolism, Floxuridine pharmacology, HeLa Cells enzymology, Liver enzymology, Methotrexate pharmacology, Ribonucleotide Reductases biosynthesis
- Abstract
A number of studies in bacteria have indicated that deoxythymidine 5'-triphosphate may be a repressor or corepressor of ribonucleotide reductase. For determination of whether a similar regulating mechanism exists in mammalian cells, HeLa cells and partially hepatectomized rats were treated with either methotrexate, 5-fluorouracil, or 5-fluorodeoxyuridine in order to block thymidylate synthesis and consequently lower the intracellular pools of deoxythymidine 5'-triphosphate. In HeLa cells there was a significant (360 to 400 percent) increase in reductase activity in both the methotrexate and 5-fluorodeoxyuridine-treated cells. The administration of methotrexate to partially hepatectomized rats resulted in a 2.7-fold enhancement of the hepatectomy-induced increase in reductase activity, and the 5-fluorouracil treatment yielded a 60 percent increment in the increase of ribonucleotide reductase activity after partial hepatectomy. Cycloheximide prevented the increase in reductase activity after the exposure of HeLa cells to methotrexate and 5-fluorodeoxyuridine, indicating that the stimulation of ribonucleotide reductase activity was the result of enhancement of de novo enzyme synthesis rather than of enzyme activation. The data support the thesis that deoxythymidine 5'-triphosphate or a thymidylate metabolite may be involved in the regulation of ribonucleotide reductase levels in mammalian cells.
- Published
- 1977
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