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The Biochemical Journal Sep 1992DT-diaphorase [NAD(P)H:quinone oxidoreductase; EC 1.6.99.2] catalysed the two-electron reduction of the anti-tumour quinone...
Thiol oxidation coupled to DT-diaphorase-catalysed reduction of diaziquone. Reductive and oxidative pathways of diaziquone semiquinone modulated by glutathione and superoxide dismutase.
DT-diaphorase [NAD(P)H:quinone oxidoreductase; EC 1.6.99.2] catalysed the two-electron reduction of the anti-tumour quinone 2,5-bis-(1-aziridinyl)-3,6-bis(ethoxycarbonylamino)-1,4-benzoquino ne (AZQ) to the hydroquinone form (AZQH2). Although DT-diaphorase catalysis of AZQ was not significantly affected by pH, the hydroquinone product was effectively stabilized by protonation at pH values below 7, whereas, above that pH, hyroquinone autoxidation, evaluated in terms of H2O2 production, increased exponentially. The autoxidation of AZQH2 entailed the formation of diverse radicals, such as O2-.,HO., and the semiquinone form of AZQ (AZQ-.), which contributed to different extents to the e.p.r. spectrum. Superoxide dismutase enhanced the autoxidation of AZQH2 and suppressed the e.p.r. signal ascribed to AZQ-., in agreement with a displacement of the equilibrium of the semiquinone autoxidation reaction (AZQ-.+O2 in equilibrium with AZQ+O2-.) upon enzymic withdrawal of O2-.. GSH increased the steady-state concentration of AZQH2 formed during DT-diaphorase catalysis and inhibited temporarily its autoxidation. This effect was accompanied by oxidation of the thiol to the disulphide within a process involving glutathionyl radical (GS.) formation, the relative contribution of which to the e.p.r. spectrum was enhanced by increasing GSH concentrations. GS. formation in this experimental model can be rationalized as originating from the reaction of GSH with AZQ-., rather than with O2-. or HO., for thiol oxidation was not affected significantly by superoxide dismutase, and GS. formation was insensitive to catalase. In addition, GSH suppressed the e.p.r. signal attributed to AZQ-.. No glutathionyl-quinone conjugate was detected during the DT-diaphorase-catalysed reduction of AZQ; although the chemical requirements for alkylation were partly fulfilled (quinone ring aromatization and acid-assisted aziridinyl ring opening), the negligible dissociation of GSH (GS(-)+H+ in equilibrium with GSH) at low pH prevented any nucleophilic addition to occur. Therefore the redox transitions of AZQ during DT-diaphorase catalysis seemed to be centred on the semiquinone species, the fate of which was inversely affected by catalytic amounts of superoxide dismutase and large amounts of GSH: the former enhanced AZQ-. autoxidation and the latter favoured AZQ-. reduction. Accordingly, superoxide dismutase and GSH suppressed the semiquinone e.p.r. signal. These results are discussed in terms of three interdependent redox transitions (comprising one-electron transfer reactions involving the quinone, oxygen and the thiol) and the thermodynamic and kinetic properties of the reactions involved.
Topics: Aziridines; Benzoquinones; Catalysis; Free Radicals; Glutathione; Hydrogen-Ion Concentration; Kinetics; NAD(P)H Dehydrogenase (Quinone); Oxidation-Reduction; Spectrum Analysis; Sulfhydryl Compounds; Superoxide Dismutase; Thermodynamics
PubMed: 1530580
DOI: 10.1042/bj2860481 -
Cancer Treatment Reports 1984Twenty-eight patients received diaziquone (AZQ) as a single iv dose ranging from 2 to 27.5 mg/m2 in a phase I study. Myelosuppression was dose-limiting, tended to be...
Twenty-eight patients received diaziquone (AZQ) as a single iv dose ranging from 2 to 27.5 mg/m2 in a phase I study. Myelosuppression was dose-limiting, tended to be cumulative, and was somewhat unpredictable in its occurrence. No pretreatment patient characteristics or chemical abnormalities were found to be consistently related to hematologic toxicity. No objective responses were noted in this study, with most patients having gastrointestinal neoplasms. A single iv injection of 22.5-27.5 mg/m2 of AZQ given every 4-5 weeks would be a suitable initial schedule. Pharmacokinetic studies revealed that the plasma elimination of AZQ was best described by a two-compartment open model with rapid plasma elimination of the parent drug.
Topics: Antineoplastic Agents; Aziridines; Azirines; Benzoquinones; Bone Marrow; Drug Evaluation; Humans; Neoplasms
PubMed: 6744349
DOI: No ID Found -
Cancer Research Nov 1986To analyze the mode of action of diaziquone [AZQ] on DNA, we examined the activity of two AZQ analogues and N,N',N"-triethylenethiophosphoramide on three forms...
To analyze the mode of action of diaziquone [AZQ] on DNA, we examined the activity of two AZQ analogues and N,N',N"-triethylenethiophosphoramide on three forms [supercoiled (Form I), open circular (Form II), and linear (Form III)] of PM-2 DNA. The AZQ analogues contained chlorine atoms which substituted either the carbethoxyamino groups or the aziridine groups of the parent compound. N,N',N"-triethylenethiophosphoramide is a triaziridine compound containing pentavalent phosphorus instead of a quinone group. We found that only when reduced with sodium borohydride did AZQ change the topology of the three forms of PM-2 DNA by introducing mainly single strand breaks. The AZQ analogue containing only aziridines (RQ2) was active in both its oxidized and its reduced forms, while the analogue containing only the carbethoxyamino groups (RQ14) or N,N',N"-triethylenethiophosphoramide were not active in either form. Under similar experimental conditions, Adriamycin alone altered the electrophoretic mobility of PM-2 DNA, while borohydride reduced Adriamycin did not. By using electron spin resonance spectroscopy, we showed that dihydrodiaziquone (AZQH2) oxidizes to the semiquinone in the presence of oxygen. Although AZQH2 was active against DNA, it was not active against cellular DNA synthesis as measured by [3H]thymidine incorporation into exponentially growing HEp-2 cells. However, AZQ alone prevented [3H]thymidine incorporation into HEp-2 cells. We found that HEp-2 cells have the ability to reduce AZQ to its free radical anion, but AZQH2 does not autoxidize to the free radical in the presence of cells. The reductive ability of HEp-2 cells may be responsible in part for preventing the oxidation of AZQH2 to the free radical. We found that under our conditions (1-h incubations) the aziridines are essential for the activity of aziridinyl quinones against PM-2 DNA and that in the case of AZQ the hydroquinone is also required.
Topics: Aziridines; Azirines; Bacteriophages; Benzoquinones; Cell Line; DNA Damage; DNA Replication; DNA, Superhelical; DNA, Viral; Doxorubicin; Electron Spin Resonance Spectroscopy; Free Radicals; Humans; Hydroquinones; Oxidation-Reduction; Oxygen Consumption; Quinones; Structure-Activity Relationship; Thiotepa
PubMed: 3019536
DOI: No ID Found -
Journal of Natural Products Apr 2010Nine geranylated flavanones isolated from the fruits of Paulownia tomentosa (4-12) and two from the roots of Morus alba (13 and 14) were examined for cytotoxicity to...
Nine geranylated flavanones isolated from the fruits of Paulownia tomentosa (4-12) and two from the roots of Morus alba (13 and 14) were examined for cytotoxicity to selected human cancer cell lines and normal human fibroblasts. Cytotoxicity was determined in vitro using a calcein AM cytotoxicity assay. Cytotoxicity for the THP-1 monocytic leukemia cell line was tested using erythrosin B cell staining. The geranylated compounds tested were compared with the known simple flavanone standards taxifolin (1), naringenin (2), and hesperetin (3) and with the standard anticancer drugs olomoucine II, diaziquone, and oxaliplatin and the antineoplastic compound camptothecin, and showed different levels of cytotoxicity. The effects of structural changes on cytotoxic activity, including geranyl substitution of the flavanone skeleton and the oxidation pattern of ring B of the flavanones, are discussed.
Topics: Antineoplastic Agents, Phytogenic; Apoptosis; Drug Screening Assays, Antitumor; Fibroblasts; Flavanones; Fruit; Humans; Magnoliopsida; Molecular Structure; Morus; Nuclear Magnetic Resonance, Biomolecular; Plant Roots; Plants, Medicinal; Structure-Activity Relationship; Turkey
PubMed: 20192247
DOI: 10.1021/np900681y -
Cancer Research Oct 1991We have studied adduct formation of the antineoplastic agent diaziquone (AZQ; NSC 182986) with DNA and nucleotides in vitro. The aziridine moieties of AZQ can be...
We have studied adduct formation of the antineoplastic agent diaziquone (AZQ; NSC 182986) with DNA and nucleotides in vitro. The aziridine moieties of AZQ can be expected to interact covalently with DNA which, in turn, presumably elicits the antitumor activity. We analyzed AZQ-DNA adducts by a modified 32P-postlabeling assay involving purification of the nuclease P1-enriched labeled adducts by high-salt C18 reversed-phase thin-layer chromatography and separation of the eluted adducts on a polyethyleneimine-cellulose layer using non-urea salt solutions. Modification of calf thymus DNA with AZQ produced two major (22% and 40%) and at least eight minor adducts. At equal concentrations of AZQ and DNA (1 micrograms/microliters each), peak binding was observed in about 2 h [1926 +/- 378 (SD) fmol/micrograms of DNA] with the binding levels remaining practically unchanged through 4 h. However, incubation for 24 h resulted in over 40% decline, indicating adduct instability. AZQ was found to be highly reactive in vitro as evidenced by its substantial binding (49 +/- 14 fmol/micrograms of DNA) even at a DNA:AZQ ratio of 100:1. When incubated with mononucleotides, AZQ reacted extensively with adenine, guanine, and cytosine but only slightly with thymine. Cochromatography of the modified DNA and nucleotides revealed that one of the major adducts and several minor adducts were guanine derived. The aziridine rings of AZQ were found to be the main reactive sites as its monoaminoalcohol derivative showed as much DNA reactivity as did the parent compound, but no activity was observed when both aziridine groups were hydrolyzed to diaminoalcohols. The improved 32P-postlabeling assay seems capable of detecting relatively polar adducts such as those formed with AZQ at a level of one adduct/10(9) nucleotides.
Topics: Animals; Antineoplastic Agents; Aziridines; Benzoquinones; Cattle; Chromatography, Thin Layer; DNA; Dose-Response Relationship, Drug; In Vitro Techniques; Time Factors
PubMed: 1913643
DOI: No ID Found -
Journal of Neuro-oncology 1998
Review
Topics: Antineoplastic Agents; Aziridines; Benzoquinones; Brain Neoplasms; Cyclophosphamide; Cytotoxins; Humans; Injections, Spinal; Meningeal Neoplasms; Topotecan
PubMed: 9696375
DOI: 10.1023/a:1005944622003 -
Cancer Treatment Reports Mar 1987Diaziquone (AZQ) is a synthetic quinone with considerable activity against L1210 leukemia and potent myelosuppressive activity in man. To test the efficacy and toxicity... (Clinical Trial)
Clinical Trial
Diaziquone (AZQ) is a synthetic quinone with considerable activity against L1210 leukemia and potent myelosuppressive activity in man. To test the efficacy and toxicity of AZQ administered by continuous infusion, a phase II multi-institutional trial was undertaken by the Southeastern Cancer Study Group. Eligible adults with acute myeloid leukemia (AML) received AZQ at a dose of 28 mg/m2 daily by continuous infusion for 5 days. Patients failing to achieve complete remission received a second course utilizing the same dose and schedule. Of 25 evaluable patients with relapsed or refractory AML, three achieved complete response (12%) and two achieved partial response (8%). All patients experienced marked myelosuppression. Severe or life-threatening infection was observed in 15 (56%) patients. Clinical or postmortem evidence of central nervous system hemorrhage was encountered in three (12%) patients with severe refractory thrombocytopenia. Minimal nonhematologic toxicity was observed, suggesting that further studies of this agent in combination regimens and possibly for marrow transplantation preparation in patients with acute leukemia are warranted.
Topics: Adult; Aziridines; Azirines; Benzoquinones; Bone Marrow; Clinical Trials as Topic; Female; Humans; Leukemia, Myeloid, Acute; Male; Middle Aged
PubMed: 3545462
DOI: No ID Found -
Cancer Research Jan 1988Diaziquone (AZQ) (NSC 182986), a lipid-soluble benzoquinone derivative currently being tested as an experimental chemotherapeutic agent, was used to treat mouse and...
Diaziquone (AZQ) (NSC 182986), a lipid-soluble benzoquinone derivative currently being tested as an experimental chemotherapeutic agent, was used to treat mouse and human peripheral blood lymphocytes (PBLs) to determine its genotoxic potential by examination of sister chromatid exchange (SCE) induction. In vitro exposure to AZQ caused a linear increase in SCE in both mouse and human PBLs, with mouse PBLs being about twice as sensitive as the human cells. The lowest in vitro concentration found to induce a significant effect on SCE frequency was 0.3 micrograms/ml in mice and 1.0 micrograms/ml in human PBLs. Mice exposed by either i.p. or i.v. injection showed similar dose-related linear increases in SCE frequencies in their PBLs. After i.v. administration of AZQ, splenocytes from treated mice showed approximately the same SCE frequency as found in the PBLs. In general, AZQ caused a slowing of cell cycling in vivo while giving inconsistent responses in vitro. AZQ did cause a dose-related decrease in the number of recoverable mononuclear lymphocytes in mice treated in vivo. Contrary to the in vitro studies, comparison of SCE responses in mice with those previously observed in brain tumor patients undergoing chemotherapy with AZQ (Kligerman et al., Cancer Res., 47: 631-635, 1987) revealed AZQ was a much more potent SCE inducer in humans than in mice.
Topics: Animals; Antineoplastic Agents; Aziridines; Azirines; Benzoquinones; Cell Cycle; Cells, Cultured; DNA; Humans; Lymphocytes; Mice; Mice, Inbred C57BL; Sister Chromatid Exchange; Species Specificity
PubMed: 3334997
DOI: No ID Found -
Cancer Treatment Reports Dec 1985Diaziquone (AZQ) is a benzoquinone derivative exhibiting significant effects against CNS tumors. This study investigates the pharmacokinetics of AZQ for three different...
Diaziquone (AZQ) is a benzoquinone derivative exhibiting significant effects against CNS tumors. This study investigates the pharmacokinetics of AZQ for three different durations of continuous iv infusions, over 20 mins, 4 hrs, and 6 hrs, in nine patients with CNS malignancies. Total AZQ doses varied from 10 to 20 mg. The average elimination half-life was 37.2 +/- 13.9 mins, the total clearance was 515 +/- 280 ml/min or 11.3 +/- 5.9 ml/min/kg, and the apparent volume of distribution by area was 26.5 +/- 14.7 L or 0.62 +/- 0.50 L/kg. Peak concentrations after the 20-min infusions (three patients) varied from 0.58 to 1.20 micrograms/ml, whereas concentrations during the 4-hr infusions (three patients) varied from 0.02 to 0.37 micrograms/ml, and during the 6-hr infusions (three patients) varied from 0.02 to 0.61 micrograms/ml. These results indicate that concentrations found to exhibit minimum inhibitory effects in in vitro cell studies are achievable during prolonged iv infusions of AZQ.
Topics: Antineoplastic Agents; Aziridines; Azirines; Benzoquinones; Brain Neoplasms; Chromatography, High Pressure Liquid; Half-Life; Humans; Infusions, Parenteral; Kinetics; Metabolic Clearance Rate
PubMed: 4075314
DOI: No ID Found -
Drug Metabolism and Disposition: the... 1983We have studied the murine disposition and pharmacokinetics of diaziquone (AZQ), a new aziridinylbenzoquinone antitumor agent that is currently undergoing clinical...
We have studied the murine disposition and pharmacokinetics of diaziquone (AZQ), a new aziridinylbenzoquinone antitumor agent that is currently undergoing clinical trials. 14C-AZQ, dissolved in dimethylacetamide/0.01M phosphate buffer, pH 6.5, 5:95 (v/v), was administered iv to mice at a dosage of 6 mg/kg (18 mg/m2). After injection, mice were killed and plasma and organs were obtained and analyzed for total radioactivity and for chloroform-extractable 14C. Both total plasma radioactivity and chloroform-extractable plasma 14C declined very rapidly. By 3 hr, chloroform-extractable 14C was about 0.2% of its initial concentration. Within 30 min after injection, more radioactivity remained in the aqueous phase than was extracted into chloroform. When analyzed by TLC, all chloroform-extractable radioactivity in plasma as well as in brain, heart, liver, and skeletal muscle co-chromatographed with parent AZQ. Tissue distribution of 14C was extensive. 14C concentrations (dpm/g tissue wet weight) were initially greatest in heart and lung, but by 2 min after injection, were greatest in kidney, and by 10 min were second greatest in liver. Substantial amounts of total and chloroform-extractable 14C were found in brains. By 3 hr after injection, total 14C in all tissues exceeded total 14C in plasma. The apparent volume of distribution of AZQ was approximately 1 ml/g and the total body clearance of AZQ was 0.9 ml/min or 130 ml/min/m2. Extraction of tissues with chloroform showed conversion of AZQ into non-chloroform-extractable metabolites. This conversion was reproduced in vitro by mouse liver homogenate at 37 degrees C but not at 0 degree C.
Topics: Animals; Antineoplastic Agents; Aziridines; Azirines; Benzoquinones; Humans; Kinetics; Male; Mice; Mice, Inbred BALB C; Protein Binding; Tissue Distribution
PubMed: 6132794
DOI: No ID Found