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Biochemical Pharmacology Apr 1992
Review
Topics: Animals; Antineoplastic Agents; Aziridines; Benzoquinones; Dihydrolipoamide Dehydrogenase; Drug Design; Enzyme Induction; Gene Expression Regulation, Enzymologic; Humans; Indolequinones; Indoles; Mitomycin; Neoplasms; Precancerous Conditions; Tirapazamine; Triazines
PubMed: 1575764
DOI: 10.1016/0006-2952(92)90694-e -
Biochemical Pharmacology Apr 1992The flavoenzyme thioredoxin reductase (TR) is an important enzyme for many aspects of cellular function. The antitumor quinones diaziquone and doxorubicin have been... (Comparative Study)
Comparative Study
Inhibition of cellular thioredoxin reductase by diaziquone and doxorubicin. Relationship to the inhibition of cell proliferation and decreased ribonucleotide reductase activity.
The flavoenzyme thioredoxin reductase (TR) is an important enzyme for many aspects of cellular function. The antitumor quinones diaziquone and doxorubicin have been shown to produce a time- and concentration-dependent inhibition of TR when incubated for up to 24 hr with intact A204 human rhabdomyosarcoma cells. There was a positive correlation between the inhibition of TR and the inhibition of cell colony formation measured 7 days later for diaziquone (r = 0.84, P less than 0.01), and for doxorubicin (r = 0.87, P less than 0.01). 2,6-Dichloroindophenol, which in previous studies was shown to be a good inhibitor of TR in vitro, was a poor inhibitor of TR in intact A204 cells and there was no significant correlation with inhibition of colony formation. The activity of ribonucleotide reductase, which catalyzes the first unique step of DNA synthesis and which obtains its reducing equivalents from TR through thioredoxin, was decreased in diaziquone- and doxorubicin treated A204 cells. We suggest that the inhibition of TR by some antitumor quinones leading to a decreased activity of TR and, consequently, a decreased activity of thioredoxin-dependent enzymes including ribonucleotide reductase may contribute to the growth inhibitory activity of these quinones.
Topics: Antineoplastic Agents; Aziridines; Benzoquinones; Cell Division; Dose-Response Relationship, Drug; Doxorubicin; Humans; Ribonucleotide Reductases; Thioredoxin-Disulfide Reductase; Tumor Cells, Cultured
PubMed: 1567483
DOI: No ID Found -
Biochemical Pharmacology Apr 1992Quinoids undergo metabolism by a number of flavoenzymes. Reactive species formed during the metabolism of some quinoids might be anticipated to inhibit flavoenzyme...
Quinoids undergo metabolism by a number of flavoenzymes. Reactive species formed during the metabolism of some quinoids might be anticipated to inhibit flavoenzyme activity. Several quinoids have been tested for their ability to inhibit rat liver thioredoxin reductase (TR). The antitumor quinones diaziquone and doxorubicin, and the quinoneimine 2,6-dichloroindophenol, were found to be inhibitors of the reduction of 5,5'-dithiobis-2-nitrobenzoic acid (DTNB) by TR. The inhibition was most marked after incubation of the quinoid with NADPH and the enzyme for 60 min before adding DTNB, with Ki values of 0.5 microM for diaziquone, 0.5 microM for doxorubicin, and 0.07 microM for 2,6-dichloroindophenol. The three quinoids all produced a time-dependent and first order loss of TR activity. There was formation of electron spin resonance-detectable semiquinoid free radicals upon incubation of diaziquone, doxorubicin and 2,6-dichloroindophenol with TR and NADPH under anaerobic conditions. Oxygen radicals formed by redox cycling of the quinoids did not make a major contribution to the inhibition of TR by the quinoids, as shown by the absence of significant reversal of the inhibition by anaerobic incubation conditions and the lack of effect of the oxygen radical scavengers dimethyl sulfoxide, superoxide dismutase and catalase. It was not possible to demonstrate NADPH-dependent covalent binding of radiolabeled diaziquone or doxorubicin to the TR apoprotein. It is possible that the quinoids bind noncovalently to the enzyme apoprotein, or bind to the FAD prosthetic group. The results of the study suggest that some antitumor quinoids are mechanism-based inhibitors of TR showing metabolism- and time-dependent irreversible inhibition of enzyme activity.
Topics: 2,6-Dichloroindophenol; Animals; Antineoplastic Agents; Aziridines; Benzoquinones; Dithionitrobenzoic Acid; Doxorubicin; Free Radical Scavengers; Free Radicals; Kinetics; Liver; Male; Quinones; Rats; Rats, Inbred Strains; Thioredoxin-Disulfide Reductase
PubMed: 1567482
DOI: 10.1016/0006-2952(92)90220-d -
Journal of Clinical Oncology : Official... Jan 1992Because there is a compelling need to develop new agents for intrathecal use, we investigated the safety, efficacy, and CSF pharmacokinetics of diaziquone (AZQ)... (Clinical Trial)
Clinical Trial
PURPOSE
Because there is a compelling need to develop new agents for intrathecal use, we investigated the safety, efficacy, and CSF pharmacokinetics of diaziquone (AZQ) following intrathecal administration in patients with refractory meningeal malignancies.
PATIENTS AND METHODS
Thirty-nine patients received 45 courses of intrathecal AZQ. Two schedules were studied; twice-weekly administration of a 1- or 2-mg dose and "concentration times time" (C x T) administration of 0.5 mg every 6 hours for three doses, administered once weekly.
RESULTS
Dose-limiting toxicity consisting of headache, nausea, or vomiting occurred in only three patients and only at the 2-mg, twice weekly dose. The schedules of 1 mg twice-weekly and 0.5 mg every 6 hours for three doses were well tolerated. Thirty-seven courses were assessable for response. The overall response rate was 62%. Complete responses (CRs) occurred in 14 of 37 courses (38%) and partial responses (PRs) occurred in nine of 37 courses (24%). Among patients with meningeal leukemia, CRs were observed in 11 of 26 courses (42%) and PRs in nine of 26 courses (35%). There was no difference in response rate related to dose or schedule. The pharmacokinetic behavior of intrathecally administered AZQ was characterized by biexponential disappearance from ventricular CSF, with mean half-lives of 18.2 and 78.6 minutes. The mean clearance rate was 0.37 mL/min.
CONCLUSION
Intrathecal AZQ is safe, well tolerated, and highly active against refractory meningeal malignancies.
Topics: Adolescent; Adult; Antineoplastic Agents; Aziridines; Benzoquinones; Child; Child, Preschool; Drug Administration Schedule; Drug Evaluation; Female; Humans; Injections, Spinal; Male; Meningeal Neoplasms; Precursor Cell Lymphoblastic Leukemia-Lymphoma
PubMed: 1727916
DOI: 10.1200/JCO.1992.10.1.143 -
International Journal of Radiation... 1992The flavoenzyme DT-diaphorase has the potential either to bioactivate or to detoxify different bioreductive cytotoxins. Elucidation of structural features governing the...
The flavoenzyme DT-diaphorase has the potential either to bioactivate or to detoxify different bioreductive cytotoxins. Elucidation of structural features governing the ability to act as a substrate for DT-diaphorase should facilitate rational optimization or elimination of this reductive pathway for a particular class of bioreductive drug. We have examined structure-activity relationships governing both the cytotoxicity and the DT-diaphorase mediated reduction of two groups of bioreductive alkylating agents: (1) Indoloquinones related to EO9 [3-hydroxy-methyl-5-aziridinyl-1-methyl-2-(1H-indole-4,7-dione)prop-beta - en-alpha-ol]; and (2) derivatives of diaziridinyl benzoquinone or diaziquone [2,5-bis(carboethoxyamino)-3,6-diaziridinyl-1,4-benzoquinone]. The rat U.K. 256 Walker tumor cell line and the human HT29 colon carcinoma line were studied because of their high DT-diaphorase content. Enzyme activity was measured spectrophotometrically by dicoumarol inhibitable cytochrome c reduction in the presence of drug, and aerobic cytotoxicity was assessed by the MTT assay. EO9 acted as a good substrate for both enzyme preparations and was highly potent in each cell line, especially in Walker tumor cells (ID50 0.039 nM). AZQ was also reduced efficiently and gave an ID50 of 6 nM in the Walker tumor line. Slight modifications in structure resulted in large variations in both DT-diaphorase metabolism and toxicity for both types of agent. There was a clear tendency for the most efficiently reduced analogues to exhibit greater cytotoxic potency. Inclusion of an aziridine moiety in the structure appears to be desirable, but not essential, for both rapid reduction and cytotoxicity. There was no evidence of active site-directed enzyme inhibition.
Topics: Animals; Antineoplastic Agents; Aziridines; Benzoquinones; Carcinoma 256, Walker; Cell Hypoxia; Colonic Neoplasms; Humans; In Vitro Techniques; Indoles; NAD(P)H Dehydrogenase (Quinone); Oxidation-Reduction; Prodrugs; Quinones; Rats; Structure-Activity Relationship; Tumor Cells, Cultured
PubMed: 1544832
DOI: 10.1016/0360-3016(92)90496-5 -
Biochemistry Dec 1991Several bifunctional alkylating agents of the aziridinylbenzoquinone class have been evaluated as potential antitumor agents. 3,6-Bis[(2-hydroxyethyl)amino]-2,5-...
Several bifunctional alkylating agents of the aziridinylbenzoquinone class have been evaluated as potential antitumor agents. 3,6-Bis[(2-hydroxyethyl)amino]-2,5- diaziridinyl-1,4-benzoquinone (BZQ), 2,5-diaziridinyl-1,4-benzoquinone (DZQ), 3,6-bis(carboxyamino)-2,5-diaziridinyl- 1,4-benzoquinone (AZQ), and six analogues of AZQ have been studied for their ability to induce DNA interstrand cross-linking, as measured by an agarose gel technique, and to determine whether they react with DNA in a sequence-selective manner, as determined by a modified DNA sequencing technique. At an equimolar concentration (10 microM), only DZQ and BZQ showed any detectable cross-linking at pH 7 without reduction. Cross-linking was enhanced in both cases at low pH (4). Reduction by ascorbic acid at both pH's increased the cross-linking, which was particularly striking in the case of DZQ. In contrast, AZQ and its analogues only produced a significant level of cross-linking under both low-pH and reducing conditions, the extent of cross-linking decreasing as the size of the alkyl end group increased. The compounds reacted with all guanine-N7 positions in DNA with a sequence selectivity similar to other chemotherapeutic alkylating agents, such as the nitrogen mustards, although some small differences were observed with BZQ. Nonreduced DZQ showed a qualitatively similar pattern of reactivity to the other compounds, but on reduction (at pH 4 or 7) was found to react almost exclusively with 5'-GC-3' sequences, and in particular, at 5'-TGC-3' sites. A model to explain this unique reaction is proposed.
Topics: Antineoplastic Agents; Autoradiography; Aziridines; Base Sequence; Benzoquinones; Cross-Linking Reagents; DNA; Electrophoresis, Agar Gel; Electrophoresis, Polyacrylamide Gel; Molecular Sequence Data; Oxidation-Reduction; Uracil Mustard
PubMed: 1751490
DOI: 10.1021/bi00114a016 -
British Journal of Cancer Dec 1991Surgical specimens from 15 medulloblastoma patients were used to establish early passage cultures. In vitro sensitivity to a battery of cytotoxic agents, including some...
Surgical specimens from 15 medulloblastoma patients were used to establish early passage cultures. In vitro sensitivity to a battery of cytotoxic agents, including some in current medulloblastoma treatment protocols, was measured. Drug sensitivity was assessed at clinically relevant drug concentrations using the 3H-thymidine uptake method. Tumours were predicted to be sensitive if greater than 37% were killed by exposure to drugs at clinically achievable levels. A poor response to vincristine (Vcr), cis-platin (CDDP), hydroxyurea (HU) or diaziquone (AZQ) (no responders), and cytosine arabinoside (AraC) (1/12), was seen. Nine of ten tumours tested were sensitive to mafosfamide (Mfs); seven out of 12 were sensitive to carmustine (BCNU), 12 of 13 to teniposide (VM-26) and seven of 13 to etoposide (VP16-213). VM-26 was the best of the agents tested with most tumours responding to very low concentrations of drug, suggesting that the role of epipodophyllotoxins in treatment of brain tumours be further investigated. Despite the marked sensitivity of the medulloblastomas to the epipodophyllotoxins, three early passage cultures were much more resistant to these drugs than the average for the group. The basis of this resistance was investigated. Deficient cellular uptake of drug was excluded as a cause of resistance. One resistant early passage culture displayed low cellular activity of topoisomerase II and decreased levels of drug induced enzyme-DNA strand break activity. This was not the case for the other resistant early passage cultures: the basis of resistance in these cells does not appear to be due to any previously reported mechanism.
Topics: Alkylating Agents; Amsacrine; Cell Division; Cell Survival; Cross-Linking Reagents; Cytarabine; DNA Damage; DNA Topoisomerases, Type II; Drug Resistance; Etoposide; Humans; Hydroxyurea; In Vitro Techniques; Karyotyping; Medulloblastoma; Teniposide; Tumor Cells, Cultured; Vincristine
PubMed: 1662532
DOI: 10.1038/bjc.1991.464 -
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 Clinical Oncology : Official... Aug 1991Diaziquone (AZQ), a synthetic quinone with demonstrated activity against acute nonlymphocytic leukemia (ANLL), primary CNS tumors, and non-Hodgkin's lymphoma (NHL), is... (Clinical Trial)
Clinical Trial
Diaziquone (AZQ), a synthetic quinone with demonstrated activity against acute nonlymphocytic leukemia (ANLL), primary CNS tumors, and non-Hodgkin's lymphoma (NHL), is virtually devoid of nonhematopoietic toxicity at conventional doses. As a prelude to its inclusion into bone marrow transplant (BMT) preparative regimens, a phase I study of high-dose AZQ with autologous BMT (ABMT) was performed. Patients with refractory solid tumors and lymphomas were treated with a single 24-hour infusion of AZQ at 50 to 355 mg/m2 in dose escalations of 20%. Fifty-six patients received 69 courses. Those receiving greater than 60 mg/m2 had nadir granulocyte and platelet counts less than 500/microL and 20,000/microL, respectively. Nausea, vomiting, stomatitis, and diarrhea were mild, transient, and not dose-related. Transient minimal elevations of liver function tests were seen in five patients and were also not dose-related. The maximally tolerated dose (MTD) of high-dose AZQ was found to be 245 mg/m2, with nephrotoxicity being dose-limiting. Significant azotemia was seen in four of 12 patients treated at 295 and 355 mg/m2, including fatal anuric renal failure in three of these patients. Reversible proteinuria also occurred in 24 of 26 courses above 150 mg/m2, including nephrotic range proteinuria in eight courses, all at doses of 205 to 355 mg/m2. The proteinuria was also associated with multiple proximal tubular defects including generalized aminoaciduria and proximal renal tubular acidosis. There were six early deaths including two of early renal failure (295 and 355 mg/m2), two of sepsis (205 and 245 mg/m2), one of a pulmonary embolus (85 mg/m2), and one of progressive disease (60 mg/m2). Of 50 patients who were assessable for response, there were seven responses including two of 10 with primary CNS tumors, one of 12 with malignant melanoma, one of five with non-small-cell lung carcinoma, two of two with breast carcinoma, and one of one with ovarian carcinoma. Because of its activity in ANLL and NHL and its unique toxicity spectrum, high-dose AZQ may improve the efficacy of current BMT preparative regimens without significantly increasing their nonhematopoietic toxicity.
Topics: Adolescent; Adult; Aged; Antineoplastic Agents; Aziridines; Benzoquinones; Bone Marrow Transplantation; Combined Modality Therapy; Dose-Response Relationship, Drug; Drug Evaluation; Female; Humans; Infusions, Intravenous; Kidney Diseases; Leukocyte Count; Male; Middle Aged; Neoplasms; Platelet Count
PubMed: 2072148
DOI: 10.1200/JCO.1991.9.8.1487 -
International Journal of Radiation... Jun 1991We have performed in vitro and in vivo tests to determine whether ultrasound (US) at levels lower than previously investigated by others could still potentiate...
We have performed in vitro and in vivo tests to determine whether ultrasound (US) at levels lower than previously investigated by others could still potentiate chemotherapeutic cell killing. Positive results were obtained with adriamycin and diaziquone. Two types of low-level US were effective: tone-burst US (10% duty cycle, 1.765 MHz, ISATA = 0.25 W/cm2), and pulsed US (2.5 MHz centre frequency, 1 kHz repetition frequency, MPa-level pressure amplitudes), distributed uniformly over the biological target. These US beams were non-cytotoxic and produced negligible temperature elevation. Statistically significant US-induced increases in drug cytotoxicity were observed in CHO and MCF-7 WT but not V79 cells for 1-h drug exposures at several drug concentrations. The effects of combined drug and US treatments in vivo were studied by measuring post-treatment volume changes in uterine cervical squamous cell carcinoma implanted in the cheek pouch of the Syrian hamster. A statistically significant US-drug synergy in tumour volume reduction was observed with adriamycin and diaziquone.
Topics: Animals; Antineoplastic Agents; Aziridines; Benzoquinones; Carcinoma, Squamous Cell; Cell Line; Cell Survival; Combined Modality Therapy; Cricetinae; Doxorubicin; Humans; In Vitro Techniques; Neoplasm Transplantation; Ultrasonic Therapy; Ultrasonics
PubMed: 1677389
DOI: 10.1080/09553009114551301