Mechanistic studies of the cytotoxic action of selected azonafide analogs

Persistent Link:
http://hdl.handle.net/10150/282529
Title:
Mechanistic studies of the cytotoxic action of selected azonafide analogs
Author:
Mayr, Craig, Andrew, 1968-
Issue Date:
1997
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The cytotoxic mechanism of selected anthracene-containing, DNA-intercalating antitumor agents (azonafides) was investigated. The hypothesis tested was that these compounds kill tumor cells via poisoning DNA topoisomerase II (TOPO II). This hypothesis was based on observations that similar DNA intercalators poison TOPO II as a contributing mechanism to their cytotoxicity. The agents studied had nuclear effects similar to other DNA intercalators. The azonafides inhibited DNA and RNA synthesis with lesser effects on protein synthesis. They produced DNA damage consistent with TOPO II poisoning, including single strand breaks, double strand breaks and DNA/protein crosslinks. Of the five analogs studied, the two with the greatest cytotoxic potency produced less DNA damage than the other analogs. Furthermore, the DNA damage produced by these two highly toxic analogs did not correlate with their cytotoxic potencies whereas the DNA damage production by the less toxic analogs did. This observation suggests that there may be disparate mechanisms of toxicity among the azonafides. All analogs studied inhibited the activity of purified TOPO II. However, there was no evidence of TOPO II poisoning in these experiments. Intracellular TOPO II poisoning assays revealed that only two of the five analogs poisoned TOPO II. This suggests that TOPO II poisoning is involved in the mechanism of action of some azonafide analogs. However, like other DNA intercalators, there may be alternate, possibly novel, mechanisms involved in their toxicity. Additional studies investigated the effect of metabolism on the activity of the parent compound (azonafide). Four metabolites resulting from in vitro metabolism of azonafide were identified including two desmethyl species, an N-oxide metabolite and a carboxylic acid metabolite. The two desmethyl species retained cytotoxic activity and inhibited TOPO II, but were less potent than the parent. The N-oxide and carboxylic acid metabolites were inactive in cytotoxicity analyses. These findings show that metabolism of azonafide represents a deactivation pathway and not a bioactivation scheme.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Biology, Molecular.; Health Sciences, Pharmacology.; Health Sciences, Oncology.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Pharmacology and Toxicology
Degree Grantor:
University of Arizona
Advisor:
Dorr, Robert T.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleMechanistic studies of the cytotoxic action of selected azonafide analogsen_US
dc.creatorMayr, Craig, Andrew, 1968-en_US
dc.contributor.authorMayr, Craig, Andrew, 1968-en_US
dc.date.issued1997en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe cytotoxic mechanism of selected anthracene-containing, DNA-intercalating antitumor agents (azonafides) was investigated. The hypothesis tested was that these compounds kill tumor cells via poisoning DNA topoisomerase II (TOPO II). This hypothesis was based on observations that similar DNA intercalators poison TOPO II as a contributing mechanism to their cytotoxicity. The agents studied had nuclear effects similar to other DNA intercalators. The azonafides inhibited DNA and RNA synthesis with lesser effects on protein synthesis. They produced DNA damage consistent with TOPO II poisoning, including single strand breaks, double strand breaks and DNA/protein crosslinks. Of the five analogs studied, the two with the greatest cytotoxic potency produced less DNA damage than the other analogs. Furthermore, the DNA damage produced by these two highly toxic analogs did not correlate with their cytotoxic potencies whereas the DNA damage production by the less toxic analogs did. This observation suggests that there may be disparate mechanisms of toxicity among the azonafides. All analogs studied inhibited the activity of purified TOPO II. However, there was no evidence of TOPO II poisoning in these experiments. Intracellular TOPO II poisoning assays revealed that only two of the five analogs poisoned TOPO II. This suggests that TOPO II poisoning is involved in the mechanism of action of some azonafide analogs. However, like other DNA intercalators, there may be alternate, possibly novel, mechanisms involved in their toxicity. Additional studies investigated the effect of metabolism on the activity of the parent compound (azonafide). Four metabolites resulting from in vitro metabolism of azonafide were identified including two desmethyl species, an N-oxide metabolite and a carboxylic acid metabolite. The two desmethyl species retained cytotoxic activity and inhibited TOPO II, but were less potent than the parent. The N-oxide and carboxylic acid metabolites were inactive in cytotoxicity analyses. These findings show that metabolism of azonafide represents a deactivation pathway and not a bioactivation scheme.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectBiology, Molecular.en_US
dc.subjectHealth Sciences, Pharmacology.en_US
dc.subjectHealth Sciences, Oncology.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplinePharmacology and Toxicologyen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorDorr, Robert T.en_US
dc.identifier.proquest9814421en_US
dc.identifier.bibrecord.b37743132en_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.