Free radical intermediates have been found in the metabolic pathways of a wide variety of organic compounds including antitumor agents which contain a quinone group. Drug activity as well as toxic effects appear to be the result of the purely chemical reactions that these free radicals can undergo. Our working hypothesis is that free radicals from quinone containing antitumor agents are implicated in the agent's activity. Before free radical metabolism can be implicated in a given agent's activity and/or toxicity, it is important that the chemistry of the free radical be known, and that the free radical be found in the metabolic pathway or generated by cells in culture. We plan to continue to investigate the relationship of drug free radicals to drug activity. We found that the free radical generated by electrochemical reduction of diaziquone (AZQ) is the same as that generated by cancer cells in culture. We were able to characterize the free radical in terms of electron spin resonance parameters, electrochemical reduction potentials and light spectroscopy. These results put us now in a position to study the chemical reactions of the AZQ free radical in the test tube and be able to make biologically significant statements regarding the free radical's behavior in vivo. For instance, we are going to look at chemical reactions of the free radicals of AZQ with nucleophiles of biological interest such as GSH and also with DNA. We want to relate their reaction rates to drug activity. We will also study the products of these reactions as possible metabolites. We and others have shown that for AZQ, borohydride reduction elicits DNA strand breaks which cannot be found in the absence of reducing conditions. We want to extend these experiments to in vitro and in vivo conditions where the effect of reduced AZQ against murine leukemia P388 will be investigated. We were able to show that AZQ can be activated by visible light (500 nm). We are now ready to study the photoenhancement of AZQ activity by visible light against cells in culture.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA033681-06
Application #
3171478
Study Section
Experimental Therapeutics Subcommittee 2 (ET)
Project Start
1983-07-01
Project End
1991-02-28
Budget Start
1989-03-01
Budget End
1991-02-28
Support Year
6
Fiscal Year
1989
Total Cost
Indirect Cost
Name
University of Maryland Baltimore
Department
Type
Schools of Medicine
DUNS #
003255213
City
Baltimore
State
MD
Country
United States
Zip Code
21201
Gutierrez, P L (2000) The metabolism of quinone-containing alkylating agents: free radical production and measurement. Front Biosci 5:D629-38
Fisher, G R; Donis, J; Gutierrez, P L (1992) Reductive metabolism of diaziquone (AZQ) in the S9 fraction of MCF-7 cells. II. Enhancement of the alkylating activity of AZQ by NAD(P)H: quinone-acceptor oxidoreductase (DT-diaphorase). Biochem Pharmacol 44:1625-35
Fisher, G R; Gutierrez, P L (1991) Free radical formation and DNA strand breakage during metabolism of diaziquone by NAD(P)H quinone-acceptor oxidoreductase (DT-diaphorase) and NADPH cytochrome c reductase. Free Radic Biol Med 11:597-607
Fisher, G R; Gutierrez, P L (1991) The reductive metabolism of diaziquone (AZQ) in the S9 fraction of MCF-7 cells: free radical formation and NAD(P)H: quinone-acceptor oxidoreductase (DT-diaphorase) activity. Free Radic Biol Med 10:359-70
Nguyen, B; Gutierrez, P L (1990) Mechanism(s) for the metabolism of mitoxantrone: electron spin resonance and electrochemical studies. Chem Biol Interact 74:139-62
Wilder, P J; Overman, D K; Tenenholz, T C et al. (1990) Differences in myristic acid synthesis and in metabolic rate for P388 cells resistant to doxorubicin. J Lipid Res 31:1973-82
Gutierrez, P L; Wilder, P J; Biswal, N (1989) In vitro multidrug resistance of P388 murine leukemia selected for resistance to diaziquone. Cancer Commun 1:181-90
Nguyen, B; Biswal, S; Gutierrez, P L (1988) The influence of diaziquone free radicals on the in vitro activity of diaziquone. Xenobiotica 18:593-602
Gutierrez, P L (1988) The influence of ascorbic acid on the free-radical metabolism of xenobiotics: the example of diaziquone. Drug Metab Rev 19:319-43
Gutierrez, P L; Balachandran Nayar, M S; Nardino, R et al. (1987) The chemical reduction of diaziquone: products and free radical intermediates. Chem Biol Interact 64:23-37

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