Abstract
Azonafide (2-[2′-(dimethylamino)ethyl]-1,2-dihydro-3H-dibenz[de, h]isoquinoline-1,3-dione) is the parent of a new series of anthracene-containing antitumor agents. Its structure is based on amonafide but lacks a primary amine and has an anthracene chromophore rather than a naphthalene chromophore. Using a rat liver cytosol incubation and HPLC/MS detection, we have identified four metabolites resulting from in vitro metabolism of azonafide. These alkyl-modified derivatives include a mono- and a di-N′-desmethyl metabolite, anN′-oxide metabolite, and a carboxylic acid metabolite. Purified samples of these metabolites were analyzed for cytotoxic activity using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium vital dye (mitochondrial reductase) assay and for inhibition of topoisomerase II (TOPO II) using a cell-free enzymatic system. Each metabolite had decreased cytotoxicity relative to azonafide with the following relative potencies in descending order: the mono-N′-desmethyl metabolite, di-N′-desmethyl metabolite, the N-oxide metabolite, and the carboxylic acid metabolite. Similarly, the N′-desmethyl metabolites retained TOPO II inhibitory activity but with lower potency than azonafide. The N-oxide and carboxylic acid metabolites did not inhibit TOPO II at 0.05 and 0.5 μg/ml, respectively. Thus, metabolism of azonafide by rat liver cytosol represents a detoxification pathway rather than a bioactivation scheme for this DNA intercalator.
Footnotes
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Send reprint requests to: Robert T. Dorr, The Arizona Cancer Center, P.O. Box 245024, 1515 N. Campbell Avenue, Tucson, AZ 85724.
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Supported by National Institute of Health and National Cancer Institute Grant GM 49875. Mass spectrometry was performed in the Southwest Environmental Health Sciences Center analytical core laboratory and supported by U.S. Public Health Service Grant ES 06994.
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A portion of this work was presented at the 88thannual meeting of the American Association for Cancer Research and appeared in abstract form in Proc Am Assoc Cancer Res38:226–227 (1997).
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↵2 Mayr CA, Sami SM, Remers WA and Dorr RT, unpublished data.
- Abbreviations used are::
- TOPO II
- topoisomerase II
- CHO
- Chinese hamster ovary
- DMSO
- dimethyl sulfoxide
- APCI
- atmospheric pressure chemical ionization
- MTT
- 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium
- Received July 22, 1997.
- Accepted October 22, 1997.
- The American Society for Pharmacology and Experimental Therapeutics
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