This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Coombs, M. M. Articles by Allen, J. A. Search for Related Content PubMed PubMed Citation Articles by Coombs, M. M. Articles by Allen, J. A.

An Investigation into the Binding of the Carcinogen 15,16-Dihydro-11-methylcyclopenta[a]phenanthren-17-one to DNA in Vitro

Chemistry Department, Imperial Cancer Research Fund Laboratories, Lincoln's Inn Fields, London WC2A 3PX, England

After metabolic activation the carcinogen 15,16-dihydro-11-[³H]methylcyclopenta[aphenanthren-17-one binds to DNA in vitro, and this binding is prevented by 7,8-benzoflavone. Radioactivity cannot be removed from the DNA with organic solvents or by chromatography on Sephadex G-50, even after heat denaturation of the DNA. Enzymatic hydrolysis yields radioactive fractions, which elute from a column of Sephadex LH-20 immediately after the natural nucleosides.

At least two species of reactive metabolites are involved in this binding, those with a half-life of a few hr and others with greater stability. After extraction from the aqueous incubation mixture, they could be detected in discrete polar fractions from separations of the complex metabolite mixture by high-pressure liquid chromatography. Their ability to bind to DNA decreased with time at ambient temperature, and they were rapidly deactivated by acid.

7,8-Benzoflavone acted by suppressing the formation of polar metabolites derived from enzymatic oxidation of the aromatic double bonds. The inhibitor had no effect on the enzymes hydroxylating saturated carbon; hence it is unlikely that metabolism of the methyl group is important in conversion of this carcinogen to its proximate form, although the presence of the 11-methyl group is essential for carcinogenic activity in this series.

Received 4/26/76. Accepted 8/17/76.