N-Hydroxy-2-fluorenylacetamide, an Active Intermediate of the Mammary Carcinogen N-Hydroxy-2-fluorenylbenzenesulfonamide1

The mechanism of mammary carcinogenesis by N-hydroxy-2-FBS, a highly potent mammary carcinogen for the female rat by ip administration, has been investigated. Previous work in vivoindicating hydrolytic cleavage of the nitrogen-sulfur bond has been confirmed with the use of sonicates of mammary gland. One of the products of the hydrolysis was N-hydroxy-2-FA identified by its conversion to 2-FA. Since carcinogenicity tests by local application showed that N-hydroxy-2-FA was not carcinogenic for the mammary gland, desulfonylation of N-hydroxy-2-FBS by mammary gland does not account for mammary carcinogenesis. N-Hydroxy-2-FBS applied directly to the mammary gland was not carcinogenic and 2-nitrosofluorene, the product of the spontaneous decomposition of N-hydroxy-2-FBS, exhibited only weak carcinogenicity upon local application. In contrast, N-hydroxy-2-FAA, a urinary metabolite of N-hydroxy-2-FBS, was highly carcinogenic by local application and very likely mediates the action of N-hydroxy-2-FBS. A metabolic pathway for the conversion of N-hydroxy-2-FBS to N-hydroxy-2-FAA is presented. This pathway involves the intermediate formation, by mammary gland or liver, of N-hydroxy-2-FA. The site of the subsequent acetylation of the hydroxylamine is unknown at present although the mammary gland appears to be excluded.The authors thank Dr. R. E. Rydell for histologic examination of tumors and Miss S. Cadman for technical assistance.