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On Protein Binding of Fluorenyl Carcinogens by Minimal Deviation Hepatomas¹

Institute for Cancer Research, Philadelphia, Pennsylvania, and National Cancer Institute, Bethesda, Maryland

Because fluorenyl carcinogens form conjugates in preneoplastic liver that are principally soluble h₂ proteins and do not do so in subsequent liver tumor, the h proteins of 3 minimal deviation hepatomas have been studied. At the level of class detection, hepatoma 7787 has as much soluble h protein as has host liver. Hepatoma 5123 has less, and hepatoma 7793 has still less.

These transplanted minimal deviation hepatomas, which were originally induced by a fluorenyl carcinogen, were also tested for the ability to form fluorenyl conjugates among their h₂ proteins. Rats bearing these hepatomas were fed stock diet or N-2-fluorenylacetamide (FAA)² for 5 weeks. After they were given single i.p. injections of FAA-9-¹⁴C or its proximate N-hydroxy metabolite, N-OH-FAA-9-¹⁴C, the rats were sacrificed 48 hr later. Little or no h₂ fluorenyl-¹⁴C protein was found. Only the hepatoma 7787 of rats fed FAA had any significant amount of h₂ protein conjugate (8% that of equivalent liver). Instead, the principal protein conjugates in the extracts of these unperfused hepatomas were A proteins.

The present findings, taken together with the considerable number of previously accumulated correlations, are consistent with the concept that carcinogen conjugation forming h₂ protein conjugates may be involved in certain chemical carcinogeneses.

¹ This investigation was supported in part by Grant E-73 from the American Cancer Society and Grants CA 05945 and CA 06927 from the USPHS. The paper was presented in part at the 56th Annual Meeting of the American Association for Cancer Research, Philadelphia, Pennsylvania, April 7–10, 1965 (24).

² The following abbreviations are used: FAA, N-2-fluorenylacetamide (2-acetylaminofluorene); N-OH-FAA, N-hydroxy-N-2-fluorenylacetamide; TCA, trichloroacetic acid.

Received 6/11/65.