New insights into carcinogenesis of the classical model arylamine 2-acetylaminofluorene

• Published in: Cancer letters 1999-09, Vol.143 (2), p.223-227
• Main Authors: Bitsch, Annette, Klöhn, Peter-Christian, Hadjiolov, Nikolai, Bergmann, Ole, Neumann, Hans-Günter
• Format: Article
• Language: English
• Subjects: 2-Acetylaminofluorene; 2-Acetylaminofluorene - administration & dosage; 2-Acetylaminofluorene - metabolism; 2-Acetylaminofluorene - toxicity; Animals; Apoptosis; arylamines; Biological and medical sciences; Carcinogenesis, carcinogens and anticarcinogens; Carcinogens - administration & dosage; Carcinogens - metabolism; Carcinogens - toxicity; Cell Division - drug effects; Cell Transformation, Neoplastic - drug effects; Chemical agents; Dose-Response Relationship, Drug; Initiation; Liver Neoplasms, Experimental - chemically induced; Liver Neoplasms, Experimental - metabolism; Liver Neoplasms, Experimental - pathology; Male; Medical sciences; Mitochondria, Liver - pathology; N-2-Fluorenylacetamide; Permeability transition pore; Promotion; Rat liver tumor; Rats; Rats, Wistar; Tumors
• ISSN: 0304-3835; 1872-7980
• DOI: 10.1016/S0304-3835(99)00129-9

2-Acetylaminofluorene (AAF) is a complete carcinogen in rat liver. The genotoxic effects of reactive metabolites are considered necessary but not sufficient to explain tumor formation. An overview is given of an AAF-feeding experiment designed to demonstrate early effects, preceding the development of enzyme-altered foci to support the hypothesis that toxic effects lead to a cirrhosis-like transformation as a prerequisite for the expansion of initiated foci and how those effects influence the dose-time-response relationship of tumor formation. Male Wistar rats were fed 0.005, 0.01, 0.02, 0.04 and 0.08% AAF in the diet for 2, 4, 8, and 16 weeks. GST-P-positive foci developed more than proportionately only at 16 weeks. As a first sign of morphological alterations the number of apoptoses increased (2 weeks), the proliferation rate followed with some delay and was maximal at 4 weeks. The most sensitive parameter for adaptive responses was the inhibition of the mitochondrial permeability transition, studied ex vivo. All parameters increased dose-dependently at low doses. A threshold could not be detected, but effects developed much more gradually with the lowest, non-toxic dose. The situation of massive development of foci observed with the higher doses at 16 weeks was not reached. Apoptosis and proliferation rate reach a plateau between 4 and 8 weeks with some of the doses indicating a period in which some balance between adaptation and stress response exists.