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2-Acetylaminofluorene mechanistic data and risk assessment: DNA reactivity, enhanced cell proliferation and tumor
L Verna1, J Whysner, G M Williams
1Toxicology and Risk Assessment Program, American Health Foundation, Valhalla, NY 10595-1599, USA.
Abstract:
The aromatic amine 2-acetylaminofluorene (AAF) produced neoplasms in diverse target organs of many animal species. AAF was DNA-reactive after N-hydroxylation by CYP1A2 in the liver and nitrenium ion formation at the target site. In mouse bladder, AAF-DNA adducts were proportional to dose. An epigenetic component for tumor formation was also present since tumor incidence and hyperplasia showed a threshold dose and decreased following discontinuation of AAF exposure. In contrast, both adduct and tumor formation in the liver were proportional to dose, and discontinuation of AAF did not reduce tumor incidence.
Insights
The aromatic amine 2-acetylaminofluorene (AAF) causes DNA damage and tumors in animals. Bladder tumor formation shows epigenetic factors and dose thresholds, unlike liver tumors.
Area of Science:
- Toxicology and Carcinogenesis
- Molecular Biology
- Epigenetics
Background:
- The aromatic amine 2-acetylaminofluorene (AAF) is a known carcinogen inducing neoplasms across various animal species and organs.
- AAF's carcinogenic mechanism involves metabolic activation via CYP1A2 in the liver, leading to DNA-reactive intermediates and subsequent DNA adduct formation at target sites.
Framework:
- Investigating the dose-response relationship and epigenetic contributions to AAF-induced carcinogenesis in mouse bladder and liver.
- Analyzing the impact of AAF exposure cessation on tumor incidence and hyperplasia in different target organs.
Implementation:
- Quantified AAF-DNA adducts in mouse bladder, demonstrating a dose-proportional relationship.
- Observed threshold effects for tumor incidence and hyperplasia in the bladder, suggesting an epigenetic component.
- Assessed liver tumor formation and adduct levels, finding them proportional to dose without reduction upon AAF discontinuation.
Implications:
- Highlights the distinct mechanisms of AAF carcinogenesis in the bladder versus the liver, with a significant epigenetic role in bladder tumor development.
- Suggests that epigenetic factors and threshold effects in the bladder may influence tumor initiation and progression differently than in the liver.
- Provides insights into organ-specific carcinogen responses and the potential for reversibility of chemically induced tumors.