Best evidence across studies

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Evidence-supported molecular sequence

1. Bioactivation: AFB1 itself is comparatively unreactive; hepatic CYP450 enzymes convert it to the electrophilic AFB1-8,9-epoxide (AFBO). Competing glutathione conjugation and aflatoxin-aldehyde-reductase pathways can reduce DNA binding. Bioactivation and detoxification pathways
2. Primary covalent lesion: AFBO attacks DNA, especially guanine, generating AFB1-N7-Gua. In Salmonella exposed to AFB1 with rat-liver S9 activation, approximately 70% of measured DNA-bound AFB1 co-eluted with AFB1-N7-Gua. Direct DNA-adduct identification
3. Lesion persistence and mutagenesis: AFB1-N7-Gua can be lost from DNA or undergo imidazole-ring opening to form AFB1-FAPy, a more persistent lesion discussed in the supplied review. Such lesions alter base-pairing and obstruct or misdirect DNA synthesis, linking adduct burden to mutation. In the bacterial model, 15 and 22 adducts per genome were associated with induced 8-azaguanine-resistance fractions of 4.9×10⁻⁴ and 9.6×10⁻⁴, respectively. Adduct burden and mutation relationship

From DNA damage to carcinogenic change

The supplied review connects AFB1 adduct formation with mutation patterns including a p53 codon-249 signature, while the rat study shows that persistent hepatic FAPy adducts remain detectable during exposure. In F344 rats, FAPy burden was reported as approximately one lesion per 250,000 nucleotides with AFB1 alone and one per 650,000 nucleotides with CDDO-Im, demonstrating that reduced carcinogenesis can occur despite residual adducts. Adduct persistence and cancer outcome

What is established versus uncertain

• Strongest causal chain: metabolic activation, covalent guanine adduction, and dose-associated mutagenesis.
• Contributory mechanism: ROS, lipid peroxidation, and inflammatory signaling may amplify cellular injury, but the supplied evidence is primarily review-level synthesis rather than a single definitive mechanistic experiment. Oxidative-stress contribution
• Important blind spots: the mutation estimate came from one Salmonella strain, one selectable marker, two doses, pooled cultures, and rat-liver S9; it did not directly measure mammalian replication or repair. Approximately 30% of bound AFB1 was unidentified in that experiment. Therefore, exact lesion-to-mutation efficiencies and human dose relationships remain uncertain.

Confidence: moderate-high for the bioactivation/adduct mechanism; moderate for the relative contribution of oxidative stress and for direct extrapolation from bacterial and rat models to humans.