Nongenotoxic carcinogens in the regulatory environment

Area of Science:

• Toxicology
• Carcinogenesis
• Risk Assessment

Background:

• Genotoxic mechanisms, involving direct DNA reactivity, are traditionally assumed for carcinogen testing and risk assessment.
• Carcinogenesis is a complex, multistep process where nongenotoxic mechanisms are increasingly recognized as primary drivers of tumor formation.
• Many nongenotoxic mechanisms exhibit high species-specificity, questioning the direct applicability of experimental rodent models to human health risks.

Purpose of the Study:

• To highlight the importance of nongenotoxic mechanisms in chemical carcinogenesis.
• To emphasize the limitations of genotoxicity-based risk assessment models for certain carcinogens.
• To advocate for research into the diverse mechanisms of nongenotoxic carcinogens for improved predictive assays and risk assessment.

Main Methods:

• Review of current understanding of carcinogenesis mechanisms.
• Analysis of the role of nongenotoxic pathways in experimental and human cancers.
• Discussion of the implications for risk assessment models and predictive assays.

Main Results:

• Nongenotoxic mechanisms are significant drivers of carcinogenesis, distinct from direct DNA damage.
• Species-specificity of nongenotoxic effects challenges the extrapolation of rodent data to humans.
• Current risk assessment models often overlook the impact of nongenotoxic carcinogens.

Conclusions:

• Further research is needed to elucidate the mechanisms of various classes of nongenotoxic carcinogens.
• Understanding these mechanisms will enable the development of more accurate predictive assays and realistic risk assessment strategies.
• For certain carcinogens, a no observed effect level with a safety factor may be the most appropriate risk management approach.