Salmonella mutagenicity and rodent carcinogenicity: quantitative structure-activity relationships

Area of Science:

• Toxicology
• Computational Chemistry
• Chemical Safety

Background:

• The NCI/NTP compiled 222 rodent carcinogenicity bioassays and Salmonella mutagenicity bioassays (Ames tests).
• Ashby and Tennant (1988) categorized compounds into genotoxic (Ames-positive) and non-genotoxic (Ames-negative) groups based on structural characteristics.
• The Ames test was identified as sufficient for genotoxicity identification, outperforming other short-term bioassays or batteries.

Purpose of the Study:

• To develop structure-activity relationship (SAR) models for predicting chemical carcinogenicity and genotoxicity.
• To classify carcinogens into genotoxic and non-genotoxic groups using SAR.
• To classify non-genotoxic compounds into carcinogenic and non-carcinogenic groups using SAR.

Main Methods:

• Utilized 222 NCI/NTP carcinogenicity bioassays and Ames tests.
• Developed QSAR models using molecular descriptors (sigma charge, connectivity indices, shape descriptors, substructure descriptors).
• Validated models for discriminating between genotoxic/non-genotoxic carcinogens and carcinogenic/non-carcinogenic non-genotoxins.

Main Results:

• Achieved 94.5% accuracy in distinguishing genotoxic from non-genotoxic carcinogens using an 8-descriptor equation.
• Achieved 95.2% accuracy in distinguishing carcinogenic from non-carcinogenic non-genotoxins using a 25-descriptor equation.
• Demonstrated high classification accuracy (approx. 95%) for both categories based solely on structural information.

Conclusions:

• Developed robust SAR models capable of predicting genotoxicity and carcinogenicity.
• These models enable classification of chemicals without requiring animal bioassay data.
• The findings support the use of SAR for chemical safety assessments and regulatory purposes.