Structure-activity models of chemical carcinogens: state of the art, and new directions.

Chemical carcinogenicity has been the target of numerous attempts to create predictive models alternative to the animal ones, ranging from short-term biological assays (e.g. mutagenicity tests) to theoretical models. Among the theoretical models, the application of the science of structure-activity relationships (SAR) has earned special prominence. The qualitative approach to SAR has lead to the identification of a large number of reactive chemical substructures that are both mutagenic and carcinogenic. More sophisticated developments are the quantitative structure-activity relationship (QSAR) models, that link the physical chemical or structural properties of the molecules to the toxicological endpoints. Both approaches provide strong support to the process of risk assessment of the chemicals, especially in the phase of priority setting. Among the areas potentially able to contribute to further developments of (Q)SAR, the novel chemical relational databases are presented and discussed. The freely downloadable ISSCAN database on chemical carcinogens is presented.